RING-Finger Protein 6 Amplification Activates JAK/STAT3 Pathway by Modifying SHP-1 Ubiquitylation and Associates with Poor Outcome in Colorectal Cancer

Objective: The E3 ubiquitin ligase RNF6 (RING-finger protein 6) plays a crucial role in carcinogenesis. However, the copy number and expression of RNF6 were rarely reported in colorectal cancer. We aimed to explore the mechanical, biological, and clinical role of RNF6 in colorectal cancer initiation and progression. Design: The copy number and expression of RNF6 were analyzed from Tumorscape and The Cancer Genome Atlas (TCGA) datasets. Gene expressions were examined by real-time PCR, Western blot, and immunohistochemical staining. Gene expression profiling studies were performed to identify pivotal genes regulated by RNF6. Biological function of RNF6 on tumor growth and metastasis was detected in vivo and in vitro. Role of RNF6 in modulating SHP-1 expression was examined by coimmunoprecipitation and confocal microscopy, respectively. Results: The copy number of RNF6 was significantly amplified in colorectal cancer, and the amplification was associated with RNF6 expression level. Amplification and overexpression of RNF6 positively correlated with patients with colorectal cancer with poor prognosis. The gene set enrichment analysis (GSEA) revealed cell proliferation, and invasion-related genes were enriched in RNF6 high-expressed colorectal cancer cells as well as in patients from TCGA dataset. Downregulation of RNF6 impaired the colorectal cancer cell proliferation and invasion in vitro and in vivo. RNF6 may activate the JAK/STAT3 pathway and increase pSTAT3 levels by inducing the ubiquitination and degradation of SHP-1. Conclusions: Genomic amplification drives RNF6 overexpression in colorectal cancer. RNF6 may be a novel biomarker in colorectal carcinogenesis, and RNF6 may increase pSTAT3 level via promoting SHP-1 ubiquitylation and degradation. Targeting the RNF6/SHP-1/STAT3 axis provides a potential therapeutic option for RNF6-amplified tumors. (C) 2017 AACR.