cholecalciferol and Osteosarcoma

Osteosarcoma is a type of malignant bone tumor with high metastasis and poor prognosis. Previous studies have demonstrated the involvement of LIM kinase 1 (LIMK1) in the proliferation of osteosarcoma cells. LIMK1 is overexpressed in human osteosarcoma tissues and cell lines. To further study LIMK1-associated mechanisms, we used shRNA targeted to the LIMK1 gene to block its expression in the osteosarcoma cell lines MG63 and U2OS. Insulin promoted the proliferation of MG63 cells in a time- and dose-dependent manner, however, this insulin induced proliferation was significantly inhibited by transfection of shRNA targeted to the LIMK1 gene, as well as by the PI3K inhibitor LY294002, but not by the mitogen‑activated protein kinase (MAPK) inhibitor PD98059. The level of cofilin phosphorylation was increased significantly following stimulation of insulin for 24 h, indicating the activation of LIMK1. MG63 cell proliferation was also significantly inhibited by 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) in a time-dependent manner. Furthermore, 1,25(OH)2D3 negated the inhibitory effect of LIMK1 shRNA, indicating that LIMK1 is important in the inhibitory pathway of 1,25(OH)2D3. The present study confirms that LIMK1 is important in regulating osteosarcoma cell proliferation via the insulin/PI3K/LIMK1 signaling pathway, thus the development of gene therapy for osteosarcoma targeting LIMK1 is warranted.

Topics: Actin Depolymerizing Factors; Cell Line, Tumor; Cell Proliferation; Cholecalciferol; Chromones; Flavonoids; Humans; Insulin; Lim Kinases; Mitogen-Activated Protein Kinases; Morpholines; Osteosarcoma; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Protein Kinase Inhibitors; RNA Interference; RNA, Small Interfering; Signal Transduction

The N-myc downstream regulated gene 1 (NDRG1)/Cap43 is closely associated with cell differentiation, and its expression is induced by hypoxia and increasing intracellular calcium levels. Whether the NDRG1/Cap43 expression in cancer cells is a predictive marker of good or poor prognosis in patients, depends upon tumor types and differentiation status. In this study, we examined whether the NDRG1/Cap43 expression was involved in the differentiation of osteosarcoma cells, using three osteosarcoma cell lines, MG63, U2OS and SaOS2. The NDRG1/Cap43 expression in MG63 and U2OS was significantly enhanced by vitamin D3, which also induced the production of osteocalcin, a differentiation marker of osteoblasts. The knockdown of NDRG1/Cap43 using small interfering RNA also suppressed the production of osteocalcin and enhanced cell proliferation, accompanied by the suppression of p21 expression. Furthermore, the acquired invasiveness of osteosarcoma cells during the invasion in Matrigel resulted in the decreased expression of NDRG1/Cap43. On the basis of these results, our proposed role for NDRG1/Cap43 would be in the capacity of differentiation and invasion in osteosarcoma cells.

Topics: Bone Neoplasms; Cell Cycle Proteins; Cell Differentiation; Cell Line, Tumor; Cell Movement; Cholecalciferol; Cyclin-Dependent Kinase Inhibitor p21; Gene Expression Regulation, Neoplastic; Humans; Intracellular Signaling Peptides and Proteins; Neoplasm Invasiveness; Osteocalcin; Osteosarcoma; RNA Interference; Time Factors

Based on their content of prolactin receptors, osteosarcoma cells were predicted to be responsive to prolactin (PRL), but whether PRL would be beneficial or contribute to pathogenesis was unclear. 1,25(OH)(2) vitamin D(3) [1alpha,25(OH)(2)D(3)] has antiproliferative effects on osteosarcoma cells, and a complex interregulatory situation exists between PRL and 1alpha,25(OH)(2)D(3). Using osteosarcoma cells, Western blot, real time RT-PCR, and promoter-luciferase assays, we have examined the interaction between PRL and 1alpha,25(OH)(2)D(3) and demonstrated that physiological concentrations of PRL block increased osteocalcin and vitamin D receptor (VDR) expression in response to 1alpha,25(OH)(2)D(3.) This blockade was shown to be the result of lack of nuclear accumulation of the VDR in response to 1alpha,25(OH)(2)D(3). Although inhibition of proteasomic degradation with MG132 had no effect on the VDR itself in a 30-min time frame, it relieved the blockade by PRL. Analysis of ubiquitinated proteins brought down by immunoprecipitation with anti-VDR showed PRL regulation of a 250-kDa protein-VDR complex. P250 was identified as the breast cancer tumor suppressor gene product, BRCA1, by Western blot of the VDR immunoprecipitate and confirmed by immunoprecipitation with anti-BRCA1 and blotting for the VDR in the absence and presence of PRL. Knockdown of BRCA1 inhibited nuclear translocation of the VDR and the ability of 1alpha,25(OH)(2)D(3) to induce the VDR. This, to our knowledge, is the first demonstration of a role for BRCA1 in nuclear accumulation of a steroid hormone and the first demonstration that PRL has the potential to affect the cell cycle through effects on BRCA1.

Topics: Active Transport, Cell Nucleus; Animals; BRCA1 Protein; Cell Line, Tumor; Cell Nucleus; Cholecalciferol; Genes, Reporter; Osteocalcin; Osteosarcoma; Prolactin; Promoter Regions, Genetic; Proteasome Endopeptidase Complex; Protein Isoforms; Rats; Receptors, Calcitriol; Receptors, Prolactin; Ubiquitin

A proteomic analysis of proteins bound to the osteocalcin OSE2 sequence of the mouse osteocalcin promoter identified TRPS1 as a regulator of osteocalcin transcription. Mutations in the TRPS1 gene are responsible for human tricho-rhino-phalangeal syndrome, which is characterized by skeletal and craniofacial abnormalities. TRPS1 has been shown to bind regulatory promoter sequences containing GATA consensus binding sites and to repress transcription of genes involved in chondrocyte differentiation. Here we show that TRPS1 can directly bind the osteocalcin promoter in the presence or absence of Runx2. TRPS1 binds through a GATA binding sequence in the proximal promoter of the osteocalcin gene. The GATA binding site is conserved in mice, humans, and rats, although its location and orientation are not. Mutation of the mouse or human GATA binding sequence abrogates binding of TRPS1 to the osteocalcin promoter. We show that TRPS1 is expressed in osteosarcoma cells and upon induction of osteoblast differentiation in primary mouse bone marrow stromal cells and that TRPS1 regulates the expression of osteocalcin in both cell types. The expression of TRPS1 modulates mineralized bone matrix formation in differentiating osteoblast cells. These data suggest a role for TRPS1 in osteoblast differentiation, in addition to its previously described role in chondrogenesis.

