dNSurR9-C84A renders DU145 cancer cells susceptible to the proapoptotic effects of TNF-α. (A) 3D cultures of DU145 cells were treated with either R9-GST or dNSurR9-C84A in combination with increasing concentrations of TNF-α for 36 h, and cell viability measured by the MTT assay. (B) 3D cultures of DU145 cells were treated with either R9-GST or dNSurR9-C84A alone or in combination with TNF-α for 18 h and the activity of caspase-3 was measured. A statistically significant difference versus R9-GST is denoted as "*". *p < 0.05.