ジメチルヒドラジン誘発マウス大腸異常腺窩巣におけるKi-ras遺伝子点突然変異の解析(Mini Symposium IX. 癌における遺伝子変化)

概要

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The Ki-ras point mutation in DMH-induced aberrant crypt foci (ACF) of mouse colon was investigated to clarify the nature of ACF which has been considered as a precursor of colon cancer. Male CDF1 mice were treated three times s.c. with 20 mg/kg b.w. of DMH. Four weeks after first DMH treatment, these mice were sacrificed. Control group was treated with saline s.c. in the same way. After morphological identification of ACF, tiny mucosal tissues containing ACF which consisted of more than 3 aberrant crypts (AC) were taken by using Pasteur's pipettes under a microscope. Ki-ras gene was amplified from these tissues by PCR and the point mutation of this gene was analyzed by oligonucleotide hybridization. The total number of ACF per colon was 28.5±9.6, the total number of AC per colon was 48.0±7.3, and the mean size of ACF was 1.67±0.10. No ACF was found in colons of control group. Ki-ras mutations were detected in two, one in codon 12 : GGT→G__-AT and another in codon 13 : GGC→G__-AC, out of 39 ACF. The sensitivity of oligonucleotide hybridization is about 5% and the cells which compose ACF is 1/10-1/20 of thissues from which DNA was extracted. Taking tese into consideration, detection of Ki-ras mutation in ACF indicates that these two ACF are formed by clonal expansion originated from one cell which mutated at Ki-ras gene. This also suggests that ACF is one of the precursors of mouse colon cancer.
1993-09-10