Bianchi A B, Aldaz C M, Conti C J
Department of Carcinogenesis, University of Texas, M.D. Anderson Cancer Center, Smithville 78957.
Proc Natl Acad Sci U S A. 1990 Sep;87(17):6902-6. doi: 10.1073/pnas.87.17.6902.
We analyzed the normal/mutated allelic ratio of the Ha-ras-1 gene in mouse skin squamous cell carcinomas induced by initiation with dimethylbenz[a]anthracene and promotion with phorbol 12-myristate 13-acetate. DNA for these studies was obtained from short-term tumor cultures (24-72 hr) to eliminate the contribution of stromal and inflammatory cells to the sample. The allelotypic analysis was performed in 25 squamous cell carcinomas by quantitative radio-analysis of the Xba I restriction fragment length polymorphism as detected by BS9, a v-Ha-ras probe, and rehybridization of the Southern blots with probes for chromosomes 7 and 8. Approximately 85% of the tumors presented overrepresentation of the mutated allele in the form of 1 normal/2 mutated (12 tumors), 0 normal/3 mutated (4 tumors), 0 normal/2 mutated (3 tumors), and gene amplification (3 tumors). No tumor was found with a 2 normal/1 mutated allelic ratio. These results support our previous cytogenetic studies, indicating that trisomy of chromosome 7 is present in the majority of these tumors and show that nonrandom duplication of the chromosome carrying the mutated Ha-ras-1 allele appears to be a major mechanism by which the mutated gene is overrepresented.
我们分析了用二甲基苯并[a]蒽启动并用佛波醇12-肉豆蔻酸酯13-乙酸酯促进诱导的小鼠皮肤鳞状细胞癌中Ha-ras-1基因的正常/突变等位基因比例。这些研究的DNA取自短期肿瘤培养物（24 - 72小时），以消除基质和炎症细胞对样本的影响。通过对由v-Ha-ras探针BS9检测到的Xba I限制性片段长度多态性进行定量放射分析，并将Southern印迹与7号和8号染色体的探针重新杂交，对25例鳞状细胞癌进行了等位基因分型分析。大约85%的肿瘤呈现出突变等位基因的过度表达，形式为1个正常/2个突变（12个肿瘤）、0个正常/3个突变（4个肿瘤）、0个正常/2个突变（3个肿瘤）以及基因扩增（3个肿瘤）。未发现具有2个正常/1个突变等位基因比例的肿瘤。这些结果支持了我们之前的细胞遗传学研究，表明这些肿瘤中的大多数存在7号染色体三体，并表明携带突变的Ha-ras-1等位基因的染色体的非随机复制似乎是突变基因过度表达的主要机制。
