Mechanisms of tumor regression and resistance to estrogen deprivation and fulvestrant in a model of estrogen receptor-positive, HER-2/neu-positive breast cancer.
15 Aug 2006-Cancer Research (American Association for Cancer Research)-Vol. 66, Iss: 16, pp 8266-8273
TL;DR: The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib significantly delayed the emergence of resistance to both estrogen deprivation and fulvestrant, but reactivation of HER-2/neu and signaling through AKT leads to tumor regrowth.
Abstract: HER-2/neu in breast cancer is associated with tamoxifen resistance, but little data exist on its interaction with estrogen deprivation or fulvestrant. Here, we used an in vivo xenograft model of estrogen receptor (ER)-positive breast cancer with HER-2/neu overexpression (MCF7/HER-2/neu-18) to investigate mechanisms of growth inhibition and treatment resistance. MCF7/HER-2/neu-18 tumors were growth inhibited by estrogen deprivation and with fulvestrant, but resistance developed in 2 to 3 months. Inhibited tumors had reductions in ER, insulin-like growth factor-I receptor (IGF-IR), phosphorylated HER-2/neu (p-HER-2/neu), and phosphorylated p42/44 mitogen-activated protein kinase (p-MAPK). p27 was increased especially in tumors sensitive to estrogen deprivation. Tumors with acquired resistance to these therapies had complete loss of ER, increased p-HER-2/neu, increased p-MAPK, and reduced p27. In contrast, IGF-IR and phosphorylated AKT (p-AKT) levels were markedly reduced in these resistant tumors. The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib, which can block EGFR/HER-2/neu signaling, significantly delayed the emergence of resistance to both estrogen deprivation and fulvestrant. Levels of p-MAPK and p-AKT decreased with gefitinib, whereas high ER levels were restored. Eventually, however, tumors progressed in mice treated with gefitinib combined with estrogen deprivation or fulvestrant accompanied again by loss of ER and IGF-IR, increased p-HER-2/neu, high p-MAPK, and now increased p-AKT. Thus, estrogen deprivation and fulvestrant can effectively inhibit HER-2/neu-overexpressing tumors but resistance develops quickly. EGFR/HER-2/neu inhibitors can delay resistance, but reactivation of HER-2/neu and signaling through AKT leads to tumor regrowth. Combining endocrine therapy with EGFR/HER-2/neu inhibitors should be tested in clinical breast cancer, but a more complete blockade of EGFR/HER-2/neu may be optimal.
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TL;DR: The need to better identify a priori the patients whose tumors are most likely to benefit from new treatment combinations targeting both ER and growth factor receptor signaling to block the crosstalk between these pathways and eliminate escape routes is highlighted.
Abstract: The estrogen receptor (ER) pathway plays a pivotal role in breast cancer development and progression. Endocrine therapy to block the ER pathway is highly effective, but its usefulness is limited by common intrinsic and acquired resistance. Multiple mechanisms responsible for endocrine resistance have been proposed and include deregulation of various components of the ER pathway itself, alterations in cell cycle and cell survival signaling molecules, and the activation of escape pathways that can provide tumors with alternative proliferative and survival stimuli. Among these, increased expression or signaling of growth factor receptor pathways, especially the EGFR/HER2 pathway, has been associated with both experimental and clinical endocrine therapy resistance. New treatment combinations targeting both ER and growth factor receptor signaling to block the crosstalk between these pathways and eliminate escape routes have been proven highly effective in preclinical models. Results of recent clinical studies, while partly supporting this approach, also highlight the need to better identify a priori the patients whose tumors are most likely to benefit from these specific cotargeting strategies.
1,013 citations
TL;DR: In this paper, the authors evaluated the effect of adding lapatinib, a dual tyrosine kinase inhibitor blocking epidermal growth factor receptor and HER2, to the aromatase inhibitor letrozole as first-line treatment of hormone receptor-positive metastatic breast cancer.
