ARG1 and neoplasm: The production of lactate by cancer cells in GBM has been reported to promote M2 polarization and tumor angiogenesis of tumor-associated macrophages (TAMs) (23), the possible mechanism is that lactate can upregulate the expression of Vascular Endothelial Growth Factor (VEGF) and ARG1 genes through HIF1a-mediated mechanisms, promoting macrophage M2 polarization (24).