Lim Kyu, Han Chang, Xu Lihong, Isse Kumiko, Demetris Anthony J, Wu Tong
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA.
Cancer Res. 2008 Jan 15;68(2):553-60. doi: 10.1158/0008-5472.CAN-07-2295.
Cholangiocarcinoma is a highly malignant neoplasm of the biliary tree. It has a high rate of mortality, and currently, there is no effective chemoprevention and treatment. This study was designed to investigate the potential effect of omega 3 polyunsaturated fatty acids (omega 3-PUFA) on human cholangiocarcinoma cell growth and to determine their mechanisms of actions. Treatment of three human cholangiocarcinoma cells (CCLP1, HuCCT1, SG231) with two omega 3-PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for 12 to 72 h resulted in a dose- and time-dependent inhibition of cell growth; in contrast, arachidonic acid, a omega 6-PUFA, had no significant effect. The omega 3-PUFA effect is due to the induction of apoptosis, given that DHA induced the cleaved form of PARP, caspase-3, and caspase-9. DHA and EPA treatment caused dephosphorylation (and hence, the activation) of glycogen synthase kinase-3beta (GSK-3beta) with a decline of beta-catenin protein. Accordingly, DHA treatment also decreased the beta-catenin-mediated T cell factor/lymphoid enhancer factor (TCF/LEF) reporter activity, and inhibited the expression of c-Met, a beta-catenin-controlled downstream gene implicated in cholangiocarcinogenesis. The GSK-3beta inhibitor, SB216763, partially prevented DHA-induced reduction of beta-catenin protein and TCF/LEF reporter activity, and restored cell growth, suggesting the involvement of GSK-3beta dephosphorylation in omega 3-PUFA-induced beta-catenin degradation. In parallel, DHA treatment also induced the formation of the beta-catenin/Axin/GSK-3beta binding complex, further leading to beta-catenin degradation. Moreover, DHA inhibited the expression of cyclooxygenase-2 (COX-2) and enhanced the expression of 15-hydroxyprostaglandin dehydrogenase, a physiologic COX-2 antagonist, in human cholangiocarcinoma cells. These findings suggest that omega 3-PUFAs block cholangiocarcinoma cell growth at least in part through inhibition of Wnt/beta-catenin and COX-2 signaling pathways. Thus, utilization of omega 3-PUFAs may represent an effective and safe therapeutic approach for the chemoprevention and treatment of human cholangiocarcinoma.
胆管癌是一种胆管的高恶性肿瘤。其死亡率很高，目前尚无有效的化学预防和治疗方法。本研究旨在探讨ω-3多不饱和脂肪酸（ω-3-PUFA）对人胆管癌细胞生长的潜在影响，并确定其作用机制。用两种ω-3-PUFA，即二十二碳六烯酸（DHA）和二十碳五烯酸（EPA）处理三种人胆管癌细胞（CCLP1、HuCCT1、SG231）12至72小时，导致细胞生长呈剂量和时间依赖性抑制；相比之下，ω-6-PUFA花生四烯酸没有显著影响。鉴于DHA诱导了PARP、caspase-3和caspase-9的裂解形式，ω-3-PUFA的作用是由于诱导了细胞凋亡。DHA和EPA处理导致糖原合酶激酶-3β（GSK-3β）去磷酸化（从而激活），β-连环蛋白水平下降。因此，DHA处理还降低了β-连环蛋白介导的T细胞因子/淋巴细胞增强因子（TCF/LEF）报告基因活性，并抑制了c-Met的表达，c-Met是β-连环蛋白控制的下游基因，与胆管癌发生有关。GSK-3β抑制剂SB216763部分阻止了DHA诱导的β-连环蛋白水平降低和TCF/LEF报告基因活性，并恢复了细胞生长，表明GSK-3β去磷酸化参与了ω-3-PUFA诱导的β-连环蛋白降解。同时，DHA处理还诱导了β-连环蛋白/Axin/GSK-3β结合复合物的形成，进一步导致β-连环蛋白降解。此外，DHA抑制了人胆管癌细胞中环氧合酶-2（COX-2）的表达，并增强了15-羟基前列腺素脱氢酶（一种生理性COX-2拮抗剂）的表达。这些发现表明，ω-3-PUFA至少部分通过抑制Wnt/β-连环蛋白和COX-2信号通路来阻断胆管癌细胞生长。因此，利用ω-3-PUFA可能是一种有效且安全的化学预防和治疗人胆管癌的治疗方法。
