Gilmer T M, Lamb P W, Oshimura M, Barrett J C
Cancer Res. 1987 Sep 1;47(17):4663-6.
A preneoplastic cell line (10W) isolated after treatment of Syrian hamster embryo cells with asbestos was cotransfected with pSV2-neo DNA and Rous sarcoma virus DNA. Six of these colonies contained v-src DNA; however, none of the six initially expressed v-src RNA. Five of the clones failed to grow in soft agar (frequency, less than 10(-6)). One clone (61) grew in soft agar, but with a low frequency. Three of the clones (41, 61, and 62) were tumorigenic in nude mice and three were nontumorigenic. Cells cloned from soft agar or established from tumor explants expressed the v-src gene. The gene copy number of v-src, which was three to 10 in the original neoR clones, was increased approximately 10-fold in the soft agar-derived cell clones and tumor-derived cell lines. Cytogenetic analyses indicated that cells with amplified v-src contained double minute chromosomes. The results suggest that gene amplification influences the expression of the transfected oncogene and is a mechanism which can overcome the initial suppression of transcription of the v-src oncogene in the 10W cell line.
用石棉处理叙利亚仓鼠胚胎细胞后分离得到的一种癌前细胞系（10W），与pSV2-neo DNA和劳氏肉瘤病毒DNA共转染。这些菌落中有六个含有v-src DNA；然而，这六个菌落最初均未表达v-src RNA。其中五个克隆在软琼脂中无法生长（频率小于10^(-6)）。一个克隆（61）能在软琼脂中生长，但频率较低。三个克隆（41、61和62）在裸鼠中具有致瘤性，另外三个则无致瘤性。从软琼脂中克隆的细胞或从肿瘤外植体建立的细胞系表达v-src基因。v-src的基因拷贝数在原始neoR克隆中为3至10个，在软琼脂衍生的细胞克隆和肿瘤衍生的细胞系中增加了约10倍。细胞遗传学分析表明，v-src扩增的细胞含有双微体染色体。结果表明，基因扩增影响转染癌基因的表达，是一种可以克服最初10W细胞系中v-src癌基因转录抑制的机制。
