Rapamycin Regulation of the Androgen Receptor: Implications in Prostate Cancer

描述（由申请人提供）：在本申请中，我们证明mTOR抑制剂雷帕霉素和抗雄激素比卡鲁胺联合使用在雄激素非依赖性前列腺癌（AIPC）细胞中引起了长期的生长抑制和细胞凋亡，尽管这两种药物都没有单一药物的效果。本项目的总体目标是阐明受这种治疗影响的信号转导途径，从而导致细胞周期阻滞和凋亡。在初步研究中，我们提供了新的证据，证明单靠比卡鲁胺无法抑制AIPC细胞的生长和诱导细胞凋亡，这是由于mTOR下游存在一个强大的雄激素独立但雷帕霉素敏感的生存途径。另一方面，由于雷帕霉素治疗刺激ar依赖性细胞存活通路，作为单一疗法的雷帕霉素无法诱导长期生长抑制。因此，我们假设mTOR和AR通路平行调节前列腺癌细胞的存活，只有当这两条通路同时被抑制时才会诱导细胞凋亡。为了验证这一假设，我们设计了以下具体目标：为了验证抗雄激素比卡鲁胺不能诱导雄激素不依赖型前列腺癌细胞凋亡的假设，这是由于mTOR复合物mTORC1下游存在一种雄激素不依赖型但雷帕霉素敏感的细胞存活途径。mTORC1磷酸化下游靶点p70S6激酶和4E-BP1，一种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性前列腺癌细胞中雄激素非依赖性细胞的增殖和存活。此外，我们将研究mTOR通路是否在雄激素不依赖型人前列腺癌组织中被激活。2：验证mTOR抑制剂雷帕霉素长期治疗前列腺癌细胞刺激AR转录活性从而提高生存率和抵抗雷帕霉素生长抑制的假设。(i)我们将检验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）我们将检验雷帕霉素刺激的AR转录活性导致细胞存活增加的假设，从而导致对雷帕霉素治疗的耐药性。3. 验证雷帕霉素与比卡鲁胺联合治疗可诱导前列腺癌细胞凋亡并预防AIPC的假说。我们将确定雷帕霉素和比卡鲁胺联合使用是否能在体内阻止雄激素非依赖性前列腺肿瘤的生长。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性肿瘤是否能预防前列腺肿瘤复发。公共卫生相关性：这是雷帕霉素和比卡鲁胺联合应用于治疗雄激素非依赖性前列腺癌的临床前研究首次。这些药物的联合使用以前没有显示激素难治性细胞对激素治疗（雄激素剥夺或抗雄激素）敏感。这里提出的研究将证明利用比卡鲁胺和雷帕霉素联合治疗复发性前列腺癌患者的II/ III期临床试验是合理的。目前，雄激素非依赖性前列腺癌患者的选择是有限的；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.