Aggarwal S, Taneja N, Lin L, Orringer M B, Rehemtulla A, Beer D G
Department of Surgery, University of Michigan Medical School, Ann Arbor 48109, USA.
Neoplasia. 2000 Jul-Aug;2(4):346-56. doi: 10.1038/sj.neo.7900097.
The prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been shown to exert a chemopreventive effect in esophageal and other gastrointestinal tumors. The precise mechanism by which this occurs, however, is unknown. While the inhibition of COX-2 as a potential explanation for this chemopreventive effect has gained a great deal of support, there also exists evidence supporting the presence of cyclooxygenase-independent pathways through which NSAIDs may exert their effects. In this study, immunohistochemical analysis of 29 Barrett's epithelial samples and 60 esophageal adenocarcinomas demonstrated abundant expression of the COX-2 protein in Barrett's epithelium, but marked heterogeneity of expression in esophageal adenocarcinomas. The three esophageal adenocarcinoma cell lines, Flo-1, Bic-1, and Seg-1, also demonstrated varying expression patterns for COX-1 and COX-2. Indomethacin induced apoptosis in all three cell lines, however, in both a time- and dose-dependent manner. In Flo-1 cells, which expressed almost undetectable levels of COX-1 and COX-2, and in Seg-1, which expressed significant levels of COX-1 and COX-2, indomethacin caused upregulation of the pro-apoptotic protein Bax. The upregulation of Bax was accompanied by the translocation of mitochondrial cytochrome c to the cytoplasm, and activation of caspase 9. Pre-treatment of both cell lines with the specific caspase 9 inhibitor, z-LEHD-FMK, as well as the broad-spectrum caspase inhibitor, z-VAD-FMK, blocked the effect of indomethacin-induced apoptosis. These data demonstrate that induction of apoptosis by indomethacin in esophageal adenocarcinoma cells is associated with the upregulation of Bax expression and mitochondrial cytochrome c translocation, and does not correlate with the expression of COX-2. This may have important implications for identifying new therapeutic targets in this deadly disease.
长期使用非甾体抗炎药（NSAIDs）已被证明对食管癌和其他胃肠道肿瘤具有化学预防作用。然而，这种作用发生的确切机制尚不清楚。虽然抑制COX-2作为这种化学预防作用的一种潜在解释已获得大量支持，但也有证据支持存在非COX-2依赖性途径，NSAIDs可能通过这些途径发挥作用。在本研究中，对29个巴雷特上皮样本和60例食管腺癌进行免疫组织化学分析，结果显示COX-2蛋白在巴雷特上皮中大量表达，但在食管腺癌中表达存在明显异质性。三种食管腺癌细胞系Flo-1、Bic-1和Seg-1也表现出COX-1和COX-2的不同表达模式。然而，吲哚美辛以时间和剂量依赖性方式诱导这三种细胞系凋亡。在几乎检测不到COX-1和COX-2表达的Flo-1细胞以及表达显著水平COX-1和COX-2的Seg-1细胞中，吲哚美辛导致促凋亡蛋白Bax上调。Bax的上调伴随着线粒体细胞色素c向细胞质的转位以及caspase 9的激活。用特异性caspase 9抑制剂z-LEHD-FMK以及广谱caspase抑制剂z-VAD-FMK对这两种细胞系进行预处理，均阻断了吲哚美辛诱导凋亡的作用。这些数据表明，吲哚美辛诱导食管腺癌细胞凋亡与Bax表达上调和线粒体细胞色素c转位有关，与COX-2的表达无关。这可能对确定这种致命疾病的新治疗靶点具有重要意义。
