The impact of the RBM4-initiated splicing cascade on modulating the carcinogenic signature of colorectal cancer cells

Jung-Chun Lin,Yang C Fann,Yuan-Chii Lee,Kory R Johnson,Ying-Ju Lin,Yu-Chih Liang

doi:10.1038/srep44204

Abstract

A growing body of studies has demonstrated that dysregulated splicing profiles constitute pivotal mechanisms for carcinogenesis. In this study, we identified discriminative splicing profiles of colorectal cancer (CRC) cells compared to adjacent normal tissues using deep RNA-sequencing (RNA-seq). The RNA-seq results and cohort studies indicated a relatively high ratio of exon 4-excluded neuro-oncological ventral antigen 1 (Nova1−4) and intron 2-retained SRSF6 (SRSF6+intron 2) transcripts in CRC tissues and cell lines. Nova1 variants exhibited differential effects on eliminating SRSF6 expression in CRC cells by inducing SRSF6+intron 2 transcripts which were considered to be the putative target of alternative splicing-coupled nonsense-mediated decay mechanism. Moreover, the splicing profile of vascular endothelial growth factor (VEGF)165/VEGF165b transcripts was relevant to SRSF6 expression, which manipulates the progression of CRC calls. These results highlight the novel and hierarchical role of an alternative splicing cascade that is involved in the development of CRC.

Highlights

A growing body of studies has demonstrated that dysregulated splicing profiles constitute pivotal mechanisms for carcinogenesis
Overexpression of Nova[1] isoforms exerted opposite effects on diminishing E-cadherin expression and the concomitant upregulation of N-cadherin levels in colorectal cancer (CRC) cells (Fig. 4b, lanes 3, 4, 7, and 8). These results suggested that RNA-binding motif protein 4 (RBM4) and Nova[1] proteins potentially constitute an antagonistic mechanism that manipulates the epithelial-to-mesenchymal transition (EMT)-related pathway in CRC cells
We performed deep RNA sequencing (RNA-seq) to reveal the CRC-related splicing cascade composed of the Nova[1], SRSF6, and vascular endothelial growth factor (VEGF) genes

Summary

Introduction

A growing body of studies has demonstrated that dysregulated splicing profiles constitute pivotal mechanisms for carcinogenesis. The splicing profile of vascular endothelial growth factor (VEGF)165/VEGF165b transcripts was relevant to SRSF6 expression, which manipulates the progression of CRC calls These results highlight the novel and hierarchical role of an alternative splicing cascade that is involved in the development of CRC. Among these alternative splicing events, RBM4, Nova[1], SRSF6, and vascular endothelial growth factor 165 (VEGF165) comprised a splicing cascade in a consensus sequence-dependent manner which manipulated the migration and angiogenetic signature of CRC cells. These results suggested the potential value of splicing events as clinical applications for CRC treatment

Methods

Results

Conclusion