Inactivation of the INK4a/ARF locus and p53 in sporadic extrahepatic bile duct cancers and bile tract cancer cell lines
Inactivation of the INK4a/ARF locus and p53 in sporadic extrahepatic bile duct cancers and bile tract cancer cell lines
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DOI：
10.1002/ijc.1639
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发表时间：
2002-02-01
影响因子：
6.4
通讯作者：
Berr, F
中科院分区：
文献类型：
--
作者：
Caca, K;Feisthammel, J;Berr, F
肿瘤抑制基因p14（ARF）、p16（INK 4a）和Tp 53通常在许多肿瘤中失活。我们研究了它们在9个胆管癌细胞系和21个原发性散发性肝外胆管癌发病机制中的作用。Western blot和免疫组化检测p53和p16蛋白表达。采用SSCP和直接测序法对p53基因进行突变筛查。p14和p16的失活机制通过筛选突变、纯合性缺失、9 p21染色体缺失（杂合性缺失[洛]分析）和p14/p16基因启动子高甲基化来解决。p53基因在9个细胞系中的7个和21个原发性肿瘤中的7个中检测到过表达，但仅在3个细胞系中检测到突变。由于9个细胞系中的8个细胞系中的基因纯合缺失和1个细胞系（CC-LP-1）中的p16启动子的超甲基化，所有细胞系中均不存在p16表达。p14外显子1 β在9个细胞系中的6个中同源缺失，而在CC-LP-1和另外2个细胞系中保留。未检测到p14基因启动子甲基化。21例原发性肿瘤中p16表达缺失。21例原发性肿瘤中有9例p16基因启动子甲基化，全部p16基因表达缺失。在21例原发性肿瘤中，13例检测到9 p21的等位基因丢失，11例p16表达丢失中有10例，9例p16启动子甲基化中有8例。未检测到p14启动子高甲基化或p14/p16突变。无论是TP 53还是p16的改变都没有表现出明显的组织病理学或临床特征。总之，p16基因失活是原发性散发性肝外胆管癌的常见事件，9 p21洛缺失和启动子甲基化是主要的失活机制。因此，p16，而不是p14，似乎是胆管癌中INK 4a焦点处失活的主要靶点。Tp 53突变以外的其他机制似乎主要负责胆管癌中核p53蛋白的稳定。(C)2002 Wiley-Liss，Inc.
The tumor-suppressor genes p14(ARF), p16(INK4a) and Tp53 are commonly inactivated in many tumors. We investigated their role in the pathogenesis of 9 bile tract cancer cell lines and 21 primary sporadic extrahepatic bile duct carcinomas. p53 and p16 protein expression was examined by Western blot analysis and immunohistochemistry. Mutation screening of p53 was done by SSCP and direct sequencing. Inactivating mechanisms of p14 and p16 were addressed by screening for mutations, homozygous deletions, chromosomal loss of 9p21 (loss of heterozygosity [LOH] analysis) and promoter hypermethylation of the p14/p16 genes. p53 overexpression could be detected in 7 of 9 cell lines and 7 of 21 primary tumors, but mutations were found in 3 cell lines only. p16 expression was absent in all cell lines, due to homozygous deletion of the gene in 8 of 9 cell lines and hypermethylation of the p16 promoter in one cell line (CC-LP-1). p14 exon 1beta was homozygously deleted in 6 of 9 cell lines, while retained in CC-LP-1 and 2 additional lines. No p14 promoter hypermethylation could be detected. p16 expression was lost in I I of 21 primary tumors. p16 promoter hypermethylation was present in 9 of 21 primary tumors, all with lost p16 expression. Allelic loss at 9p21 was detected in 13 of 21 primary tumors, 10 of 11 with lost p16 expression and 8 of 9 with methylated p16 promoter. No p14 promoter hypermethylation or p14/p16 mutations could be detected. Neither Tp53 nor p16 alterations showed obvious association with histopathologic or clinical characteristics. In conclusion, inactivation of the p16 gene is a frequent event in primary sporadic extrahepatic bile duct cancers, 9p21 LOH and promoter hypermethylation being the principal inactivating mechanisms. Therefore, p16, but not p14, seems to be the primary target of inactivation at the INK4a focus in bile duct cancers. Other mechanisms than Tp53 mutations seems to be predominantly responsible for stabilization of nuclear p53 protein in bile duct cancers. (C) 2002 Wiley-Liss, Inc.