Modulation of cell differentiation and tumor promotion by vitamin D compounds

Abstracts from the Calcified Tissues Workshop tion 350nm, emmision 460nm) that are known to be present in tissues, undergoing peroxidation. Tissue slices, chondrocytes plasma membranes and matrix vesicles were extracted choloroform-methanol and the malondialdehyde content of each extract determined by reacting the lipid with thiobarbituric acid. The concentration of thiobarbituric acid reactive substances was greatest in the calcifying cartilage and in matrix vesicle preparations. Lower concentrations of malondialdehyde were seen in the premineralized cartilage and in chondrocyte membranes The results of this study suggest that products of oxygen radicals metabolism accumulate in the growth cartilage and that generation of oxygen metabolites may play a role in vesicle biogenesis. MODULATION OF CELL DIFFERENTIATION AND TUMOR PROMOTION BY VITAMIN D COMPOUNDS T. Suds,’ T. Kurok? ‘Department of Biochemistry, School of Dentistry, Showa University, Tokyo, and ‘Department of Cancer Cell Research, Institute of Medical Sbence, University of Tokyo, Tokyo, Japan In 1981, we reported that lc~,25(OH),D, stimulates differentiation of myeloid leukemia cells of mice (Ml) and humans (HL-60) into the cells of the monocyte-macrophage lineage (PNAS, USA 78: 4990, 1981; BBRC 102: 937, 1981). Since then, we have extended this original observation to other types of cells. la,25(OH)2D3 promoted fusion of mouse alveolar macrophages forming multinucleated giant cells with bone-resorbing activity by a direct mechanism and also by a spleen cell-mediated indirect mechanism (PNAS, USA 80: 5583, 1983). Unlike la,25(OH)*D,, bacterial lipopolysaccharides (LPS) did not induce fusion of alveolar macrophages, but the two compounds similarly activated alveolar macrophages, as measured by glucose consumption and induction of cytotoxicity against tumor cells (PNAS, USA 81: 7112, 1984). All of these results suggest that the differentiating action of la,25(OH),D, is closely related not only to the formation of multinucleated osteoclasts, but also to the modulating action of the vitamin in immune response. The differentiating action of la,25(OH),D, was found to occur not only in vitro, but also in vivo. Administration of 1~~,25(0H)~D~ or 1a(OH)D, markedly prolonged survival time of nude mice inoculated with MI cells (PNAS, USA 80: 201, 1983). Furthermore, topical application of 1~1,25(0H)~D~ to mouse skin inhibited the TPA-induced ornithine decarboxylase (ODC) activity (Cancer Res. 44: 1387, 1984) and also the chemically induced papilloma formation, especially in the Stage II of promotion (Cancer Res. 45: 5426, 1985). More recently, Morimoto et al. reported that both oral administration of la(OH)D, and topical application of la,25(OH)2D3 cure strikingly the skin lesions of patients with persistent psoriasis (Calc. Tissue Int., in press). Recent findings in our laboratory and other laboratories on modulation by la,25-(OH),D, of cell differentiation and tumor promotion will be reviewed. A DECREASED RESPONSE TO 1,25(OH),D, OF MONONUCLEAR CELLS FROM NEWBORN INFANTS R. Koren, A. Ravid, C. Rotem, J. Amir, S.H. Reisner, U.A. Liberman, A. Novogrodsky

Metabolic Disease Unit and the Rogoff Med. Res. Inst. Beilinson Medical Center, Petah-Tikva, Israel T lymphocytes acquire receptors for 1,25(OH),D upon mitogenic stimulation. The mitogen-induced proliferation is partially inhibited by physiological concentrations of 1,25(OH),D,. We found that lymphocytes from patients with hereditary end organ resistance to 1,25(OH)2D are insensitive to the hormone action. Delayed bone mineralization with or without the clinical syndrome of rickets is a common finding in very low birth weight infants fed routine formulas. The defect in calcium absorption exists despite normal or elevated serum levels of 1,25(OH),D,, suggesting a partial end organ resistance to 1,25(OH),D3. We assessed the response to 1,25(OH),D, of activated mononuclear cells obtained from cord blood of term and preterm infants and from adult peripheral blood. We observed that the inhibitory effect of 1,25(OH)*D, on cell proliferation was significantly less (34 ? 8%) in mononuclear cells obtained from the cord (independently of gestational age) as compared to adult mononuclear cells (66 4 5%, p < 0.001). The concentration of 1,25(OH),D, necessary to obtain half maximal response was the same for both cell populations (-lO-ioM). However, the number of high affinity binding sites for 1,25(OH),D, in activated mononuclear cells from cord blood was higher (1800 sites/cell) than in cells from adult blood (700 sites/cell). A possible conclusion from these findings is that the coupling between the receptors for 1,25(OH),D, and the biological response in neonates is less efficient than that in the adult. Alternatively, this difference may reflect a reduced susceptibility of the immature immune system to the regulatory action of 1,25(OH),D.

THE ROLE OF 24,25(OH)*D3 RAT KIDNEY

IN THE MATURATION

OF

S. Somjen, Y. Weisman,* E. Berger, A. Harell, A.M. Kaye,** I. Binderman Hard Tissues Unit and *Vitamin Research Laboratory, lchilov Hospital, Tel-Aviv, and **Dept. of Hormone Research, Weizmann Institute, Rehovot, Israel Recently, we have demonstrated that during postnatal development of rat kidney, responsiveness to 24,25(OH),D, occurs from the 6th to the 28th day, while responsiveness to 1,25(OH),D, begins on the 21 st day and continues at least through day 52 (1). In the present study, we have investigated the influence of 24,25(OH),D3 on the development of responsiveness to 1,25(OH),D, in kidney cell cultures Cells from 6-, 21- and 35-day old rat kidneys were isolated by enzymic treatment, seeded in 35 mm culture dishes at 3 x lo5 cells/dish, and grown in MEM medium containing 10% FCS. From day 1 of culture, 12 nM of either 24,25(OH),D,, or 1,25(OH),D, or 10 ~liml 20% ethanol in saline (vehicle) were added to the medium daily, for one week. Two days later, the responsiveness to either hormone was measured by stimulation of CK-BB activity and [3H]-thymidine incorporation into DNA. Chronic treatment with either vehicle or 1 ,25(OH),D3 did not change the pattern of responsiveness to either hormone. However, chronic treatment with 24,25(OH),D, increased the responsiveness to 24,25(OH),D, in cell cultures made from 6-day old kidneys, but not in call cultures from 21-day or 35-day old kidneys. More unexpectedly, treatment with