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Tumor suppressor genes: new pathways in gynecological cancer
1Department of Gynaecological Oncology, Samaritan Hospital for Women, Marylebone Road, London NW1 5YE and Ludwig Institute for Cancer Research, St Mary's Hospital Medical School, Norfolk Place, London W2 1PG.
Abstract:
The Retinoblastoma (Rb-1) and p53 genes appear to play an important role in controlling cell division, and mutations in Rb-1 and p53 have been reported widely in non-gynecological cancers. Unlike other cancer-related genes, which become activated during carcinogenesis, it is the loss of wild type p53 and Retinoblastoma protein (RB) function that is thought to contribute to cancer development. These genes therefore, have been called tumor suppressor genes since normal function appears to be necessary for negative control of cell growth. Several viral oncoproteins have been shown to interact with RB and p53. It seems likely that the formation of these complexes inactivates the cellular protein resulting in an overall effect similar to somatic mutation of the Rb-1 or p53 genes. The HPV16 transforming proteins E7 and E6 complex with protein products of Rb-1 and p53, respectively. In HPV positive anal and cervical tumors the normal function of RB and p53 may be inhibited by these viral proteins and so mutation within the RB-1 and p53 gene coding sequences would not appear to be a necessary step in the genesis of these tumors. However, in HPV negative tumors from the same tissues, loss of wild type Rb-1 and p53 activity may only be achieved by somatic mutation of these genes.
Insights
Tumor suppressor genes like Retinoblastoma (Rb-1) and p53 are crucial for cell division control. Viral proteins, such as HPV16 E7 and E6, can inactivate these tumor suppressors, impacting cancer development.
Area of Science:
- Oncology
- Molecular Biology
- Virology
Background:
- Retinoblastoma (Rb-1) and p53 are key tumor suppressor genes regulating cell division.
- Loss of function in Rb-1 and p53 contributes to various cancers.
- Viral oncoproteins can interact with and inactivate Rb-1 and p53 proteins.
Purpose of the Study:
- To investigate the role of viral oncoproteins in the inactivation of Rb-1 and p53.
- To understand the mechanisms by which HPV16 E7 and E6 proteins affect tumor suppressor function.
- To differentiate the roles of viral inactivation versus somatic mutation in HPV-positive and HPV-negative tumors.
Main Methods:
- Analysis of viral oncoprotein interactions with Rb-1 and p53.
- Examination of HPV16 E7 and E6 protein complex formation with Rb-1 and p53 products.
- Comparison of genetic alterations in HPV-positive and HPV-negative anal and cervical tumors.
Main Results:
- HPV16 E7 protein complexes with Rb-1 protein.
- HPV16 E6 protein complexes with p53 protein.
- In HPV-positive tumors, viral proteins inhibit Rb-1 and p53, potentially obviating the need for somatic mutations.
Conclusions:
- Viral oncoproteins play a significant role in inactivating tumor suppressor genes Rb-1 and p53 in HPV-associated cancers.
- Somatic mutations in Rb-1 and p53 may be essential for tumor development only in HPV-negative cases.
- Understanding these mechanisms is crucial for cancer research and therapeutic strategies.