TY - JOUR
T1 - Down-regulation of proteolytic activity in 12-O-tetradecanoyl-phorbol-13-acetate-induced K562 leukemia cell cultures
T2 - depletion of active urokinase by excess type 1 plasminogen activator inhibitor
AU - Alitalo, R
AU - Andersson, L C
AU - Tapiovaara, H
AU - Sistonen, L
AU - Vaheri, A
AU - Stephens, R
PY - 1989/7
Y1 - 1989/7
N2 - The human chronic myeloid leukemia cell line K562 acquires several megakaryoblastoid features when cultured in the presence of the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We observed strongly increased secretion of several proteins into the culture media of K562 cells within a few hours of TPA treatment. Two of the major secreted polypeptides were identified by immunoprecipitation from media of metabolically labeled cultures as the tissue inhibitor of metalloproteinases (TIMP) and the type 1 plasminogen activator inhibitor (PAI-1). Maximal amounts of PAI-1 mRNA and secretion of PAI-1 polypeptides were observed after 24 hr of TPA treatment and PAI-1 persisted at elevated levels for several days. The induction of PAI-1 mRNA was dependent on de novo protein synthesis. Uninduced and induced cells secreted urokinase plasminogen activator in its single-chain proenzyme form (pro-u-PA), which was cleaved extracellularly to the active two-chain form as shown by pulse-chase labeling experiments. Upon TPA induction, the secretion of u-PA polypeptides increased severalfold, and there was a transient accumulation of pro-u-PA in the culture medium. However, this did not lead to increased u-PA activity in the cultures, since active u-PA was removed by complex formation with the large excess of coinduced PAI-1. Induction of u-PA mRNA was biphasic: The first peak of about tenfold increase in steady-state u-PA mRNA at 3 hr was followed by a steep decline to the baseline level at 12 hr, and a second, slower accumulation of u-PA mRNA occurred over the next few days. The biphasic accumulation of u-PA mRNA was also reflected in u-PA protein synthesis. We conclude that concerted changes in favor of a nonproteolytic extracellular environment occur in TPA-induced K562 cultures undergoing megakaryoblastoid differentiation. These changes include excessive secretion of TIMP and inhibition of the induced u-PA by the simultaneous accumulation of PAI-1.
AB - The human chronic myeloid leukemia cell line K562 acquires several megakaryoblastoid features when cultured in the presence of the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We observed strongly increased secretion of several proteins into the culture media of K562 cells within a few hours of TPA treatment. Two of the major secreted polypeptides were identified by immunoprecipitation from media of metabolically labeled cultures as the tissue inhibitor of metalloproteinases (TIMP) and the type 1 plasminogen activator inhibitor (PAI-1). Maximal amounts of PAI-1 mRNA and secretion of PAI-1 polypeptides were observed after 24 hr of TPA treatment and PAI-1 persisted at elevated levels for several days. The induction of PAI-1 mRNA was dependent on de novo protein synthesis. Uninduced and induced cells secreted urokinase plasminogen activator in its single-chain proenzyme form (pro-u-PA), which was cleaved extracellularly to the active two-chain form as shown by pulse-chase labeling experiments. Upon TPA induction, the secretion of u-PA polypeptides increased severalfold, and there was a transient accumulation of pro-u-PA in the culture medium. However, this did not lead to increased u-PA activity in the cultures, since active u-PA was removed by complex formation with the large excess of coinduced PAI-1. Induction of u-PA mRNA was biphasic: The first peak of about tenfold increase in steady-state u-PA mRNA at 3 hr was followed by a steep decline to the baseline level at 12 hr, and a second, slower accumulation of u-PA mRNA occurred over the next few days. The biphasic accumulation of u-PA mRNA was also reflected in u-PA protein synthesis. We conclude that concerted changes in favor of a nonproteolytic extracellular environment occur in TPA-induced K562 cultures undergoing megakaryoblastoid differentiation. These changes include excessive secretion of TIMP and inhibition of the induced u-PA by the simultaneous accumulation of PAI-1.
KW - Cell Line
KW - Culture Media
KW - Electrophoresis, Polyacrylamide Gel
KW - Enzyme Inhibitors/analysis
KW - Glycoproteins/analysis
KW - Humans
KW - Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism
KW - Peptide Hydrolases/metabolism
KW - Plasminogen Activators/metabolism
KW - Plasminogen Inactivators
KW - Precipitin Tests
KW - RNA, Messenger
KW - Tetradecanoylphorbol Acetate
KW - Tissue Inhibitor of Metalloproteinases
KW - Tumor Cells, Cultured/metabolism
KW - Urokinase-Type Plasminogen Activator/metabolism
U2 - 10.1002/jcp.1041400115
DO - 10.1002/jcp.1041400115
M3 - Article
C2 - 2500450
SN - 0021-9541
VL - 140
SP - 119
EP - 130
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
IS - 1
ER -