Endocr Relat Cancer. 2006 Dec;13 Suppl 1:S77-88. Deciphering antihormone-induced compensatory mechanisms in breast cancer and their therapeutic implications.
Breast cancer inhibition by antihormones is rarely complete, and our studies using responsive models reveal the remarkable flexibility of breast cancer cells in recruiting alternative signalling to limit maximal anti-tumour effects of oestrogen receptor alpha (ER) blockade. The recruited mechanism involves antihormone-induced expression of oestrogen-repressed signalling genes. For example, epidermal growth factor receptor gene (EGFR) is induced by antioestrogens and maintains residual kinase and ER phosphorylation, cell survival genes, and thereby allows incomplete antihormone response and emergence of resistance. Microarrays are revealing the breadth of antihormone-induced genes that may attenuate growth inhibition, including NFkappaB, Bag1, 14-3-3zeta and tyrosine kinases, such as HER2 and Lyn. Three concepts are emerging: first, some genes are induced exclusively by antioestrogens, while others extend to oestrogen deprivation; secondly, some are transiently induced, while others persist into resistance; finally, some confer additional adverse features when tumour cells are in an appropriate context. Among the latter is CD59 whose antioestrogen induction may permit evasion of immune surveillance in vivo. Also, induction of pro-invasive genes (including NFkappaB, RhoE and delta-catenin) may underlie our findings that antioestrogens can markedly stimulate migratory behaviour when tumour intercellular contacts are compromised. Based on our promising studies selectively inhibiting EGFR (gefitinib), NFkappaB (parthenolide) or CD59 (neutralising antibody) together with antioestrogens, we propose that co-targeting strategies could markedly improve anti-tumour activity (notably enhancing cell kill) during the antihormone-responsive phase. Furthermore, subverting those induced signalling genes that are retained into resistance (e.g. EGFR, NFkappaB, HER2) may prove valuable in this state. Alongside future deciphering and targeting of genes underlying antioestrogen-promoted invasiveness, embracing of intelligent combination strategies could significantly extend patient survival.
PMID: 17259561 [PubMed - indexed for MEDLINE]Free Article
Breast Cancer Res. 2008;10(6):R103. Epub 2008 Dec 4. Anti-oestrogens but not oestrogen deprivation promote cellular invasion in intercellular adhesion-deficient breast cancer cells.
INTRODUCTION: Anti-oestrogens have been the mainstay of therapy in patients with oestrogen-receptor (ER) positive breast cancer and have provided significant improvements in survival. However, their benefits are limited by tumour recurrence in a significant proportion of initially drug-responsive breast cancer patients because of acquired anti-oestrogen resistance. Relapse on such therapies clinically presents as local and/or regional recurrences, frequently with distant metastases, and the prognosis for these patients is poor. The selective ER modulator, tamoxifen, classically exerts gene inhibitory effects during the drug-responsive phase in ER-positive breast cancer cells. Paradoxically, this drug is also able to induce the expression of genes, which in the appropriate cell context may contribute to an adverse cell phenotype. Here we have investigated the effects of tamoxifen and fulvestrant treatment on invasive signalling and compared this with the direct effects of oestrogen withdrawal to mimic the action of aromatase inhibitors. METHODS: The effect of oestrogen and 4-hydroxy-tamoxifen on the invasive capacity of endocrine-sensitive MCF-7 cells, in the presence or absence of functional E-cadherin, was determined by Matrigel invasion assays. Studies also monitored the impact of oestrogen withdrawal or treatment with fulvestrant on cell invasion. Western blotting using phospho-specific antibodies was performed to ascertain changes in invasive signalling in response to the two anti-oestrogens versus both oestradiol treatment and withdrawal. RESULTS: To the best of our knowledge, we report for the first time that tamoxifen can promote an invasive phenotype in ER-positive breast cancer cells under conditions of poor cell-cell contact and suggest a role for Src kinase and associated pro-invasive genes in this process. Our studies revealed that although this adverse effect is also apparent for further classes of anti-oestrogens, exemplified by the steroidal agent fulvestrant, it is absent during oestrogen withdrawal. CONCLUSIONS: These data highlight a previously unreported effect of tamoxifen (and potentially further anti-oestrogens), that such agents appear able to induce breast cancer cell invasion in a specific context (absence of good cell-cell contacts), where these findings may have major clinical implications for those patients with tumours that have inherently poor intercellular adhesion. In such patients oestrogen deprivation with aromatase inhibitors may be more appropriate.
PMID: 19055788 [PubMed - indexed for MEDLINE]PMCID: PMC2656899Free PMC Article
Matthew Ellis Siteman Cancer Center, Washington University, St. Louis, Missouri, USA
Correspondence: Matthew Ellis, M.D., Ph.D., F.R.C.P., Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8056, Division of Oncology, St. Louis, Missouri 63110, USA. Telephone: 314-362-8866; Fax: 314-362-7086; e-mail: mellis@im.wustl.edu
Endocrine therapy is the most effective systemic treatment forpatients with hormone-receptor-positive (HR+) breast cancer.Unfortunately, efficacy is often limited by the onset of resistance,which is almost inevitable for patients with advanced disease.Several patterns of endocrine resistance are recognizable clinically,including: A) tumors that are inherently insensitive to allattempts at estrogen receptor (ER) targeting despite expressionof ER (pan-endocrine therapy resistance); B) tumors that areestrogen dependent but resistant to one or more specific endocrinetherapies (agent-selective resistance); and C) tumors that initiallyrespond but subsequently progress (acquired resistance). Currentinsights into the molecular basis for these resistance patternsare rudimentary, but are most clearly illuminated by investigationsthat focus on the crosstalk between the ErbB or HER peptidegrowth factor family and the ER. The data are sufficiently compellingto be addressed by ongoing clinical trials that examine combinationsof endocrine agents and either trastuzumab (Herceptin®;Genentech, Inc.; South San Francisco, CA) or ErbB-specific tyrosinekinase (TK) inhibitors. Preliminary data from a small "proofof concept" phase II study of letrozole (Femara®; NovartisPharmaceuticals Corporation; East Hanover, NJ) and trastuzumabdemonstrated durable responses despite tamoxifen (Nolvadex®;AstraZeneca Pharmaceuticals; Wilmington, DE) resistance. Efficacywas variable, however, despite the selection of patients onthe basis of ER and ErbB-2 coexpression. Complicating mattersfurther, resistance often occurs in the absence of any evidencefor ErbB TK family member expression. In the absence of a cleartarget, common downstream signal transduction proteins thatare known to intersect with the ER pathway can be inhibitedto address resistance, including G proteins with farnesyltransferaseinhibitors and molecular target of rapamycin (mTOR) with rapamycinanalogues. With a number of phase III clinical trials now underway, major advances in the endocrine treatment of advanced diseaseare possible.
Breast Cancer Res Treat. 2010 Feb 5. [Epub ahead of print] Metformin and rapamycin have distinct effects on the AKT pathway and proliferation in breast cancer cells.
Zakikhani M, Blouin MJ, Piura E, Pollak MN.
Department of Oncology, McGill University, Montreal, QC, Canada.
Rapamycin and its analogues inhibit mTOR, which leads to decreased protein synthesis and decreased cancer cell proliferation in many experimental systems. Adenosine 5'- monophosphate-activated protein kinase (AMPK) activators such as metformin have similar actions, in keeping with the TSC2/1 pathway linking activation of AMPK to inhibition of mTOR. As mTOR inhibition by rapamycin is associated with attenuation of negative feedback to IRS-1, rapamycin is known to increase activation of AKT, which may reduce its anti-neoplastic activity. We observed that metformin exposure decreases AKT activation, an action opposite to that of rapamycin. We show that metformin (but not rapamycin) exposure leads to increased phosphorylation of IRS-1 at Ser(789), a site previously reported to inhibit downstream signaling and to be an AMPK substrate phosphorylated under conditions of cellular energy depletion. siRNA methods confirmed that reduction of AMPK levels attenuates both the IRS-1 Ser(789) phosphorylation and the inhibition of AKT activation associated with metformin exposure. Although both rapamycin and metformin inhibit mTOR (the former directly and the latter through AMPK signaling), our results demonstrate previously unrecognized differences between these agents. The data are consistent with the observation that maximal induction of apoptosis and inhibition of proliferation are greater for metformin than rapamycin.
PMID: 20135346
SABC 2009
67. Targeting Aldose Reductase: A Novel Strategy in Treating Endocrine Resistance Using Combination Therapy
Treating estrogen receptor-positive breast cancer tumors with a combination of fidarestat (an inhibitor of aldose reductase enzyme) and letrozole (an aromatase inhibitor) could delay or stop tumor resistance to endocrine therapy, according to data presented at the CTRC-AACR San Antonio Breast Cancer Symposium.
"Single agents are less effective," said Rajeshwar Rao Tekmal, Ph.D., professor of obstetrics and gynecology at the University of Texas Health Science Center at San Antonio. "Many tumors develop resistance, so this combination approach could prolong that window when endocrine therapy is effective."
About two-thirds of breast cancer tumors initially are hormone sensitive or estrogen receptor-positive and respond well to endocrine therapy. However, close to half of those tumors develop resistance to endocrine therapy, said Tekmal.
