PTGS2 and colorectal carcinoma: In addition to the above, the expression levels of inflammatory factors VEGF, COX-2, IL-6, and CDH17 in the colonic tissues of mice in the CRC + Fn and CRC + Fn + Cys groups (Fig. 5h) were significantly higher than those of the control group, and the levels of inflammatory factors in the colonic tissues of mice in the CRC + Fn + Cys group were significantly higher than those in the CRC + Fn group, which again verified that Fn and/or its product H2S can promote the development of CRC.