MicroRNA-154-5p regulates the HPV16 E7-pRb pathway in Cervical Carcinogenesis by targeting CUL2

Cervical cancer, induced by persistent HPV infection, has a high mortality rate. The E3 ubiquitin ligase Cullin 2 (CUL2) is critical for HPV16 E7-mediated degradation of retinoblastoma protein (pRb). Dysregulation of microRNAs (miRNAs) is induced during tumorigenesis; however, the association between miRNA networks and CUL2, specific to cervical cancer, remains unknown. Herein, we determined miRNA profiles in cervical cancer tissues using an Affymetrix miRNA array. We found that miR-154-5p was downregulated during cancer progression using real-time quantitative reverse transcription PCR in 130 biopsy specimens. Bioinformatics analysis and dual-luciferase reporter assays indicated that miR-154-5p directly targets the CUL2 3'UTR. To determine the functional consequences of modulating miR-154-5p and CUL2 levels, HPV16-positive cervical cancer cell line (SiHa) was transfected with miR-154-5p mimic, miR-154-5p inhibitor, or CUL2 siRNA. The proliferation, migration, and invasion of transfected cells were evaluated using CCK8 cell counting kit, wound-healing assay, and Transwell invasion assay. Increased miR-154-5p expression promoted significantly reduced SiHa cell proliferation, migration, and invasion, whereas the miR-154-5p inhibitor had the opposite effect. CUL2 silencing had similar effects to those of the miR-154-5p mimic. Consistent with the inverse correlation between miR-154-5p and CUL2 levels, CUL2 silencing also increased pRb expression. To our knowledge, this is the first study to demonstrate that miR-154-5p regulates pRb expression by targeting CUL2 3'UTR, thereby playing a tumor-suppressive role in HPV16 E7-induced cervical carcinogenesis.