A mice model of breast cancer showed that a GABAB-R agonist potentiates lung metastasis without affecting primary tumor volume, whereas an antagonist decreased metastases.280 Baclofen, a GABAB-R agonist, induces migration, invasion, and metastasis mediated by ERK1/2; in contrast, a GABAB-R antagonist (CGP55845) decreased migration and invasion. This evidence concerns the gene MAPK3 and breast cancer.