Specifically, the high expression of TGF-β1 induced by MC-LR exposure in M2 macrophages may stimulate glycolysis and L-lactate production in CRC cells, leading to an acidic microenvironment that activates cathepsin D and enhances the cleavage of CST3, ultimately leading to reduced CST3 expression. Here, CST3 is linked to colorectal carcinoma.