Fig. 2: Triggering β-AR signaling suppresses intrinsic apoptotic pathways in MDSCs.

A, B MDSCs were generated in vitro using IL-6 (40 ng/ml) and GM-CSF (40 ng/ml) with and without isoproterenol (10 µM) treatment in both wild type (WT) and β2-AR^-/- MDSCs. These cells were then exposed to increasing concentrations of doxorubicin (1−1000 ng/ml). After 20 h. the apoptosis rate was measured by Annexin V (apoptotic cell: Aqua+ Annexin V + ) in (A) CD11b⁺Ly6C⁺Ly6G^- (M-MDSC) (*p = 0.0109; **p = 0.0030) and (B) CD11b⁺Ly6C⁺Ly6G⁺ (PMN-MDSC) (*p = 0.0216; ****p < 0.0001). One-way ANOVA with Bonferroni’s multiple comparison tests. Data are presented as mean ± SEM. Representative of three independent experiments with n = 3 technical replicates per group. Activated caspase 3 was detected in in vitro generated MDSCs as (C) M-MDSC (*p = 0.0419; **p = 0.0019) and (D) PMN-MDSC (*p = 0.0158; *p = 0.0455) by CaspGLOW™ Caspase-3 staining assay. One-way ANOVA with Bonferroni’s multiple comparison tests. Data are presented as mean ± SEM. Representative of three independent experiments with n = 3 technical replicates per group. E, F MDSCs were generated in vitro, and their transcriptomics profile was evaluated by single cell RNA sequencing (scRNA-seq). E tSNE plots demonstrate distribution of MDSC subpopulations, and (F) the heatmap summarizes the top genes correlated with each subpopulation. G Overall gene profile shift in generated MDSCs for intrinsic apoptotic pathway. Each data point represents pathway score value of a cluster (clusters 0−5 of E, F). Results are shown as representative of n = 6 clusters per group. Data are presented as mean ± SEM. Apoptosis Phospho-Antibody Array used to detect apoptotic pathways on in vitro generated (H) WT + ISO vs. WT + PBS, and (I) β2-AR^-/- + ISO vs. β2-AR^-/- + PBS control MDSCs. Source data containing independents experiment raw data are provided as a Source Data file.