Abstract 5747: Elucidating the mechanisms by which Snail transcription factor promotes resistance to chemotherapy in breast carcinomas

Abstract

Abstract Snail (Snail1) is a zinc finger transcription factor that can induce EMT and is expressed at high levels in tumors. Maspin is a potential tumor suppressor, whose expression is lost as breast and prostate tumors progress during EMT. Maspin can be transcriptionally repressed by androgen receptor (AR) in prostate cancer cells. We hypothesized that overexpression of Snail will inhibit maspin expression and confer resistance to chemotherapy. Initially, we examined the expression of Snail and maspin in a panel of breast epithelial and breast cancer cells by RT-PCR and Western blot analysis. Preliminary results suggest that breast cancer cells express variable levels of Snail that is higher in breast cancer cells than in the normal MCF10A cells. We then utilized MCF-7 cells transfected stably with an empty Neo vector (MCF-7 Neo) or constitutively active Snail cDNA (MCF-7 Snail) that have been shown previously to represent an EMT model, and examined maspin, estrogen receptor alpha (ER-α) and AR levels by western blot analysis. MCF-7 Snail cells had upregulated levels of Snail and lower levels of maspin, ER-α and AR, as compared to MCF-7 Neo. MCF-7 Neo and MCF-7 Snail cells were also xenografted into nude mice and tissue sections stained immunohistochemically for Snail, maspin, and ER-α. Tumor volumes of MCF-7 Snail tumor xenografts were significantly larger than the MCF-7 Neo xenografts. MCF-7 Snail tissue sections expressed higher levels of Snail and lower levels of maspin and ER-α as compared to MCF-7 Neo sections. MCF-7 Neo and MCF-7 Snail cells were also treated with estradiol (E2, 0.01uM), tamoxifen (TAM, 10uM), and docetaxel (DOX, 1uM) individually; and in combination with E2 plus TAM and TAM plus DOX for periods of 24h and 72h to analyze changes in cell morphology and EMT marker expression. No effect on cell morphology or cell death was observed in MCF-7 Snail cells after TAM treatments, whereas TAM induced cell death in MCF-7 Neo. Expression of Snail was increased with E2 treatments and decreased with TAM, DOX, and combination treatments in MCF-7 Neo and MCF-7 Snail. AR expression decreased further in MCF-7 Snail cells and MCF-7 Neo following treatments with TAM and DOX. Overall, the Snail overexpression appears to promote resistance to TAM and DOX chemotherapeutic agents. The mechanism of Snail-regulated EMT needs to be investigated further to determine changes in breast cancer progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5747. doi:1538-7445.AM2012-5747