Urokinase-type plasminogen activator overexpression enhances the invasive capacity of endothelial cells.

Fetal bovine aortic endothelial GM 7373 cells were transfected with a viral expression vector harboring the human urokinase-type plasminogen activator (uPA) gene. The stable transfectant clone uPA-R5 overexpressed and secreted human uPA as shown by Northern blot analysis, immunoprecipitation of metabolically labeled proteins, plasmin chromogenic assays, and SDS-PAGE zymography of cell extracts and conditioned media. The uPA-R5 cells were analyzed for their invasive capacity in vitro in the Matrigel chemoinvasion assay in the presence of serine- or metalloprotease inhibitors. uPA overexpression enhanced the invasive capacity of GM 7373 cells through a mechanism which differs from that mediated by metalloproteases. Endothelial cell uPA transfectants may represent an useful experimental model to investigate the role of uPA in angiogenesis and angioproliferative diseases.

Characterization of tumorigenic sub-lines from a poorly tumorigenic human colon-adenocarcinoma cell line.

The interaction of tumor cells with extracellular-matrix components is suspected to play an important role in tumorigenesis induction. The tumorigenicity of a poorly tumorigenic human colon-adenocarcinoma cell line (BCS-TC2) was induced by co-injection with Matrigel. A new cell sub-line, BCS-TC2.1, was isolated and established from these tumors. Implantation of these cells in nude mice in the absence of Matrigel-generated tumors which allowed the establishment of another tumorigenic cell sub-line, BCS-TC2.2. Matrigel and laminin, but not collagens, promote the tumorigenicity of BCS-TC2 cells, probably due to specific interactions of a pre-existing minor cell sub-population with laminin, which facilitate the initial growth of these cells in vivo. Cytogenetic analysis reveals that both sub-lines originate from the parental one, but a new marker in chromosome 9 is observed. These sub-lines present a lower degree of differentiation, as deduced from the lower CEA content, 5'-nucleotidase and alkaline-phosphatase activities. No variation is observed in the mRNA and protein expression of the 67-kDa laminin-binding protein. However, an increase in beta1 integrins and a parallel decrease in beta4 integrin were detected. Thus, the new sub-lines, compared to the parental cells, present karyotypic and phenotypic differences such as the expression of a distinctive integrin pattern. This system represents a useful model for understanding the development and progression of tumorigenicity in cancer cells.