Abstract 5170: The effect of vitamin K on aggressiveness, lipid metabolism and gene expression in triple-negative breast cancer cells

Abstract

Abstract Vitamin K is an essential cofactor in the γ-carboxylation of glutamate (Glu) to γ-carboxyglutamate (Gla), a post-translational modification mediated by the gamma-glutamyl carboxylase enzyme (GGCX) and vitamin K oxidoreductases (VKORC1 or VCORC1L1). All three of these genes are expressed in most breast cancer cell lines and The Cancer Genome Atlas (TCGA) data indicate that upregulation of these genes is associated with reduced survival in breast cancer patients. Since vitamin K is not typically present in cell culture media, γ-carboxylation is limited in vitro despite the presence of GGCX and VKORs. To determine the functional significance of the vitamin K pathway in breast cancer cells, we assessed the effect of vitamin K treatment on cell survival, migration and mammosphere formation. SUM159 and Hs578T cells were maintained in vitamin K1 (5 ug/mL) for at least 3 passages for all assays. Cells passaged with vitamin K produced γ-carboxylated proteins and exhibited increased cell survival after 72h, increased mammosphere formation after 8 days and increased cell migration after 48h compared to cells passaged in ethanol vehicle. Inhibition of VKORC1 with 2 uM warfarin decreased the production of γ-carboxylated proteins and reduced the effects of vitamin K on cell survival and migration but not on mammosphere formation. Microarray profiling and pathway analysis indicated upregulation of several known oncogenic pathways, including PI3K-AKT, VEGF-VEGFR, RANK-RANKL and JAK/STAT in vitamin K-treated SUM159 and Hs578T cells. Thus, γ-carboxylation of proteins driven by vitamin K might indirectly activate these pathways to enhance cell survival, cell migration and mammosphere formation. Additional pathways upregulated in vitamin K-treated cells included adipogenesis, fatty acid biosynthesis and lipid metabolism. We therefore examined lipid droplet formation in cells exposed to vitamin K using Bodipy assays. We detected an increase in lipid droplet formation after 72 hours of vitamin K treatment, which was inhibited by warfarin. Since aggressive breast cancers are often associated with accumulation of cytoplasmic lipid droplets, further studies on the mechanism by which vitamin K increases lipid accumulation are warranted. In conclusion, our data indicate that vitamin K enhances γ-carboxylation, breast cancer aggressiveness and lipid metabolism, suggesting that blocking the vitamin K pathway might be of therapeutic value for patients whose tumors express GGCX and VKORs. Citation Format: Leila Kokabee, Sarah Beaudin, JoEllen Welsh. The effect of vitamin K on aggressiveness, lipid metabolism and gene expression in triple-negative breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5170.