Impact of TRAIL/zVAD/CHX- and TNF/zVAD/CHX-induced programmed necrosis on clonogenic survival. Cells were treated with zVAD/CHX, TRAIL/zVAD/CHX or TNF/zVAD/CHX for 24 h as in Figure 1a and b. Subsequently, their ability to form colonies was analyzed by staining with crystal violet (or by soft agarose cloning for the non-adherent cell line U-937) after 7 days. Treatment with zVAD/CHX (negative control) served as reference for calculation of colony formation as well as of P values. *P < 0.05, ***P < 0.001.