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Cellular proteins involved in papillomavirus-induced transformation
D C Swan1, S D Vernon, J P Icenogle
1National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Archives of Virology
|January 1, 1994
Summary
High-risk human papillomaviruses (HPVs) contribute to cervical cancer by inactivating tumor suppressors like p53 and Rb. Viral DNA integration and oncogene activation are key steps in cervical carcinoma development.
Area of Science:
- Oncology
- Virology
- Molecular Biology
Background:
- Human papillomaviruses (HPVs) are linked to over 80% of cervical carcinomas.
- HPVs are categorized as high-risk or low-risk based on their association with cervical cancers.
- High-risk HPV early gene products (E6 and E7) immortalize keratinocytes and are implicated in cervical carcinoma development.
Purpose of the Study:
- To elucidate the role of high-risk HPVs in cervical carcinogenesis.
- To understand the mechanisms by which HPV E6 and E7 proteins interact with tumor suppressors p53 and Rb.
- To investigate the significance of viral DNA integration and chromosomal changes in tumor progression.
Main Methods:
- Analysis of HPV E6 and E7 protein interactions with p53 and Rb tumor suppressors.
- Examination of keratinocyte immortalization and transformation in tissue culture.
- Investigation of high-risk HPV DNA integration into host cell genomes.
- Comparison of p53 and Rb gene mutation frequencies in HPV-positive and HPV-negative tumors.
Main Results:
- High-risk HPV E6 and E7 proteins strongly interact with p53 and Rb, unlike low-risk HPV proteins.
- High-risk HPVs immortalize keratinocytes, but transformation requires additional chromosomal changes and possibly oncogene activation.
- High-risk HPV DNA is frequently integrated into cancer cell genomes, disrupting viral gene regulation and increasing E6/E7 expression.
- p53 and Rb genes appear less frequently mutated in HPV-positive tumors, suggesting inactivation via viral protein interaction is a primary mechanism.
Conclusions:
- High-risk HPV infection is a critical factor in cervical cancer, primarily through E6/E7 mediated inactivation of p53 and Rb.
- Cervical transformation is a multi-step process involving HPV infection, viral DNA integration, chromosomal alterations, and potentially oncogene activation.
- Inactivation of functional p53 or Rb, either by viral proteins or mutation, is essential for tumor progression, especially when oncogenes are activated.