SHMT1 and acute lymphoblastic leukemia: Strikingly, when ranking T-ALL samples according to mRNA expression level of the different serine/glycine synthesis enzymes (PHGDH, PSAT1, PSPH, SHMT1 and SHMT2), NKX2–1 altered samples clustered on the side of the samples with the highest expression of all serine/glycine pathway enzymes (Fig. 1d).