Prevention of Metastasis by Green Tea Polyphenols

描述（由申请人提供）：绿色茶多酚（GTP）及其主要成分表没食子儿茶素-3-没食子酸酯（表没食子儿茶素没食子酸酯）与降低前列腺癌进展风险相关，并成为一种有前途的转移抑制剂。我们发表的研究（Gupta等人，Proc.Natl. Acad. Sci. USA 98：10350-5，2001）已经表明，在人类中容易达到的剂量下，遗传上易患前列腺癌的转基因小鼠[TRAMP小鼠模型（小鼠前列腺的转基因腺癌）]口服绿色茶多酚，导致原发性肿瘤的显著抑制和完全防止向远端器官的转移。尽管如此，绿色茶多酚在阻断癌细胞转移过程中的作用机制仍在很大程度上未知。基于我们初步研究的结果，我们假设GTP/EGCG介导的金属蛋白酶组织抑制剂（TIMP）-3的再表达是GTP/EGCG抑制前列腺癌细胞侵袭从而防止肿瘤转移的关键机制。TIMP-3与基质金属蛋白酶（MMP-2和MMP-9）的催化结构域以1：1的化学计量比直接结合，MMP-2和MMP-9是参与基底膜溶解的关键酶。TIMP-3蛋白表达水平低与侵袭性肿瘤表型和无病生存率低相关。在提出的具体目标1下，我们将研究GTP/EGCG重新激活TIMP-3并抑制前列腺癌细胞侵袭的表观遗传机制。具体目标2将确定GTP/EGCG在再活化TIMP-3和预防转移中的体内作用。假设在临床前模型中，GTP/EGCG的体内补充可以通过组蛋白的整体修饰和TIMP-3启动子的特异性改变显著降低转移级联而有效地增加TIMP-3表达。我们计划在去势nu/nu小鼠中原位植入C4-2B肿瘤细胞，其在器官中形成原发性肿瘤并转移到骨并侵入局部组织，包括淋巴结和肝脏。这些研究将为深入了解GTP/EGCG在预防前列腺癌转移中的作用机制提供依据。

DESCRIPTION (provided by applicant): Green tea polyphenols (GTP) and its major constituent, epigallocatechin-3-gallate (EGCG) has been associated with reduced risk of prostate cancer progression and emerged as a promising suppressor of metastasis. Our published study (Gupta et al. Proc. Natl. Acad. Sci. USA 98:10350-5, 2001) has shown that oral consumption of green tea polyphenols by transgenic mice [the TRAMP mouse model (transgenic adenocarcinoma of the mouse prostate)] genetically predisposed to developing prostate cancer, at doses readily achievable in humans, results in significant inhibition of primary tumor and completely prevented metastases to distant-site organs. Nonetheless, the mechanism of action of green tea polyphenols in blocking the metastatic process in cancer cells remains largely unknown. Based on the results of our preliminary studies we hypothesize that GTP/EGCG-mediated re-expression of Tissue Inhibitor of Metalloproteinases (TIMP)-3 is a critical mechanism wherein GTP/EGCG inhibits invasion of prostate cancer cells thereby preventing tumor metastasis. TIMP-3 directly binds to the catalytic domain of matrix metalloproteinase (MMP-2 and -9) in 1:1 stoichiometry, which are key enzymes involved in the dissolution of basement membrane. Low level of TIMP-3 protein expression has been associated with an aggressive tumor phenotype and poor disease-free survival. Under the proposed specific aim 1 we will investigate the epigenetic mechanism(s) by which GTP/EGCG reactivates TIMP-3 and suppress invasiveness in prostate cancer cells. Specific aim 2 will determine the in vivo effects of GTP/EGCG in reactivating TIMP-3 and preventing metastasis. The hypothesis is that in vivo supplementation of GTP/EGCG could effectively increase TIMP-3 expression through global modification in histone proteins and specific alterations at the TIMP-3 promoter significantly reducing metastatic cascade in pre-clinical model. We plan to use an orthotopic implantation of C4-2B tumor cells in castrated nu/nu mice which forms primary tumor in the organ and metastasizes to the bone and invades local tissue including lymph nodes and liver. These studies will provide mechanistic basis of understanding the effect of GTP/EGCG in the prevention of prostate cancer metastasis.