Rapamycin Regulation of the Androgen Receptor: Implications in Prostate Cancer

描述(申请人提供)：在本申请中，我们表明mTOR抑制剂雷帕霉素和抗雄激素药物比卡鲁胺联合使用可导致雄激素非依赖性前列腺癌(AIPC)细胞的长期生长抑制和凋亡，尽管这两种药物都没有与单一药物相同的效果。本项目的总体目标是阐明该治疗影响的信号转导通路，从而导致细胞周期停滞和细胞凋亡。在初步研究中，我们提供了新的证据，证明比卡鲁胺单独无法抑制AIPC细胞的生长和诱导细胞凋亡，这是因为mTOR下游存在强大的雄激素非依赖性但雷帕霉素敏感的生存途径。另一方面，作为单一疗法的雷帕霉素不能诱导长期的生长抑制，这是因为雷帕霉素刺激了AR依赖的细胞生存途径。因此，我们假设mTOR和AR通路同时调节前列腺癌细胞的存活，只有当这两个通路同时被抑制时才能诱导细胞凋亡。为了验证这一假说，我们设计了以下特定的目标：1.为了验证抗雄激素药物比卡鲁胺不能诱导雄激素非依赖性前列腺癌细胞凋亡的假说，是因为mTORC1下游存在一条雄激素非依赖性的、但对雷帕霉素敏感的细胞存活通路。MTORC1磷酸化下游靶标p70S6蛋白和4E-BP1，4E-BP1是eIF4E结合蛋白。我们将确定mTORC1/4E-BP1/eIF4E通路的激活增加是否促进雄激素依赖型前列腺癌细胞的增殖和存活。此外，我们还将研究mTOR通路在雄激素非依赖性前列腺癌组织中是否被激活。2：为了验证长期用mTOR抑制剂雷帕霉素处理前列腺癌细胞可以刺激AR转录活性从而提高存活率和抵抗雷帕霉素抑制生长的假设。(I)我们将测试长期雷帕霉素治疗刺激前列腺癌细胞AR转录活性的假设。(Ii)我们将检验这样一种假设，即雷帕霉素刺激的AR转录活性导致细胞存活率增加，从而导致对雷帕霉素治疗的抵抗。3.验证雷帕霉素和比卡鲁胺联合作用诱导前列腺癌细胞凋亡和预防AIPC的假说。我们将在体内确定雷帕霉素和比卡鲁胺联合应用是否能阻止雄激素非依赖性前列腺癌的生长。此外，我们将在前列腺癌进展模型中研究雷帕霉素和比卡鲁胺联合治疗雄激素依赖型肿瘤是否能防止前列腺癌复发。公共卫生相关性：这是雷帕霉素和比卡鲁胺首次联合用于雄激素非依赖性前列腺癌的临床前研究。这些药物的组合以前从未被证明能使激素不敏感的细胞对激素治疗(雄激素剥夺或抗雄激素)敏感。这里提出的研究将证明使用比卡鲁胺和雷帕霉素联合治疗复发前列腺癌患者的第二阶段/第三阶段临床试验是合理的。目前，雄激素非依赖性前列腺癌患者的选择有限；因此，这样的研究将为新的治疗选择打开大门。

DESCRIPTION (provided by applicant): In this application, we show that the combination of the mTOR inhibitor rapamycin and the anti-androgen bicalutamide caused long-term growth inhibition and apoptosis in androgen independent prostate cancer (AIPC) cells despite neither drug having the same effect as single agents. The overall objective of the present project is to elucidate the signal transduction pathways affected by this treatment, which lead to cell cycle arrest and apoptosis. In preliminary studies, we provide novel evidence that bicalutamide alone was unable to inhibit cell growth and induce apoptosis in AIPC cells, due to the presence of a strong androgen-independent, but rapamycin-sensitive, survival pathway downstream of mTOR. On the other hand, rapamycin as monotherapy was unable to induce long-term growth inhibition due to the stimulation of an AR-dependent cell survival pathway by rapamycin treatment. Thus we hypothesize that the mTOR and AR pathways regulate survival in prostate cancer cells in parallel, and apoptosis was induced only when both pathways were simultaneously inhibited. The following specific aims have been designed to test this hypothesis: 1. To test the hypothesis that the anti-androgen bicalutamide is unable to induce apoptosis in androgen-independent prostate cancer cells due to the presence of an androgen-independent, but rapamycin-sensitive, cell survival pathway downstream of mTORC1, a complex of mTOR. mTORC1 phosphorylates downstream targets p70S6 kinase and 4E-BP1, an eIF4E binding protein. We will determine whether increased activation of the mTORC1/4E-BP1/eIF4E pathway promotes androgen-independent cell proliferation and survival in androgen-dependent prostate cancer cells. In addition, we will examine whether the mTOR pathway is activated in androgen-independent human prostate cancer tissues. 2: To test the hypothesis that long-term treatment of prostate cancer cells with the mTOR inhibitor rapamycin stimulates AR transcriptional activity resulting in increased survival and resistance to growth inhibition by rapamycin. (i) We will test the hypothesis that long-term rapamycin treatment stimulates AR transcriptional activity in prostate cancer cells. (ii) We will test the hypothesis that rapamycin-stimulated AR transcriptional activity results in increased cell survival which causes resistance to rapamycin treatment. 3. To test the hypothesis that combination treatment with rapamycin and bicalutamide induce apoptosis in prostate cancer cells and prevent AIPC. We will determine whether rapamycin and bicalutamide in combination prevent the growth of androgen-independent prostate tumors in vivo. Further, we will investigate whether combination treatment with rapamycin and bicalutamide in androgen-dependent tumors prevent the recurrence of prostate tumors in a model of prostate cancer progression. PUBLIC HEALTH RELEVANCE: This is the first time that the combination of rapamycin and bicalutamide will be used in preclinical studies for the treatment of androgen-independent prostate cancer. The combination of these drugs has not been shown before to sensitize hormone-refractory cells to hormone therapy (androgen deprivation or anti-androgens). The studies proposed here would justify a Phase II/Phase III clinical trial utilizing the combination of bicalutamide and rapamycin for the treatment of patients who experience recurrent prostate cancer. Currently, the options for patients with androgen-independent prostate cancer are limited; hence such a study would open the doors for a new treatment option.