Mario A. Bourdon

Functional activation of integrin αvβ3 in tumor cells expressing membrane‐type 1 matrix metalloproteinase

Matrix metalloproteinases (MMPs) and integrins have been implicated in a variety of processes involved in tumor progression. To evaluate the individual roles of integrin αvβ3 and membrane‐type 1 matrix metalloproteinase (MT1‐MMP), as well as the effects of their joint expression on tumor cell functions, MCF7 breast carcinoma cells were transfected stably with either the MT1‐MMP, the β3 integrin subunit or both MT1‐MMP and β3 cDNAs. MT1‐MMP expression is accompanied by the functional activation of integrin αvβ3, thereby increasing vitronectin‐mediated adhesion and migration of MCF7 cells transfected with MT1‐MMP and integrin αvβ3. MT1‐MMP‐dependent functional activation of αvβ3 correlates with modification(s) of the β3 subunit, including its higher electrophoretic mobility and affected the LM609‐binding site. MCF7 cells jointly expressing MT1‐MMP and αvβ3 were the most efficient in adhesion to the recombinant C‐terminal domain of MMP‐2 as well as in generating soluble and cell surface associated mature MMP‐2 enzyme. These findings suggest a mechanism of selective docking of MMP‐2 at tumor cell surfaces, specifically at the sites that include MT1‐MMP and activated integrin αvβ3. These mechanisms may provide a link between spatial regulation of focal proteolysis by the cell surface associated MMPs and the regulation of integrin‐mediated motility of tumor cells. Int. J. Cancer 86:15–23, 2000.

Tenascin expression in human glioma cell lines and normal tissues

Tenascin expression was evaluated in 21 human glioma cell lines and in normal adult tissue extracts by Western and Northern blotting. The cell lines differed in their relative expression of tenascin in the cell-associated and supernatant compartments. Glioma cell line tenascin production was not uniformly stimulated by changes in fetal bovine serum concentration in the growth media. In most glioma cell lines and normal tissue extracts, reducing Western blots and Northern blots revealed two tenascin species, respectively: a major 340 kDa polypeptide and a 9 kb RNA transcript accompanied by a less intense 250 kDa polypeptide and 7 kDa RNA species. In U-87 MG and in normal adult kidney extracts, however, the 250 kDa band and 7 kb transcript were more prominent. Quantitation of tenascin in the glioma lines revealed variable levels that were significantly higher than those in the tissue extracts.

Human fetal brain antigen expression common to tumors of neuroectodermal tissue origin.

The antigenic relationship between human tumors of neuroectodermal origin and fetal brain were further investigated by characterization of two hybridoma antibodies derived from a fusion of P3-NS1/1-Ag 4-1 (NSI) myeloma cells and splenocytes hyperimmunized to second trimester human fetal brain homogenate. Monoclonal antibodies (MAs) 1H8cl 2 and 1H8cl 3 were analyzed by cell surface radioimmunoassay (CS-RIA), quantitative absorption, indirect immunofluorescence, and peroxidase-antiperoxidase (PAP) immunohistology. MA 1H8cl 3 is the more broadly reactive, binding to 9/14 glioblastoma (GBM), 2/3 neuroblastoma, 1/2 melanoma, and 1 medulloblastoma cell line(s) by CS-RIA analysis, and to 12/15 GBM, fetal brain, spleen, and liver, and adult spleen by PAP analysis. MA 1H8cl 2 is more restricted, binding to 7/14 GBM, 2/3 neuroblastoma, 1 medulloblastoma, and 2/3 fetal skin fibroblast cell line(s) by CS-RIA, and to 9/15 GBM and fetal brain and spleen by PAP analysis. Control non-central nervous system tumors and normal adult tissue including brain, thymus, lymph node, liver, kidney, lung, skin, and pancreas, were unreactive with both 1H8cl 2 and 1H8cl 3 by CS-RIA, PAP, and absorption analysis. The data presented here establish the unique nature of the detected antigenic specificities as compared to previously described oncofetal and onconeural antigens, and define two immune reagents which are operationally specific for tumors of neuroectodermal origin within the adult central nervous system.