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Fas-mediated apoptosis in Ewing's sarcoma cell lines by metalloproteinase inhibitors
N Mitsiades1, V Poulaki, A Leone
1Laboratory of Pathology, Division of Clinical Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD. mitsiade@helix.mgh.harvard.edu
Background:
Fas ligand (FasL) is a transmembrane protein that induces apoptosis (programmed cell death) in susceptible cells by interacting with its receptor, Fas. Transmembrane FasL is cleaved by a metalloproteinase enzyme into a soluble form that is released into the extracellular medium. Tumors of the Ewing's sarcoma family express functional transmembrane FasL and release soluble FasL. This cleavage is inhibited by a matrix metalloproteinase inhibitor (MMPI). We therefore hypothesized that MMPIs can lead to apoptosis of tumor cells by inducing accumulation of transmembrane FasL.
Methods:
Ewing's sarcoma and neuroblastoma cell lines were treated with two synthetic MMPIs (BB-3103 and A-151011) and examined for apoptosis and expression of FasL and Fas.
Results:
Although MMPIs increase levels of FasL and Fas proteins on the surface of all tumor cells studied, they induced apoptosis in Fas-sensitive but not in Fas-resistant cell lines; the induction of apoptosis was inhibited by a Fas-neutralizing antibody. The increase in protein expression was not associated with enhanced transcription. Treatment with an MMPI sensitized the Ewing's sarcoma cells to Fas-activating antibody and to doxorubicin-induced apoptosis.
Conclusions:
MMPIs cause accumulation of transmembrane FasL by inhibiting its cleavage, accumulation of Fas (probably secondarily to FasL cleavage inhibition), and decreased levels of soluble FasL. These effects lead to apoptosis in Fas-sensitive cell lines. The observed cooperative action of MMPIs and doxorubicin suggests a possible role of MMPIs in combination treatments with standard apoptosis-inducing chemotherapeutic agents.
Insights
Matrix metalloproteinase inhibitors (MMPIs) induce tumor cell apoptosis by increasing transmembrane Fas ligand (FasL) and Fas levels. This approach shows promise for combination cancer therapy.
Area of Science:
- Oncology
- Molecular Biology
- Cell Death Research
Background:
- Fas ligand (FasL) induces apoptosis; its soluble form is released after cleavage by metalloproteinases.
- Ewing's sarcoma family tumors express functional FasL, releasing soluble FasL.
- Matrix metalloproteinase inhibitors (MMPIs) block FasL cleavage, potentially increasing transmembrane FasL.
Purpose of the Study:
- To investigate if MMPIs can induce tumor cell apoptosis by accumulating transmembrane FasL.
- To explore the mechanism of MMPI-induced apoptosis in cancer cells.
Main Methods:
- Ewing's sarcoma and neuroblastoma cell lines were treated with synthetic MMPIs (BB-3103, A-151011).
- Apoptosis, FasL, and Fas expression levels were analyzed.
- Fas-sensitive and Fas-resistant cell lines were differentiated.
Main Results:
- MMPIs increased surface FasL and Fas protein levels in tumor cells.
- Apoptosis was induced only in Fas-sensitive cell lines, inhibited by a Fas-neutralizing antibody.
- Increased protein expression was not linked to enhanced transcription.
Conclusions:
- MMPIs inhibit FasL cleavage, leading to transmembrane FasL and Fas accumulation.
- This accumulation induces apoptosis in Fas-sensitive tumor cells.
- MMPIs may enhance standard chemotherapy, like doxorubicin, in combination treatments.