Gene Amplification During Stages of Carcinogenesis
Models of carcinogenesis have developed from extensive observation of clinical and experimental systems. (This summary is based on Pitot, 1981.) The related concepts of promotion and progression describe an essential feature of carcinogenesis, the gradual change from a normal cell to a tumor composed of proliferating, invading, metastasizing cells. Promotion is the gradual conversion of undetectable initiated cells to tumors without the continuing action of a carcinogen. Promotion requires distinct agents and involves both cell proliferation and gradually changing cell properties. In other words, promotion is the process by which an initiated cell evolves from a state of homeostatically regulated proliferation to a state of inadequately regulated proliferation. However, the appearance of a tumor is not really an endpoint in this process, and the more general term, progression, refers to the continuous evolution in characters both before and after a tumor has formed.
KeywordsGene Amplification Liver Regeneration Replication Fork Burkitt Lymphoma Dhfr Gene
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