Our data confirmed the capacity of lactate to induce cell proliferation and wound healing in breast cancer cells, and, for first time to the best of our knowledge, they showed that these effects occurred through a complex mechanism involving the following: (i) stimulation of the lactate transporter MCT1-4; (ii) transduction of the signal through the increase in GPR81 expression; (iii) change in cell metabolism and ROS detoxifying defenses through the increase in IGFBP6 expression. This evidence concerns the gene HCAR1 and breast cancer.