Warmka Janel K, Winston Susanna E, Zeliadt Nicholette A, Wattenberg Elizabeth V
Division of Envirommental and Occupational Health, School of Public Health, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Toxicol Appl Pharmacol. 2002 Nov 15;185(1):8-17. doi: 10.1006/taap.2002.9519.
We have been probing the molecular mechanisms of tumor promoters that stimulate distinct initial signals to define critical downstream biochemical events in carcinogenesis. The action of the novel skin tumor promoter palytoxin on signaling and gene expression in keratinocytes, the primary target cells of tumor promoters, was therefore investigated. Palytoxin stimulated an increase in mRNA for matrix metalloproteinase-13 (MMP-13), an enzyme implicated in carcinogenesis, in a keratinocyte cell line derived from initiated mouse skin (308). Palytoxin stimulated an increase in c-Fos binding to the activator protein-1 (AP-1) site present in the promoter of the mouse MMP-13 gene. This effect was specific because palytoxin had little effect on c-Jun, JunB, JunD, FosB, Fra-1, or Fra-2 binding or on overall levels of transcription factor binding. The increase in c-Fos binding corresponded to a palytoxin-stimulated increase in c-Fos protein levels. Palytoxin stimulated the activation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase, and p38. The MAPK kinase inhibitor PD 98059 blocked palytoxin-stimulated ERK activation. PD 98059 also blocked the palytoxin-stimulated increases in c-Fos protein levels, c-Fos binding to the AP-1 site, and MMP-13 mRNA. These studies identify important differences between palytoxin-stimulated signaling in keratinocytes derived from initiated mouse skin, the biologically relevant cell type, and other cell lines. Specifically, our data suggest that, in keratinocytes derived from initiated mouse skin, ERK plays an important role in transmitting palytoxin-stimulated signals to three downstream targets that are likely to affect carcinogenesis: c-Fos, AP-1, and MMP-13.
我们一直在探究肿瘤启动子的分子机制，这些启动子会激发不同的初始信号，以确定致癌过程中关键的下游生化事件。因此，我们研究了新型皮肤肿瘤启动子岩沙海葵毒素对角质形成细胞（肿瘤启动子的主要靶细胞）信号传导和基因表达的作用。岩沙海葵毒素刺激了基质金属蛋白酶13（MMP - 13，一种与致癌作用有关的酶）在源自起始小鼠皮肤的角质形成细胞系（308）中的mRNA增加。岩沙海葵毒素刺激了c - Fos与小鼠MMP - 13基因启动子中存在的激活蛋白 - 1（AP - 1）位点的结合增加。这种效应具有特异性，因为岩沙海葵毒素对c - Jun、JunB、JunD、FosB、Fra - 1或Fra - 2的结合或转录因子结合的总体水平几乎没有影响。c - Fos结合的增加与岩沙海葵毒素刺激引起的c - Fos蛋白水平增加相对应。岩沙海葵毒素刺激了丝裂原活化蛋白激酶（MAPK）细胞外信号调节激酶（ERK）、c - Jun N端激酶和p38的激活。MAPK激酶抑制剂PD 98059阻断了岩沙海葵毒素刺激的ERK激活。PD 98059还阻断了岩沙海葵毒素刺激引起的c - Fos蛋白水平增加、c - Fos与AP - 1位点的结合以及MMP - 13 mRNA的增加。这些研究确定了岩沙海葵毒素在源自起始小鼠皮肤的角质形成细胞（生物学上相关的细胞类型）和其他细胞系中刺激信号传导之间的重要差异。具体而言，我们的数据表明，在源自起始小鼠皮肤的角质形成细胞中，ERK在将岩沙海葵毒素刺激的信号传递到三个可能影响致癌作用的下游靶点（c - Fos、AP - 1和MMP - 13）中起重要作用。