In this preclinical study, researchers treated estrogen receptor-positive tumors already resistant to letrozole with letrozole and fidarestat. As an inhibitor of aldose reductase enzyme, fidarestat blocks the metabolism of glucose in cancer cells. Together, the combination effectively re-sensitized the cells to letrozole, allowing for effective endocrine therapy and more cell death.
Researchers believe increased glucose metabolism (polyol accumulation) contributes to oxidative stress, which, in turn, could alter intracellular signalling by affecting the regulation of protein kinases that are known to be involved in therapy resistance. Blocking the path of glucose metabolism may help to restore sensitivity to endocrine therapies or it may stop or delay the development resistance endocrine therapies in first place.
While this is a preclinical study, Tekmal believes it could lead to future drug treatments that will make endocrine therapy more effective for longer periods of time.
"This is a very promising study showing that combination treatments seem to work on resistance and re-sensitizing tumors that are resistant to endocrine therapies," he said.
Listen to a recording of the teleconference:
Download* the mp3 of the teleconference (13.2 MB, 58 minutes and 04 seconds)
Does Glucose issue mean Metformin (also mTOR inhib) helpful?
http://www.patentstorm.us/patents/68...scription.html
Among the natural compounds, flavonoid compounds such as quercetin, quercetrin, naringinin and hesperidin are reported to be useful and potent aldose reductase inhibitors (Aida, K., Tawata, M., Shindo, H., Onaya, T., Sasaki H., Yamaguchi T., Chin, M., Mitsuhashi. Planta Med, 56 (1990) 254-258).
Vitamin C: an aldose reductase inhibitor that normalizes erythrocyte sorbitol in insulin-dependent diabetes mellitus
J. J. Cunningham, P. L. Mearkle and R. G. Brown
Department of Nutrition, University of Massachusetts, Amherst 01003-1420.
OBJECTIVE: Diabetic hyperglycemia promotes sorbitol production from glucose via aldose reductase. Since the intracellular accumulation of sorbitol, or its sequelae, are postulated to contribute to the progression of chronic diabetic complications, aldose reductase inhibitors (ARI) offer therapeutic promise. Others have shown that vitamin C at pharmacologic doses decreases erythrocyte (RBC) sorbitol. We examined whether smaller, physiologic doses of vitamin C were also effective in individuals with insulin-dependent diabetes mellitus (IDDM) and whether vitamin C was an ARI in vitro. METHODS: Vitamin C supplements (100 or 600 mg) were taken daily for 58 days by young adults with IDDM and nondiabetic adults in an otherwise free-living design. Diabetic control was monitored by fasting plasma glucose, glycosylated hemoglobin, and glycosuria and was moderate to poor throughout the study. RBC sorbitol was measured at baseline and again at 30 and 58 days. Three-day dietary records and 24-hour urine collections were performed for each sampling day. RESULTS: RBC sorbitol levels were significantly elevated in IDDMs, on average doubled, despite their more than adequate dietary intakes of vitamin C and normal plasma concentrations. Vitamin C supplementation at either dose normalized the RBC sorbitol in IDDMs within 30 days. This correction of sorbitol accumulation was independent of changes in diabetic control. Furthermore, our in vitro studies show that ascorbic acid inhibited aldose reductase activity. CONCLUSIONS: Vitamin C supplementation is effective in reducing sorbitol accumulation in the erythrocytes of diabetics. Given its tissue distribution and low toxicity, we suggest a superiority for vitamin C over pharmaceutic ARIs.
J. J. Cunningham Micronutrients as Nutriceutical Interventions in Diabetes Mellitus
J. Am. Coll. Nutr., February 1, 1998; 17(1): 7 - 10. [Abstract][Full Text][PDF]
By Julie Steenhuysen
CHICAGO, Dec 11 (Reuters) - U.S. researchers may have found a way to overcome resistance to hormone-blocking breast cancer drugs, extending the life of treatments that keep the disease in check.
They said the drug Nexavar or sorafenib, made by German drugmaker Bayer (BAYGn.DE) and its development partner Onyx Pharmaceuticals (ONXX.O), helped re-sensitize breast cancer to treatment with aromatase inhibitors, drugs given to post-menopausal women with hormone-sensitive breast cancers.
"Hormone-receptor positive breast cancers eventually become resistant to hormonal therapy," said Dr. Claudine Isaacs of Georgetown University in Washington, who presented her findings at the American Association for Cancer Research's San Antonio Breast Cancer Symposium.
"There has been a great deal of interest in trying to figure out how we might overcome that resistance or stop the cancer cells from figuring out how to circumvent that hormonal therapy," Isaacs said in a telephone interview.
She said Nexavar, a drug approved for liver and kidney cancer, acts on a lot of cancer-related genes and it also acts to inhibit new blood vessels from forming.
The researchers studied the drug in 35 post-menopausal women with advanced breast cancer resistant to treatment with aromatase inhibitors.
Women in the trial, funded with a grant by Bayer, continued to take the aromatase inhibitor, but they also took Nexavar.
"These women all had disease progression. Twenty-three percent of the women in the study had a clinical benefit from it. It means they either had shrinkage of their tumors or it stayed stable," Isaacs said.
Isaacs said the finding suggests the drug somehow circumvents the mechanism used by the cancer to resist the effects of the aromatase inhibitors. "It puts the brakes on it so it didn't grow for at least six months," she said.
The treatment was not without side effects. Many women in the study developed a rash called hand-foot syndrome, which causes redness, peeling and some tenderness on the palms of the hands and soles of the feet. It also caused elevated blood pressure in 11 percent of the women, but Isaacs this could be overcome by putting women on blood pressure drugs before taking Nexavar. She said the findings were strong enough to inspire the drug companies to start a large, late-stage study to see if it has a significant benefit for women.
Aromatase inhibitors include anastrozole, made by AstraZeneca (AZN.L) under the brand name Arimidex, and exemestane, made by Pfizer Inc (PFE.N), under the brand name Aromasin.
LINK Potential new therapy to re-sensitize breast cancer (Nexavar/Sorafenib)
Clin Cancer Res. 2010 Feb 23. [Epub ahead of print] Lapatinib Restores Hormone Sensitivity with Differential Effects on Estrogen Receptor Signaling in Cell Models of Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer with Acquired Endocrine Resistance.
Leary AF, Drury S, Detre S, Pancholi S, Lykkesfeldt AE, Martin LA, Dowsett M, Johnston SR.
Authors' Affiliations: Royal Marsden Hospital and Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London, United Kingdom; and Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
PURPOSE: Acquired endocrine resistance in estrogen receptor (ER)alpha+/human epidermal growth factor receptor 2-negative (HER2-) breast cancer has been associated with modest adaptive increases in HER2, although exactly how aberrant HER2 signaling affects the ERalpha pathway is poorly understood. We investigated (a) whether the epidermal growth factor receptor/HER2 inhibitor lapatinib could restore endocrine responsiveness in cell models of acquired endocrine resistance with modest increases in HER2, and (b) the nature of ERalpha-HER2 cross-talk in this process. Methods: Combination growth studies, ERalpha transcription, immunoblot, and gene expression assays were conducted in two models of acquired resistance to (a) estrogen deprivation (long-term estrogen-deprived cells) and (b) tamoxifen (long-term tamoxifen-treated cells), and in hormone sensitive controls. Changes in ERalpha, PgR, and HER2 were assessed in samples from patients treated with tamoxifen. RESULTS: Both cell models of acquired endocrine resistance showed modest adaptive upregulation in HER2, and lapatinib restored endocrine sensitivity in both. The effect of lapatinib on ERalpha signaling varied markedly depending on the nature of the HER2/ERalpha cross-talk. In long-term estrogen-deprived cells characterized by enhanced ERalpha function, lapatinib suppressed ERalpha genomic activity (as measured by pERSer118, ERalpha transcriptional activity, and PGR gene expression). In contrast, in long-term tamoxifen-treated cells with reduced ERalpha activation, lapatinib reactivated ERalpha genomic function. Twenty percent of tamoxifen-resistant patients relapsed with modest increases in HER2 and either suppressed or enhanced ERalpha/PgR expression. CONCLUSIONS: Aberrant GFR signaling can augment or suppress ERalpha function. Regardless, interrupting the HER2/ERalpha cross-talk with lapatinib can restore endocrine sensitivity and should be investigated as a therapeutic strategy in combination with endocrine therapy in ERalpha+/HER2- patients with acquired endocrine resistance. Clin Cancer Res; 16(5); 1486-97.
PMID: 20179226 [PubMed - as supplied by publisher]
Clin Cancer Res. 2010 Feb 23. [Epub ahead of print] Does Lapatinib Work against HER2-negative Breast Cancers?
Mayer IA, Arteaga CL.
Authors' Affiliations: Departments of Medicine, Cancer Biology, and Breast Cancer Research Program, Vanderbilt-Ingram Comprehensive Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee.
Aberrant growth factor receptor signaling can augment or suppress estrogen receptor (ER) function in hormone-dependent breast cancer cells and lead to escape from anti-estrogen therapy. Interruption of HER2/ER cross-talk with lapatinib can restore sensitivity to anti-estrogens and thus, should be investigated in combination with endocrine therapy in patients with ER+/HER2-negative breast cancers. Clin Cancer Res; 16(5); 1355-7.