Topics: Androgens; Animals; Binding Sites; Blotting, Western; Bone Density Conservation Agents; Bone Marrow; Bone Neoplasms; Calcification, Physiologic; Cell Differentiation; Cells, Cultured; Cholecalciferol; Chromatin Immunoprecipitation; Chromatography, Liquid; Core Binding Factor Alpha 1 Subunit; DNA Primers; DNA-Binding Proteins; DNA, Neoplasm; Enzyme-Linked Immunosorbent Assay; GATA Transcription Factors; Gene Expression Regulation; Humans; Immunoprecipitation; Luciferases; Mice; Osteoblasts; Osteocalcin; Osteosarcoma; Promoter Regions, Genetic; Rats; Regulatory Sequences, Nucleic Acid; Repressor Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Stromal Cells; Transcription Factors; Transfection

Circulating 1 alpha,25-dihydroxyvitamin D(3) (1,25D) derives from renal conversion of 25-hydroxyvitamin D(3) (25D), by the 25D 1 alpha-hydroxylase (CYP27B1). Blood 25D levels, but not 1,25D levels, are the best indicator of vitamin D status and predict fracture risk in the elderly. We examined the extent to which osteoblasts can metabolize 25D. Well-characterized human primary osteoblasts and osteosarcoma (OS) cell lines were examined for the expression and regulation of genes associated with vitamin D metabolism, using real-time PCR. Primary osteoblasts and OS cell lines were found to express CYP27B1 mRNA and secreted detectable 1,25D in response to 25D. Of the OS cell lines tested, HOS expressed the most CYP27B1 mRNA and secreted the highest levels of 1,25D. All osteoblastic cells examined up-regulated expression of the catabolic regulator of 1,25D, the 25-hydroxyvitamin D-24-hydroxylase (CYP24), when incubated with either 1,25D or 25D. Exposure to physiological levels of 25D resulted in up-regulated transcription of the 1,25D responsive genes, osteocalcin (OCN), osteopontin (OPN) and RANKL. Specific knockdown of CYP27B1 in HOS cells using siRNA resulted in up to 80% reduction in both 1,25D secretion and the transcription of OCN and CYP24, strongly implying that the 25D effect in osteoblasts is preceded by conversion to 1,25D. Incubation with 25D, like 1,25D, inhibited primary osteoblast proliferation and promoted in vitro mineralization. Finally, we detected expression by osteoblasts of receptors for vitamin D binding protein (DBP), cubilin and megalin, suggesting that osteoblasts are able to internalize DBP-25D complexes in vivo. Together, our results suggest that autocrine, and perhaps paracrine, pathways of vitamin D(3) metabolism may regulate key osteoblast functions independently of circulating, kidney derived 1,25D. Our results are therefore consistent with the reported benefits of maintaining a healthy vitamin D status in the elderly to reduce the risk of fractures.

Topics: 25-Hydroxyvitamin D3 1-alpha-Hydroxylase; Calcifediol; Calcitriol; Cell Line, Tumor; Cells, Cultured; Cholecalciferol; Gene Expression Regulation; Humans; Low Density Lipoprotein Receptor-Related Protein-2; Osteoblasts; Osteocalcin; Osteopontin; Osteosarcoma; Polymerase Chain Reaction; RANK Ligand; Receptors, Cell Surface; RNA, Messenger; RNA, Small Interfering; Steroid Hydroxylases; Transcription, Genetic; Vitamin D3 24-Hydroxylase

Previous studies have suggested that 1,25(OH)2D3, the active form of vitamin D3, may increase the survival of bone-forming osteoblasts through an inhibition of apoptosis. On the other hand, vitamin D3 has also been shown to trigger apoptosis in human cancer cells, including osteosarcoma-derived cell lines. In the present study, we show that 1,25(OH)2D3 induces a time- and dose-dependent loss of cell viability in the rat osteosarcoma cell line, UMR-106, and the human osteosarcoma cell line, TE-85. We were unable, however, to detect nuclear condensation, phosphatidylserine externalization, or other typical signs of apoptosis in this model. Moreover, 1,25(OH)2D3 failed to protect against apoptosis induced by serum starvation or incubation with the protein kinase inhibitor, staurosporine. These in vitro findings are thus at variance with several previous reports in the literature and suggest that induction of or protection against apoptosis of bone-derived cells may not be a primary function of vitamin D3.

Topics: Animals; Apoptosis; Cell Line, Tumor; Cholecalciferol; DNA Fragmentation; Humans; Osteosarcoma; Rats; Serum; Staurosporine

