Effect of 1,25-(OH)2-vitamin D3 on growth, homologous receptor and c-myc regulation in C3H/10T1/2 cells

Synergistic anti-proliferative effects of vitamin D derivatives and 9-cis retinoic acid in SH-SY5Y human neuroblastoma cells

This study examines the effect of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)], 24,25-dihydroxyvitamin D(3) [24,25(OH)(2)D(3)], two vitamin D analogues (KH 1060 and EB 1089, which are 20-epi-22-oxa and 22,24-diene-analogues, respectively), 9-cis retinoic acid and all-trans retinoic acid on proliferation of SH-SY5Y human neuroblastoma cells, after treatment for 7 days. Cell number did not change when the cells were incubated with 1, 10 or 100 nM 1,25(OH)(2)D(3) or its derivatives, but significantly decreased in the presence of the two retinoids (0.001--10 microM final concentration). A synergistic inhibition was observed, when SH-SY5Y cells were treated combining 0.1 microM 9-cis retinoic acid and 10 nM 1,25(OH)(2)D(3) or 10 nM KH 1060, and 1 microM 9-cis retinoic acid and 10 nM 1,25(OH)(2)D(3) or 10 nM EB 1089. Acetylcholinesterase activity showed a significant increase, in comparison with controls, after treatment of the cells for 7 days with 0.1 or 1 microM 9-cis retinoic acid, alone or combined with 10 nM 1,25(OH)(2)D(3) or 10 nM KH 1060 or 10 nM EB 1089. This increase was synergistic, combining 1 microM 9-cis retinoic acid and 10 nM 1,25(OH)(2)D(3) or EB 1089. The levels of the c-myc encoded protein remarkably decreased after treatment of SH-SY5Y cells for 1, 3, 7 days with 0.1 and 1 microM 9-cis retinoic acid, alone or combined with 10 nM 1,25(OH)(2)D(3) or 10 nM KH 1060 or 10 nM EB 1089. In particular, the association of 1 microM 9-cis retinoic acid and 10 nM 1,25(OH)(2)D(3) or 10 nM EB 1089 resulted in a synergistic c-myc inhibition, in comparison with that obtained in the presence of the retinoid alone. These findings may have therapeutic implications in human neuroblastoma.

1,25-dihydroxyvitamin D3 and agents that increase intracellular adenosine 3',5'-monophosphate synergistically inhibit fibroblast proliferation

Agents that increase intracellular cAMP (cAMP elevating agents) and 1, 25(OH)2D3 inhibit the proliferation of many cell types. We investigated the combined effect of 1,25(OH)2D3 and cAMP elevating agents on exponentially growing mouse 3T3 fibroblasts. The following cAMP elevating agents were used: theophylline and pentoxyfilline, which inhibit cAMP-dependent phosphodiesterase; prostaglandin E2 which activates adenylate cyclase by a receptor-mediated mechanism; forskolin, which directly stimulates adenylate cyclase; and the cell permeable cAMP analogs 8-bromo cAMP and N6 benzoyl cAMP. 1,25(OH)2D3 and cAMP elevating agents were added to exponentially growing fibroblasts cultured in 96-well microtiter plates and cell number was monitored 3-7 d later. 1,25(OH)2D3 and the cAMP elevating agents as single agents inhibited the growth of the 3T3 cells. The combined treatment of the fibroblasts with 1,25(OH)2D3 and the cAMP elevating agents resulted in an antiproliferative effect that was more than additive. The synergistic interaction depended on the dose of 1,25(OH)2D3 and was apparent already at 10(-8) M of the hormone. The specificity of the effect of 1,25(OH)2D3 was demonstrated by the finding that 24,25-dihydroxyvitamin D3, a vitamin D metabolite with low affinity for the vitamin D receptor, did not affect the antiproliferative effect of cAMP elevating agents. From the synergistic interaction between 1,25(OH)2D3 and the cell permeable cAMP analogs, we infer that the site of interaction between the two signaling pathways is distal to the cAMP generating and degrading machinery.

