Abstract
The binding of urokinase-type plasminogen activator (u-PA) to its receptor (u-PA-R) is required for morphological and functional maturation during monocyte differentiation of the promyelocytic leukaemia line HL-60. This paper reports that monocyte differentiation of HL-60 cells induced by 1,25 dihydroxyvitamin D2 (vitamin D2) results in a marked increase in expression of u-PA and u-PA-R. This increase in u-PA expression is of greater magnitude than is observed after culture with interferon-gamma (IFNγ), another potent inducer of monocytic differentiation. Dimethyl sulphoxide (DMSO), an agent that induces granulocytic differentiation, also increased expression of u-PA. However, culture with the granulocyte-inducing all-trans retinoic acid (RA) did not induce an increase in surface expression of u-PA or u-PA-R. The vitamin D2-induced increase in cell-surface u-PA was not coincident with an increase in steady-state levels of u-PA mRNA, suggesting that intracellular stores of this protein, translational or post-translational mechanisms of regulation, or some other regulatory mechanism may be responsible for the increase in u-PA during differentiation. To ascertain an association between the increased expression of cell-surface u-PA and reduced proliferation that accompanies differentiation, the effect of u-PA on cellular proliferation of HL-60 cells was measured. Both pro-u-PA (whole molecule) and fragments of u-PA that retained receptor-binding capability caused a marked inhibition of HL-60 proliferation in the absence of vitamin D2. A modified form of u-PA that retains receptor binding capability but lacks a fucose in the receptor binding domain (defucosylated u-PA) did not diminish HL-60 cell proliferation. These findings suggest that u-PA may regulate myeloid cell proliferation, a finding that may be relevant to the design of experimental treatment protocols for patients with myeloid leukaemia.
Original language | English (US) |
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Pages (from-to) | 445-453 |
Number of pages | 9 |
Journal | Blood Coagulation and Fibrinolysis |
Volume | 5 |
Issue number | 4 |
State | Published - Jan 1 1994 |
Keywords
- myeloid leukaemia
- proliferation
- urokinase
- urokinase receptor
- vitamin D2
ASJC Scopus subject areas
- Hematology