PMID: 20179241 [PubMed - as supplied by publisher]
Low Forms of Cyclin E Reduce Breast Cancer Drug's Effectiveness
ScienceDaily (Feb. 9, 2010) — Overexpression of low-molecular-weight (LMW-E) forms of the protein cyclin E renders the aromatase inhibitor letrozole ineffective among women with estrogen-receptor-positive (ER+) breast cancers, researchers from The University of Texas M. D. Anderson Cancer Center report in Clinical Cancer Research.
The M. D. Anderson research, led by Khandan Keyomarsi, Ph.D., professor in M. D. Anderson's Department of Experimental Radiation Oncology and the Hubert L. and Olive Stringer Professor in Medical Oncology, found evidence that women whose cancers express the LMW-E are more likely to develop resistance to letrozole. However, their research also showed that treating breast cancer cells with a cyclin-dependent kinase 2 (CDK2) inhibitor can reverse letrozole resistance.
Cyclin E is one of the proteins that regulates the cell cycle, influencing how rapidly a cell passes through the four phases and divides. In tumor cells, cyclin E is converted to low-molecular weight forms, an event that does not occur in normal cells. High levels of LMW-E accelerate the cell's transition through the G1phase, an important checkpoint that can arrest the cell cycle if DNA damage is detected. Elevated levels of LMW-E have been linked to uncontrolled cell proliferation and a poor outcome in breast cancer patients. Outwitting Drug Resistance
Keyomarsi estimated that approximately 70 percent of all breast cancer patients are estrogen receptor positive (ER+), of which a large percentage are post-menopausal, and would thereby be a candidate to receive an aromatase inhibitor as maintenance therapy. Aromatase inhibitors can reduce the risk of early metastasis among postmenopausal women with ER+ breast cancer. However, not every patient responds to aromatase inhibitors, and those who do will develop resistance to the drugs over time, explained Keyomarsi. Understanding the mechanisms behind this resistance has been a long-standing goal in breast cancer research. The M. D. Anderson team hypothesized that ER+ breast cancer patients whose tumors express the LMW forms of cyclin E would be less responsive to treatment with an aromatase inhibitor. To test their hypothesis, the researchers exposed aromatase-overexpressing MCF-7/Ac1 breast cancer cells to the full-length form of cyclin E or to the LMW-E forms ("low forms").
"We found that we could negate the growth inhibitory effects of letrozole with the low forms of cyclin E but not with the wild-type cyclin E," said Keyomarsi, the study's senior author. "The mechanism behind this is that the low forms of cyclin E increase the activity of the cyclin E complex, and this complex is what mediates the negative effects."
After confirming that the LMW forms of cyclin E suppress the anti-proliferative effects of letrozole, the researchers examined whether a CDK2 inhibitor could reverse the drug resistance in the unresponsive breast cancer cells. "We challenged the aromatase-overexpressing cells with either the wild-type or the low forms of cyclin E and then treated them with the CDK2 inhibitor roscovitine," Keyomarsi said. "When we did that, we could kill all the cells." The researchers also looked back at the results of another ongoing study from their group in which 128 ER+ breast cancer patients were treated with an aromatase inhibitor. "Of those, 100 expressed normal levels of wild-type cyclin E, and 28 overexpressed the low forms," Keyomarsi said. "When we looked at recurrence, three of the hundred with wild-type cyclin E had experienced a recurrence compared to four of the twenty-eight with the low forms. That in itself tells us there is a huge difference between the two groups of patients based on the pattern of expression of normal versus low forms of cyclin E." Of the seven patients who had a recurrence, six had high levels of cyclin E activity. Keyomarsi noted that these patients can be treated with a CDK2 inhibitor, which is now clinically available.
"I believe that in the very near future we will be able to take advantage of the knowledge we now have about the low forms of cyclin E, and identify the patients who have these forms and devise a personalized treatment," Keyomarsi added.
This research was supported by National Institutes of Health grant CA87458 and National Cancer Institute grant P50CA116199, as well as funds from the Clayton Foundation.
Keyomarsi's co-authors on the all-M. D. Anderson study include: Said Akli, Ph.D., Tuyen Bui, Anna Biernacka, M.D. all of the Department of Experimental Radiation Oncology; Kelly K. Hunt, M.D.; and Hannah Wingate, Ph.D., Department of Surgical Oncology; Stacy Moulder, M.D., Department of Breast Medical Oncology; and Susan L. Tucker, Ph.D., Department of Bioinformatics and Computational Biology.
PLoS One. 2010 Jan 6;5(1):e8604. Co-inhibition of BCL-W and BCL2 restores antiestrogen sensitivity through BECN1 and promotes an autophagy-associated necrosis.
Crawford AC, Riggins RB, Shajahan AN, Zwart A, Clarke R.
Lombardi Comprehensive Cancer Center and Department of Oncology, School of Medicine, Georgetown University, Washington, District of Columbia, United States of America.
BCL2 family members affect cell fate decisions in breast cancer but the role of BCL-W (BCL2L2) is unknown. We now show the integrated roles of the antiapoptotic BCL-W and BCL2 in affecting responsiveness to the antiestrogen ICI 182,780 (ICI; Fulvestrant Faslodex), using both molecular (siRNA; shRNA) and pharmacologic (YC137) approaches in three breast cancer variants; MCF-7/LCC1 (ICI sensitive), MCF-7/LCC9 (ICI resistant), and LY2 (ICI resistant). YC137 inhibits BCL-W and BCL2 and restores ICI sensitivity in resistant cells. Co-inhibition of BCL-W and BCL2 is both necessary and sufficient to restore sensitivity to ICI, and explains mechanistically the action of YC137. These data implicate functional cooperation and/or redundancy in signaling between BCL-W and BCL2, and suggest that broad BCL2 family member inhibitors will have greater therapeutic value than targeting only individual proteins. Whereas ICI sensitive MCF-7/LCC1 cells undergo increased apoptosis in response to ICI following BCL-W+/-BCL2 co-inhibition, the consequent resensitization of resistant MCF-7/LCC9 and LY2 cells reflects increases in autophagy (LC3 cleavage; p62/SQSTM1 expression) and necrosis but not apoptosis or cell cycle arrest. Thus, de novo sensitive cells and resensitized resistant cells die through different mechanisms. Following BCL-W+BCL2 co-inhibition, suppression of functional autophagy by 3-methyladenine or BECN1 shRNA reduces ICI-induced necrosis but restores the ability of resistant cells to die through apoptosis. These data demonstrate the plasticity of cell fate mechanisms in breast cancer cells in the context of antiestrogen responsiveness. Restoration of ICI sensitivity in resistant cells appears to occur through an increase in autophagy-associated necrosis. BCL-W, BCL2, and BECN1 integrate important functions in determining antiestrogen responsiveness, and the presence of functional autophagy may influence the balance between apoptosis and necrosis.
PMID: 20062536 [PubMed - in process]
Breast Cancer Res Treat. 2009 Nov 27. [Epub ahead of print] ETAR antagonist ZD4054 exhibits additive effects with aromatase inhibitors and fulvestrant in breast cancer therapy, and improves in vivo efficacy of anastrozole.
Smollich M, Götte M, Fischgräbe J, Macedo LF, Brodie A, Chen S, Radke I, Kiesel L, Wülfing P.
Department of Obstetrics and Gynecology, University Hospital of Münster, Albert-Schweitzer-Str. 33, 48129, Munster, Germany.
Endothelin-1 (ET-1) and endothelin A receptor (ETAR) contribute to the development and progression of breast carcinomas by modulating cell proliferation, angiogenesis, and anti-apoptosis. We investigated antitumoral effects of the specific ETAR antagonist ZD4054 in breast cancer cells and xenografts, and assessed antitumoral efficacy of the combinations of ZD4054 with aromatase inhibitors and fulvestrant. Gene expression changes were assessed by quantitative real-time PCR. Cell proliferation was measured using alamarBlue((R)); migration and invasion assays were performed using modified Boyden chambers. Evaluating the antitumoral efficacy of ZD4054 in vivo, different breast cancer models were employed using nude mice xenografts. ZD4054 reduced ET-1 and ETAR expression in MCF-7, MDA-MB-231, and MDA-MB-468 breast cancer cells in a concentration-dependent manner. ZD4054 inhibited invasion by up to 37.1% (P = 0.022). Combinations of ZD4054 with either anastrozole or letrozole produced significant reductions in migration of aromatase-overexpressing MCF-7aro cells (P < 0.05). Combination of ZD4054 with fulvestrant reduced MCF-7 cell migration and invasion by 36.0% (P = 0.027) and 56.7% (P < 0.001), respectively, with effects significantly exceeding those seen with either compound alone. Regarding tumor volume reduction in vivo, ZD4054 (10 mg/kg) was equipotent to fulvestrant (200 mg/kg) and exhibited additive effects with anastrozole (0.5 mg/kg). These data are the first indicating that selective ETAR antagonism by ZD4054 displays antitumoral activity on breast cancer cells in vitro and in vivo. Our data strongly support a rationale for the clinical use of ZD4054 in combination with endocrine therapies.
PMID: 19943105 [PubMed - as supplied by publisher]
J Endocrinol. 2004 Nov;183(2):395-404. All trans-retinoic acid acts synergistically with hydroxytamoxifen and transforming-growth factor beta to stimulate apoptosis in MCF-7 breast cancer cells.
