Oncogene expression and cytotoxic activity of tumor necrosis factor against human cancer cells

We studied the effect of recombinant tumor necrosis factor (TNF) on selected leukemic and breast cancer cell lines. Based on their sensitivity to TNF in the presence or absence of cycloheximide (CHX), these cell lines could be categorized into three phenotypes: SS, cells that are spontaneously sensitive to TNF; RS, cells that are normally resistant to TNF but are killed in the presence of CHX; and RR, cells that are resistant to TNF irrespective of the presence of CHX. The effect of TNF on expression of c-myc, N-ras, and Ha-ras oncogenes was also studied in these cell lines. Transient, minimal suppression of c-myc was observed in one cell line (Raji), and an inconsistent stimulation of c-myc in another (MCF-7.OCI). No correlation was observed between the effect on oncogene expression and TNF sensitivity.