Development of a Silibinin/Vitamin D Regimen for Colon Cancer Prevention

描述(由申请人提供)：流行病学和动物研究已经证实，天然饮食成分和补充剂可以降低癌症风险。结直肠癌(CRC)是美国第二大常见的恶性肿瘤死亡原因，死亡率约为50%。与结肠长期炎症相关的疾病，如慢性溃疡性结肠炎(UC)和克罗恩病(CD)，会增加患CRC的风险。慢性炎症性疾病患者降低这种风险的选择有限。饮食成分可以用于化学预防，特别是因为大多数成分在高剂量下都是耐受的，没有严重的副作用。血清1，25-二羟基维生素D(1，25D)水平与结直肠癌发病率呈负相关。1，25D通过与维生素D受体(VDR)结合发挥作用。在慢性炎症条件下，细胞因子释放增加转录因子Snail1和Snail2/slug的表达，导致VDR水平受到抑制，无法对1，25D做出反应。从水飞蓟种子中分离出的黄酮木脂素水飞蓟宾能抑制蜗牛1和鼻涕的水平。我们认为，在慢性炎症中，Snail1/Slug介导的VDR水平下降，导致对1，25D无效，可以通过与水飞蓟宾共同治疗而逆转，恢复1，25D的有益效果，并导致良好的预后。在支持方面，我们发现，在HT-29人结肠细胞中，肿瘤坏死因子(肿瘤坏死因子)增加Snail1和Slug水平，降低VDR水平，并抑制1，25D的抗增殖作用。水飞蓟宾降低Snail1和Slug水平，增加VDR水平，逆转肿瘤坏死因子对Snail1、Slug和VDR以及对细胞增殖的影响，并在1，25D无反应的细胞中恢复维生素D反应元件介导的启动子活性。水飞蓟宾和1，25D协同抑制肿瘤坏死因子诱导的细胞增殖。我们的长期目标是确定水飞蓟宾和1，25D 类似物具有协同作用，可作为化学预防药物，防止慢性炎症条件下结直肠癌的发展。我们将通过追求这些具体目标来检验我们的假设。1)1，25D信号在水飞蓟宾介导的对炎性细胞因子介导的结肠细胞损伤的保护作用中的作用将以细胞增殖、迁移和侵袭为读数来评估；2)水飞蓟宾+EB1089(非高钙1，25D类似物)方案在AOM/DSS(偶氮甲烷/葡聚糖硫酸钠)小鼠模型中对炎症和肿瘤形成的影响将被评估。这些研究将为未来旨在开发1，25D类似物+水飞蓟宾方案以预防慢性炎症患者结直肠癌的机械性和转化性研究奠定基础。

DESCRIPTION (provided by applicant): Epidemiologic and animal studies have established that natural dietary components and supplements reduce cancer risk. Colorectal carcinoma (CRC) is the second most common cause of death from malignant disease in the US; the mortality rate is ~50%. Diseases associated with long-term inflammation of the colon, such as chronic ulcerative colitis (UC) and Crohn's disease (CD), increase the risk for CRC. Patients with chronic inflammatory disease have limited options to reduce this risk. Dietary constituents can be developed for chemoprevention, especially since most are tolerated at high doses without serious side-effects. An inverse correlation exists between serum levels of 1, 25-dihydroxyvitamin D (1,25D) and CRC incidence. 1,25D functions by binding to the vitamin D receptor (VDR). In conditions of chronic inflammation, cytokine release increases expression of the transcription factors Snail1 and Snail2/Slug, leading to suppressed VDR levels and failure to respond to 1,25D. The flavonolignan silibinin, isolated from milk thistle seeds, suppresses Snail1 and Slug levels. We propose that Snail1/Slug-mediated decrease in VDR levels in chronic inflammation, accounting for failure to respond to 1,25D, can be reversed by co-treating with silibinin, restoring the beneficial effects of 1,25D and leading to a favorable prognosis. In support, we show that, in HT-29 human colon cells, tumor necrosis factor-¿ (TNF-¿) increases Snail1 and Slug levels, decreases VDR levels, and suppress 1,25D's anti-proliferative effects. Silibinin decreases Snail1 and Slug levels, increases VDR levels, reverses the TNF-¿ effects on Snail1, Slug and VDR and on cell proliferation, and restores Vitamin D Response Element-mediated promoter activity in 1,25D-unresponsive cells. Silibinin and 1,25D synergistically inhibit TNF-¿-induced cell proliferation. Our long-term goal is to determine if silibinin and 1,25D analogs function synergistically as chemopreventive agents to prevent CRC development in conditions of chronic inflammation. We will test our hypothesis by pursuing these Specific Aims. 1) The role of 1,25D signaling in the silibinin-mediated protective effects against inflammatory cytokine-mediated colon cell damage will be assessed using cell proliferation, migration and invasion as readouts; and 2) the effect of a silibinin + EB1089 (non-hypercalcemic 1,25D analog) regimen on inflammation and tumorigenesis will be evaluated in the AOM/DSS (azoxymethane/dextran sodium sulfate) mouse model. These studies will lay the foundation for future mechanistic and translational studies aimed at developing a 1,25D analogs + silibinin regimen to prevent CRC in patients with chronic inflammation.