SHMT1 and neoplasm: There were 18 differentially expressed TCA cycle-related genes identified, with a threshold of p < 0.05 and |log2FC > 1.5|, of which 17 (PKM, GPI, IDH1, SHMT1, MTHFD1, SHMT2, ENO1, IDH2, ALDOA, DHFR, ELOVL3, SCD, TYMS, HK2, ALDOB, and PKLR) were upregulated and only one gene, ACAT1, was downregulated in tumor tissues (Figure 1A).