Sepulveda Veronica A Tovar, Weigel Nancy L, Falzon Miriam
Department of Pharmacology and Toxicology, and Sealy Center for Molecular Science, University of Texas Medical Branch, 10th and Market Streets, Galveston, TX 77555, USA.
Steroids. 2006 Feb;71(2):102-15. doi: 10.1016/j.steroids.2005.08.009. Epub 2005 Oct 21.
Parathyroid hormone-related protein (PTHrP) increases the growth and osteolytic potential of prostate cancer cells, making it important to control PTHrP expression in these cells. We show that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and its non-hypercalcemic analog, EB1089, decrease PTHrP mRNA and cellular protein levels in the androgen-dependent human prostate cancer cell line LNCaP and its androgen-independent derivative, the C4-2 cell line. This effect is mediated via a negative Vitamin D response element (nVDREhPTHrP) within the human PTHrP gene and involves an interaction between nVDREhPTHrP and the Vitamin D receptor (VDR). The retinoid X receptor (RXR) is a frequent heterodimeric partner of the VDR. We show that RXRalpha forms part of the nuclear protein complex that interacts with nVDREhPTHrP along with the VDR in LNCaP and C4-2 cells. We also show that the RXR ligand, 9-cis-retinoic acid, downregulates PTHrP mRNA levels; this decrease is more pronounced in LNCaP than in C4-2 cells. In addition, 9-cis-retinoic acid enhances the 1,25(OH)2D3-mediated downregulation of PTHrP expression in both cell lines; this effect also is more pronounced in LNCaP cells. Proliferation of LNCaP, but not C4-2, cells is decreased by 9-cis-retinoic acid. Promoter activity driven by nVDREhPTHrP cloned upstream of the SV40 promoter and transiently transfected into LNCaP and C4-2 cells is downregulated in response to 1,25(OH)2D3 and EB1089 in both cell lines. Co-treatment with these compounds and 9-cis-retinoic acid further decreases CAT activity in LNCaP, but not C4-2, cells. These results indicate that PTHrP gene expression is regulated by 1,25(OH)2D3 in a cell type-specific manner in prostate cancer cells.
甲状旁腺激素相关蛋白（PTHrP）可提高前列腺癌细胞的生长和溶骨潜能，因此控制这些细胞中PTHrP的表达至关重要。我们发现，1,25 - 二羟基维生素D3（1,25(OH)2D3）及其非高钙血症类似物EB1089可降低雄激素依赖的人前列腺癌细胞系LNCaP及其雄激素非依赖衍生物C4 - 2细胞系中PTHrP mRNA和细胞蛋白水平。这种效应是通过人PTHrP基因内的负性维生素D反应元件（nVDREhPTHrP）介导的，并且涉及nVDREhPTHrP与维生素D受体（VDR）之间的相互作用。视黄酸X受体（RXR）是VDR常见的异源二聚体伴侣。我们发现，在LNCaP和C4 - 2细胞中，RXRα是与nVDREhPTHrP以及VDR相互作用的核蛋白复合物的一部分。我们还发现，RXR配体9 - 顺式视黄酸可下调PTHrP mRNA水平；这种降低在LNCaP细胞中比在C4 - 2细胞中更明显。此外，9 - 顺式视黄酸增强了两种细胞系中1,25(OH)2D3介导的PTHrP表达下调；这种效应在LNCaP细胞中也更明显。9 - 顺式视黄酸可降低LNCaP细胞（而非C4 - 2细胞）的增殖。在SV40启动子上游克隆并瞬时转染到LNCaP和C4 - 2细胞中的nVDREhPTHrP驱动的启动子活性，在两种细胞系中均因1,25(OH)2D3和EB1089而下调。这些化合物与9 - 顺式视黄酸联合处理可进一步降低LNCaP细胞（而非C4 - 2细胞）中的CAT活性。这些结果表明，在前列腺癌细胞中，PTHrP基因表达以细胞类型特异性方式受1,25(OH)2D3调节。
