[Rich66]

(combination therapies, her2 therapies making ER- antiestrogen sensitive etc, Traz + Serm+AI)



Combined ER and HER-targeted therapy in breast cancer treatment

Citation: THE BREAST, Volume 18, Supplement 1, March 2009, Page S8

K. Osborne¹, R. Schiff<sup>1

1</sup>Breast Center, Baylor College of Medicine, Houston, USA

The estrogen receptor (ER) and HER signaling networks are complex, redundant, evolvable and robust pathways, each with several regulatory controls. Several levels of crosstalk between these two networks act as modulatory circuits that when altered can contribute to resistance to therapies targeting them. Nuclear ER when bound by estrogen increases the expression of ligands binding to HER receptors while at the same time reducing the expression of the receptors themselves. At the same time, the HER signaling pathway reduces expression of ER and progesterone receptor (PR) while it can activate ER functionally through phosphorylation of the receptor and its coactivators. Therefore, blockade of ER signaling by endocrine therapy can increase the cellular content of HER1 and HER2, while blockade of HER signaling can increase the expression of ER and PR. Non-nuclear ER can also activate the HER signaling pathway by several mechanisms at the level of the cell membrane. Although there are several potential mechanisms for resistance to ER and HER-targeted therapy, preclinical data from our group and others, as well as supporting data from recent clinical trials, indicate that upregulation at the HER signaling pathway can cause resistance to ER-targeted therapy and that upregulation of ER signaling can cause resistance to HER-targeted therapy.
These data suggest that optimal treatment in some patients using therapies targeting these two pathways might necessitate simultaneous blockade of both pathways. In preclinical models and, now, data from clinical trials, simultaneous use of endocrine therapy to target ER and therapy targeting the HER receptor network can overcome resistance to endocrine therapy and delay the time to tumor progression. Using a combination of HER inhibitors to completely block the HER pathway together with ER blockade is very potent therapy in preclinical xenograft models of ER+/HER2+ tumors and is able to eradicate tumors even after short term therapy. In ER+ tumors that express initially low levels of HER receptors, the addition of HER receptor blockade to endocrine therapy anticipating upregulation of HER receptors during endocrine therapy delays the emergence of resistance and prolongs time to progression. Combined HER-targeted therapy in this situation does not eradicate these xenograft tumors indicating that other survival pathways still function and that these tumors have not yet become “oncogene addicted” to the HER pathway. There is an urgent need to biopsy patients immediately before embarking on targeted therapy to profile the tumor and to select the optimal patient for this new approach.



ENDO: ER Negative Breast CA Cells Turn Positive with Trastuzumab

2009-06-18T12:58:05-04:00WASHINGTON, June 18 (MedPage Today) -- A drug used to treat breast cancer carrying the HER2 receptor made cells sensitive to hormonal therapy, suggesting a new strategy for treating the disease, an investigator reported here.
Estrogen receptor-negative, human epidermal growth factor receptor-2 (HER2)-positive breast cancer cells converted to ER-positive status after exposure to trastuzumab (Herceptin).
After three days of exposure to trastuzumab in vitro, the previously ER-negative cells exhibited upregulation of ER±, Gauri Sabnis, PhD, of the University of Maryland in Baltimore, said at the Endocrine Society meeting.
Moreover, trastuzumab-stimulated cells responded to the growth-inhibiting effects of antiestrogens and aromatase inhibitors.
"This strategy may offer a new avenue for treatment of breast cancer patients with ER-negative and HER2-positive tumors," Dr. Sabnis concluded.
About 25% of breast cancers are ER negative: typically they're treated with chemotherapy and radiation only, because endocrine therapy usually has no growth-inhibiting activity in such tumors.
In previous studies, Dr. Sabnis and colleagues found that breast cancer cells and tumors resistant to an aromatase inhibitor had reduced levels of ER± and increased levels of HER2.
The aromatase inhibitor-resistant cells had been derived from an ER-positive cell line, leading investigators to examine whether HER2 inhibition would lead to upregulation of ER± in ER-negative, HER2-positive cells.
Dr. Sabnis and colleagues added trastuzumab at a concentration of 50 mcg/mL to ER-negative cells and evaluated ER expression after 72 hours.
Investigators then treated the cells with different concentrations of estradiol and the estradiol precursor androstenedione. The hormones triggered proliferation of the formerly ER-negative cells.
Subsequently, the investigators evaluated the effects of aromatase inhibitors and antiestrogens on trastuzumab-pretreated ER-negative cancer cells.
They observed significant growth inhibition -- comparable to what occurs when ER-positive cells are exposed to aromatase inhibitors or antiestrogens.
The inhibition was significantly greater than treatment with an aromatase inhibitor or antiestrogen alone -- or with trastuzumab alone.
For example, letrozole (Femara) had an IC₅₀ of 3 nmol, which is similar to the growth inhibiting response the aromatase inhibitor has in ER-positive cells, said Dr. Sabnis.
A literature review uncovered evidence that trastuzumab might also upregulate ER± in humans with ER-negative breast cancer.
Italian investigators gave trastuzumab to 10 patients with HER2-positive, ER-negative breast cancer. Three of the 10 subsequently had upregulation of ER±, and two of the three were treated with letrozole monotherapy and remained progression free for as long as three years (Breast Cancer Res 2006; 8(6): 407).
Moreover, a clinical trial initiated at the University of Michigan in Ann Arbor is evaluating trastuzumab's ability to induce ER expression in patients with ER-negative, HER2-positive breast cancer.
Dr. Sabnis reported no disclosures. Co-investigator Angela Brodie, PhD, disclosed a financial relationship with Syndax.
Primary source: The Endocrine Society Source reference: Sabnis G, Brodie A "Trastuzumab sensitizes ER negative, HER-2 positive breast cancer cells (SKBr-3) to endocrine therapy" ENDO 2009; Abstract OR38-02.

