Identification of a candidate tumor suppressor gene RHOBTB1 located at a novel allelic loss region 10q21 in head and neck cancer
Identification of a candidate tumor suppressor gene RHOBTB1 located at a novel allelic loss region 10q21 in head and neck cancer
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DOI：
10.1007/s00432-005-0033-0
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发表时间：
2006-01-01
影响因子：
3.6
通讯作者：
Shimizu, K
中科院分区：
文献类型：
--
作者：
Beder, LB;Gunduz, M;Shimizu, K
目的：缩小以往全基因组杂合性缺失(LOH)分析在头颈部鳞状细胞癌(HNSCC)中确定的10q21上的热点区域，并确定与10q21相关的候选肿瘤抑制基因(TSG)。材料和方法：利用10个多态微卫星标记进行杂合性缺失分析。半定量逆转录聚合酶链式反应分析基因表达，聚合酶链式反应和直接测序分析基因突变。结果：52例HNSCC患者10q21上的杂合性缺失分析显示，D10S589存在明显而频繁的等位基因缺失(42%)。在侧翼基因中，我们发现RHOBTB1基因是TSG的候选基因，因为一个基因内标记显示了最高的LOH(44%)。表达分析显示RHOBTB1mRNA在37%的肿瘤中表达下调。有趣的是，RHOBTB1表达降低的五种肿瘤都伴有LOH，支持RHOBTB1的单倍体不足和第二类TSG特征。未发现RHOBTB1致病突变。此外，该区域内的另一个基因EGR2也被纳入研究范围。EGR2基因周围的杂合性缺失频率相对较低(23%和33%)。尽管半定量分析显示45%的肿瘤标本中EGR2表达下调，但未发现其表达水平与LOH状态之间的关系。结论：RHOBTB1基因频繁的等位基因丢失和表达降低提示该基因在HNSCC的一个亚群的发生发展中起一定作用。
Purpose: Aims of the study are to narrow-down the hotspot region on 10q21 defined by previous genome-wide loss of heterozygosity (LOH) analysis in head and neck squamous cell carcinomas (HNSCC) and to define candidate tumor suppressor genes (TSG) concerned with 10q21. Materials and methods: LOH analysis was carried out with ten polymorphic microsatellite markers. Expression analysis was performed by semi-quantitative RT-PCR, and mutation analysis by PCR and direct sequencing. Results: LOH analysis on 10q21 in 52 HNSCC indicated distinctive and frequent allelic loss at D10S589 (42%). Among flanking genes, we found the RHOBTB1 gene as a candidate TSG, since an intragenic marker demonstrated the highest LOH (44%). Expression analysis revealed down-regulation of RHOBTB1 mRNA in 37% of tumors. Interestingly, all the five tumors that showed decreased expression of RHOBTB1 were accompanied with LOH, supporting the haploinsufficiency and class 2 TSG characteristics of RHOBTB1. No pathogenic mutation of RHOBTB1 was found. Furthermore, another gene within the region, EGR2, was also taken under scope. LOH frequencies around the EGR2 gene were relatively low (23 and 33%). Albeit semi-quantitative expression analysis of EGR2 demonstrated downregulation in 45% of tumor samples, no relation was found between the expression levels and LOH status. Conclusion: Frequent allelic loss and decreased expression of RHOBTB1 suggested that this gene has a role in tumorigenesis of a subset of HNSCC.