Mechanisms underlying therapeutic effect of a new compound Isorhapontigenin (ISO)

描述（由申请人提供）：膀胱尿路上皮癌（或膀胱癌，BC）是西方世界最常见的癌症之一。由于高级别浸润性膀胱癌（HGIBC）可以发展为危及生命的转移，因此鉴定一种特异性抑制BC侵袭和转移的天然化合物对于潜在地降低这种疾病的死亡率具有巨大的重要性。异橙皮素（isohapontigenin， ISO）是一种新的苯乙烯衍生物，从一种中药中分离出来，在中国用于治疗bc已有数百年的历史，但其分子机制尚不清楚。因此，本研究的目的是确定ISO的潜在治疗作用及其抗癌活性的分子机制。我们的初步研究发现，X-linked inhibitor of the apoptosis protein （XIAP）在所有被检测的人类浸润性BC组织中都有极高的表达，但在所有邻近的正常膀胱组织中几乎检测不到，并且与野生型小鼠和Ras诱导的低级别BC相比，p53-/-/pRb-/-小鼠bbn诱导的浸润性BC组织中XIAP的表达水平也显著升高。我们还发现，在培养的HGIBC来源的人BC细胞中，XIAP明显高于来自低级别乳头状膀胱肿瘤（LGPBT）的人BC细胞。此外，我们发现用ISO处理BC细胞抑制HGIBC T24T细胞的迁移和侵袭，在转录水平上特异性抑制Sp-1反激活和XIAP下调，而在5-10¿M剂量下不影响细胞增殖。因此，我们假设ISO是一种有效的治疗药物，可以通过下调Sp-1/XIAP通路抑制BC在体外的侵袭和体内的侵袭转移。我们将通过以下目的进行验证：1 .验证isoxiap下调是其抑制bbn诱导的p53和pRb缺失小鼠BC形成的原因；2：评估SP-1是体外和体内BC中XIAP的ISO下调的主要靶点的假设；3：明确ISO在体外和体内抑制BC发展的分子机制。该建议的成功将促进我们对ISO化合物抗癌作用的分子机制的理解。这一新发现将为设计更有效的利用ISO的策略或合成其他新的构象限制衍生物以治疗bc和其他癌症提供有价值的信息。考虑到BC是最常见的恶性肿瘤，每年在全球范围内造成336,000例新病例和132,000例死亡，这些研究应该反过来有助于改善BC患者的临床结果。

DESCRIPTION (provided by applicant): Urothelial carcinoma of the bladder (or bladder cancer, BC) is one of the most common cancers in the Western world. Because high-grade invasive bladder cancers (HGIBC) can progress to life threatening metastases, identifying a natural compound that specifically inhibits BC invasion and metastasis is of tremendous importance for potentially reducing mortality as a result of this disease. Isorhapontigenin (ISO) i a new derivative of stilbene, and isolated from a Chinese herb that has been used in China for treatment of BCs for hundreds of years without understanding of molecular mechanisms. Thus, the goal of this proposal is to determine the ISO potential therapeutic effect and the molecular mechanisms responsible for this anti-cancer activity. Our preliminary studies found that the X-linked inhibitor of the apoptosis protein (XIAP) was extremely highly expressed in all of the human invasive BC tissues that were tested, but it was barely detectable in all adjacent normal bladder tissues, and that XIAP expression level was also markedly elevated in BBN-induced invasive BC tissues in p53-/-/pRb-/- mice as compared with that from wild-type mice and oncogenic Ras- induced low-grade BCs. We also found that XIAP was significantly higher in cultured human BC cells derived from HGIBC than from those derived from low-grade papillary bladder tumors (LGPBT). Moreover, we showed that treatment of BC cells with ISO inhibited HGIBC T24T cell migration and invasion, was accompanied with specific inhibition of Sp-1 transactivation and XIAP downregulation at the transcription level without affecting cell proliferation at doses of 5-10 ¿M. Thus, we hypothesize that ISO is an effective therapeutic agent for the inhibition of BC invasion in vitro and BC invasion and metastasis in vivo via downregulation of the Sp-1/XIAP pathway. We will test this with the following aims: 1: To test the hypothesis that XIAP downregulation by ISO is responsible for its inhibition of BBN-induced BC formation in the mice lacking both p53 and pRb; 2: To evaluate the hypothesis that SP-1 is a major target for ISO downregulation of XIAP in BC in vitro and in vivo; 3: To define the molecular mechanisms whereby ISO inhibits the BC development in vitro and in vivo. Success of the proposal will facilitate our understanding of the molecular mechanism(s) responsible for the anti-cancer effects of ISO compound. This novel finding will provide valuable information for the design of more effective strategies for utilization of ISO or for the synthesis of other novel conformation- constrained derivatives for the treatment of BCs and other cancers. Taken together with the fact that BC is the most common malignant tumors, responsible for 336,000 new cases and 132,000 deaths annually worldwide, the studies should in turn help improve the clinical outcome of patients with BCs.