MTHFS and cancer: Methenyltetrahydrofolate synthetase (MTHFS) catalyses 5‐formyltetrahydrofolate (5‐f‐THF) conversion to 5,10‐methenyltetrahydrofolate (5,10‐CH‐THF) and then participates in the synthesis of purine, which is upregulated in various cancers.194