剪接因子 SRSF1 通过 PTPMT1 的致癌剪接转换促进乳腺癌的进展。
Splicing factor SRSF1 promotes breast cancer progression via oncogenic splice switching of PTPMT1.
机构信息
Department of General Surgery, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
Liver Cancer Institute, Zhongshan Hospital, Fudan University & State Key Laboratory of Genetic Engineering, Fudan University, Shanghai, 200032, China.
出版信息
J Exp Clin Cancer Res. 2021 May 15;40(1):171. doi: 10.1186/s13046-021-01978-8.
BACKGROUND
Intensive evidence has highlighted the effect of aberrant alternative splicing (AS) events on cancer progression when triggered by dysregulation of the SR protein family. Nonetheless, the underlying mechanism in breast cancer (BRCA) remains elusive. Here we sought to explore the molecular function of SRSF1 and identify the key AS events regulated by SRSF1 in BRCA.
METHODS
We conducted a comprehensive analysis of the expression and clinical correlation of SRSF1 in BRCA based on the TCGA dataset, Metabric database and clinical tissue samples. Functional analysis of SRSF1 in BRCA was conducted in vitro and in vivo. SRSF1-mediated AS events and their binding motifs were identified by RNA-seq, RNA immunoprecipitation-PCR (RIP-PCR) and in vivo crosslinking followed by immunoprecipitation (CLIP), which was further validated by the minigene reporter assay. PTPMT1 exon 3 (E3) AS was identified to partially mediate the oncogenic role of SRSF1 by the P-AKT/C-MYC axis. Finally, the expression and clinical significance of these AS events were validated in clinical samples and using the TCGA database.
RESULTS
SRSF1 expression was consistently upregulated in BRCA samples, positively associated with tumor grade and the Ki-67 index, and correlated with poor prognosis in a hormone receptor-positive (HR+) cohort, which facilitated proliferation, cell migration and inhibited apoptosis in vitro and in vivo. We identified SRSF1-mediated AS events and discovered the SRSF1 binding motif in the regulation of splice switching of PTPMT1. Furthermore, PTPMT1 splice switching was regulated by SRSF1 by binding directly to its motif in E3 which partially mediated the oncogenic role of SRSF1 by the AKT/C-MYC axis. Additionally, PTPMT1 splice switching was validated in tissue samples of BRCA patients and using the TCGA database. The high-risk group, identified by AS of PTPMT1 and expression of SRSF1, possessed poorer prognosis in the stage I/II TCGA BRCA cohort.
CONCLUSIONS
SRSF1 exerts oncogenic roles in BRCA partially by regulating the AS of PTPMT1, which could be a therapeutic target candidate in BRCA and a prognostic factor in HR+ BRCA patient.
背景
大量证据表明，当 SR 蛋白家族失调时，异常的可变剪接（AS）事件会影响癌症的进展。然而，乳腺癌（BRCA）的潜在机制仍难以捉摸。在这里，我们试图探索 SRSF1 的分子功能，并确定 SRSF1 调节的 BRCA 中的关键 AS 事件。
方法
我们基于 TCGA 数据集、Metabric 数据库和临床组织样本，对 BRCA 中 SRSF1 的表达和临床相关性进行了全面分析。在体外和体内进行了 SRSF1 在 BRCA 中的功能分析。通过 RNA-seq、RNA 免疫沉淀-PCR（RIP-PCR）和体内交联免疫沉淀（CLIP）鉴定 SRSF1 介导的 AS 事件及其结合基序，进一步通过小基因报告基因检测进行验证。通过 P-AKT/C-MYC 轴，鉴定 PTPMT1 外显子 3（E3）AS 部分介导了 SRSF1 的致癌作用。最后，在临床样本和 TCGA 数据库中验证了这些 AS 事件的表达和临床意义。
结果
SRSF1 在 BRCA 样本中的表达一致上调，与肿瘤分级和 Ki-67 指数呈正相关，并与激素受体阳性（HR+）队列中的不良预后相关，这促进了体外和体内的增殖、细胞迁移和抑制凋亡。我们鉴定了 SRSF1 介导的 AS 事件，并发现了 SRSF1 在 PTPMT1 剪接转换调控中的结合基序。此外，SRSF1 通过直接结合其 E3 中的基序来调节 PTPMT1 的剪接转换，部分通过 AKT/C-MYC 轴介导了 SRSF1 的致癌作用。此外，在 BRCA 患者的组织样本和 TCGA 数据库中验证了 PTPMT1 的剪接转换。在 TCGA BRCA 队列的 I/II 期，通过 PTPMT1 的 AS 和 SRSF1 的表达鉴定的高危组，预后较差。
结论
SRSF1 通过调节 PTPMT1 的 AS 在 BRCA 中发挥致癌作用，这可能是 BRCA 的治疗靶点候选物和 HR+BRCA 患者的预后因素。
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