Growth and Dissemination of Lewis Lung Carcinoma in Plasminogen-Deficient Mice

Deficiency of plasminogen activator inhibitor-2 results in accelerated tumor growth

BACKGROUND

Upregulation of the plasminogen activation system, including urokinase plasminogen activator (uPA), has been observed in many malignancies, suggesting that co-opting the PA system is a common method by which tumor cells accomplish extracellular matrix proteolysis. PAI-2, a serine protease inhibitor, produced from the SERPINB2 gene, inhibits circulating and extracellular matrix-tethered uPA. Decreased SERPINB2 expression has been associated with increased tumor invasiveness and metastasis for several types of cancer. PAI-2 deficiency has not been reported in humans and PAI-2-deficient (SerpinB2-/- ) mice exhibit no apparent abnormalities.

OBJECTIVES

We investigated the role of PAI-2 deficiency on tumor growth and metastasis.

METHODS

To explore the long-term impact of PAI-2 deficiency, a cohort of SerpinB2-/- mice were aged to >18 months, with spontaneous malignancies observed in 4/9 animals, all of apparently vascular origin. To further investigate the role of PAI-2 deficiency in malignancy, SerpinB2-/- and wild-type control mice were injected with either B16 melanoma or Lewis lung carcinoma tumor cells, with markedly accelerated tumor growth observed in SerpinB2-/- mice for both cell lines. To determine the relative contributions of PAI-2 from hematopoietic or nonhematopoietically derived sources, bone marrow transplants between wild-type C57BL/6J and SerpinB2-/- mice were performed.

RESULTS AND CONCLUSIONS

Our results suggest that PAI-2 deficiency increases susceptibility to spontaneous tumorigenesis in the mouse, and demonstrate that SerpinB2 expression derived from a nonhematopoietic compartment is a key host factor in the regulation of tumor growth in both the B16 melanoma and Lewis lung carcinoma models.

Inhibition of invasion, angiogenesis, tumor growth, and metastasis by adenovirus-mediated transfer of antisense uPAR and MMP-9 in non-small cell lung cancer cells

Lung cancer is currently the leading cause of cancer deaths in the United States. Conventional therapeutic treatments, including surgery, chemotherapy, and radiation therapy, have achieved only limited success. The overexpression of proteases, such as urokinase-type plasminogen activator (uPA), its receptor (uPAR), and matrix metalloproteinases (MMP), is correlated with the progression of lung cancer. In the present study, we used a replication-deficient adenovirus capable of expressing antisense uPAR and antisense MMP-9 transcripts to simultaneously down-regulate uPAR and MMP-9 in H1299 cells. Ad-uPAR-MMP-9 infection of H1299 cells resulted in a dose- and time-dependent decrease of uPAR protein levels and MMP-9 activity as determined by Western blotting and gelatin zymography, respectively. Corresponding immunohistochemical analysis also showed that Ad-uPAR-MMP-9 infection inhibited uPAR and MMP-9 expression. As shown by Boyden chamber assay, Ad-uPAR-MMP-9 infection significantly decreased the invasive capacity of H1299 cells compared with mock and Ad-CMV (empty vector)-infected cells in vitro. Furthermore, Ad-uPAR-MMP-9 infection inhibited capillary-like structure formation in H1299 cells cocultured with endothelial cells in a dose-dependent manner compared with mock- and Ad-CMV-infected cells. Ad-uPAR-MMP-9 injection caused the regression of s.c. induced tumors after s.c. injection with H1299 lung cancer cells and inhibited lung metastasis in the metastatic model with A549 cells. These data suggest that Ad-uPAR-MMP-9 shows its antitumor activity against both established and early phases of lung cancer metastases by causing the destruction of the tumor vasculature. In summary, adenovirus-mediated inhibition of uPA-uPAR interaction and MMP-9 on the cell surface may be a promising anti-invasion and antimetastatic strategy for cancer gene therapy.

