ABSTRACT
The methylthioadenosine phosphorylase (MTAP) gene is located adjacent to the cyclin-dependent kinase inhibitor 2A (CDKN2A) tumor-suppressor gene and is co-deleted with CDKN2A in approximately 15% of all cancers. This co-deletion leads to aggressive tumors with poor prognosis that lack effective, molecularly targeted therapies. The metabolic enzyme methionine adenosyltransferase 2α (MAT2A) was identified as a synthetic lethal target in MTAP-deleted cancers. We report the characterization of potent MAT2A inhibitors that substantially reduce levels of S-adenosylmethionine (SAM) and demonstrate antiproliferative activity in MTAP-deleted cancer cells and tumors. Using RNA sequencing and proteomics, we demonstrate that MAT2A inhibition is mechanistically linked to reduced protein arginine methyltransferase 5 (PRMT5) activity and splicing perturbations. We further show that DNA damage and mitotic defects ensue upon MAT2A inhibition in HCT116 MTAP-/- cells, providing a rationale for combining the MAT2A clinical candidate AG-270 with antimitotic taxanes.
Subject(s)
DNA Damage/drug effects , Enzyme Inhibitors/pharmacology , Methionine Adenosyltransferase/antagonists & inhibitors , Protein-Arginine N-Methyltransferases/genetics , Purine-Nucleoside Phosphorylase/genetics , RNA Splicing/drug effects , RNA, Messenger/genetics , Animals , Cell Line , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p16 , DNA Damage/genetics , Gene Deletion , HCT116 Cells , HEK293 Cells , Humans , Methionine Adenosyltransferase/genetics , Mice, Inbred NOD , Mice, Nude , Mice, SCID , Neoplasms/drug therapy , Neoplasms/genetics , RNA Splicing/genetics , S-Adenosylmethionine/metabolismABSTRACT
Complex interactions between genetic and environmental factors are widely believed to underlie the incidence and progression of Parkinson's disease (PD). Rotenone is a naturally occurring metabolic toxin employed as an insecticide and piscicide identified as a risk factor for the development of PD in agricultural workers. The Nlrp3 inflammasome is an intracellular mediator that can initiate an inflammatory cascade in response to cellular stress. Reports by others indicating that NLRP3 expression was detectable in tissues obtained from Alzheimer's disease patients and that the PD-associated protein α-synuclein could activate inflammasomes in cultured glial cells, prompted us to test the prediction that Nlrp3 was required for the development of Parkinson's-like changes resulting from rotenone exposure in mice. We exposed wild type and Nlrp3-/- mice to chronic low doses of intragastric rotenone and conducted longitudinal behavioral and serum cytokine analysis followed by evaluation of neuroinflammatory and neurodegenerative endpoints in brain tissues. We observed progressive rotenone-dependent changes in serum cytokine levels and circulating leukocytes in wild type mice not observed in Nlrp3-/- mice. Analysis of brain tissues revealed Nlrp3-dependent neuroinflammation and nigral cell loss in mice exposed to rotenone as compared with mice exposed to vehicle alone. Together, our findings provide compelling evidence of a role for Nlrp3 in nigral degeneration and neuroinflammation resulting from systemic rotenone exposure and suggest that the suppression of NLRP3 activity may be a rational neuroprotective strategy for toxin-associated PD.