The Ferroptosis Induced by Palmitic Acid via CD36 Activating ER Stress to Break Calcium-Iron Balance in Colon Cancer Cells.

PURPOSE/OBJECTIVE(S): There have been numerous studies to date on the treatment of tumors by saturated fatty acids. But the role that ferroptosis plays in this is not clear. Palmitic acid (PA) is a common saturated fatty acid with huge application prospects for inducing tumor cell ferroptosis.

MATERIALS/METHODS: In vivo and in vitro experiments were performed to verify changes in cell proliferation, apoptosis and ferroptosis after PA treatment of colon cancer cells. Changes in ROS, lipid peroxidation, ferric ions, calcium ions, endoplasmic reticulum (ER) stress, endocytosis recycling trafficking of transferrin after PA treatment of colon cancer cells were detected. Further using necrosis inhibitor (Necrostatin-1), apoptosis inhibitor (Z-VAD-FMK), autophagy inhibitor (CQ), iron death inhibitor (Fer-1), calcium / ferric ion chelator (BAPTA-AM / DFP), iron supplement (FAC), calcium ion agonist (thapsigargin) for positive and negative verification. The association of CD36 expression and patient prognosis in colon cancer patients was subsequently evaluated by bioinformatics analysis. Detect the difference of CD36 expression in different colon cancer cells induced by PA, and further knock down or over express CD36 to explore the change of sensitivity to PA induced ferroptosis.

RESULTS: PA inhibited colon cancer cell viability in vitro and in vivo, in conjunction with an accumulation of ROS and lipid peroxidation. The ferroptosis inhibitor Ferrostatin-1 but not Z-VAD-FMK, Necrostatin-1, or CQ rescued the cell death induced by PA. Subsequently, we verified that PA-induced ferroptosis through excess iron as cell death was inhibited by iron chelator deferiprone (DFP) but exacerbated by a supplement of ferric ammonium citrate (FAC). Mechanistically, PA leads to endoplasmic reticulum calcium release by inducing ER stress, and the increase of cytosolic calcium level positively regulates the endocytosis recycling transport of transferrin to promote the increase of intracellular iron content. Furthermore, we observed that cells with high expression of CD36 were more vulnerable to PA-induced ferroptosis. Knocking down the expression of CD36 can inhibit the sensitivity of colon cancer cells to PA induced ferroptosis, and vice versa.

CONCLUSION: In general, we report for the first time that PA can selectively induce ferroptosis in colon cancer cells with high expression of CD36 by activating ER stress/ER calcium release/transferrin-dependent ferroptosis. This provides a new strategy and basis for the precise treatment of tumors.