HPV18 E6 and E7 genes affect cell cycle, pRB and p53 of cervical tumor cells and represent prominent candidates for intervention by use peptide nucleic acids (PNAs)

Approximately 100% of cervical carcinomas are causally linked to infections with high-risk human papillomaviruses (HPVs), whose oncogenicity has been assigned to the continued expression of two early viral genes, E6 and E7. Reversal of the transformed phenotype by inhibiting E6/E7 gene expression therefore provides a suitable goal for tumor therapy. We established an application controlling the E6/E7 expression of the HPV type 18, by using viral gene directed peptide nucleic acids (PNAs). One consequence was the complete change in growth to a stagnated behavior of the HPV 18 positive HeLa-S cells. With flow cytometry, we investigated changes in the cell cycle and expression of the pRB (retinoblastoma) and p53 genes acting as antagonists to E6 and E7. We realized that application of PNAs via intracellular cleavable conjugated peptide carriers mediates specific inhibitory effects and we showed that the combined E6/E7-directed PNA-application mediated a clear morphological change from suspension to adherend state and the cells stopped growth. These data could demonstrate a promising approach for development of new ‘anti-gene therapeutics’ against papillomavirus-induced human cancers.