Silymarin Effect on Mitophagy Pathway in the Human Colon Cancer HT-29 Cells

The anti-cancer effects of silymarin have been reported in several studies. However, the mechanism of its action in colon cancer cells is not well understood. This study aimed to investigate the effect of silymarin on the mitophagy pathway and the formation of reactive oxygen species (ROS) in human colon cancer cells (HT-29).

HT-29 cancer cells and NIH-3T3 non-cancer cells were exposed to 0 (control), 25, 50, and 100 μg/ml of silymarin for 48 h. Cell viability, ROS level, mitochondrial membrane potential (MMP), and expression of important mitophagy-related genes including Pink1 (PTEN-induced putative kinase protein 1) and Parkin were examined to evaluate the effects of silymarin.

Silymarin significantly reduced the viability percentage of the HT-29 cells depending on the concentration (P<0.05). It also significantly decreased MMP in a concentration-dependent manner while significantly increased ROS formation in the HT-29 cells (P<0.05). In addition, silymarin significantly increased the expression of Pink1 and Parkin genes in a concentration-dependent manner (P<0.05). Concentration of 100 μg/ml of silymarin had the greatest effect on reducing viability and MMP, as well as increasing ROS levels and expression of mitophagy-related genes (P<0.001). Silymarin did not cause significant changes in the viability percentage, ROS level, and MMP of the NIH-3T3 non-cancerous cells at different concentrations.

According to the results, silymarin increases the level of ROS by decreasing MMP, thereby inducing mitophagy through the Pink1/Parkin signaling pathway in the HT-29 cells.