B淋巴瘤6号染色体微卫星不稳定性及杂合性缺失

Microsatellite instability and loss of heterozygosity at chromosome 6 in B-cell lymphoma

目的:探讨6号染色体微卫星不稳定性(microsatelliteinstability,MSI)及杂合性缺失(lossofheterozygosity,LOH),碱基错配修复系统GTBP和hMLH1基因蛋白在B细胞淋巴瘤(Bcellnonhodgkin’slymphoma,BNHL)发生学上的意义。方法:选取6号染色体上7对多态微卫星标记,结合PCR及银染技术,采用凝胶成像图象分析系统,分别检测58例BNHL染色体微卫星MSI及LOH。对其中23例BNHL细胞进行EnVinsion法检测MMR的功能基因GTBP、hMLH1的表达情况。结果:弥漫性大B细胞淋巴瘤(diffuselargeBcelllymphoma,DLBCL)与滤泡性淋巴瘤(follicularlymphoma,FL)中GTBP和hMLH1蛋白表达差异无统计学意义,P值分别为0.98和1.30。原发生于淋巴结内与淋巴结外的GTBP、hMLH1蛋白表达差异无统计学意义,P值分别为0.54和0.67。GTBP蛋白在高、低度恶性表达之间差异无统计学意义,P=1.00;而hMLH1蛋白表达在低度恶性较高度恶性高,P=0.99。在位点D6S275MSI的发生率为7.5%(4/53),其中包括DLBCL2例,FL和BCLL/SLL各1例,LOH总的发生率达66.0%(35/53),其中包括DLBCL19例(19/21,90.5%),FL8例(8/13,61.5%),BCLL/SLL8例(8/19,42.1%),DLBCL的LOH率同BCLL/SLL和FL相比,差异有统计学意义,P=10.60。结论:hMLH1和GTBP错配修复基因蛋白表达与BNHL组织学类型、肿瘤的发生部位可能无关系。位点D6S275可能存在一个抑癌基因,该基因的缺失以及与错配修复基因hMLH1突变的关系对B细胞淋巴瘤的发生作用有待进一步研究。

OBJECTIVE： To evaluate the significance of loss of heterozygosity and microsatellite instability, mismatch repair system （MMR） GTBP and hMLH1 protein in the pathogenesis of B-cell lymphoma. METHODS： LOH and MSI were studied in 58 cases of B-cell lymphomas （21 cases of DLBCL, 13 cases of B-CLL/SLL, 19 cases of FL,3 cases of MALT, 1 case of B-PLL,B-LBL/ALL） by means of PCR amplification and silver staining at seven polymorphic microsatellites DNA loci on chromosome six. GTBP and hMLH1 about MMR were measured by the method of EnVinsion in 23 cases of these cases. RESULTS.. Between the DLBCL （P=0. 98） and FL （P= 1.30）, no any significant difference was found in GTBP and hMLH1 expressions. Between the nodal （P=0. 54） and extra-nodal （P=0. 67） sites, there was also no any significant difference detected in the GTBP and hMLH1 expression. Between the high and low grade group, there was no any significant difference found in GTBP, P=1. 00, however, the hMLH1 expression was higher in the low grade group than that in the high grade group, P=0.99. Four cases of lymphoma （including two cases of DLBCL, each one case of FL and B-CLL/SLL） showed MSI, but thirty-five cases of lymphomas （66% ,35/53） showed I,OH at the locus of D6S275. Molecular genomic change （LOH） at the locus was observed in 90. 5 % of the DLBCL （19/21）, in 61.5%（8/13） of FL and in 42.1% （8/19） of B-CLL/SLL. The frequency of LOH was significantly related to the types of lymphomas, P= 10.60. CONCLUSIONS： There is no any relationship befween the B-cell lymphoma histological categories, the location of tumor, and the GTBP/ hMLH1 expression concerned. There might be a tumor suppressor gene at D6S275 locus and it is to be verified whether it is important to the pathogenesis of B-cell lymphoma or not. It is not excluded that the loss of the tumor suppressor gene might not be relevant to the mutation of hMLH1, The other MMR genes might play a role in the loss of the tumor suppressor gene.