Oncogenes and Tumor Suppressor Genes

TABLE 5.22 Important Oncogenes and Tumor Suppressor Genes in Human Cancers... 

TABLE 85-1. Examples of Oncogenes and Tumor-Suppressor Genes... 

Hie terms oncogene and tumor suppressor gene do not give any information about the actual function of the gene or the protein for which they code. Both are coupled in a complex way to different positions in the network of proliferation regulation and in cell-cell interactions, as shown in the examples below. 

The function of oncogenes and tumor suppressor genes is generally investigated in defined cell lines. These serve as model systems in which individual aspects of tumor formation can be investigated. 

Immortalization, reduced requirement for growth factors and changed growth behavior are different characteristics of cells imdergoing transformation from a normal state to a tumor cell. All three characteristics are important parameters which are used to characterize the function of oncogenes and tumor suppressor genes. 

Cancer is generally the result of an accumulation of mutations in oncogenes and tumor suppressor genes. 

As mentioned earlier, epidemiological studies have revealed that the incidence of cancer increases exponentially with age. From these studies, it has been suggested that three to seven mutations or hits are necessary for cancer development. Definitive proof that these hits occur in oncogenes and tumor suppressor genes and that these genes cooperate in tumorigenesis comes from molecular studies in human cancer and mouse cancer models. 

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