Project description:Epigenetic dysregulation plays a pivotal role in mixed-lineage leukemia (MLL) pathogenesis, therefore serving as a suitable therapeutic target. S-adenosylmethionine (SAM) is the universal methyl donor in human cells and is synthesized by methionine adenosyltransferase 2A (MAT2A), which is deregulated in different cancer types. Here, we used our human CRISPR/Cas9-MLL-rearranged (CRISPR/Cas9-MLLr) leukemia model, faithfully mimicking MLLr patients' pathology with indefinite growth potential in vitro, to evaluate the unknown role of MAT2A. Comparable to publicly available patient data, we detected MAT2A to be significantly overexpressed in our CRISPR/Cas9-MLLr model compared to healthy controls. By using non-MLLr and MLLr cell lines and our model, we detected an MLLr-specific enhanced response to PF-9366, a new MAT2A inhibitor, and small interfering (si) RNA-mediated knockdown of MAT2A, by alteration of the proliferation, viability, differentiation, apoptosis, cell cycling, and histone methylation. Moreover, the combinational treatment of PF-9366 with chemotherapy or targeted therapies against the SAM-dependent methyltransferases, disruptor of telomeric silencing 1 like (DOT1L) and protein arginine methyltransferase 5 (PRMT5), revealed even more pronounced effects. In summary, we uncovered MAT2A as a key regulator in MLL leukemogenesis and its inhibition led to significant anti-leukemic effects. Therefore, our study paves the avenue for clinical application of PF-9366 to improve the treatment of poor prognosis MLLr leukemia.
Project description:BACKGROUND:Hepatic stellate cell (HSC) activation induced by transforming growth factor β1 (TGF-β1) plays a pivotal role in fibrogenesis, while the complex downstream mediators of TGF-β1 in such process are largely unknown. METHODS:We performed pharmacoproteomic profiling of the mice liver tissues from control, carbon tetrachloride (CCl4)-induced fibrosis and NPLC0393 administrated groups. The target gene MAT2A was overexpressed or knocked down in vivo by tail vein injection of AAV vectors. We examined NF-κB transcriptional activity on MAT2A promoter via luciferase assay. Intracellular SAM contents were analyzed by LC-MS method. FINDINGS:We found that methionine adenosyltransferase 2A (MAT2A) is significantly upregulated in the CCl4-induced fibrosis mice, and application of NPLC0393, a known small molecule inhibitor of TGF-β1 signaling pathway, inhibits the upregulation of MAT2A. Mechanistically, TGF-β1 induces phosphorylation of p65, i.e., activation of NF-κB, thereby promoting mRNA transcription and protein expression of MAT2A and reduces S-adenosylmethionine (SAM) concentration in HSCs. Consistently, in vivo and in vitro knockdown of MAT2A alleviates CCl4- and TGF-β1-induced HSC activation, whereas in vivo overexpression of MAT2A facilitates hepatic fibrosis and abolishes therapeutic effect of NPLC0393. INTERPRETATION:This study identifies TGF-β1/p65/MAT2A pathway that is involved in the regulation of intracellular SAM concentration and liver fibrogenesis, suggesting that this pathway is a potential therapeutic target for hepatic fibrosis. FUND: This work was supported by National Natural Science Foundation of China (No. 81500469, 81573873, 81774196 and 31800693), Zhejiang Provincial Natural Science Foundation of China (No. Y15H030004), the National Key Research and Development Program from the Ministry of Science and Technology of China (No. 2017YFC1700200) and the Key Program of National Natural Science Foundation of China (No. 8153000502).
Project description:Hepatocellular carcinoma (HCC) is characterized by the down-regulation of the liver-specific methyladenosyltransferase 1A (<i>MAT1A</i>) gene, encoding the S-adenosylmethionine synthesizing isozymes MATI/III, and the up-regulation of the widely expressed methyladenosyltransferase 2A (<i>MAT2A</i>), encoding MATII isozyme, and methyladenosyltransferase 2B (<i>MAT2B</i>), encoding a ?-subunit without catalytic action that regulates MATII enzymatic activity. Different observations showed hepatocarcinogenesis inhibition by miR-203. We found that miR-203 expression in HCCs is inversely correlated with HCC proliferation and aggressiveness markers, and with <i>MAT2A</i> and <i>MAT2B</i> levels. MiR-203 transfection in HepG2 and Huh7 liver cancer cells targeted the 3'-UTR of <i>MAT2A</i> and <i>MAT2B</i>, inhibiting <i>MAT2A</i> and <i>MAT2B</i> mRNA levels and MAT?2 and MAT?2 protein expression. These molecular events were paralleled by an increase in SAM content and were associated with growth restraint and apoptosis, inhibition of cell migration and invasiveness, and suppression of the expression of <i>CD133</i> and <i>LIN28B</i> stemness markers. In contrast, <i>MAT2B</i> transfection in the same cell lines led to a rise of both MAT?2 and MAT?2 expression, associated with increases in cell growth, migration, invasion and overexpression of stemness markers and p-AKT. Altogether, our results indicate that the miR-203 oncosuppressor activity may at least partially depend on its inhibition of <i>MAT2A</i> and <i>MAT2B</i> and show, for the first time, an oncogenic activity of <i>MAT2B</i> linked to AKT activation.
