Circ₀104541 Promotes Migration And Invasion Of Cervical Cancer By Sponging MiR-4429/miR-320a And Regulating FoxM1

Cervical cancer is the fourth most common cancer in the world and the leading cause of death for women.In China,cervical cancer is also one of the most common malignant tumors among women in 2015,with 989,000 new cases and 305,000 deaths.Among the pathological types of cervical cancer,squamous cell carcinoma and adenocarcinoma are the most common histological subtypes,accounting for 70% and 25% of cervical cancer,respectively.Cervical cancer has a high incidence of invasion and mortality.Although we know that the main ways of metastasis of cervical cancer are adjacent tissue metastasis,lymphatic metastasis and blood metastasis.However,its specific mechanism of invasion and transfer is still unclear.Therefore,it is necessary to explore the exact mechanism of cervical cancer progression for finding new therapeutic targets.Referring to the literature,it was found that fork box M1?FOXM1?is a transcription factor of fork box protein superfamily.As a classical proliferation-related transcription factor,FOXM1 can be specifically expressed in proliferative cervical cancer cells,making the cell cycle G1 to S,G2 to M,and promoting cell mitosis.Many literatures have reported that over-expression of Foxm1 promotes the migration and invasion of cervical cancer cells.However,the underlying molecular mechanism of FoxM1 overexpression remains unclear.Micro-RNA?microRNA?: Micro RNA is a very important small non-coding RNA.Its length is generally 19-25 nucleotide fragments.Current studies have shown that microRNAs negatively regulate the expression of target genes through complementary or incomplete complementarity with the 3'untranslated region?3'UTR?of the RNA,leading to degradation or translation inhibition of the RNA.In this study,bioinformatics analysis showed that both microRNAs 320 A and microRNAs 4429 had FoxM1 3'UTR binding sites,suggesting that microRNAs 320 A and microRNAs 4429 may negatively regulate FoxM1 expression in cervical cancer.Cyclic RNA?circular RNA?is a group of naturally occurring endogenous non-coding RNA,whose length is hundreds to thousands of nucleotides.Current studies have shown that cyclic RNA acts as a competitive endogenous RNA binding to microRNAs to regulate gene expression.However,the biological role of cyclic RNA in cervical cancer has rarely been reported.In this study,circRNA sequencing results showed that the expression of circ₀104541 in cervical cancer tissues was significantly higher than that in adjacent normal tissues,which was confirmed by qRT-PCR results.In the functional mechanism study,up-regulation of circ₀104541 promoted the migration and invasion of cervical cancer cells,while down-regulation of circ₀104541 inhibited the migration and invasion of SiHa and HeLa cells.In addition,luciferase reporter gene assay and RNA binding protein immunoprecipitation assay?RIP?showed that circ₀104541 could directly regulate the expression of microRNA-4429/microRNA-320 a.At the same time,the experiment proved that microRNA-4429/microRNA-320 a could bind with FoxM1 mRNA 3'UTR to regulate FoxM1 expression.Therefore,we conclude that circ₀104541 can promote FoxM1 expression by binding to microRNA-4429/microRNA-320 a.This study provides a new theoretical basis for the study of the occurrence and development of cervical cancer.circ₀104541 can be used as a potential biomarker for the progress of cervical cancer disease and provide a promising therapeutic target for targeted therapy.Background/AimsCircular RNAs?circRNAs?are a new class of non-coding RNA following the microRNA and long non-coding RNA,and play a crucial role in the development and progression of various cancers.However,the detail functions of circRNAs in cervical cancer have seldom been reported.This study was aimed to explore the biological function of circ₀104541 and illuminate the underlying molecular mechanisms in the progression of cervical cancer.MethodsCircRNA sequence was applied to detect the differentially expressed circRNAs between cervical cancer tissues and adjacent normal tissues.Quantitative RT-PCR was used to determine the expression of circ₀104541,miR-4429,miR-320 a and FoxM1.The abilities of cell migration and invasion were tested by wound healing assay and transwell assay were performed.The luciferase reporter assay and RIP assay were employed to clarify the direct relationship between circ₀104541 and miR-4429/miR-320 a,and the regulation of miR-4429/miR-320 a on FoxM1 was studied,as well.The rescue of miR-4429/miR-320 a on the regulation of circ₀104541 on FoxM1 was investigated.ResultsThe expression of circ₀104541 was remarkably higher in cervical cancer tissues than that in the adjacent normal tissues.The down-regulated circ₀104541 evidently inhibited the migration and invasion of cervical cancer cells in vitro,while up-regulated circ₀104541 significantly promoted the migration and invasion of cervical cancer cells in vitro.The luciferase reporter assay and RIP assay showed that circ₀104541 could directly bind to and sponge miR-4429/miR-320 a.MiR-4429 and miR-320 a both inhibited the expression of FoxM1 through directly binding to 3'UTR of FoxM1 mRNA.In addition,the enforced expression of miR-4429 and miR-320 a suppressed the migration and invasion of cervical cancer cells,and the knockdown of miR-4429 and miR-320 a both promoted and the ability of migration and invasion.Furthermore,miR-4429 and miR-320 a could reverse the promotion of circ₀104541 on FoxM1 expression and cell migration and invasion.ConclusionsCirc₀104541,highly expressed in cervical cancer tissues,can increase the expression of FoxM1 through competitively binding to miR-4429/miR-320 a,and thus promote cell migration and invasion of cervical cancer.It is suggested that circ₀104541 may serve as a potential biomarker for disease progression of cervical cancer,and provide a promising target for targeted therapy.