Although glycine might be important for rapid cancer cell proliferation by supporting de novo purine nucleotide biosynthesis [6], glycine restriction alone didn’t have the same detrimental effect on cancer cells as serine starvation, which might be explained by the inter-conversion between serine and glycine in one-carbon metabolism by serine hydroxymethyl transferase (SHMT) [7, 16, 17], especially the mitochondrial glycine synthesis enzyme SHMT2 [6]. This evidence concerns the gene SHMT2 and cancer.