Hu Peter, Lee Chang Woo, Xu Jing P, Simien Crystal, Fan Chuan Li, Tam Michael, Ramagli Louis, Brown Barry W, Lynch Patrick, Frazier Marsha L, Siciliano Michael J, Coolbaugh-Murphy Mary
Molecular Genetic Technology Program, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Unit 2, Houston, TX 77030, USA.
Ann Clin Lab Sci. 2011 Fall;41(4):321-30.
Microsatellites are short tandem repeats of deoxyribonucleic acid (DNA) sequences which are distributed throughout the genome. Tumors in patients with Lynch syndrome tend to accumulate mutations in microsatellites at a much higher rate than other sequences in the genome resulting in microsatellite instability (MSI). This is due to germline mutations in mismatch repair (MMR) genes. Using small pool-polymerase chain reaction (SP-PCR), previous studies have shown that mutant alleles can be detected in microsatellites of DNA from peripheral blood lymphocytes (PBLs) of Lynch syndrome patients at frequencies that were low, but significantly higher than frequencies in PBLs of age-matched non-Lynch syndrome controls. In the present study, SP-PCR detection of frequency of mutant MSI alleles (FMMA) was performed on PBLs and saliva samples from four sets of families. Each family set consisted of a mutation carrying affected proband (initial tumor bearer), a germline mutation-carrier sibling without tumors, and an age-matched normal control, either related (for 3 family sets) without mutation carrier status or unrelated (for 1 family set) without mutation carrier status. FMMAs of saliva and PBL DNA were compared between each proband, sibling and control for each family set, and between family sets. In all five statistically significant saliva comparisons identified between germline mutation carriers (FMMA: 0.080-0.261) and normal controls (FMMA: 0.003-0.087), the measured FMMAs were always higher in the carriers (p < 0.05). A logistic regression model of the data showed a significant increase in FMMAs in saliva DNA from siblings with MMR mutation compared to the normal controls (p < 0.001). These results indicated that the increased FMMAs observed in the saliva DNA as well as PBL DNA of MMR gene mutation carriers compared to normal controls are real and repeatable. Furthermore, the logistic regression also indicated that the FMMAs seen in saliva were nearly double those seen in PBLs (p < 0.001). Saliva testing, a less-invasive procedure than PBL testing, is more sensitive and appears to be a viable alternative for identifying MSI in carriers with MMR mutations.
微卫星是脱氧核糖核酸（DNA）序列的短串联重复序列，分布于整个基因组中。林奇综合征患者的肿瘤倾向于以比基因组中其他序列高得多的速率在微卫星中积累突变，从而导致微卫星不稳定（MSI）。这是由于错配修复（MMR）基因中的种系突变。使用小池聚合酶链反应（SP-PCR），先前的研究表明，在林奇综合征患者外周血淋巴细胞（PBL）的DNA微卫星中可以检测到突变等位基因，其频率较低，但明显高于年龄匹配的非林奇综合征对照的PBL中的频率。在本研究中，对四组家庭的PBL和唾液样本进行了SP-PCR检测突变型MSI等位基因频率（FMMA）。每组家庭由一名携带突变的患病先证者（初始肿瘤携带者）、一名无肿瘤的种系突变携带者同胞以及一名年龄匹配的正常对照组成，其中3组家庭的正常对照与先证者有亲缘关系且无突变携带者状态，1组家庭的正常对照与先证者无亲缘关系且无突变携带者状态。比较了每组家庭中每个先证者、同胞和对照之间以及不同家庭组之间唾液和PBL DNA的FMMA。在种系突变携带者（FMMA：0.080 - 0.261）和正常对照（FMMA：0.003 - 0.087）之间进行的所有五项具有统计学意义的唾液比较中，携带者的测量FMMA总是更高（p < 0.（此处原文有误，推测应为p < 0.05））。对数据进行的逻辑回归模型显示，与正常对照相比，MMR突变同胞唾液DNA中的FMMA显著增加（p < 0.001）。这些结果表明，与正常对照相比，在MMR基因突变携带者的唾液DNA以及PBL DNA中观察到的FMMA增加是真实且可重复的。此外，逻辑回归还表明，唾液中的FMMA几乎是PBL中的两倍（p < 0.001）。唾液检测是一种比PBL检测侵入性更小的方法，更敏感，似乎是识别MMR突变携带者中MSI的可行替代方法。
