Higinbotham K G, Rice J M, Perantoni A O
Laboratory of Comparative Carcinogenesis, National Cancer Institute, Frederick, Maryland.
Mol Carcinog. 1992;5(2):136-9. doi: 10.1002/mc.2940050209.
Renal mesenchymal tumors induced in F344 rats with methyl(methoxymethyl)nitrosamine (DMN-OMe) have previously been shown by our laboratory to contain transforming Ki-ras sequences, activated most commonly by a variety of codon 12 mutations. Further sequence analysis of the one DMN-OMe-induced tumor with transforming Ki-ras sequences detected by NIH 3T3 transfection assay but with no mutation in codon 12 detected by selective oligonucleotide hybridization has now revealed an activating point mutation in codon 63. The observed GAG----AAG transition in codon 63, which replaces glutamic acid with lysine, was the only detectable mutation in exon 1 and 2 hotspot regions of Ki-ras in this tumor. The same mutation was also detected in Ki-ras sequences derived from first- and second-cycle transformants in NIH 3T3 transfection assays. Although random mutagenesis studies of cloned Ha-ras sequences by Fasano et al. (Proc Natl Acad Sci USA 81:4008-4012, 1984) had already indicated that GAG----AAG mutations in codon 63 of ras are transforming, this is the first demonstration of the natural occurrence of this particular activating mutation in a tumor.
我们实验室先前已证明，用甲基（甲氧基甲基）亚硝胺（DMN-OMe）诱导F344大鼠产生的肾间充质肿瘤含有转化型Ki-ras序列，其激活最常见的方式是多种密码子12突变。对一种经NIH 3T3转染试验检测到含有转化型Ki-ras序列，但通过选择性寡核苷酸杂交未检测到密码子12突变的DMN-OMe诱导肿瘤进行进一步序列分析，现已揭示密码子63处存在一个激活点突变。在该肿瘤中，观察到的密码子63处的GAG----AAG转换，即用赖氨酸取代谷氨酸，是Ki-ras外显子1和2热点区域中唯一可检测到的突变。在NIH 3T3转染试验中，从第一代和第二代转化体衍生的Ki-ras序列中也检测到相同的突变。尽管Fasano等人（《美国国家科学院院刊》81:4008 - 4012, 1984）对克隆的Ha-ras序列进行的随机诱变研究已经表明，ras密码子63处的GAG----AAG突变具有转化作用，但这是首次证明这种特定激活突变在肿瘤中自然发生。
