Effects of cellular transformation on expression of plasminogen activator inhibitors 1 and 2. Evidence for independent regulation.
Expression of plasminogen activators (PA) has been reported to be associated with invasive tumor growth and increased metastatic ability. In order to delineate changes in PA and PA inhibitor (PAI) expression that accompany cellular transformation, we studied oncogene-containing variants of the Rat-1 cell line. We report here that transfection of the oncogenes v-src, erbB, c-myc, v-myc, N-myc, and EJras into these cells does not result in detectable PA activity in conditioned media or cell extracts. In addition, Northern blot analysis fails to demonstrate urokinase mRNA in Rat-1 cells or transfectants. Moreover, cells transformed by EJras and v-src but not other oncogenes secrete an active placental-type PAI, PAI-2. Using inducible EJras constructs, we find that increased PAI-2 gene expression is detectable within 6-12 h after treatment with the inducing agent. Peak expression of PAI-2 mRNA is increased 10-15-fold over base line, and high levels are maintained for at least 72 h. In contrast to the results with PAI-2, secretion of endothelial-type PAI-1 into conditioned media is sharply down-regulated by several oncogenes. Thus, we have found that PAI-1 and PAI-2 are independently regulated in transformed variants of Rat-1 cells. The specific induction of PAI-2 in cells transformed by oncogenic ras and src suggests that this protease inhibitor may have a previously unsuspected role in malignancy.
Cohen
R L
RL
Cancer Research Institute, University of California, San Francisco 94143.
Niclas
J
J
Lee
W M
WM
Wun
T C
TC
Crowley
C W
CW
Levinson
A D
AD
Sadler
J E
JE
Shuman
M A
MA
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D015342:DNA Probes; D003907:Dexamethasone / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation / Q000187:drug effects; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D009857:Oncogenes; D010960:Plasminogen Activators / Q000235:genetics / Q000378:metabolism; D015849:Plasminogen Inactivators; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D010959:Tissue Plasminogen Activator / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology; D017967:Zinc Compounds
D002712:Chlorides; D015342:DNA Probes; D006023:Glycoproteins; D015849:Plasminogen Inactivators; D012333:RNA, Messenger; D017967:Zinc Compounds; D003907:Dexamethasone; C016837:zinc chloride; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator; D015032:Zinc