1: Breast Cancer Res Treat. 2009 Aug 21. [Epub ahead of print] Links

Breast cancer cells can switch between estrogen receptor alpha and ErbB signaling and combined treatment against both signaling pathways postpones development of resistance.

Sonne-Hansen K, Norrie IC, Emdal KB, Benjaminsen RV, Frogne T, Christiansen IJ, Kirkegaard T, Lykkesfeldt AE.
Department of Tumor Endocrinology, Institute of Cancer Biology, Danish Cancer Society, Strandboulevarden 49, 2100, Copenhagen, Denmark.
The majority of breast cancers are estrogen responsive, but upon progression of disease other growth promoting pathways are activated, e.g., the ErbB receptor system. The present study focuses on resistance to the pure estrogen antagonist fulvestrant and strategies to treat resistant cells or even circumvent development of resistance. Limited effects were observed when targeting EGFR and ErbB2 with the monoclonal antibodies cetuximab, trastuzumab, and pertuzumab, whereas the pan-ErbB inhibitor CI-1033 selectively inhibited growth of fulvestrant resistant cell lines. CI-1033 inhibited Erk but not Akt signaling, which as well as Erk is important for antiestrogen resistant cell growth. Accordingly, combination therapy with CI-1033 and the Akt inhibitor SH-6 or the Protein Kinase C inhibitor RO-32-0432 was applied and found superior to single agent treatment. Further, the resistant cell lines were more sensitive to CI-1033 treatment when grown in the presence of fulvestrant, as withdrawal of fulvestrant restored signaling through the estrogen receptor alpha (ERalpha), partly overcoming the growth inhibitory effects of CI-1033. Thus, the resistant cells could switch between ERalpha and ErbB signaling for growth promotion. Although parental MCF-7 cell growth primarily depends on ERalpha signaling, a heregulin-1beta induced switch to ErbB signaling rescued MCF-7 cells from the growth inhibition exerted by fulvestrant-mediated blockade of ERalpha signaling. This interplay between ERalpha and ErbB signaling could be abrogated by combined therapy targeting both receptor systems. Thus, the present study indicates that upon development of antiestrogen resistance, antiestrogen treatment should be continued in combination with signal transduction inhibitors. Further, upfront combination of endocrine therapy with pan-ErbB inhibition may postpone or even prevent development of treatment resistance.
PMID: 19697122 [PubMed - as supplied by publisher

