Secretion protein vstm2a is a novel tumor suppressor and associates with colorectal cancer patient survival
Refereed conference paper presented and published in conference proceedings

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AbstractIntroduction: Using genome-wide promoter CpG island screening and RNAsequencing data, we have recently identified that V-set and transmembrane domain containing 2A (VSTM2A) gene, which encodes a 26 kDa protein, was hypermethylated and silenced in colorectal cancer (CRC). However the role of VSTM2A in tumorigenesis has not been evaluated yet. Aims & Methods: VSTM2A methylation status was evaluated by bisulfite genomic sequencing. The biological functions of VSTM2A were investigated in vitro A280 United European Gastroenterology Journal 4(5S) and in vivo. VSTM2A downstream effectors were elucidated by luciferase assay, real-time PCR and Western blot. The clinical impact of VSTM2A was assessed in 263 CRC patients. Results: Full or partial methylation of VSTM2A promoter was found in CRC cell lines and tumor specimens, whilst none or low methylation was detected in the normal colon tissue specimens. Demethylation by 5-aza-2’-deoxycytidine restored VSTM2A expression in silenced CRC cell lines, indicating that promoter methylation contributed to the decrease expression of VSTM2A. VSTM2A mRNA was significantly reduced in all 8 CRC cell lines and in CRC cancer tissues compared with adjacent normal tissues (P<0.05). In keeping with this, VSTM2A protein expression was reduced in CRC tumors compared to their adjacent normal tissues detected by Western blot (P<0.05) and immunohistochemistry analysis (P<0.05). We further evaluated the association between VSTM2A protein expression level and survival of CRC patients by tissue microarray. A survival analysis of 158 CRC patients indicated that high VSTM2A protein expression was significantly correlated with longer overall survival (P<0.05) and disease-free survival (P<0.05). Our functional studies supported a tumor suppressive role of VSTM2A in CRC. Ectopic VSTM2A expression significantly suppressed CRC cell viability (P<0.01) and reduced colony formation (P<0.01). VSTM2A caused G2 phase cell cycle arrest (P<0.01) and induced apoptosis (P<0.01), concomitant with enhanced cell cycle regulators p21 and p27, and pro-apoptotic factors of cleaved caspase 3, caspase 8 and PARP. Subcutaneous tumor xenografts of CRC cells (HCT116 and DLD1) with stable VSTM2A expression in nude mice exhibited significant reduced tumor growth compared with the control cells (P<0.01). We further investigated the molecular mechanisms of VSTM2A in CRC. VSTM2A could be detected in the cell culture supernatant. Inhibition of the cell secretion by Brefeldin A, which prevents secretory protein transport from the endoplasmic reticulum to the Golgi apparatus, inhibited VSTM2A supernatant expression and induced cytosolic accumulation, suggesting a secretory property of VSTM2A. Our results further indicated that secreted VSTM2A could attach to cell plasma membrane evidenced by Immunofluorescence and immunoprecipitation assays, inferring that VSTM2A exerted its biological function in a paracrine manner. Using luciferase reporter screening of 9 signal transduction pathways, we found that VSTM2A significantly inhibited Wnt signaling TOP-Flash luciferase reporter activity (P<0.01). Moreover, VSTM2A suppresses Wnt signaling through inducing beat-catenin phosphorylation and inhibiting Wnt downstream targets c-myc and cyclin D1 expression. Conclusion: Secretory protein VSTM2A is a critical tumor suppressor in colorectal carcinogenesis through inhibiting Wnt signaling by suppressing beta-catenin activation. High VSTM2A protein level was significantly correlated with better CRC patient outcomes.
All Author(s) ListY. Dong, A. Higashimori, W. Kang, Y. Zhang, S. S. Ng, J. Yu
Name of ConferenceUnited European Gastroenterology (UEG) Week 2016
Start Date of Conference15/10/2016
End Date of Conference19/10/2016
Place of ConferenceVienna
Country/Region of ConferenceAustria
Proceedings TitleUnited European Gastroenterology Journal
Volume Number2
Issue NumberSuppl. 1
LanguagesEnglish-United States

Last updated on 2018-18-01 at 08:22