Oncogene

An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels. Most normal cells will undergo a programmed form of rapid cell death (apoptosis) when critical functions are altered and malfunctioning. Activated oncogenes can cause those cells designated for apoptosis to survive and proliferate instead. Most oncogenes began as proto-oncogenes: normal genes involved in cell growth and proliferation or inhibition of apoptosis. If, through mutation, normal genes promoting cellular growth are up-regulated (gain-of-function mutation), they will predispose the cell to cancer; thus, they are termed "oncogenes". Usually multiple oncogenes, along with mutated apoptotic or tumor suppressor genes will all act in concert to cause cancer. Since the 1970s, dozens of oncogenes have been identified in human cancer. Many cancer drugs target the proteins encoded by oncogenes. The theory of oncogenes was foreshadowed by the German biologist Theodor Boveri in his 1914 book Zur Frage der Entstehung Maligner Tumoren (Concerning the Origin of Malignant Tumors) in which he predicted the existence of oncogenes (Teilungsfoerdernde Chromosomen) that become amplified (im permanenten Übergewicht) during tumor development. Later on, the term "oncogene" was rediscovered in 1969 by National Cancer Institute scientists George Todaro and Robert Huebner. The first confirmed oncogene was discovered in 1970 and was termed SRC (pronounced "sarc" as it is short for sarcoma). SRC was first discovered as an oncogene in a chicken retrovirus. Experiments performed by Dr. G. Steve Martin of the University of California, Berkeley demonstrated that SRC was indeed the gene of the virus that acted as an oncogene upon infection. The first nucleotide sequence of v-Src was sequenced in 1980 by A.P. Czernilofsky et al. In 1976, Drs. Dominique Stéhelin, J. Michael Bishop and Harold E. Varmus of the University of California, San Francisco demonstrated that oncogenes were activated proto-oncogenes as is found in many organisms, including humans.