Identification and characterization of small molecule human papillomavirus E6 inhibitors

ACS Chem Biol. 2014 Jul 18;9(7):1603-12. doi: 10.1021/cb500229d. Epub 2014 Jun 2.

Abstract

Cervical cancer is the sixth most common cancer in women worldwide and the leading cause of women's death in developing countries. Nearly all cervical cancers are associated with infection of the human papillomavirus (HPV). This sexually transmitted pathogen disrupts the cell cycle via two oncoproteins: E6 and E7. Cells respond to E7-mediated degradation of pRB by upregulating the p53 tumor suppressor pathway. However, E6 thwarts this response by binding to the cellular E6-Associating Protein (E6AP) and targeting p53 for degradation. These two virus-facilitated processes pave the way for cellular transformation. Prophylactic HPV vaccines are available, but individuals already infected with HPV lack drug-based therapeutic options. To fill this void, we sought to identify small molecule inhibitors of the E6-E6AP interaction. We designed an ELISA-based high throughput assay to rapidly screen compound libraries, and hits were confirmed in several orthogonal biochemical and cell-based assays. Over 88,000 compounds were screened; 30 had in vitro potencies in the mid-nanomolar to mid-micromolar range and were classified as validated hits. Seven of these hits inhibited p53 degradation in cell lines with HPV-integrated genomes. Two compounds of similar scaffold successfully blocked p53 degradation and inhibited cell proliferation in cells stably transfected with E6. Together, these studies suggest that small molecules can successfully block E6-dependent p53 degradation and restore p53 activity. The compounds identified here constitute attractive starting points for further medicinal chemistry efforts and development into beneficial therapeutics.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alphapapillomavirus / drug effects
  • Alphapapillomavirus / physiology*
  • Anticarcinogenic Agents / chemistry
  • Anticarcinogenic Agents / pharmacology*
  • Antiviral Agents / chemistry
  • Antiviral Agents / pharmacology*
  • Cell Cycle / drug effects
  • Cell Line, Tumor
  • DNA-Binding Proteins / antagonists & inhibitors*
  • DNA-Binding Proteins / metabolism
  • Female
  • High-Throughput Screening Assays / methods
  • Host-Pathogen Interactions / drug effects*
  • Human papillomavirus 16 / drug effects
  • Human papillomavirus 16 / physiology
  • Human papillomavirus 18 / drug effects
  • Human papillomavirus 18 / physiology
  • Humans
  • Oncogene Proteins, Viral / antagonists & inhibitors*
  • Oncogene Proteins, Viral / metabolism
  • Papillomaviridae
  • Papillomavirus Infections / metabolism
  • Papillomavirus Infections / virology
  • Proteolysis / drug effects
  • Repressor Proteins / antagonists & inhibitors*
  • Repressor Proteins / metabolism
  • Small Molecule Libraries / chemistry
  • Small Molecule Libraries / pharmacology*
  • Tumor Suppressor Protein p53 / metabolism
  • Ubiquitin-Protein Ligases / antagonists & inhibitors
  • Ubiquitin-Protein Ligases / metabolism
  • Uterine Cervical Neoplasms / virology

Substances

  • Anticarcinogenic Agents
  • Antiviral Agents
  • DNA-Binding Proteins
  • E6 protein, Human papillomavirus type 16
  • E6 protein, Human papillomavirus type 18
  • Oncogene Proteins, Viral
  • Repressor Proteins
  • Small Molecule Libraries
  • Tumor Suppressor Protein p53
  • UBE3A protein, human
  • Ubiquitin-Protein Ligases