RASAL2 promotes tumor progression through LATS2/YAP1 axis of hippo signaling pathway in colorectal cancer

Yi Pan,Johnny Sheung Him Kwan,Lau Ying Chung,Kwok Wai Lo,Simon Siu Man Ng,Wing Po Chak,Ka Fai To,Joanna Hung Man Tong,Anthony Wing Hung Chan,Jun Yu,Wei Kang,Raymond Wai Ming Lung,Ka Yee Tin,Tony Wing Chung Mak,Feng Wu

doi:10.1186/s12943-018-0853-6

Yi Pan, Johnny Sheung Him Kwan + Show 13 more

Open Access

https://doi.org/10.1186/s12943-018-0853-6

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Abstract

BackgroundPatients with colorectal cancer (CRC) have a high incidence of regional and distant metastases. Although metastasis is the main cause of CRC-related death, its molecular mechanisms remain largely unknown.MethodsUsing array-CGH and expression microarray analyses, changes in DNA copy number and mRNA expression levels were investigated in human CRC samples. The mRNA expression level of RASAL2 was validated by qRT-PCR, and the protein expression was evaluated by western blot as well as immunohistochemistry in CRC cell lines and primary tumors. The functional role of RASAL2 in CRC was determined by MTT proliferation assay, monolayer and soft agar colony formation assays, cell cycle analysis, cell invasion and migration and in vivo study through siRNA/shRNA mediated knockdown and overexpression assays. Identification of RASAL2 involved in hippo pathway was achieved by expression microarray screening, double immunofluorescence staining and co-immunoprecipitation assays.ResultsIntegrated genomic analysis identified copy number gains and upregulation of RASAL2 in metastatic CRC. RASAL2 encodes a RAS-GTPase-activating protein (RAS-GAP) and showed increased expression in CRC cell lines and clinical specimens. Higher RASAL2 expression was significantly correlated with lymph node involvement and distant metastasis in CRC patients. Moreover, we found that RASAL2 serves as an independent prognostic marker of overall survival in CRC patients. In vitro and in vivo functional studies revealed that RASAL2 promoted tumor progression in both KRAS/NRAS mutant and wild-type CRC cells. Knockdown of RASAL2 promoted YAP1 phosphorylation, cytoplasm retention and ubiquitination, therefore activating the hippo pathway through the LATS2/YAP1 axis.ConclusionsOur findings demonstrated the roles of RASAL2 in CRC tumorigenesis as well as metastasis, and RASAL2 exerts its oncogenic property through LATS2/YAP1 axis of hippo signaling pathway in CRC.

Highlights

Patients with colorectal cancer (CRC) have a high incidence of regional and distant metastases
RASAL2 copy number gains and overexpression were observed in CRC By high-resolution microarray-based comparative genomic hybridization, we found recurrent gains of chromosome 1q in 5 out of 8 metastatic CRC patients (Additional file 1: Table S4)
We examined the mRNA expression level of RASAL2 in a panel of CRC cell lines including 5 lines established from early stage CRC (LS 180, CL-14, HT-29, SW480 and Caco-2) and 4 lines from advanced stage CRC (LoVo, SW620, HCT 116 and DLD-1)

Summary

Introduction

Patients with colorectal cancer (CRC) have a high incidence of regional and distant metastases. Metastasis is the main cause of CRC-related death, its molecular mechanisms remain largely unknown. Despite an increase in its public awareness, colorectal cancer (CRC) remains one of the most common cancers and the second leading cause of cancer-related death globally [1, 2]. Some genes involved in cell growth, survival, adhesion, invasion and angiogenesis have already been suggested to contribute to tumor progression in CRC [3]. A full understanding of the key elements dictating the oncogenic phenotype as well as the molecular events supporting tumor progression undoubtedly helps discover new drugs and ways to prevent CRC. Growing evidence suggests that hippo pathway dysregulation is associated with CRC development [5,6,7,8]. The gene that has received the most attention in the literature

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