Interestingly, the existence of mGluR4 has been documented in medulloblastoma arising from the cerebellum of children (Iacovelli et al., 2006) and several non-neural malignant tumors, such as colorectal carcinoma (Yoo et al., 2004; Chang et al., 2005) and osteosarcoma (Yang et al., 2014). This evidence concerns the gene GRM4 and osteosarcoma.