SHMT1 and esophageal squamous cell carcinoma: According to the analysis of TCGA-ESCA data, we found that the expression of serine hydroxymethyltransferases 1, 2 (SHMT1, SHMT2) and glycine decarboxylase (GLDC), which catalyze the conversion of serine to glycine, were upregulated in ESCC cancer tissues compared with normal tissues (Figure 4B).