Here, we show that the treatment with the AEA analog metAEA phenocopies some of the in vitro (induction of CXCR4 expression and CXCR4-mediated cell invasion) and in vivo (induction of CXCR4-dependent lung metastasis) effects of FAAH silencing through a CBR-mediated mechanism, which strongly supports the existence of an endogenous AEA tone in BC cells that supports tumor progression and that is ultimately controlled by FAAH. This evidence concerns the gene CXCR4 and breast cancer.