人结直肠癌组织9p21-22区微卫星改变的研究

Microsatellite alterations on chromosome 9p21-22 in sporadic colorectal cancer.

目的 研究ｐ１６ 的改变是不是结直肠癌发展的重要的基因改变，探讨９ｐ２１２２ 区的分子遗传学改变与结直肠癌的关系。方法 采用ＰＣＲ、变性聚丙烯酰胺凝胶电泳、银染色等方法，检测９５例散发性结直肠癌患者癌组织９ｐ２１２２ 区４ 个位点的微卫星改变，包括微卫星不稳定性（ＭＳＩ） 及杂合性缺失（ＬＯＨ） ，研究其发生率，并将之与临床病理资料进行比较，并对ｐ１６ 内含子区表现有ＭＳＩ者进行了直接测序，研究内含子结构的改变状态。结果 在９ｐ２１２２ 区散发性结直肠癌的微卫星改变发生率为１７．９０％ （１７／９５） 。ＭＳＩ阳性组具有以下特征与ＭＳＩ阴性组不同：（１） 患者年龄较小，大多＜ ５０岁（Ｐ＜０ ．０５） ；（２）ＭＳＩ阳性组易发生粘液腺癌（ Ｐ＜０．０１） 。５ 例在ｐ１６（２） 位点ＭＳＩ阳性的病例直接测序都证明有Ａ数目的增加或减少。结论 选择合适的微卫星标记，就可对人类基因组任一染色体任一位点进行遗传不稳定性研究，可进而找到其他潜在的肿瘤相关基因，阐明肿瘤的发病机制。结果还提示，ｐ１６ 与结直肠癌关系不甚密切。

Objective To study whether alteration of p16 plays an important role in the development of colorectal carcinomas and the relationship between the molecular changes of 9p21 22 chromosome subregion in sporadic colorectal cancers. Methods To detect microsatellite instability (MSI) and loss of heterozygosity (LOH ) by PCR, denatured polyacrylamide gel electrophoresis and silver staining (microsatellite DNA PCR silver staining method) and to compare the results with the clinopathological parameters. Results Between MSI positive and negative cases and the clinopathological findings, some evidences found in the MSI positive group were as follows: (1)tendency towards younger patients (usually <50 years in age, P <0.05); (2) more frequently seen in mucoid carcinomas ( P <0.01). Conclusions Microsatellite DNA PCR silver staining method is very sensitive in detecting even a tiny change of a single base. MSI occured in the selected microsatellite loci of different subregions and different chromosomes might be different in significance, therefore, a right choice of the suitable loci for studying the microsatellite changes is important. Since the frequency of loss of heterozygosity at 9p21 22 is low (merely 8.42%), it is considered that p16 is not closely associated with the development of sporadic colorectal cancer.