Hollister, Beth

Abstract Introduction: A significant number of histologically triple negative breast cancer (TNBC) cells express substantial estrogen receptor (ER) mRNA but do not express ER protein as a result of rapid proteolytic degradation. Here we assessed whether proteasome inhibitors could sensitize such cells to tamoxifen-induced growth suppression. Methods: Data from the Katzenellenbogen laboratory elegantly demonstrate that in high ER mRNA MDA-MB-468 cells, ER protein is rapidly degraded via proteosomal degradation (Bhatt et al. MCB, 2012).Utilizing established human TNBC cell lines that express high ER mRNA (BT-20, MDA-MB-468, and newly established human TNBC cell lines from our laboratory MCJB2 and MCJB11), we defined a therapeutic strategy using the proteasome inhibitor carfilzomib in combination with the antiestrogen tamoxifen that demonstrates antitumor synergy. Results: We found that administration of carfilzomib in TNBC cell lines with high ER mRNA restored ER protein expression, and that combining this treatment with tamoxifen treatment led to enhanced growth suppression. We found that the TNBC MDA-MB-231 cells, which express no ER mRNA, show some growth suppression, but that tamoxifen provided no further growth suppression with these cells. We have previously shown that combined epigenetic therapy [methyltransferase inhibitor (decitabine) plus a histone deacetylase inhibitor (HDACi; romidepsin)] provided antitumor synergy in MDA-MB-231 cells via upregulation of the soluble Wnt suppressor, secreted frizzled protein 1 (sFRP1; Cooper et al. CCR, 2012). In addition, we show that this epigenetic therapy restores silenced ER mRNA and protein levels in MDA-MB-231 cells, and that combination of this epigenetic therapy with tamoxifen in MDA-MB-231 cells led to enhanced growth suppression by tamoxifen. We are currently testing these therapeutic strategies in vivo using established TNBC cell lines and our newly developed patient derived xenograft (PDX) mouse models that express either ERhigh or ERlow mRNA. Conclusions: If validated in animal models, we propose that ER mRNA expression level in TNBC patients could guide therapeutic choice, whereby, ERlow mRNA TNBC tumors could respond to epigenetic therapy followed by antiestrogen while ERhigh mRNA TNBC tumors could respond to a proteosome inhibitor followed by antiestrogen therapy. These results identify a novel epigenetic biomarker as predictive of therapeutic response. Citation Format: Christina A. von Roemeling, Laura A. Marlow, James Miller, Adam Mathias, Louis Dawson, Steadman Harrison, Beth A. Hollister, Derek C. Radisky, John Alton Copland. Estrogen receptor mRNA-directed therapy for triple-negative breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-95. doi:10.1158/1538-7445.AM2014-LB-95

Abstract Introduction: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of RCC, which is the most prevalent kidney cancer among adults. Of the patients who develop this disease, over 1/3 will already present with advanced or metastatic disease during initial diagnosis due to the lack of symptoms in early stages. RCC demonstrates considerable resistance to radiation and traditional chemotherapeutics. Despite advances in the development of targeted anti-cancer treatments, no current drug therapy leads to significant improvement in long term survival in patients with advanced disease with the rare exception of those who respond to immunotherapy. Additionally, patients inevitably develop drug resistance. Therefore new molecular targets for therapy are sorely needed. Our group has identified stearoyl coA desaturase (SCD1) as a novel molecular target in ccRCC. We examined its role in tumor cell growth and viability in vitro and in vivo independently as well as in combination with current FDA approved regimens. Methods: Patient normal and ccRCC tissue samples and cell lines were examined for SCD1 expression. Genetic knockdown models and targeted inhibition of SCD1 through use of a small molecule inhibitor were analyzed for growth, apoptosis, and alterations in gene expression using gene array analysis. Therapeutic models of synergy were evaluated utilizing pharmacologic inhibition of SCD1 with the tyrosine kinase inhibitors (TKI) sunitinib and pazopanib, and the mTOR inhibitor temsirolimus. Results: Our studies identify increased SCD1 expression in all stages of ccRCC. Both genetic knockdown and pharmacologic inhibition of SCD1 decrease tumor cell proliferation and induce apoptosis in vitro and in vivo. Upon gene array, quantitative real-time PCR, and protein analysis of SCDi treated or SCD1 lentiviral knockdown samples, induction of endoplasmic reticulum (ER) stress response signaling was observed, providing mechanistic insight for SCD1 activity in ccRCC. Furthermore, combinatorial application of SCDi with temsirolimus synergistically inhibits tumor growth in vitro and in vivo. Conclusions: Increased SCD1 expression supports ccRCC viability and therefore we propose it as a novel molecular target for therapy either independently or in combination with an mTOR inhibitor for patients whose disease cannot be remedied with surgical intervention, such as in cases of advanced or metastatic disease. These findings support the further evaluation of targeting SCD1 as an anti-cancer strategy in a phase I clinical trial. Citation Format: Christina A. von Roemeling, Laura Marlow, Thomas Caulfield, Kevin Wu, Winston Tan, Han Tun, John A. Copland, Adam Mathias, Chuck Harrison, Louis Dawson, Beth Hollister. Stearoyl-CoA desaturase 1 is a novel molecular therapeutic target for clear cell renal cell carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-210. doi:10.1158/1538-7445.AM2013-LB-210