Emerging roles of circular RNA hsa_circ_0000064 in the proliferation and metastasis of lung cancer

Circular RNAs (circRNAs), a novel class of widespread and diverse endogenous RNAs, can regulate gene expression in mammals. CircRNAs have recently been identified as microRNA sponges and involved in the development of some human diseases. However, the role of circRNAs in the process of tumorigenesis and development of lung cancer remains vague. The purpose of this study is to investigate the role of circRNAs in the lung cancer. In this study, we chose hsa_circ_0000064 as a targeted circRNA to investigate its clinical significances in lung cancer patients. The result indicated that hsa_circ_0000064 was up-regulated in lung cancer tissues and lung cancer cell lines (A549 and H1229). Moreover, its aberrant expression was correlated with several clinical characteristics, including T stage, lymphatic metastasis, and TNM stage. Fluorescence in situ hybridization detected that hsa_circ_0000064 was mostly located in the cytoplasm in A549 and H1229 cells. In addition, knockdown of hsa_circ_0000064 with siRNA dramatically attenuated the proliferation, blocked cell cycle progression, and promoted cell apoptosis. Western blot analysis showed that the protein levels of caspase-3, caspase-9, bax, p21, CDK6 and cyclin D1 significantly restrained by si-hsa_circ_0000064, while the expression of bcl-2 notably increased in A549 and H1229 cells. Further, si-hsa_circ_0000064 also abated migration and invasion activities of A549 and H1229 cells, which may be associated with reduced expressions of MMP-2 and MMP-9. In general, our data suggest that hsa_circ_0000064 represents a novel potential biomarker and therapeutic target of lung cancer.