Evaluation of cholecalciferol/vitamin d3 treatment in colon cancer cells through autophagy and endoplasmic reticulum stress

Vitamin D is the precursor to cholecalciferol, a powerful steroid hormone with widespread effects on the body. Vitamin D, which also has an anticancer effect, can not show this effect due to insufficient exposure to sunlight and various reasons that can be seen in individuals with cancer. In addition, some cancer patients are faced with vitamin D deficiency. Cholecalciferol is the most important form of vitamin D that nourishes the body. Studies have shown that cholecalciferol inhibits proliferation, migration, invasiveness and angiogenesis of various cancer cells. In addition, cholecalciferol positively affects the intestinal microbiota by regulating the biology of immune cells in the intestine. In this study, the effect of cholecalciferol treatment on autophagy and endoplasmic reticulum (ER) stress in colon cancer cells was evaluated. The cytotoxic effect of cholecalciferol on HT-29 and HCT 116 cells was evaluated by XTT analysis. Considering cytotoxicity results, cells were treated with 150 and 250 µM cholecalciferol for 48 hours in subsequent analyzes. Then, RNA was isolated from the control and dose groups, cDNA was synthesized, and expression levels of genes associated with apoptosis, ER stress and autophagy were analyzed by qRT-PCR. The effect of cholecalciferol on colony-forming abilities in colon cancer cells was evaluated by colony formation analysis. In addition, the effect of cholecalciferol on autophagy and ER stress was investigated using the fluorometric-based autophagy kit and the GRP78/BiP ELISA kit. According to the qRT-PCR results, cholecalciferol treatment increased the expression of genes associated with apoptosis and ER stress, while decreasing the expression of autophagy-related genes in colon cancer cells. Similarly, while autophagy decreased after cholecalciferol treatment, the amount of ER stress marker GRP78/BiP increased. In addition, cholecalciferol significantly reduced the colony-forming ability of colon cancer cells. When all the results are evaluated together, it is thought that cholecalciferol causes an anticancer effect by suppressing autophagy and increasing apoptosis with ER stress in colon cancer cells