Project description:Transcriptome analysis of human cells has revealed that intron retention controls the expression of a large number of genes with diverse cellular functions. Detained introns (DI) constitute a subgroup of transcripts with retained introns that are not exported to the cytoplasm but instead remain in the nucleus. Previous studies reported that the splicing of DIs in the CLK1 transcript is post-transcriptionally induced to produce mature mRNA in the absence of new transcription. Thus, CLK1-DI serves as a precursor or "reservoir" for the CLK1 mRNA. However, whether this is a universal mechanism for gene regulation by intron detention remains unknown. The MAT2A gene encodes S-adenosylmethionine (SAM) synthetase and it contains a DI that is regulated in response to intracellular SAM levels. We used three independent assays to assess the precursor-product relationship between MAT2A-DI and MAT2A mRNA. In contrast to CLK1-DI, these data support a model in which the MAT2A-DI transcript is not a precursor to mRNA but is instead a "dead-end" RNA fated for nuclear decay. Additionally, we show that in SAM-deprived conditions the cotranscriptional splicing of MAT2A detained introns increases. We conclude that polyadenylated RNAs with DIs can have at least two distinct fates. They can serve as nuclear reservoirs of pre-mRNAs available for rapid induction by the cell, or they constitute dead-end RNAs that are degraded in the nucleus.
Project description:Epidermal growth factor receptor (EGFR) is involved in multiple aspects of cancer cell biology. EGFR has already been identified as an important target for cancer therapy, with various kinds of EGFR inhibitors currently used in treatment of several human cancers. Recently, EGFR and its downstream signaling pathways were identified as being associated with cisplatin sensitivity. In addition, EGFR inhibitors have shown significant promise for patients who failed cisplatin-based therapy. In this study, we investigated whether treatment with an EGFR inhibitor improves cisplatin sensitivity in oral squamous cell carcinoma (OSCC) cell lines. The effects of a combination of AG1478, a specific EGFR tyrosine kinase inhibitor, with cisplatin were evaluated in cultured OSCC cell lines and cisplatin-resistant sublines. Higher expression of EGFR and p-EGFR was found in the two cisplatin-resistant cell lines compared with the corresponding parental cell lines. In addition, augmented inhibition of OSCC cell growth by the combination of AG1478 with cisplatin was found in both cell lines. These results suggest that the combination of an EGFR inhibitor and cisplatin may be useful as a rational strategy for the treatment of patients with oral cancer with acquired cisplatin resistance.
Project description:Up to 20% of individuals who have thoracic aortic aneurysms or acute aortic dissections but who do not have syndromic features have a family history of thoracic aortic disease. Significant genetic heterogeneity is established for this familial condition. Whole-genome linkage analysis and exome sequencing of distant relatives from a large family with autosomal-dominant inheritance of thoracic aortic aneurysms variably associated with the bicuspid aortic valve was used for identification of additional genes predisposing individuals to this condition. A rare variant, c.1031A>C (p.Glu344Ala), was identified in MAT2A, which encodes methionine adenosyltransferase II alpha (MAT II?). This variant segregated with disease in the family, and Sanger sequencing of DNA from affected probands from unrelated families with thoracic aortic disease identified another MAT2A rare variant, c.1067G>A (p.Arg356His). Evidence that these variants predispose individuals to thoracic aortic aneurysms and dissections includes the following: there is a paucity of rare variants in MAT2A in the population; amino acids Glu344 and Arg356 are conserved from humans to zebrafish; and substitutions of these amino acids in MAT I? are found in individuals with hypermethioninemia. Structural analysis suggested that p.Glu344Ala and p.Arg356His disrupt MAT II? enzyme function. Knockdown of mat2aa in zebrafish via morpholino oligomers disrupted cardiovascular development. Co-transfected wild-type human MAT2A mRNA rescued defects of zebrafish cardiovascular development at significantly higher levels than mRNA edited to express either the Glu344 or Arg356 mutants, providing further evidence that the p.Glu344Ala and p.Arg356His substitutions impair MAT II? function. The data presented here support the conclusion that rare genetic variants in MAT2A predispose individuals to thoracic aortic disease.
