Wu G, Iwamura M, di Sant'Agnese P A, Deftos L J, Cockett A T, Gershagen S
Department of Urology, University of Rochester Medical Center, New York 14642, USA.
Urology. 1998 May;51(5A Suppl):110-20. doi: 10.1016/s0090-4295(98)00077-6.
Parathyroid hormone-related protein (PTHrP) is a primary factor in the pathogenesis of malignancy-associated hypercalcemia. By alternative splicing, the human PTHrP gene can generate three different species of mRNA that encode three initial translational isoforms of 139, 173, and 141 amino acids. We recently reported that PTHrP was present in normal prostatic neuroendocrine cells and was overexpressed in prostate cancer tissue as demonstrated by immunostaining. This study was undertaken to further clarify the complex expression of PTHrP gene in normal prostate tissue and prostate cancer.
PTHrP mRNA in samples prepared from normal prostate tissue, prostate cancer, and three prostate cancer cell lines, PC3, LNCaP, and DU145 was assessed using Northern hybridization. Expressed PTHrP isoforms were deduced from differential reverse transcription-polymerase chain reaction (RT-PCR) assays with exon-specific primers. Further localization of different species of PTHrP mRNA was performed using nonradioactive in situ hybridization with exon-specific probes on consecutive sections of normal and neoplastic prostate tissue.
Northern hybridization showed that the PTHrP expression level was higher in prostate cancer than in normal prostate tissue. All three PTHrP isoforms could be detected in normal prostate tissues and prostate cancer with differential RT-PCR. Further analysis using in situ hybridization with exon-specific probes revealed that all three PTHrP isoforms were present in prostatic neuroendocrine cells and only PTHrP-1-139 isoform could be clearly detected in prostate cancer tissue. Two androgen-insensitive cell lines, PC3 and DU145, derived from a bone metastasis and a brain metastasis, respectively, expressed all three mRNA species encoding for the three isoforms, but DU145 cells expressed less than PC3 cells. Androgen-sensitive LNCaP cells exhibited a low level of expression of mRNA species encoding for PTHrP-1-139 and PTHrP-1-173, and no expression of PTHrP1-141 isoform.
All three initial translational isoforms of PTHrP are produced by prostatic neuroendocrine cells. The mature products of PTHrP might exert their effects on other prostatic epithelial cells in a paracrine fashion and also participate in the homeostatic regulation of the ejaculate. In prostate cancer, differential expression of these three isoforms is evident and PTHrP-1-139 isoform is more abundant than the other two forms. These findings are valuable for designing future research studies to further elucidate the biological functions of PTHrP in normal prostatic glands and prostate cancer.
甲状旁腺激素相关蛋白（PTHrP）是恶性肿瘤相关性高钙血症发病机制中的一个主要因素。通过可变剪接，人PTHrP基因可产生三种不同的mRNA，它们编码139、173和141个氨基酸的三种初始翻译异构体。我们最近报道，免疫染色显示PTHrP存在于正常前列腺神经内分泌细胞中，并在前列腺癌组织中过表达。本研究旨在进一步阐明PTHrP基因在正常前列腺组织和前列腺癌中的复杂表达情况。
使用Northern杂交法评估从正常前列腺组织、前列腺癌以及三种前列腺癌细胞系PC3、LNCaP和DU145制备的样本中的PTHrP mRNA。用外显子特异性引物通过差异逆转录-聚合酶链反应（RT-PCR）分析推导表达的PTHrP异构体。使用非放射性原位杂交法，用外显子特异性探针在正常和肿瘤性前列腺组织的连续切片上对不同种类的PTHrP mRNA进行进一步定位。
Northern杂交显示前列腺癌中PTHrP的表达水平高于正常前列腺组织。通过差异RT-PCR可在正常前列腺组织和前列腺癌中检测到所有三种PTHrP异构体。使用外显子特异性探针进行原位杂交的进一步分析显示，所有三种PTHrP异构体均存在于前列腺神经内分泌细胞中，而在前列腺癌组织中只能清楚地检测到PTHrP-1-139异构体。两种雄激素不敏感细胞系PC3和DU145分别来源于骨转移和脑转移，表达编码三种异构体的所有三种mRNA，但DU145细胞的表达低于PC3细胞。雄激素敏感的LNCaP细胞中编码PTHrP-1-139和PTHrP-1-173的mRNA表达水平较低，且不表达PTHrP1-141异构体。
PTHrP的所有三种初始翻译异构体均由前列腺神经内分泌细胞产生。PTHrP成熟产物可能以旁分泌方式作用于其他前列腺上皮细胞，并参与射精的稳态调节。在前列腺癌中，这三种异构体的差异表达明显，且PTHrP-1-139异构体比其他两种形式更为丰富。这些发现对于设计未来的研究以进一步阐明PTHrP在正常前列腺和前列腺癌中的生物学功能具有重要价值。
