TGFB1 and neoplasm: For instance, arginine is essential for the survival and effector function of T cells.[12] Tumor‐associated macrophages (TAMs) can impair T cell function by upregulating arginase, which breaks down arginine into ornithine and urea.[13] Glutamine serves as a primary energy source for tumor‐infiltrating immune cells, and its deficiency can lead to decreased function of Th1 cells and downregulation of the anti‐tumor effector molecule IFN‐γ.[14] Leucine can be taken up by B cells in the colorectal cancer microenvironment, thereby promoting the expression of the immune‐suppressive cytokine TGF‐β1.