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 noncoding RNAs (lncRNA) have been observed in various cancer types. Our bioinformatic analysis of existing databases 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 patients with pancreatic cancer was characterized and was associated with clinical outcomes. The nonprotein 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 patients with PDAC. 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 in patients with PDAC.
CONCLUSIONS: Our findings indicate that THAP9-AS1 plays an important role in PDAC growth via enhancing YAP signaling, which in turn also modulates THAP9-AS1 transcription. THAP9-AS1/YAP axis may serve as a potential biomarker and therapeutic target for PDAC treatment. ©2019 American Association for Cancer Research.