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技术——限制性地标基因组扫描（RLGS），在人肝细胞癌中发现了一种新的基因改变。这项研究的目的是用同样的方法识别结直肠癌中新的基因改变。[方法]从25个结直肠癌组织和相应的正常粘膜组织中提取高分子量基因组dna。每个DNA用内切酶Not I切割，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片段并进行二维电泳分离。通过对比每对RLGS剖面，我们发现了6个共同的变化点。变化最频繁的斑点直接从凝胶中克隆出来。25例结直肠癌患者中有19例（76.0%）出现了正常粘膜中从未出现过的斑点。克隆出与该位点相对应的410 bp的DNA片段。该序列与人类脂肪酸合成酶基因（FAS）的部分同源性为69%，定位于人类草图序列第3染色体的95%。B点、C点和F点分别在44%（11/25）、24%（6/25）和28%（7/25）的病例中发现，分别为271、168和374 bp的DNA片段。B点、C点和F点的DNA序列也分别与第1条和第9条染色体的基因组序列和人类Not I克隆的基因组序列同源。【结论】共克隆了4个位点，其中1个位点与人脂肪酸合酶基因同源。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.