Abstract 1047: Effect of 1,25-Dihydroxyvitamin D in regulating glutamic-oxaloacetic transaminase 1 (GOT1) and redox balance during breast cancer progression

Abstract

Breast cancer is the second most common cancer among women in the US. The active form of vitamin D, 1α,25 dihydroxyvitamin D (1,25(OH)2D), is proposed to inhibit cellular processes that may prevent breast cancer. Possible pro-oxidative effects of 1,25(OH)2D in breast cancer cells which may selectively promote cell death have been proposed. Glutamic-oxaloacetic transaminase 1 (GOT1) is an essential transaminase in glutamine metabolism. GOT1 converts aspartate into oxaloacetate in the cytoplasm, which is then subsequently converted to malate and pyruvate. NADPH is produced during the last step of this process and increased NADPH/NADP+ ratio has the potential to maintain cellular redox balance. Therefore, it is of interest to study 1,25(OH)2D regulation of GOT1 during cancer progression to understand the role of vitamin D in regulating oxidative stress as a mechanism to prevent breast cancer. We employed untransformed MCF10A human breast epithelial cells (MCF10A), as well as Harvey ras-oncogene or ErbB2 (HER-2/neu) oncogene transformed cells (MCF10A-ras and MCF10A-ErbB2) as cell models for early cancer progression. Results showed that 1,25(OH)2D significantly decreased GOT1 mRNA expression at 48 hours in MCF10A-ras cells and MCF10A-ErbB2 cells by 35 ± 8.8% and 49 ± 10%, respectively, and GOT1 protein expression at 72 hours by 51 ± 4.9% and 51 ± 16%, respectively. The susceptibility of MCF10A-ras cells to hydrogen peroxide induced cell death was significantly increased by 1,25(OH)2D, as determined by measuring viable cell number using MTT assay. We further showed that 96-hour 1,25(OH)2D treatment significantly reduced cellular NADPH/NADP+ ratio by 30 ± 2.8% and GSH/GSSG ratio by 34 ± 2.7% in MCF10A-ras cells. Collectively, these results support that 1,25(OH)2D inhibits GOT1 expression and has pro-oxidative effects in oncogene transformed MCF10A cell lines, which may contribute to its role in preventing breast cancer development. Citation Format: Xuanzhu Zhou, Tomasz Wilmanski, Dorothy Teegarden. Effect of 1,25-Dihydroxyvitamin D in regulating glutamic-oxaloacetic transaminase 1 (GOT1) and redox balance during breast cancer progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1047.