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

Abstract

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‐α) 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‐n was performed on all cell fines 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‐α at a concentration of 40 U/ml; rTNF‐α at 100 U/ml had antiprolif‐erative and cytotoxic effects on both cell lines. The growth and proliferation of cell tines SF‐126 and U 251 MG were not affected by rTNF‐α even at high concentrations (5,000 U/ml). The growth and proliferation of SF‐S39 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‐α. Time‐sequence electron microscopy showed that rTNF‐α 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 junctions! complexes, and fragmentation of the plasma membrane. Studies with ¹²⁵I‐rTNF‐α 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‐α (3,400 receptors/ cell with high affinity; k_d = 0.27 nm), while SF‐126, a highly resistant cell line, had the weakest binding (809 receptors/cell; k_d = 0.25 nm). We conclude that there is a spectrum of anti‐proliferative and cytotoxic activity among glioma‐derived tumor cell lines exposed to rTNF‐α. An increased number of rTNF‐α receptors appears to be a necessary but insufficient condition to explain the antiproliferative effects observed in some glioma‐derived cell lines.