Similar to GRM8 role in squamous cell lung carcinoma, we found that GRM8 overexpression in breast cancer HCC1937 cells significantly enhanced cell proliferation, migration, and invasion and repressed cell apoptosis, while knockdown of GRM8 in SK-BR-3 cells induced the opposite results, indicating that GRM8 functions as an oncogene in breast cancer. The gene discussed is GRM8; the disease is breast cancer.