Metabolomics analyses of cancer tissue from patients with colorectal cancer

The alteration of metabolism is essential for the initiation and progression of numerous types of cancer, including colorectal cancer (CRC). Metabolomics has been used to study CRC. At present, the reprogramming of the metabolism in CRC remains to be fully elucidated. In the present study, comprehensive untargeted metabolomics analysis was performed on the paired CRC tissues and adjacent normal tissues from patients with CRC (n=35) using ultra-high-performance liquid chromatography-mass spectrometry. Subsequently, bioinformatic analysis was performed on the differentially expressed metabolites. The changes in these differential metabolites were compared among groups of patients based on sex, anatomical tumor location, grade of tumor differentiation and stage of disease. A total of 927 metabolites were detected in the tissue samples, and 24 metabolites in the CRC tissue were significantly different compared with the adjacent normal tissue. The present study revealed that the levels of three amino acid metabolites were increased in the CRC tissue, specifically, N-α-acetyl-ε-(2-propenal)-Lys, cyclo(Glu-Glu) and cyclo(Phe-Glu). The metabolites with decreased levels in the CRC tissue included quinaldic acid (also referred to as quinoline-2-carboxilic acid), 17α- and 17β-estradiol, which are associated with tumor suppression activities, as well as other metabolites such as, anhydro-β-glucose, Asp-Arg, lysophosphatidylcholine, lysophosphatidylethanolamine (lysoPE), lysophosphatidylinositol, carnitine, 5′-deoxy-5′-(methylthio) adenosine, 2′-deoxyinosine-5′-monophosphate and thiamine monophosphate. There was no difference in the levels of the differential metabolites between male and female patients. The differentiation of CRC also showed no impact on the levels of the differential metabolites. The levels of lysoPE were increased in the right side of the colon compared with the left side of the colon and rectum. Analysis of the different tumor stages indicated that 2-aminobenzenesulfonic acid, P-sulfanilic acid and quinoline-4-carboxylic acid were decreased in stage I CRC tissue compared with stage II, III and IV CRC tissue. The levels of N-α-acetyl-ε-(2-propenal)-Lys, methylcysteine and 5′-deoxy-5′-(methylthio) adenosine varied at different stages of tumorigenesis. These differential metabolites were implicated in multiple metabolism pathways, including carbohydrate, amino acid, lipid, nucleotide and hormone. In conclusion, the present study demonstrated that CRC tumors had altered metabolites compared with normal tissue. The data from the metabolic profile of CRC tissues in the present study provided supportive evidence to understand tumorigenesis.