Department of Oncogene Regulation, Chittaranjan National Cancer Institute, Kolkata, India.
Int J Cancer. 2011 Oct 15;129(8):1859-71. doi: 10.1002/ijc.25849. Epub 2011 Apr 1.
To understand the importance of frequent deletion of chromosomal 11q23.3-24.3 region in cervical carcinogenesis, alterations (deletion/methylation/mutation/expression) of the candidate genes LOH11CR2A, EI24 and CHEK1 located in the region were analyzed in 29 cervical intraepithelial neoplasia (CIN), 112 cervical carcinoma (CACX) samples and two CACX cell lines. The deletion frequency of these genes was low in CIN than in CACX [CIN: CHEK1: 28%, EI24: 21%, LOH11CR2A: 15% and CACX: CHEK1: 51%, EI24: 41%, LOH11CR2A: 36%]. Similar trend was seen in promoter methylation of these genes [CIN: CHEK1: 10%, EI24: 3%, LOH11CR2A: 3% and CACX: CHEK1: 55%, EI24: 31%, LOH11CR2A: 14%]. Mutations of the genes are a rare event. Overall alterations (deletion and methylation) of CHEK1 and EI24 were associated with progression of CACX. Quantitative mRNA expression analysis showed reduced expression of the three genes in concordance to their molecular alterations. A shorter isoform of CHEK1 lacking exon 8, hence impaired in substrate binding capacity, was found in two samples. Immunohistochemical analysis showed nuclear expression of Chek1, p-Chek1 and Ei24 in tumor tissues, whereas the cell lines exhibited both nuclear and cytoplasmic expression of Chek1 and Ei24, as is also evident from Western blot analysis suggesting differential localization of the proteins. Alterations of CHEK1 and EI24 coupled with tumor stage and early sexual debut (≤ 19 years) predicted worst prognosis. Thus, our data suggest that inactivation of EI24 and CHEK1 through two independent mechanisms contributes to the development of CACX.
为了理解染色体 11q23.3-24.3 区域频繁缺失在宫颈癌发生中的重要性，我们分析了该区域候选基因 LOH11CR2A、EI24 和 CHEK1 的改变（缺失/甲基化/突变/表达），这些改变在 29 例宫颈上皮内瘤变（CIN）、112 例宫颈癌（CACX）样本和 2 个 CACX 细胞系中发生。这些基因在 CIN 中的缺失频率低于 CACX [CIN： CHEK1：28%，EI24：21%，LOH11CR2A：15%，CACX： CHEK1：51%，EI24：41%，LOH11CR2A：36%]。这些基因的启动子甲基化也存在类似的趋势 [CIN： CHEK1：10%，EI24：3%，LOH11CR2A：3%，CACX： CHEK1：55%，EI24：31%，LOH11CR2A：14%]。这些基因的突变是罕见事件。总的来说， CHEK1 和 EI24 的改变（缺失和甲基化）与 CACX 的进展有关。定量 mRNA 表达分析显示，这三个基因的表达与其分子改变一致降低。在两个样本中发现了缺乏外显子 8 的 CHEK1 较短同工型，因此在底物结合能力上受损。免疫组织化学分析显示肿瘤组织中 Chek1、p-Chek1 和 Ei24 的核表达，而细胞系则显示 Chek1 和 Ei24 的核和细胞质表达，这也可以从 Western blot 分析中看出，提示蛋白质的不同定位。 CHEK1 和 EI24 的改变加上肿瘤分期和早期性接触（≤19 岁）预测预后最差。因此，我们的数据表明，通过两种独立的机制失活 EI24 和 CHEK1 有助于 CACX 的发展。
