Fig. 5: Replication stress sensitization to navitoclax is mediated by decreased BIRC5/Survivin.

A LNCaP cells were treated with siRNA targeting BAX or BAK for 24 h followed by 48 h treatment with nolatrexed (4 μM), and addition of navitoclax for last 6 h. Whole cell lysates were then immunoblotted as indicated. B LNCaP cells were treated as in A with nolatrexed (4 or 8 μM). Apoptosis was quantified by CaspaseGlo 3/7 assay and displayed as a heat map. C Analysis of anti-apoptotic proteins in LNCaP cells treated with nolatrexed and navitoclax. Fold change in BCL-2 is quantified. D Analysis of pro-apoptotic proteins in LNCaP cells treated with nolatrexed and navitoclax. E Analysis of further pro- and anti-apoptotic genes in LNCaP cells treated with nolatrexed and navitoclax. Fold change in Survivin is quantified. F Survivin/BIRC5 was silenced with siRNA (versus nontarget siRNA) for 3 days in LNCaP cells and apoptosis markers after nolatrexed and navitoclax treatment were assessed with immunoblotting. G Survivin/BIRC5 was silenced with siRNA and Caspase 3/7 activity in response to navitoclax and S63845 was assessed. Mean and SEM for 5 biological replicates are shown. Data were analyzed by unpaired t-test, ***p < 0.001. H–J LNCaP cells treated with YM-155 were immunoblotted (H) and assessed for Caspase 3/7 activity in combination with navitoclax (I) or AZD4320 (J). Mean and SEM for 5 biological replicates are shown. Data at each YM-155 concentration were analyzed by unpaired t-test, *p < .05. Analysis by two-way ANOVA showed significant enhancement of apoptosis by YM-155 in I and J, p < 0.001 in both. Source data are provided as a Source Data file.