[Circular RNA CircHIPK3 Promotes NCI-H1299 and NCI-H2170 Cell Proliferation through miR-379 and its Target IGF1].

BACKGROUND: It has been proven that the circular RNA, possessing a stable covalently closed continuous loop, is a type of RNA molecule which is expressed widespread in mammals. The circular RNA circHIPK3 is abundantly expressed in hepatocellular carcinoma (HCC) and promotes tumourgenesis. However, a role for circHIPK3 has not been systematically examined in non-small cell lung cancer (NSCLC). In this study, we investigated whether circHIPK3 has an effect on cell proliferation in the NSCLC cell lines NCI-H1299 and NCI-H2170 and the underlying molecular mechanisms.

METHODS: The expression of circHIPK3 was measured by real-time PCR in NSCLC cell lines. Nuclear mass separation experiment was used to detect the location of circHIPK3 in cells. The gain and loss function experiments were used to examine the proliferation of NCI-H1299 and NCI-H2170 cells by Cell Counting Kit-8 (CCK-8) and the colony formation assays. Then, circHIPK3 was cloned into the downstream of the luciferase reporter gene which activity was detected to verify whether miR-379 could bind with circHIPK3 or IGF1 mRNA. The protein level of IGF1 was detected by Western blot and ELISA in circHIPK3 overexpressed/knock-down NCI-H1299 and NCI-H2170 cells.

RESULTS: CircHIPK3 was generally expressed in six kinds of NSCLC cells lines we detected, and the expression level was highest in H2170 and lowest in H1299. Overexpression of circHIPK3 obviously promoted NCI-H1299 cell proliferation and knock-down of circHIPK3 inhibited NCI-H2170 cell proliferation. In the luciferase assay, miR-379 was observed to sequester circHIPK3 and IGF1 mRNA with potential binding sites. Furthermore, we found that the overexpression of circHIPK3 could increase the expression levels of IGF1 and knock-down reduced it. Moreover, up-regulation of miR-379 rescued the phenotype induced by overexpression of circHIPK3.

CONCLUSIONS: CircHIPK3 could promote cell proliferation by a circHIPK3/miR-379 pathway in NCI-H1299 and NCI-H2170 cells and might be a potential tumor biomarker for NSCLC.
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