Targeted degradation of the HPV oncoprotein E6 reduces tumor burden in cervical cancer

Abstract

Human papillomavirus (HPV) remains a global health burden, yet there are no targeted therapies for HPV-related cancers. The HPV E6 protein is essential for tumorigenesis and immune evasion, making it an attractive target for antiviral drug development. In this study, we developed an E6-targeting proteolysis targeting chimera (PROTAC) that inhibits the growth of HPV⁺ tumors. To develop E6 antagonists, we generated a panel of nanobodies targeting HPV16 E6 protein. Nanobody A5 was fused to Von Hippel-Lindau protein to generate a PROTAC that degrades E6 (PROTAC^E6). Mutational rescue experiments validated E6 degradation via the CRL2^VHL E3 ligase. To deliver PROTAC^E6, we used a clinically viable DNA vaccine, which offers the advantages of localized PROTAC^E6 expression and low production costs compared to protein- or viral-based therapies. Intralesional administration of the PROTAC^E6 reduced tumor burden in an immunocompetent mouse model of HPV⁺ cancer. The PROTAC^E6 inhibitory effect was abrogated by CD4⁺ and CD8⁺ T cell depletion, indicating that the antitumor function of the PROTAC^E6 relies in part on host immune responses. These results demonstrate that E6 degradation inhibits its oncogenic function and stimulates an immune response in HPV⁺ tumors, opening new opportunities for virus-specific therapies in the treatment of HPV-related cancers.

Keywords: E6; HPV; antiviral; bioPROTAC; biologics; cancer; nanobody; oncoproteins.