Abstract: Purpose Cross-talk between human epidermal growth factor receptors and hormone receptor pathways may cause endocrine resistance in breast cancer. This trial evaluated the effect of adding lapatinib, a dual tyrosine kinase inhibitor blocking epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2), to the aromatase inhibitor letrozole as first-line treatment of hormone receptor (HR) –positive metastatic breast cancer (MBC). Patients and Methods Postmenopausal women with HR-positive MBC were randomly assigned to daily letrozole (2.5 mg orally) plus lapatinib (1,500 mg orally) or letrozole and placebo. The primary end point was progression-free survival (PFS) in the HER2-positive population. Results In HR-positive, HER2-positive patients (n 219), addition of lapatinib to letrozole significantly reduced the risk of disease progression versus letrozole-placebo (hazard ratio [HR] 0.71; 95% CI, 0.53 to 0.96; P .019); median PFS was 8.2 v 3.0 months, respectively. Clinical benefit (responsive or stable disease 6 months) was significantly greater for lapatinib-letrozole versus letrozole-placebo (48% v 29%, respectively; odds ratio [OR] 0.4; 95% CI, 0.2 to 0.8; P .003). Patients with centrally confirmed HR-positive, HER2-negative tumors (n 952) had no improvement in PFS. A preplanned Cox regression analysis identified prior antiestrogen therapy as a significant factor in the HER2-negative population; a nonsignificant trend toward prolonged PFS for lapatinib-letrozole was seen in patients who experienced relapse less than 6 months since prior tamoxifen discontinuation (HR 0.78; 95% CI, 0.57 to 1.07; P .117). Grade 3 or 4 adverse events were more common in the lapatinib-letrozole arm versus letrozole-placebo arm (diarrhea, 10% v 1%; rash, 1% v 0%, respectively), but they were manageable.
903 citations
01 Nov 2009
TL;DR: It is demonstrated that a combined targeted strategy with letrozole and lapatinib significantly enhances PFS and clinical benefit rates in patients with MBC that coexpresses HR and HER2.
869 citations
Cites background from "Mechanisms of tumor regression and ..."
...that initially lack EGFR or HER2 develop acquired resistance over time with enhanced expression of receptors involved in cross-talk with ER.(10-14) Two randomized trials in HR-positive MBC suggested that the EGFR tyrosine kinase inhibitor (TKI) gefitinib may improve PFS when added to endocrine therapy....
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...Coexpression of HER2 in HR-positive breast cancer confers relative endocrine resistance, and preclinical models have used targeted strategies to enhance efficacy of either tamoxifen or estrogen deprivation.(13,14,32-34) The Trastuzumab in Dual HER2 ER-Positive Metastatic Breast Cancer (TAnDEM) trial evaluated anastrozole with or without the addition of trastuzumab in HR-positive, HER2positive MBC (n 208)(9) and showed that the combined approach had a significant benefit for PFS....
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TL;DR: The aim of this review article is to summarize the current knowledge on mechanisms of resistance of breast cancer cells to endocrine therapies due to the crosstalk between the ER and the HER growth factor receptor signaling pathways and to explore new available therapeutic strategies that could prolong duration of response and circumvent endocrine resistant tumor growth.
Abstract: Breast cancer evolution and tumor progression are governed by the complex interactions between steroid receptor [estrogen receptor (ER) and progesterone receptor] and growth factor receptor signaling. In recent years, the field of cancer therapy has witnessed the emergence of multiple strategies targeting these specific cancer pathways and key molecules (ER and growth factor receptors) to arrest tumor growth and achieve tumor eradication; treatment success, however, has varied and both de novo (up front) and acquired resistance have proven a challenge. Recent studies of ER biology have revealed new insights into ER action in breast cancer and have highlighted the role of an intimate crosstalk between the ER and HER family signaling pathways as a fundamental contributor to the development of resistance to endocrine therapies against the ER pathway. The aim of this review article is to summarize the current knowledge on mechanisms of resistance of breast cancer cells to endocrine therapies due to the crosstalk between the ER and the HER growth factor receptor signaling pathways and to explore new available therapeutic strategies that could prolong duration of response and circumvent endocrine resistant tumor growth.
496 citations
Cites background or result from "Mechanisms of tumor regression and ..."
...Interestingly, MCF-7 cells adapted to grow in the presence of the potent antiestrogen fulvestrant also show increased EGFR signaling, suggesting that growth factor receptors play central roles in resistance to various endocrine therapies such as AIs and pure ER antagonists in addition to tamoxifen (94, 102, 103)....
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...The combination more effectively inhibited growth and delayed the acquired resistance that develops rapidly with estrogen deprivation alone (102)....
