Schneider-Stock R, Kuester D, Ullrich O, Mittag F, Habold C, Boltze C, Peters B, Krueger S, Hintze C, Meyer F, Hartig R, Roessner A
Department of Pathology, Otto-von-Guericke University Magdeburg, Germany.
J Pathol. 2006 May;209(1):95-105. doi: 10.1002/path.1951.
The death-associated protein kinase (DAP-kinase) is a cytoskeleton-associated protein crucially involved in the induction of early apoptotic pathways. Aberrant hypermethylation of the DAP-kinase promoter plays a major role in tumorigenesis. We aimed to investigate the inactivation of DAP-kinase and its association with apoptotic cell death in 94 colorectal carcinomas. DAP-kinase promoter hypermethylation and mRNA expression were investigated using methylation-specific PCR and real-time RT-PCR, respectively. The expression of DAP-kinase, Fas, and Fas-ligand (FasL) proteins was studied by immunohistochemistry and immunofluorescence. Apoptosis of tumour cells was investigated using the TUNEL assay. DAP-kinase was expressed in tumour cells and tumour-invading macrophages and was closely associated with high numbers of apoptotic tumour cells. DAP-kinase expression co-localized with FasL overexpression in tumour-associated macrophages, and aberrant promoter hypermethylation was verified in more than 50% of carcinomas. There was a tendency for proximal tumours to show DAP-kinase promoter methylation more frequently (p = 0.07). Promoter methylation resulted in a decrease or loss of DAP-kinase protein expression in tumour cells and tumour-associated macrophages. Simultaneously, a decreased apoptotic count and loss of Fas/FasL expression was observed in tumour cells. Our study is the first to demonstrate DAP-kinase expression in invading tumour-associated macrophages in colorectal cancer. The presence of similar expression levels of DAP-kinase in tumour cells and associated macrophages, and their dependence on the promoter methylation status of the tumour cells, suggests cross talk between these cell types during apoptotic cell death.
死亡相关蛋白激酶（DAP激酶）是一种与细胞骨架相关的蛋白，在早期凋亡途径的诱导中起关键作用。DAP激酶启动子的异常高甲基化在肿瘤发生中起主要作用。我们旨在研究94例结直肠癌中DAP激酶的失活及其与凋亡细胞死亡的关系。分别使用甲基化特异性PCR和实时RT-PCR研究DAP激酶启动子的高甲基化和mRNA表达。通过免疫组织化学和免疫荧光研究DAP激酶、Fas和Fas配体（FasL）蛋白的表达。使用TUNEL法研究肿瘤细胞的凋亡。DAP激酶在肿瘤细胞和肿瘤浸润巨噬细胞中表达，并与大量凋亡肿瘤细胞密切相关。DAP激酶表达与肿瘤相关巨噬细胞中FasL的过表达共定位，并且在超过50%的癌中证实了启动子异常高甲基化。近端肿瘤更频繁地显示DAP激酶启动子甲基化有一定趋势（p = 0.07）。启动子甲基化导致肿瘤细胞和肿瘤相关巨噬细胞中DAP激酶蛋白表达降低或缺失。同时，在肿瘤细胞中观察到凋亡计数减少和Fas/FasL表达缺失。我们的研究首次证明了DAP激酶在结直肠癌侵袭性肿瘤相关巨噬细胞中的表达。肿瘤细胞和相关巨噬细胞中DAP激酶表达水平相似，以及它们对肿瘤细胞启动子甲基化状态的依赖性，表明在凋亡细胞死亡过程中这些细胞类型之间存在相互作用。
