1α,25(OH)_2D_3抑制前列腺癌机制研究进展

1α,25(OH)_2D_3是一种类固醇激素,在抑制前列腺癌发生和发展中具重要作用。1α,25(OH)_2D_3抑制前列腺癌涉及多方面的分子过程,包括G1/S细胞周期阻滞、促癌细胞凋亡、抗血管生成和阻止癌细胞迁移等。本文将从维生素D_3合成代谢羟化酶表达调控、VDR基因多态性、雄激素及受体调控、抗炎因子表达调控、胰岛素样生长因子及相关结合蛋白表达调控等方面阐述了近年来1α,25(OH)_2D_3抑制前列腺癌分子机制的研究进展,为维生素D_3预防和治疗前列腺癌的应用提供了参考。     

1α,25(OH)2 Vitamin D3 Modulates Avian T Lymphocyte Functions without Inducing CTL Unresponsiveness

1,25-Dihydroxyvitamin D3 (Vitamin D) is a naturally synthesized fat soluble vitamin shown to have immunomodulatory, anti-inflammatory and cancer prevention properties in human and murine models. Here, we studied the effects of Vitamin D on the functional abilities of avian T lymphocytes using chicken Interferon (IFN)-γ ELISPOT assay, BrdU proliferation assay, Annexin V apoptosis assay and PhosFlow for detecting phosphorylated signalling molecules. The results demonstrate that Vitamin D significantly inhibited the abilities of T lymphocytes to produce IFN-γ and proliferate in vitro (P≤0.05), but retained their ability to undergo degranulation, which is a maker for cytotoxicity of these cells. Similarly, Vitamin D did not inhibit Extracellular signal-Regulated Kinase (ERK) 1/2 phosphorylation, a key mediator in T cell signalling, in the stimulated T lymphocytes population, while reduced ERK1/2 phosphorylation levels in the unstimulated cells. Our data provide evidence that Vitamin D has immuno-modulatory properties on chicken T lymphocytes without inducing unresponsiveness and by limiting immuno-pathology can promote protective immunity against infectious diseases of poultry.     

Plasma membrane Pdia3 and VDR interact to elicit rapid responses to 1α,25(OH)2D3

1α,25-Dihydroxyvitamin D3 (1α,25(OH)₂D₃) regulates osteoblasts through genomic and rapid membrane-mediated responses. Here we examined the interaction of protein disulfide isomerase family A, member 3 (Pdia3) and the traditional vitamin D receptor (VDR) in plasma membrane-associated responses to 1α,25(OH)₂D₃. We found that Pdia3 co-localized with VDR and the caveolae scaffolding protein, caveolin-1 on the surface of MC3T3-E1 osteoblasts. Immunoprecipitation showed that both Pdia3 and VDR interacted with caveolin-1. Pdia3 further interacted with phospholipase A2 activating protein (PLAA), whereas VDR interacted with c-Src. 1α,25(OH)₂D₃ changed the interactions and transport of the two receptors and rapidly activated phospholipase A2 (PLA2) and c-Src. Silencing either receptor or caveolin-1 inhibited both PLA2 and c-Src, indicating that the two receptors function interdependently. These two receptor dependent rapid responses to 1α,25(OH)₂D₃ regulated gene expression, proliferation and apoptosis of MC3T3-E1 cells. These data demonstrate the importance of both receptors and caveolin-1 in mediating membrane responses to 1α,25(OH)₂D₃ and subsequently regulating osteoblast biology.     

The 25(OH)D(3)/1alpha,25(OH)(2)D(3)-24R-hydroxylase: a catabolic or biosynthetic enzyme?

