1-alpha-24-dihydroxyvitamin-d3 and Osteosarcoma

We compared the separate effects of 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and its analog, 1alpha,25-dihydroxy-16ene,23yne-vitamin D3 (1alpha25(OH)2-16ene,23yne-D3), as well as their interactions with 17-beta estradiol (E2) in our human osteosarcoma SaOS-2 cell models representing two stages of differentiation, the SaOS+DEX and SaOS-DEX cells. SaOS+DEX cells have been previously shown to express higher PTH-stimulated adenylate cyclase (PTH-AC) and basal alkaline phosphatase (ALP) activities compared with SaOS-DEX cells. ALP: In SaOS+DEX cells, 0.1 nmol/L analog, but not 1alpha,25(OH)2D3, increased ALP activity 1.7-fold (p < 0.05). Instead, 1 nmol/L 1alpha,25(OH)2D3 increased ALP 1.4-fold (p < 0.05). In these cells, E2 enhanced 1alpha,25(OH)2D3-stimulated ALP activity (ANOVA, F = 51.22, p <0.0001), while inhibiting the effect of the analog. [3H]-Thymidine uptake: In SaOS+DEX cells, 1alpha,25(OH)2D3 had biphasic effects (ANOVA, F = 13.08, p < 0.0001), which were not altered by E2. In contrast, the analog was stimulatory only with E2 (ANOVA, F = 3.59, p < 0.025). Osteocalcin (OC): 1alpha,25(OH)2D3 and its analog stimulated OC production in SaOS-DEX cells with smaller effects in SaOS+DEX cells. In SaOS-DEX cells, E2 enhanced the effect of 1alpha,25(OH)2D3, but not that of the analog. PTH-AC: In SaOS-DEX cells, 100 nmol/L analog inhibited PTH-AC activities by 50% (p < 0.01), whereas 1alpha,25(OH)2D3 had little effect. In SaOS+DEX cells, both compounds inhibited PTH-AC approximately 35%. E2 inhibited the effect of the analog in SaOS-DEX cells, but enhanced the effects of both compounds in SaOS+DEX cells. These results show that the analog 1alpha,25(OH)2-16ene,23yne-D3 was effective in regulating osteoblastic function; its effects were modulated by E2 and dependent upon the stage of osteoblast differentiation.

Topics: Adenylyl Cyclases; Alkaline Phosphatase; Calcitriol; Cell Differentiation; Dihydroxycholecalciferols; Estradiol; Humans; Osteoblasts; Osteocalcin; Osteosarcoma; Parathyroid Hormone; Thymidine; Tumor Cells, Cultured

The effects of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), 1 alpha-hydroxyvitamin D3 (1 alpha(OH)D3), and dexamethasone on colony formation of Dunn osteosarcoma cells (TA 102 cells) were investigated. Concentrations of 1 alpha,25(OH)2D3, 1 alpha(OH)D3, and dexamethasone at which they exerted 50% reduction of the total area of TA 102 colony formation were 9 X 10(-9) M, 9 X 10(-8) M, and 5 X 10(-6) M, respectively. Effects of anticancer drugs on TA 102 cells were also investigated and concentrations needed for 50% growth inhibition (50% inhibitory concentration values) of cis-platinum, mitomycin C (MMC), methotrexate (MTX), and Adriamycin (ADR) against TA 102 cells were calculated to be 0.07 microgram/ml, 0.0008 microgram/ml, 0.0008 microgram/ml, and 0.0005 microgram/ml, respectively. The simultaneous treatment of TA 102 cells with 10(-8) M of 1 alpha,25(OH)2D3 and anticancer drugs significantly enhanced the respective inhibitory effects on colony formation. In this treatment, the IC50 value of MMC was calculated to be 6.4 X 10(-6) micrograms/ml, which was 1/160 of the expected IC50 value of MMC (8 X 10(-4) micrograms/ml). Similar synergistic effects were observed when the cells were treated with 1 alpha,25(OH)2D3 and low concentrations of cis-platinum, MTX, or ADR.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cells, Cultured; Cricetinae; Dihydroxycholecalciferols; Dose-Response Relationship, Drug; Drug Synergism; Mice; Osteosarcoma; Rats; Tumor Cells, Cultured