Whereas ethanol exposure induced significantly increased apoptosis of predominantly MMR-proficient normal-appearing colonic epithelia in ethanol-treated compared with water-treated induced Aldh1b1flox/flox Msh2-LS and Aldh1b1−/− Msh2-LS mice, almost no cCas3+ apoptotic bodies were observed in ethanol-treated induced Aldh1b1flox/flox Msh2-LS and Aldh1b1−/− Msh2-LS murine dMMR colonic adenomas, indicating almost complete failure of acetaldehyde-mediated DNA damage to induce apoptosis in dMMR colonic tumours. This evidence concerns the gene MSH2 and colonic neoplasm.