Downregulation of miR-193a/b-3p during HPV-induced cervical carcinogenesis contributes to anchorage-independent growth through PI3K-AKT pathway regulators

Abstract

Cervical cancer is caused by a persistent infection with high-risk types of human papillomavirus (HPV) and an accumulation of (epi)genetic alterations in the host cell. Acquisition of anchorage-independent growth represents a critical hallmark during HPV-induced carcinogenesis, thereby yielding the most valuable biomarkers for early diagnosis and therapeutic targets. In a previous study, we found that miR-193a-3p and miR-193b-3p were involved in anchorage-independent growth. This study aimed to delineate the role of miR-193a/b-3p in HPV-induced carcinogenesis and to identify their target genes related to anchorage-independent growth. Cell viability and colony formation were assessed in SiHa cancer cells and HPV-16 and -18 immortalized keratinocytes upon miR-193a/b-3p overexpression. Both microRNAs reduced cell growth of all three cell lines in low-attachment conditions and showed a minor effect in adherent conditions. Online target-predicting programs and publicly available expression data were used to find candidate messenger RNA (mRNA) targets of miR-193a/b-3p. Seven targets showed reduced mRNA expression upon miR-193a/b-3p overexpression. For three targets, Western blot analysis was also performed, all showing a reduced protein expression. A direct interaction was confirmed using luciferase assays for six genes: LAMC1, PTK2, STMN1, KRAS, SOS2, and PPP2R5C, which are phosphatidylinositol 3-kinase/protein kinase B (PI3K-AKT) regulators. All six targets were overexpressed in cervical cancers and/or precursor lesions. Together with an observed downregulation of phosphorylated-AKT upon miR-193a/b-3p overexpression, this underlines the biological relevance of miR-193a/b-3p downregulation during HPV-induced cervical carcinogenesis. In conclusion, the downregulation of miR-193a-3p and miR-193b-3p is functionally involved in the acquisition of HPV-induced anchorage independence by targeting regulators of the PI3K-AKT pathway.

Keywords: HPV-induced carcinogenesis; anchorage-independent growth; cervical cancer; miR-193a-3p; miR-193b-3p.