Riboflavin and cancer: a review.

The relationship of riboflavin to cancer is intriguing but many gaps remain in our knowledge. Several studies indicate that riboflavin deficiency inhibits tumor growth in experimental animals and possibly in man, but the precise mechanisms involved have not been elucidated. Azo dye carcinogenesis in liver appears to be a special case in that riboflavin deficiency increases the potency of these drugs in tumor causation, probably in large measure because flavin cofactors are involved in their metabolic degradation. Riboflavin influences uptake of chemotherapeutic drugs in at least one instance (methotrexate) into neoplastic cells. The fact that folic acid metabolism depends upon flavin cofactors may have implications for the use of folate antagonists in cancer chemotherapy.