STX5 Inhibits Hepatocellular Carcinoma Adhesion and Promotes Metastasis by Regulating the PI3K/mTOR Pathway

Bin Zhang; Ziyin Zhao; Youpeng Wang; Tingting Guo; Mingyang He; Ge Guan; Pai Peng; Jinzhen Cai; Bingyuan Zhang; Xutao Liu; Qiaoling Song

doi:10.14218/JCTH.2022.00276

STX5 Inhibits Hepatocellular Carcinoma Adhesion and Promotes Metastasis by Regulating the PI3K/mTOR Pathway

J Clin Transl Hepatol. 2023 Jun 28;11(3):572-583. doi: 10.14218/JCTH.2022.00276. Epub 2023 Jan 9.

Authors

Bin Zhang^{1

2}, Ziyin Zhao², Youpeng Wang³, Tingting Guo³, Mingyang He², Ge Guan², Pai Peng², Jinzhen Cai², Bingyuan Zhang³, Xutao Liu⁴, Qiaoling Song¹

Affiliations

¹ Key Laboratory of Marine Drugs, Ministry of Education School of Medicine & Pharmacy, Ocean University of China, Qingdao, Shandong, China.
² Organ Transplantation Center, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China.
³ Department of Hepatobiliary and Pancreatic Surgery, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, China.
⁴ Samueli School of Engineering, University of California Los Angeles, Los Angeles, CA, USA.

Abstract

Background and aims: Syntaxin 5 (STX5) is a member of the syntaxin or target-soluble SNAP receptor (t-SNARE) family and plays a critical role in autophagy. However, its function and molecular mechanism in tumor cell migration are still unknown. The role of STX5 in influencing hepatocellular carcinoma (HCC) is an important topic in our research.

Methods: By using quantitative reverse transcription polymerase chain reaction (qPCR), western blotting, and immunohistochemical analysis of RNA and protein in tissues, we comprehensively evaluated data sets from public databases and clinical patient cohorts for STX5. The correlation of STX5 expression with the clinicopathological characteristics of HCC patients were assessed. In addition, we predicted signal pathways from differentially expressed genes (DEGs) and the Cancer Genome Atlas (TCGA) databases, and confirmed the prediction using integrated transcriptome and RNA-seq. We further investigated the underlying mechanisms of STX5 in the migration and adhesion of HCC cells both in vitro and in vivo.

Results: In the TCGA dataset and our patient cohort, STX5 levels were significantly higher in HCC tissues than in adjacent normal liver tissues. At the same time, high expression of STX5 predicted worse prognosis in patients with liver cancer. High expression of STX5 indicates the decrease of adhesion and the increase of migration of HCC cells, and the conversion of epithelial-mesenchymal transition (EMT) in vitro via PI3K/mTOR pathway activation. Conversely, when Sirolimus, a phosphoinositide 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) inhibitor acts on cells simultaneously, STX5 overexpression-mediated enhancement of HCC metastasis is reversed. Double-negative regulation of STX5 and mTOR further enhanced the inhibitory effect of STX5 on HCC metastasis. In vivo, STX5 knockdown inhibited the metastasis of HCC cells.

Conclusions: Our study demonstrates a novel research result that STX5 promotes HCC metastasis through PI3K/mTOR pathway. We believe that combined inhibition of STX5 and mTOR is a potential treatment for effectively prolonging patient survival and inhibiting HCC metastasis.

Keywords: Epithelial-mesenchymal transition; Hepatocellular carcinoma; PI3K/mTOR; Syntaxin 5.