There is evidence for clinical significance of the expression of these glutamate receptors; for example the expression of mGlu5 in oral squamous cell carcinoma [91] has been shown to correlate with increased survival of the patients while an inverse correlation has been noted between the expression of mGlu4 in medullablastoma and increasing tumor severity and recurrence after therapy [87]. Here, GRM5 is linked to oral cavity squamous cell carcinoma.