Analysis of a new gene alteration related to fatty acid synthase in colorectal carcinogenesis.

[背景]我们利用一种高分辨率的限制性标志物基因组扫描(RLGS)技术在人肝细胞癌中发现了一种新的基因突变。[方法]从25例结直肠癌组织和相应的正常大肠黏膜组织中提取高分子量基因组DNA。每个DNA用限制性内切酶Not I酶切，用Pvu II进行一维电泳，然后用Pst I作为凝胶中的第三种酶切割DNA片段，并进行双向电泳分离。通过比较每对RLGS图谱，我们发现了6个共同的变异点。最频繁变化的斑点是直接从凝胶中克隆的。25例结直肠癌中有19例(76.0%)出现正常粘膜中未见的斑点改变。克隆了与该斑点对应的410个碱基DNA片段。该序列与人类部分脂肪酸合成酶基因(Fas)有69%的同源性，并定位于人类Draft序列第3条染色体的95%。B、C和F点分别占44%(11/25)、24%(6/25)和28%(7/25)，分别为271、168和374个DNA片段。B、C、F点的DNA序列也分别与第1、9号染色体的基因组重叠群和人类Not I克隆同源。[结论]克隆了4个点，其中1个与人类脂肪酸合成酶基因同源。这些基因突变与临床病理特征之间的关系将在未来通过制作这些斑点的抗体来研究。

[Background] We identified a new genetic alteration in human hepatocellular carcinoma by using a high resolution technique, restriction landmark genomic scanning (RLGS). The aim of this study was to identify new genetic alterations in colorectal cancer using the same method.[Methods] High molecular weight genomic DNAs were extracted from 25 colorectal cancerous tissues and corresponding normal mucosae. Each DNA was cleaved with the restriction enzyme Not I, size fractionated by 1st-dimensional electrophoresis using Pvu II, and the DNA fragments were then cleaved by Pst I as the third enzyme in gel and separated by 2-dimensional electrophoresis. By comparing each pair of RLGS profiles, we detected 6 common changed spots. The most frequently changed spot was directly cloned from the gel. Nineteen of 25 (76.0%) colorectal cancer cases showed a spot with the same alteration, which never appeared in normal mucosae. A 410-bp DNA fragment corresponding to this spot was cloned. This sequence was found to be 69% homologous to part of the human fatty acid synthase gene (FAS), and mapped to 95% of the 3rd chromosome of the human draft sequence. The three cloned spots (Spots B, C and F) were observed in 44%(11/25), 24% (6/25) and 28% (7/25) of the cases, respectively, and found to be 271-, 168-, and 374-bp DNA fragments. The DNA sequences from spots B, C and F were also homologous to the genomic contig of the first and the ninth chromosomes, and human Not I clones, respectively.[Conclusion] Four spots were cloned, one of which was found to homologous human fatty acid synthase gene. Relations between these gene mutations and clinicopathological features will be studied in the future by making antibodies of these spots.