ABSTRACT
Cancers are caused by abnormalities of the genome [18]. These abnormalities can be due to the effects of carcinogens such as chemical and viruses (environment), inherited traits, and randomly acquired errors during DNA replication and/or repair. Thus, cancer cells are characterized by genomic rearrangements, activation or repression of oncogenes and tumor suppressor genes, karyotypic and phenotypic instability, uncontrolled growth, and metastatic ability with the acquisition of new phenotypes (loss of adhesion, gain of new resistances). Several types of genes may be affected in cancer [17]. The oncogenes are genes that when mutated or expressed at high levels help turn a normal cell into a cancer cell by allowing the gain of new properties
FIGURE 3.1 Genes involved in the tumorigenesis process. Each step of the process is characterized by the involvement of a set of genes: genes of the metabolism in response to carcinogen insults oncogenes and tumor suppressor genes in cell transformation, and metastatic genes in dissemination.
