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，在大多数男性中会导致疾病缓解。然而，CAP最终会复发，此后患者的中位生存期不到一年。因此，从雄激素依赖到雄激素非依赖性生长的转变是前列腺癌进展的关键时刻。前列腺癌的发育和生长需要雄激素，一种功能强大的雄激素受体(AR)和促进生长的AR靶基因的表达。AR在复发性CAP中的表达与雄激素依赖型CAP相似，我们对雄激素依赖型CWR22人CAP异种移植的研究结果表明，尽管没有睾丸雄激素，但复发性CWR-22中AR调节基因的表达增加。该计划项目的统一假设是，AR和AR调节基因在雄激素剥夺治疗期间CAP的复发生长中起作用。该方案由三个密切相关的项目组成。项目1将检验这一假设，即AR的表达和功能的变化会影响CAP的进展，并且这些变化在非裔美国人和高加索美国人之间存在差异。将检测AR和组织中雄激素的水平。AR的突变将被识别，突变的ARs的功能将被表征。对去雄激素后肿瘤复发前后的CAP进行AR突变分析，AR基因扩增和AR及AR诱导的促生长基因的表达项目2将验证这样的假设：在复发的CWR-22中，AR是通过雄激素非依赖性机制重新激活的，在没有雄激素的情况下激活AR会增加AR调节的促生长基因的表达。将对复发的CWR-22中的AR进行生化分析，以获得与激活相关的特性。将确定雄激素调节的促生长基因，并确定它们在复发的CWR22中的表达。在复发的CWR22中，AR将通过表达显性负向突变体AR或抗AR核酶来敲除，以确定AR在促进生长基因上调中的作用。根据这些结果，将确定雄激素非依赖性AR激活或AR非依赖性生长促进AR靶基因表达的机制。项目3将测试这一假设，即复发性CAP是转化的含有AR的前列腺干细胞的副产物，可以被雄激素刺激增殖，但对凋亡诱导的雄激素缺乏不敏感。干细胞株将被转化，并确定它们形成雄激素依赖和雄激素非依赖性CAP的能力。此外，AR在维持雄激素非依赖性帽的致瘤潜能中的因果作用将被确定。肿瘤干细胞将从CWR22异种移植中分离出来，并评估AR在移植到去势小鼠体内时在肿瘤产生中的作用。将进行类似的研究，以确定从人帽建立的暂时性异种移植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使分析存档样本在雄激素依赖和雄激素非依赖性CAP之间干细胞频率的差异成为可能。

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.