Frequent silencing of a putative tumor suppressor gene melatonin receptor 1 A (MTNR1A) in oral squamous-cell carcinoma
Frequent silencing of a putative tumor suppressor gene melatonin receptor 1 A (MTNR1A) in oral squamous-cell carcinoma
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DOI：
10.1111/j.1349-7006.2008.00838.x
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发表时间：
2008-07-01
期刊：
影响因子：
5.7
通讯作者：
Imoto, Issei
中科院分区：
文献类型：
--
作者：
Nakamura, Erina;Kozaki, Ken-ichi;Imoto, Issei
基于阵列的比较基因组杂交技术（array-CGH）在高通量鉴定细胞基因组中的遗传畸变方面具有良好的潜力。在一个项目的过程中，筛选一组21口腔鳞状细胞癌（OSCC）细胞系的全基因组拷贝数畸变阵列CGH使用我们的内部细菌人工染色体阵列，我们确定了一个频繁的纯合性缺失在4 q35位点约1 Mb的程度。在位于该区域的7个基因中，褪黑激素受体1A（MTNR 1A）信使RNA（mRNA）的表达在39个（89%）OSCC细胞系中的35个（89%）中未检测到或降低，但在永生化的正常口腔上皮细胞系中检测到，并且在基因沉默的OSCC细胞中恢复，而在5-氮杂-2 '-脱氧胞苷处理后没有其纯合丢失。MTNR 1A基因启动子区CpG岛的甲基化程度与其在无纯合缺失的OSCC细胞系中的表达呈负相关。在原发性OSCC组织中也观察到该CpG岛的甲基化。在对50例原发性OSCC肿瘤的免疫组化分析中，免疫反应性MTNR 1A的缺失与OSCC肿瘤患者的肿瘤大小和较短的总生存期显著相关，在多变量分析中似乎是一个独立的预测因子。MTNR 1A表达的外源性恢复抑制了缺乏其表达的OSCC细胞的生长。结合已知的褪黑激素和MTNR 1A在各种肿瘤中的肿瘤抑制功能，我们的研究结果表明MTNR 1A是4 q35表观遗传沉默的最可能靶点，并在口腔癌发生过程中发挥关键作用。
Array-based comparative genomic hybridization (array-CGH) has good potential for the high-throughput identification of genetic aberrations in cell genomes. In the course of a program to screen a panel of 21 oral squamous-cell carcinoma (OSCC) cell lines for genome-wide copy-number aberrations by array-CGH using our in-house bacterial artificial chromosome arrays, we identified a frequent homozygous deletion at 4q35 loci with approximately 1 Mb in extent. Among the seven genes located within this region, the expression of the melatonin receptor 1 A (MTNR1A) messenger RNA (mRNA) was not detected or decreased in 35 out of the 39 (89%) OSCC cell lines, but was detected in immortalized normal oral epithelial cell line, and was restored in gene-silenced OSCC cells without its homozygous loss after treatment with 5-aza-2'-deoxycytidine. The hypermethylation of the CpG (cytosine and guanine separated by phosphate) island in the promoter region of MTNR1A was inversely correlated with its expression in OSCC lines without a homozygous deletion. Methylation of this CpG island was also observed in primary OSCC tissues. In an immunohistochemical analysis of 50 primary OSCC tumors, the absence of immunoreactive MTNR1A was significantly associated with tumor size and a shorter overall survival in patients with OSCC tumors, and seems to be an independent prognosticator in a multivariate analysis. Exogenous restoration of MTNR1A expression inhibited the growth of OSCC cells lacking its expression. Together with the known tumor-suppressive function of melatonin and MTNR1A in various tumors, our results indicate MTNR1A to be the most likely target for epigenetic silencing at 4q35 and to play a pivotal role during oral carcinogenesis.