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Polypyrimidine Tract-Binding Protein 1 promotes proliferation, migration and invasion in clear-cell renal cell carcinoma by regulating alternative splicing of PKM.

ABSTRACT: Polypyrimidine Tract-Binding Protein 1 (PTBP1) is an essential RNA-binding protein that regulates diverse biological events through regulating alternative splice of mRNA. PTBP1 induces cancer-promoting splice variants and is related to tumorigenesis in several cancers. However, both the expression patterns and biological mechanisms of PTBP1 in clear-cell renal cell carcinoma (ccRCC) are unclear. We investigated PTBP1 expression in 533 ccRCC patients from TCGA and 30 ccRCC patients by immunohistochemistry, and found that PTBP1 expression levels were significantly increased in ccRCC tissues and that high PTBP1 expression was closely correlated with advanced tumor stage, AJCC stage and poor prognosis. Cell biological assays with siRNA-mediated knockdown and lentivirus vector-mediated over-expression demonstrated that PTBP1 promoted proliferation, migration and invasion in ccRCC cells in vitro. Furthermore, PTBP1 increased the transformation from pyruvate kinase muscle 1 (PKM1) to PKM2. Knockdown of PKM2 mainly abolished PTBP1-induced proliferation, migration and invasion in ccRCC cells in vitro. In conclusion, our study indicates that PTBP1 plays a tumorigenic role in ccRCC by mediating PKM2 alternative splicing and it may be a potential prognostic marker and a promising target for treatment of ccRCC.

SUBMITTER: Jiang J

PROVIDER: S-EPMC5336499 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Polypyrimidine Tract-Binding Protein 1 promotes proliferation, migration and invasion in clear-cell renal cell carcinoma by regulating alternative splicing of PKM.

Jiang Junyi J Chen Xu X Liu Hao H Shao Jing J Xie Ruihui R Gu Peng P Duan Chaohui C

American journal of cancer research 20170201 2

Polypyrimidine Tract-Binding Protein 1 (PTBP1) is an essential RNA-binding protein that regulates diverse biological events through regulating alternative splice of mRNA. PTBP1 induces cancer-promoting splice variants and is related to tumorigenesis in several cancers. However, both the expression patterns and biological mechanisms of PTBP1 in clear-cell renal cell carcinoma (ccRCC) are unclear. We investigated PTBP1 expression in 533 ccRCC patients from TCGA and 30 ccRCC patients by immunohisto ...[more]

PMID: 28337374

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Project description:BackgroundRenal cell carcinoma (RCC) accounts for 90% of renal cancers, of which clear cell carcinoma (ccRCC) is the most usual histological type. The process of alternative splicing (AS) contributes to protein diversity, and the dysregulation of protein diversity may have a great influence on tumorigenesis. We developed a prognostic signature and comprehensively analyzed the role of tumor immune microenvironment (TIME) and immune checkpoint blocking (ICB) treatment in ccRCC.MethodsTo identify prognosis-related AS events, univariate Cox regression was used and functional annotation was performed using gene set enrichment analysis (GSEA). In this study, prognostic signatures were developed based on multivariate Cox, univariate Cox, and LASSO regression models. Moreover, to assess the prognostic value, the proportional hazards model, Kruskal-Wallis analysis, and ROC curves were used. To obtain a better understanding of TIME in ccRCC, the ESTIMATE R package, single sample gene set enrichment analysis (ssGSEA) algorithm, CIBERSORT method, and the tumor immune estimation resource (TIMER) were applied. The database was searched to verify the expression of C4OF19 in tumor and normal samples. Regulatory networks for AS-splicing factors (SFs) were visualized using Cytoscape 3.9.1.ResultsThere were 9,347 AS cases associated with the survival of ccRCC patients screened. A total of eight AS prognostic signatures were developed with stable prognostic predictive accuracy based on splicing subtypes. In addition, a qualitative prognostic nomogram was developed, and the prognostic prediction showed high effectiveness. In addition, we found that the combined signature was significantly associated with the diversity of TIME and ICB treatment-related genes. C4ORF19 might become an important prognostic factor for ccRCC. Finally, the AS-SF regulatory network was established to clearly reveal the potential function of SFs.ConclusionWe found novel and robust indicators (i.e., risk signature, prognostic nomogram, etc.) for the prognostic prediction of ccRCC. A new and reliable prognostic nomogram was established to quantitatively predict the clinical outcome. The AS-SF networks could provide a new way for the study of potential regulatory mechanisms, and the important roles of AS events in the context of TIME and immunotherapy efficiency were exhibited. C4ORF19 was found to be a vital gene in TIME and ICB treatment.

Project description:BackgroundHighly proliferating cancer cells exhibit the Warburg effect by regulation of PKM alternative splicing and promoting the expression of PKM2. Majority of the alternative splicing events are known to occur in the nuclear matrix where various MARBPs actively participate in the alternative splicing events. SMAR1, being a MARBP and an important tumor suppressor, is known to regulate the splicing of various cancer-associated genes. This study focuses on the regulation of PKM alternative splicing and inhibition of the Warburg effect by SMAR1.MethodsImmunohistochemistry was performed in breast cancer patient samples to establish the correlation between SMAR1 and PKM isoform expression. Further, expression of PKM isoforms upon modulation in SMAR1 expression in breast cancer cell lines was quantified by qRT-PCR and western blot. The acetylation status of PTBP1 was estimated by immunoprecipitation along with its enrichment on PKM pre-mRNA by CLIP in SMAR1 knockdown conditions. The role of SMAR1 in tumor metabolism and tumorigenesis was explored by in vitro enzymatic assays and functional assays upon SMAR1 knockdown. Besides, in vivo tumor formation by injecting adeno-SMAR1-transduced MDA-MB-231 cells in NOD/SCID mice was performed.ResultsThe expression profile of SMAR1 and PKM isoforms in breast cancer patients revealed that SMAR1 has an inverse correlation with PKM2 and a positive correlation with PKM1. Further quantitative PKM isoform expression upon modulation in SMAR1 expression also reflects that SMAR1 promotes the expression of PKM1 over tumorigenic isoform PKM2. SMAR1 deacetylates PTBP1 via recruitment of HDAC6 resulting in reduced enrichment of PTBP1 on PKM pre-mRNA. SMAR1 inhibits the Warburg effect, tumorigenic potential of cancer cells, and in vivo tumor generation in a PKM2-dependent manner.ConclusionsSMAR1 regulates PKM alternative splicing by causing HDAC6-dependent deacetylation of PTBP1, resulting in reduced enrichment of PTBP1 on PKM pre-mRNA. Additionally, SMAR1 suppresses glucose utilization and lactate production via repression of PKM2 expression. This suggests that tumor suppressor SMAR1 inhibits tumor cell metabolism and tumorigenic properties of cancer cells via regulation of PKM alternative splicing.

Dataset Information

Polypyrimidine Tract-Binding Protein 1 promotes proliferation, migration and invasion in clear-cell renal cell carcinoma by regulating alternative splicing of PKM.

Publications

Polypyrimidine Tract-Binding Protein 1 promotes proliferation, migration and invasion in clear-cell renal cell carcinoma by regulating alternative splicing of PKM.

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