Clinical and biochemical studies of pyridoxine deficiency in patients with neoplastic diseases

Seventeen patients with advanced neoplastic diseases were fed a formula diet deficient in vitamin B6 for 10 to 80 days. In addition, nine of the patients received the B6 antagonist, 4-deoxypyridoxine (4-DOP), for periods ranging from 6 to 46 days. No definite antitumor effect could be observed in any of the patients studied despite ample biochemical and clinical evidence of vitamin B6 depletion. The study confirmed previous reported experiences in man and many other animal species that 4-DOP accentuates some of the manifestations of vitamin-B6 deficiency, particularly neurologic and dermatologic side effects. The lymphopenic effect of 4-DOP was demonstrated only in patients with normal bone marrow. In three of four patients with lymphoproliferative disease the peripheral lymphocyte count rose coincidentally with 4-DOP administration while in the fourth the rise developed immediately after discontinuation of 4-DOP and at the peak of toxicity. The study showed evidence of progressive tissue depletion when the patient was fed the deficient diet alone. Addition of 4-DOP to the deficient diet led to the transient reappearance of measurable pyridoxal phosphate in leukocytes and pyridoxic acid in the urine. This and the slight increase in reticulocyte counts during administration of 4-DOP raise the possibility that vitamin B6 was mobilized from certain tissue depots by the 4-DOP and was thus available for oxidation to pyridoxic acid and for use by the less depressed of the enzymes dependent upon vitamin B6.