Since our original demonstration of the metabolism of 1alpha,25(OH)2D3 into 1alpha,25(OH)2-3-epi-D3 in human keratinocytes, there have been several reports indicating that epimerization of the 3 hydroxyl group of vitamin D compounds is a common metabolic process. Recent studies reported the metabolism of 25OHD3 and 24(R),25(OH)2D3 into their respective C-3 epimers, indicating that the presence of 1alpha hydroxyl group is not necessary for the 3-epimerization of vitamin D compounds. To determine whether the presence of a 25 hydroxyl group is required for 3-epimerization of vitamin D compounds, we investigated the metabolism of 1alphaOHD3, a non-25 hydroxylated vitamin D compound, in rat osteosarcoma cells (ROS 17/2.8). We noted metabolism of 1alphaOHD3 into a less polar metabolite which was unequivocally identified as 1alphaOH-3-epi-D3 using the techniques of HPLC, GC/MS, and 1H-NMR analysis. We also identified 1alphaOH-3-epi-D3 as a circulating metabolite in rats treated with pharmacological concentrations of 1alphaOHD3. Thus, these results indicated that the presence of a 25 hydroxyl group is not required for 3-epimerization of vitamin D compounds. Furthermore, the results from the same studies also provided evidence to indicate that 1alphaOH-3-epi-D3, like 1alphaOHD3, is hydroxylated at C-25. We then evaluated the biological activities of 1alphaOH-3-epi-D3. Treatment of normal rats every other day for 7 days with 2.5 nmol/kg of 1alphaOH-3-epi-D3 did not raise serum calcium, while the same dose of 1alphaOHD3 increased serum calcium by 3.39 +/- 0.52 mg/dl. Interestingly, in the same rats which received 1alphaOH-3-epi-D3 we also noted a reduction in circulating PTH levels by 65 +/- 7%. This ability of 1alphaOH-3-epi-D3 to suppress PTH levels in normal rats without altering serum calcium was further tested in rats with reduced renal function. The results indicated that the ED50 of 1alphaOH-3-epi-D3 for suppression of PTH was only slightly higher than that of 1alpha,25(OH)2D3, but that the threshold dose of the development of hypercalcemia (total serum Ca > 10.5 mg/dl) was nearly 80 times higher. These findings indicate that 1alphaOH-3-epi-D3 is a highly selective vitamin D analog with tremendous potential for treatment of secondary hyperparathyroidism in chronic renal failure patients.

Topics: Animals; Calcium; Cell Line, Tumor; Cholecalciferol; Female; Humans; Male; Molecular Structure; Osteosarcoma; Parathyroid Hormone; Rats; Rats, Sprague-Dawley; Uremia

The remodeling of chromatin is required for tissue-specific gene activation to permit interactions of transcription factors and coregulators with their cognate elements. Here, we investigate the chromatin-mediated mechanisms by which the bone-specific osteocalcin (OC) gene is transcriptionally activated during cessation of cell growth in ROS 17/2.8 osteosarcoma cells and during normal osteoblast differentiation. Acetylation of histones H3 and H4 at the OC gene promoter was assayed during the proliferative and postproliferative stages of cell growth by using chromatin immunoprecipitation assays with antibodies that recognize different acetylated forms of histones H3 or H4. The results show that the promoter and coding regions of the OC gene contain very low levels of acetylated histones H3 and H4 during the proliferative period of osteoblast differentiation when the OC gene is inactive. Active expression of the OC gene in mature osteoblasts and confluent ROS 17/2.8 cells is functionally linked to preferential acetylation of histone H4 and, to a lesser extent, to acetylation of histone H3. Histone acetylation at the loci for RUNX2 (CBFA1), alkaline phosphatase, bone sialoprotein, osteopontin, and the cell growth regulator p21, which are expressed throughout osteoblast differentiation, is not altered postproliferatively. We conclude that acetylation of histones H3 and H4 is functionally coupled to the chromatin remodeling events that mediate the developmental induction of OC gene transcription in bone cells.

Topics: Acetylation; Alkaline Phosphatase; Amino Acid Sequence; Animals; Bone Neoplasms; Cell Differentiation; Cells, Cultured; Cholecalciferol; Chromatin; Core Binding Factor Alpha 1 Subunit; Cyclin-Dependent Kinase Inhibitor p21; Cyclins; Gene Expression Regulation; Histones; Integrin-Binding Sialoprotein; Molecular Sequence Data; Neoplasm Proteins; Osteoblasts; Osteocalcin; Osteopontin; Osteosarcoma; Promoter Regions, Genetic; Rats; Sialoglycoproteins; Transcription Factors; Transcription, Genetic; Transcriptional Activation

Osteocalcin (OC) is a small (6 kDa) polypeptide whose expression was thought to be limited to mature osteoblasts. The discovery of OC expression in prostate cancer specimens led us to study the regulation of OC gene in androgen-independent metastatic human prostate PC3 cells. An 800-bp human OC (hOC) promoter-luciferase construct exhibited strong basal and vitamin D-induced activity in OC-positive human prostate and osteosarcoma cell lines. Through deletion analysis of the hOC promoter, the functional hierarchy of the cis-acting elements, OSE1, OSE2, and AP-1/VDRE, was established in PC3 cells (OSE1 > AP-1/VDRE > OSE2). By juxtaposing dimers of these 3 cis-elements, we produced a minimal hOC promoter capable of displaying high tissue specific activity in prostate cancer cells. Our study demonstrated three groups of transcription factors, Runx2, JunD/Fra-2, and Sp1, responsible for the high hOC promoter activity in PC3 cells by binding to the OSE2, AP-1/VDRE, and OSE1 elements, respectively. Among the three groups of transcription factors, the expression levels of Runx2 and Fra-2 are higher in the OC-positive PC3 cells and osteoblasts, compared with the OC-negative LNCaP cells. Interestingly, unlike the mouse OC promoter, the OSE1 site in hOC promoter is regulated by members of Sp1 family instead of the osteoblast-specific factor Osf1. The molecular basis for androgen-independent prostate cancer cells behaving like mature osteoblasts may be explained by the interplay and coordination of these transcription factors under the tight regulation of autocrine and paracrine mediators.

