Gould M N, Watanabe H, Kamiya K, Clifton K H
Int J Radiat Biol Relat Stud Phys Chem Med. 1987 Jun;51(6):1081-90. doi: 10.1080/09553008714551371.
Carcinogenesis is a multistage process consisting minimally of initiation and promotion/progression stages. Radiation and many environmental xenobiotics are potent initiating agents. We have shown that initiation of carcinogenesis in vivo by these agents is a common cellular event. In the irradiated thyroid (5 Gy) at least one in 20 cells is initiated. Initiation by both radiation and chemicals has also been shown to be a common cellular event in the mammary gland. Initiation therefore is most likely not the sole rate-limiting event in the carcinogenic process. The propensity of the initiated cell to express the malignant phenotype is modulated by many factors, including environmental chemicals and physiological and genetic factors. Scopal and abscopal physiological factors can either enhance or suppress the progression of initiated cells to a frank tumour. For example, prolactin enhances the rate of progression of radiation and chemically initiated mammary tumours while glucocorticoids suppress this progression. TSH enhances the progression of radiation-initiated thyroid tumours while a scopal factor associated with unirradiated thyroid cells suppresses progression of this tumour type.
致癌作用是一个多阶段过程，至少由启动阶段和促进/进展阶段组成。辐射和许多环境异生物质是强效的启动剂。我们已经表明，这些物质在体内引发致癌作用是一种常见的细胞事件。在接受5 Gy辐射的甲状腺中，每20个细胞中至少有一个被启动。辐射和化学物质引发致癌作用在乳腺中也已被证明是一种常见的细胞事件。因此，启动很可能不是致癌过程中唯一的限速事件。启动细胞表达恶性表型的倾向受到许多因素的调节，包括环境化学物质、生理和遗传因素。局部和远隔生理因素可以增强或抑制启动细胞发展为明显肿瘤的进程。例如，催乳素可提高辐射和化学引发的乳腺肿瘤的进展速度，而糖皮质激素则抑制这一进程。促甲状腺激素可促进辐射引发的甲状腺肿瘤的进展，而与未受辐射的甲状腺细胞相关的远隔因素则抑制这种肿瘤类型的进展。
