LncRNA CASC9 interacts with CPSF3 to regulate TGF-β signaling in colorectal cancer

Abstract

Background Colorectal cancer (CRC) is the third most frequent cancer and the second leading cause of cancer-related death worldwide. Increasing evidence indicates that the deregulation of long noncoding RNAs (lncRNAs) contributes to tumor initiation and progression; however, little is known about the biological role of cancer susceptibility candidate 9 (CASC9) in CRC. Methods Novel lncRNAs potentially involved in CRC tumorigenesis were identified from datasets downloaded from The Cancer LncRNome Atlas and The Atlas of Noncoding RNAs in Cancer. The CRC cell lines HCT-116, HCT-116 p53 −/− , SW620, SW480, HT-29, LoVo, LS-174T, and RKO were used. Colony-formation, MTS, cell-cycle, apoptosis, and in-vivo tumorigenesis assays were used to determine the role of CASC9 in CRC cell growth in vitro and in vivo. Potential interaction between CASC9 and cleavage and polyadenylation specificity factor subunit 3 (CPSF3) was evaluated using RNA immunoprecipitation and RNA-protein pull-down assays. RNA-sequencing was performed to analyze gene expression following CASC9 knockdown. RT-qPCR, western blotting, and mRNA decay assays were performed to study the mechanisms involved. Results CASC9 was frequently upregulated in CRC, which was correlated with advanced TNM stage, and higher CASC9 levels were associated with poor patient outcomes. Knockdown of CASC9 inhibited growth and promoted apoptosis in CRC cells, whereas ectopic CASC9 expression promoted cell growth in vitro and in vivo. We demonstrated that CPSF3 is a CASC9-interacting protein, and knockdown of CPSF3 mimicked the effects of CASC9 knockdown in CRC cells. Furthermore, we found that CASC9 exerts its oncogenic activity by modulating TGFβ2 mRNA stability and upregulating the levels of TGFβ2 and TERT, resulting in an increase in phosphorylated SMAD3 and activation of TGF-β signaling, and enhanced TERT complex function in CRC cells. Finally, CPSF3 was significantly upregulated in CRC tissues as compared with adjacent or non-adjacent normal colon tissues, and CASC9, CPSF3, and TGFβ2 levels in human CRC tissues were positively correlated. Conclusions CASC9 is a promising prognostic predictor for patients with CRC and the CASC9-CPSF3-TGFβ2 axis is a potential therapeutic target for CRC treatment. Electronic supplementary material The online version of this article (10.1186/s13046-019-1263-3) contains supplementary material, which is available to authorized users.

<p>STAT3-Induced Upregulation of lncRNA CASC9 Promotes the Progression of Bladder Cancer by Interacting with EZH2 and Affecting the Expression of PTEN</p>

“…[21][22][23] However, till now, there are only several lncRNAs have been mechanistically characterized in BC. LncRNA CASC9 has been demonstrated to serve as an oncogenic factor in plenty of human cancers, such as breast cancer, 24 colorectal cancer, 25 and lung adenocarcinoma. 26 A pan-cancer analysis revealed that CASC9 was strikingly overexpressed in bladder cancers, especially in urothelial carcinomas with squamous differentiation or pure squamous bladder cancers, indicating the potential role of CASC9 in BC.…”

Prognostic and Predictive Values of the Autophagy Signature in Colon Cancer

“…lncRNAs dominate the upstream portion of the RNA network and function as primary effectors of mRNAs, and several lncRNAs are identi ed as potential prognostic factors in COAD [20,30]. Among these 14 lncRNAs in the model, PCAT6, CASC9, MIR4435-2HG, SNHG16, and LINC00513 have been reported to play a role in the pathogenesis and prognosis of various cancer types (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43). For example, CASC9 has been reported to be upregulated and conferred an oncogenic function in human hepatocellular carcinoma, oral carcinoma, gastric cancer, colorectal cancer, and esophageal cancer [28,[31][32][33].…”

“…In colorectal cancer, CASC9 was found to be negatively correlated with the miR-193a-5p expression, and promoted tumorigenesis via the miR-193a-5p/ERBB2 axis [34]. Luo et al [35] reported that the higher expression of the oncogenic CASC9 was associated with poor patient outcomes when interacting with CPSF3 to regulate TGF-β signaling. Consistently, it has been reported that the higher expression of PCAT6 was correlated with poorer clinical outcomes and further found that PCAT6 was able to inhibit cell apoptosis by regulating the anti-apoptotic protein ARC expression via the EZH2 in COAD [36].…”

Long non‐coding RNAs and TGF‐β signaling in cancer

“…In colorectal cancer, the cancer susceptibility candidate 9 ( CASC9 ) is a lncRNA that predicts poor survival for patients 37 . The pro‐tumorigenic function of CASC9 is due to the increased stabilization of TGFB2 levels, which lead to active TGF‐β2 signaling and enhanced p‐Smad3 levels 37 . The positive contribution of CASC9 to TGF‐β signaling depends on its binding to the protein cleavage and polyadenylation specific factor 3 (CPSF3), an mRNA‐processing factor, which is capable of directly interacting with TGFB2 mRNA 37 .…”