The pro-oncogenic effect of CB2R in HER2+ breast cancer was discovered when HER2-CB2R heteromers were detected in these cells, and having observed a simultaneous appearance of higher CB2 protein expression and poorer overall relapse-free and metastasis-free survival of patients (Pérez-Gómez et al., 2015). This evidence concerns the gene ERBB2 and breast carcinoma.