Potential drugs against cervical cancer: zinc-ejecting inhibitors of the human papillomavirus type 16 E6 oncoprotein.
BACKGROUND
The principal agent in the etiology of cervical cancer, i.e., human papillomavirus (HPV) type 16, encodes three oncoproteins, E5, E6, and E7. Structural and mutational studies have identified two potential zinc-finger domains as critical for E6 protein function. We investigated several assays to identify and characterize compounds that interfere with the binding of zinc to E6.


METHODS
Thirty-six compounds were selected on the basis of their structure, which would facilitate their participation in sulfhydryl residue-specific redox reactions, and were tested for their ability to release zinc from E6 protein. The zinc-ejecting compounds were then tested for their ability to inhibit E6 binding to E6-associated protein (E6AP) and E6-binding protein (E6BP), two coactivators of E6-mediated cellular transformation. The binding of E6 to E6BP and E6AP was measured by use of surface plasmon resonance (a technique that monitors molecular interactions by measuring changes in refractive index) and by use of in vitro translation assays. The compounds were also tested for their effects on the viability of HPV-containing cell lines.


RESULTS
Nine of the 36 tested compounds ejected zinc from E6. Two of the nine compounds inhibited the interaction of E6 with E6AP and E6BP, and one of these two, 4, 4'-dithiodimorpholine, selectively inhibited cell viability and induced higher levels of p53 protein (associated with the induction of apoptosis [programmed cell death]) in tumorigenic HPV-containing cells.


CONCLUSIONS
We have described assay systems to identify compounds, such as 4,4'-dithiodimorpholine, that can potentially interfere with the biology and pathology of HPV. These assay systems may be useful in the development of drugs against cervical cancer, genital warts, and asymptomatic infections by genital HPVs.
Beerheide
W
W
Screening for Novel Inhibitors Laboratory, Institute of Molecular and Cell Biology, Singapore, Republic of Singapore.
Bernard
H U
HU
Tan
Y J
YJ
Ganesan
A
A
Rice
W G
WG
Ting
A E
AE
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000096:biosynthesis; D006801:Humans; D008025:Ligases / Q000187:drug effects; D008969:Molecular Sequence Data; D009025:Morpholines / Q000494:pharmacology*; D009856:Oncogene Proteins, Viral / Q000187:drug effects* / Q000378:metabolism; D027383:Papillomaviridae; D030361:Papillomavirus Infections / Q000150:complications; D011485:Protein Binding / Q000187:drug effects; D014176:Protein Biosynthesis; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014412:Tumor Virus Infections / Q000150:complications; D044767:Ubiquitin-Protein Ligases; D002583:Uterine Cervical Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000821:virology*; D015032:Zinc / Q000378:metabolism*; D016335:Zinc Fingers / Q000187:drug effects*
D000970:Antineoplastic Agents; D002135:Calcium-Binding Proteins; C068651:E6 protein, Human papillomavirus type 16; D009025:Morpholines; D009856:Oncogene Proteins, Viral; C088393:RCN2 protein, human; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; C471639:UBE3A protein, human; D044767:Ubiquitin-Protein Ligases; D005982:Glutathione Transferase; D008025:Ligases; D005978:Glutathione; D015032:Zinc; C013975:4,4'-dithiodimorpholine