|Budget Amount *help
¥6,700,000 (Direct Cost : ¥6,700,000)
Fiscal Year 1994 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1993 : ¥4,600,000 (Direct Cost : ¥4,600,000)
The mechanisim of proliferation and differentiation of human megakaryocytic cells has been investigated.
1. Tyrosine phosphorylation of c-Kit receptor, Vav, MAP kinase was observed in a megakaryoblastic leukemia cell line, CNK,by the stimulation of SCF.When GM-CSF (granulocyte-macrophage colony-stimulating factor) was added to CMK cells, tyrosine phosporylation of Jak2 and MAP kinase was revealed.
2. The role of Evi-1 on megakaryocytic cells was investigated. Evi-1 m-RNA was expressed in CMK and Meg-J cells. However, expression of Evi-1 m-RNA did not increase after stimulation of TPA (12-0-tetradecanoyl phorbol-13-acetate), IL-3 (interleukin-3), IL-6 or IL-11. Myb m-RNA was expressed in CMK cells, however, additon of antisense oligonucleotide of myb to CMK cells chould not suppress the proliferation, suggesting that myb has no role for the proliferation of CMK cells.
3. When Meg-J cells were cultured in the presence of K252a, a protein kinase C inhibitor, the ploidy was dramatically increased. This assay system may be use ful for studying the mechanism of polyploidization of megakaryocytic cells.
4. Enhancement of CD41 expression of CMK cells by TPA was ablogated by Herbimycin A,a tyrosine kinase inhibitor, indicating that TPA-induced CD41 expression was mediated by tyrosine kinases.
5. It has been shown that IL-11 is an autocrine growth factor for human megakaryoblastic leukemia cells. Therefore, we next ivestigated whether IL-11 act as an autocrine growth factor for normal human mekakaryocytic cells. Human megakaryocytes obtained by normal bone marrow cells did not express IL-11 mRNA,indicating that IL-11 is not a autocrine growth factor in normal megakaryocyotopoiesis.