Carcinogenesis (meaning literally, the creation of cancer) is the process by which normal cells are transformed into cancer cells.
Nonlethal genetic damage lies at the heart of carcinogenesis. Such genetic damage (or mutation) may be acquired by the action of environmental agents, such as chemicals, radiation, or viruses, or it may be inherited in the germ line.
The term "environmental," used in this context, involves any acquired defect caused by exogenous agents or endogenous products of cell metabolism. Not all mutations, however, are "environmentally" induced. Some may be spontaneous and stochastic.
Carcinogenesis is a multistep process at both the phenotypic and the genetic levels. A malignant neoplasm has several phenotypic attributes, such as excessive growth, local invasiveness, and the ability to form distant metastases. These characteristics are acquired in a stepwise fashion, a phenomenon called tumor progression.
At the molecular level, progression results from accumulation of genetic lesions that in some instances are favored by defects in DNA repair.
Types
chemical carcinogenesis
physical carcinogenesis
- radic carcinogenesis
viral carcinogenesis
Localization
colorectal carcinogenesis
See also