Efficacy of Methionine-Restricted Diets on Cancers In Vivo

Methionine (MET) dependence is the elevated requirement of cancer cells for MET. Cancer cells are arrested when MET is restricted in late S/G₂ phase of the cell cycle. MET dependence may be the only known general metabolic defect in cancer. This chapter reviews the in vivo efficacy of dietary MET restriction (MR) to arrest human-cancer cell-line tumors and mouse tumors in nude mice. Human cancer xenografts in nude mice, when fed a MET-free diet, had greatly inhibited tumor growth. The body weight of mice on the MET-free diet was found to be maintainable by once-per-week administration of MET. These results suggested that MET dependence can be an important target for human cancer treatment. Yoshida sarcoma in nude mice on a MET-depleted diet regressed. MET depletion resulted in the extended survival of the tumor-bearing mice. These experiments are a prelude to further clinical studies of the efficacy of MR diets on cancer patients.