LncRNA THAP9-AS1 promotes pancreatic ductal adenocarcinoma growth and leads to a poor clinical outcome via sponging miR-484 and interacting with YAP

Purpose: Long non-coding RNAs (lncRNAs) has been observed in various cancer types. Our bioinformatic analysis of existing database demonstrated overexpression of lncRNA THAP9-AS1 in pancreatic ductal adenocarcinoma (PDAC). We aimed to investigate the roles and mechanisms of THAP9-AS1 in PDAC. Experimental Design: The overexpression of THAP9-AS1 in samples of pancreatic cancer patients was characterized and was associated with clinical outcomes. The non-protein coding property of the THAP9-AS1 was verified. Various in vitro and in vivo experiments were performed to investigate the interaction between THAP9-AS1 and YAP signaling. Results: We demonstrated that lncRNA THAP9-AS1 is overexpressed in PDAC in multiple patient sample sets, which is significantly associated with poor outcome of PDAC patients. THAP9-AS1 promotes PDAC cells growth both in vitro and in vivo. THAP9-AS1 exerts its effects via enhancing YAP signaling. Ectopic YAP expression overcame the effects of THAP9-AS1 knockdown. Inversely, YAP knockdown diminished the effects of THAP9-AS1 overexpression. THAP9-AS1 acts as a competing endogenous RNA for miR-484, leading to YAP upregulation. Moreover, THAP9-AS1 binds to YAP protein and inhibits the phosphorylation mediated inactivation of YAP by LATS1. Reciprocally, YAP/TEAD1 complex promotes THAP9-AS1 transcription to form a feed-forward circuit. Importantly, THAP9-AS1 level positively correlates with YAP expression in PDAC tissues. YAP overexpression also predicts a poor outcome of PDAC patients. Conclusions: Our findings indicate that THAP9-AS1 plays an important role in PDAC growth via enhancing YAP signaling which in return also modulates THAP9-AS1 transcription. THAP9-AS1/YAP axis may serve as a potential biomarker and therapeutic target for PDAC treatment.