Cancer-associated cachexia reduces survival, which has been attenuated by blocking the activin receptor type 2B (ACVR2B) ligands in mice. The purpose of this study was to unravel the underlying physiology and novel cachexia biomarkers using the colon-26 (C26) carcinoma model of cancer cachexia. BALB/c male mice were subcutaneously inoculated with C26 cancer cells or vehicle control. Tumor-bearing mice were treated with vehicle (C26+PBS) or soluble ACVR2B either before (C26+sACVR/b) or before and after (C26+sACVR/c) tumor formation. Skeletal muscle and serum metabolomics analysis was conducted by gas chromatography-mass spectrometry.
Cancer altered various biologically functional groups representing: 1) amino acids, 2) energy sources and 3) nucleotide related intermediates. Muscle metabolomics revealed increased content of free phenylalanine in cancer that strongly correlated with the loss of body mass within the last two days of the experiment. This correlation was also detected in serum. Decreased ribosomal RNA content and phosphorylation of a marker of pyrimidine synthesis revealed changes in nucleotide metabolism in cancer.
Overall, the effect of the experimental C26 cancer predominated over blocking ACVR2B ligands in both muscle and serum. However, the level of methyl phosphate, which was decreased in the muscle in cancer, was restored by sACVR2B-Fc treatment. In conclusion, experimental cancer affected muscle and blood metabolomes mostly independent of blocking ACVR2B ligands. Of the affected metabolites, we have identified free phenylalanine as a promising biomarker of muscle atrophy or cachexia. Finally, the decreased capacity for pyrimidine nucleotide and protein synthesis in tumor-bearing mice opens up new avenues in cachexia research.