Inbal B, Cohen O, Polak-Charcon S, Kopolovic J, Vadai E, Eisenbach L, Kimchi A
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
Nature. 1997 Nov 13;390(6656):180-4. doi: 10.1038/36599.
DAP kinase is a new type of calcium/calmodulin-dependent enzyme that phosphorylates serine/threonine residues on proteins. Its structure contains ankyrin repeats and the 'death' domain, and it is associated with the cell cytoskeleton. The gene encoding DAP kinase was initially isolated as a positive mediator of apoptosis induced by interferon-gamma, by using a strategy of functional cloning. We have now tested whether this gene has tumour-suppressive activity. We found that lung carcinoma clones, characterized by their highly aggressive metastatic behaviour and originating from two independent murine lung tumours, did not express DAP kinase, in contrast to their low-metastatic counterparts. Restoration of DAP kinase to physiological levels in high-metastatic Lewis carcinoma cells suppressed their ability to form lung metastases after intravenous injection into syngeneic mice, and delayed local tumour growth in a foreign 'microenvironment' Conversely, in vivo selection of rare lung lesions following injection into syngeneic mice of low-metastatic Lewis carcinoma cells or of DAP kinase transfectants, was associated with loss of DAP kinase expression. In situ TUNEL staining of tumour sections revealed that DAP kinase expression from the transgene raised the incidence of apoptosis in vivo. DAP-kinase transfectants also showed increased sensitivity in vitro to apoptotic stimuli, of the sort encountered by metastasizing cells at different stages of malignancy. We propose that loss of DAP kinase expression provides a unique mechanism that links suppression of apoptosis to metastasis.
DAP激酶是一种新型的钙/钙调蛋白依赖性酶，可使蛋白质上的丝氨酸/苏氨酸残基磷酸化。其结构包含锚蛋白重复序列和“死亡”结构域，并且与细胞细胞骨架相关。通过功能克隆策略，最初分离出编码DAP激酶的基因，作为干扰素-γ诱导的细胞凋亡的正向介质。我们现在测试了该基因是否具有肿瘤抑制活性。我们发现，与低转移性对应物相比，源自两个独立的小鼠肺肿瘤、具有高度侵袭性转移行为的肺癌克隆不表达DAP激酶。将DAP激酶恢复到高转移性Lewis癌细胞的生理水平，可抑制其静脉注射到同基因小鼠后形成肺转移的能力，并延迟在异体“微环境”中的局部肿瘤生长。相反，将低转移性Lewis癌细胞或DAP激酶转染子注射到同基因小鼠后，对罕见肺部病变进行体内选择，与DAP激酶表达缺失有关。肿瘤切片的原位TUNEL染色显示，转基因表达的DAP激酶提高了体内细胞凋亡的发生率。DAP激酶转染子在体外对凋亡刺激也表现出更高的敏感性，这种刺激是转移细胞在恶性肿瘤不同阶段所遇到的。我们提出，DAP激酶表达缺失提供了一种独特的机制，将细胞凋亡抑制与转移联系起来。
