KEGG pathway analysis showed that these differential metabolites were mainly concentrated in central carbon metabolism in cancer, alanine, aspartate and glutamate metabolism, ABC transporters, butanoate metabolism, glycine, serine and threonine metabolism, citrate cycle (TCA cycle), nicotinate and nicotinamide metabolism, protein digestion and absorption, and biosynthesis of amino acids (Fig. 1E and F). This evidence concerns the gene ABCG2 and cancer.