Vitamin B6 and cancer: adenosine-N6-diethylthioether N1-pyridoximine 5'-PO4, a circulating human tumor marker

Studies in my laboratory on the metabolism and utilization of labeled vitamin B6 by tumor-bearing animals and tumor cells in culture have shown the production and presence in the circulation of a novel pyridoxal 5'-phosphate conjugate metabolite (1-5). Using specific radiolabeling and analytical tests, its structure was tentatively identified (now confirmed) as adenosine-N6-diethylthioether-N1-pyridoximine 5'-phosphate (4-6). The novel vitamin conjugate was isolated from the plasma of patients and control subjects following extraction with perchloric acid and separation by pair-ion HPLC. This communication reports the chromatographic separation of the novel compound and its plasma levels in control subjects, cancer patients and patients with other ailments. The results show that the novel metabolite is a circulating human tumor marker with levels of up to 4x or greater seen in cancer patients compared to controls and to subjects with other ailments. The results indicate strongly that the novel circulating vitamin B6 conjugate compound can be successfully used for the detection of different malignancies in humans by evaluating its level in circulation.