Comparison of the amino acid profile between the nontumor and tumor regions in patients with lung cancer

Energy metabolism in cancer cells is reprogrammed to meet the energy demands for cell proliferation under strict environments. In addition to the specifically activated metabolism of cancer, including the Warburg effect and glutaminolysis, most amino acids (AAs) are utilized for gluconeogenesis. Significant increases in AAs and energy metabolites in the tumor region occur in gastric and colon cancers. However, a different AA-related energy metabolism may exist in lung cancer because of the abundant blood supply to lung tissue. This study compared the profiles of AAs and their related metabolites in energy metabolism, analyzed by an HPLC-MS/MS system, between tissues from nontumor and tumor regions collected from 14 patients with non-small cell lung cancer (NSCLC). In the energic metabolism precursor categories, the glucogenic AAs, which included the pyruvate precursors (Ser, Gly, Thr, Ala, and Trp), the α-ketoglutarate precursors (Glu, Gln, and Pro) and the succinyl-CoA precursors (Val, Ile, and Met) were significantly increased in the tumor region compared to in the nontumor region. However, no significant differences existed between the two regions in the ketogenic AAs (Leu, Lys, and Tyr). These differences were not observed between the subgroups with and without diabetes mellitus in the two regions. The metabolites on the left-hand side of the TCA cycle were significantly higher in the tumor region, but no differences in metabolites in the right-hand side. The mRNA expressions of major AA transporters and cancer proliferation factors were also significantly increased in the tumor region, compared to these in their counterparts. In lung cancer, glucogenic AAs that are actively transported from circulating fluids would be predominantly utilized for gluconeogenesis, with and without diabetes mellitus. The characteristics of the AA-related metabolism would be associated with tissue-specific cell proliferation in patients with NSCLC.