Barberá V M, Martín M, Mariñoso L, Munné A, Carrato A, Real F X, Fabre M
Laboratorio de Oncologia Molecular y Celular, Universidad Miguel Hernández, Unidad de Investigación, Hospital Universitario de Elche, Alicante, Spain.
Biochim Biophys Acta. 2000 Oct 18;1502(2):283-96. doi: 10.1016/s0925-4439(00)00054-5.
The 18q21 region is frequently altered in gastrointestinal tumors. Three candidate tumor suppressor genes have been identified in it: DCC, Smad4/DPC4 and Smad2; the mechanisms involving their inactivation have not been completely elucidated. In this study, genetic losses at 18q21 and expression of DCC and DPC4 in colorectal (n=12) and pancreatic (n=16) cell lines and in colorectal tissues (n=10) were analyzed. The status of the 18q21 region was assessed using microsatellite analysis and duplex PCR of exonic sequences; expression was analyzed by RT-PCR; mutational analysis of DPC4 cDNA was performed in selected cases. Homozygous losses of microsatellite markers at 18q21 were not observed in colon or pancreas lines; however, a higher proportion of apparent homozygosity than expected was found. DCC and DPC4 transcripts were detected in 11/12 and 12/12 colorectal cancer lines, respectively. In tumors, homozygous losses at 18q21 were detected in three cases, without affecting DCC. All tumors retained DCC and DPC4 mRNA expression. In pancreatic lines, DPC4 was inactivated through homozygous deletion (n=5), intragenic mutation (n=3), and lack of protein (n=2).
(1) microsatellite analysis does not provide adequate information regarding homozygous losses at 18q21; (2) approximately 65% of pancreas cancer lines show inactivation of DPC4; and (3) loss of DCC and DPC4 occur independently.
18q21区域在胃肠道肿瘤中经常发生改变。在该区域已鉴定出三个候选肿瘤抑制基因：DCC、Smad4/DPC4和Smad2；但其失活机制尚未完全阐明。在本研究中，分析了18q21区域的基因缺失以及DCC和DPC4在结肠（n = 12）和胰腺（n = 16）细胞系及结肠组织（n = 10）中的表达情况。使用微卫星分析和外显子序列的双重PCR评估18q21区域的状态；通过RT-PCR分析表达情况；对选定病例进行DPC4 cDNA的突变分析。在结肠或胰腺细胞系中未观察到18q21处微卫星标记的纯合缺失；然而，发现明显纯合性的比例高于预期。分别在11/12和12/12的结肠癌细胞系中检测到DCC和DPC4转录本。在肿瘤中，在三例中检测到18q21处的纯合缺失，但不影响DCC。所有肿瘤均保留DCC和DPC4 mRNA表达。在胰腺细胞系中，DPC4通过纯合缺失（n = 5）、基因内突变（n = 3）和缺乏蛋白（n = 2）而失活。
（1）微卫星分析不能提供关于18q21处纯合缺失的充分信息；（2）约65%的胰腺癌细胞系显示DPC4失活；（3）DCC和DPC4的缺失是独立发生的。
