Methionine addiction of cancer cells targeted by methioninase

All types of cancer are addicted to methionine, which is known as the “Hoffman effect”. Restricting methionine inhibits the growth and proliferation of all tested types of cancer cells, while normal cells are unaffected. Methionine addiction is targeted with methioninase (METase), which has been shown to be effective and safe as a therapy for all types of cancer cells and animal cancer models, either alone or in combination with common cancer medications. Approximately six years ago, researchers developed a rMETase that may be taken orally as a supplement and has resulted in anecdotal positive results in patients with advanced cancer. Currently, there are 8 clinical studies on METase, including 2 from the 1990s and 6 more recent ones. This review focuses on the clinical studies of METase-mediated methionine restriction, specifically the oral dosage form of rMETase as a supplement alone or in combination with common chemotherapeutic agents in the treatment of patients with advanced cancer.