Androgenic Inactivation of FOXO1 in Prostate Cancer

描述（由申请人提供）：前列腺癌是美国癌症死亡的第二大原因。前列腺癌细胞的生长和存活依赖于雄激素。雄激素的促有丝分裂作用与其对细胞周期调节分子如细胞周期蛋白依赖性激酶2和4（CDK 2和CDK 4）的调节有关。然而，雄激素介导的细胞存活的分子机制尚未完全阐明。我们和其他人已经表明，雄激素通过拮抗抑癌蛋白PTEN的功能来促进前列腺癌的生存。进一步的研究表明，雄激素通过直接抑制叉头转录因子FOXO 1（FKHR）的功能来阻断PTEN信号传导，FOXO 1是PTEN的关键下游靶点。我们的初步数据表明，CDK 2在体外和体内与FOXO 1相互作用并磷酸化FOXO 1。CDK 2通过丝氨酸249的磷酸化抑制FOXO 1的功能。重要的是，CDK 2介导的磷酸化和FOXO 1的抑制可以在化疗剂和辐射诱导的DNA损伤后逆转。鉴于雄激素介导的增殖和存活的作用以及临床上雄激素消融和放射治疗之间相互作用的抗肿瘤作用，我们假设CDK 2介导的FOXO 1失活在前列腺癌细胞中雄激素刺激的增殖、存活和氧化应激中起重要作用。为了验证这一假设，我们打算确定（1）CDK 2介导的FOXO 1磷酸化是否在雄激素刺激的前列腺癌细胞增殖和存活中起重要作用;（2）雄激素诱导的FOXO 1磷酸化是否抑制前列腺癌细胞中FOXO 1的转录活性;（3）FOXO 1的激活是否是介导雄激素去除和放射治疗协同抗肿瘤作用的关键因素。这项工作的发现将为雄激素诱导前列腺癌细胞增殖和存活的工作机制提供新的见解。此外，他们应该提高我们的理解的潜在机制的治疗优势，雄激素消融和放射治疗在临床上。

DESCRIPTION (provided by applicant): Prostate cancer is the second leading cause of cancer death in the United States. Cancer cells in the prostate depend on androgens for growth and survival. Mitogenic effects of androgens have been linked to their modulation of cell cycle regulatory molecules such as cyclin-dependent kinase 2 and 4 (CDK2 and CDK4). However, the molecular mechanisms for androgen-mediated cell survival are not fully elucidated. We and others have shown that androgens promote prostate cancer survival by antagonizing the function of PTEN, a tumor suppressor protein. Further studies have revealed that androgens block PTEN signaling by directly inhibiting the function of the forkhead transcription factor FOXO1 (FKHR), a key downstream target of PTEN. Our preliminary data demonstrate that CDK2 interacts with and phosphorylates FOXO1 in vitro and in vivo. CDK2 inhibits the function of FOXO1 through phosphorylation of serine 249. Importantly, CDK2- mediated phosphorylation and inhibition of FOXO1 can be reversed upon DNA damage induced by chemotherapeutic agents and irradiation. In view of the roles of androgen-mediated proliferation and survival and the anti-tumor effect of the interaction between androgen ablation and radiation therapy in the clinic, we hypothesize that CDK2-mediated inactivation of FOXO1 plays an important role in androgen-stimulated proliferation, survival, and oxidative stress in prostate cancer cells. To test this hypothesis, we propose to determine (1) whether CDK2-mediated phosphorylation of FOXO1 plays an essential role in androgen- stimulated proliferation and survival of prostate cancer cells; (2) whether androgen-induced phosphorylation of FOXO1 inhibits FOXO1 transcriptional activity in prostate cancer cells; (3) whether activation of FOXO1 is a key factor that mediates the synergistic anti-tumor effect of androgen ablation and radiation therapy. The findings from this work will provide new insights into the working mechanisms of androgen-induced proliferation and survival of prostate cancer cells. Moreover, they should enhance our understanding of the underlying mechanisms of the therapeutic advantage of androgen ablation and radiation therapy in the clinic.