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Summary. The alterations in gene expression associated with 1,25(OH) 2 D 3 -induced differentiation of HL-60 cells were studied in order to identify potential targets for further investigation of the genetic basis of acute myeloid leukaemia. Atlas human haematology filters, including 406 genes (Clontech), were used to study gene expression in response to 1,25(OH) 2 D 3 (concentration, 5 · 10 )8 mol/l) for 24 and 72 h. Compared with untreated cells, expression differences were found in 43 genes. Downregulated genes at both time-points were: IL2RA, CMYC, NPM, DEK, AF4, FLI1, HTLF, MNDA, BCR, IKAROS, BPI and NFAT4. Upregulated genes at both time-points were IL1B, CD14 and MCL1. CD55, CD58, IRF2, CREB1, ATF4, RAC1, TIAR, KIAA0053, BAT2, BTK, RCK, EV12B and EDN were downregulated at 24 h, while SPI1, MKK3, BTG1 and IL8were upregulated. At 72 h the upregulated genes were IL1RA, IL2RG, CXCR4, SCYA1, SCYA3, SCYA4, SCYA5, SCYA22, ANX2, CD83 and UPAR. cDNA array results were confirmed on randomly selected genes using quantitative real-time polymerase chain reaction for three upregulated (CXCR4, IL1B and CD14) and three downregulated (DEK, AF4 and FLI1) genes. Gene expression analysis after differentiation induction may provide a tool to study the roles of DEK, AF4 and FLI1 in cell proliferation and differentiation. To demonstrate the genes that initiate differentiation, sequential gene expression analysis has to be performed during the first 24 h of the differentiation process.

Summary:The major obstacle to successful bone marrow transplantation (BMT) is graft-versus-host disease (GVHD). Vitamin D analogs have shown their efficacy in solid organ transplantation. The purpose of this study was to investigate the suitability of a novel vitamin D analog, MC1288, in the prevention of acute GVHD in a rat BMT model. Allogeneic BMT were performed from Lewis to BN rats (n = 18). The animals were divided into four groups: an untreated control group, MC1288, cyclosporin A (CsA), and MC1288 + CsA-treated groups. Rats were harvested for histology and immunohistochemistry on day 20 after BMT. Histological changes for GVHD in liver, skin, and spleen were thickening associated with transplant arteriosclerosis, or chronic rejection, in a rat aortic transplant model. 7 In addition to their immunosuppressive effects, we and others have shown that vitamin D analogs have anti-leukemic effects both in vitro and on de novo patient samples. 8 The major obstacle in using natural vitamin D or its early analogs for treatment has been hypercalcemia before therapeutic concentrations could be reached. 9,10 This problem has now been solved with novel analogs with lesser calcemic activity. 7,8 MC 1288 is a 20-epi-1,25(OH) 2 D 3 , differing from 1,25(OH) 2 D 3 by altered stereochemistry of the methyl group at carbon 20 in the side chain of the molecule (Figure 1). We have previously shown that MC1288 is well tolerated in rats in vivo. It did not induce hypercalcemia during the first month of treatment although in 3 months, the serum calcium level increased by 30%. 7 The purpose of this study was to investigate the suitability of MC1288 in the prevention of acute graft-versushost disease (GVHD) in a rat bone marrow transplantation (BMT) model. Here, we studied the effects of MC1288 on the clinical course and histological manifestations of acute GVHD after allogeneic BMT. Materials and methods Bone marrow transplantation (BMT)Allogeneic bone marrow transplantations were performed using adult Brown Norway (BN; RT1 l ) rats as recipients and 10-week-old Lewis (LEW; RT1 n ) rats as bone marrow cell donors. The cells were collected by flushing the femurs with saline. The recipient animals were irradiated with 960 rad (Varian Climac 600c, 6 MV photon irradiation, distance 120 cm, field size 40 × 40 cm 2 ) prior to BMT. After 24 h, 60-80 × 10 6 mononuclear bone marrow cells from LEW rats were injected into BN recipients.

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