Molecular and Population Genetics Laboratory, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.
PLoS One. 2010 Nov 5;5(11):e13840. doi: 10.1371/journal.pone.0013840.
We have previously shown that serum/glucocorticoid regulated kinase 1 (SGK1) is down-regulated in colorectal cancers (CRC) with respect to normal tissue. As hyper-methylation of promoter regions is a well-known mechanism of gene silencing in cancer, we tested whether the SGK1 promoter region was methylated in colonic tumour samples.
METHODOLOGY/PRINCIPAL FINDINGS: We investigated the methylation profile of the two CpG islands present in the promoter region of SGK1 in a panel of 5 colorectal cancer cell lines by sequencing clones of bisulphite-treated DNA samples. We further confirmed our findings in a panel of 10 normal and 10 tumour colonic tissue samples of human origin. We observed CpG methylation only in the smaller and more distal CpG island in the promoter region of SGK1 in both normal and tumour samples of colonic origin. We further identified a single nucleotide polymorphism (SNP, rs1743963) which affects methylation of the corresponding CpG.
CONCLUSIONS/SIGNIFICANCE: Our results show that even though partial methylation of the promoter region of SGK1 is present, this does not account for the different expression levels seen between normal and tumour tissue.
我们之前已经表明，血清/糖皮质激素调节激酶 1（SGK1）在结直肠癌（CRC）组织中相对于正常组织呈下调表达。由于启动子区域的高甲基化是癌症中基因沉默的一种众所周知的机制，我们检测了 SGK1 启动子区域是否在结肠肿瘤样本中发生甲基化。
方法/主要发现：我们通过对亚硫酸氢盐处理的 DNA 样本的克隆进行测序，研究了 5 种结直肠癌细胞系中 SGK1 启动子区域内存在的两个 CpG 岛的甲基化谱。我们进一步在 10 个人源正常和 10 个人源肿瘤结肠组织样本中证实了我们的发现。我们仅在结肠来源的正常和肿瘤样本的 SGK1 启动子区域较小且更远端的 CpG 岛上观察到 CpG 甲基化。我们进一步确定了一个单核苷酸多态性（SNP，rs1743963），它影响相应 CpG 的甲基化。
结论/意义：我们的结果表明，尽管 SGK1 启动子区域存在部分甲基化，但这并不能解释正常组织和肿瘤组织之间可见的不同表达水平。