Effects of 1,25-dihydroxyvitamin D3 on transformed C3H/10T1/2 fibroblasts grown as multicellular spheroids

We have previously shown that 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) is able to modulate proliferation of C3H/10T1/2 fibroblasts grown in monolayer cell culture. The aim of this study was to investigate the effects of the hormone in a 3-dimensional culture system, which is considered to better reflect the cellular environment that is found in vivo. Two transformed cell lines of C3H/10T1/2 fibroblasts (C116 and TPA 482) were grown as multicellular spheroids, whereas the nontumorigenic C3H/10T1/2 C18 cells failed to form spheroids. The hormone had no effect on spheroids made of TPA 482 cells but had a biphasic effect on C116 spheroid growth with stimulation at low and inhibition at higher concentrations. In C116 spheroids, 10(-8) M 1,25-(OH)2D3 induced complete arrest of spheroid growth. Light and electron microscopic studies and immunocytochemistry showed that 10(-8) M 1,25-(OH)2D3 induced morphological changes in C116 spheroids, with a marked reduction in expression of fibronectin, laminin and the gap junction protein connexin 43. These effects were followed by a loosening of the spheroid structure, detachment of viable cells, and finally disaggregation of the spheroids. The results of this study, together with the data previously obtained in monolayer cell cultures, indicate that the effects of 1,25-(OH)2D3 may be conditioned by the cellular environment. Therefore, the spheroid model is an interesting tool for investigation of the antineoplastic effect of the hormone.

Biological activity of vitamin D analogues in the skin, with special reference to antipsoriatic mechanisms

Active vitamin D3 modulates epidermal growth, keratinization and inflammation, and various vitamin D3 analogues have been shown to be effective in the treatment of psoriasis. These analogues now provide a useful addition to the therapeutic modalities available for the treatment of psoriasis. Epidermal hyperproliferation, abnormal keratinization and inflammation are the well-established hallmarks of the psoriatic plaque. The aim of this review is to provide an update of information on the cell biological effects of vitamin D3, and the influence of vitamin D analogues on the pathomechanisms of psoriasis.

Effects of 1,25-dihydroxyvitamin D3 and retinoic acid on the proliferation and cell cycle phase distribution of neuroblastoma SK-N-SH cells

The hormone 1,25-(OH)2D3 has been shown to modulate cell proliferation and induce differentiation in several normal and malignant cell lines. In this work, we examined the effect of the hormone on the neuroblastoma SK-N-SH cell line. The steroid did not influence cell growth and cell cycle distribution, while retinoic acid inhibited proliferation and induced an accumulation of the cells in the G0/G1 phase of the cell cycle. 1,25-(OH)2D3 did not alter cell morphology. The activities of the 1-alpha- and 24-hydroxylases were low and not regulated by the hormone. The level of the total 1,25-(OH)2D3 receptor was low. We conclude that the lack of effect of 1,25-(OH)2D3 on the SK-N-SH cell line is related to the low level of the 1,25-(OH)2D3 receptor.

Time-course study of 1,25-(OH)2-vitamin D3 induction of homologous receptor and c-myc in nontransformed and transformed C3H/10T1/2 cell clones

1. We have used 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) to investigate autoregulation of homologous receptor and the control of c-myc mRNA and protein expression in C3H/10T1/2 cells. 2. 10 nM 1,25-(OH)2D3 stimulated 1,25-(OH)2D3 receptor (VDR) synthesis in both non-transformed C3H/10T1/2 Cl 8 and in chemically transformed C3H/10T1/2 Cl 16 cells within 4 hr of treatment. Maximal induction was observed between 8 and 24 hr. 3. Two VDR mRNA transcripts, 2.7 and 4.8 kb, were present in both cell types. There were parallel changes in VDR specific mRNA levels and cellular VDR concentration in the C3H/10T1/2 Cl 8 cells indicating that the increase in receptor concentrations was dependent on de novo mRNA synthesis. 4. The increase in VDR mRNA concentration in the chemically transformed C3H/10T1/2 Cl 16 cells was maximal already at 4 hr, preceding the maximal increase in receptor concentration by 4-6 hr. 5. Analysis of c-myc mRNA levels also showed cell line specificity. 6. The c-myc mRNA level increased 2.1-fold with 10 nM 1,25-(OH)2D3 treatment in C3H/10T1/2 Cl 8 cells after 12 hr while the C3H/10T1/2 Cl 16 cells had maximal c-myc mRNA level after 1 hr. 7. The relative amount of c-myc mRNA remained higher than that of unstimulated controls the next 10-12 hr in C3H/10T1/2 Cl 16 cells. 8. The c-myc protein levels were not affected by 1,25-(OH)2D3 treatment in either cell line as detected by Western blot analysis. 9. Our data suggest that 1,25-(OH)2D3 mediated induction of VDR does not require prior c-myc protein synthesis in the C3H/10T1/2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of 1alpha,25-dihydroxyvitamin D3 receptor in cell extracts with low protein concentration

