Fig. 4. SPOP mutants potentiate growth inhibition and induction of cGAS-STING by PARP inhibitor treatment, associated with increased inhibitory STAT3 phosphorylation and suppression of secretory signaling targets and non-canonical STING-NF-κB signaling in prostate cancer models.

A. MTS analysis of C4–2b and RM-1-BM (SPOPF102C or SPOPF133V) treated with siSTING or siNC in the presence and absence of olaparib (OLA), *, P<0.05, and **, P<0.01. B. Colony formation and C. MTS analysis of cell proliferation in doxycycline (Dox)-induced SPOP mutant-expressing C4–2b and RM-1-BM (SPOPF102C or SPOPF133V) in the presence and absence of OLA. T-test was used for statistical analysis, *, P<0.05, and **, P<0.01. D. Immunoblot analysis of OLA-induced DNA damage and canonical STING1 signaling activities (phosphorylation of STING1 and IRF3, and IFN-β) in Dox-induced C4–2b and RM-1-BM SPOP mutants compared to empty vector controls in a dose-dependent manner (Dox 10 and 200 ng/mL for C4–2b-SPOP models, or 20 and 200 ng/mL for RM-1-BM-SPOP models). E. Analysis of the effects of PARP inhibitor (OLA and talazoparib, TALA) on DNA damage (γH2AX), cGAS-STING-TBK1 signaling, IFN-β protein expression, p-S754-STAT3 expression, HMGA1/HMGBs secretory signaling protein expression, NF-κB signaling, IL-6 expression and expression of proapoptotic signaling proteins (cleaved caspases 3 and 7) in human and mouse SPOPmut models compared to empty vector control cells.