Choi Jin-Sung, Kim Kyung-Hee, Jeon You-Kyung, Kim Sung-Hee, Jang Sang-Geun, Ku Ja-Lok, Park Jae-Gahb
Laboratory of Cell Biology, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea.
Int J Cancer. 2009 Mar 15;124(6):1258-62. doi: 10.1002/ijc.24023.
Promoter hypermethylation of the ADAM23 gene, which is normally involved in cell-to-cell and cell-to matrix adhesion, has been reported in pancreatic, breast and brain cancer, and recently the role of this gene was examined in gastric cancer. In this study, we analyzed ADAM23 expression in colorectal cancer cell lines and examined its methylation by methylation-specific PCR (MSP) and bisulfate-modified DNA sequencing analysis. Methylated cells were treated with 5-aza-2'-deoxycytidine to restore the ADAM23 expression. We then examined ADAM23 methylation status in colorectal cancer tissues and their corresponding normal tissues. We found that ADAM23 was aberrantly silenced or expressed at very low levels in 28 of the 32 (88%) colorectal cancer cell lines. MSP analysis showed that ADAM23 was methylated in 29 of 32 (91%) colorectal cancer cell lines and attenuated expression of ADAM23 was found to be related to hypermethylation in its promoter region. Moreover, the CpG dinucleotide methylation threshold of 70-90% was found to be required for complete silencing. In addition, when some cell lines without ADAM23 expression were treated with 5-aza-2'-deoxycytidine, ADAM23 was reexpressed. In colorectal cancer tissues, the promoter region of ADAM23 was hypermethylated in 36 of 76 (47%). These results demonstrated that ADAM23 may be down-regulated by aberrant promoter hypermethylation during the progression of colorectal cancer.
ADAM23基因的启动子高甲基化通常参与细胞间和细胞与基质的黏附，在胰腺癌、乳腺癌和脑癌中已有报道，最近该基因在胃癌中的作用也得到了研究。在本研究中，我们分析了结直肠癌细胞系中ADAM23的表达，并通过甲基化特异性PCR（MSP）和亚硫酸氢盐修饰的DNA测序分析检测了其甲基化情况。对甲基化细胞用5-氮杂-2'-脱氧胞苷处理以恢复ADAM23的表达。然后我们检测了结直肠癌组织及其相应正常组织中ADAM23的甲基化状态。我们发现，在32个结直肠癌细胞系中的28个（88%）中，ADAM23异常沉默或表达水平极低。MSP分析显示，32个结直肠癌细胞系中的29个（91%）ADAM23发生了甲基化，且ADAM23表达减弱与启动子区域的高甲基化有关。此外，发现完全沉默需要70-90%的CpG二核苷酸甲基化阈值。另外，当一些不表达ADAM23的细胞系用5-氮杂-2'-脱氧胞苷处理时，ADAM23重新表达。在结直肠癌组织中，76个样本中的36个（47%）ADAM23的启动子区域发生了高甲基化。这些结果表明，在结直肠癌进展过程中，ADAM23可能因启动子异常高甲基化而下调。
