| Co-Investigator(Kenkyū-buntansha) |
NAGAI Masami Kagawa Medical School School of Medicine Associate, 医学部, 助手 (40180450)
KUBOTA Yoshitsugu Kagawa Medical School School Hospital Associate, 医学部附属病院, 助手 (90178054)
IKEDA Kazuma Kagawa Medical School School of Medicine Associate, 医学部, 助手 (50176088)
TANAKA Terukazu Kagawa Medical School School Hospital Assistant Professor, 医学部附属病院, 講師 (20155146)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
It is still controversial how to treat the patients with myelodysplastic syndrome and hypoplastic leukemia. We administrated high dose of 1alpha(OH)D_3 which is converted to 1alpha, 25(OH)_2D_3 (D3) in vivo, and obtained promising clinical effects in the treatment of these types of diseases. The main clinical effects were as follows : 1. a decrease of myeloblasts in the bone marrow, 2. aggregation of heterochromatin of myeloblasts, 3. improvement of pancytopenia in the peripheral blood. The effects were considered to be due to the differentiation of leukemia cells induced by D3 but not due to the cytotoxicity.
HL-60 cells derived from acute promyelocytic leukemia are differentiated into monocyte-macrophages by D3 or phorbol ester (TPA) and into granulocytes by retinoic acid (RA). To elucidate the role of Ca^<2+> in HL-60 cell proliferation and differentiation, we analyzed the effects of diltiazem (Dil),a Ca^<2+> channel blocker, on HL-60 cells. Dil(> 20muM) significantly inhibited the p
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roliferation and [^3H] thymidine incorporation into DNA of HL-60 cells. Dil(> 50muM) enhanced HL-60 cell differentiation induced by D3 or RA, but there was no significant differences between D-cis and L-cis isomers of Dil in the enhancing effects. We investigated changes in cytosolic free Ca^<2+> concentration ( [Ca^<2+>]i) at short term (within 5 min) and long term ( 24-72 hrs ) during the differentiation. A transient increase of [Ca^<2+>]i was observed in HL-60 cells treated with D3 and Dil or TPA, but not with RA. After 24 to 72 hours incubation with D3 or TPA , [Ca^<2+>]i increased significantly but did not with RA. These findings suggest that both short and long term increases in [Ca^<2+>]i play an important role in the induction of HL-60 cell differentiation into the monocyte lineage. There are two major information transduction systems involving Ca^<2+> signals, protein kinase C and calmodulin systems. H-7, a protein kinase C inhibitor, showed remarkable inhibition of the differentiation induced by D3 and moderate suppression of [Ca^<2+>]i. W-7, a calmodulin inhibitor, did not show any inhibiting effects on the differentiation or the increase in [Ca^<2+>]i. These findings suggest that the activation of protein kinase C plays an important role in HL-60 cell differentiation induced by D3.
We also analyzed changes of the amount of lipocortins, another type of Ca^<2+> binding proteins, during HL-60 cell differentiation. The amount of lipocortins in HL-60 cells increased after the differentiation into the monocyte and granulocyte lineags. This finding suggests that lipocortins also participate in the induced differentiation. But the role of lipocortins in the differentiation must be investigated in detail and elucidated in future. Less
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