Project description:Methionine adenosyltransferase 2A (MAT2A) is an enzyme that catalyzes the formation of S-adenosylmethionine (SAMe) by joining methionine and ATP. SAMe is a methyl donor for transmethylation and has an important role for DNA and/or protein methylation. MAT2A is expressed widely in many tissues especially in kidney. Several studies have demonstrated that there are abnormal expressions of MAT2A in several kinds of cancers such as liver and colon cancers. But the relationship of MAT2A between renal cell carcinomas (RCC) is less understood.The mRNA expression level of the MAT2A gene was determined in 24 RCC patients and 4 RCC cell lines, using real-time quantitative-polymerase chain reaction (RT-PCR). The MAT2A protein content was measured by western blotting and immunohistochemical analysis in 55 RCC patients. The mRNA levels of heme oxygenase-1 (HO-1) and cyclooxygenase-2 (COX-2) were also analysized in patients using RT-PCR. The correlations between the MAT2A and HO-1 as well as COX-2 were analyzed with nonparametric Spearman method.MAT2A transcript was significantly downregulated in cancer tissues compared to normal tissues (P < 0.05). Immunohistochemical analysis and western blotting indicated that level of MAT2A protein was decreased in cancer tissues. The statistical analysis reveals a negative correlation between MAT2A and HO-1 expression in RCC patients and cell lines (P < 0.01).This study demonstrated that MAT2A was lower expression in cancer tissues, suggesting that it may be involved in the development of RCC. MAT2A is a transcriptional corepressor for HO-1 expression by supplying SAM for methyltransferases, which may be one of potential mechanism of MAT2A as tumor suppressor in kidney carcinogenesis.
Project description:Human methionine S-adenosyltransferase (MAT2A) catalyzes the formation of S-adenosylmethionine (SAM) from ATP and methionine. Synthetic lethal genetic analysis has identified MAT2A as an anticancer target in tumor cells lacking expression of 5'-methylthioadenosine phosphorylase (MTAP). Approximately 15% of human cancers are MTAP-/-. The remainder can be rendered MTAP- through MTAP inhibitors. We used kinetic isotope effect (KIE), commitment factor (Cf), and binding isotope effect (BIE) measurements combined with quantum mechanical (QM) calculations to solve the transition state structure of human MAT2A. The reaction is characterized by an advanced SN2 transition state. The bond forming from the nucleophilic methionine sulfur to the 5'-C of ATP is 2.03 Å at the transition state (bond order of 0.67). Departure of the leaving group triphosphate of ATP is well advanced and forms a 2.32 Å bond between the 5'-C of ATP and the oxygen of the triphosphate (bond order of 0.23). Interaction of MAT2A with its MAT2B regulatory subunit causes no change in the intrinsic KIEs, indicating the same transition state structure. The transition state for MAT2A is more advanced along the reaction coordinate (more product-like) than that from the near-symmetrical transition state of methionine adenosyltransferase from E. coli.
Project description:PURPOSE:To test whether a microRNA (miRNA) panel may serve as an alternative biomarker of fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor sensitivity in lung cancer. METHODS:Histologically diverse lung cancer cell lines were submitted to assays for ponatinib and AZD4547 sensitivity. miRNAs, FGFR1 messenger RNA, gene copy number, and protein expression were detected by real-time quantitative PCR, fluorescence in-situ hybridization, and immunoblotting in 34 lung cancer cell lines. RESULTS:Among 34 cell lines, 14 exhibited ponatinib sensitivity and 20 exhibited AZD4547 sensitivity (drug concentration causing 50% inhibition values < 100 nmol/L). A total of 39 of the 377-miRNA set were initially identified from the 4 paired ponatinib-sensitive or -insensitive cell lines to have at least an 8-fold differential expression and then were detected in all the 34 cell lines. A predictive panel of 3 miRNAs (let-7c, miRNA155, and miRNA218) was developed that had an area under the curve (AUC) of 0.886 with a sensitivity of 71.4% and specificity of 77.3% to predict response to ponatinib. The miRNA panel performed similar to FGFR1 protein expression (AUC = 0.864) and messenger RNA expression (AUC = 0.939), and better than FGFR1 amplification (AUC = 0.696). Furthermore, we validated this panel using data for sensitivity to AZD4547 in the cell line cohort with an AUC of 0.931 and a sensitivity of 73.3% and specificity of 76.2%, respectively. CONCLUSION:The developed miRNA panel (let-7c, miRNA155, and miRNA218) may be useful in predicting response to FGFR tyrosine kinase inhibitors, either ponatinib or AZD4547 in lung cancer cell lines, and warrants further validation in the clinical setting.