Herceptin turning ER- to ER+

http://www.breastcancer.org/treatmen.../20090618c.jsp

WASHINGTON, June 18 (MedPage Today) -- A drug used to treat breast cancer carrying the HER2 receptor made cells sensitive to hormonal therapy, suggesting a new strategy for treating the disease, an investigator reported here.
Estrogen receptor-negative, human epidermal growth factor receptor-2 (HER2)-positive breast cancer cells converted to ER-positive status after exposure to trastuzumab (Herceptin).
After three days of exposure to trastuzumab in vitro, the previously ER-negative cells exhibited upregulation of ER±, Gauri Sabnis, PhD, of the University of Maryland in Baltimore, said at the Endocrine Society meeting.
Moreover, trastuzumab-stimulated cells responded to the growth-inhibiting effects of antiestrogens and aromatase inhibitors .
"This strategy may offer a new avenue for treatment of breast cancer patients with ER-negative and HER2-positive tumors," Dr. Sabnis concluded.
About 25% of breast cancers are ER negative: typically they're treated with chemotherapy and radiation only, because endocrine therapy usually has no growth-inhibiting activity in such tumors.
In previous studies, Dr. Sabnis and colleagues found that breast cancer cells and tumors resistant to an aromatase inhibitor had reduced levels of ER± and increased levels of HER2.
The aromatase inhibitor-resistant cells had been derived from an ER-positive cell line, leading investigators to examine whether HER2 inhibition would lead to upregulation of ER± in ER-negative, HER2-positive cells.
Dr. Sabnis and colleagues added trastuzumab at a concentration of 50 mcg/mL to ER-negative cells and evaluated ER expression after 72 hours.
Investigators then treated the cells with different concentrations of estradiol and the estradiol precursor androstenedione. The hormones triggered proliferation of the formerly ER-negative cells.
Subsequently, the investigators evaluated the effects of aromatase inhibitors and antiestrogens on trastuzumab-pretreated ER-negative cancer cells.
They observed significant growth inhibition -- comparable to what occurs when ER-positive cells are exposed to aromatase inhibitors or antiestrogens.
The inhibition was significantly greater than treatment with an aromatase inhibitor or antiestrogen alone -- or with trastuzumab alone.
For example, letrozole (Femara) had an IC₅₀ of 3 nmol, which is similar to the growth inhibiting response the aromatase inhibitor has in ER-positive cells, said Dr. Sabnis.
A literature review uncovered evidence that trastuzumab might also upregulate ER± in humans with ER-negative breast cancer.
Italian investigators gave trastuzumab to 10 patients with HER2-positive, ER-negative breast cancer. Three of the 10 subsequently had upregulation of ER±, and two of the three were treated with letrozole monotherapy and remained progression free for as long as three years (Breast Cancer Res 2006; 8(6): 407).
Moreover, a clinical trial initiated at the University of Michigan in Ann Arbor is evaluating trastuzumab's ability to induce ER expression in patients with ER-negative, HER2-positive breast cancer.
Dr. Sabnis reported no disclosures. Co-investigator Angela Brodie, PhD, disclosed a financial relationship with Syndax.
Primary source: The Endocrine Society Source reference: Sabnis G, Brodie A "Trastuzumab sensitizes ER negative, HER-2 positive breast cancer cells (SKBr-3) to endocrine therapy" ENDO 2009; Abstract OR38-02.

Tumori. 2009 Nov-Dec;95(6):804-7.
Inhibition of HER2/estrogen receptor cross-talk, probable relation to prolonged remission of stage IV breast cancer: a case report.

Tisman G.
Whittier Cancer Research Building, 13025 Bailey Street, Suite A, Whittier, CA 90601, USA. glennmd@gmail.com
Metastatic breast cancer to the liver is considered incurable. Though many patients with liver metastases may enjoy response to chemo-, immuno- and hormonal therapy, those so inflicted rarely remain disease-free from the time of diagnosis for longer than 6-11 months. New laboratory and clinical research identified that cross-talk between activation of the epidermal growth factor family of tyrosine kinase transduction pathways (EGF/HER2) and estrogen receptor (ER) activation plays a role in resistance to hormonal therapy. A 59-year-old woman with a 4.5-cm invasive ductal, ER-positive/PR-negative, grade III adenocarcinoma of the breast was treated with mastectomy. Staging revealed biopsy-proven liver metastases. Surgery was immediately followed with vinorelbine, trastuzumab, tamoxifen and exemestane. The patient underwent a bone scan and PET/CT documented complete remission. She has remained in complete remission for 7 years. It is proposed that a possible mechanism for prolonged remission of stage IV breast cancer in this patient may be related to suppression of EGF/HER2 by trastuzumab, thus inhibiting cross-talk-associated tamoxifen/estrogen withdrawal resistance.