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...This contrasts with the good clinical response witnessed in this small HER2-positive group of patients and may suggest that resistance dependent on HER2 signaling might rapidly emerge as was reported in a recent preclinical model (102)....
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TL;DR: EGFR/HER2 may mediate tamoxifen resistance in ER-positive breast cancer despite continued suppression of ER genomic function by tamox ifen, providing a rationale to combine HER inhibitors with tamoxIFen in clinical studies, even in tumors that do not initially overexpress EGFR/ HER2.
Abstract: Not all breast cancers respond to tamoxifen, and many develop resistance despite initial benefit. We used an in vivo model of estrogen receptor (ER)-positive breast cancer (MCF-7 xenografts) to investigate mechanisms of this resistance and develop strategies to circumvent it. Epidermal growth factor receptor (EGFR) and HER2, which were barely detected in control estrogen-treated tumors, increased slightly with tamoxifen and were markedly increased when tumors became resistant. Gefitinib, which inhibits EGFR/HER2, improved the antitumor effect of tamoxifen and delayed acquired resistance, but had no effect on estrogen-stimulated growth. Phosphorylated levels of p42/44 and p38 mitogen-activated protein kinases (both downstream of EGFR/HER2) were increased in the tamoxifen-resistant tumors and were suppressed by gefitinib. There was no apparent increase in phosphorylated AKT (also downstream of EGFR/HER2) in resistant tumors, but it was nonetheless suppressed by gefitinib. Phosphorylated insulin-like growth factor-IR (IGF-IR), which can interact with both EGFR and membrane ER, was elevated in the tamoxifen-resistant tumors compared with the sensitive group. However, ER-regulated gene products, including total IGF-IR itself and progesterone receptor, remained suppressed even at the time of acquired resistance. Tamoxifen's antagonism of classic ER genomic function was retained in these resistant tumors and even in tumors that overexpress HER2 (MCF-7 HER2/18) and are de novo tamoxifen-resistant. In conclusion, EGFR/HER2 may mediate tamoxifen resistance in ER-positive breast cancer despite continued suppression of ER genomic function by tamoxifen. IGF-IR expression remains dependent on ER but is activated in the tamoxifen-resistant tumors. This study provides a rationale to combine HER inhibitors with tamoxifen in clinical studies, even in tumors that do not initially overexpress EGFR/HER2.
441 citations
Cites background or methods or result from "Mechanisms of tumor regression and ..."
...Interestingly, preclinical studies, as well as recent clinical studies, support combining aromatase inhibitors with growth factor pathway inhibitors in the subset of breast cancers overexpressing HER2 (18, 44), whereas using growth factor pathway inhibitors in combination with aromatase inhibitors was not beneficial in unselected patients with breast cancer (45, 46)....
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...1B previously published (18), and all the treatment groups were done as part of one xenograft experiment....
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...mice supplemented with estrogen pellets as previously described (9, 18)....
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References
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TL;DR: Gefitinib pretreatment eliminated tamoxifen's agonist effects, restored its antitumor activity both in vitro and in vivo in MCF-7/HER2-18 cells, and revealed molecular cross-talk between the ER and HER2 pathways was increased.
