Abstract 1903: Up-regulation of vitamin B1 homeostasis genes in breast cancer.

Abstract

Abstract Malignant cells exhibit alterations in metabolic enzymes requiring an adequate supply of cofactors to support enzymatic activity. In particular, Vitamin B1 (thiamine) is an important component of cellular growth and metabolism within all cells, functioning as an essential enzyme cofactor in key metabolic pathways within in the glycolytic network. Intracellular availability of thiamine is facilitated by the activity of thiamine transporters and the conversion of thiamine to the active coenzyme, thiamine pyrophosphate (TPP) by thiamine pyrophosphokinase (TPK1). Therefore, the objective was to establish if the cellular determinants regulating thiamine homeostasis differ between breast cancer and normal breast epithelia. This work will aid in linking the metabolic phenotype of cancer cells with the adaptive regulation of thiamine homeostasis. This may provide a molecular basis for dietary interventions and new therapeutic targets directed towards cancer cell metabolism. Methods: cDNA arrays of breast cancer and normal breast tissues were employed to determine expression of SLC19A2, SLC19A3, SLC25A19 and TPK-1. Western blotting was used to determine whole cell protein expression. To test the extent of cell surface localization of the transporters, cell surface proteins were biotinylated and run on Western Blot. Transport assays were used to quantify thiamine transport and free thiamine levels in breast cancer cell lines compared to human mammary epithelial cells (HMEC). Results: SLC19A2, SLC25A19 and TPK-1were found to be significantly up-regulated in clinical tissues and breast cancer cell lines 6.48 (P=0.0013), 5.97 (P=0.0003), and 2.33 (P=0.0063) folds, respectively. Additionally, thiamine transporters THTR1 and THTR2 exhibited different cellular localization and expression depending on the ER status of the cancer cell. The increase in thiamine homeostasis genes correlated with an increase in intracellular free thiamine levels but not with the coenzyme TPP. Conclusions: Overall, these findings demonstrate an adaptive response by breast cancer cells to bolster an increase in the cellular availability of thiamine. Citation Format: Jason Zastre, Brad Hanberry, Rebecca Sweet, Cary McGinnis, Kristen Venuti, Michael Bartlett, Raj Govindarajan. Up-regulation of vitamin B1 homeostasis genes in breast cancer. [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 1903. doi:10.1158/1538-7445.AM2013-1903