PMID: 20210247 [PubMed - in process]

Tamoxifen and exemestane were started after discontinuation of vinorelbine after only 6 weeks of therapy due to a vinorelbine-induced rash. Complete clinical response was confirmed after 2 months from the start of therapy. The patient has remained free of disease for 7 years and receives trastuzumab 6 mg/kg every 6 weeks, tamoxifen 20 mg daily, and exemestane 25 mg daily.

The ATAC study reported less than optimal activity for the combination of tamoxifen and anastrozole when compared to the AI alone20. It was decided, however, to continue this patient on the combination of tamoxifen plus AI because of the early success of therapy.

It is conjectured that this patient’s prolonged complete remission of 7+ years may represent the result of inhibition of EGFR/HER2-ER cross-talk, thus prolonging benefit from hormonal therapy. However, it is also possible – though less likely – that the independent effects of trastuzumab, tamoxifen and exemestane inhibition of tumor growth is responsible as well.

Int J Oncol. 2007 Feb;30(2):509-20.
Role for HER2/neu and HER3 in fulvestrant-resistant breast cancer.

Osipo C, Meeke K, Cheng D, Weichel A, Bertucci A, Liu H, Jordan VC.
Department of Pathology, Oncology Institute, Cardinal Bernadin Cancer Center, Loyola University Medical Center, Maywood, IL, USA.
Tamoxifen resistance is common for estrogen receptor alpha (ERalpha) positive breast cancer. Second-line therapies include aromatase inhibitors or fulvestrant. We have shown previously that fulvestrant reversed 17beta-estradiol-induced tumor regression of tamoxifen-stimulated MCF-7 xenografts (MCF-7TAMLT) treated for >5 years with tamoxifen in athymic mice and paradoxically stimulated growth. We investigated mechanisms responsible for growth by fulvestrant in the presence of physiologic estradiol and therapeutic strategies in vivo. The results demonstrated that only estradiol increased expression of the estrogen-responsive genes, c-myc, igf-1, cathepsin D, and pS2 mRNAs, in MCF-7E2 and MCF-7TAMLT tumors. Tamoxifen or fulvestrant decreased the estradiol-induced increase of these mRNAs in both tumor models. However, tyrosine-phosphorylated HER2/ neu, HER3, phospho-extracellular-regulated kinase-1/2 (ERK-1/2), and phospho-glycogen synthetase kinase 3alpha (GSK3alpha) and beta proteins were increased in MCF-7TAMLT tumors treated with fulvestrant compared to estradiol, control, or tamoxifen. Phospho-HER2/neu interacted with HER3 protein in MCF-7TAMLT tumors. In order to determine whether the functional interaction of HER2/neu with HER3 is critical for growth of fulvestrant-stimulated MCF-7TAMLT tumors, pertuzumab (an antibody that blocks HER2/neu-HER3 interaction) was used in an in vivo xenograft growth assay. Only growth of fulvestrant-treated MCF-7TAMLT xenografts was decreased significantly by 37.2% in response to pertuzumab (P=0.004). Pertuzumab specifically decreased the interaction of HER2/neu protein with HER3 in fulvestrant-stimulated MCF-7TAMLT tumors. These results suggested growth of MCF-7TAMLT tumors by tamoxifen or fulvestrant is potentially independent of ERalpha transcriptional activity as evidenced by lack of induction of four estrogen-responsive genes. The results suggested that growth of MCF-7TAMLT tumors treated with fulvestrant in the presence of physiologic estradiol is in part mediated through enhanced signaling from the HER2/neu-HER3 pathway as pertuzumab partially inhibited growth and the interaction of HER2/neu with HER3 in vivo.

PMID: 17203234 [PubMed - indexed for MEDLINE]





Originally Her2 neg cells upregulate Her2 after Letrozole treatment:


Clin Breast Cancer. 2010 Feb 1;10(1):E6-E15.
Understanding resistance to endocrine agents: molecular mechanisms and potential for intervention.

