Silencing RNA-binding protein CELF1 inhibits tumor growth and alters gene expression in oral squamous cell carcinoma. Homo sapiens

RNA-binding proteins (RBPs) are critical regulators of gene expression, but only a small fraction have been studied for their role in malignancy. Here we report a systematic analysis of RBP CUGBP Elav-Like Family member 1 (CELF1 alias CUGBP1) roles in mRNA alternative splicing, translation and turnover in oral cancer cells. CELF1 is overexpressed in carcinogen-induced oral cancer tumorigenesis mouse model and specific inhibition of CELF1 reduces tumor growth in vivo. Deep transcriptomic analysis revealed that hundreds of mRNAs were differentially regulated as a function of CELF1 expression in oral cancer cells. More importantly, the presence of CELF1 promoted alternative splicing of several target mRNAs which are known to be involved in various cancer biological processes. Using a pulse SILAC-based quantitative proteomic approach, we observed hundreds of proteins whose translation was controlled by CELF1 and those altered proteins were implicated in malignancy. Altogether, these data provided a comprehensive view of the CELF1 mRNA regulatory network in OSCC and suggests that CELF1 is a viable target for therapeutic intervention. Significance Post-transcriptional mechanisms that regulate cancer cells which are believed to constitute the driving force of many malignancies are poorly understood. We show that oral squamous cell carcinoma (OSCC) emerge as a result of an over expressed RNA-binding protein CELF1, a protein implicated in mRNA turnover, alternative splicing and translation. The resulting mRNA expression repertoire regulates networks of genes whose expression changes regulate oral cancer pathogenesis. Inhibition of CELF1 mitigated OSCC tumor-forming capacity and offers an attractive therapeutic option for oral malignancies. Overall design: Transcriptomic analysis of UMSCC-74B oral cancer cells as a function of CELF1 protein expression.

RNA结合蛋白（RNA-binding proteins, RBPs）是基因表达的关键调控因子，但目前仅对极小一部分该类蛋白的恶性肿瘤调控功能开展了研究。本研究系统性分析了RNA结合蛋白家族成员CELF1（CUGBP Elav样家族成员1，别名CUGBP1）在口腔癌细胞中对mRNA可变剪接、翻译及降解的调控作用。研究发现，CELF1在致癌物诱导的口腔癌发生小鼠模型中呈过表达状态，而特异性抑制CELF1可在体内抑制肿瘤生长。深度转录组分析显示，口腔癌细胞中数百条mRNA的表达差异受CELF1表达水平调控。更为关键的是，CELF1可促进多个靶mRNA的可变剪接，而这些靶mRNA已知参与多种癌症相关生物学过程。本研究采用基于脉冲SILAC的定量蛋白质组学方法，观测到数百种蛋白质的翻译过程受CELF1调控，且这些差异表达蛋白均与恶性肿瘤发生发展密切相关。综上，本研究全面阐明了CELF1在口腔鳞状细胞癌（oral squamous cell carcinoma, OSCC）中的mRNA调控网络，并提示CELF1是极具潜力的临床治疗干预靶点。

研究意义：调控癌细胞的转录后机制被认为是多种恶性肿瘤的核心驱动因素，但目前对其了解仍十分有限。本研究证实，过表达的RNA结合蛋白CELF1可诱发口腔鳞状细胞癌（OSCC），该蛋白参与mRNA降解、可变剪接及翻译调控过程。由此产生的mRNA表达谱可调控一系列基因网络，这些基因的表达变化直接参与口腔癌的发病机制。抑制CELF1可显著减弱OSCC的成瘤能力，为口腔恶性肿瘤的治疗提供了极具吸引力的潜在策略与靶点。

总体设计：以UMSCC-74B口腔癌细胞为模型，分析CELF1蛋白表达水平对其转录组的调控效应。