Christine Kottaridi

HPV16 E6 Oncogene Contributes to Cancer Immune Evasion by Regulating PD-L1 Expression through a miR-143/HIF-1a Pathway

Human Papillomaviruses have been associated with the occurrence of cervical cancer, the fourth most common cancer that affects women globally, while 70% of cases are caused by infection with the high-risk types HPV16 and HPV18. The integration of these viruses’ oncogenes E6 and E7 into the host’s genome affects a multitude of cellular functions and alters the expression of molecules. The aim of this study was to investigate how these oncogenes contribute to the expression of immune system control molecules, using cell lines with integrated HPV16 genome, before and after knocking out E6 viral gene using the CRISPR/Cas9 system, delivered with a lentiviral vector. The molecules studied are the T-cell inactivating protein PD-L1, its transcription factor HIF-1a and the latter’s negative regulator, miR-143. According to our results, in the E6 knock out (E6KO) cell lines an increased expression of miR-143 was recorded, while a decrease in the expression of HIF-1a and PD-L1 was exhibited. These findings indicate that E6 protein probably plays a significant role in enabling cervical cancer cells to evade the immune system, while we propose a molecular pathway in cervical cancer, where PD-L1’s expression is regulated by E6 protein through a miR-143/HIF-1a axis.

Disruption Events in the HPV18 E1 and E2 Genes in Precancerous Cervical Lesions

Human papillomavirus 18 (HPV18) is the second most oncogenic high-risk HPV genotype, after HPV16, and is responsible for about 15% of cervical cancer cases worldwide. The integration of high-risk HPV DNA into the host genome leads to the disruption of the E1 and/or E2 genes, which is considered a risk factor for viral-induced carcinogenesis. This study examined the disruption events of HPV18 E1 and E2 genes in precancerous cervical lesions to investigate the rates and sites of gene disruption in the Greek population. The complete E1 and E2 genes were amplified using three and four overlapping primer sets, respectively. Extensive analysis revealed that the disruption/deletion events of the E1 and E2 genes were detected in all grades of cytology-determined lesions, with high frequency. E2 gene disruption was significantly related to LSIL+ cases (Fisher’s exact test, p = 0.022). No significant association was found in the analysis of the E1 gene. Additionally, no preferential sites of E1/E2 gene disruption were detected. This is the first study to provide evidence of disruption events of the HPV18 E1 gene. The data from the current analysis suggest that disruption of the E2 gene could be a significant marker for the progression of cytology-determined cervical dysplasia. However, future studies are required to evaluate whether different geographic populations have particular profiles regarding the rates and sites of gene disruption to further determine population-specific biomarkers.