Topics: Base Sequence; Blotting, Western; Cell Nucleus; Cholecalciferol; Core Binding Factor Alpha 1 Subunit; Dimerization; Electrophoresis, Polyacrylamide Gel; Gene Deletion; Humans; Luciferases; Male; Models, Biological; Molecular Sequence Data; Neoplasm Proteins; Osteocalcin; Osteosarcoma; Plasmids; Promoter Regions, Genetic; Prostatic Neoplasms; Proto-Oncogene Proteins c-jun; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Homology, Nucleic Acid; Sp1 Transcription Factor; Transcription Factors; Transcription, Genetic; Transfection; Tumor Cells, Cultured

The level of osteocalcin in serum is lower in lead-intoxicated children than in their normal counterparts. To explain this clinical observation, we investigated the mechanism of action of lead on vitamin D3-dependent osteocalcin production. Lead (5-20 microM) blocked the stimulating effects of vitamin D3 on osteocalcin production in cultured rat osteosarcoma cells (ROS 17/2.8). It is often suggested that activation of protein kinase C (PKC) is a critical mediator of the toxic actions of lead. Treatment of ROS cells with Gö6976, an inhibitor of PKC alpha and beta isozymes, produced similar effects as lead on vitamin D3-dependent osteocalcin production, while activation of PKC by phorbol-12-myristate-13-acetate (TPA) did not reverse or mimic this effect of lead. Thus activation of PKC is not consistent with the actions of lead on vitamin D3-dependent osteocalcin production. Measurement of PKC enzyme activity showed that 10 microM lead treatment does not activate or inhibit the activity of PKC in ROS cells. Western blot analysis indicated that lead treatment does not translocate PKC alpha, beta, or zeta from cytosol to membrane. Therefore, we concluded that PKC does not mediate the cellular toxicity of lead on vitamin D3-dependent osteocalcin production.

Topics: Alkaline Phosphatase; Animals; Blotting, Western; Bone and Bones; Bone Development; Bone Neoplasms; Cell Fractionation; Cholecalciferol; Electrophoresis, Polyacrylamide Gel; Lead; Osteoblasts; Osteocalcin; Osteosarcoma; Parathyroid Hormone; Protein Kinase C; Rats; Receptors, Glucocorticoid; Tumor Cells, Cultured

We previously demonstrated a correlation between wild-type p53 expression and appearance of osteoblastic-specific differentiation characteristics, as evidenced by basal osteocalcin gene expression in a mouse osteosarcoma tumor. The study reported here further explored the possibility of p53's having a distinct transcription-activating role in bone differentiation, in addition to its proposed role in G1 arrest and apoptosis. ROS17/2.3 osteoblastic osteosarcoma cells were stably transfected with a plasmid containing wild-type p53 binding sequences fused to the chloramphenicol acetyltransferase reporter gene. These cells were used to determine the transactivating role of p53 in regulation of osteocalcin gene expression. We chose two conditions under which osteocalcin expression is known to be upregulated: exposure of osteoblastic cells to differentiation-promoting medium and to vitamin D3. Exposure of the transfected cells to differentiation-promoting medium produced an increase in p53 transactivating activity correlating with the appearance of osteocalcin expression after about 1 wk. Vitamin D3 treatment resulted in upregulation of osteocalcin activity without a corresponding change in p53 transactivation activity or expression. In separate experiments, we tested whether changes in osteocalcin expression accompanied changes in p53 activity under conditions of downregulation of cell proliferation mediated by inhibition of DNA synthesis. Hydroxyurea treatment was used to inhibit DNA synthesis and produce growth arrest in osteoblastic cells. Inhibition of osteoblast cell proliferation was associated with a fourfold increase in p53 transactivating activity and a transient increase in osteocalcin steady-state expression. These results demonstrated a close relationship between p53 and osteocalcin and suggested a regulatory role for wild-type p53 in the control of basal osteocalcin gene expression in osteoblasts.

Topics: Animals; Biomarkers; Cell Cycle; Cell Differentiation; Chloramphenicol O-Acetyltransferase; Cholecalciferol; Genes, p53; Hydroxyurea; Osteoblasts; Osteocalcin; Osteosarcoma; Rats; Transcription, Genetic; Tumor Cells, Cultured; Up-Regulation

Vitamin D3: 1-alpha, 25(OH)2D3 (calcitriol), 22-oxa-1,25(OH)2D3 (OCT), cholecalciferol (vitamin D3), and retinoids: all-trans retinoic acid (ATRA) and 9-cis retinoic acid, induced morphological changes in POS canine osteosarcoma cells into elongated, spindle or fibroblast like-shaped cells, and apoptotic like cell death characterized by cell shrinkage, condensation and margination of the nucleus for all drugs at 10(-6)M-10(-9)M after 72 to 120 hr culture. Apoptosis as shown by DNA laddering was induced at 48 hr by all drugs at 10(-6)M, 10(-7)M at 96 hr, 10(-8)M and 10(-9)M at 120 hr respectively. These vitamins are suggested to adjunct antineoplastic agents in canine osteosarcoma therapy by induction of apoptosis.

Topics: Animals; Apoptosis; Bone Neoplasms; Calcitriol; Cholecalciferol; Dog Diseases; Dogs; Electrophoresis, Agar Gel; Osteosarcoma; Retinoids; Tumor Cells, Cultured

Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGF-beta) superfamily and are crucial factors in the process of bone formation. Despite knowledge on their wide distribution and expression, however, there is very little information on the biological factors that affect gene transcription of these osteoinductive agents. To investigate this aspect of BMP gene regulation we have studied the effect of a number of factors known to affect osteogenic cells. Northern analysis showed modulation of the expression of BMP-2 and BMP-4 mRNAs in two human osteosarcoma cell lines, MG63 and Saos-2, by prostaglandin E2 (PGE2), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interferon-alpha (IFN-alpha), retinoic acid and 1,25(OH)2 vitamin D3. mRNA expressions of the normally used "housekeeping genes", glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and beta-actin, were found to be susceptible to influence by some of the factors used. Hence, an oligo(dT)15-18 probe was used to reliably estimate the relative quantities of mRNA present for normalization of data. In general, all factors down-regulated mRNA expressions of BMP-2 and BMP-4 in MG63 cells. IL-6 completely abolished detectable expression of BMP-2 mRNA, which was also greatly reduced by IL-1beta, retinoic acid and 1,25(OH)2 vitamin D3. PGE2 had similar influences on BMP-2 and BMP-4 expressions, showing reductions to approximately 60% of normal. In Saos-2 cells only 1,25(OH)2 vitamin D3 had any great effect on BMP-2 expression, which was down-regulated to approximately 60% of control values. BMP-4 was down-regulated by IFN-alpha (approximately 60%) and IL-1beta (approximately 20%). We conclude that BMPs are subject to regulation by a variety of factors and that this is dependent on the stage of the cell in the osteogenic lineage. Furthermore, the use of GAPDH and beta-actin genes as "housekeeping genes" in expression-modulation studies must be treated with care.

