PROSTATE CANCER: TRANSITION TO ANDROGEN-INDEPENDENCE

雄激素消融术仍然是晚期前列腺癌（CaP）的标准治疗方法，并在大多数男性中引起疾病缓解。然而，CaP最终会复发，此后患者的中位生存期不到一年。因此，从雄激素依赖型到雄激素非依赖型生长的转变是前列腺癌进展的一个关键节点。前列腺的发育和生长需要雄激素、雄激素受体（AR）的功能和促生长AR靶基因的表达。AR在复发性Cap中的表达与雄激素依赖性Cap中的表达相似，我们对雄激素依赖性CWR22人Cap异种移植物的研究结果表明，尽管缺乏睾丸雄激素，AR调节基因的表达在复发性CWR22中增加。该项目的统一假设是，在雄激素剥夺治疗期间，AR和AR调节基因在CaP的复发生长中起作用。该计划由三个密切相关的项目组成。项目1将检验AR表达和功能的变化影响CaP进展的假设，并且这些变化在非裔美国人和白种人美国人之间有所不同。将检测AR和组织雄激素水平。AR的突变将被识别，突变Ars的功能将被表征。我们将在雄激素剥夺后肿瘤复发前后对CaP进行系列活组织检查，分析AR突变、AR基因扩增以及AR和AR诱导的促生长基因的表达。项目2将检验AR在复发的cwr22中通过雄激素不依赖的机制被重新激活的假设，在缺乏雄激素的情况下，AR的激活增加了AR调节的促生长基因的表达。复发性CWR-22中的AR将进行生化分析，以确定其与活化相关的特性。将鉴定雄激素调节的生长促进基因，并确定其在复发性CWR22中的表达。在复发性CWR22中，AR将通过显性负突变AR或抗AR核酶的表达被敲除，以确定AR在促生长基因上调中的作用。根据这些结果，将确定雄激素不依赖型AR激活或AR不依赖型促生长AR靶基因表达的机制。项目3将验证一个假设，即复发性CaP是含有AR的转化前列腺干细胞的产物，可以被雄激素刺激增殖，但对凋亡诱导的雄激素剥夺不敏感。干细胞系将被转化，并确定其产生雄激素依赖性和雄激素非依赖性CaP的能力。此外，AR在维持雄激素非依赖性CaP的致瘤潜能中的因果作用将被确定。将从CWR22异种移植物中分离出肿瘤干细胞，并评估AR在被阉割小鼠体内移植后肿瘤产生中的作用。将进行类似的研究，以表征从人类CaP建立的瞬时异种移植物中干细胞成分的表型，并确定它们形成雄激素非依赖性肿瘤的能力。肿瘤干细胞群体的特征将允许分析存档标本中雄激素依赖性和雄激素非依赖性CaP之间干细胞频率的差异。

Androgen ablation remains the standard therapy with advanced prostate cancer (CaP) and causes disease remission in most men. However, CaP eventually recurs and thereafter the median survival of patients is less than one year. Thus the transition from androgen-dependent to androgen- independent growth represents a critical juncture in the progression of prostate cancer. Development and growth of the prostate gland require androgen, a functioning androgen receptor (AR) and expression of growth promoting AR target genes. Expression of AR in recurrent Cap is similar to that in androgen-dependent CaP and our results from studies on the androgen-dependent CWR22 human CaP xenograft indicate that expression of AR-regulated genes is increased in recurrent CWR-22 despite the absence of testicular androgen. The Program Project's unifying hypothesis is that AR and AR-regulated genes have a role in the recurrent growth of CaP during androgen deprivation therapy. The Program consists of three closely related projects. Project 1 will test the hypothesis that changes in the expression and function of AR effect the progression of CaP and that these changes differ between African Americans and Caucasian Americans. AR and tissue levels of androgens will be assayed. Mutations in AR will be identified and the function of mutant Ars characterized. Serial biopsies of CaP spanning the period before and after tumor recurrence following androgen deprivation will be analyzed for AR mutations, AR gene amplification and the expression of AR and AR-induced growth promoting genes Project 2 will test the hypothesis that AR is reactivated in the recurrent CWR-22 by an androgen-independent mechanism and its activation in the absence of androgen increases the expression of AR-regulated growth promoting genes. AR in recurrent CWR-22 will be analyzed biochemically for properties associated with activation. Androgen-regulated growth promoting genes will be identified and their expression in recurrent CWR22 determined. AR will be knocked out in recurrent CWR22 by expression of a dominant negative mutant AR or an anti-AR ribozyme to determine the role of AR in up-regulation of the growth promoting genes. Depending on these results the mechanism of androgen-independent AR activation or AR-independent expression of growth promoting AR target genes will be identified. Project 3 will test the hypothesis that recurrent CaP is the outgrowth of a transformed prostate stem cell that contains AR, can be stimulated to proliferate by androgen, but is insensitive to apoptosis induced androgen deprivation. Stem cell lines will be transformed and their capacity to develop androgen-dependent and androgen-independent CaP determined. Additionally, the causal role of AR in maintenance of tumorigenic potential of androgen-independent CaP will be determined. Tumor stem cells will be isolated from the CWR22 xenograft and the role of AR evaluate in the production of tumors when transplanted into castrated mice. Comparable studies will be undertaken to characterize the phenotype of the stem cell components in transient xenografts established from human CaP and determine their capacity to form androgen-independent tumors. Characterization of tumor stem cell populations will allow analysis of archived specimens for differences in frequencies of stem cells between androgen-dependent and androgen-independent CaP.