Danforth DN Jr.
Surgery Branch, National Cancer Institute, National Institutes of Health, Bldg. 10/Rm 2B42, Bethesda, Maryland 20892, USA. David_Danforth@nih.gov The anti-estrogen 4-hydroxytamoxifen (TAM) and vitamin A-related compounds, the retinoids, in combination act synergistically to inhibit growth of breast cancer cells in vitro and in vivo. To clarify the mechanism of this synergism, the effect of TAM and all trans-retinoic acid (AT) on proliferation of MCF-7 breast cancer cells was studied in vitro. TAM and AT acted synergistically to cause a time-dependent and dose-dependent inhibition of MCF-7 cell growth. In a temporally related manner, TAM+AT acted synergistically to downregulate Bcl-2 mRNA and Bcl-2 protein expression, and to stimulate apoptosis. TAM and AT each blocked cell cycle progression throughout 7 days of treatment but without any synergistic or additive effect on this process, indicating a selective synergism for apoptosis. The negative growth factor-transforming growth factor beta (TGFbeta) is secreted by these cells and was studied as a potential mediator of the synergistic effects of TAM+AT on apoptosis. TAM+AT acted synergistically to induce a fivefold increase in TGFbeta1 secretion over 72 h. TGFbeta1 alone had no apoptotic effects on these cells; however, TGFbeta1 in combination with AT acted synergistically to inhibit growth, to downregulate Bcl-2 mRNA and Bcl-2 protein expression, and to stimulate apoptosis of these cells in a manner comparable with that noted for TAM+AT. The synergism of both TAM+AT and TGFbeta1+AT for apoptosis was suppressed by estradiol. Co-incubation of TAM+AT with anti-TGFbeta antibody did not block down-regulation of Bcl-2 protein expression or stimulation of apoptosis. The synergistic effects of TAM+AT on apoptosis therefore occur independently of TGFbeta, although TGFbeta may interact with AT in a novel manner to provide another important anti-proliferative mechanism for breast cancer cells.
Valproic acid restores ERalpha and antiestrogen sensitivity to ERalpha-negative breast cancer cells.
Fortunati N, Bertino S, Costantino L, De Bortoli M, Compagnone A, Bandino A, Catalano MG, Boccuzzi G.
Oncological Endocrinology, AUO San Giovanni Battista, Torino, Italy. Histone deacetylase inhibitors (HDIs) are valuable drugs in breast cancer where estrogen receptor alpha (ERalpha) can be silenced by epigenetic modifications. We report the effect of the clinically available HDI, valproic acid (VPA), on ERalpha expression and function in ER-negative breast cancer cells, MDA-MB-231. VPA induced ERalpha mRNA and protein, while did not modify ERbeta. In VPA-treated cells, we also observed: (1) a correct transcriptional response to estradiol after transfection with the luciferase gene under the control of an estrogen-responsive minimal promoter (ERE-TKluc); (2) increased expression of the ER-related transcription factor FoxA1; (3) estradiol-induced up-regulation of several estrogen-regulated genes (e.g. pS2, progesterone receptor); (4) inhibitory effect of tamoxifen on cell growth. In conclusion, the HDI VPA, inducing ERalpha and FoxA1, confers to MDA-MB 231 cells an estrogen-sensitive "phenotype", restoring their sensitivity to antiestrogen therapy.
PMID: 19772891 [PubMed - as supplied by publisher
Cancer Res. 2010 Feb 23. [Epub ahead of print] FGFR1 Amplification Drives Endocrine Therapy Resistance and Is a Therapeutic Target in Breast Cancer.
Turner N, Pearson A, Sharpe R, Lambros M, Geyer F, Lopez-Garcia MA, Natrajan R, Marchio C, Iorns E, Mackay A, Gillett C, Grigoriadis A, Tutt A, Reis-Filho JS, Ashworth A.
Authors' Affiliations: The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research; Breast Unit, Royal Marsden Hospital; Breakthrough Breast Cancer Research Unit, King's College London School of Medicine, Guy's Hospital, London, United Kingdom. Amplification of fibroblast growth factor receptor 1 (FGFR1) occurs in approximately 10% of breast cancers and is associated with poor prognosis. However, it is uncertain whether overexpression of FGFR1 is causally linked to the poor prognosis of amplified cancers. Here, we show that FGFR1 overexpression is robustly associated with FGFR1 amplification in two independent series of breast cancers. Breast cancer cell lines with FGFR1 overexpression and amplification show enhanced ligand-dependent signaling, with increased activation of the mitogen-activated protein kinase and phosphoinositide 3-kinase-AKT signaling pathways in response to FGF2, but also show basal ligand-independent signaling, and are dependent on FGFR signaling for anchorage-independent growth. FGFR1-amplified cell lines show resistance to 4-hydroxytamoxifen, which is reversed by small interfering RNA silencing of FGFR1, suggesting that FGFR1 overexpression also promotes endocrine therapy resistance. FGFR1 signaling suppresses progesterone receptor (PR) expression in vitro, and likewise, amplified cancers are frequently PR negative, identifying a potential biomarker for FGFR1 activity. Furthermore, we show that amplified cancers have a high proliferative rate assessed by Ki67 staining and that FGFR1 amplification is found in 16% to 27% of luminal B-type breast cancers. Our data suggest that amplification and overexpression of FGFR1 may be a major contributor to poor prognosis in luminal-type breast cancers, driving anchorage-independent proliferation and endocrine therapy resistance. Cancer Res; 70(5); 2085-94.
PMID: 20179196 [PubMed - as supplied by publisher]
At a concentration of 1 μM, resveratrol significantly inhibited the VEGF-induced
PAE/VEGFR-2 endothelial cell migration (Fig. 1F). These data demonstrate that resveratrol inhibits both FGF- and VEGF-receptor-mediated endothelial cell growth and chemotaxis.
Introduction: Estrogen deprivation using aromatase inhibitors is one of the standard treatments for postmenopausal women with estrogen receptor (ER)-positive breast cancer. However, one of the consequences of prolonged estrogen suppression is acquired drug resistance. Our group is interested in studying antihormone resistance and has previously reported the development of an estrogen deprived human breast cancer cell line, MCF-7:5C, which undergoes apoptosis in the presence of estradiol. In contrast, another estrogen deprived cell line, MCF-7:2A, appears to have elevated levels of glutathione (GSH) and is resistant to estradiol-induced apoptosis. In the present study, we evaluated whether buthionine sulfoximine (BSO), a potent inhibitor of glutathione (GSH) synthesis, is capable of sensitizing antihormone resistant MCF-7:2A cells to estradiol-induced apoptosis. Methods Estrogen deprived MCF-7:2A cells were treated with 1 nM 17β-estradiol (E2), 100 µM BSO, or 1 nM E2 + 100 µM BSO combination in vitro, and the effects of these agents on cell growth and apoptosis were evaluated by DNA quantitation assay and annexin V and terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) staining. The in vitro results of the MCF-7:2A cell line were further confirmed in vivo in a mouse xenograft model. Results:Exposure of MCF-7:2A cells to 1 nM E2 plus 100 µM BSO combination for 48 to 96 h produced a sevenfold increase in apoptosis whereas the individual treatments had no significant effect on growth. Induction of apoptosis by the combination treatment of E2 plus BSO was evidenced by changes in Bcl-2 and Bax expression. The combination treatment also markedly increased phosphorylated c-Jun N-terminal kinase (JNK) levels in MCF-7:2A cells and blockade of the JNK pathway attenuated the apoptotic effect of E2 plus BSO. Our in vitro findings corroborated in vivo data from a mouse xenograft model in which daily administration of BSO either as a single agent or in combination with E2 significantly reduced tumor growth of MCF-7:2A cells. Conclusions:Our data indicates that GSH participates in retarding apoptosis in antihormone-resistant human breast cancer cells and that depletion of this molecule by BSO may be critical in predisposing resistant cells to E2-induced apoptotic cell death. We suggest that these data may form the basis of improving therapeutic strategies for the treatment of antihormone resistant ER-positive breast cancer.
Bisphosphonates suppress insulin-like growth factor 1-induced angiogenesis via the HIF-1α/VEGF signaling pathways in human breast cancer cells
International Journal of Cancer, 08/12/09
Tang X et al. - In a trial to investigate potential molecular mechanisms underlying the antiangiogenic effect of non-nitrogen-containing and nitrogen-containing bisphosphonates, clodronate and pamidronate, respectively, in insulin-like growth factor (IGF)-1 responsive human breast cancer cells, it was demonstrated that pamidronate and clodronate functionally abrogated both in vitro and in vivo tumor angiogenesis induced by IGF-1-stimulated MCF-7 cells. These findings have highlighted an important mechanism of the pharmacological action of bisphosphonates in inhibition of tumor angiogenesis in breast cancer cells.
Methods
It was tested whether bisphosphonates had any effects on hypoxia-inducible factor (HIF)-1α/vascular endothelial growth factor (VEGF) axis that plays a pivotal role in tumor angiogenesis.
Results
Both pamidronate and clodronate significantly suppressed IGF-1-induced HIF-1α protein accumulation and VEGF expression in MCF-7 cells.
Mechanistically, either pamidronate or clodronate did not affect mRNA expression of HIF-1α, but they apparently promoted the degradation of IGF-1-induced HIF-1α protein.