The kidney is the major source of the circulating dihydroxylated metabolites of vitamin D, 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] and 24R,25-dihydroxyvitamin D(3) [24R,25(OH)(2)D(3)]. The enzymes which catalyze the production of these two dihydroxylated vitamin D metabolites are the 25(OH)D(3)-1alpha-hydroxylase (1alpha-hydroxylase) and -24R-hydroxylase (24R-hydroxylase), respectively. While there is no controversy regarding the fundamental importance of the 1alpha-hydroxylase in the production of the steroid hormone 1alpha,25(OH)(2)D(3), the biologic significance of the 24R-hydroxylase has been the subject of ongoing discussion. Some hold that it is strictly catabolic, leading to side chain oxidation and cleavage of 25-hydroxylated vitamin D sterols, and others hold that it plays a biosynthetic role in the production of 24R,25(OH)(2)D(3) which has biologic activities distinct from those of 1alpha,25(OH)(2)D(3). The 24R-hydroxylase has properties in common with other multicatalytic steroidogenic enzymes: (1) the enzyme carries out multiple oxidative and carbon-carbon bond cleavages; (2) it utilizes two natural substrates; (3) its regulation varies depending on the cell or tissue in which it occurs. The purpose of this paper is to review the current literature relevant to the characteristics of the 24R-hydroxylase and its regulation in the context of other multicatalytic steroid hydroxylases in order to provide a perspective regarding its possible function as both a catabolic and activating enzyme in the vitamin D endocrine system.     

Transformation of vitamin D3 to 1α,25-dihydroxyvitamin D3 via 25-hydroxyvitamin D3 using Amycolata sp. strains

To enzymatically synthesize active metabolites of vitamin D₃, we screened about 500 bacterial strains and 450 fungal strains, of which 12 strains were able to convert vitamin D₃ to 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] via 25-hyroxyvitamin D₃ [25(OH)D₃]. The conversion activity was only detected in strains belonging to the genus Amycolata among all the organisms tested. A preparative-scale conversion of vitamin D₃ to 25(OH)D₃ and 1,25(OH)₂D₃ in a 200-1 tank fermentor using A. autotrophica FERM BP-1573 was accomplished, yielding 8.3 mg 25(OH)D₃/l culture and 0.17 mg 1,25(OH)₂D₃/l culture. A related compound, vitamin D₂, could be also converted to 25-hydroxyvitamin D₂ and 1,25-dihydroxyvitamin D₂ using the same strain. The cytochrome P-450 of FERM BP-1573 was detected by reduced CO difference spectra in whole-cell suspensions. Vitamin D₃ in the culture induced cytochrome P-450 and the conversion activity simultaneously, suggesting that the hydroxylation at C-25 of vitamin D₃ and at C-1 of 25(OH)D₃ originates from cytochrome P-450.Correspondence to: J. Sasaki     

1α,25-Dihydroxyvitamin D(3) signaling pathways on calcium uptake in 30-day-old rat Sertoli cells

1α,25-Dihydroxyvitamin D(3) (1,25D(3)) is the active metabolite of vitamin D(3) and the major calcium regulatory hormone in tissues. The aim of this work was to investigate the mechanism of action of 1,25D(3) on (45)Ca(2+) uptake in Sertoli cells from 30-day-old rats. Results showed that 10(-9) and 10(-12) M 1,25D(3) increased the rate of (45)Ca(2+) uptake 5 and 15 min after hormone exposure and that 1α,25(OH)(2) lumisterol(3) (JN) produced a similar effect suggesting that 1,25D(3) action occurs via a putative membrane receptor. The involvement of voltage-dependent calcium channels (VDCC) in 1,25D(3) action was evidenced by using nifedipine, while the use of Bapta-AM demonstrated that intracellular calcium was not implicated. Moreover, the incubation with ouabain and digoxin increased the rate of (45)Ca(2+) uptake, indicating that the effect of 1,25D(3) may also result from Na(+)/K(+)-ATPase inhibition. In addition, we demonstrated that the mechanism underlying the hormone action involved extracellular signal-regulated kinase (ERK) and protein kinase C (PKC) activation in a phospholipase C-independent way. Furthermore, a local elevation of the level of cAMP, as demonstrated by incubating cells with dibutyryl cAMP or a phosphodiesterase inhibitor, produced an effect similar to that of 1,25D(3), and the inhibition of protein kinase A (PKA) nullified the hormone action. In conclusion, the stimulatory effect of 1,25D(3) on (45)Ca(2+) uptake in Sertoli cells occurs via VDCC, as well as PKA, PKC, and ERK activation. These protein kinases seem to act by inhibiting Na(+)/K(+)-ATPase or directly phosphorylating calcium channels. The Na(+)/K(+)-ATPase inhibition may result in Na(+)/Ca(2+) exchanger activation in reverse mode and consequently induce the uptake of calcium into the cells.     

