Reversion from Methionine Addiction to Methionine Independence Results in Loss of Tumorigenic Potential of Highly-malignant Lung-cancer Cells

Abstract

Background/Aim: Methionine addiction, a fundamental and general hallmark of cancer, is due to the excess use of methionine for transmethylation, and is described as the Hoffman-effect. Methionine-addicted cancer cells can revert at low frequency to methionine independence when selected under methionine-restriction. We report here that highly-malignant methionine-addicted H460 human lung-cancer cells, when selected for methionine independence, have greatly-reduced tumorigenic potential. Materials and Methods: Methionine-addicted H460 parental cancer cells and methionine-independent revertant H460-R1 cells were injected in nude mice subcutaneously. Results: When the parental H460 methionine-addicted cells were injected in nude mice at 2.5×10⁵, 1×10⁵ and 5×10⁴, the cells could form tumors. In contrast, the H460-R1 methionine-independent revertant cells could not form tumors when the above-listed cell numbers were injected in nude mice. Conclusion: There is a tight linkage between methionine addiction and malignancy.