The antitumor rationality of MGL elaborates from the lack of active methionine synthase in tumor cells “methionine auxotrophic”5,6, making the tumor cells are absolutely dependent on plasma L-methionine for their rapid proliferation, in contrary to the normal cells that have active methionine synthase, ensuring the targetability of MGL for attacking the tumor cells only5–8. The gene discussed is MTR; the disease is neoplasm.