The effects of human recombinant tumor necrosis factor on glioma-derived cell lines: cellular proliferation, cytotoxicity, morphological and radioreceptor studies.

To determine whether tumor necrosis factor is of potential value for the treatment of human malignant gliomas, we studied the effects of human recombinant tumor necrosis factor (rTNF-alpha) on the morphology, incorporation of tritiated thymidine, and proliferation of 5 established cell lines derived from human malignant gliomas and 3 normal human brain cell cultures. A radioreceptor analysis for rTNF-alpha was performed on all cell lines and cultures. Two of the 5 human glioma cell lines (SF-188 and U 343 MG-A) demonstrated a marked decrease (60% or less of untreated controls) in the uptake of tritiated thymidine when treated with rTNF-alpha at a concentration of 40 U/ml; rTNF-alpha at 100 U/ml had antiproliferative and cytotoxic effects on both cell lines. The growth and proliferation of cell lines SF-126 and U 251 MG were not affected by rTNF-alpha even at high concentrations (5,000 U/ml). The growth and proliferation of SF-539 were affected to an intermediate degree. A colony-forming efficiency assay corroborated the results of the proliferation studies: SF-126 was relatively resistant (surviving fraction of 0.9 at 500 U/ml) and SF-188 was relatively sensitive (surviving fraction of 0.08 at 500 U/ml) to the cytotoxic effects of rTNF-alpha. Time-sequence electron microscopy showed that rTNF-alpha at a concentration of 500 U/ml caused ultrastructural changes in SF-188, including increased intracytoplasmic vesiculation, swelling and degeneration of mitochondria, loss of cell:cell junctional complexes, and fragmentation of the plasma membrane. Studies with 125I-rTNF-alpha showed a variable degree of binding in all cell lines and cultures. SF-188, a highly sensitive cell line, demonstrated the strongest binding of 125I-rTNF-alpha (3,400 receptors/cell with high affinity; kd = 0.27 nM), while SF-126, a highly resistant cell line, had the weakest binding (809 receptors/cell; kd = 0.25 nM). We conclude that there is a spectrum of antiproliferative and cytotoxic activity among glioma-derived tumor cell lines exposed to rTNF-alpha. An increased number of rTNF-alpha receptors appears to be a necessary but insufficient condition to explain the antiproliferative effects observed in some glioma-derived cell lines.