Frequent silencing of low density lipoprotein receptor-related protein 1B (LRP1B) expression by genetic and epigenetic mechanisms in esophageal squamous cell carcinoma
Frequent silencing of low density lipoprotein receptor-related protein 1B (LRP1B) expression by genetic and epigenetic mechanisms in esophageal squamous cell carcinoma
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DOI：
10.1158/0008-5472.can-04-0172
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发表时间：
2004-06-01
期刊：
影响因子：
11.2
通讯作者：
Inazawa, J
中科院分区：
文献类型：
--
作者：
Sonoda, I;Imoto, I;Inazawa, J
低密度脂蛋白受体相关蛋白1B(LRP1B)在各种类型的肿瘤中经常缺失，但其在食管鳞癌(ESCs)中的状态和表达尚未见报道。在使用基于阵列的比较基因组杂交筛选ESC细胞系拷贝数异常的程序过程中，我们鉴定了LRP1B的纯合子缺失。基因组聚合酶链式反应显示LRP1B在额外的ESC细胞系(共6/43，14.0%)和原发食道肿瘤(30/70，42.9%)中纯合缺失。此外，在无纯合子缺失的ESC系中，LRP1B基因的表达经常被沉默(14/37；37.8%)。利用亚硫酸氢盐-聚合酶链式反应分析和测序，我们发现没有纯合缺失的LRP1B非表达细胞在LRP1B的CpG岛上高度甲基化，这是一个具有启动子活性的序列。经5-氮-2‘-脱氧胞苷处理后，这些ESC细胞中LRP1B的表达恢复。组蛋白乙酰化状态与LRP1B表达正相关，与CpG岛甲基化状态负相关。LRP1B基因甲基化在原发性食道肿瘤中也被检测到。在ESC细胞中恢复LRP1B的表达减少了克隆形成。这些结果表明，在食道癌的发生中，LRP1B功能的丧失通常是通过纯合缺失或通过其CpG岛的高甲基化导致转录沉默而发生的。
Low-density lipoprotein receptor-related protein 1B (LRP1B) is frequently deleted in tumors of various types, but its status and expression in esophageal squamous cell carcinomas (ESCs) have never been reported. In the course of a program to screen ESC cell lines for copy-number aberrations using array-based comparative genomic hybridization, we identified a homozygous deletion of LRP1B. Genomic PCR experiments revealed homozygous deletions of LRP1B in additional ESC cell lines (total, 6 of 43; 14.0%) and in primary esophageal tumors (30 of 70; 42.9%). Moreover, expression of LRP1B mRNA was frequently silenced in ESC lines without homozygous deletions (14 of 37; 37.8%). Using bisulfite-PCR analysis and sequencing, we found that LRP1B-nonexpressing cells without homozygous deletions were highly methylated at a CpG island of LRP1B, a sequence possessing promoter activity. Treatment with 5-aza-2'-deoxycytidine restored expression of LRP1B in those ESC lines. Histone acetylation status correlated directly with expression of LRP1B and inversely with the methylation status of the CpG island. Methylation of LRP1B was also detected in primary esophageal tumors. Restoration of LRP1B expression in ESC cells reduced colony formation. These results suggest that loss of LRP1B function in esophageal carcinogenesis most often occurs either by homozygous deletion or by transcriptional silencing through hypermethylation of its CpG island.