放疗后复发鼻咽癌微卫星不稳定和杂合性缺失改变的研究

目的比较放疗后复发鼻咽癌（NPC）与初诊NPC中染色体微卫星不稳定（MSI）和杂合性缺失（LOH）发生情况。方法选择1p、3p、3q、4q、9q、11q、13q、14q的12个微卫星多态性位点,显微切割分离22例初诊和18例放疗后复发NPC组织和正常组织,提取DNA,经PCR扩增及聚丙烯酰胺凝胶电泳和硝酸银染色,进行MSI及LOH分析研究。结果（1）8个位点发生了LOH：复发癌与初诊癌相比,LOH发生率在D1S2697位点为28.6%比20.0%,在D13S133位点为30.0%比20.0%,在D9S1682位点为7.7%比9.1%;D5S433和D14S65位点只在复发癌中发生LOH,分别为33.3%和6.7%;D13S263、D4S350、D14S258位点只在初诊癌发生LOH,分别为20.0%、33.3%、16.6%。（2）11个位点发生了MSI：4个位点在复发癌和初诊癌中都发生MSI,4个位点只在复发癌中发生MSI,3个位点只在初诊癌中发生MSI。结论 D1S2697、D13S133、D5S433位点可能含有与放疗后复发NPC相关的肿瘤抑制基因,放疗后复发NPC中MSI发生率呈增高趋势,提示部分放疗后复发NPC与原发癌可能属不同细胞克隆起源。

Microsatellite instability and loss of heterozygosity in recurrent nasopharyngeal carcinoma after radiotherapy

Objective To compare the microsatellite instability（MSI） and loss of heterozygosity（LOH） between recurrent nasopharyngeal carcinoma（NPC-R） after radiotherapy and primary nasopharyngeal carcinomas（NPC-P）. Methods Twelve microsatellite markers in the chromosomes 1p, 3p, 3q, 4q, 9q, 11 q, 13 q, and 14 q were selected. The tumor tissues of 22 NPC-P and 18 NPC-R cases and normal tissues isolated by microdissection. The extracted DNA was amplified by PCR, and MSI and LOH were analyzed by polyacrylamide gel electrophoresis and silver nitrate staining. Results（1） LOH occurred in 8 microsatellites. The frequency of LOH in NPC-R and NPC-P was 28.6% and 20.0% at D1S2697, 30.0% and 20.0% at D13S133, and 7.7% and 9.1% at D9S1682, respectively. The frequency of LOH was 33.3% at D5S433 and 6.7% at D14S258 in NPC-R, while frequency of LOH was 20.0% at D13S263, 33.3% at D4S350 and 16.6% at D14S258 in NPC-P.（2） MSI was found in 7 microsatellites, including 4 loci in both NPC-R and NPC-P, 4 in NPC-R, and 3 in NPC-P. Conclusion D1S2697, D13S133 and D5S433 loci might harbor the NPC recurrence-related tumor suppressor genes after radiotherapy. The MSI tends to develop in NPV-R, suggesting that NPC-R might be partly different from NPC-P in the clone origin.