Sabnis G, Brodie A.
Department of Pharmacology and Experimental Therapeutics, University of Maryland, Baltimore.
Background: We developed a mouse model system that mimics hormone-dependent postmenopausal breast cancer. In this model, human estrogen receptor-positive (ER+) breast cancer cells (MCF-7) stably transfected with aromatase (MCF-7Ca) are grown as tumors in ovariectomized female nude mice. Using this model, we have established that aromatase inhibitors (AIs) such as letrozole and anastrozole that reduce estrogen production are more effective than the antiestrogen agent tamoxifen. This intratumoral aromatase xenograft model has proved accurate in predicting the outcome of several clinical trials. Nevertheless, resistance to treatment might eventually occur. Materials and Methods: To investigate the mechanisms involved in the loss of sensitivity of the tumors to AIs, we developed a cell line isolated from the tumors of long-term letrozole-treated MCF-7Ca xenografts. This cell line was designated LTLT-Ca. Results: These cells exhibited lower expression of ERalpha and apparent "estradiol-independent" growth along with hyperactivation of growth factor receptor- mediated signaling pathways such as HER2/mitogen-activated protein kinase. The inhibition of HER2 with trastuzumab results in restoration of ERalpha and response to letrozole.

Conclusion: Our data suggest that inhibition of both the HER2 and estrogen signaling pathways is required to prolong the responsiveness of the tumors to endocrine therapies. In addition, we have shown that HER2 upregulation is an adaptive process that the tumors undergo during continued letrozole treatment, which is reversed upon removal of the treatment. The tumors regain responsiveness to letrozole after a short period "off" treatment. These studies suggest that by reversing the resistance to hormone therapy, patients could have a second response and could delay the need for chemotherapy.

PMID: 20133251 [PubMed - in process]



Urol Oncol. 2009 Jan-Feb;27(1):53-63.
The Coffey Lecture: steroidogenic enzyme inhibitors and hormone dependent cancer.

Brodie A, Njar V, Macedo LF, Vasaitis TS, Sabnis G.
Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, MD 21201, USA. abrodie@umaryland.edu
OBJECTIVES: To improve treatment for patients with breast and prostate cancer. METHODS: A number of novel inhibitors of steroidogenic enzymes have been developed. Their biological effects have been evaluated in a variety of preclinical models. Aromatase (estrogen synthetase) inhibitors have now been extensively tested in clinical trials in breast cancer patients. Inhibitors of 17alpha-hydroxylase/lyase have also been studied in preclinical models and are beginning trials in prostate cancer patients. RESULTS: The enzyme aromatase (CYP19) has proven to be an important therapeutic target. Inhibitors of aromatase (AIs) are showing greater benefit than antiestrogens in the treatment of breast cancer. Although effective in other conditions in both women and men, AIs have not been useful in benign prostatic hypertrophy or prostate cancer. However inhibitors of 17alphahydroxylase/lyase (CYP17) to block synthesis of androgens may be effective for prostate cancer. Recent clinical trials with abiraterone and preclinical studies with other novel CYP17 inhibitors, which also interact with the androgen receptor and cause its down-regulation, could provide a new approach for treating this disease. In further studies, we optimized treatment with aromatase inhibitors and antiestrogens utilizing an intratumoral aromatase xenograft model. AIs were more effective and sustained growth inhibition was longer than antiestrogens. However, inevitably tumors eventually began to grow despite continued treatment. Analysis of breast tumors from mice treated with letrozole revealed up-regulation of HER-2 and MAP Kinase signaling proteins and down-regulation of the estrogen receptor. Our studies showed that tumors adapt to AI treatment by activating alternate signaling pathways, thus enabling them to proliferate in the absence of estrogen. When mice bearing resistant tumors were treated with trastuzumab, the anti-HER-2 antibody (herceptin), HER-2 was decreased in the tumor but the estrogen receptor and aromatase were restored. Tumor growth was significantly inhibited by treatment with trastuzumab in addition to letrozole. CONCLUSIONS: Aromatase inhibitors are proving to be an effective new class of agents for the treatment of breast cancer. Compounds inhibiting 17alphahydroxylase/lyase have potential for the treatment of prostate cancer. Our results suggest that strategies to overcome resistance to these types of agents can restore sensitivity of the tumors to hormone therapy.

PMID: 19111799 [PubMed - indexed for MEDLINE]




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]