The presence of pamidronate and clodronate led to a dose-dependent decease in the newly-synthesized HIF-1α protein induced by IGF-1 in breast cancer cells after proteasomal inhibition, thus, indirectly reflecting inhibition of protein synthesis.
The inhibitory effects of bisphosphonates on the HIF-1α/VEGF axis are associated with inhibition of the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin signaling pathways.
Stopping Treatment Can Reverse Acquired Resistance to Letrozole
Gauri J. Sabnis1, Luciana F. Macedo1, Olga Goloubeva2, Adam Schayowitz1 and Angela M.H. Brodie1,2 1 Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine and 2 University of Maryland Greenebaum Cancer Center, Baltimore, Maryland Requests for reprints: Angela M.H. Brodie, Department of Pharmacology and Experimental Therapeutics, University of Maryland, School of Medicine, Health Science Facility I, Room 580G, 685 West Baltimore Street, Baltimore, MD 21201. Phone: 410-706-3137; Fax: 410-706-0032; E-mail: abrodie@umaryland.edu .
Using the intratumoral aromatase xenograft model, we have observedthat despite long-lasting growth inhibition, tumors eventuallybegin to grow during continued letrozole treatment. In cellsisolated from these long-term letrozole-treated tumors (LTLT-Ca),estrogen receptor- (ER) levels were decreased, whereas signalingproteins in the mitogen-activated protein kinase cascade wereup-regulated along with human epidermal growth factor receptor2 (Her-2). In the current study, we evaluated the effect ofdiscontinuing letrozole treatment on the growth of letrozole-resistantcells and tumors. The cells formed tumors equally well in theabsence or presence of letrozole and had similar growth rates.After treatment was discontinued for 6 weeks, letrozole wasadministered again. Marked tumor regression was observed withthis second course of letrozole treatment. Similarly, in MCF-7Caxenografts, a 6-week break in letrozole treatment prolongedthe responsiveness of the tumors to letrozole. To understandthe mechanisms of this effect, LTLT-Ca cells were cultured inthe absence of letrozole for 16 weeks. The resulting cell line(RLT-Ca) exhibited properties similar to MCF-7Ca cells. Thecell growth was inhibited by letrozole and stimulated by estradiol.The expression of phosphorylated mitogen-activated protein kinase(MAPK) was reduced and ER and aromatase levels increased comparedwith LTLT-Ca cells and were similar to levels in MCF-7Ca cells.These results indicate that discontinuing treatment can reverseletrozole resistance. This could be a beneficial strategy toprolong responsiveness to aromatase inhibitors for patientswith breast cancer. [Cancer Res 2008;68(12):4518–24]
FASEB J. 2010 Feb 12. [Epub ahead of print] BCL2 and CASP8 regulation by NF-{kappa}B differentially affect mitochondrial function and cell fate in antiestrogen-sensitive and -resistant breast cancer cells.
Nehra R, Riggins RB, Shajahan AN, Zwart A, Crawford AC, Clarke R.
*Department of Oncology,Lombardi Comprehensive Cancer Center, andDepartment of Physiology and Biophysics, Georgetown University School of Medicine, Washington, DC, USA.
Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-alpha (ER)-positive breast cancer. We show that inhibition of NF-kappaB (p65/RELA), either by overexpression of a mutant IkappaB (IkappaBSR) or a small-molecule inhibitor of NF-kappaB (parthenolide; IC50=500 nM in tamoxifen-resistant cells), synergistically restores sensitivity to 4-hydroxytamoxifen (4HT) in resistant MCF7/RR and MCF7/LCC9 cells and further sensitizes MCF-7 and MCF7/LCC1 control cells to 4HT. These effects are independent of changes in either cell cycle distribution or in the level of autophagy measured by inhibition of p62/SQSTM1 expression and cleavage of LC3. NF-kappaB inhibition restores the ability of 4HT to decrease BCL2 expression, increase mitochondrial membrane permeability, and induce a caspase-dependent apoptotic cell death in resistant cells. Each of these effects is reversed by a caspase 8 (CASP8)-specific inhibitor that blocks enzyme-substrate binding. Thus, increased activation of NF-kappaB can alter sensitivity to tamoxifen by modulating CASP8 activity, with consequent effects on BCL2 expression, mitochondrial function, and apoptosis. These data provide significant new insights into how molecular signaling affects antiestrogen responsiveness and strongly suggest that a combination of parthenolide and tamoxifen may offer a novel therapeutic approach to the management of some ER-positive breast cancers.-Nehra, R., Riggins, R. B., Shajahan, A. N., Zwart, A., Crawford, A. C., Clarke, R. BCL2 and CASP8 regulation by NF-kappaB differentially affect mitochondrial function and cell fate in antiestrogen-sensitive and -resistant breast cancer cells.
PMID: 20154269 [PubMed - as supplied by publisher]
Mol Cancer Ther. 2008 Jul;7(7):2096-108. Apigenin inhibits antiestrogen-resistant breast cancer cell growth through estrogen receptor-alpha-dependent and estrogen receptor-alpha-independent mechanisms.
Long X, Fan M, Bigsby RM, Nephew KP.
Medical Sciences, Indiana University School of Medicine, 302 Jordan Hall, 1001 East 3rd Street, Bloomington, IN 47405-4401, USA. Breast cancer resistance to the antiestrogens tamoxifen (OHT) and fulvestrant is accompanied by alterations in both estrogen-dependent and estrogen-independent signaling pathways. Consequently, effective inhibition of both pathways may be necessary to block proliferation of antiestrogen-resistant breast cancer cells. In this study, we examined the effects of apigenin, a dietary plant flavonoid with potential anticancer properties, on estrogen-responsive, antiestrogen-sensitive MCF7 breast cancer cells and two MCF7 sublines with acquired resistance to either OHT or fulvestrant. We found that apigenin can function as both an estrogen and an antiestrogen in a dose-dependent manner. At low concentrations (1 mumol/L), apigenin stimulated MCF7 cell growth but had no effect on the antiestrogen-resistant MCF7 sublines. In contrast, at high concentrations (>10 mumol/L), the drug inhibited growth of MCF7 cells and the antiestrogen-resistant sublines, and the combination of apigenin with either OHT or fulvestrant showed synergistic, growth-inhibitory effects on both antiestrogen-sensitive and antiestrogen-resistant breast cancer cells. To further elucidate the molecular mechanism of apigenin as either an estrogen or an antiestrogen, effects of the drug on estrogen receptor-alpha (ERalpha); transactivation activity, mobility, stability, and ERalpha-coactivator interactions were investigated. Low-dose apigenin enhanced receptor transcriptional activity by promoting interaction between ERalpha and its coactivator amplified in breast cancer-1. However, higher doses (>10 mumol/L) of apigenin inhibited ERalpha mobility (as determined by fluorescence recovery after photobleaching assays), down-regulated ERalpha and amplified in breast cancer-1 expression levels, and inhibited multiple protein kinases, including p38, protein kinase A, mitogen-activated protein kinase, and AKT. Collectively, these results show that apigenin can function as both an antiestrogen and a protein kinase inhibitor with activity against breast cancer cells with acquired resistance to OHT or fulvestrant. We conclude that apigenin, through its ability to target both ERalpha-dependent and ERalpha-independent pathways, holds promise as a new therapeutic agent against antiestrogen-resistant breast cancer.
PMID: 18645020 [PubMed - indexed for MEDLINE]
Clin Ther. 2009;31P2:2371-2378. High-dose estrogen as salvage hormonal therapy for highly refractory metastatic breast cancer: A retrospective chart review.
Mahtani RL, Stein A, Vogel CL.
Boca Raton Comprehensive Cancer Center, Boca Raton, Florida.
Background: High-dose estrogens (HDEs) are an efficacious but widely overlooked treatment option for patients with metastatic breast cancer (MBC). This is due in part to the introduction of tamoxifen in the 1970s, which was proven to be equivalent in efficacy and associated with fewer adverse events (AEs). Objective: The aim of this study was to report our experience with the use of HDE in postmenopausal women with advanced breast cancer. Methods: Local institutional review board approval was obtained to conduct a retrospective chart review of patients with MBC treated with HDEs at the Boca Raton Comprehensive Cancer Center, Boca Raton, Florida, from 2001 through March 2009. Demographic information, response rates, and tolerability profiles were collected. Results: Of the 426 patients with MBC identified, we found 26 patients with MBC who were prescribed HDEs as a treatment in any line of therapy for advanced breast cancer. The median age at the start of HDE therapy was 59 years (range, 42-92 years). Three of the 26 patients (11.5%) were human epidermal growth factor receptor 2-positive determined via fluorescent in situ hybridization analysis. With the exception of 1 patient who had received no prior systemic treatment for metastatic disease, all patients received multiple lines of treatment (both chemotherapy and hormonal treatments) in the advanced setting (median, 7 lines; range, 0-12) prior to the initiation of HDE. Five of 20 patients (25%) with measurable metastatic disease (visceral and/or soft tissue metastases) had objective antitumor responses defined as either a partial response (PR) or a complete response (CR). Four additional patients (20%) had prolonged stable disease (SD) for >/=6 months. Three of 6 patients (50%) with nonmeasurable metastatic disease (bone-only) had prolonged SD for >/=6 months. Clinical benefit rate (defined as CR + PR + SD >/=6 months) for all patients was 46% (12/26), with a median duration of 10 months. Overall median progression-free survival for the 26 subjects was 5 months. Median survival from the start of HDE was 17 months (range, 3-54 months). AEs included fluid retention (8 [31%]), vaginal bleeding (7 [27%]), and nausea (4 [15%]). Two patients discontinued therapy after 1 month. Three of the remaining 24 patients discontinued estrogen therapy due to AEs.
