Furthermore, the weak or the absence of the expression of mGluR1 and mGluR5 in normal cells compared with cancer cells allow making the hypothesis that these receptors are not involved in the onset of cancer, rather, the activation of mGluR1 and mGluR5 might occur in the cancer cell or in a cell undergoing a malignant transformation which can contribute to the progression of cancer and the malignant behavior cancer cells. The gene discussed is GRM5; the disease is cancer.