The Multistage Concept of Carcinogenesis

摘要: The recognition of carcinogenesis as a complex multievent process has developed from evidence gained over the past 50 years research in experimental oncology demonstrating that tumors can be induced high yield by combined administration agents may have little or no carcinogenic activity when given singly. Three major types tumorigenic enhancement defined on basis inducing used and temporal relationships their administration: 1. Syncarcinogenesis: Synergistic tumor formation simultaneous1 sequential treatment2 with two carcinogens separately relatively activity 2. Cocarcinogenesis: Enhancement simultaneous carcinogen an additional agent (cocarcinogen) intrinsic but facilitates action3–8 3. Two-stage, initiation-promotion carcinogenesis: (initiator) (promoter) expression prior carcinogen-induced cryptic cellular changes.3 In this context, initiating is exemplified subcarcinogenic dose carcinogen, i.e., one will not elicit neoplasms within life span animal produce irreversible fundamental change (i.e., mutation) cells target organ tissue so to predispose them neoplastic transformation they are further subjected appropriate promoting stimulus. A promoter, certain plant products, hormones, xenobiotics acts affect gene stimulate hyperplastic expansion initiated cell population. This ultimately results development persistent precancerous nodules, papillomas, polyps organ. Some these lesions then undergo progression malignant (see Chapter 10).