In colon cancer, high expression of mGluR4 is related to poor prognosis [142], while the activation of mGluR4 protects cells from 5-fluorouracil (5-FU) toxicity; conversely, in the same model, reduced mGluR4 expression or its drug-induced inactivation lead to cell death [136]. This evidence concerns the gene GRM4 and colonic neoplasm.