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Phosphorylated p-70S6K predicts tamoxifen resistance in postmenopausal breast cancer patients randomized between adjuvant tamoxifen versus no systemic treatment.

ABSTRACT: INTRODUCTION: Activation of the phosphatidylinositol-3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) pathways results in anti-estrogen resistance in vitro, but a biomarker with clinical validity to predict intrinsic resistance has not been identified. In metastatic breast cancer patients with previous exposure to endocrine therapy, the addition of a mammalian target of rapamycine (mTOR) inhibitor has been shown to be beneficial. Whether or not patients on adjuvant endocrine treatment might benefit from these drugs is currently unclear. A biomarker that predicts intrinsic resistance could potentially be used as companion diagnostic in this setting. We tested the clinical validity of different downstream-activated proteins in the PI3K and/or MAPK pathways to predict intrinsic tamoxifen resistance in postmenopausal primary breast cancer patients. METHODS: We recollected primary tumor tissue from patients who participated in a randomized trial of adjuvant tamoxifen (1-3 years) versus observation. After constructing a tissue micro-array, cores from 563 estrogen receptor ? positive were immunostained for p-AKT(Thr308), p-AKT(Ser473), p-mTOR, p-p706SK and p-ERK1/2. Cox proportional hazard models for recurrence free interval were used to assess hazard ratios and interactions between these markers and tamoxifen treatment efficacy. RESULTS: Interactions were identified between tamoxifen and p-AKT(Thr308), p-mTOR, p-p70S6K and p-ERK1/2. Applying a conservative level of significance, p-p70S6K remained significantly associated with tamoxifen resistance. Patients with p-p70S6K negative tumors derived significant benefit from tamoxifen (HR 0.24, P?

SUBMITTER: Beelen K

PROVIDER: S-EPMC3979131 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Phosphorylated p-70S6K predicts tamoxifen resistance in postmenopausal breast cancer patients randomized between adjuvant tamoxifen versus no systemic treatment.

Beelen Karin K Opdam Mark M Severson Tesa M TM Koornstra Rutger H T RH Vincent Andrew D AD Wesseling Jelle J Muris Jettie J JJ Berns Els M J J EM Vermorken Jan B JB van Diest Paul J PJ Linn Sabine C SC

Breast cancer research : BCR 20140121 1

<h4>Introduction</h4>Activation of the phosphatidylinositol-3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) pathways results in anti-estrogen resistance in vitro, but a biomarker with clinical validity to predict intrinsic resistance has not been identified. In metastatic breast cancer patients with previous exposure to endocrine therapy, the addition of a mammalian target of rapamycine (mTOR) inhibitor has been shown to be beneficial. Whether or not patients on adjuvant endocrine ...[more]

PMID: 24447434

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Project description:Purpose:Phosphorylated ribosomal S6 kinase 1 (pS6K1) is a major downstream regulator of the mammalian target of rapamycin (mTOR) pathway. Recent studies have addressed the role of S6K1 in adipogenesis. pS6K1 may affect the outcome of estrogen depletion therapy in patients with hormone-sensitive breast cancer due to its association with adipogenesis and increased local estrogen levels. This study aimed to investigate the potential of pS6K1 as a predictive marker of adjuvant aromatase inhibitor (AI) therapy outcome in postmenopausal or ovarian function-suppressed patients with hormone-sensitive breast cancer. Methods:Medical records were retrospectively reviewed in postmenopausal or ovarian function-suppressed patients with estrogen receptor-positive and node-positive primary breast cancer. pS6K1 expression status was scored on a scale from 0 (negative) to 3+ (positive) based on immunohistochemical analysis. Results:A total of 428 patients were eligible. The median follow-up duration was 44 months (range, 1-90). In patients with positive pS6K1 expression, AIs significantly improved disease-free survival (DFS) compared to selective estrogen receptor modulators (SERMs) (5 year-DFS: 83.5% vs. 50.7%, p = 0.016). However, there was no benefit of AIs on DFS in the pS6K1 negative group (5 year-DFS 87.6% vs. 91.4%, p = 0.630). On multivariate analysis, AI therapy remained a significant predictor for DFS in the pS6K1 positive group (hazard ratio, 0.39; 95% confidence interval, 0.16-0.96; p = 0.041). pS6K1 was more effective in predicting the benefit of AI therapy in patients with ages < 50 (p = 0.021) compared to those with ages ? 50 (p = 0.188). Conclusion:pS6K1 expression may predict AI therapy outcomes and serve as a potential predictive marker for adjuvant endocrine therapy in postmenopausal and ovarian function-suppressed patients with hormone-sensitive breast cancer. AIs may be more effective in patients with pS6K1 positive tumors, while SERM could be considered an alternative option for patients with pS6K1 negative tumors.

Project description:Inhibitors of the phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway can overcome endocrine resistance in estrogen receptor (ER) ?-positive breast cancer, but companion diagnostics indicating PI3K/AKT/mTOR activation and consequently endocrine resistance are lacking. PIK3CA mutations frequently occur in ER?-positive breast cancer and result in PI3K/AKT/mTOR activation in vitro. Nevertheless, the prognostic and treatment-predictive value of these mutations in ER?-positive breast cancer is contradictive. We tested the clinical validity of PIK3CA mutations and other canonic pathway drivers to predict intrinsic resistance to adjuvant tamoxifen. In addition, we tested the association between these drivers and downstream activated proteins.Primary tumors from 563 ER?-positive postmenopausal patients, randomized between adjuvant tamoxifen (1 to 3 years) versus observation were recollected. PIK3CA hotspot mutations in exon 9 and exon 20 were assessed with Sequenom Mass Spectometry. Immunohistochemistry was performed for human epidermal growth factor receptor 2 (HER2), phosphatase and tensin homolog (PTEN), and insulin-like growth factor 1 receptor (IGF-1R). We tested the association between these molecular alterations and downstream activated proteins (like phospho-protein kinase B (p-AKT), phospho-mammalian target of rapamycin (p-mTOR), p-ERK1/2, and p-p70S6K). Recurrence-free interval improvement with tamoxifen versus control was assessed according to the presence or absence of canonic pathway drivers, by using Cox proportional hazard models, including a test for interaction.PIK3CA mutations (both exon 9 and exon 20) were associated with low tumor grade. An enrichment of PIK3CA exon 20 mutations was observed in progesterone receptor- positive tumors. PIK3CA exon 20 mutations were not associated with downstream-activated proteins. No significant interaction between PIK3CA mutations or any of the other canonic pathway drivers and tamoxifen-treatment benefit was found.PIK3CA mutations do not have clinical validity to predict intrinsic resistance to adjuvant tamoxifen and may therefore be unsuitable as companion diagnostic for PI3K/AKT/mTOR inhibitors in ER?- positive, postmenopausal, early breast cancer patients.

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Phosphorylated p-70S6K predicts tamoxifen resistance in postmenopausal breast cancer patients randomized between adjuvant tamoxifen versus no systemic treatment.

Publications

Phosphorylated p-70S6K predicts tamoxifen resistance in postmenopausal breast cancer patients randomized between adjuvant tamoxifen versus no systemic treatment.

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