Suppression of tumor development and metastasis formation in mice lacking the S100A4(mts1) gene

The S100A4(mts1) protein stimulates metastatic spread of tumor cells. An elevated expression of S100A4 is associated with poor prognosis in many human cancers. Dynamics of tumor development were studied in S100A4-deficient mice using grafts of CSML100, highly metastatic mouse mammary carcinoma cells. A significant delay in tumor uptake and decreased tumor incidences were observed in S100A4(-/-) mice compared with the wild-type controls. Moreover, tumors developed in S100A4(-/-) mice never metastasize. Immunohistochemical analyses of these tumors revealed reduced vascularity and abnormal distribution of host-derived stroma cells. Coinjection of CSML100 cells with immortalized S100A4(+/+) fibroblasts partially restored the dynamics of tumor development and the ability to form metastasis. These fibroblasts were characterized by an enhanced motility and invasiveness in comparison with S100A4(-/-) fibroblasts, as well as by the ability to release S100A4 into the tumor environment. Taken together, our results point to a determinative role of host-derived stroma cells expressing S100A4 in tumor progression and metastasis.

Expression of Chicken Ovalbumin Upstream Promoter-Transcription Factor II Enhances Invasiveness of Human Lung Carcinoma Cells

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) plays an essential role in angiogenesis and development. It is differentially expressed in tumor cell lines, but its role in carcinogenesis is largely unknown. We demonstrate here that noninvasive human lung cancer cells become invasive when COUP-TFII was expressed. The expression of extracellular matrix degrading proteinases, such as matrix metalloproteinase 2 and urokinase-type plasminogen activator, was up-regulated in these cells. This finding was confirmed by transduction of different human lung cancer cell lines with COUP-TFII protein and also by using antisense expression. We observed disorganization of actin filaments and focal adhesion kinase phosphorylation in COUP-TFII-transfected human lung cancer cells in addition to the increase in extracellular metalloproteinase activity. These results suggest that COUP-TFII may be considered as a new target for anticancer therapies.

Plasminogen promotes sarcoma growth and suppresses the accumulation of tumor-infiltrating macrophages

The specific functions of plasminogen, stromal plasminogen activator, stromal plasminogen activator receptor, and stromal plasminogen activator inhibitor in the progression of the murine soft tissue sarcoma, T241 were investigated. Negation of plasminogen to the tumor blunted the orthotopic growth of the sarcoma in syngeneic mice. The reduced tumor growth was associated with a dramatic increase in tumor-infiltrating F4/80-positive macrophages and a diminution of vessel density, but not with obvious differences in fibrin and collagen deposition, or invasiveness of the tumor. Ablation of plasminogen activation by the tumor stroma only modestly impaired the prolonged growth of the sarcoma, suggesting that tumor cell-produced plasminogen activator is sufficient to mediate productive plasminogen activation. Plasminogen facilitated sarcoma progression, angiogenesis, and suppression of macrophage infiltration in the absence of either stromal urokinase plasminogen activator receptor or stromal plasminogen activator inhibitor. These data demonstrate that tumor cell-produced plasminogen activator and host plasminogen cooperate to facilitate soft tissue sarcoma growth and suppress the accumulation of tumor-infiltrating macrophages.

Ligneous Conjunctivitis in Plasminogen-Deficient Mice

Ligneous conjunctivitis is a rare form of chronic pseudomembranous conjunctivitis that is associated with systemic membranous pathological changes. A probable link between plasminogen and ligneous conjunctivitis has been indicated by the recent diagnoses of plasminogen deficiency in five patients suffering from ligneous conjunctivitis. The current study reports that plasminogen-deficient mice develop conjunctival lesions indistinguishable from human ligneous conjunctivitis in both appearance and histology. Both human and mouse lesions contain acellular material rich in fibrin, and aberrant or disrupted epithelium. The incidence of lesion development in mice increases with age and is strongly influenced by genetic background. Interestingly, ligneous conjunctivitis was not observed in plasminogen-deficient mice simultaneously lacking fibrinogen. This study provides direct evidence that plasminogen deficiency is one cause of ligneous conjunctivitis and suggests that plasminogen-deficient mice may be an excellent model for the development of therapeutic strategies for the treatment of this debilitating disease.