Molecular Mechanisms of Prostate Cancer Chemoprevention by Apigenin

描述（由申请人提供）：本竞争性续期申请旨在继续资助研究芹菜素对前列腺癌抗癌作用的分子机制。在之前的资助期内，我们研究了芹菜素对细胞培养、肿瘤异种移植和转基因前列腺癌小鼠模型中各种蛋白激酶、IGF-I生长轴、¿- catenin和NF- B信号通路的影响。我们发现芹菜素抑制多种信号转导途径；因此，芹菜素作用的潜在靶点包括磷脂酰肌醇3-激酶（PI3K）、蛋白激酶B/Akt、经典MAPK/ERK1/2和周期蛋白依赖激酶。芹菜素有效抑制这些靶点的剂量范围与抑制信号传导和前列腺肿瘤发生的剂量范围相似，并且在人类生理上是可以达到的。在这项更新应用中，我们假设I(B激酶：IKKa/¿在介导芹菜素在多种信号转导途径中的抗癌作用中起中心枢纽作用。我们的假设是基于我们之前发表的研究结果和我们的初步数据，这些数据表明i) IKK活性在人类前列腺癌及其假定的前体中上调ii)芹菜素抑制IKK活性及其磷酸化，iii)芹菜素抑制多种信号转导途径，特别是IGF-I轴，PI3K-Akt, NF-(B)和¿- catenin途径，iv) IKK复合物对所有这些不同的信号转导途径都有调节作用。为了验证这一假设，我们将使用最先进的技术，包括1H NMR， x射线晶体学和先进的分子生物学程序，我们的研究将在敲入和敲除细胞培养以及转基因（TRAMP）小鼠上进行。我们提出的具体目标包括研究i) IKKa/¿在细胞转化和芹菜素抑制活性中的作用，ii) IKKa对巨噬蛋白抑制及其由芹菜素调节的作用，iii) IKK¿对叉头盒O3a活性和细胞分布的作用以及芹菜素对其的调节作用，以及iv) IKKa/¿作为芹菜素对TRAMP小鼠体内抗癌作用的分子靶点。我们期望了解芹菜素抗癌作用的分子机制，可能有助于开发基于这些关键分子机制的有效化学预防/治疗策略，更有效地靶向这些关键分子机制，减少相关副作用。

DESCRIPTION (provided by applicant): This competitive renewal application is for continued funding to investigate the molecular mechanisms underlying the anticancer effects of apigenin on prostate cancer. During the previous funding period, we investigated the effects of apigenin on various protein kinases, the IGF-I growth axis, ¿-Catenin and NF-(B signaling pathways in cell cultures, tumor xenografts and a genetically-modified mouse model of prostate cancer. We found that apigenin inhibits multiple signal transduction pathways; consequently, potential targets of apigenin action include phosphatidylinositol 3-kinase (PI3K), protein kinase B/Akt, classical MAPK/ERK1/2, and cyclin-dependent kinases. The dose range of apigenin that effectively inhibits these targets is similar to that which suppresses signaling and prostate tumorigenesis and is physiologically attainable in humans. In this renewal application, we hypothesize that I(B kinase: IKKa/¿ acts as a central hub in mediating the anticancer effects of apigenin on multiple signal transduction pathways. Our hypothesis is based upon our previously published findings and our preliminary data showing that i) IKK activity is upregulated in human prostate cancer and its putative precursor ii) apigenin inhibits IKK activity and its phosphorylation, iii) apigenin inhibits multiple signal transduction pathways, specifically, the IGF-I axis, PI3K-Akt, NF-(B and ¿-Catenin pathways, and iv) the IKK complex exhibits regulatory effects on all of these distinct signaling pathways. To test this hypothesis, we will use state-of-the-art techniques, including 1H NMR, X-ray crystallography, and advanced molecular biology procedures, and our studies will be performed on knock-in and knockout cell cultures and on transgenic (TRAMP) mice. Our proposed specific aims include investigation of i) the role of IKKa/¿ in cell transformation and the inhibitory activity of apigenin, ii) the role of IKKa on maspin suppression and its modulation by apigenin, iii) the role of IKK¿ on activity and cellular distribution of forkhead box O3a and its modulation by apigenin, and iv) IKKa/¿ as a molecular target for the anticancer effects of apigenin in vivo on TRAMP mice. We expect that understanding the molecular mechanisms underlying the anti-cancerous effects of apigenin may be helpful in developing effective chemopreventive/therapeutic strategies based upon targeting these key molecular mechanisms more effectively and with fewer associated side-effects. PUBLIC HEALTH RELEVANCE: Numerous studies have shown that apigenin (4', 5, 7-trihydroxyflavone), a naturally occurring plant flavone abundantly present in common fruits and vegetables, possess promising cancer preventive and therapeutic properties. It has low toxicity, is non-mutagenic, and has shown selective effects in inhibiting cell growth and inducing apoptosis in cancer cells without affecting normal cells. The molecular targets and molecular mechanisms are not fully investigated. We have previously demonstrated that apigenin inhibits multiple signal transduction pathways, specifically the IGF-I axis, PI3K-Akt, NF-(B and ¿-Catenin pathways. In this renewal application, we hypothesize that apigenin binds to and inhibit IKKa/¿, independent of NF-(B regulation thereby suppressing prostate cancer development and progression. Understanding the molecular mechanisms of apigenin may reveal key molecular targets for the development of more effective agents with fewer side-effects for future use in chemopreventive/therapeutic regimens.