Tumor suppressor gene
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Overview
A tumor suppressor gene is a gene that reduces the probability that a cell in a multicellular organism will turn into a tumor cell. A mutation or deletion of such a gene will increase the probability of the formation of a tumor.
Two-hit hypothesis
Unlike oncogenes, tumor suppressor genes generally follow the 'two-hit hypothesis,' which implies that both alleles that code for a particular gene must be affected before an effect is manifested. This is due to the fact that if only one allele for the gene is damaged, the second can still produce the correct protein. In other words, tumor suppressors are usually not haploinsufficient, although there are notable exceptions (the p53 gene product).
Functions
Tumor suppressor genes, or more precisely, the proteins for which they code, either have a dampening or repressive effect on the regulation of the cell cycle or promote apoptosis, and sometimes do both. The functions of tumor suppressor proteins fall into several categories including the following:[1]
- Repression of genes that are essential for the continuing of the cell cycle. If these genes are not expressed, the cell cycle will not continue, effectively inhibiting cell division.
- Coupling the cell cycle to DNA damage. As long as there is damaged DNA in the cell, it should not divide. If the damage can be repaired, the cell cycle can continue.
- If the damage can not be repaired, the cell should initiate apoptosis, or programmed cell death, to remove the threat it poses for the greater good of the organism.
- Some proteins involved in cell adhesion prevent tumor cells from dispersing, block loss of contact inhibition, and inhibit metastasis.[2]
Examples
The first tumor suppressor protein discovered was the pRb protein in human retinoblastoma; however, recent evidence has also implicated pRb as a tumor survival factor.
Another important tumor suppressor is the p53 tumor suppressor protein produced by the TP53 gene.
PTEN acts by opposing the action of PI3K, which is essential for anti-apoptotic, pro-tumorogenic Akt activation.
See also
- Adenomatosis polyposis coli
- Oncogene
- Cancer
- DNA repair
- Signal transduction
- Von Hippel Lindau Binding protein 1
References
- ↑ Sherr C (2004). "Principles of tumor suppression". Cell 116 (2): 235-46. PMID 14744434.
- ↑ Hirohashi S, Kanai Y (2003). "Cell adhesion system and human cancer morphogenesis". Cancer Sci 94 (7): 575-81. PMID 12841864.
External links
- Cancer Medicine, online textbook.
- Human Molecular Genetics, online textbook.
- Introduction to Genetic Analysis, online textbook.
- TCF21 gene discovery at Ohio State University
Tumor suppressor genes/proteins |
|---|
| APC - BRCA1 - BRCA2 - CHEK2 - Neurofibromin 1 - Maspin - Neurofibromin 2/Merlin - p14arf - p16 - p21 - p27 - p53 - p57 - p73 - pRb - PTEN - SDHB - SDHD - VHL |
de:Tumorsuppressorgennl:Tumorsuppressorgensk:Tumor-supresorový gén fi:Kasvunrajoitegeeni sv:Tumörsuppressorgen
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
