CXCR4 and breast cancer: Various heteromers have also been explored in HER2+ BC (HER2-CB2R, CXCR4-CB2R, GPR55-CB2R) as anti-cancer targets and as prognostic biomarkers [13,14,84,168], and the endocannabinoid cannabidiol has been shown to affect BC cell proliferation and invasiveness [169].