Edward M. Kennedy, Anand V. R. Kornepati, Michael Goldstein, Hal P. Bogerd, Brigid C. Poling, Adam W. Whisnant, Michael B. Kastan and Bryan R. Cullen
Journal of Virology,Published ahead of print 6 August 2014, doi: 10.1128/JVI.01879-14
High-risk human papillomaviruses (HPVs), including HPV-16 and HPV-18, are the causative agents of cervical carcinomas as well as being linked to several other tumors of the anogenital and oropharyngeal regions. The majority of HPV-induced tumors contain integrated copies of the normally episomal HPV genome that invariably retain intact forms of the two HPV oncogenes E6 and E7. E6 induces degradation of the cellular tumor suppressor p53, while E7 destabilizes the retinoblastoma (Rb) protein. Previous work has shown that loss of E6 function in cervical cancer cells induces p53 expression as well as downstream effectors that induce apoptosis and cell cycle arrest. Similarly, loss of E7 allows increased Rb expression, leading to cell cycle arrest and senescence.
Here, we demonstrate that expression of a bacterial Cas9 RNA-guided endonuclease, together with single guide RNAs (sgRNAs) specific for E6 or E7, is able to induce cleavage of the HPV genome, resulting in the introduction of inactivating deletion and insertion mutations into the E6 or E7 gene. This results in induction of p53 or Rb, leading to cell cycle arrest and eventual cell death. Both HPV-16 and HPV-18-transformed cells were found to be responsive to targeted HPV genome-specific DNA cleavage. These data provide proof of principle for the idea that vector-delivered Cas9/sgRNA combinations could represent effective treatment modalities for HPV-induced cancers.