Mechanism of Carcinogenesis
In the preceding sub-section you learnt that carcinogenesis is a multistep process. Even though cancer may be caused by many agents chemical, physical and viral they all have a common pathway that are, damage to DNA. This damage or alteration of the normal DNA of the cell can be affected mainly in two ways. Either the common genes are mutated or as in the case of viral agents, abnormal genes are inserted in the host cell which encodes abnormal proteins the question may arise that of the genes of the normal cell on mutation give rise to neoplastic cells? We said earlier that neoplastic cells arise while normal cells somehow escape the clutches of cell growth regulatory mechanisms. Hence, genes that are responsible for regulating cell growth and differentiation would be the observable targets of mutation. Research over the years has revealed that two major types of genes play a role in cancer induction. The first is a set of genes that regulate cell growth and differentiation. These genes are termed as proto-oncogenes and their mutated versions that can cause cancer are called oncogenes. The second is a set of tumor-suppressor genes as well called anti-oncogenes whose common function is to prevent overgrowth of cells.