5-HT2B promotes tumors in the late stage of CAC. (A) Schematic of inducible Htr2b deletion in the AOM/DSS model. Villin-CreERT2 activation was mediated by tamoxifen injection after the tumors had formed. (B) Immunohistochemical analysis of 5-HT in the colonic polyp tissues of WT and Htr2bΔIEC-ER mice. (C) The colonic polyp multiplicity and polyp load in WT and Htr2bΔIEC-ER mice given AOM/DSS treatment (n = 7-8). (D) Immunohistochemical analysis of Ki-67 and cleaved caspase-3 in colonic polyp tissues of WT and Htr2bΔIEC-ER mice given AOM/DSS treatment. (E) The percentage of Ki-67 and cleaved caspase-3 positive cells in colonic polyp tissues of WT and Htr2bΔIEC-ER mice (n = 5). (F) Immunohistochemical analysis of p-STAT3 in the colonic polyp tissues of WT and Htr2bΔIEC-ER mice. (G) The percentage of p-STAT3-positive cells in colonic polyp tissues of WT and Htr2bΔIEC-ER mice (n = 5). Scale bars, 100 μm. Error bars represent the mean ± SEM. ns: not significant, *P < 0.05, **P < 0.01; unpaired Student's t-test (C, E, G).