PRL and breast carcinoma: The first evidence for a control of the ECS on estrogen system was provided by De Petrocellis et al., (1998) [206] and Melck et al., (2000) [200] who showed that AEA treatment was able to inhibit the proliferation of prolactin (PRL)-responsive human breast cancer cells and this effect was mediated by the down-regulation of the PRL receptor.