ROLE OF LIPIDS IN COLON CANCER

脂质在结肠癌中的作用

• 批准号: 6290019
• 负责人: Thomas Eling
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6290019
• 关键词: arachidonate; butyrates; carcinogenesis; colon neoplasms; enzyme activity; enzyme inhibitors; linoleate; lipid metabolism; lipoxygenase; neoplasm /cancer pharmacology; nonsteroidal antiinflammatory agent; phospholipase A2; prostaglandin endoperoxide synthase; tissue /cell culture

The importance of arachidonic acid and linoleic acid metabolism is supported by animal and human epidemiology studies that indicate that aspirin and other NSAIDs reduce the incidence and mortality of colon cancer. Recent studies reported that Cox-2 is significantly expressed in colon cancer and other cancers. Some data suggest effects of prostaglandins are via modulation of apoptosis and angiogenesis. We are examining arachidonic and linoleic acid metabolism, and the expression of Cox-1 and -2, lipoxygenases, human cell lines. Using CaCo-2 cells as a model for human colorectal epithelium, we have studied the expression of Cox-2, -1 and 15-LO during apoptosis and differentiation. Apoptosis and differentiation is accompanied by a decrease in the expression of Cox-2 and an increase in expression of 15-LO. The expression of Cox-1, Cox-2 and 15-lipoxygenase was measured in human colorectal tumors and the adjacent normal tissue obtained from UNC. Cox-1 is highly expressed in both the normal and tumor tissue while higher expression of Cox-2 was detected in most of the tumors compared to normal tissue.15- lipoxygenase was expressed in most colorectal tissue and characterized as 15-LO-1, with a 2-3 fold higher expression noted in tumors. Immunohistochemical studies found the 15-lipoxygenase-1 to be highly expressed in the epithelial cells. The regulation of 15-lipoxygenase and Cox-2 expression is also under investigation. We have used HT-29 cells, a human colorectal carcinoma cell line with 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 dis- regulated after loss of APC function. Induction of full-length APC causes the HT-29-APC cells to undergo apoptosis. Full-length APC protein has been shown to bind the intracellular protein b-catenin and as a result, the Lef/Tcf transcription factors are downregulated. Analysis of APC immunoprecipitates demonstrates a time dependent increase of b-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 downregulated while Cox-2 mRNA levels remain the same. This data indicates 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 downregulation 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 downregulated in the HT-29-APC cells is under investigation.We investigated the transcriptional regulation of 15-LO in human colorectal carcinoma cells by treatment with NaBT and other histone deacetylase (HDAC) inhibitors. The treatment with NaBT, trichostatin A and HC toxin induced the clear expression of 15-LO--1 in Caco-2 and SW-480 cells. Acid urea polyacrylamide gel electrophoresis indicated that histone proteins from Caco-2 and SW-480 cells were acetylated by treatment with HDAC inhibitors. Moreover, histone acetylation was detected in the surgical samples of human colon cancer expressing 15-lipoxygenase. These observations suggested that histone acetylation by HDAC inhibitors such as butyrate may, directly or indirectly, modulate the transcriptional regulation of 15-lipoxygenase in human colorectal carcinoma cells and colorectal tissue. We are currently investigating if the family of GATA transcriptions factor know to be involved in differentiation are also directly responsible for the increased expression of 15-lipoxygenase. - apoptosis, colon cancer, C0X-2, 15-LO, cell differentiation

花生四烯酸和亚油酸代谢的重要性得到动物和人类流行病学研究的支持，这些研究表明阿司匹林和其他NSAID可降低结肠癌的发病率和死亡率。最近的研究报道，考克斯-2在结肠癌和其他癌症中显著表达。一些数据表明，洋地黄素的作用是通过调节细胞凋亡和血管生成。我们正在研究花生四烯酸和亚油酸代谢，以及考克斯-1和-2，脂氧合酶，人类细胞系的表达。以CaCo-2细胞为模型，研究了考克斯-2、-1和15-LO在人大肠癌细胞凋亡和分化过程中的表达。细胞凋亡和分化伴随着考克斯-2表达的减少和15-LO表达的增加。检测考克斯-1、考克斯-2和15-脂氧合酶在人结直肠癌和癌旁正常组织中的表达。考克斯-1在正常组织和肿瘤组织中均高度表达，而与正常组织相比，在大多数肿瘤中检测到考克斯-2的更高表达。15-脂氧合酶在大多数结直肠组织中表达，并表征为15-LO-1，在肿瘤中的表达高2-3倍。免疫组织化学研究发现，15-脂氧合酶-1在上皮细胞中高度表达。15-脂氧合酶和考克斯-2表达的调节也在研究中。我们已经使用HT-29细胞，一种具有突变的羧基截短的APC基因的人结肠直肠癌细胞系，其中完整的APC基因已经在诱导型启动子的控制下被引入。这些HT-29-APC细胞提供了一种合适的模型系统来检测APC功能丧失后考克斯-2表达如何失调.全长APC的诱导导致HT-29-APC细胞经历凋亡。已显示全长APC蛋白结合细胞内蛋白b-连环蛋白，并且因此，Lef/Tcf转录因子下调。APC免疫沉淀物的分析表明与全长APC相互作用的b-连环蛋白的时间依赖性增加。因此，Lef/Tcf信号通路在这些细胞中的这一点上是完整的。此外，在表达全长APC时，考克斯-2蛋白表达下调，而考克斯-2 mRNA水平保持不变。该数据表明APC直接或间接地在考克斯-2的翻译调节中起作用。用丁酸钠（一种凋亡诱导剂）处理HT-29-APC细胞不改变考克斯-2蛋白表达。因此，考克斯-2下调似乎是APC特异性的，而不仅仅是由于凋亡诱导。APC似乎唯一地调节考克斯-2表达。本研究通过观察NaBT和其他组蛋白去乙酰化酶（HDAC）抑制剂对HT-29-APC细胞中15-LO的转录调控，探讨了HT-29-APC细胞中考克斯-2蛋白表达下调的机制。用NaBT、阿司他丁A和HC毒素处理Caco-2和SW-480细胞可诱导15-LO-1的明确表达。酸性尿素聚丙烯酰胺凝胶电泳结果表明，HDAC抑制剂处理后，Caco-2和SW-480细胞的组蛋白发生乙酰化。此外，在表达15-脂氧合酶的人结肠癌手术样品中检测到组蛋白乙酰化。这些观察结果表明，组蛋白乙酰化的HDAC抑制剂，如丁酸盐，可能直接或间接地调节15-脂氧合酶在人结直肠癌细胞和结直肠组织中的转录调控。我们目前正在研究已知参与分化的加塔转录因子家族是否也直接负责15-脂氧合酶表达的增加。- 凋亡，结肠癌，C 0X-2，15-LO，细胞分化