Colorectal cancer (CRC) is one of the most common malignancies, and effective treatment and prevention methods are lacking. Sodium butyrate (NaB) is a short-chain fatty acid produced by intestinal microbial fermentation of dietary fiber. It has been shown to be effective in inhibiting CRC, but the mechanism is not known.
Methods: Human normal intestinal epithelial cell line FHT and colorectal tumor cell line HCT-116 were treated with NaB alone or in combination with different programmed cell death inhibitors. Cell activity was then assessed with MTT assays and PI staining; ferroptosis with Fe2+, glutathione (GSH), and lipid peroxidation assays; signaling pathway screening with PCR arrays; and CD44, SCL7A11, and GPX4 expression with Western blotting. A CD44-overexpressing HCT-116 cell line was constructed to determine the effect of the overexpression of CD44 on NaB-induced ferroptosis. The synergistic effect of co-treatment with NaB and Erastin was assessed by isobolographic analysis.
Results: NaB induced apoptosis and ferroptosis in HCT-116 cells but only induced low-level apoptosis in FHC cells. Moreover, NaB significantly increased intracellular Fe2+ and promoted GSH depletion and lipid peroxidation in HCT-116 cells. Ferroptosis-related qPCR array analysis identified CD44/SLC7A11 as a potential effector molecular of NaB-induced ferroptosis. NaB significantly inhibited the expression of CD44 and SLC7A11 in mouse CRC tissues. A CD44 overexpressed HCT-116 cell line was used to verify that CD44/SLC7A11 was a key signaling pathway that NaB-induced GSH depletion, lipid peroxidation accumulation, and ferroptosis in HCT-116 cells. Examination of whether NaB can increase the effect of ferroptosis agents showed that NaB, in combination with Erastin, a ferroptosis inducer, further promoted HCT-116 cell death and increased changes of ferroptosis markers.
Conclusions: Our results suggest that NaB induces ferroptosis in CRC cells through the CD44/SLC7A11 signaling pathway and has synergistic effects with Erastin. These results may provide new insights into CRC prevention and the combined use of NaB and ferroptosis-inducing agents.
Keywords: CD44; CRC; SLC7A11; ferroptosis; sodium butyrate.