MSH2 and colorectal carcinoma: The study by Valeri et al. shows that the microRNA-21 (miR-21) downregulates hMSH2, and miR-21 overexpression reduces the therapeutic efficacy of 5-FU in a CRC xenograft model, suggesting that the downregulation of MSH2 with miR-21 overexpression may be an important indicator of therapeutic efficacy in CRC [110].