SNORA74B gene silencing inhibits gallbladder cancer cells by inducing PHLPP and suppressing Akt/mTOR signaling

Yiyu Qin,Cuixiang Gao,Mingzhe Weng,Zhiwei Quan,Zhengdong Zhang,Yang Fu,Li Meng,Mingzhe Ma,Koulan Han,Xinghua Shi

doi:10.18632/oncotarget.15301

Abstract

Small nucleolar RNAs (snoRNAs) have been implicated in the development of many cancers. We therefore examined the differential expression of snoRNAs between gallbladder cancer (GBC) tissues and matched adjacent non-tumor tissues using expression microarray analysis with confirmation by quantitative real-time PCR (qRT-PCR). Western blot analysis showed that SNORA74B levels were higher in GBC than non-tumor tissues. SNORA74B expression was positively associated with local invasion, advanced TNM stage, CA19-9 level, and Ki67 expression in patients with GBC, while it was negatively associated with expression of PHLPP, an endogenous Akt inhibitor. Moreover, SNORA74B expression was prognostic for overall survival (OS) and disease-free survival (DFS). Functional studies revealed that silencing SNORA74B in GBC cells using sh-SNORA74B suppressed cell proliferation, induced G1 arrest, and promoted apoptosis. Preliminary molecular investigation revealed that SNORA74B silencing inhibited activation of the AKT/mTOR signaling pathway, while increasing PHLPP expression. PHLPP depletion using shRNA abrogated sh-SNORA74B suppression of GBC cell proliferation, indicating that the antitumor effects of SNORA74B silencing were mediated by PHLPP. These findings define the important role of SNORA74B in cell proliferation, cell cycle, and apoptosis of GBC, and suggest that it may serve as a novel target for GBC treatment.

Highlights

gallbladder cancer (GBC) is the most common malignancy of the biliary tract and the fifth most common malignancy of the gastrointestinal tract worldwide [1]
Detailed data are listed in Table 1. qRTPCR results for these 21 Small nucleolar RNAs (snoRNAs) with Fold Change (FC) > 2 or FC < 0.5 indicates SNORA74B, SNORA21, SNORD71A, SNORD38b, SNORD20 and SNORD75 have the highest up-regulation in GBC tissue
Since the initial discovery of C/D box snoRNAU50 involvement in B-cell lymphoma biology, several snoRNAs including SNHG20, SNORD78, and SNORD114-1 have been reported to act as oncogenes in colorectal cancer [7], lung cancer [8], and leukemia [9]

Summary

Introduction

GBC is the most common malignancy of the biliary tract and the fifth most common malignancy of the gastrointestinal tract worldwide [1]. Due to vague symptoms in the early stage, most GBC cases are diagnosed at an advanced stage when nodal involvement, hepatic invasion, and metastatic progression are present, greatly increasing the difficulty of treatment. While it was originally believed that snoRNAs are primarily engaged in the processing of rRNA, recent studies have revealed many unexpected cellular functions for snoRNAs which may change entrenched views of gene expression. The relationship between snoRNAs and tumors has been documented in recent studies. The tumor suppressive role of the SNORD113-1 gene has been confirmed in hepatocellular carcinoma (HCC). SNORD113-1 expression is abnormally downregulated in HCC tissues compared with adjacent non-tumor tissues, and it may suppress growth of HCC cell both in vitro and in vivo [6], demonstrating that snoRNAs may have a dual role in tumor development

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