An unacceptable loss of tritiated 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] to the wall of the reaction tubes constituted an obstacle when examining C3H/10T1/2 Cl 8 cells for 1,25-(OH)2D3 receptor. The loss of tracer in low protein cell extracts could be strongly reduced by incubating the cell extracts in polyethylene tubes and in the presence of inert peptides prepared by digestion of gluten proteins. When incubated in buffer the recovery of tracer increased from 3 to 45% by using polyethylene tubes instead of sodium-glass tubes. However, the presence of a sufficient amount of inert peptides in the buffer significantly increased the recovery of tracer to 89%. This procedure improved the saturation binding analysis of the 1,25-(OH)2D3 receptor in the C3H/10T1/2 Cl 8 cells using the hydroxylapatite assay.

Modulation of cell proliferation and cell cycle, and inhibition of cytokinesis by 1,25-dihydroxyvitamin D3 in C3H/10T1/2 fibroblasts

The growth-modulating effects of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] were studied on three mouse embryo fibroblast cell lines. Concentrations ranging from 0.1 to 100 nM inhibited dose-dependently proliferation in the non-tumorigenic C3H/10T1/2 Cl 8 (10T1/2) and the chemically transformed C3H/10T1/2 Cl 16 (Cl 16) cells. The hormone had a biphasic effect on the transformed cell line C3H/10T1/2 TPA 482 (TPA 482) in which growth was stimulated by low concentrations. Exposure to 10 nM 1,25-(OH)2D3 for 5 days resulted in a 90% growth inhibition of 10T1/2 cells, and the hormone was 10 and 100 times less potent in Cl 16 and TPA 482 cells, respectively. The inhibition of cell replication was fully reversible on removal of the hormone. Treatment of 10T1/2 and Cl 16 cells with 10 nM 1,25-(OH)2D3 reduced the saturation density to 30 and 37% that of controls, respectively, suggesting an enhancement of cell-cell contact mediated growth inhibition. 1,25-(OH)2D3 inhibited cytokinesis in 10T1/2 cells, inducing the formation of binucleated cells. Flow cytometric studies showed that 1,25-(OH)2D3-treated cells accumulated in the Go/G1 phase while the number of cells in S phase decreased. This in vitro model system seems to be useful for studies of the molecular mechanisms of the growth modulating effect of 1,25-(OH)2D3.

Reorganization of the cytoskeleton and morphological changes induced by 1,25-dihydroxyvitamin D3 in C3H/10T1/2 mouse embryo fibroblasts: relation to inhibition of proliferation

The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3) on cell morphology, the cytoskeleton, and fibronectin were studied in three lines of C3H/10T1/2 mouse embryo fibroblasts in which the antiproliferative effect of the hormone had previously been investigated. We showed that 1,25(OH)2D3 induced morphological changes in the nontransformed C3H/10T1/2 Cl 8 cells, which flattened and spread out markedly. Visualization of actin and tubulin by immunocytochemistry disclosed a reorganization of the microfilament and microtubular systems. 1,25(OH)2D3 also induced an increase in cell-surface-associated fibronectin. These changes were only slight in the transformed cell line C3H/10T1/2 Cl 16 and absent in the transformed C3H/10T1/2 TPA 482 cell line. These effects were correlated with the growth inhibition induced by the hormone, and this suggests a possible relationship between the 1,25(OH)2D3-induced alterations of cell shape and of the cytoskeleton and the effects of the hormone on cell proliferation.