PMID: 20110046 [PubMed - as supplied by publisher]
JAMA. 2009 Aug 19;302(7):774-80. Lower-dose vs high-dose oral estradiol therapy of hormone receptor-positive, aromatase inhibitor-resistant advanced breast cancer: a phase 2 randomized study.
CONTEXT: Estrogen deprivation therapy with aromatase inhibitors has been hypothesized to paradoxically sensitize hormone-receptor-positive breast cancer tumor cells to low-dose estradiol therapy. OBJECTIVE: To determine whether 6 mg of estradiol (daily) is a viable therapy for postmenopausal women with advanced aromatase inhibitor-resistant hormone receptor-positive breast cancer. DESIGN, SETTING, AND PATIENTS: A phase 2 randomized trial of 6 mg vs 30 mg of oral estradiol used daily (April 2004-February 2008 [enrollment closed]). Eligible patients (66 randomized) had metastatic breast cancer treated with an aromatase inhibitor with progression-free survival (> or = 24 wk) or relapse (after > or = 2 y) of adjuvant aromatase inhibitor use. Patients at high risk of estradiol-related adverse events were excluded. Patients were examined after 1 and 2 weeks for clinical and laboratory toxicities and flare reactions and thereafter every 4 weeks. Tumor radiological assessment occurred every 12 weeks. At least 1 measurable lesion or 4 measurable lesions (bone-only disease) were evaluated for tumor response. INTERVENTION: Randomization to receive 1 oral 2-mg generic estradiol tablet 3 times daily or five 2-mg tablets 3 times daily. MAIN OUTCOME MEASURES: Primary end point: clinical benefit rate (response plus stable disease at 24 weeks). Secondary outcomes: toxicity, progression-free survival, time to treatment failure, quality of life, and the predictive properties of the metabolic flare reaction detected by positron emission tomography/computed tomography with fluorodeoxyglucose F 18. RESULTS: The adverse event rate (> or = grade 3) in the 30-mg group (11/32 [34%]; 95% confidence interval [CI], 23%-47%) was higher than in the 6-mg group (4/34 [18%]; 95% CI, 5%-22%; P = .03). Clinical benefit rates were 9 of 32 (28%; 95% CI, 18%-41%) in the 30-mg group and 10 of 34 (29%; 95% CI, 19%-42%) in the 6-mg group. An estradiol-stimulated increase in fluorodeoxyglucose F 18 uptake (> or = 12% prospectively defined) was predictive of response (positive predictive value, 80%; 95% CI, 61%-92%). Seven patients with estradiol-sensitive disease were re-treated with aromatase inhibitors at estradiol progression, among which 2 had partial response and 1 had stable disease, suggesting resensitization to estrogen deprivation. CONCLUSIONS: In women with advanced breast cancer and acquired resistance to aromatase inhibitors, a daily dose of 6 mg of estradiol provided a similar clinical benefit rate as 30 mg, with fewer serious adverse events. The efficacy of treatment with the lower dose should be further examined in phase 3 clinical trials. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00324259.
PMID: 19690310 [PubMed - indexed for MEDLINE]
J Mammary Gland Biol Neoplasia. 2010 Jan 27. [Epub ahead of print] Epigenetic Regulation in Estrogen Receptor Positive Breast Cancer-Role in Treatment Response.
Pathiraja TN, Stearns V, Oesterreich S.
Translational Biology and Molecular Medicine Graduate Program, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX, USA.
Recent advances in breast cancer treatment have allowed increasing numbers of patients with estrogen receptor (ER) positive (+) breast cancer to receive various forms of endocrine therapy. Unfortunately, de novo and acquired resistance to endocrine therapy remains a major challenge in the clinic. A number of possible mechanisms for drug resistance have been described, which include activation of growth factor receptor pathways, overexpression of ER coactivators, and metabolic resistance due to polymorphisms in metabolizing enzymes. While many of these changes are caused by genetic alterations, there is also increasing evidence to implicate epigenetic gene regulatory mechanisms in the development of endocrine resistance. Since epigenetic modifications are easier to reverse than genetic mutations, they are appealing therapeutic targets, and thus future improvements in medical care for breast cancer patients will depend upon a better understanding of the roles epigenetic modifications play in endocrine resistance. In this review we will focus on recent advances made in the understanding of epigenetic gene regulation in estrogen response and endocrine resistance in breast cancer. We will also summarize current clinical-translational advances in epigenetic therapy, and discuss potential future clinical use of epigenetic changes as therapeutic targets, especially with respect to endocrine treatment.
PMID: 20101445 [PubMed - as supplied by publisher]
Int J Cancer. 2010 Jan 15;126(2):545-62. Endocrine resistance associated with activated ErbB system in breast cancer cells is reversed by inhibiting MAPK or PI3K/Akt signaling pathways.
Herbal complex suppresses telomerase activity in chemo-endocrine resistant cancer cell lines.
Lian Z, Fujimoto J, Yokoyama Y, Niwa K, Tamaya T.
Department of Obstetrics and Gynecology, Gifu University School of Medicine, Gifu City, Japan.
A herbal complex consisting of Hoelen, Angelicae radix, Scutellariae radix and Glycyrrhizae radix suppressed cell viability and telomerase activity in hormone-refractory and chemo-resistant cancer cell lines, namely poorly differentiated uterine endometrial cancer cell line AN3 CA, adriamycin-resistant breast cancer cell line MCF7/ADR and cisplatin-resistant ovarian cancer cell line A2780. Furthermore, the herbal complex suppressed the expression of the full length of human telomerase reverse transcriptase (hTERT), which is related to telomerase activity. This indicates that the herbal complex can suppress the tumor growth of chemoendocrine resistant cancers, at least in part via suppression of telomerase activity associated with down-regulated hTERT.
PMID: 11766737
Int J Cancer. 2008 Apr 1;122(7):1506-11. Induction of acquired resistance to antiestrogen by reversible mitochondrial DNA depletion in breast cancer cell line.
Although the net benefits of tamoxifen in adjuvant breast cancer therapy have been proven, the recurrence of the cancer in an aggressive and hormone independent form has been highly problematic. We previously demonstrated the important role mitochondrial DNA (mtDNA) plays in hormone-independence in prostate cancer. Here, the role of mtDNA in breast cancer progression was investigated. We established hydroxytamoxifen (4-OHT) resistant HTRMCF by growing MCF-7, human breast adenocarcinoma cells, in the presence of 4-OHT. HTRMCF was cross-resistant to 4-OHT and ICI182,780 concurrent with the depletion of mtDNA. To further investigate the role of mtDNA depletion, MCF-7 was depleted of mtDNA by treatment with ethidium bromide. MCF Rho 0 was resistant to both 4-OHT and ICI182,780. Furthermore, cybrid (MCFcyb) prepared by fusion MCF Rho 0 with platelet to transfer mtDNA showed susceptibility to antiestrogen. Surprisingly, after withdrawal of 4-OHT for 8 weeks, HTRMCF and their clones became susceptible to both drugs concurrent with a recovery of mtDNA. Herein, our results substantiated the first evidence that the depletion of mtDNA induced by hormone therapy triggers a shift to acquired resistance to hormone therapy in breast cancer. In addition, we showed that mtDNA depletion can be reversed, rendering the cancer cells susceptible to antiestrogen. The fact that the hormone independent phenotype can be reversed should be a step toward more effective treatments for estrogen-responsive breast cancer. (c) 2007 Wiley-Liss, Inc.
PMID: 17990320 [PubMed - indexed for MEDLINE]PMCID: PMC2293290Free PMC Article
Biological Determinants of Endocrine Resistance in Breast Cancer
Elizabeth A. Musgrove; Robert L. Sutherland
Published: 09/24/2009
Abstract
Endocrine therapies targeting oestrogen action (anti-oestrogens, such as tamoxifen, and aromatase inhibitors) decrease mortality from breast cancer, but their efficacy is limited by intrinsic and acquired therapeutic resistance. Candidate molecular biomarkers and gene expression signatures of tamoxifen response emphasize the importance of deregulation of proliferation and survival signalling in endocrine resistance. However, definition of the specific genetic lesions and molecular processes that determine clinical endocrine resistance is incomplete. The development of large-scale computational and genetic approaches offers the promise of identifying the mediators of endocrine resistance that may be exploited as potential therapeutic targets and biomarkers of response in the clinic.
