Department of Cancer and Thoracic Surgery, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Shikata-cho, Okayama, Japan.
J Cancer Res Clin Oncol. 2012 May;138(5):799-809. doi: 10.1007/s00432-012-1158-6. Epub 2012 Jan 25.
The REIC (reduced expression in immortalized cells)/Dkk-3 is down-regulated in various cancers and considered to be a tumor suppressor gene. REIC/Dkk-3 mRNA has two isoforms (type-a,b). REIC type-a mRNA has shown to be a major transcript in various cancer cells, and its promoter activity was much stronger than that of type-b. In this study, we examined the methylation status of REIC/Dkk-3 type-a in a broad range of human malignancies.
We examined REIC/Dkk-3 type-a methylation in breast cancers, non-small-cell lung cancers, gastric cancers, colorectal cancers, and malignant pleural mesotheliomas using a quantitative combined bisulfite restriction analysis assay and bisulfate sequencing. REIC/Dkk-3 type-a and type-b expression was examined using reverse transcriptional PCR. The relationships between the methylation and clinicopathological factors were analyzed.
The rate of REIC/Dkk-3 type-a methylation ranged from 26.2 to 50.0% in the various primary tumors that were examined. REIC/Dkk-3 type-a methylation in breast cancer cells was significantly heavier than that in the other cell lines that we tested. REIC/Dkk-3 type-a methylation was inversely correlated with REIC/Dkk-3 type-a expression. There was a correlation between REIC/Dkk-3 type-a and type-b mRNA expression. REIC/Dkk-3 type-a expression was restored in MDA-MB-231 cells using 5-aza-2'-deoxycytidine treatment. We found that estrogen receptor-positive breast cancers were significantly more common among the methylated group than among the non-methylated group.
REIC/Dkk-3 type-a methylation was frequently detected in a broad range of cancers and appeared to play a key role in silencing REIC/Dkk-3 type-a expression in these malignancies.
REIC（永生化细胞中表达减少）/Dkk-3 在多种癌症中下调，被认为是一种肿瘤抑制基因。REIC/Dkk-3 mRNA 有两种亚型（a、b 型）。REIC-a mRNA 在各种癌细胞中表现为主要转录本，其启动子活性比 b 型强得多。在这项研究中，我们检查了广泛的人类恶性肿瘤中 REIC/Dkk-3 a 型的甲基化状态。
我们使用定量联合亚硫酸氢盐限制性分析测定和亚硫酸氢盐测序法检查乳腺癌、非小细胞肺癌、胃癌、结直肠癌和恶性胸膜间皮瘤中 REIC/Dkk-3 a 型的甲基化。使用逆转录 PCR 检查 REIC/Dkk-3 a 和 b 型的表达。分析了甲基化与临床病理因素之间的关系。
在所检查的各种原发性肿瘤中，REIC/Dkk-3 a 型的甲基化率为 26.2%至 50.0%。乳腺癌细胞中 REIC/Dkk-3 a 型的甲基化明显重于我们测试的其他细胞系。REIC/Dkk-3 a 型甲基化与 REIC/Dkk-3 a 型表达呈负相关。REIC/Dkk-3 a 和 b mRNA 表达之间存在相关性。使用 5-氮杂-2'-脱氧胞苷处理 MDA-MB-231 细胞可恢复 REIC/Dkk-3 a 表达。我们发现，雌激素受体阳性的乳腺癌在甲基化组中比非甲基化组更为常见。
广泛的癌症中经常检测到 REIC/Dkk-3 a 甲基化，并且似乎在这些恶性肿瘤中沉默 REIC/Dkk-3 a 表达中起关键作用。
