Metabolomics and metabolic pathway networks from human colorectal cancers, adjacent mucosa, and stool.
BACKGROUND
Colorectal cancers (CRC) are associated with perturbations in cellular amino acids, nucleotides, pentose-phosphate pathway carbohydrates, and glycolytic, gluconeogenic, and tricarboxylic acid intermediates. A non-targeted global metabolome approach was utilized for exploring human CRC, adjacent mucosa, and stool. In this pilot study, we identified metabolite profile differences between CRC and adjacent mucosa from patients undergoing colonic resection. Metabolic pathway analyses further revealed relationships between complex networks of metabolites.


METHODS
Seventeen CRC patients participated in this pilot study and provided CRC, adjacent mucosa ~10 cm proximal to the tumor, and stool. Metabolomes were analyzed by gas chromatography-mass spectrometry (GC/MS) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). All of the library standard identifications were confirmed and further analyzed via MetaboLync(TM) for metabolic network interactions.


RESULTS
There were a total of 728 distinct metabolites identified from colonic tissue and stool matrices. Nineteen metabolites significantly distinguished CRC from adjacent mucosa in our patient-matched cohort. Glucose-6-phosphate and fructose-6-phosphate demonstrated 0.64-fold and 0.75-fold lower expression in CRC compared to mucosa, respectively, whereas isobar: betaine aldehyde, N-methyldiethanolamine, and adenylosuccinate had 2.68-fold and 1.88-fold higher relative abundance in CRC. Eleven of the 19 metabolites had not previously been reported for CRC relevance. Metabolic pathway analysis revealed significant perturbations of short-chain fatty acid metabolism, fructose, mannose, and galactose metabolism, and glycolytic, gluconeogenic, and pyruvate metabolism. In comparison to the 500 stool metabolites identified from human CRC patients, only 215 of those stool metabolites were also detected in tissue. This CRC and stool metabolome investigation identified novel metabolites that may serve as key small molecules in CRC pathogenesis, confirmed the results from previously reported CRC metabolome studies, and showed networks for metabolic pathway aberrations. In addition, we found differences between the CRC and stool metabolomes.


CONCLUSIONS
Stool metabolite profiles were limited for direct associations with CRC and adjacent mucosa, yet metabolic pathways were conserved across both matrices. Larger patient-matched CRC, adjacent non-cancerous colonic mucosa, and stool cohort studies for metabolite profiling are needed to validate these small molecule differences and metabolic pathway aberrations for clinical application to CRC control, treatment, and prevention.
Department of Environmental and Radiological Health Sciences, Colorado State University, 200 West Lake Street, 1680 Campus Delivery, Fort Collins, CO 80523 USA.
Dustin G
DG
Brown
Department of Clinical Sciences, Colorado State University, Fort Collins, CO 80523 USA.
Sangeeta
S
Rao
Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, CO 80523 USA.
Tiffany L
TL
Weir
University of Colorado Health-North, Fort Collins, CO 80522 USA.
Joanne
J
O'Malia
University of Colorado Health-North, Fort Collins, CO 80522 USA.
Marlon
M
Bazan
Division of Medical Oncology, University of Colorado School of Medicine, Aurora, CO 80045 USA.
Regina J
RJ
Brown
Department of Environmental and Radiological Health Sciences, Colorado State University, 200 West Lake Street, 1680 Campus Delivery, Fort Collins, CO 80523 USA ; Department of Clinical Sciences, Colorado State University, Fort Collins, CO 80523 USA.
Elizabeth P
EP
Ryan
Cancer; Colon mucosa; Colorectal; Metabolic pathways; Metabolites; Metabolomics; Stool; Tumor