Overexpression of plasminogen activator inhibitor 2 in human melanoma cells inhibits spontaneous metastasis in scid/scid mice.

Abstract

A metastatic human melanoma cell line that produces urokinase-type plasminogen activator was stably transfected with cDNA encoding human plasminogen activator inhibitor 2 (PAI-2). Transfected clones expressed PAI-2 at levels two to nine times higher than both the parental cell line and mock transfectants, as detected by ELISA ofcell lysates and conditioned medium.The clone with the highest PAI-2 expression exhibited complete inhibition of soluble and cell-surface-bound plasminogen activator activity. (3). Plasmin, the active form of plasminogen, degrades ECM components such as fibronectin, laminin, and fibrin and also mediates activation of certain metalloproteinases. Two distinct activators of plasminogen are known, urokinase-type PA (uPA) and tissue-type PA, which are tightly controlled by specific PA inhibitors (PAls) namely, PAI-1 and PAI-2. The fine-tuned balance between PA and PAI activities is responsible for controlled pericellular proteolysis and appears to be lacking in tumor cells, resulting in continuous, uncontrolled proteolytic breakdown of the ECM by these cells, leading to tissue invasion and ultimately metastasis. Restoration of this balance by inhibition of tumor cell-derived PA activity should therefore result in suppression of invasion and metastasis.Thus, inhibition of uPA by specific inhibitors or anticatalytic antibodies resulted in inhibition of tumor cell invasion and metastasis. PAI-1 and PAI-2 were shown to inhibit ECM degradation by human tumor cell lines in vitro (4-6). Anti-uPA antibodies inhibited invasion and metastasis of a human squamous carcinoma cell line in chicken embryos (7), localThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.invasion of human tumors grown s.c. in mice (8), and experimental metastasis of murine melanoma cells in mice (9). Overexpression of uPA in poorly metastatic murine melanoma cells (10) or in H-ras-transformed NIH 3T3 fibroblasts (11) enabled these cells to form experimental metastases. Overexpression of enzymatically inactive uPA reduced metastasis of prostate carcinoma cells (12).We previously described the highly metastatic human melanoma cell line M24met (13) that secretes a spectrum of proteolytic enzymes, including type IV collagenases, interstitial collagenase, and uPA (14). In vitro, this cell line degrades interstial and basement membrane matrices with uPAdependent removal of matrix glycoprotein as a prerequisite step preceding metalloproteinase-dependent collagenolysis. Consequently in this model the addition of exogenous recombinant PAI-2 inhibits dissolution of all matrix components (14). Here, we address the role of PA activity in human melanoma metastasis in severe combined immunodeficient (SCID) mice. We stably transfected our metastatic melanoma cell line with full-length PAI-2 cDNA and analyzed the resulting transfectants for their ability to degrade ECM and to met...

Significance of plasminogen activator inhibitor 2 as a prognostic marker in primary lung cancer: association of decreased plasminogen activator inhibitor 2 with lymph node metastasis

“…Our current study suggests that PAI-2 is deeply involved in tumour growth and tissue degradation. This notion is also supported by other experiments in which transfection of recombinant PAI-2 cDNA to HT-1080 cells or Met 24 cells effectively depressed their metastatic ability (Laug et al, 1993;Mueller et al, 1995). The regulating mechanism of PAI-2 expression still remains unclear.…”

Tumor Cell Plasticity in Uveal Melanoma

“…A metastatic human melanoma cell line that produces urokinase-type plasminogen activator was stably transfected with cDNA encoding human plasminogen activator inhibitor 2 (PAI-2), and PAI-2-transfected cell lines produced significantly fewer or no metastases. 43 The down-regulation of chondroitin sulfate proteoglycan (versican; CSPG1) has been associated previously with melanocytic differentiation. 44 Highly invasive melanoma cells that have generated vasculogenic mimicry patterns have only a limited capacity for invasion and proliferation (Figures 2 and 3).…”

Prevention of Aneurysm Development and Rupture by Local Overexpression of Plasminogen Activator Inhibitor-1

“…A similar approach using PAI-2 overexpression in vivo has been shown to inhibit metastasis, a phenomenon in which extracellular matrix lysis is necessary for the movement of transformed cells in tissues. 47 PAIs form inhibitory complexes with their C-terminus end and the catalytic domain of PAs. 48,49 In addition, inactive t-PA-PAI-1 complexes compete with active t-PA to occupy binding sites on fibrin.…”