Abstract: Background: Patients receiving adjuvant tamoxifen whose tumors express high levels of both HER2/neu (HER2) and the estrogen receptor (ER) coactivator AIB1 often develop tamoxifen resistance. We used a breast cancer model system with high expression of AIB1 and HER2 to investigate the possible mechanisms underlying this resistance. Methods: MCF-7 breast cancer cells, which express high levels of AIB1, and a tamoxifen-resistant derivative cell line engineered to overexpress HER2 (MCF-7/HER2-18) were treated with estrogen, tamoxifen, epidermal growth factor (EGF), or heregulin in the absence or presence of the EGF receptor (EGFR) tyrosine kinase inhibitor gefitinib. We analyzed phosphorylation of signaling intermediates by immunoblotting, ER transcriptional activity with reporter gene constructs and immunoblot analysis of endogenous gene products, promoter assembly by chromatin immunoprecipitation (ChIP) assay, and tumor cell growth in vitro by anchorage-independent colony formation and in vivo using xenografts in nude mice. Results: MCF-7/HER2-18 tumors were completely growth inhibited by estrogen deprivation but were growth stimulated by tamoxifen. Molecular crosstalk between the ER and HER2 pathways was increased in the MCF-7/HER-2 cells compared with MCF-7 cells, with cross-phosphorylation and activation of both the ER and the EGFR/HER2 receptors, the signaling molecules AKT and ERK 1,2 mitogen-activated protein kinase (MAPK), and AIB1 itself with both estrogen and tamoxifen treatment. Tamoxifen recruited coactivator complexes (ER, AIB1, CBP, p300) to the ER-regulated pS2 gene promoter in MCF-7/ HER2-18 cells and corepressor complexes (NCoR, histone deacetylase 3) in MCF-7 cells. Gefitinib pretreatment blocked receptor cross-talk, reestablished corepressor complexes with tamoxifen-bound ER on target gene promoters, eliminated tamoxifen’ s agonist effects, and restored its antitumor activity both in vitro and in vivo in MCF-7/HER2-18 cells. Conclusions: Tamoxifen behaves as an estrogen agonist in breast cancer cells that express high levels of AIB1 and HER2, resulting in de novo resistance. Gefitinib’ s ability to eliminate this cross-talk and to restore tamoxifen’ s antitumor effects should be tested in the clinic. [J Natl Cancer Inst 2004; 96:926 ‐35]
1,140 citations
"Mechanisms of tumor regression and ..." refers background in this paper
...HER-2/neu-overexpressing breast cancer, show that inhibition of EGFR/HER-2/neu signaling may delay the emergence of resistance to treatment with estrogen deprivation and fulvestrant just as it overcomes de novo tamoxifen resistance in the model ( 6 )....
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...We have previously shown that MCF7 cells stably transfected with the HER-2/neu oncogene (MCF7/HER-2/ neu-18) rapidly form tumors in nude mice in the presence of estrogen and are de novo resistant to tamoxifen compared with the wild-type MCF7 tumors (4, 6 ). We have now compared the sensitivity of these MCF7/HER-2/neu-18 tumors to estrogen deprivation, estrogen deprivation plus fulvestrant, estrogen deprivation plus tamoxifen (6), and ......
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...ER in breast cancer regulates tumor growth in a liganddependent fashion via its classic action to regulate gene transcription in the nucleus and also by activities thought to originate outside the nucleus, perhaps in the plasma membrane or cytoplasm, that have been termed its nongenomic or membraneinitiated effects ( 6 , 12, 13)....
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...As we have shown recently, estrogen deprivation plus tamoxifen stimulates tumor growth due to the enhanced estrogen agonist activity of the drug derived from its ability to stimulate the rapid membrane activities of ER ( 6 )....
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...Studies in cell lines and xenograft models of human breast cancer suggest that these nongenomic activities of ER may be most relevant in tumors that overexpress EGFR/HER-2/neu ( 6 )....
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TL;DR: It is suggested that ErbB-1 and Erb B-2 signaling through ER is ligand-dependent and that the growth-promoting effects of these receptor tyrosine kinases on ER+ breast cancer can be inhibited by potent estrogen deprivation therapy.
Abstract: PURPOSE: Expression of ErbB-1 and ErbB-2 (epidermal growth factor receptor and HER2/neu) in breast cancer may cause tamoxifen resistance, but not all studies concur. Additionally, the relationship between ErbB-1 and ErbB-2 expression and response to selective aromatase inhibitors is unknown. A neoadjuvant study for primary breast cancer that randomized treatment between letrozole and tamoxifen provided a context within which these issues could be addressed prospectively. PATIENTS AND METHODS: Postmenopausal patients with estrogen– and/or progesterone receptor–positive (ER+ and/or PgR+) primary breast cancer ineligible for breast-conserving surgery were randomly assigned to 4 months of neoadjuvant letrozole 2.5 mg daily or tamoxifen 20 mg daily in a double-blinded study. Immunohistochemistry (IHC) for ER and PgR was conducted on pretreatment biopsies and assessed by the Allred score. ErbB-1 and ErbB-2 IHC were assessed by intensity and completeness of membranous staining according to published criteria. RE...
1,053 citations
TL;DR: It is shown that activation of protein kinase B (PKB)/Akt, contributes to resistance to antiproliferative signals and breast cancer progression in part by impairing the nuclear import and action of p27.
