[Antiproliferative effect of tumor necrosis factor-alpha on human glioblastoma cells]

Although tumor necrosis factor-alpha (TNF) has been applied to early clinical trials for patients with malignant glioma, majority of human glioma cells has been reported to be resistant to TNF cytocidal effect in vitro. This study investigated antiproliferative effect of the TNF associated with induction of differentiation and expression of two distinct TNF receptors on human glioblastoma cell lines. The expression of p55 and p75 TNF receptors on 12 human glioblastoma cell lines was assessed by polymerase chain reaction and flow cytometry. p55 TNF receptor was detected in all cell lines, and only 4 cell lines concomitantly expressed p75 TNF receptor. Twelve human glioblastoma cell lines were treated with low-dose TNF, up to 256 U/ml for 7 days. TNF did not exhibit its cytocidal effect, but showed antiproliferative effects with inhibition of DNA synthesis in majority of cell lines tested. Flow cytometry with the bromodeoxyuridine-propidium iodide dual staining technique demonstrated that this antiproliferative effect of TNF was attributed to accumulation of glioblastoma cells in G0/G1 phase, suppressing the proliferative pathway. Furthermore the TNF stimulation increased glial fibrillary acidic protein and production of bioactive molecules including interleukin(IL)-6, IL-8, granulocyte-macrophage colony stimulating factor, prostaglandin E2 and manganous superoxide dismutase. In conclusion, human glioblastoma cells had p55 TNF receptor as a functional receptor and well responded to low-dose TNF stimulation, but not susceptible TNF cytocydal effect. The effect of TNF on glioblastoma cells appeared to modulate cell differentiation. TNF may be utilized as an agent for a differentiation therapy for human glioblastomas.