BCL2 and cancer: Based on the notion that (i) several apoptotic stimuli induce cell death through a Bcl-2-regulated pathway and (ii) proteins belonging to Bcl2 family can play a dichotomous role, acting both as promoters as well as inhibitors of apoptotic events [21,45,46], we may suppose that the lower expression of Bcl-2 determined in metastatic tissue of 4T1 M. U-care mice could be related to a decrease in cancer cell proliferation, evidencing an alteration of the proliferation/apoptosis balance.