散发性结直肠癌1号染色体等位基因杂合缺失精细定位研究

Refined mapping of loss of heterzygosity on chromosome 1 in sporadic colorectal carcinoma

目的抑癌基因的杂合缺失(LOH)被认为是结直肠癌形成的通路之一。本实验通过对1号染色体1p36.33～36.31、1q31.1～32.1区域进行杂合缺失精细定位分析,以发现更精确的高频杂合缺失区域。方法在1p36.33～36.31、1q31.1～32.1区域分别选择7个、6个荧光标记微卫星引物与83例结直肠癌的肿瘤和正常组织进行聚合酶链反应(PCR)反应。产物在电泳后进行LOH分析。LOH结果与临床病理参数之间的关系比较采用x^2检验。结果1p36.33～36.31区域平均杂合缺失率是31.47%,以D1S243位点最高,为47.22%(34/72),最低是D1S1347,为7.35% (5/68)。存在两个高频杂合缺失区域:D1S243位点(1p36.33)以及D1S468-D1S2660区域(1p36.32～36.31)。1q31.1～32.1区域平均杂合缺失率是22.98%,以D1S2622位点最高,为36.73%(18/49),最低是D1S412,为16.42%(11/67)。更精确的缺失范围定位在D1S413和D1S2622之间(1q31.3～32.1),大约2cm的遗传距离范围内。1p36.33～36.31、1q31.1～32.1区域各位点的杂合缺失率与性别、年龄、肿瘤大小、生长方式以及Dukes分期无显著相关。提示该区域上的杂合缺失现象普遍存在于各种类型的散发性结直肠癌中。结论1号染色体上存在3个高频杂合缺失区域,D1S243位点(1cm)、D1S468和D1S2660位点之间(3cm)以及D1S413和D1S2622之间(2cm),提示在这些区域存在与结直肠癌相关的抑癌基因。

Objective Loss of heterozygosity of tumor suppressor genes is believed to play a key role in carcinogenesis of colorectal carcinoma. In this study, we performed refined mapping of loss of heterozygosity on 1p36.33-36.31 and 1q31.1-32.1 regions in order to explore precise deleted regions. Methods Seven fluorescenceqabeled polymorphic markers on 1p36.33-36.31 and 6 markers on 1 q31.1-32.1 were chosen. These polymorphic microsatellite markers in 83 cases of colorectal cancer tissues and normal tissues were analyzed by using PCR. PCR products were eletrophoresed for LOH scanning and analysis. Comparison between LOH frequency and clinicopathologic parameters was performed by X^2 test. Results The average LOH frequency of 1p36.33-36.31 was 31.47% ,with the highest LOH frequency of 47.22% （34/72） identified at D1S243,and the lowest of 7.35% （5/68） at D1S1347. Two distinct regions of frequent allelic deletion were found at D1 S243 （ 11736.33 ） and at D1 S468-D1 S2660 （ 1 p36.32-36.31 ）. The average LOH frequency of 1q31.1-32.1 was 22.98% ,with the highest frequency of 36.73% （18/49） at D1 S2622, and the lowest of 16.42% （11/67） at D1 S412 respectively. A minimal region of frequent deletion was located within a 2 cM genomic segment at D1S413-D1S2622 （ 1q31.3-32.1 ）. There was no significant association between LOH of each marker on 1p36.33-36.31 ,1q31.1-32. 1 and the clinicopathologic data （sex, age,tumor size,growth pattern or Dukes stage）, indicating that on 1p36.33-36.31 and 1 q31.1-32.1, LOH was a common phenomenon in all kinds of sporadic colorectal carcinoma. Conclusion Through the detailed deletion mapping,three critical and precise deleted regions were found： （1） D1S243 （ 1 cm） ; （ 2 ） D1 S468-D1 S2660 （ 3cm） ; and （ 3 ） D1 S413-D1 S2622 （ 2cm）. No significant association was found between LOH and elinieopathologie features. The regions identified in the present study could harbor one or more tumor suppressor gene（s） that would be associated with eoloreetal carcinoma.