Vitamin B6 responsive growth of human tumors.

The model of human malignant tumors, heterotransplanted and passaged into athymic nude mice, proved to be a valuable tool for nutritional oncology. It showed that several human tumors proliferate in distinct dependence on the available vitamin B6. A surplus of the vitamin causes enhancement of growth. Proliferation is retarded in cases of reduced availability. The amount of vitamin B6 available does not only depend on the dietary supply. The contribution of the intestinal flora may be considerable. Therefore the adverse effect of a diet free of vitamin B6 is distinctly increased by additional application of a vitamin antagonist such as D-penicillamine for instance. It should be emphasized that this happens even in situations in which no clinical symptoms of vitamin deficiency could be observed at all. Our experimental findings may have consequences for those human patients who are stricken with vitamin B6 responsive tumors. A shifting supply of vitamin B6 should at least be avoided. Dietary guidance and a careful use of vitamin antagonists, such as D-penicillamine for instance, may be helpful.