Venkatapoorna, Chandra Mohan Kurapaty

Abstract Fatty acid synthase (FASN), the key enzyme in de novo lipogenesis, is significantly upregulated and activated in many carcinomas, including breast cancer. Pharmacological inhibition of FASN induces apoptosis of FASN expressing cancer cells. However, the mechanism is still unclear. Inhibition of FASN in breast cancer cells induces a dose dependent increase in apoptotic cell death with a concomitant upregulation of the pro-apoptotic BH3-only proteins Noxa, Bim and Puma (mRNA and protein). Blockage of the BH3-only protein expression using specific small interfering ribonucleic acid (siRNA), significantly diminishes the apoptotic effect induced by the inhibition of FASN. Moreover, addition of palmitate, the end product of FASN, protects the cells from the proapoptotic effects of FASN inhibition by suppressing expression of Noxa, Bim and Puma. These data indicate that Noxa, Bim and Puma are essential for the apoptotic effect induced by the inhibition of FASN. Combination therapeutic regimens have received growing attention for the possibility of higher efficacy with reduced toxicity. Thus, we investigated the combinatorial effect of pharmacological inhibition of FASN and Bcl-2/Bcl-xL. While a small molecule Bcl-2/Bcl-xL inhibitor alone did not induce apoptosis, co-treatment of the small molecule Bcl-2/Bcl-xL inhibitor with a synthetic FASN inhibitor significantly surpassed the apoptotic effect of the synthetic FASN inhibitor alone. Accordingly, combined treatment of a FASN inhibitors and Bcl-2/Bcl-xL antagonists represents a new rational combination that merits further consideration in FASN overexpressing tumors. Citation Format: Chandra Mohan Kurapaty Venkatapoorna, Ingrid Espinoza, Scott H Kaufmann, Ruth Lupu. Pharmacological inhibition of fatty acid synthase regulates BH3-only proteins and sensitizes breast cancer cells to a small molecule Bcl-2/Bcl-xL inhibitor to induce apoptosis. [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 1737. doi:10.1158/1538-7445.AM2013-1737 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract Background: Cyr61, also known as CCN1, is a survival and pro-angiogenic factor overexpressed in invasive breast tumors that promotes tumorigenicity. We investigated whether Cyr61 plays important roles in breast cancer and evaluated its potential role as a chemotherapeutical target. Methods: We analyzed Cyr61 expression in a tissue microarray from breast cancer patients consisting of primary breast carcinomas and recurrences. Cyr61 was silenced in the metastatic MDA-MB-231 cells using a Cyr61-specific short hairpin RNA (Cyr61-shRNA). The effect of Cyr61 silencing on anchorage dependent- and independent growth, migration and invasiveness was characterized in vitro. The mechanism by which Cyr61 mediates the proliferation effects was investigated. The effect of Cyr61 in tumor growth was investigated in a subcutaneous orthotopic tumor xenograft model and the histological and immunohistochemical analysis ware performed. All statistical tests were two-sided. Results: Cyr61 is highly expressed in about 47% of the metastatic breast cancer patients analyzed. The expression is higher in the recurrences than in the primary tumors. Silencing Cyr61 inhibits cell proliferation, prevents anchorage-dependent and -independent growth, and suppresses the invasive potential of the cells by inhibiting migration in vitro. We also found that silencing Cyr61 decreases the expression of its own receptor αvβ3, and decreases its signaling activities. Remarkably, the in vivo studies showed that after silencing Cyr61 the tumor burden is significantly decreased and there is poor vascularized compared to control tumors. Conclusions: Our findings provide the proof of concept that Cyr61 is a key promoter of breast cancer tumorigenicity. It should be considered as a potential target for developing therapies to breast cancers patients that overexpress Cyr61. 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 1846. doi:1538-7445.AM2012-1846