Topics: Actins; Blotting, Northern; Bone Morphogenetic Protein 2; Bone Morphogenetic Protein 4; Bone Morphogenetic Proteins; Cholecalciferol; Dinoprostone; Gene Expression Regulation; Glyceraldehyde-3-Phosphate Dehydrogenases; Humans; Interferon-alpha; Interleukin-1; Interleukin-6; Oligonucleotide Probes; Osteosarcoma; RNA, Messenger; Transcription, Genetic; Transforming Growth Factor beta; Tretinoin; Tumor Cells, Cultured

3,5,3'-Tri-iodothyronine (T3), 1 alpha,25(OH)2-vitamin D3 (D3) and retinoids activate related nuclear receptors which interact by heterodimerisation to regulate gene expression. Actions of each hormone are discrete and may be specified by changes in the relative concentrations of their receptors (T3R, vitamin D receptor (VDR), retinoic acid receptor (RAR), retinoid X receptor (RXR)). T3, D3 and retinoids are essential for skeletal development and maintenance and we have previously shown complex interactions amongst their signalling pathways in osteosarcoma cells. In these studies we demonstrate that similar T3R, VDR, RAR and RXR proteins are co-expressed in both osteoblast lineage cell primary cultures and osteosarcoma cells by Western blotting. We investigated whether hormone interactions in bone result from changes in receptor stoichiometry. Cells were treated with combinations of T3, D3, 9-cis retinoic acid (9-cis RA) and all-trans retinoic acid (RA) that are known from previous studies to produce complex cell specific responses. No alteration in expression of any receptor protein was seen in response to any hormone combination in three phenotypically distinct osteosarcoma cell lines. Thus, in contrast to studies of overexpressed receptors in vitro, changes in the physiological concentrations of endogenous T3R, VDR, RAR and RXR do not specify discrete hormone actions in osteoblastic cells. Other unidentified factors are likely to modulate hormone action in these bone cells.

Topics: Animals; Blotting, Western; Cells, Cultured; Cholecalciferol; Osteoblasts; Osteosarcoma; Rats; Rats, Wistar; Receptors, Calcitriol; Receptors, Retinoic Acid; Receptors, Thyroid Hormone; Signal Transduction; Tretinoin; Triiodothyronine; Tumor Cells, Cultured

The principal cause of death from most forms of cancer is metastatic disease. Cancer cells appear to grow quickly out of the control of the normal host regulatory mechanisms. Many factors contribute to this unrestrained proliferation, including increased metalloproteinase activity causing degradation of the extracellular matrix surrounding cancer cells, angiogenesis permitting easy access of the cells to the bloodstream and decrease or loss of programmed cell death, or apoptosis, an important mechanism for removal of abnormal or senescent cells. Treatment modalities targeted towards arresting cancer cell proliferation and spread are needed to improve the survival of patients with cancer. Vitamin D3, 1,25-dihydroxychole-calciferol D3, has been shown to induce apoptosis in the human breast cancer cell line, MCF-7. We have studied the effects of three concentrations of vitamin D3 on the human breast cancer cell line, MDA-MB-435, the human prostate cancer cell line, LNCaP, and a human osteosarcoma cell line, U20S. We report here that vitamin D3 strikingly inhibits cell proliferation and induces apoptosis in all three cell lines.

Topics: Adenocarcinoma; Apoptosis; Breast Neoplasms; Cell Division; Cholecalciferol; Dose-Response Relationship, Drug; Female; Humans; Male; Neoplasm Proteins; Osteosarcoma; Prostatic Neoplasms; Tumor Cells, Cultured

24-Oxa-vitamin D3 (24-oxa-D3) and 24-oxa-1 alpha-hydroxyvitamin D3 were designed as possible inhibitors of the vitamin D metabolic activation pathway. Their affinity for the vitamin D receptor (from pig intestine) and human vitamin binding protein were reduced, and their potency to induce cell differentiation of human leukemia cells (HL 60) or osteosarcoma cells (MG 63) was markedly reduced (19% and 3%, respectively), in comparison with calcitriol. A single or chronic injection of 24-oxa-D3 had no biological activity, whereas chronic administration of 24-oxa-1 alpha-hydroxy-D3 showed weak agonist activity in rachitic chicks. When the 24-oxa-D3 was given prior to a single injection of vitamin D3, lower values of serum calcium (64% of the value obtained in vitamin D-treated animals), osteocalcin (52%), 25-(OH)D3 (45%) and duodenal calbindin-D 28K (9.4%) were found. When given chronically in a 100-fold more excess no clear antagonistic effects were observed. 24-Oxa-D3 is thus a new metabolic weak antagonist of vitamin D3, but adding a hydroxyl group at C-1 creates a weak agonist.

Topics: Animals; Calcitriol; Calcium; Cell Differentiation; Chickens; Cholecalciferol; Humans; Leukemia, Promyelocytic, Acute; Osteosarcoma; Receptors, Calcitriol; Swine; Tumor Cells, Cultured; Vitamin D; Vitamin D-Binding Protein

