AKAP12/Gravin is inactivated by epigenetic mechanism in human gastric carcinoma and shows growth suppressor activity
AKAP12/Gravin is inactivated by epigenetic mechanism in human gastric carcinoma and shows growth suppressor activity
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DOI：
10.1038/sj.onc.1207932
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发表时间：
2004-09-16
期刊：
影响因子：
8
通讯作者：
Bang, YJ
中科院分区：
文献类型：
--
作者：
Choi, MC;Jong, HS;Bang, YJ
AKAP 12/Gravin是A激酶锚定蛋白（AKAP）之一，作为激酶支架蛋白和β（2）-肾上腺素能受体复合物的动态调节剂发挥作用。然而，AKAP 12在癌症发展中的生物学作用还不清楚。AKAP 12基因编码305和287 kDa的两种主要亚型（在本报告中分别命名为AKAP 12 A和AKAP 12 B）。我们发现，这两种异构体是独立表达的，它们可能是在两个不同的启动子的控制下。此外，这两种亚型在大多数人胃癌细胞中均不存在。甲基化特异性PCR（MSP）和亚硫酸氢盐测序的结果显示，胃癌细胞中AKAP 12 A和AKAP 12 B的5' CpG岛经常发生高甲基化。用DNA甲基转移酶抑制剂和/或组蛋白去乙酰化酶抑制剂治疗有效地恢复了AKAP 12亚型的表达，证实了DNA甲基化直接参与胃癌细胞中AKAP 12的转录沉默。AKAP 12 A CpG岛的高甲基化也在56%（10/18）的原发性胃肿瘤中检测到。在AKAP 12非表达细胞中AKAP 12 A的恢复减少了集落形成并诱导了凋亡性细胞死亡。总之，我们的研究结果表明，AKAP 12 A可能作为一个重要的负调节人胃癌的生存途径。
AKAP12/Gravin, one of the A-kinase anchoring proteins (AKAPs), functions as a kinase scaffold protein and as a dynamic regulator of the beta(2)-adrenergic receptor complex. However, the biological role of AKAP12 in cancer development is not well understood. The AKAP12 gene encodes two major isoforms of 305 and 287 kDa ( designated AKAP12A and AKAP12B, respectively, in this report). We found that these two isoforms are independently expressed and that they are probably under the control of two different promoters. Moreover, both isoforms were absent from the majority of human gastric cancer cells. The results from methylation-specific PCR (MSP) and bisulfite sequencing revealed that the 5' CpG islands of both AKAP12A and AKAP12B are frequently hypermethylated in gastric cancer cells. Treatment with DNA methyltransferase inhibitor and/or histone deacetylase inhibitor efficiently restored the expression of AKAP12 isoforms, confirming that DNA methylation is directly involved in the transcriptional silencing of AKAP12 in gastric cancer cells. Hypermethylation of AKAP12A CpG island was also detected in 56% ( 10 of 18) of primary gastric tumors. The restoration of AKAP12A in AKAP12-nonexpressing cells reduced colony formation and induced apoptotic cell death. In conclusion, our results suggest that AKAP12A may function as an important negative regulator of the survival pathway in human gastric cancer.