Quantitative biochemical differences between tumor and host as a basis for cancer chemotherapy. I. Vitamin B6.

It has been postulated that cancer chemo therapy utilizing metabolic antagonists may be based on quantitative differences between normal and tumor tissue. In general, neoplasms have con siderably lower enzyme and vitamin concentra tions than most normal tissues, and, in some cases, the observed levels are lower in the cancer cell than in any normal tissue. Furthermore, it is known that inhibition by an antimetabolite de pends upon the concentration ratio of the metabo lite, or susceptible enzyme, and antagonist. Thus, it is reasoned that an enzyme in low concentration in cancer tissue may be blocked by means of an antagonist, while the activity of the same enzyme in nonmalignant cells would be only minimally depressed owing to its higher concentration. This concept has been previously recorded. Boyland (6) selected a catalase inhibitor, a-nitroso-/3-naphthosol for chemotherapeutic trial, reasoning that the significantly lower enzyme concentration in certain tumor tissues should per mit inhibition of tumor growth with doses of this agent tolerated by normal tissues. Ackermann and Potter (1) stated that ". . . it should be possible to