It has been previously reported that several human cancer cell lines possess specific receptors for 1,25-dihydroxyvitamin D3. In the present study, the concentration of the 1 alpha,25 dihydroxyvitamin D3 receptors has been determined in four human osteosarcoma cell lines--MG63, OST, MNNG-HOS, and KHOS-NP, and we report the effect of 1 alpha, 25 dihydroxyvitamin D3 on these cells. The concentration of 1 alpha, 25 dihydroxyvitamin D3 receptors in MG63, OST, MNNG-HOS and KHOS-NP was 31.1, 12.1, 5.9 and 3.0 fmol/mg of cytosol protein, respectively. These cell lines were classified into two groups according to the concentration of the receptors. The two receptor-rich cell lines were MG63 and OST, and the receptor-poor cell lines were MNNG-HOS and KHOS-NP. In a colony-forming assay, 1 alpha, 25 dihydroxyvitamin D3 (10(-8)M, 10(-9)M) was found to significantly suppress the growth of the receptor-rich cell lines (p < 0.01), but did not suppress that of the receptor-poor cell lines. In an antitumor assay, athymic mice received a transplantation of tumor cells and were treated with 2.5 nmol/kg of 1 alpha hydroxyvitamin D3. Then the relative mean weight of the tumor was measured (MG63 was, however, not transplantable into athymic mice.) As a result, 1 alpha hydroxyvitamin D3 was found to have significantly suppressed the relative mean tumor weight of OST and MNNG-HOS compared with a control group (p < 0.05), but did not suppress that of KHOS-NP. Histologically, 1 alpha hydroxyvitamin D3 induced marked chondrogenetic differentiation in OST alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Bone Neoplasms; Cell Differentiation; Cell Division; Cholecalciferol; Female; Humans; Mice; Mice, Inbred BALB C; Osteosarcoma; Receptors, Calcitriol; Tumor Cells, Cultured

Although numerous studies have shown potent antiproliferative and differentiation-inducing effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and its analogs on cells not directly related to bone metabolism, only few reports focussed on the effects of these analogs on bone. We compared the action of several recently developed analogs with that of 1,25-(OH)2D3 on human (MG-63) and rat (ROS 17/2.8) osteoblast-like cells and on in vitro bone resorption. In MG-63 cells the analogs EB1089 and KH1060 were about 166,000 and 14,000 times more potent than 1,25-(OH)2D3 in stimulating type I procollagen and 100 and 6,000 times more potent in stimulating osteocalcin production, respectively. Also in ROS 17/2.8 cells EB1089 and KH1060 were most potent in inducing osteocalcin synthesis. In vitro bone resorption was 2.3 and 17.5 times more potently stimulated by EB1089 and KH1060, respectively. In MG-63 cells, 1,25-(OH)2D3 and the analogs inhibited cell proliferation, whereas both 1,25-(OH)2D3 and the analogs stimulated the growth of ROS 17/2.8 cells. Differences in potency could neither be explained by affinity for the vitamin D receptor nor by a differential involvement of protein kinase C in the action of the analogs. Together, these data show that also in bone the analogs EB1089 and KH1060 are more potent than 1,25-(OH)2D3 but that the potency of the analogs compared to 1,25-(OH)2D3 is dependent on the biological response. On the basis of these observations it can be concluded that the reported reduced calcemic effect in vivo is not the result of a decreased responsiveness of bone to these analogs. Lastly, in view of eventual clinical application of 1,25-(OH)2D3-analogs, the observed stimulation of in vitro bone resorption and growth of an osteosarcoma cell line warrant in vivo studies to further examine these effects.

Topics: Animals; Antineoplastic Agents; Binding, Competitive; Bone Resorption; Calcitriol; Cell Division; Cells, Cultured; Cholecalciferol; Enzyme Inhibitors; Glyceryl Ethers; Humans; In Vitro Techniques; Osteoblasts; Osteocalcin; Osteosarcoma; Procollagen; Protein Kinase C; Rats; Receptors, Calcitriol; Structure-Activity Relationship; Tumor Cells, Cultured

1 alpha, 25-Dihydroxyvitamin D3 (1,25-D3) rapidly (within seconds) shifts the threshold for activation of inward calcium currents to more negative and physiological potentials. To determine whether the opening of calcium channels in bone cells is mediated by the cytosolic 1,25-dihydroxyvitamin D3 receptor (VDR), several natural metabolites 1,25-D3, 25-hydroxyvitamin D3, and 24R,25-dihydroxyvitamin D3 and synthetic analogs 25-hydroxy-16,23E-diene D3 (HO), 25-hydroxy-23-yne D3 (Y), and 1 alpha, 25-dihydroxy-16-ene-23-yne-26,27-F6 D3 (EO) were tested on dihydropyridine-sensitive inward barium currents. In order to probe the structural specificity at the 1 position of the steroid for stimulation of barium currents, we used several synthetic 1-(1'-hydroxyethyl) (NP, ON, NN, OP) and 1-(2'-hydroxyethyl)-25-hydroxyvitamin D3 analogs (14w-1 alpha and 14-w1 beta). Using the perforated patch-clamp technique, we found that the naturally occurring vitamin D3 analogs gave nearly the same rank order potency for stimulation of barium currents as their affinity for VDR with 1,25-D3 being the most potent analog. Using the synthetic analogs which have minimal affinity for VDR, we found that the compounds without 1-OH group but with additional double bonds in positions 16 and 23 or with a triple bond in position 23 retained high affinity for calcium channel activation. Furthermore, 1-hydroxyethyl-25-hydroxyvitamin D3R isomers at the 1' position had greater affinity than the S isomers at this position, and a beta oriented 2'-hydroxyethyl group gave the homolog greater affinity than did the alpha-oriented 2'-hydroxyethyl group. The fact that these synthetic analogs cause rapid effects on calcium channels and show pharmacological specificity different from the binding to the cytosolic vitamin D3 receptor suggests that calcium influx is mediated by a distinct signal transduction pathway. The high and physiological affinity of 1,25-D3 (50 pM) suggests that it is a biological regulator of calcium channels.

