Circular RNA CircSLC22A23 Promotes Gastric Cancer Progression by Activating HNRNPU Expression

Abstract

Background: Circular RNAs (CircRNAs) play essential roles in cancer occurrence as regulatory RNAs. However, circRNA-mediated regulation of gastric cancer (GC) remains poorly understood.

Aim: The purpose of this study was to investigate the molecular mechanism of circSLC22A23 (hsa_circ_0075504) underlying GC occurrence.

Methods: CircSLC22A23 levels were first quantified by quantitative real-time reverse transcription-polymerase chain reaction in GC cell lines, 80 paired GC tissues and adjacent normal tissues, and 27 pairs of plasma samples from preoperative and postoperative patients with GC. Then circSLC22A23 was knocked-down with short hairpin RNA to analyze its oncogenic effects on the proliferation, migration, and invasion of GC cells. Finally, circRNA-binding proteins and their downstream target genes were identified by RNA pulldown, mass spectrometry, RNA immunoprecipitation, quantitative real-time reverse transcription-polymerase chain reaction, and Western blot assays.

Results: CircSLC22A23 was found to be highly expressed in GC cells, GC tissues, and plasma from GC patients. Knockdown of circSLC22A23 inhibited GC cell proliferation, migration and invasion. RNA pulldown and RNA immunoprecipitation assays verified the interaction between circSLC22A23 and heterogeneous nuclear ribonucleoprotein U (HNRNPU). Knockdown of circSLC22A23 decreased HNRNPU protein levels. Moreover, rescue assays showed that the tumor suppressive effect of circSLC22A23 knockdown was reversed by HNRNPU overexpression. Finally, epidermal growth factor receptor (EGFR) was found to be one of the downstream target genes of HNRNPU that was up regulated by circSLC22A23.

Conclusion: CircSLC22A23 regulated the transcription of EGFR through activation of HNRNPU in GC cells, suggesting that circSLC22A23 may serve as a potential therapeutic target for the treatment of GC.

Keywords: Gastric cancer; Gene regulation; RNA-binding protein; RNAs; SLC22A23.