The Fusion Circular RNA F-circEA1 Promotes Non-small Cell Lung Carcinoma Progression through ALK Downstream Signaling

Abstract Background Circular RNA has a stable closed structure, which plays an important role in the occurrence and development of tumors. However, there are no reports on the relationship between fusion circular RNA and EML4-ALK variant 1, or their underlying molecular mechanisms in non-small cell lung carcinoma (NSCLC). Methods To test F-circEA1 in NCI-H3122 cells (carrying the EML4-ALK variant 1 gene) by RT-PCR, FISH and Sanger sequencing; To determine cell proliferation with a CCK-8 assay. Transwell experiments were used to detect cell migration and invasion. Cell cycle stage and apoptosis were detected by flow cytometry. The sensitivity of cells to crizotinib was tested using a CCK-8 assay. RT-PCR and western blots were used to measure the expression of EML4-ALK1 and downstream signaling factors associated with ALK. Subcutaneously transplanted tumors were used in nude mice to determine the effect of F-circEA1 on tumor formation and the expression of EML4-ALK1 by immunohistochemistry. Statistical analyses were carried by GraphPad Prism 8.0 and differences between groups were compared using Student's t test. Difference with p value <0.05 is statistically significant.Results F-circEA1 was present both in the cytoplasm and nucleus of NCI-H3122 cells. F-circEA1 was contributed to cell proliferation, metastasis, invasion. F-circEA1 induced cell arrest, promoted cell apoptosis and improved drug sensitivity to crizotinib. After knockdown with F-circEA1, subcutaneously transplanted tumors in nude mice grew slowly, the expression of EML4-ALK1 in tumor tissues decreased significantly. The mRNA and protein levels of EML4-ALK1 decreased after knockdown of F-circEA1 but increased after its overexpression. The protein expression of downstream ALK signaling factors increased after overexpression of F-circEA1, but not at the mRNA level.Conclusions We have confirmed a potential carcinogenenic and therapeutic role for F-circEA1 in NSCLC. Our experimental results may provide a new biomarker, treatment method, and prognostic monitoring index for use in the clinic.