The Function And Mechanism Of MicroRNA 205-5p In The Pathogenesis Of Nasopharyngeal Carcinoma

Background and objective: It is becoming increasingly evident that aberrantly expressed micro RNAs(miRNAs)play crucial roles in numerous neoplasms by regulating multiple tumor-related target genes.The miRNA-205(miR-205)has been shown to be involved in the development and progression of various tumors.However,the role of miR-205 remains controversial since it acted either as a tumour suppressor or an oncogene in the pathogenesis of different types of tumors.Several previous studies showed that miR-205 was up-regulated in nasopharyngeal carcinoma(NPC)tissues,suggesting that miR-205 may be involved in the pathogenesis of NPC.However,the function and mechanism of miR-205 in NPC tumorigenesis remain unclear.The aim of this study is to explore the role and mechanism of miR-205-5p to be involved in NPC by in vivo and in vitro experiments,so as to provide experimental evidence for clarifying the oncogenic mechanism of miR-205-5p in NPC.Methods: q RT-PCR was used to detect the expression levels of miR-205-5p in 40 NPC tissues and 22 nasopharyngitis tissues.NPC cell line HONE1 was transfected with miR-205-5p mimics,inhibitor,mimics negative control or inhibitor negative control.The function of miR-205-5p in cell proliferation,apoptosis,migration and invasion was assessed via CCK-8 assay,flow cytometry,wound healing assay and Transwell migration assay,and Matrigel invasion assay,respectively.Two potential target genes of miR-205-5p,tumor suppressor genes PTEN(phosphatase and tensin homolog)and Smad4,was predicted by software.The transcripts and proteins of PTEN and Smad4 in transfeted cells and control cells were quantified by q RT-PCR and western blot,respectively.The transcripts and proteins of protein kinase B(AKT),which is the downstream gene of PTEN,were also evaluated.Results:(1)Compared with nasopharyngitis tissues,the expression of miR-205-5p was up-regulated in NPC tissues with significant difference(P<0.05).(2)Compared with control cells,overexpression of miR-205-5p was induced in miR-205-5p mimics transfected cells and down-regulated expression of miR-205-5p was induced in miR-205-5p inhibitor transfected cells.(3)Overexpression of miR-205-5p increased the proliferation,migration and invasion of HONE1(P<0.05),while low expression of miR-205-5p suppressed the proliferation,migration and invasion of HONE1(P<0.05).Different to cell proliferation,migration and invasion,deregulation of miR-205-5p had no significant influence to cell apoptosis(P>0.05).(4)Overexpression of miR-205-5p down-regulated the transcription and protein expression of PTEN and Smad4(P<0.05),while low expression of miR-205-5p up-regulated the transcription and protein expression of PTEN and Smad4(P<0.05).Although deregulation of miR-205-5p did not affect the transcription and protein expression of AKT(P>0.05),the phosphate AKT(p-AKT)was up-regulated in miR-205-5p mimics transfected cells and down-regulated in miR-205-5p inhibitor transfected cells(P <0.05).Conclusion:(1)miR-205-5p is up-regulated in NPC tissues in vivo,and overexpression of miR-205-5p promotes the proliferation,migration and invasion of NPC cell line in vitro,suggesting that miR-205-5p acts as an oncogene to be involved in the pathogenesis of NPC.(2)miR-205-5p may promote the proliferation,migration and invasion of NPC cell lines via regulating the PTEN/AKT pathway and the expression of Smad4.