ABCG2 and cancer: KEGG analysis demonstrated that these different metabolites of distal gastric cancer and proximal gastric cancer were related to aminoacyl-tRNA biosynthesis, central carbon metabolism in cancer, neuroactive ligand-receptor interaction, histidine metabolism, biosynthesis of unsaturated fatty acids, protein digestion and absorption, ABC transporters, glutathione metabolism, apoptosis, FoxO signaling pathway, Huntington disease, long-term potentiation, spinocerebellar ataxia, nicotine addiction, GABAergic synapse, and alcoholism.