Masuda Katsuaki, Ono Mayumi, Okamoto Masahiro, Morikawa Wataru, Otsubo Michihiro, Migita Toshiro, Tsuneyoshi Masazumi, Okuda Heiwa, Shuin Taro, Naito Seiji, Kuwano Michihiko
Department of Medical Biochemistry, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Int J Cancer. 2003 Jul 20;105(6):803-10. doi: 10.1002/ijc.11152.
We previously identified 9 genes (i.e., thymosin beta4, secreted protein acidic and rich in cysteine, Cap43, ceruloplasmin, serum amyloid A, heat shock protein 90, LOT1, osteopontin and casein kinase Igamma) that are more highly expressed in cancerous regions than in noncancerous regions in human renal cancers. In our study, we considered the possibility that the von Hippel-Lindau (VHL) tumor suppressor gene might be able to affect the expression of these 9 genes in renal cancer cells. We first established 2 VHL-positive cell lines, 786/VHL-1 and 786/VHL-2, after the introduction of wild-type VHL into VHL-negative renal cancer 786-O cells. Of these 9 genes, expression of the Cap43 gene was specifically downregulated by VHL. Expression of Cap43 was also much lower in 4 other VHL-positive renal cancer cell lines than in VHL-negative 786-O cells. Cap43 promoter assays with several deletion or mutation constructs demonstrated that the Sp1 site in the element from -286 base pairs (bp) to -62 bp was partly responsible for VHL-induced suppression of the Cap43 gene. Immunostaining analysis with human specimens of renal cancers demonstrated that the Cap43 protein was expressed in most cancer cells and macrophages. We also observed a marked and specific increase of Cap43 mRNA levels in response to hypoxia or nickel in all VHL-positive cell lines. Cellular expression of Cap43 mRNA in response to hypoxia or nickel thus is closely associated with VHL gene expression in renal cancer cells. Although the function of the Cap43 protein remains unclear, the expression of Cap43 protein could be a molecular marker closely associated with VHL in renal cancer.
我们之前鉴定出9个基因（即胸腺素β4、富含半胱氨酸的酸性分泌蛋白、Cap43、铜蓝蛋白、血清淀粉样蛋白A、热休克蛋白90、LOT1、骨桥蛋白和酪蛋白激酶Iγ），这些基因在人类肾癌的癌组织区域比非癌组织区域表达更高。在我们的研究中，我们考虑了冯·希佩尔-林道（VHL）肿瘤抑制基因可能会影响这9个基因在肾癌细胞中表达的可能性。我们首先将野生型VHL导入VHL阴性的肾癌细胞786-O中，建立了2个VHL阳性细胞系，786/VHL-1和786/VHL-2。在这9个基因中，Cap43基因的表达被VHL特异性下调。在其他4个VHL阳性肾癌细胞系中，Cap43的表达也比VHL阴性的786-O细胞低得多。对几种缺失或突变构建体进行的Cap43启动子分析表明，从-286碱基对（bp）到-62 bp元件中的Sp1位点部分负责VHL诱导的Cap43基因抑制。对人类肾癌标本进行的免疫染色分析表明，Cap43蛋白在大多数癌细胞和巨噬细胞中表达。我们还观察到，在所有VHL阳性细胞系中，低氧或镍刺激后Cap43 mRNA水平显著且特异性升高。因此，肾癌细胞中Cap43 mRNA对低氧或镍刺激的细胞表达与VHL基因表达密切相关。尽管Cap43蛋白的功能尚不清楚，但Cap43蛋白的表达可能是与肾癌中VHL密切相关的分子标志物。
