中国人结肠癌染色体12p12-13杂合性丢失的研究

目的通过对中国人结肠癌染色体12p12-13杂合性丢失（loss of heterozygosity,LDH）分析，了解KRAS2基因与结肠癌发生发展的关系。方法从10例结肠癌手术切除标本中，提取肿瘤、癌旁及相应正常组织的DNA，用PCR．变性聚丙烯酰胺凝胶电泳．免疫荧光标记多重微卫星PCR法，对染色体12p12-13杂合性丢失进行分析。结果10例癌旁组织中有3例（30％）在12p12-13处至少有一个位点出现杂合性丢失，其中D12S1034出现频率最高，为28．57％（2／7）；10例原发性结肠癌标本中6例（60％）在12p12-13处至少有一个位点出现有杂合性丢失，D12S1034和D12S1591是高频率丢失集中的区域，均占42．86％（3／7）；癌旁组织、癌组织均发生LDH的标本有3例，占30％（3／10）；仅在癌组织中发生LDH的标本有3例，占30％（3／10）；仅在癌旁组织中发生LDH，癌组织无信号的标本1例；杂合性丢失的频率与肿瘤患者的年龄、性别、肿瘤大小、肿瘤部位及淋巴结转移均无关。结论SRAS2基因所在的12p12-13区域在结肠癌发生发展过程中出现基因组不稳定，该区域的高频杂合性丢失可能直接影响野生型KRAS2基因的转录与翻译。

Loss of heterozygosity on chromosome 12p12-13 region in Chinese patients with colon carcinoma

Objective It is demonstrated that KRAS2, functioning as an oncogene, plays a critical role in carcinogenesis. However, some studies suggest that the wild type KRAS2, located in the region of 12p12.1, takes its effect as a tumor suppressor gene. This study, therefore, is aimed to investigate the loss of heterozygosity(LOH) on chromosome 12p12-13 region in 10 human colon carcinomas. Methods LOH analysis of the 12p12-13 region was performed by PCR, using 11 microsatellite markers in 12p12-13 region. The relationships between LOH for each marker and clinical pathologic factors were evaluated. Results LOH in at least one of the loci in 12p12-13 region was detected in 30% (3/10) of adjacent tissues; the highest frequency of LOH was identified at the locus of D12S1034 in 28.57%(2/7)of adjacent tissues. 60% (6/10) carcinoma tissues were found to have LOH in at least one locus in the same region; the most frequent LOH was found at the loci of D12S1034 and D12S1591, both about 42.86% (3/7). Among all samples, 3 cases were noted to have LOH in both adjacent and tumor tissues, and 3 cases were shown to have LOH only in tumor tissues. Occurrence of LOH was not correlated with sex, age, tumor size and lymph node metastasis. Conclusion Allelic loss on 12p12-13 region would influence the KRAS2 expression by reducing the gene-dosage in colon carcinogenesis.