GRM1 and metastatic prostate carcinoma: While analysis of The Cancer Genome Atlas dataset has revealed there is an interesting interaction between PTEN status with GRM1 in dictating prognostic outcomes (Supplementary Fig. S8), further work including clinical trials will be required to link this prognostic effect to a possible stratification strategy to achieve better clinical outcome when PI3K/mTOR inhibition is applied to treat patients with metastatic prostate cancer.