Fig. 2: RB1 loss increases dependency on BCL-XL.
From: BH3 mimetics targeting BCL-XL have efficacy in solid tumors with RB1 loss and replication stress
A Genomic characterization of PCa models based on PCa-commonly altered genes. B Validation of RB1-loss induced sensitivity to BCL-XL inhibitor using an independent PCa PDX-derived spheroid cohort. Upper panels: RB1 expression by IHC and H-scores. Lower panels: organoid cultures from each PDX were treated with navitoclax for 6 h and caspase activity was assessed (left), or treated for 4 days and cells viability was assessed (right). Mean and SEM for 5 biological replicates are shown. Data were analyzed by one-way ANOVA *p < 0.05 (left panel: p = 0.003 for model CP267C and p = 0.002 for model CP336C, right panel: p = 0.002 for model CP267C and p = 0.001 for model CP336C). Scale bar is 100 μM. C Comprehensive analysis of solid tumor cell lines sensitivity to BCL-XL inhibitors (Navitoclax, WEHI and ABT737) based on RB1 alteration (combined mutation or copy number loss). Data were analyzed by unpaired t-test. D Volcano plot with effect size (x axis) and significance (y axis) of large-effect cancer-specific pharmacogenomic interactions based on RB1 alteration. Each circle represents an association between RB1 status and drug sensitivity analyzed using ANOVA (Genomics of Drug Sensitivity in Cancer- Sanger Institute/Mass General Cancer Center database). E Effect of short term RB1 silencing on BCL-XL sensitivity in LNCaP (RB1 proficient PCa cell line). Cells were treated with siRNA targeting RB1 (siRB1) or nontarget control (siNT) for 48 h. Navitoclax was then added to media for 6 h. Apoptotic effect was assessed by luminescence assay over a range of navitoclax concentrations (left panel) and apoptosis markers at 500 nM navitoclax by immunoblotting (right panel). Mean and SEM for 3 biological replicates are shown. Effects of RB1 siRNA at each navitoclax concentration were analyzed by unpaired t-test, *p < 0.05. Two-way ANOVA then showed that the effect of the shRNA on response to navitoclax was significant (p = 0.002). F Effect of long-term RB1 silencing on BCL-XL sensitivity in LNCaP cells. Cells were infected with shRNA targeting RB1 (shRB1) or nontarget control (shNT) constructs and treated with increasing doses of enzalutamide until development of resistance to 5 μM. Left panel: RB1 expression in the enzalutamide adapted cells. Middle panel: apoptosis activity of cells treated with navitoclax for 6 h based on luminescence assay. Right panel: viability assay of cells treated with navitoclax for 4 days based on luminescence assay. Mean and SEM for 3 biological replicates are shown. Effects of RB1 shRNA at each Navitoclax concentration were analyzed by unpaired t-test, *p < 0.05. Two-way ANOVA then showed that the effect of the shRB1 on response to Navitoclax was significant (p = 0.0001 for both apoptosis and viability analysis). Source data are provided as a Source Data file.
