Скачать или смотреть Protein Methyltransferase Inhibitors as Personalized Cancer Therapeutics

Jesse Smith, PhD
The protein methyltransferases (PMTs) constitute a class of enzymes that catalyze the methylation of lysine or arginine residues on histones and other proteins. A number of PMTs have been shown to be genetically altered in cancers through, for example, gene amplification, chromosomal translocations, point mutations, and synthetic lethal relationships. The enzymes DOT1L and EZH2 provide two representative examples of altered PMTs that act as genetic drivers of specific human cancers. The enzymatic activity of DOT1L is associated with a chromosomal translocation that is universally found in patients with MLL-rearranged leukemia.Point mutations at Y641 of EZH2 are found in a subset of non-Hodgkin lymphoma patients; the enzymatic activity of both wild-type and mutant EZH2 are required for pathogenesis in these patients. In addition, deletion of the INI1 (SMARCB1 or hSNF5) subunit of the SWI/SNF chromatin-remodeling complex occurs in nearly all malignant rhabdoid tumors (MRTs), a childhood cancer with a particularly poor prognosis. An antagonistic relationship has been demonstrated between the biochemical action on chromatin of the SWI/SNF complex and EZH2 (in the context of the polycomb repressive complex 2) that is relieved in MRTs because of the INI1 deletion. Consequently, MRTs demonstrate increased reliance on the enzymatic activity of EZH2 for proliferation, and we have shown that MRT cells deficient in INI1 are selectively killed by inhibition of EZH2 in cell culture and in mouse xenograft models. Drug discovery efforts have yielded potent, selective inhibitors of each of these targets that have now transitioned into phase I clinical trials. These inhibitors affect the appropriate histone methyl marks in cells, lead to selective cell killing that is dependent on genetic alteration of the target enzyme, and affect tumor growth inhibition in xenograft models. These data portend the effective use of selective PMT inhibitors as a novel modality for future personalized cancer therapeutics.