Abstract: Mechanisms linking mitogenic and growth inhibitory cytokine signaling and the cell cycle have not been fully elucidated in either cancer or in normal cells. Here we show that activation of protein kinase B (PKB)/Akt, contributes to resistance to antiproliferative signals and breast cancer progression in part by impairing the nuclear import and action of p27. Akt transfection caused cytoplasmic p27 accumulation and resistance to cytokine-mediated G1 arrest. The nuclear localization signal of p27 contains an Akt consensus site at threonine 157, and p27 phosphorylation by Akt impaired its nuclear import in vitro. Akt phosphorylated wild-type p27 but not p27T157A. In cells transfected with constitutively active AktT308DS473D (PKBDD), p27WT mislocalized to the cytoplasm, but p27T157A was nuclear. In cells with activated Akt, p27WT failed to cause G1 arrest, while the antiproliferative effect of p27T157A was not impaired. Cytoplasmic p27 was seen in 41% (52 of 128) of primary human breast cancers in conjunction with Akt activation and was correlated with a poor patient prognosis. Thus, we show a novel mechanism whereby Akt impairs p27 function that is associated with an aggressive phenotype in human breast cancer. NOTE: In the version of the article initially published online, the abstract contained one extraneous sentence. This error has been corrected in the HTML and PDF versions. The abstract will appear correctly in the forthcoming print issue.
960 citations
"Mechanisms of tumor regression and ..." refers background in this paper
...Interestingly, phosphorylation of p27 by AKT impairs its nuclear import in vitro, and cytoplasmic p27 in conjunction with AKT activation is correlated with poor patient prognosis ( 41 , 42)....
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TL;DR: This work proposes that selective estrogen receptor modulator (SERM) complexes with ERbeta and with truncated ERalpha derivatives use their DNA binding domain to titrate histone deacetylase (HDAC)-repressor complexes away from the Jun/Fos coactivator complex, thereby allowing unfettered activity of the coactivators.
921 citations
"Mechanisms of tumor regression and ..." refers background in this paper
...Nuclear activity increases the expression of genes regulated by ER binding to estrogen response elements or by ER tethering to other transcription factors, such as activator protein-1, in the promoters of genes that are important for cell proliferation and/or survival (12, 14 )....
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TL;DR: It is demonstrated that ErbBB2 overexpression and activity alone are insufficient to promote breast tumor cell division, andErbB3 is shown to be an essential partner in the transformation process, which functions as an oncogenic unit to drive breast cancer cell proliferation.
Abstract: ErbB2 is a receptor tyrosine kinase whose activity in normal cells depends on dimerization with another ligand-binding ErbB recep- tor. In contrast, amplification of c-erbB2 in tumors results in dramatic overexpression and constitutive activation of the recep- tor. Breast cancer cells overexpressing ErbB2 depend on its activity for proliferation, because treatment of these cells with ErbB2- specific antagonistic antibodies or kinase inhibitors blocks tumor cells in the G1 phase of the cell cycle. Intriguingly, loss of ErbB2 signaling is accompanied by a decrease in the phosphotyrosine content of ErbB3. On the basis of these results, it has been proposed that ErbB3 might be a partner for ErbB2 in promoting cellular transformation. To test this hypothesis and directly exam- ine the role of the ''kinase dead'' ErbB3, we specifically ablated its expression with a designer transcription factor (E3). By infection of ErbB2-overexpressing breast cancer cells with a retrovirus express- ing E3, we show that ErbB3 is an essential partner in the transfor- mation process. Loss of functional ErbB2 or ErbB3 has similar effects on cell proliferation and cell cycle regulators. Furthermore, expression of constitutively active protein kinase B rescues the proliferative block induced as a consequence of loss of ErbB2 or ErbB3 signaling. These results demonstrate that ErbB2 overexpres- sion and activity alone are insufficient to promote breast tumor cell division. Furthermore, we identify ErbB3's role, which is to couple active ErbB2 to the phosphatidylinositol 3-kinaseprotein kinase B pathway. Thus, the ErbB2ErbB3 dimer functions as an oncogenic unit to drive breast tumor cell proliferation.
917 citations
"Mechanisms of tumor regression and ..." refers background in this paper
...Indeed, HER-2/neu/HER-3 heterodimers or HER-2/neu homodimers may be more productive than EGFR/HER-2/neu heterodimers in activating the phosphatidylinositol 3-kinase/AKT pathway ( 36 , 37)....
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