Endocrine-Related Cancer 12 (3) 599 -614 DOI: 10.1677/erc.1.00946 Antiestrogen-resistant human breast cancer cells require activated Protein Kinase B/Akt for growth 2005
T Frogne, J S Jepsen, S S Larsen, C K Fog, B L Brockdorff and A E Lykkesfeldt Department of Tumor Endocrinology, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark
(Requests for offprints should be addressed to A E Lykkesfeldt; Email: al@cancer.dk)
Development of acquired resistance to antiestrogens is a majorclinical problem in endocrine treatment of breast cancer patients.The IGF system plays a profound role in many cancer types, includingbreast cancer. Thus, overexpression and/or constitutive activationof the IGF-I receptor (IGF-IR) or different components of theIGF-IR signaling pathway have been reported to render breastcancer cells less estrogen dependent and capable of sustainingcell proliferation in the presence of antiestrogens. In thisstudy, growth of the antiestrogen-sensitive human breast cancercell line MCF-7 was inhibited by treatment with IGF-IR-neutralizingantibodies. In contrast, IGF-IR-neutralizing antibodies hadno effect on growth of two different antiestrogen-resistantMCF-7 sublines. A panel of antiestrogen-resistant cell lineswas investigated for expression of IGF-IR and either undetectableor severely reduced IGF-IR levels were observed. No increasein insulin receptor substrate 1 (IRS-1) or total PKB/Akt (Akt)was detected in the resistant cell lines. However, a significantincrease in phosphorylated Akt (pAkt) was found in four of sixantiestrogen-resistant cell lines. Overexpression of pAkt wasassociated with increased Akt kinase activity in both a tamoxifen-and an ICI 182,780-resistant cell line. Inhibition of Akt phosphorylationby the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmanninor the Akt inhibitor SH-6 (structurally modified phosphatidylinositol ether liquid analog PIA 6) resulted in a more pronouncedgrowth inhibitory effect on the antiestrogen-resistant cellscompared with the parental cells, suggesting that signalingvia Akt is required for antiestrogen-resistant cell growth inat least a subset of our antiestrogen-resistant cell lines.PTEN expression and activity was not decreased in cell linesoverexpressing pAkt. Our data demonstrate that Akt is a targetfor treatment of antiestrogen-resistant breast cancer cell linesand we suggest that antiestrogen-resistant breast cancer patientsmay benefit from treatment targeted to inhibit Akt signaling.
Use of Metformin(IGF-), Tykerb(EGF)?
J Steroid Biochem Mol Biol. 2009 Oct 6. [Epub ahead of print] Estrogen utilization of IGF-1-R and EGF-R to signal in breast cancer cells.
Song RX, Chen Y, Zhang Z, Bao Y, Yue W, Wang JP, Fan P, Santen RJ.
Department of Internal Medicine, University of Virginia School of Medicine, 450 Ray Hunt Dr., Charlottesville, VA 22903, USA. As breast cancer cells develop secondary resistance to estrogen deprivation therapy, they increase their utilization of non-genomic signaling pathways. Our prior work demonstrated that estradiol causes an association of ERalpha with Shc, Src and the IGF-1-R. In cells developing resistance to estrogen deprivation (surrogate for aromatase inhibition) and to the anti-estrogens tamoxifen, 4-OH-tamoxifen, and fulvestrant, an increased association of ERalpha with c-Src and the EGF-R occurs. At the same time, there is a translocation of ERalpha out of the nucleus and into the cytoplasm and cell membrane. Blockade of c-Src with the Src kinase inhibitor, PP-2 causes relocation of ERalpha into the nucleus. While these changes are not identical in response to each anti-estrogen, ERalpha binding to the EGF-R is increased in response to 4-OH-tamoxifen when compared with tamoxifen. The changes in EGF-R interactions with ERalpha impart an enhanced sensitivity of tamoxifen-resistant cells to the inhibitory properties of the specific EGF-R tyrosine kinase inhibitor, AG 1478. However, with long term exposure of tamoxifen-resistant cells to AG 1478, the cells begin to re-grow but can now be inhibited by the IGF-R tyrosine kinase inhibitor, AG 1024. These data suggest that the IGF-R system becomes the predominant signaling mechanism as an adaptive response to the EGF-R inhibitor. Taken together, this information suggests that both the EGF-R and IGF-R pathways can mediate ERalpha signaling. To further examine the effects of fulvestrant on ERalpha function, we examined the acute effects of fulvestrant, on non-genomic functionality. Fulvestrant enhanced ERalpha association with the membrane IGF-1-receptor (IGF-1-R). Using siRNA or expression vectors to knock-down or knock-in selective proteins, we further demonstrated that the ERalpha/IGF-1-R association is Src-dependent. Fulvestrant rapidly induced IGF-1-R and MAPK phosphorylation. The Src inhibitor PP2 and IGF-1-R inhibitor AG1024 greatly blocked fulvestrant-induced ERalpha/IGF-1-R interaction leading to a further depletion of total cellular ERalpha induced by fulvestrant and further enhanced fulvestrant-induced cell growth arrest. More dramatic was the translocation of ERalpha to the plasma membrane in combination with the IGF-1-R as shown by confocal microscopy. Taken in aggregate, these studies suggest that secondary resistance to hormonal therapy results in usage of both IGF-R and EGF-R for non-genomic signaling.
PMID: 19815064 [PubMed - as supplied by publisher]
Int J Oncol. 2003 Aug;23(2):369-80. Induction of antiproliferation and apoptosis in estrogen receptor negative MDA-231 human breast cancer cells by mifepristone and 4-hydroxytamoxifen combination therapy: a role for TGFbeta1.
Liang Y, Hou M, Kallab AM, Barrett JT, El Etreby F, Schoenlein PV.
Department of Surgery, Medical College of Georgia, Augusta, GA, USA. Mifepristone (MIF) is an antiprogestin with potent anti-glucocorticoid and anti-androgen activity. MIF also appears to have anti-tumor activity independent of its ability to bind to nuclear receptors. In this study, we tested the ability of MIF to inhibit the growth of ER and PR negative breast cancer cells. In addition, because high-dose anti-estrogen treatment has been shown to inhibit ER and PR negative breast cancer cells, we compared the anti-proliferative activity of MIF to that of the anti-estrogen 4-hydroxytamoxifen (TAM) or combination hormonal therapy (MIF + TAM). MIF and TAM therapy induced a significant time- and dose-dependent growth inhibition and, ultimately, induced cell death in MDA-231 cells as evidenced by increased DNA fragmentation, cytochrome c release from the mitochondria, and the activation of caspase-3. The anti-proliferative activity of TAM plus MIF combination treatment was at least additive as compared to either monotherapy. The earliest indicator of TAM and MIF cytostatic and cytotoxic action on MDA-231 cells was a significant (p<0.05) induction of TGFbeta1 secretion into the growth medium within 4 h of treatment. Secreted TGFbeta1 levels at 24 and 48 h were significantly higher in the TAM plus MIF treatment group as compared to cells treated with TAM or MIF alone. TGFbeta1 neutralizing antibody or addition of mannose-6-phosphate (M6P), a reagent also used to inhibit TGFbeta1, significantly attenuated the TAM and/or MIF-induced cell growth inhibition and cell death. In summary, our results indicate that MIF used in combination with TAM can effectively kill estrogen-insensitive human breast cancer cells. Our study further implies that agents that effectively increase TGFbeta1 levels in ER negative breast cancer cells may be one treatment approach for hormone-independent breast cancers.
PMID: 12851686 [PubMed - indexed for MEDLINE]
Br J Cancer. 2010 Jan 19;102(2):342-50. Epub 2009 Dec 15. Pre-clinical evaluation of cyclin-dependent kinase 2 and 1 inhibition in anti-estrogen-sensitive and resistant breast cancer cells.
Johnson N, Bentley J, Wang LZ, Newell DR, Robson CN, Shapiro GI, Curtin NJ.
Northern Institute for Cancer Research, Newcastle University, Paul O' Gorman Building, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
BACKGROUND: Cellular proliferation, driven by cyclin-dependent kinases (CDKs) and their cyclin partners, is deregulated in cancer. Anti-estrogens, such as tamoxifen, antagonise estrogen-induced ERalpha transactivation of cyclin D1, resulting in reduced CDK4/6 activity, p27(Kip1)-mediated inhibition of CDK2 and growth arrest. We hypothesised that direct inhibition of CDK2 and CDK1 may overcome the major clinical problem of anti-estrogen resistance. METHODS: The cellular effects of CDK2/1 siRNA knockdown and purine-based CDK2/1 inhibitors, NU2058 and NU6102, were measured in anti-estrogen-sensitive and resistant breast cancer cell lines. RESULTS: CDK2 knockdown caused G1 accumulation, whereas CDK1 depletion caused G2/M slowing, and dual CDK1/2 depletion resulted in further G2/M accumulation and cell death in both anti-estrogen-sensitive and resistant cells, confirming CDK2 and CDK1 as targets for breast cancer therapy. In contrast to tamoxifen, which only affected hormone-sensitive cells, NU2058 and NU6102 reduced CDK2-mediated phosphorylation of pRb, E2F transcriptional activity and proliferation, ultimately resulting in cell death, in both anti-estrogen-sensitive and resistant cells. Both drugs caused G2/M arrest, reflective of combined CDK2/1 knockdown, with a variable degree of G1 accumulation. CONCLUSION: These studies confirm the therapeutic potential of CDK2 and CDK1 inhibitors for cancer therapy, and support their use as an alternative treatment for endocrine-resistant breast cancer.
PMID: 20010939 [PubMed - in process]
Endocr Relat Cancer. 2006 Dec;13 Suppl 1:S77-88. Deciphering antihormone-induced compensatory mechanisms in breast cancer and their therapeutic implications.
