Lactate exposure determined a significant increase in proliferating PH3-positive cells in RAS-overexpressing zebrafish brains, but not in control brains, and this was reverted by the selective inhibition of MCT1. This evidence suggests that lactate intake supports cell proliferation in cancer and that metabolic reshaping is a critical stimulus in the GBM microenvironment. The gene discussed is PHC3; the disease is glioblastoma.