circYap inhibits oral squamous cell carcinoma by arresting cell cycle

Circular RNAs (circRNAs) involve in the development and progression of tumour. The mechanism of circRNAs in oral squamous cell carcinoma (OSCC) has remained unclear. This study aimed to investigate the role of circular Yes-associated protein (circYap) in OSCC.

Quantification reverse transcription-polymerase chain reaction (qRT-PCR) was applied to measure circYap expression in patients with OSCC tissues and cells. Flow cytometry was performed to evaluate cell cycle. circYap interaction with CDK4 was detected by RNA immunoprecipitation (RIP) and RNA pull-down. The interaction of Cyclin D1 and CDK4 was determined using co-immunoprecipitation (co-IP).

We showed that circYap expression was downregulated in OSCC tissues. Using small interfering circular (Si-circYap) and overexpression plasmid, we found that circYap overexpression inhibited proliferation and arrested cell cycle in OSCC cells, while, circYap knockdown yielded the opposite result. Cyclin D1/CDK4 complexes and nuclear translocation is essential for cell cycle progression. We found that CDK4 interacted with circYap was increased when circYap overexpression, meanwhile, Cyclin D1/CDK4 complexes and of nuclear distribution were decreased.

Our findings suggest that circYap impedes progression of OSCC. Overexpression of circYap suppresses proliferation and cell cycle through binding to CDK4 to block formation and nuclear translocation of Cyclin D1/CDK4 complexes. Thus, circYap may serves as a valuable therapeutic target for OSCC.