GNMT: A multifaceted suppressor of hepatocarcinogenesis

Abstract

Glycine N-methyltransferase (GNMT) exerts a pivotal role in the methionine cycle and, consequently, contributes to the control of methylation reactions, and purine and pyrimidine synthesis. Numerous observations indicate that GNMT is a tumor suppressor gene, but the molecular mechanisms of its suppressive action have only been partially unraveled to date. Present knowledge indicates that GNMT acts through both epigenetic and genetic mechanisms. Among them are the decrease of AKT signaling through the inhibition of the RAPTOR/mTOR complex and the interaction of GNMT with the PTEN inhibitor, PREX2. Furthermore, GNMT is a polycyclic aromatic hydrocarbon-binding protein and a mediator of the induction, by polycyclic hydrocarbons of the cytochrome P450-1A1 gene, whose polymorphism is involved in favoring different types of cancers. Finally, GNMT suppresses the expression of the transcription factor NRF2, whose overexpression is associated with HCC development. These findings suggest a multifaceted suppressor mechanism of the GNMT gene.