1,25 Dihydroxyvitamin D regulation of glucose metabolism via pyruvate carboxylase in MCF10A‐ras human breast epithelial cells (261.7)

Abstract

Previous studies from our laboratory, employing Harvey‐ras oncogene transfected MCF10A (ras) cells, a model of early breast cancer progression, show that 1,25 dihydroxyvitamin D (1,25D) regulates glucose metabolism with reduced glycolysis and lactate production, and reduced flux to the TCA cycle in ras cells. Further, 1,25D reduced cell “glucose addiction”, a characteristic of cells in progression to cancer. In the current study, glucose restriction from 5 mM to 1 mM increased G1 cell cycle arrest (flow cytometry) in ras cells (62% vs. 71%, respectively). shRNA knockdown of pyruvate carboxylase (PC), a key enzyme for the anaplerosis of the TCA cycle, prevented the increase in G1 cell cycle arrest at 1 mM glucose in ras cells, which was a similar effect to 1,25D. However, 1,25D treatment in addition to PC knockdown had no effect in preventing the increase in G1 cell cycle arrest at 1 mM glucose, suggesting PC may mediate the effect of 1,25D. 1,25D inhibited PC mRNA (45%) and protein (65%) expression starting at 24 and 48 hours, respectively. Consistent with potential transcriptional regulation of the PC gene by 1,25D, six consensus sequences to the negative vitamin D responsive element (nVDRE) were found on PC gene promoter. Therefore, negative regulation of the PC gene is part of the mechanism by which 1,25D regulates glucose metabolism and prevents early breast cancer progression.Grant Funding Source: Supported by NIH R25CA128770 and NCI CCSG CA23168