1α,25(OH)2D3 inhibits FGF-2 release from oral squamous cell carcinoma cells through down-regulation of HBp17/FGFBP-1

Heparin-binding protein 17/fibroblast growth factor binding protein-1 (HBp17/FGFBP-1, GenBank accession no. NP-005121) is prominent for its role as the chaperone for fibroblast growth factor-2 (FGF-2), which plays a crucial role in angiogenesis as well as promoting tumor growth. HBp17/FGFBP-1 has been proposed as a candidate biomarker for a number of cancers since it is frequently found to be elevated in many cancer types including in the tissue and cell lines of oral squamous cell carcinomas (OSCC). Previously, we reported that 1α,25(OH)₂D₃ suppressed the HBp17/FGFBP-1 expression in OSCC by inhibiting nuclear factor-kappaB (NF-κB) expression via vitamin D3 receptor (VDR). In this paper, to further characterize the inhibitory effect of 1α,25(OH)₂D₃ on HBp17/FGFBP-1, we examined the cellular localization of HBp17/FGFBP-1 protein and FGF-2 protein in the UE OSCC cell line. We found that the treatment of OSCC cells with 40-nM 1α,25(OH)₂D₃ suppressed HBp17/FGFBP-1 expression both in the nucleus and cytosol and reduced FGF-2 release into the culture medium. The expression of HBp17/FGFBP-1 and FGF-2 was analyzed by immunofluorescence and enzyme-linked immunosorbent assay (ELISA). In summary, the ability of 1α,25(OH)₂D₃ to suppress the expression of HBp17/FGFBP-1 and FGF-2 strongly suggests a therapeutic potential as a molecular-targeted anticancer drug for FGF-dependent cancers.     

Two stages of the differentiation of HL-60 cells induced by 1α,25 dihydroxyvitamin D3; Commitment by 1α,25 dihydroxyvitamin D3 and promotion by DMSO

The differentiation of HL-60 cells induced by 1,25 dihydroxyvitamin D₃ was found to be separated into two stages, i.e. commitment and promotion. Most of the HL-60 cells were committed to monocyte/macrophage lineage by pretreatment with 1,25 dihydroxyvitamin D₃ (5–50 ng/ml) for 18–24 hr. The promotion in the second stage was inducer and lineage independent; treatment with 1.25% DMSO for 2 or 3 days promoted the differentiation of the committed HL-60 cells by 1,25 dihydroxyvitamin D₃ into monocyte/macrophage lineage, but not granulocyte lineage.Abbreviations used NEA nonspecific esterase activity - NBT nitroblue tetrazolium - DMSO dimethylsulfoxide - RA retinoic acid - TPA 12-O-tetradecanoylphorbol-13-acetate     

Signaling components of the 1α,25(OH)2D3-dependent Pdia3 receptor complex are required for Wnt5a calcium-dependent signaling

Wnt5a and 1α,25(OH)₂D₃ are important regulators of endochondral ossification. In osteoblasts and growth plate chondrocytes, 1α,25(OH)₂D₃ initiates rapid effects via its membrane-associated receptor protein disulfide isomerase A3 (Pdia3) in caveolae, activating phospholipase A₂ (PLA₂)-activating protein (PLAA), calcium/calmodulin-dependent protein kinase II (CaMKII), and PLA₂, resulting in protein kinase C (PKC) activation. Wnt5a initiates its calcium-dependent effects via intracellular calcium release, activating PKC and CaMKII. We investigated the requirement for components of the Pdia3 receptor complex in Wnt5a calcium-dependent signaling. We determined that Wnt5a signals through a CaMKII/PLA₂/PGE₂/PKC cascade. Silencing or blocking Pdia3, PLAA, or vitamin D receptor (VDR), and inhibition of calmodulin (CaM), CaMKII, or PLA₂ inhibited Wnt5a-induced PKC activity. Wnt5a activated PKC in caveolin-1-silenced cells, but methyl-beta-cyclodextrin reduced its stimulatory effect. 1α,25(OH)₂D₃ reduced stimulatory effects of Wnt5a on PKC in a dose-dependent manner. In contrast, Wnt5a had a biphasic effect on 1α,25(OH)₂D₃-stimulated PKC activation; 50 ng/ml Wnt5a caused a 2-fold increase in 1α,25(OH)₂D₃-stimulated PKC but higher Wnt5a concentrations reduced 1α,25(OH)₂D₃-stimulated PKC activation. Western blots showed that Wnt receptors Frizzled2 (FZD2) and Frizzled5 (FZD5), and receptor tyrosine kinase-like orphan receptor 2 (ROR2) were localized to caveolae. Blocking ROR2, but not FZD2 or FZD5, abolished the stimulatory effects of 1α,25(OH)₂D₃ on PKC and CaMKII. 1α,25(OH)₂D₃ membrane receptor complex components (Pdia3, PLAA, caveolin-1, CaM) interacted with Wnt5a receptors/co-receptors (ROR2, FZD2, FZD5) in immunoprecipitation studies, interactions that changed with either 1α,25(OH)₂D₃ or Wnt5a treatment. This study demonstrates that 1α,25(OH)₂D₃ and Wnt5a mediate their effects via similar receptor components and suggests that these pathways may interact.     

