The roles of E6-AP and MDM2 in p53 regulation in human papillomavirus-positive cervical cancer cells

The p53 tumor suppressor is regulated by the MDM2 oncoprotein through a neg ative feedback mechanism. MDM2 promotes the ubiquitination and proteasome-d ependent degradation of p53, possibly by acting as a ubiquitin ligase, In c ervical cancer cells containing high-risk human papillomaviruses (HPV), p53 is also targeted for degradation by the HPV E6 oncoprotein in combination with the cellular E6-AP ubiquitin ligase, In this report, we describe the i dentification of efficient antisense oligonucleotides against human E6-AP, The roles of MDM2 and E6-AP in p53 regulation were investigated using a nov el E6-AP antisense oligonucleotide and a previously characterized MDM2, ant isense oligonucleotide. In HPV16-positive and HPV-18 positive cervical canc er cells, inhibition of E6-AP, but not MDM2, expression results in signific ant induction of p53, In HPV-negative tumor cells, p53 is activated by inhi bition of MDM2 but not E6-AP, Furthermore, treatment with both E6-AP and MD M2 antisense oligonucleotides in HPV-positive cells does not lead to furthe r induction of p53 over inhibition of E6-AP alone. Therefore, E6-AP-mediate d degradation is dominant over MDM2 in cervical cancer cells but does not h ave a significant role in HPV-negative cells.