Gee JM, Shaw VE, Hiscox SE, McClelland RA, Rushmere NK, Nicholson RI.
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Redwood Building, Cardiff University, Cardiff, Wales, UK. gee@cardiff.ac.uk
Breast cancer inhibition by antihormones is rarely complete, and our studies using responsive models reveal the remarkable flexibility of breast cancer cells in recruiting alternative signalling to limit maximal anti-tumour effects of oestrogen receptor alpha (ER) blockade. The recruited mechanism involves antihormone-induced expression of oestrogen-repressed signalling genes. For example, epidermal growth factor receptor gene (EGFR) is induced by antioestrogens and maintains residual kinase and ER phosphorylation, cell survival genes, and thereby allows incomplete antihormone response and emergence of resistance. Microarrays are revealing the breadth of antihormone-induced genes that may attenuate growth inhibition, including NFkappaB, Bag1, 14-3-3zeta and tyrosine kinases, such as HER2 and Lyn. Three concepts are emerging: first, some genes are induced exclusively by antioestrogens, while others extend to oestrogen deprivation; secondly, some are transiently induced, while others persist into resistance; finally, some confer additional adverse features when tumour cells are in an appropriate context. Among the latter is CD59 whose antioestrogen induction may permit evasion of immune surveillance in vivo. Also, induction of pro-invasive genes (including NFkappaB, RhoE and delta-catenin) may underlie our findings that antioestrogens can markedly stimulate migratory behaviour when tumour intercellular contacts are compromised. Based on our promising studies selectively inhibiting EGFR (gefitinib), NFkappaB (parthenolide) or CD59 (neutralising antibody) together with antioestrogens, we propose that co-targeting strategies could markedly improve anti-tumour activity (notably enhancing cell kill) during the antihormone-responsive phase. Furthermore, subverting those induced signalling genes that are retained into resistance (e.g. EGFR, NFkappaB, HER2) may prove valuable in this state. Alongside future deciphering and targeting of genes underlying antioestrogen-promoted invasiveness, embracing of intelligent combination strategies could significantly extend patient survival.
PMID: 17259561 [PubMed - indexed for MEDLINE]
Endocr Relat Cancer. 2005 Jul;12 Suppl 1:S99-S111. Epidermal growth factor receptor/HER2/insulin-like growth factor receptor signalling and oestrogen receptor activity in clinical breast cancer.
Breast cancer models of acquired tamoxifen resistance, oestrogen receptor (ER)+ /ER- de novo resistance and gene transfer studies cumulatively demonstrate the increased importance of growth factor receptor signalling, notably the epidermal growth factor receptor (EGFR)/HER2, in tamoxifen resistance. Our recent in vitro studies also suggest that EGFR signalling productively cross-talks with insulin-like growth factor receptor (IGF-1R) and, where present, activates ER on key AF-1 serine residues to facilitate acquired tamoxifen-resistant growth. This paper presents our immunohistochemical evidence that EGFR/HER2 signalling (i.e. transforming growth factor (TGF)alpha, EGFR and HER2 expression; phosphorylation of EGFR, HER2 and ERK1/2 MAP kinase) is also prominent in clinical de novo resistant and modestly increased in acquired tamoxifen-resistant states, suggesting that anti-EGFR/HER2 strategies may prove valuable treatments. Primary breast cancer samples employed were obtained for (1) patients subsequently treated with tamoxifen for advanced disease where endocrine response and survival data were available and (2) ER+ elderly patients during tamoxifen response and relapse. We also present our clinical immunohistochemical findings that IGF-1R expression, its phosphorylation on tyrosine 1316, and also phosphorylation on serine 118 of ER are not only prominent in ER+ tamoxifen-responsive disease, but are also detectable in ER+ de novo and acquired tamoxifen-resistant breast cancer, where there is evidence of EGFR/ER cross-talk. Our data suggest that agents to deplete effectively ER or IGF-1R signalling may be of value in treating ER+ de novo/acquired tamoxifen resistance in addition to tamoxifen-responsive disease in vivo. IGF-1R inhibitors may also prove valuable in ER- patients, since considerable IGF-1R signalling activity was apparent within approximately 50% of such tumours.
PMID: 16113104 [PubMed - indexed for MEDLINE]Free Article
Quote:
Therapeutically,our new data suggest agents to deplete more effectively oestrogen/ER signalling, and also anti-IGF-1R strategies may prove valuableboth in tamoxifen-responsive disease and in ER+,de novo/acquiredtamoxifen resistance in vivo. Our experiences with Faslodexor IGF-1R inhibitors in vitro support this concept, as do theresponses to faslodex or aromatase inhibitors exhibited by someacquired tamoxifen-resistant patients (Johnston 2004) and, forthe latter agents, in a proportion of ER+,de novo tamoxifenresistance (Ellis et al. 2003). Finally, EGFR/HER2 components are markedly overexpressed inER– patients, mirroring the ER– phenotype in vitroas well as the most extreme growth factor signalling/transfectionmodels. ER– disease thus seems an obvious target for anti-EGFR/HER2agents. However, IGF-1R signalling is also present in thesetumours in vivo. While as yet not supported by model data, ourclinical findings do suggest that this pathway should also beconsidered as a target in ER– tumours.
Re: Endocrine resistance...reversed by inhibiting MAPK or PI3K/Akt signaling pathways
Breast Cancer Res Treat. 2010 May;121(1):1-11. Epub 2009 Jun 17. Androgen receptor overexpression induces tamoxifen resistance in human breast cancer cells.
Although the androgen receptor (AR) is a known clinical target in prostate cancer, little is known about its possible role in breast cancer. We have investigated the role of AR expression in human breast cancer in response to treatment with the antiestrogen tamoxifen. Resistance to tamoxifen is a major problem in treating women with breast cancer. By gene expression profiling, we found elevated AR and reduced estrogen receptor (ER) alpha mRNA in tamoxifen-resistant tumors. Exogenous overexpression of AR rendered ERalpha-positive MCF-7 breast cancer cells resistant to the growth-inhibitory effects of tamoxifen in anchorage-independent growth assays and in xenograft studies in athymic nude mice. AR-overexpressing cells remained sensitive to growth stimulation with dihydrotestosterone. Treatment with the AR antagonist Casodex (bicalutamide) reversed this resistance, demonstrating the involvement of AR signaling in tamoxifen resistance. In AR-overexpressing cells, tamoxifen induced transcriptional activation by ERalpha that could be blocked by Casodex, suggesting that AR overexpression enhances tamoxifen's agonistic properties. Our data suggest a role for AR overexpression as a novel mechanism of hormone resistance, so that AR may offer a new clinical therapeutic target in human breast cancers.
PMID: 19533338 [PubMed - in process]
Front Biosci. 2008 May 1;13:3273-87. The type I insulin-like growth factor receptor pathway: a key player in cancer therapeutic resistance.
The insulin-like growth factor (IGF) ligands stimulate cellular proliferation and survival by activating the type I insulin-like growth factor receptor (IGF-IR). As a result, the IGF signaling system is implicated in a number of cancers, including those of the breast, prostate, and lung. In addition to mitogenic and anti-apoptotic roles that may directly influence tumor development, IGF-IR also appears to be a critical determinant of response to numerous cancer therapies. This review describes the role of the IGF-IR pathway in mediating resistance to both general cytotoxic therapies, such as radiation and chemotherapy, and targeted therapies, such as tamoxifen and trastuzumab. It concludes with a description of approaches to target IGF-IR and argues that inhibition of IGF signaling, in conjunction with standard therapies, may enhance the response of cancer cells to multiple modalities.
PMID: 18508432 [PubMed - indexed for MEDLINE]
Eur J Cancer. 2010 May 13. [Epub ahead of print] Combining Src inhibitors and aromatase inhibitors: A novel strategy for overcoming endocrine resistance and bone loss.
PMID: 20471823 [PubMed - as supplied by publisher]
Breast Cancer Res Treat. 2010 Jul 29. [Epub ahead of print] Combined Src and ER blockade impairs human breast cancer proliferation in vitro and in vivo.
Antiestrogen therapies arrest susceptible estrogen receptor (ER)-positive breast cancers by increasing p27. Since Src phosphorylates p27 to promote p27 proteolysis, Src activation observed in up to 40% of ER-positive cancers may contribute to antiestrogen resistance. In this article, we show that treatment with the Src-inhibitor saracatinib (AZD0530) together with ER-blocking drugs increased breast cancer cell cycle arrest via p27. Saracatinib and fulvestrant together more effectively increased p27, reduced Ki67, and impaired MDA-MB-361 xenograft tumor growth in vivo than either of the drugs alone. In contrast, saracatinib monotherapy rapidly gave rise to drug resistance. Since combined ER and Src inhibition delays development of resistance in vivo, these data support further clinical investigation of saracatinib in combination with fulvestrant for women with ER-positive breast cancer. Proteomic analysis revealed striking bypass activation of the mTOR pathway in saracatinib-resistant tumors. mTORC1 activation also arose following long-term culture of ER-positive breast cancer lines in the presence of saracatinib. These data indicate the utility of proteomic analysis of drug-resistant tumors to identify potential means of drug resistance. The use of mTOR kinase inhibitors with saracatinib may subvert drug resistance and prove to be more effective than saracatinib alone.
PMID: 20669046 [PubMed - as supplied by publisher]
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