19-Nor-2α-(3-hydroxypropyl)-1α,25-dihydroxyvitamin D3 (MART-10) is a potent cell growth regulator with enhanced chemotherapeutic potency in liver cancer cells

The discovery that the active form of vitamin D, 1α,25-dihydroxyvitamin D [1α,25(OH)₂D] can modulate cellular proliferation and differentiation of cancer cells has led to its potential application as a chemotherapeutic agent to treat a variety of cancers. However, the use of 1α,25(OH)₂D is limited due to its lethal side effect of hypercalcemia upon systemic administration. To overcome this drawback, numerous analogs have been synthesized. In this report, we examined the anti-proliferative activity of a new analog, 19-nor-2α-(3-hydroxypropyl)-1α,25(OH)₂D₃ (MART-10), in HepG2 liver cancer cells, and studied the potential mechanisms mediating this action. We found that MART-10 exhibited approximately 100-fold greater activity than 1α,25(OH)₂D₃ in inhibiting HepG2 cell proliferation as determined by cell number counting method. MART-10 was also approximately 100-fold more potent than 1α,25(OH)₂D₃ in the upregulation of p21 and p27, that in turn arrested HepG2 cells at the G₀/G₁ phase to a greater extent. Given that no active caspase 3 was detected and treatment with 1α,25(OH)₂D₃ or MART-10 did not further increase the fractions of apoptotic and necrosis cells over the controls, the growth-inhibitory effect of 1α,25(OH)₂D₃ and MART-10 on HepG2 cells may not involve apoptosis. Overall, our findings suggest that MART-10 is a good candidate as a novel therapeutic regimen against liver cancer. Further pre-clinical studies using animal models and the subsequent human clinical trials are warranted.     

1α,25-Dihydroxyvitamin D3 exerts tissue-specific effects on estrogen and androgen metabolism

It is well-known that 1α,25-dihydroxyvitamin D(3) and analogs exert anti-proliferative and pro-differentiating effects and these compounds have therefore been proposed to be of potential use as anti-cancer agents. Due to its effects on aromatase gene expression and enzyme activity, 1α,25-dihydroxyvitamin D(3) has been proposed as an interesting substance in breast cancer treatment and prevention. In the present study, we have examined the effects of 1α,25-dihydroxyvitamin D(3) on estrogen and androgen metabolism in adrenocortical NCI-H295R cells, breast cancer MCF-7 cells and prostate cancer LNCaP cells. The NCI-H295R cell line has been proposed as a screening tool to study endocrine disruptors. We therefore studied whether this cell line reacted to 1α,25-dihydroxyvitamin D(3) treatment in the same way as cells from important endocrine target tissues. 1α,25-Dihydroxyvitamin D(3) exerted cell line-specific effects on estrogen and androgen metabolism. In breast cancer MCF-7 cells, aromatase gene expression and estradiol production were decreased, while production of androgens was markedly increased. In NCI-H295R cells, 1α,25-dihydroxyvitamin D(3) stimulated aromatase expression and decreased dihydrotestosterone production. In prostate cancer LNCaP cells, aromatase expression increased after the same treatment, as did production of testosterone and dihydrotestosterone. In summary, our data show that 1α,25-dihydroxyvitamin D(3) exerts tissue-specific effects on estrogen and androgen production and metabolism. This is important knowledge about 1α,25-dihydroxyvitamin D(3) as an interesting substance for further research in the field of breast cancer prevention and treatment. Furthermore, the observed cell line-specific effects are of importance in the discussion about NCI-H295R cells as a model for effects on estrogen and androgen metabolism.