Modulation of VDR and Cell Cycle-Related Proteins by Vitamin D in Normal Pancreatic Cells and Poorly Differentiated Metastatic Pancreatic Cancer Cells.

Many in vitro studies support the general idea that vitamin D plays a protective role against cancer. Increased doses of vitamin D dietary supplements have been widely used for the potential anticancer benefits of vitamin D. However, despite substantial epidemiological research, there are no clear conclusive data to support the use of vitamin D as a cancer preventive or treatment agent. In the, herein, reported study, we checked the effects of 1,25-dihydroxyvitamin D-3 concentrations on the expression level of the vitamin D receptor (VDR) and cell cycle-related proteins CDKN1A (p21) and CDK1 in pancreatic cells and Panc-1 pancreatic cancer (PC) cells. We found that VDR, CDKN1A, and CDK1 were upregulated by an increase in 1,25-dihydroxyvitamin D-3 concentration in normal pancreatic cells but not in the advanced cancer cell line Panc-1 from poorly differentiated metastatic PC cells. A further increase in 1,25-dihydroxyvitamin D-3 concentration above the physiological range significantly downregulated the expression of VDR, indicating that VDR is modulated by VDR levels to maintain normal functioning during dramatic variations in vitamin D concentration. By increasing the level of cell cycle inhibitory and promoting proteins p21 and CDK1, vitamin D theoretically has both preventive and promoting effects on pancreatic cell division.