Regulation of 92-kD gelatinase release in HL-60 leukemia cells

Matrix metalloproteinase 9 (MMP-9), also known as 92-kD type IV
collagenase/gelatinase, is believed to play a critical role in
tumor invasion and metastasis. Here, we report that MMP-9 was
constitutively released from the human promyelocytic cell line
HL-60 as determined by zymographic analysis. Tumor necrosis
factor-alpha (TNF-alpha) enhanced the enzyme release threefold to
fourfold and the protein kinase C (PKC) activator and
differentiation inducer 12-O-tetradecanoylphorbol-13- acetate (TPA)
eightfold to ninefold. Gelatinase induction by TNF-alpha and TPA
was inhibited by actinomycin D or cycloheximide, indicating that de
novo protein synthesis was required. Neutralizing monoclonal
antibodies to TNF-alpha (anti-TNF-alpha) decreased the basal MMP-9
release of these cells. In addition, these antibodies also
significantly interfered with the TPA-induced enzyme release.
Agents that inhibit TNF-alpha expression in HL-60 cells, such as
pentoxifylline and dexamethasone, completely abrogated both the
constitutive and TPA-evoked MMP-9 release. Diethyldithiocarbamate,
which is known to stimulate TNF-alpha production in HL-60 cells,
exerted a positive effect on MMP-9 release in untreated cells but
was inhibitory in TPA-treated HL-60 cells. The PKC inhibitor
staurosporine at low concentrations (100 ng/mL) caused a
significant augmentation of MMP-9 release in untreated cultures
that was blocked by the addition of anti-TNF-alpha. High
concentrations (2 mumol/L) of staurosporine completely abolished
the extracellular enzyme activity both in untreated and
TPA-stimulated cells. These results suggest, that TNF- alpha is
required for basal and PKC-mediated MMP-9 release in HL-60 leukemia
cells. Thus, MMP-9 secretion may be regulated by TNF-alpha not only
in a paracrine but also in an autocrine fashion. This may
potentiate the matrix degradative capacity of immature leukemic
cells in the processes of bone marrow egress and the evasion of
these cells into peripheral tissue.