TNF and osteosarcoma: To verify that the decrease in ATP levels observed following combined treatment with SM-164 and TNFα reflected abolition of clonogenic survival, we exposed primary tumor cells from three mice to a concentration of SM-164 likely to resemble the peak plasma level (5 μM) together with a concentration of TNFα slightly lower than that reported in the blood of osteosarcoma patients (10 pg/ml).