Introduction of full-length APC modulates cyclooxygenase-2 expression in HT-29 human colorectal carcinoma cells at the translational level
Introduction of full-length APC modulates cyclooxygenase-2 expression in HT-29 human colorectal carcinoma cells at the translational level
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DOI：
10.1093/carcin/20.11.2045
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发表时间：
1999-11-01
期刊：
影响因子：
4.7
通讯作者：
Eling, TE
中科院分区：
文献类型：
--
作者：
Hsi, LC;Angerman-Stewart, J;Eling, TE
腺瘤性息肉病大肠杆菌 (APC) 基因的突变与结直肠肿瘤发生的最早阶段相关，并且似乎是遗传性家族性腺瘤性息肉病 (FAP) 的原因。有证据表明，环氧合酶-2 (COX-2) 在人类结直肠癌和小鼠 FAP 模型的息肉中被诱导且水平升高。我们使用了 HT-29 细胞，一种具有突变羧基截短的 APC 基因的人结直肠癌细胞系，其中在诱导型启动子的控制下引入了完整的 APC 基因，这些 HT-29-APC 细胞提供了合适的模型系统来检查 COX-2 表达在 APC 功能丧失后如何失调，全长 APC 的诱导导致 HT-29-APC 细胞发生凋亡，然而，分化（通过碱性测量）全长 APC 的表达不会诱导磷酸酶活性，全长 APC 蛋白已被证明可结合细胞内蛋白 β-catenin，因此 Lef/Tcf 转录因子下调。APC 免疫沉淀物分析表明 β-catenin 与全长 APC 相互作用的时间依赖性增加，因此，此时这些细胞中的 Lef/Tcf 信号通路是完整的。此外，全长APC表达后，COX-2蛋白表达下调，而COX-2 mRNA水平保持不变。这些数据表明APC直接或间接地在COX-2的翻译调节中发挥作用。用凋亡诱导剂丁酸钠处理HT-29-APC细胞不会改变COX-2蛋白表达。因此，COX-2 下调似乎是 APC 特异性的，而不仅仅是由于细胞凋亡诱导。 APC 似乎独特地调节 COX-2 表达。 HT-29-APC 细胞中 COX-2 蛋白表达下调的机制正在研究中。
Mutation of the adenomatous polyposis coli (APC) gene is associated with the earliest stages of colorectal tumorigenesis and appears to be responsible for the hereditary condition familial adenomatous polyposis (FAP), Evidence indicates that cyclooxygenase-2 (COX-2) is induced and at elevated levels in human colorectal cancers and in the polyps of mouse FAP models. We have used HT-29 cells, a human colorectal carcinoma cell line with a mutant carboxy-truncated APC gene, in which intact APC gene has been introduced under the control of an inducible promoter, These HT-29-APC cells provide a suitable model system to examine how COX-2 expression becomes dysregulated after loss of APC function, Induction of full-length APC causes the HT-29-APC cells to undergo apoptosis, However, differentiation, as measured by alkaline phosphatase activity, is not induced upon expression of full-length APC, Full-length APC protein has been shown to bind the intracellular protein beta-catenin and, as a result, the Lef/Tcf transcription factors are down-regulated, Analysis of APC immunoprecipitates demonstrate a time-dependent increase of beta-catenin interacting with full-length APC, Thus, the Lef/Tcf signaling pathway is intact at this point in these cells. Furthermore, upon expression of full-length APC, COX-2 protein expression is down-regulated while COX-2 mRNA levels remain the same. These data indicate that APC plays a role, either directly or indirectly, in the translational regulation of COX-2, Treatment of the HT-29-APC cells with sodium butyrate, an inducer of apoptosis, does not alter COX-2 protein expression. Thus, COX-2 down-regulation appears to be APC specific and not just due to apoptotic induction. APC appears to uniquely regulate COX-2 expression. The mechanism by which COX-2 protein expression is down-regulated in the HT-29-APC cells is under investigation.