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Abstract Background Estrogen receptor positive (ER+) breast cancers (BC) are heterogeneous with regard to their clinical behavior and response to therapies. The ER is currently the best predictor of response to the anti-estrogen agent tamoxifen, yet up to 30–40% of ER+BC will relapse despite tamoxifen treatment. New prognostic biomarkers and further biological understanding of tamoxifen resistance are required. We used gene expression profiling to develop an outcome-based predictor using a training set of 255 ER+ BC samples from women treated with adjuvant tamoxifen monotherapy. We used clusters of highly correlated genes to develop our predictor to facilitate both signature stability and biological interpretation. Independent validation was performed using 362 tamoxifen-treated ER+ BC samples obtained from multiple institutions and treated with tamoxifen only in the adjuvant and metastatic settings. Results We developed a gene classifier consisting of 181 genes belonging to 13 biological clusters. In the independent set of adjuvantly-treated samples, it was able to define two distinct prognostic groups (HR 2.01 95%CI: 1.29–3.13; p = 0.002). Six of the 13 gene clusters represented pathways involved in cell cycle and proliferation. In 112 metastatic breast cancer patients treated with tamoxifen, one of the classifier components suggesting a cellular inflammatory mechanism was significantly predictive of response. Conclusion We have developed a gene classifier that can predict clinical outcome in tamoxifen-treated ER+ BC patients. Whilst our study emphasizes the important role of proliferation genes in prognosis, our approach proposes other genes and pathways that may elucidate further mechanisms that influence clinical outcome and prediction of response to tamoxifen.

This study aimed to define a gene expression profile associated with response to anti-estrogen treatment in estrogen receptor alpha (ERalpha)-positive breast cancer from elderly patients and to identify possible candidate genes associated with resistance by detecting those modulated by treatment. Using cDNA microarrays containing 16 702 unique clones, 21 pre-treatment and 11 paired post-treatment samples collected in a neo-adjuvant toremifene trial on elderly patients with operable and locally advanced ERalpha-positive breast cancer were profiled. Gene expression profiles generated from pre-treatment samples were correlated with treatment-induced tumor shrinkage and compared with those obtained from post-treatment paired samples to define genes differentially modulated following anti-estrogen treatment. Correlation analysis on 21 pre-treatment samples highlighted 53 genes significantly related to treatment response (P<0.001). Genes involved in cell cycle and proliferation were more frequently upregulated in responders compared with non-responders. Class comparison analysis identified 101 genes significantly modulated independently of treatment response; 82 genes were modulated in non-responders, whereas only 8 genes were differently expressed after treatment in responders. Gene expression profiles appear to be more frequently modulated by anti-estrogen treatment in non-responding patients and may harbor interesting genes possibly involved in anti-estrogen resistance, including clusterin, MAPK6, and MMP2. This concept was corroborated by in vitro studies showing that silencing of CLU restored toremifene sensitivity in the ER anti-estrogen-resistant breast cancer cell line T47D. Integration between neo-adjuvant therapy and transcriptional profiling has therefore the potential to identify therapeutic targets to be challenged for overcoming treatment resistance.

Epithelial ovarian cancer (EOC) is the gynecological disease with the highest death rate. We applied an automatic class discovery procedure based on gene expression profiling to stages III-IV tumors to search for molecular signatures associated with the biological properties and progression of EOC. Using a complementary DNA microarray containing 4451 cancer-related, sequence-verified features, we identified a subset of EOC characterized by the expression of numerous genes related to the extracellular matrix (ECM) and its remodeling, along with elements of the fibroblast growth factor 2 (FGF2) signaling pathway. A total of 10 genes were validated by quantitative real-time polymerase chain reaction, and coexpression of FGF2 and fibroblast growth factor receptor 4 in tumor cells was revealed by immunohistochemistry, confirming the reliability of gene expression by cDNA microarray. Since the functional relationships among these genes clearly suggested involvement of the identified molecular signature in processes related to epithelial-stromal interactions and/or epithelial-mesenchymal cellular plasticity, we applied supervised learning analysis on ovarian-derived cell lines showing distinct cellular phenotypes in culture. This procedure enabled construction of a gene classifier able to discriminate mesenchymal-like from epithelial-like cells. Genes overexpressed in mesenchymal-like cells proved to match the FGF2 signaling and ECM molecular signature, as identified by unsupervised class discovery on advanced tumor samples. In vitro functional analysis of the cell plasticity classifier was carried out using two isogenic and immortalized cell lines derived from ovarian surface epithelium and displaying mesenchymal and epithelial morphology, respectively. The results indicated the autocrine, but not intracrine stimulation of mesenchymal conversion and cohort/scatter migration of cells by FGF2, suggesting a central role for FGF2 signaling in the maintenance of cellular plasticity of ovary-derived cells throughout the carcinogenesis process. These findings raise mechanistic hypotheses on EOC pathogenesis and progression that might provide a rational underpinning for new therapeutic modalities.