Characterization of a novel regulator of AKT/mTOR signaling in gastric cancer.

Abstract

68 Background: Gastric cancer (GC) is a leading cause of cancer-related death with poor prognosis and “one-size fits all approach”. Dysregulation of PI3K/Akt/mTOR pathway is a common event in GC with PIK3CAmutations reported to correlate with poor prognosis. With prognosis far from satisfactory, we aimed to identify novel surrogate biomarkers. We hypothesize the role of DP103, a DEAD-box RNA helicase, as a novel surrogate biomarker for GC by regulating the PI3K/Akt/mTOR pathway. Additionally, we shed light on high DP103 GC cells responding to Akt/mTOR dual inhibitor treatment, indicating its potential role as a surrogate biomarker for GC treatment. Methods: Tissue microarray data from GC cohorts were used in correlation analysis between DP103 and PIK3CA expression. Effect of DP103 knockdown was assessed on functions downstream of PI3K/Akt/mTOR pathway including apoptosis, autophagy and cell invasion. Next, DP103 depletion studies were done and PI3K/Akt/mTOR pathway proteins were assessed. Further, immunoprecipitation studies assessed for DP103 interacting partners from PI3K/Akt/mTOR pathway in GC. Results: Herein, we provide clinical evidence of DP103 upregulation in GC patients’ tissues compared to normal gastric tissues. Additionally, we showed a positive correlation between DP103 and PIK3CA expression in GC patients’. DP103 knockdown resulted in decrease in cell invasion and an increase in apoptosis and autophagy. Further, decrease in phosphorylation of PI3K/Akt/mTOR pathway proteins was observed with DP103 depletion. Mechanistically, we discovered a novel physical interaction between DP103 and PI3K in GC. Conclusions: Here we summarized, current understanding of DP103 regulating PI3K/Akt/mTOR pathway in GC and discuss potential use as a new surrogate biomarker for better clinical application.