Oncogene

Oncogenes ( cancer genes literally ) are parts of the genetic material of a cell that promote the transition from normal growth behavior of the cell to unabated tumor growth. The "gen" in oncogene is here not as carcinogenic or mutagenic in the words, in the sense of " generating " or " promoting " is used, but is directly derived from the word gene as part of the genetic material from.

Proto-oncogenes

Oncogenes arise from changes in gene sequences (mutations ) that play a role in normal cell growth, cell division and cell differentiation. The so-called proto-oncogenes are precursors of oncogenes and are transformed by harmful influences (ionizing radiation, chemicals or viruses) in the carcinogenic form. There are now more than 100 ( as of 2004) Proto-oncogenes known. All cell cycle control genes are potential proto-oncogenes, as their change or dysfunction can mean the loss of control of cell division.

Proto-oncogenes are divided into several groups based on the proteins encoded by them:

• Growth factors
• Growth factor receptors
• G- proteins, e.g., encoded by the ras proto-oncogenes
• Non-receptor protein kinases, such as tyrosine kinases, Serin-/Threoninkinasen
• Nuclear transcription factors
• Tumor-specific chromosomal aberrations
• Oncogenes from viruses such as tax, the oncogene of HTLV -1, HTLV- 2, and bovine leukosis virus ( BLV ).

Proto-oncogenes are normal genes that are present in every cell and encode proteins that control growth, division and differentiation of a cell and control. Many of the components that affect the growth of a cell can be considered as proto-oncogenes. Mutated such a gene, it comes in the most common case, loss of function, cell division is no longer supported and the cell can no longer divide. Most pulls the programmed cell death, called apoptosis, by itself, which is no problem for the organism, since there are normally plenty of other separable cells in the neighborhood. But there is also the possibility that cell division is supported by the mutation of the protooncogene. It may happen that one gets by chromosome rearrangements Wachstumsgen under the influence of a promoter which normally has a strong activating effect. For example, the promoters of the immunoglobulins capable of proto-oncogenes are to activate oncogenes and thereby contribute to the development of tumors.