Naidoo R, Tarin M, Chetty R
Department of Pathology, University of Natal School of Medicine, Durban, South Africa.
Am J Gastroenterol. 2000 Nov;95(11):3266-75. doi: 10.1111/j.1572-0241.2000.03208.x.
This study was undertaken to investigate microsatellite instability and allelic imbalance in a cohort of young patients (<35 yr) and older patients (>50 yr) with sporadic colorectal carcinomas in the Kwa-Zulu Natal region of South Africa.
Normal and tumor DNA was isolated from formalin-fixed, paraffin-embedded tissue from 32 patients <35 yr and from 50 patients >50 yr of age. Tumors were staged using the modified Astler-Coller classification. Fluorescent-based DNA technology using an automated DNA sequencer (Alf Express Automated DNA Sequencer) was employed. CY5 labeled primers for microsatellite markers in chromosomes 18, 3, and 2 (DCC, D18S34, D18S58, D3S659, D3S1255, and D2S123) were used. The data were captured and analyzed using the Fragment Manager Software.
The informativity of the microsatellite markers ranged from 50% to 71.8%. Microsatellite instability was seen in 44 of 82 cases (53.7%) for at least one of the six markers. Low frequency MSI (MSI-L) was seen in 28 of 82 cases (34.2%) and high frequency MSI (MSI-H) in 16 of 82 cases (19.5%). In the <35-yr age group, MSI-L was seen in six cases (18.8%) and MSI-H in 10 cases (31.3%). In the >50 yr age group, MSI-L was seen in 22 cases (44%) and MSI-H in six cases (12%). Twelve cases showed AI for DCC, seven showed AI for D18S34, and four showed AI for D18S58. MSI was found in 13, 10, and 16 cases for each of these markers, respectively. Allelic imbalance for the D3S659, D2S123, and D3S1255 loci was 3 of 82 cases (3.7%), 10 of 82 cases (12.2%), and 13 of 80 cases (16.3%), respectively. MSI was 14.6% for both D3S659 and D2S123 and was 6.3% for the D3S1255 marker.
Loss of heterozygosity in the region of the DCC locus ranged from 9.3% to 26.7%, and MSI ranged from 12.2% to 19.5% of cases. Allelic imbalance in the region of the repair genes ranged from 6.8% to 27% in the informative cases. MSI, however, ranged from 5% to 12%. These figures are similar to those of other studies done in other parts of the world. Further, no correlation was found between the genetic results and clinicopathological parameters: i.e., tumor stage, grade and clinical parameters of age and gender. However, genetic abnormalities were more common in the younger cohort of patients, and this may translate into the earlier age of presentation. This opens the potential for genetic screening.
本研究旨在调查南非夸祖鲁 - 纳塔尔地区散发性结直肠癌的年轻患者（<35岁）和老年患者（>50岁）队列中的微卫星不稳定性和等位基因失衡情况。
从32例<35岁患者和50例>50岁患者的福尔马林固定、石蜡包埋组织中分离正常和肿瘤DNA。肿瘤采用改良的阿斯特勒 - 科勒分类法进行分期。使用自动DNA测序仪（Alf Express自动DNA测序仪）的基于荧光的DNA技术。使用CY5标记的18号、3号和2号染色体微卫星标记（DCC、D18S34、D18S58、D3S659、D3S1255和D2S123）的引物。使用片段管理器软件捕获和分析数据。
微卫星标记的信息性范围为50%至71.8%。8两组患者的微卫星不稳定性在82例中的44例（53.7%）中至少六个标记之一中可见。82例中的28例（34.2%）出现低频微卫星不稳定性（MSI - L），82例中的16例（19.5%）出现高频微卫星不稳定性（MSI - H）。在<35岁年龄组中，6例（18.8%）出现MSI - L，10例（31.3%）出现MSI - H。在>50岁年龄组中，22例（44%）出现MSI - L，6例（12%）出现MSI - H。12例显示DCC基因座的等位基因失衡，7例显示D18S34基因座的等位基因失衡，4例显示D18S58基因座的等位基因失衡。这些标记物分别在13例、10例和16例中发现微卫星不稳定性。D3S659、D2S123和D3S1255基因座的等位基因失衡分别为82例中的3例（3.7%）、82例中的10例（12.2%）和80例中的13例（16.3%）。D3S659和D2S123的微卫星不稳定性均为14.6%，D3S1255标记物的微卫星不稳定性为6.3%。
DCC基因座区域的杂合性缺失范围为9.3%至26.7%，微卫星不稳定性在病例中占12.2%至19.5%。在信息性病例中，修复基因区域的等位基因失衡范围为6.8%至27%。然而，微卫星不稳定性范围为5%至12%。这些数字与世界其他地区进行的其他研究结果相似。此外，未发现基因结果与临床病理参数之间的相关性，即肿瘤分期、分级以及年龄和性别的临床参数。然而，基因异常在较年轻的患者队列中更为常见，这可能转化为更早的发病年龄。这为基因筛查开辟了潜力。
