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An oncogene is a gene that has the potential to cause cancer.[1] In tumor cells, they are often mutated or expressed at high levels.[2]
Most normal cells undergo a programmed form of rapid cell death (apoptosis). Activated oncogenes can cause those cells designated for apoptosis to survive and proliferate instead.[3] Most oncogenes require an additional step, such as mutations in another gene, or environmental factors, such as viral infection, to cause cancer. Since the 1970s, dozens of oncogenes have been identified in human cancer. Many cancer drugs target the proteins encoded by oncogenes.[2][4][5][6]
The term "oncogene" was coined in 1969 by [7]
The first confirmed oncogene was discovered in 1970 and was termed src (pronounced sarc as in sarcoma). Src was in fact first discovered as an oncogene in a chicken retrovirus. Experiments performed by Dr. G. Steve Martin of the University of California, Berkeley demonstrated that the Src was indeed the oncogene of the virus.[8] The first nucleotide sequence of v-src was sequenced in 1980 by A.P. Czernilofsky et al.[9]
In 1976 Drs. Dominique Stehelin, Nobel Prize in Physiology or Medicine in 1989.[10]
A proto-oncogene is a normal gene that can become an oncogene due to mutations or increased expression. The resultant protein may be termed as oncoprotein.[11] Proto-oncogenes code for proteins that help to regulate cell growth and differentiation. Proto-oncogenes are often involved in signal transduction and execution of mitogenic signals, usually through their protein products. Upon activation, a proto-oncogene (or its product) becomes a tumor-inducing agent, an oncogene.[12] Examples of proto-oncogenes include RAS, WNT, MYC, ERK, and TRK. The MYC gene is implicated in Burkitt's Lymphoma, which starts when a chromosomal translocation moves an enhancer sequence within the vicinity of the MYC gene. The MYC gene codes for widely used transcription factors. When the enhancer sequence is wrongly placed, these transcription factors are produced at much higher rates. Another example of an oncogene is the Bcr-Abl gene found on the Philadelphia Chromosome, a piece of genetic material seen in Chronic Myelogenous Leukemia caused by the translocation of pieces from chromosomes 9 and 22. Bcr-Abl codes for a receptor tyrosine kinase, which is constitutively active, leading to uncontrolled cell proliferation. (More information about the Philadelphia Chromosome below)
The proto-oncogene can become an oncogene by a relatively small modification of its original function. There are three basic methods of activation:
The expression of oncogenes can be regulated by microRNAs (miRNAs), small RNAs 21-25 nucleotides in length that control gene expression by downregulating them.[14] Mutations in such microRNAs (known as oncomirs) can lead to activation of oncogenes.[15] Antisense messenger RNAs could theoretically be used to block the effects of oncogenes.
There are several systems for classifying oncogenes,[16][17] but there is not yet a widely accepted standard. They are sometimes grouped both spatially (moving from outside the cell inwards) and chronologically (parallelling the "normal" process of signal transduction). There are several categories that are commonly used:
More detailed information for the above Table:
: NEO
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, ,
drug (//)
Lung cancer, Breast cancer, Colorectal cancer, Medical imaging, Prostate cancer
Metabolism, X-ray crystallography, Protein folding, Biochemistry, Glycolysis
Signal transduction, Calcium signaling, Gene, Cytoskeleton, Prostate cancer
Dna, Eukaryote, Rna, Chromosome, Gene expression
Chemotherapy, Leiomyosarcoma, International Classification of Diseases for Oncology, Cancer, Epithelium
DNA repair, Cancer, Oncogene, Gene, Genetics
Epigenetics, DNA repair, Polymerase chain reaction, Colorectal cancer, Cancer
Breast cancer, Gene, Epidermal growth factor receptor, Elisa, Protein
Protein, Gene, Receptor tyrosine kinase, Wnt signaling pathway, Cluster of differentiation