Human papillomavirus type 16 reduces the expression of microRNA-218 in cervical carcinoma cells

Human papillomaviruses (HPVs) are involved in the pathogenesis of cancer of the cervix (CaCx). MicroRNA (miRNA) expression analysis using Ambion (Austin, TX, USA) arrays showed that three miRNAs were over-expressed and 24 underexpressed in cervical cell lines containing integrated HPV-16 DNA compared to the normal cervix. Furthermore, nine miRNAs were overexpressed and one underexpressed in integrated HPV-16 cell lines compared to the HPV-negative CaCx cell line C-33A. Based on microarray and/or quantitative realtime PCR and northern blot analyses, microRNA-218 (miR-218) was specifically underexpressed in HPV-positive cell lines, cervical lesions and cancer tissues containing HPV-16 DNA compared to both C-33A and the normal cervix. Expression of the E6 oncogene of high-risk HPV-16, but not that of low-risk HPV-6, reduced miR-218 expression, and conversely, RNA interference of E6/E7 oncogenes in an HPV-16-positive cell line increased miR-218 expression. We also demonstrate that the epithelial cell-specific marker LAMB3 is a target of miR-218. We also show that LAMB3 expression is increased in the presence of the HPV-16 E6 oncogene and this effect is mediated through miR-218. These findings may contribute to a better understanding of the molecular mechanisms involved in cervical carcinogenesis.