Oncogenic transformation of murine C3H 10T1/2 cells resulting from DNA double-strand breaks induced by a restriction endonuclease.
Oncogenic transformation of murine C3H 10T1/2 cells resulting from DNA double-strand breaks induced by a restriction endonuclease.
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由限制性核酸内切酶引起的DNA双链断裂引起的鼠C3H 10T1/2细胞的致癌转化。
DOI：
10.1038/bjc.1989.378
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发表时间：
1989-12
影响因子：
8.8
通讯作者：
Riches, A C
中科院分区：
文献类型：
--
作者：
Bryant, P E;Riches, A C
圣安德鲁斯大学生物学和临床前医学系，圣安德鲁斯，Fife KY16 STS，英国。几十年来，电离辐射一直被认为是一种有效的致癌物，但暴露细胞 DNA 中导致细胞发生致癌转化的主要病变的性质尚不清楚。人们普遍认为，致癌转化是一个多阶段过程（Barrett & Fletcher，1987），至少需要两个事件的相互作用：“启动”事件和“促进”事件。这些可能采取例如一种以上癌基因的激活或异常表达的形式，例如c-ras和c-myc（例如Balmain & Pragnell，1983；Balmain，1985），或突变癌基因的激活（Burck等，1988；Bradshaw，1986）。对于体内系统，影响初始治疗结果的因素的多样性表明了该过程的复杂性（例如Fry，1981；Upton，1984）。尽管转化过程的本质尚未被理解，但经常观察到在转化细胞中发生了核型变化，特别是易位（例如慢性粒细胞白血病中的费城染色体），这可能与转化过程有因果关系（Klein & Klein，1984）。培养细胞的致癌转化可以在鼠 C3H 10T1/2 系统中进行研究（Reznikoff 等，1973；Han & Elkind，1979；Ken-nedy 等，1980）。 10T1/2 系统可能不是作为研究整个动物癌症诱导模型的理想系统。然而，它是可用于检测动物或人类已知致癌物质的少数测试系统之一。 10T1/2 细胞从“正常”细胞表型向不受控制的细胞生长灶的转化允许量化辐射或其他基因毒性剂的影响。这些快速生长的病灶（III型病灶）可以在皮下接种足够数量的细胞后在同系小鼠中产生恶性肿瘤。尽管已经可以获得诱导转化病灶作为辐射剂量的函数的剂量效应关系，但通过辐射诱导这些病灶的机制尚不清楚。特别是，还不可能确定原发性损伤或导致转化细胞遗传改变的损伤。主要问题之一是电离辐射会在暴露细胞的 DNA 中诱发几种不同类型的初始损伤。这些是直接的 DNA 链断裂（单链或双链）、碱基损伤以及 DNA 链之间或 DNA 与蛋白质之间的交联。对于真核细胞中的几个辐射损伤终点（例如细胞死亡、染色体畸变和突变），DNA 双链断裂（dsb）被认为是致病病变（Frankenberg 等，1984；Natarajan 等，1980）。此外，已经表明，将透化的哺乳动物细胞暴露于 II 型限制性内切核酸酶 (RE) 中，会在特定识别序列处诱导 DNA 双链断裂，从而导致染色体畸变的诱导（综述参见 Bryant, 1988）。之前已经表明
Department ofBiology and Preclinical Medicine, University of St Andrews, St Andrews, Fife KY16 STS, UK. lonising radiationhas been acknowledged as an effective carcinogen for several decades but the nature of the primary lesions in the DNAof exposed cells which cause them to undergo oncogenic transformation is not known. It is generally agreed that oncogenic transformation is a multi-stage process (Barrett & Fletcher, 1987) at the very least requiring theinteraction oftwo events: an'initiation'and a'promotion'event. These may take the form of, for example, the activation or abnormal expression of more than one oncogene, such as c-ras and c-myc (eg Balmain & Pragnell, 1983; Balmain, 1985), or the activationof a mutated oncogene (Burck et al., 1988; Bradshaw, 1986). For in vivo systems the complex nature of the process is indicated by the multiplicity of factors influencing the outcome of initial treatments (eg Fry, 1981; Upton, 1984). Although the essen-tial nature of the transformation process is not yet under-stood it is a frequent observation that karyotypic changes, particularly translocations, have taken place in transformed cells (eg the Philadelphia chromosomein chronic myeloid leukaemia) which may be causally related to the transforma-tion process (Klein & Klein, 1984). Oncogenic transformation of cultured cells can be studied in the murine C3H 10T1/2 system (Reznikoff et al., 1973; Han & Elkind, 1979; Ken-nedy et al., 1980). The 10T1/2 system may notbe an ideal system as a model for the study of cancer induction in the whole animal. However, it is one of the few test systems available for agents or factors which are known carcinogens in animals or humans. Transformation of 10T1/2 cells from the'normal'cell phenotype to foci of uncontrolled cell growth allows the quantification of the effects of radiation or other genotoxic agents. These foci of rapid growth (type III foci) can be shown to yield malignant tumours in syngeneic mice after subcutaneous inoculation of a sufficient number of cells.Although it has been possible to obtain dose-effect rela-tionships for induction of transformed foci as a function of radiation dose, the mechanisms of inductionof these by radiation are not yet understood. In particular ithas not been possible to identify the primary lesion or lesions respon-sible for the genetic alterations of transformedcells. One of the main problems is that ionising radiation induces several different types ofinitial lesions in the DNA of exposed cells. These are direct DNA strand breaks (single or double), base lesions, and cross-links between strands of DNA or between DNA and protein. For several radiation-damage end-points, in eukaryotic cells (eg cell death, chromosome aberrations and mutations) the DNA doublestrand break (dsb) has been implicated as the causative lesion (Frankenberg et al., 1984; Natarajan et al., 1980). Moreover, it has been shown that exposure of permeabilised mammalian cells to type II restriction endonucleases (RE) which induce double-strand breaks in DNA at specific recognition sequences leads to the induction of chromosomal aberrations (for a review see Bryant, 1988). It was shown previously that