Enhancement of Fas-ligand-mediated programmed cell death by taurolidine

Abstract

Background: Taurolidine was recently found to have a direct and selective antineoplastic effect on brain tumor cells. The ability of taurolidine to exert antineoplastic action by enhancement of Fas-mediated apoptosis in different malignant glioma cell lines was investigated.

Materials and methods: Human derived U373 cells were cultured and incubated with taurolidine and the median inhibitory concentration (IC50) was calculated. Flow cytometric analysis was performed to assess changes in DNA content. The cells were qualitatively and quantitatively examined using light microscopy and electron microscopy. LN-18 and LN-229 cells were incubated in the absence or presence of either Fas-ligand, taurolidine or respective combinations thereof. The cell viability was determined by adding a double concentrated WST-1 reagent. The activity of the mitochondrial succinate reductase was measured in an ELISA reader.

Results: The exposure of U373 cells to taurolidine led to a concentration-dependent (IC50 35.8 +/- 2.2 micrograms/ml) loss of cell viability. Flow cytometric analysis demonstrated a concentration-dependent appearance of DNA debris in the sub-Go/G1 region. In the presence of 6.25 vol.% Fas-ligand, LN-18 cells displayed more than 90% loss of cell viability, whereas the viability of LN-229 cells was reduced only at higher concentrations of Fas-ligand. Taurolidine by itself did not appreciably affect the viability of LN-18 cells in the investigated concentration range, but was able to enhance the effect of Fasligand on LN-18 cells. The exposure of LN-229 cells to taurolidine alone caused an appreciable loss of cell viability by about 70% at the highest concentration tested. Cell destruction by Fas-ligand (10 vol.%) was enhanced in the presence of taurolidine.

Conclusion: The antineoplastic activity of taurolidine seems to be partially based on the enhancement of Fas-ligand-induced apoptosis. In addition, taurolidine was demonstrated to have an antieoplastic effect independent of Fas-ligand. Perhaps taurolidine exerts antineoplastic activity based on different mechanisms.