Mechanisms of Radiation Transformation
The carcinogenic properties of ionizing radiation were evident within a few years of the discovery of X-rays by Roentgen, when skin cancer began developing in radiation ulcers amongst a number of early radiation workers. This phenomenon has since been confirmed in a number of cellular and animal models, in which it has been shown that radiation will induce cancer in most tissues of most mammalian species. Despite these observations, however, the molecular mechanisms for this effect remain obscure. In order to better elucidate the molecular and cellular events associated with the conversion of a normal cell to a malignant one, recent attention has focused on the induction of malignant transformation of mammalian cells in vitro (1, 2). Such studies have shown that the induction of transformation in vitro is a complex, multi-stage process (1, 3). They have also allowed the correlation of transformation with the induction and repair of specific molecular DNA damage (4), as well as with other cellular effects such as cytogenetic changes (4, 5), and single gene mutations (6, 7). In particular, they have facilitated the design of experiments to test the somatic mutation theory of carcinogenesis; that is, the hypothesis that the initial radiation induced lesion which initiates the process of carcinogenesis is a mutation in a structural gene. It should be remembered, however, that the conversion of a normal cell to one with malignant potential represents but a very early stage in the overall process of the induction of an invasive metastatic tumor in vivo.
KeywordsMalignant Transformation Sister Chromatid Exchange Irradiate Cell Mouse Embryo Fibroblast Syrian Hamster Embryo
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- 1.J. B. Little, Radiation carcinogenesis in vitro: implications for mechanisms, in: “Origins of Human Cancer, Vol. 4, Book A,” H. H. Hiatt, J. D. Watson and J. A. Winston, eds., Cold Spring Harbor Lab., Cold Spring Harbor, New York (1977), pp. 923–939.Google Scholar
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