The analysis of KEGG pathways showed that differential metabolites were enriched in the pathways of Central carbon metabolism in cancer, Protein digestion and absorption, Aminoacyl-tRNA biosynthesis, Biosynthesis of amino acids, ABC transporters, mTOR signaling pathway, Valine, leucine and isoleucine biosynthesis, and Pyrimidine metabolism. Here, ABCG2 is linked to cancer.