Topics: Animals; Barium; Calcium Channels; Cholecalciferol; Osteosarcoma; Rats; Receptors, Calcitriol; Tumor Cells, Cultured

T3 is required for normal skeletal development, but its cellular targets in bone are unknown. T3 regulates target gene transcription via a specific nuclear receptor (T3R), which can heterodimerize with 9-cis-retinoic acid, 1 alpha, 25-dihydroxyvitamin D3, or retinoic acid receptors to modify T3 responsiveness. Serum-free cultures were developed to investigate hormone interactions in three osteosarcoma cell lines, ROS25/1, UMR106, and ROS17/2.8, that express fibroblast-like, preosteoblast, and mature osteoblast phenotypes. ROS25/1 expressed T3R alpha 1, but only low levels of T3R beta 1, whereas UMR106 and ROS17/2.8 cells expressed both receptor proteins. All cells expressed c-erb-A alpha 2 protein and equal levels of 1 alpha,25-dihydroxyvitamin D3 receptor, 9-cis-retinoic acid receptor, and retinoic acid receptor messenger RNAs. Endogenous T3R activity and the effects of D3 and 9-cis-RA on T3 responsiveness were determined in transfections using reporter genes containing T3 response elements from rat malic enzyme or alpha-myosin heavy chain genes. Cell-specific T3 responses were associated with differing patterns of T3R gene expression and stages of osteoblast phenotype expression. A change in T3R beta 1 gene expression during osteoblast phenotype differentiation may modify T3 action in developing bone.

Topics: Animals; Base Sequence; Bone Neoplasms; Cholecalciferol; Molecular Probes; Molecular Sequence Data; Osteoblasts; Osteosarcoma; Phenotype; Rats; Receptors, Thyroid Hormone; Retinoids; Signal Transduction; Triiodothyronine; Tumor Cells, Cultured

Vitamin D3 and its hydroxylated metabolites are normally in thermal equilibrium with their previtamin D isomers. To evaluate the biologic activity of 1 alpha, 25-dihydroxyprevitamin D3, we synthesized 19-nor analogs of 1 alpha, 25-dihydroxy(pre)vitamin D3 because the absence of a C19 methylene group prevents the isomerization of these analogs. The affinity of 1 alpha, 25-(OH)2D3-19-nor-D3 for the intestinal vitamin D receptor and plasma vitamin D binding protein was mildly decreased [30 and 20% of the affinity of 1 alpha, 25-(OH)2D3, respectively], but the affinity of 1 alpha, 25-(OH)2-19-nor-previtamin D3 was only 1 and 6% of that of 1 alpha, 25-(OH)2D3 for the receptor and DBP, respectively. The in vitro effects on human promyeloid leukemia (HL-60 cell) differentiation and osteocalcin secretion by human osteosarcoma (MG-63) cells by 1 alpha, 25-(OH)2-19-nor-D3 were nearly identical to those of 1 alpha-25-(OH)2D3, whereas 19-nor-previtamin D3 showed poor activity (2%). The in vivo calcemic effects of both analogs, studied in vitamin D-deficient chicks treated for 10 consecutive days with the analogs, showed no activity of the previtamin D3 analog and reduced calcemic effects (< or = 10%) of 1 alpha, 25-(OH)2-19-nor-D3. We conclude that the previtamin D form of 1 alpha, 25-(OH)2D3 has lost most of its biologic activity in vitro and in vivo.

Topics: Animals; Calbindins; Calcitriol; Calcium; Cell Differentiation; Cell Division; Chickens; Cholecalciferol; Duodenum; Humans; Hydroxylation; Intestinal Mucosa; Monocytes; Osteocalcin; Osteosarcoma; Receptors, Calcitriol; S100 Calcium Binding Protein G; Swine; Tumor Cells, Cultured

Gallium nitrate, a group IIIa metal salt, has been found to be clinically effective for the treatment of accelerated bone resorption in cancer-related hypercalcemia and Paget's disease. Here we report the effects of gallium nitrate on osteocalcin mRNA and protein levels on the rat osteoblast-like cell line ROS 17/2.8. Gallium nitrate reduced both constitutive and vitamin D3-stimulated osteocalcin protein levels in culture medium by one-half and osteocalcin mRNA levels to one-third to one-tenth of control. Gallium nitrate also inhibited vitamin D3 stimulation of osteocalcin and osteopontin mRNA levels but did not affect constitutive osteopontin mRNA levels. Among several different metals examined, gallium was unique in its ability to reduce osteocalcin mRNA levels without decreasing levels of other mRNAs synthesized by ROS 17/2.8 cells. The effects of gallium nitrate on osteocalcin mRNA and protein synthesis mimic those seen when ROS 17/2.8 cells are exposed to transforming growth factor beta 1 (TGF beta 1); however, TGF-beta 1 was not detected in gallium nitrate-treated ROS 17/2.8 cell media. Use of the RNA polymerase II inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole demonstrated that gallium nitrate did not alter the stability of osteocalcin mRNA. Transient transfection assays using the rat osteocalcin promoter linked to the bacterial reporter gene chloramphenicol acetyltransferase indicated that gallium nitrate blocked reporter gene expression stimulated by the osteocalcin promoter. This is the first reported effect of gallium nitrate on isolated osteoblast cells.

Topics: Animals; Antineoplastic Agents; Blotting, Northern; Carrier Proteins; Cholecalciferol; Gallium; Osteoblasts; Osteocalcin; Osteopontin; Osteosarcoma; Rats; RNA, Messenger; Sialoglycoproteins; Transforming Growth Factor beta; Tumor Cells, Cultured

Previous work has shown that 25-hydroxyvitamin D3 (25-OH-D3) and 1 alpha, 25-dihydroxyvitamin D3 (1,25-(OH)2D3) may be metabolized in the mammalian kidney through a side chain oxidation pathway resulting in C23-C24 cleavage, yielding 24,25,26,27-tetranor-23-OH-D3. In the present study, we have used UMR-106 clonal osteoblast cells to demonstrate that products of the side chain oxidation pathway are produced by an osteoblast-like cell. Cells cultured on microcarrier beads and incubated in the presence of pharmacological levels of substrate (1.4 microM, either 25-OH-D3 or 1,25-(OH)2D3) produced sufficient quantities of metabolite to allow identification through mass spectrometry. In addition, putative metabolites were identified through comigration with authentic standards on three high pressure liquid chromatography systems, chemical modification by NaBH4 and periodate, and UV spectral characterization. The pathway was undetectable unless the cells had been exposed to 1,25-(OH)2D3 prior to incubation with substrate. We have shown that 1,25-(OH)2D3 induces the 24-hydroxylase and perhaps also the other enzymes of this pathway in the bone cell. Although we used pharmacological concentrations of substrate to demonstrate the existence of the side chain oxidation pathway in bone cells, physiological levels of 25-OH-D3 or 1,25-(OH)2D3 were also metabolized through the pathway, at least as far as the penultimate product. We speculate that the side chain oxidation pathway may be ubiquitous among vitamin D target tissues.

