Genetic heterogeneity of the c-K-ras locus in colorectal adenomas but not in adenocarcinomas.
Genetic heterogeneity of the c-K-ras locus in colorectal adenomas but not in adenocarcinomas.
复制标题
结直肠腺瘤中 c-K-ras 基因座的遗传异质性，但腺癌中没有。
DOI：
10.1093/jnci/85.13.1058
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Perucho,M
中科院分区：
文献类型：
--
作者：
Shibata,D;Schaeffer,J;Li,ZH;Capella,G;Perucho,M
背景以往对结直肠癌的分子遗传学研究发现，c-K-ras基因(也称为KRAS2)在其发展的各个阶段都存在多个突变。由于技术上的困难，以前的研究很少关注c-K-ras突变在同一原发肿瘤标本的多个区域的详细分布。目的描述c-K-ras突变在同一原发癌标本多个区域中的分布情况，以描述早期和晚期结直肠癌发生的差异。选择7例腺癌和7例腺瘤进行c-K-ras基因突变和正常组织与肿瘤组织之间的组织学转变。通过将薄的、固定的组织切片放置在没有盖片的塑料玻片上，通过选择性紫外线辐射分级法准备组织切片以供分析。在显微镜下，毛毡笔尖上的小墨点被手动直接放置在相对纯净的细胞亚群上。将载玻片放置在组织一侧暴露在紫外线透光器下2-4小时，以灭活存在于未受保护(未点状)细胞中的DNA。将塑料玻片上的单个圆点切成2×2 mm的正方形，放入微隔离管中。提取DNA，上清液进行聚合酶链式反应(PCR)分析。结果选择性紫外光分割法和聚合酶链式反应分析显示，c-K-ras基因突变从未延伸到正常粘膜，在所有肿瘤细胞中均存在，而在所有7例腺癌和7例腺瘤中，无论表型如何，c-K-ras突变均存在。对两种癌症的p53(也称为TP53)突变或杂合性丢失的进一步检查表明，这些额外的突变也存在于所有肿瘤细胞中，这表明一个转化的克隆负责大部分的生长。然而，在其他4个腺瘤中，由于c-K-ras突变仅在不连续的部分被检测到，所以显示了肿瘤的异质性。结论腺瘤的形成可能包括一个阶段，在这个阶段中存在多个不同的肿瘤克隆，而大多数癌症似乎具有同质性的成分，这可能是这些克隆中的一个成功进展的结果。[癌症杂志85：1058-1063,1993]
BackgroundPrevious molecular genetics studies of colorectal cancer have identified multiple mutations in the c-K-ras gene (also known as KRAS2) in all phases of its development. Because of technical difficulty, prior studies rarely focused attention on the detailed distribution of c-K-ras mutations in multiple regions of the same primary tumor specimen. However, with recent development of the selective UV radiation fractionation method, characterization of c-K-ras mutations in multiple regions of the same primary tumor specimen can be performed.PurposeOur purpose was to describe how c-K-ras mutations were distributed among cells obtained from multiple regions of the same primary tumor in an attempt to describe differences between early and late colorectal carcinogenesis.MethodsFormalin-fixed, paraffin-embedded tissue blocks were obtained. Seven adenocarcinomas and seven adenomas were selected for the presence of mutant c-K-ras genes and histologic transitions between normal and neoplastic tissue. Tissue sections were prepared for analysis by the selective UV radiation fractionation method by placing thin, fixed tissue sections on a plastic slide with no coverslip. Under the microscope, small ink dots from a felt-tip pen were manually placed directly on relatively pure cell subpopulations. The slides were placed with the tissue side exposed to a UV transilluminator for 2–4 hours to inactivate the DNA present in the unprotected (“undotted”) cells. Individual dots were cut out of the plastic slide into 2 × 2-mm squares and placed into microfuge tubes. The DNA was extracted and supernatant used for polymerase chain reaction (PCR) analysis. Mutations at c-K-ras codons 12 and 13 were detected.ResultsThe selective UV radiation fractionation method and PCR analysis revealed that c-K-ras mutations never extended into normal mucosa and were present in all neoplastic cells regardless of phenotypes in all seven adenocarcinomas and three of the seven adenomas. Further examination of two carcinomas for p53 (also known as TP53) mutations or loss of heterozygosity demonstrated that these additional mutations were also present in all tumor cells, suggesting that a single transformed clone was responsible for the majority of growth. However, in four other adenomas, tumor heterogeneity was demonstrated, since c-K-ras mutations were detected only in discrete portions.ConclusionsAdenoma formation may include a stage in which multiple and genetically distinct neoplastic clones are present, while most carcinomas appear to have a homogeneous composition that may result from the successful progression of one of these clones. [J Natl Cancer Inst 85:1058–1063, 1993]