http://www.medscape.com/viewarticle/708394
(Many sections at link)
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
FULL TEXT
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 major clinical problem in endocrine treatment of breast cancer patients. The IGF system plays a profound role in many cancer types, including breast cancer. Thus, overexpression and/or constitutive activation of the IGF-I receptor (IGF-IR) or different components of the IGF-IR signaling pathway have been reported to render breast cancer cells less estrogen dependent and capable of sustaining cell proliferation in the presence of antiestrogens. In this study, growth of the antiestrogen-sensitive human breast cancer cell line MCF-7 was inhibited by treatment with IGF-IR-neutralizing antibodies. In contrast, IGF-IR-neutralizing antibodies had no effect on growth of two different antiestrogen-resistant MCF-7 sublines. A panel of antiestrogen-resistant cell lines was investigated for expression of IGF-IR and either undetectable or severely reduced IGF-IR levels were observed. No increase in insulin receptor substrate 1 (IRS-1) or total PKB/Akt (Akt) was detected in the resistant cell lines. However, a significant increase in phosphorylated Akt (pAkt) was found in four of six antiestrogen-resistant cell lines. Overexpression of pAkt was associated with increased Akt kinase activity in both a tamoxifen- and an ICI 182,780-resistant cell line. Inhibition of Akt phosphorylation by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin or the Akt inhibitor SH-6 (structurally modified phosphatidyl inositol ether liquid analog PIA 6) resulted in a more pronounced growth inhibitory effect on the antiestrogen-resistant cells compared with the parental cells, suggesting that signaling via Akt is required for antiestrogen-resistant cell growth in at least a subset of our antiestrogen-resistant cell lines. PTEN expression and activity was not decreased in cell lines overexpressing pAkt. Our data demonstrate that Akt is a target for treatment of antiestrogen-resistant breast cancer cell lines and we suggest that antiestrogen-resistant breast cancer patients may 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]
Sorafenib may resensitize metastatic ER+ bc to AI's
http://www.medicalnewstoday.com/articles/120600.php
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.
Gee JM,
Robertson JF,
Gutteridge E,
Ellis IO,
Pinder SE,
Rubini M,
Nicholson RI.
Tenovus Centre for Cancer Research, Welsh School of Pharmacy, Redwood Building, Cardiff University, Cardiff, UK.
gee@cardiff.ac.uk
FREE TEXT
Abstract
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
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Therapeutically, our new data suggest agents to deplete more effectively oestrogen/ ER signalling, and also anti-IGF-1R strategies may prove valuable both in tamoxifen-responsive disease and in ER+, de novo/acquired tamoxifen resistance in vivo. Our experiences with Faslodex or IGF-1R inhibitors in vitro support this concept, as do the responses to faslodex or aromatase inhibitors exhibited by some acquired tamoxifen-resistant patients (Johnston 2004) and, for the latter agents, in a proportion of ER+, de novo tamoxifen resistance (Ellis et al. 2003). Finally, EGFR/HER2 components are markedly overexpressed in ER– patients, mirroring the ER– phenotype in vitro as well as the most extreme growth factor signalling/transfection models. ER– disease thus seems an obvious target for anti-EGFR/HER2 agents. However, IGF-1R signalling is also present in these tumours in vivo. While as yet not supported by model data, our clinical findings do suggest that this pathway should also be considered as a target in ER– tumours.
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