Molecular analysis of DNA mismatch repair gene on human malignant lymphoma occurring in maxillo-facial and oral region

已有报道在滤泡中心细胞起源的人类淋巴瘤中发现微卫星不稳定性，这表明DNA错配修复缺陷可能在这些肿瘤的发展中起作用。然而，滤泡性淋巴瘤(FL)中MMR基因表达缺失与以MMR基因功能缺陷为靶点的肿瘤抑制基因异常之间的联系尚未建立。我们评估了22例人类t(14；18)染色体易位阳性FL患者的hMSH2和hMLH1表达异常以及Bax和转化生长因子-b受体2型(TBR-II)基因编码区核苷酸重复序列(ID)突变。免疫组织化学(IHC)检测22例FL中6例(27%)恶性卵泡内hMSH2或hMLH1蛋白表达缺失。对hMSH2和hMLH1整个编码区进行测序，发现2例FL中2例hMSH2蛋白表达缺失，1例4例FL中…蛋白表达缺失。在6例正常表达的FL对照病例中，hMSH2和hMLH1均未发现突变。所有6例hMSH2或hMLH1蛋白表达缺失的FL患者均采用高保真PCR扩增重复区域，然后进行钝端克隆和测序，以检测BAX和TRB-II重复序列中的ID突变。其中5例FL患者存在Bax(G)8和/或TBR-II(A)10重复序列的ID突变，而hMSH2和hMLH1蛋白表达正常的6例对照FL患者均缺乏ID突变。IHC对Bax蛋白表达的评估显示，在6例有MMR基因功能缺陷的FL中，有4例(67%)表达缺失或明显减弱，包括两例伴有Bax ID突变的FL。相反，16例缺乏MMR基因功能缺陷证据的FL中只有3例(19%)Bax蛋白表达缺失或减弱。这些发现提示MMR基因功能缺陷在人类FL的发病机制中起重要作用，提示免疫组织化学筛查hMSH2和hMLH1蛋白表达可能是一种有效的方法来识别通过这一途径发生的FL病例。较少

Microsatellite instability has been reported in human lymphomas of follicular center cell origin suggesting that deficient DNA mismatch repair may play a role in the development of these tumors. However, a link between loss of MMR gene expression and abnormalities in tumor suppressor genes targeted by deficient MMR gene function has not been established in follicular lymphoma (FL). We evaluated 22 human t(14;18) chromosomal translocation positive FL cases for abnormalities in hMSH2 and hMLH1 expression and insertion/deletion (ID) mutations within the coding region nucleotide repeats of the BAX and TGF-b receptor type two (TbR-II) genes. Loss of hMSH2 or hMLH1 protein expression within the malignant follicles was identified in 6 of 22 (27%) FL cases by immunohistochemistry (IHC). Sequencing of the entire coding regions of hMSH2 and hMLH1 identified mutations in 2 of 2 FL cases that showed loss of hMSH2 protein expression and in 1 of 4 FL cases that showed loss of hMLH1 protein expressio … More n. There were no mutations in either hMSH2 or hMLH1 in six control FL cases that showed normal expression of these proteins. All six FL cases showing loss of hMSH2 or hMLH1 protein expression were evaluated for ID mutations within the BAX and TRb-II repeats using high fidelity PCR amplification over the repeat areas followed by blunt end cloning and sequencing. ID mutations within the BAX (G)8 and /or TbR-II (A)10 repeats were identified in five of these FL cases whereas all six control FL cases with normal hMSH2 and hMLH1 protein expression lacked ID mutations. Assessment of BAX protein expression by IHC showed absent or markedly diminished expression in 4 of 6 (67%) FL cases that had evidence of deficient MMR gene function, including both FL cases with BAX ID mutations. In contrast, only 3 of 16 (19%) FL cases that lacked evidence of deficient MMR gene function showed absent or diminished expression of BAX protein. These findings implicate deficient MMR gene function in the pathogenesis of human FL and suggest that IHC screening for hMSH2 and hMLH1 protein expression may represent an efficient method to identify FL cases that arise via this pathway. Less