Riadh Ksontini

A matrix metalloproteinase inhibitor prevents processing of tumor necrosis factor α (TNFα) and abrogates endotoxin-induced lethality

Excessive tumor necrosis factor α (TNFα) production in response to Gram-negative bacteremia or endotoxemia can often lead to hypotension, shock, and increased mortality. Current approaches used to block the deleterious effects of exaggerated TNFα production rely on monoclonal antibodies or immunoadhesins that bind TNFα and thus prevent the interaction with its cellular receptors. This report examines whether a previously described inhibitor of matrix metalloproteinases, GM-6001, can inhibit TNFα processing and release and attenuate endotoxin-induced mortality. In human peripheral blood mononuclear cells stimulated in vitro with 1 μg/mL endotoxin, GM-6001 at concentrations <5 μg/mL blocked release of TNFα, but did not affect the release of either IL-1β or IL-6. GM-6001 also inhibited the release of soluble TNF receptor (p75) from peripheral blood mononuclear cells stimulated with endotoxin and/or TNFα. To confirm the role of secreted TNFα in endotoxic shock-induced mortality, C57BL/6 mice were challenged with either endotoxin alone (500 μg/mouse) or endotoxin (100 ng/mouse) plus D-galactosamine (8 mg/mouse). GM-6001 pretreatment (100 mg/kg) significantly attenuated the 90-minute plasma TNFα response in both models and improved survival in mice treated with low-dose endotoxin plus D-galactosamine. However, plasma IL-1β and IL-6 concentrations at 90 min after endotoxin treatment were unaffected by GM-6001 following lethal endotoxin challenge, confirming the in vivo specificity of this matrix metalloproteinase inhibitor for TNFα processing. These findings demonstrate that a novel inhibitor of matrix metalloproteinases can prevent the release of TNFα both in vitro and in vivo, and can abrogate the harmful sequelae of endotoxemic shock.

Transfection of the Type Ii Tgf-β Receptor Into Colon Cancer Cells Increases Receptor Expression, Inhibits Cell Growth, and Reduces the Malignant Phenotype

OBJECTIVE To determine if transfection of SW48 colon cancer cells with the type II transforming growth factor-beta (TGF-beta) receptor restores growth inhibition and reverses the in vitro and in vivo malignant phenotype. SUMMARY BACKGROUND DATA The authors have previously shown that SW48 colon cancer cells that are replication error positive in both alleles lack functional cell surface TGF-beta type I (RI) and type II (RII) receptors and are insensitive to TGF-beta1-induced growth inhibition. METHODS SW48 cells were stably transfected with the cDNA for the normal type II TGF-beta receptor (RII). Once transfected, the cells were evaluated for in vitro phenotypic changes and in vivo changes in tumor growth. RESULTS Denaturing sequencing gel electrophoresis of the reverse transcriptase-polymerase chain reaction product from SW48 cells revealed that the RII coding sequence contained a single base deletion mutation. When these cells were transfected with normal RII cDNA, Northern and Western blot analyses revealed increased levels of RII mRNA and protein. Affinity labeling techniques revealed that RII-transfected SW48 cells produced functional RI and RII protein. Transfection of SW48 cells also led to changes in cell phenotype, as shown by inhibition of both in vitro growth rate and incorporation of [3H]-thymidine. SW48 cells expressing normal RII also exhibited reduced cloning efficiency in semisolid medium and reduced growth as a xenograft in NOD/LtSz-scid/J mice. CONCLUSIONS The results confirm that RII is a tumor-suppressor protein that is required for TGF-beta-induced growth inhibition in SW48 colon cancer cells.