siRNA targeting of the viral E6 oncogene efficiently kills human papillomavirus-positive cancer cells

The targeted inhibition of antiapoptotic factors in tumour cells may provide a rational approach towards the development of novel anticancer therapies. Using human papillomavirus (HPV)-transformed cells as a model system, we investigated if RNA interference (RNAi)-mediated gene silencing can be employed in order to overcome the apoptosis resistance of cancer cells. We found that both vector-borne and synthetic small interfering (si)RNAs, specifically directed against the antiapoptotic HPV E6 oncogene, restored dormant tumour suppressor pathways in HPV-positive cancer cells that are otherwise inactive in the presence of E6. This ultimately resulted in massive apoptotic cell death, selectively in HPV-positive tumour cells. These findings show that RNAi provides a powerful molecular strategy to inactivate intracellular E6 function efficiently. Moreover, they define E6 as a most promising therapeutic target to eliminate HPV-positive tumour cells specifically by RNAi. Thus, by sequence-specific targeting of antiapoptotic genes, siRNAs may be developed into novel therapeutics that can efficiently correct the apoptosis deficiency of cancer cells.