肺增生病变FHIT基因微卫星不稳定和杂合性丢失的研究

Microsatellite instability and loss of heterozygosity of fragile histidine triad gene in lung hyperplastic lesions

目的检测FHIT基因在肺癌支气管上皮增生病变和肺炎支气管上皮增生病变是否存在差异,试图确定发生“真正癌变”的癌前病变,为肺癌前病变的风险性预测提供实验依据。方法采用聚合酶链反应银染技术结合二核苷酸(CA)n重复序列出现多态性,评价杂合性丢失(LOH)和微卫星不稳定(MI)。分析82例肺癌增生病变和57例肺炎增生病变的FHIT基因微卫星位点的LOH和MI现象。结果联合检测微卫星位点D3S1234、D3S1300、D3S1481、D3S1313的FHIT基因阳性率(LOH和MI总发生率),在肺癌组的各级增生病变均明显大于肺炎组的相应各级增生病变,有显著性差异(P<0.01)。肺癌组基底细胞增生、鳞状上皮化生、轻-中度不典型增生FHIT阳性率分别为33%(4/12) 、54%(7/13)、70%(7/10);肺炎组相应增生病变分别为7%(1/14)、12%(2/16)、18%(2/11)。在肺癌组,4个位点的FHIT阳性率比较,分别为41%(34/82)、37%(30/82)、38%(31/82)、34(28/82),无显著性差异(P>0.05)。4个微卫星位点在肺癌增生组的LOH发生率均明显大于MI发生率(P<0.01)。结论FHIT基因的LOH现象普遍存在于癌旁支气管上皮各级增生病变中,明显高于肺炎支气管上皮增生病变,表明肺癌前病变确实存在差异。此结果为FHIT基因作为判断“真正癌前病变”的检测指标提供了实验依据。

Objective To ascertain weather there is any difference in the hyperplastic lesions in the bronchial endothelia between patients with lung cancer and those with pneumonia, so as to find reliable molecular marker for early diagnosis of 'genuine' preneoplastic lesions. Methods With PCR-denaturing polyacrylamide gel electrophoresis and silver-staining, 82 specimens of bronchial hyperplastic lesions obtained from patients with squamous cell carcinoma (SCC) and 57 matched epithelial lesion specimens obtained from patients with pneumonia were examined for loss of heterozygosity (LOH) and microsatellite instability (MI) of fragile histidine triad (FHIT) gene. Results Allelic losses of FHIT were common in hyperplastic lesions from patients with SCC, and the frequencies of LOH and MI of the 4 microsatellite sites, D3S1234, D3S1300, D3S1481, and D3S1313 were significant higher in hyperplastic lesions from SCC patients than in those from pneumonia patients (P<0.01). The frequencies of LOH and MI of FHIT gene in cancerous and noncancerous squamous metaplasia were 54%(7/13) and 12%(2/16) respectively, and were 70%(7/10) and 18%(2/8) respectively in cancerous and noncancerous mild to moderate dysplastic lesions. No significant difference was observed between the frequencies of D3S1234, D3S1300, D3S1481, and D3S1313 in cancerous hyperplastic lesions, which were 41%(34/82), 37%(30/82), 38%(31/82), 34(28/82), respectively (P>0.05). Conclusion Hyperplastic lesions showed higher frequency of LOH at the 4 microsatellite sites than MI (P<0.01). The fact that LOH of FHIT is prevalent in hyperplastic lesions in SCC patients but rare in pneumonic patients indicates the significant difference between cancerous and noncancerous hyperplastic lesions. LOH of FHIT may be an early event in the development of squamous cell carcinoma in the lungs and is crucial in the early stage of carcinogenesis, validating the use of FHIT as a molecular marker to identify 'genuine' preneoplastic lesions.