The regulation of matrix metalloproteinase-9 (MMP-9) expression in glioma cells is one of the key processes in tumor invasion through the brain extracellular matrix. Although some studies have demonstrated the implication of classic protein kinase C (PKC) isoforms in the regulation of MMP-9 production by phorbol esters or lipopolysaccharide, the involvement of specific PKC isoforms in the signaling pathways leading to MMP-9 expression by inflammatory cytokines remains unclear. Here we report that the atypical PKC-isoform participates in the induction of MMP-9 expression by interleukin-1 (IL-1) and tumor necrosis factor-␣ (TNF-␣) in rat C6 glioma cells. Indeed, zymography and semi-quantitative reverse transcriptase-PCR analysis showed that pretreatment of C6 cells with PKC-pseudosubstrate abolished MMP-9 activity and gene expression induced by IL-1 or TNF-␣. Accordingly, IL-1 and TNF-␣ were able to induce PKC-activity, as demonstrated by in vitro kinase assay using immunoprecipitated PKC-. Furthermore, stable C6 clones overexpressing PKC-, but not PKC-⑀, displayed an up-regulation of MMP-9 constitutive expression as well as an increase of mmp-9 promoter activity. These processes were inhibited by an NF-B-blocking peptide and completely prevented by NF-B-binding site mutation in the mmp-9 promoter. Taken together, these results indicate that PKC-plays a key role in the regulation of MMP-9 expression in C6 glioma cells through NF-B.Glioma cells have the ability to invade brain tissues by secreting matrix metalloproteinases (MMPs), 1 a family of proteases able to degrade different components of the extracellular matrix including collagen, fibronectin, and proteoglycans. One of these MMPs, MMP-9, has received much attention as its expression correlates with the progression of glioma (1). Furthermore, MMP-9 seems to be essential for the invasiveness of glioma cells, as it was recently reported that the inhibition of MMP-9 expression by antisense gene transfer strongly reduced the invasion of glioblastoma cells in vitro and in vivo (2). Therefore, understanding the role of the molecules implicated in the signaling pathways leading to mmp-9 gene expression in glioma cells is important in order to identify new therapeutic targets. Several studies (3-5) have focused on the implication of protein kinase C (PKCs) in the regulation of mmp-9 gene expression, most notably by testing the effect of phorbol 12-myristate 13-acetate (PMA) on different types of cells, including human glioma cells. Members of the PKC family are divided into the following three groups of isoenzymes: the conventional PKC isoforms, which are activated by calcium and diacylglycerol (␣, ␤I, ␤II, and ␥); the novel PKCs, which are activated by diacylglycerol but are calcium-insensitive (␦, ⑀, , and ); and the atypical PKCs, which are calcium-and diacylglycerol-insensitive ( and /). Despite the fact that a large number of studies (5-7) have established a link between PKCs and MMP-9 expression using PKC inhibitors, very few studies have addressed the implicat...

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We have previously shown that ICAM-1-deficient mice were resistant to lymphoma dissemination of intravenously injected 164T2 lymphoma cells. Highly aggressive variants of this cell line, however, could overcome this resistance. To discern the complex pattern of gene expression involved in the evolution of aggressiveness in lymphoma cells, we compared the transcriptome of 164T2 cells with that of their aggressive variants using cDNA arrays. We identified several genes that were differentially expressed in nonmetastatic lymphoma cells and their metastatic variants. Galectin-7, associated with the development of chemically induced mammary carcinoma, was one such gene whose expression was significantly upregulated. We showed that it was constitutively expressed in aggressive variants, at both mRNA and protein levels. Galectin-7 expression in aggressive lymphoma cells was induced upon in vivo selection in several organs, including the thymus, the spleen and kidneys. We also showed that treatment of nonaggressive lymphoma cells with 5-aza-2 0 -deoxycytidine was sufficient to induce galectin-7 gene expression. This report is the first to show that galectin-7 is expressed in aggressive lymphoma.

The extracellular moiety of ICAM-1 consists of five Ig-like domains, the first and third domains mediating adhesion to integrin ligands. The ICAM-1 gene, however, gives rise to the expression of five alternative splice variants containing two, three, or four Ig-like domains. In this work, we have investigated whether the rearrangement of the architecture of ICAM-1 affects its structural properties and function. We showed that, in contrast to the common form, all alternative isoforms of ICAM-1 were susceptible to cleavage by leukocyte elastase and cathepsin G. We found that the length of an isoform did not influence the susceptibility to proteolysis. The molecular diversity provided by the skipping of entire Ig domains and the level of expression on the APC, however, significantly influenced their ability to potentiate the proliferation of T cells. Finally, we found that the expression of minor ICAM-1 isoforms encoding the third Ig-like domains was sufficient to sustain neutrophil infiltration in the liver and confer exon-5-targeted ICAM-1-deficient mice susceptibility to LPSinduced septic shock. These findings not only demonstrate that ICAM-1 isoforms are fully functional, but support the concept that alternative RNA splicing in the Ig superfamily may fulfill distinct roles during the development of the immune response.

Matrix metalloproteinase (MMP) 10 (stromelysin-2) is known to degrade various components of the extracellular matrix; however, the signals that regulate its expression and its role in lymphoma growth remain unknown. In the present work, we report the up-regulated expression of MMP10 in T lymphoma cells following contact with endothelial cells. The induction of MMP10 was found to be dependent on the specific interaction between LFA-1 and ICAM-1, which play a central role in regulating the expression of genes involved in the rate-limiting steps of lymphoma development. MMP10, but not MMP3 (stromelysin-1), was also up-regulated in human B lymphoma cells following exposure to IL-4, IL-6, and IL-13, but not to IL-1. To gain further insight into the role of MMP10 in lymphoma development, we generated lymphoma cell lines constitutively expressing high levels of MMP10 and studied these cells for their ability to form thymic lymphoma in vivo. Mice injected with lymphoma cells constitutively expressing MMP10 developed thymic lymphoma more rapidly than those injected with control lymphoma cells. These results provide the first in vivo evidence that overexpression of MMP10 promotes tumor development, and indicate that MMP10 induction is an important pathway activated not only upon ICAM-1/LFA-1-mediated intercellular contact, but also following activation of tumor cells with inflammatory cytokines.