HUMAN TUMORS ARE METHIONINE DEPENDENT IN-VIVO

Methionine-dependence is a tumor-specific biochemical defect expressed by the inability or decreased ability of turners to grow under the co ndition of methionine-depletion. Many reports have shown that methioni ne-dependence occurs in human tumors of all types, including fresh sur gical specimens in vitro. However, in vivo determinations of methionin e-dependence have thus fn, been made only ii? rodent malignant tumors using methionine-deficient diets. We report here for the first time th at human cancer xenografts in nude mice are methionine-dependent and w hen fed a methionine-free diet tumor growth is greatly inhibited. The body weight of mice on the methionine-free diet was found to be mainta inable by once-per-week administration of methionine. The data present ed here suggest that methionine-dependence can be an important target for. human cancer treatment.