Mass Spectrometry

Application of stable isotopes, especially carbon and nitrogen, are becoming a powerful tool in medical science. A novelapplication of the natural abundances of nitrogen isotopes, 14N and 15N in the understanding of amino acid metabolism inhuman colorectal cancer cells was carried out. Nitrogen isotope ratios are of particular advantage to understand the metabolic stateof cancer cells, since most biochemical reactions involve transfer of nitrogen. In this study nitrogen isotopes of individual amino acids from human colorectal cancer cell lines were analyzed. Significant effects were noticed in the case of glutamic acid, alanine,aspartic acid and proline between cancer and healthy cells. The data suggest that glutamic acid is a nitrogen acceptor while alanine,aspartic acid and proline are nitrogen donors in cancerous cells. One plausible explanation is the xtransamination of the three acids toproduce glutamic acid in cancerous cells. The findings are significant since glutamic acid and alanine make up more than 60 per centof the total amino acids in the human body. Glutamine is a significant source of energy for cells and also a prime donor of nitrogenin the biosynthesis of  amino acids. Several studies have advocated the role of glutamic acid incancer therapy. Identification ofmetabolic signatures in cancer cells will be crucial for advancement of cancer therapies based on the cell’s metabolic state.