Topics: Cholecalciferol; Chromatography, High Pressure Liquid; Deuterium; Mass Spectrometry; Osteoblasts; Osteosarcoma; Tumor Cells, Cultured

The effect of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on phospholipid metabolism was examined in clonal rat osteogenic sarcoma cells, UMR 106, of osteoblastic phenotype. Treatment of UMR 106 cells with 10(-8)M 1,25-(OH)2D3 for 48 h caused an increase in [14C]serine incorporation into phosphatidylserine (PS) and a decrease in [3H]ethanolamine, [3H]linositol, and [14C]choline incorporation into phosphatidylethanolamine (PE), phosphatidylinositol, and phosphatidylcholine, respectively; the decrease in [3H]ethanolamine incorporation into PE was the largest. The total contents of phospholipids were similarly affected by 10(-8)M 1,25-(OH)2D3 treatment, suggesting that the effects of 1,25-(OH)2D3 are due largely to alterations in the synthesis of these phospholipids. The effects of 1,25-(OH)2D3 were evident at 10(-10) M 1,25-(OH)2D3, and 10(-8)M 1,25-(OH)2D3 caused a maximal stimulation of [14C]PS synthesis (167% of control) and a maximal reduction in the [3H]PE synthesis (41% of control). The [14C]PS/[3H]PE ratio increased gradually and reached a maximum after 70 h of treatment with 10(-8)M 1,25-(OH)2D3. When the cells were cultured in calcium-free medium containing 0.5 mM EGTA or when 5 microM cycloheximide was added to the medium, the effect of 1,25-(OH)2D3 on phospholipid metabolism was almost completely inhibited. Neither 25-hydroxyvitamin D3 nor 24,25-dihydroxyvitamin D3 caused significant changes in phospholipid metabolism. These results suggest that 1,25-(OH)2D3 alters phospholipid metabolism by enhancing PS synthesis through a calcium-dependent stimulation of the base exchange reaction of serine with other phospholipids and that the effect of 1,25-(OH)2D3 requires the synthesis of new proteins. Because PS is thought to be important for apatite formation and bone mineralization by binding calcium and phosphate to form calcium-PS-phosphate complexes, the present data suggest that 1,25-(OH)2D3 may stimulate bone mineralization by a direct effect on osteoblasts, stimulating PS synthesis.

Topics: Animals; Calcitriol; Calcium; Cell Line; Cholecalciferol; Cycloheximide; Dose-Response Relationship, Drug; Osteoblasts; Osteosarcoma; Phospholipids; Rats; Time Factors

The effect of 1,25-dihydroxyvitamin D3 on adenylate cyclase responsiveness was studied in the clonal osteogenic sarcoma cell line, UMR 106-06, which responds to several bone active hormones. 1,25-dihydroxyvitamin D3 treatment had no consistent effect on basal formation of cyclic AMP in intact cells, but the responses to parathyroid hormone, isoproterenol, prostaglandin E2, salmon calcitonin and the plant diterpene, forskolin, were all attenuated, by up to 90%. The effect of 1,25-dihydroxyvitamin D3 was dose-dependent, with half-maximal effectiveness at 0.1 nM, and required 48 h treatment of cells before it became apparent. The relative potencies of other vitamin D3 compounds correlated closely with their relative affinities for the 1,25-dihydroxyvitamin D3 receptor and their biological activities in other systems. 1,25-dihydroxyvitamin D3 treatment had no effect on the kinetics of labelled calcitonin binding to UMR 106-06 cells. Furthermore, the fact that such a range of hormones was affected made a receptor mediated mechanism unlikely. Nucleotide stimulatory (Ns) unit activity was assayed after 1,25-dihydroxyvitamin D3 treatment and found to be unchanged. Islet activating protein, an inhibitor of nucleotide inhibitory unit (Ni) activity, failed to modify the 1,25-dihydroxyvitamin D3 effect. Thus the effect of 1,25-dihydroxyvitamin D3 appeared to be exerted beyond hormone receptor and nucleotide regulatory components of the adenylate cyclase complex. It is concluded that 1,25-dihydroxyvitamin D3 attenuates adenylate cyclase response to hormones by a direct or indirect action on the catalytic component of adenylate cyclase.

Topics: Adenylate Cyclase Toxin; Animals; Calcitonin; Calcitriol; Cell Line; Cholecalciferol; Cyclic AMP; Dose-Response Relationship, Drug; Hormones; Nucleotides; Osteosarcoma; Parathyroid Hormone; Peptide Fragments; Pertussis Toxin; Rats; Teriparatide; Time Factors; Virulence Factors, Bordetella

Topics: Calcitriol; Cells, Cultured; Cholecalciferol; Dihydroxycholecalciferols; Humans; Hydroxycholecalciferols; Kinetics; Osteosarcoma; Radioligand Assay; Receptors, Drug; Tritium

A female pet wooly monkey with metabolic bone disease initially presented with a proliferating bony mass in the left humerus which had many features of osteosarcoma. At necropsy, parathyroid hyperplasia, osteoclastic resorption, proliferative osteoid deposition in the calvarium and cortex of long bones, and fibrous proliferation of the marrow indicated the presence of generalized osteodystrophia fibrosa. The dietary history of deficient vitamin D3 and protein and minimal exposure to sunlight supported this diagnosis, as did depressed levels of serum calcium and elevated levels of serum parathyroid hormone, alkaline phosphatase, and acid phosphatase.

Topics: Animals; Bone Neoplasms; Calcium; Cholecalciferol; Diagnosis, Differential; Female; Fibrous Dysplasia of Bone; Haplorhini; Humerus; Monkey Diseases; Osteosarcoma; Vitamin D Deficiency