PCDH-PC与前列腺癌神经内分泌分化

【作者】 杨学贞；

【导师】 郭应禄； Ralph Buttyan；

【作者基本信息】 北京大学 ， 外科学， 2005， 博士

【摘要】 Protocadherin-PC(PCDH-PC或PCDHY)是一个在抗刁亡、雄性激素非依赖性前列腺癌细胞中特异表达的基因。PCDH-PC定位于人类Y染色体上,该区域是在灵长类进化到人类的过程中由X染色体迁移到Y染色体的,并且在这个过程中有一段序列的缺失,使其表达产物位于胞浆中。PCDH-PC编码的多肽在C末断有一个丝氨酸富集区,与经典的Cadherin家族和β-catenin的结合域同源。在表达PCDH-PC的抗刁亡的LNCaP细胞胞浆和胞核中β-catenin蛋白表达水平升高,与这些细胞中Wnt信号增加是一致的。在此,我们转染前列腺癌细胞LNCaP细胞PCDH-PC表达载体或通过去除细胞培养液激素的方法诱导PCDH-PC表达,发现细胞核β-catenin蛋白积聚、启动子具有TCF结合位点的荧光素酶报告载体表达水平升高以及Wnt的靶基因c-myc、cyclin D、Cox-2表达水平升高。此外,转染前列腺癌细胞LNCaP细胞PCDH-PC表达载体或去除细胞培养液激素使LNCaP细胞分化为一种神经内分泌(NE)样细胞,NSE、Chromogranin-A蛋白表达水平升高。同样,转染LNCaP细胞稳定的β-catenin表达载体也可以发生这种NE分化。去除细胞培养液激素导致的LNCaP细胞Wnt信号的增加、NE分化可以被PCDH-PC siRNA、DN-TCF(dominant-negative TCF)或β-catenin siRNA阻断,表明PCDH-PC表达激活Wnt信号传导通路,从而发生NE分化。这些研究结果对于理解人类前列腺癌发展到更具侵袭性、雄性激素抵抗性阶段的过程具有非常重要的意义。更多还原

【Abstract】 Protocadherin-PC (PCDH-PC or PCDHY) is a gene product that is selectively expressed in apoptosis- and hormone-resistant human prostate cancer cells. The gene encoding PCDH-PC lies on the human Y-chromosome in a region that was translocated from the X-chromosome during the evolutionary transition from primates to humans. Compared to its X-homologue, PCDH-PC has a small deletion in its coding sequence that removes the signal sequence and the product of this gene is cytoplasmically localized. PCDH-PC has a small serine-rich domain in its C-terminal region that is homologous to theβ-catenin binding site of classical cadherins. Hormone-resistant variants of prostate cancer cells that express PCDH-PC have high levels ofβ-catenin protein in their nuclear fractions consistent with evidence that these cells have increased wnt-signaling. In this study, we show that transfection of human prostate cancer, LNCaP, cells with PCDH-PC expression vecors or culture of LNCaP cells in androgenfree medium, an experimental condition that induces expression of PCDH-PC, activates wnt signaling in these cells as assessed by nuclear accumulation ofβ-catenin protein, increased expression of luciferase from a reporter vector promoted by Tcf binding elements and increased expression of wnt target genes such as c-myc, cyclin D and Cox-2. Moreover LNCaP cells transfected with the PCDH-PC expression vector or grown in androgen-free medium transdifferentiate to neuroendocrine- (NE-) like cells marked by elevated expression of neuron specific enolase and chromogranin-A and this NE transdifferentiation is also observed when LNCaP cells are transfected by a stabilizedβ-catenin expression vector. Increased wnt signaling and NE transdifferentiation of LNCaP cells induced by culture in androgen-free medium was suppressed by effective siRNAs that target PCDH-PC as well as by dominant-negative Tcf or siRNA againstβ-catenin supporting the hypothesis that increased expression of PCDH-PC is driving the activation of wnt signaling and NE transdifferentiation by activating wnt signaling. These findings have significant implications for the understanding of the process through which prostate cancers progress to aggressive and hormone-resistant states in humans.更多还原