Razmik Ghukasyan

Supplementary Fig. 1 STING agonist diABZI synergizes with MAPK inhibition in PDAC by enhancing apoptosis.

Supplementary Fig. 4 Immunoblot analysis demonstrating the effect of ± 100 U/ml exogenous IFN on CFPAC-1 and SUIT2 parental cells compared to their respective IFNAR-deficient isogenic cell lines. (B) Immunoblot analysis of CFPAC-1 parental and IFNAR1-KO cells exposed to ± 1 µM diABZI ± 100 nM trametinib for 24 h (C)Immunoblot analysis of the effects of ± 100 U/ml exogenous IFN ± 1 µM diABZI for 24 h.

Supplementary Fig. 2 Tumor growth is inhibited by STING agonism and MEK inhibition in vivo.

Supplementary Fig. 3 MEK inhibition amplifies STING-induced transcription of IFNB1, IL-6, and TNFA in multiple PDAC cell lines.

Supplementary Fig. 5 IL6 is not responsible for the synergistic effects of STING agonism and MEK inhibition.

Supplementary Resources and Table

Supplementary Fig. 3 MEK inhibition amplifies STING-induced transcription of IFNB1, IL-6, and TNFA in multiple PDAC cell lines.

Supplementary Fig. 5 IL6 is not responsible for the synergistic effects of STING agonism and MEK inhibition.

Supplementary Fig. 4 Immunoblot analysis demonstrating the effect of ± 100 U/ml exogenous IFN on CFPAC-1 and SUIT2 parental cells compared to their respective IFNAR-deficient isogenic cell lines. (B) Immunoblot analysis of CFPAC-1 parental and IFNAR1-KO cells exposed to ± 1 µM diABZI ± 100 nM trametinib for 24 h (C)Immunoblot analysis of the effects of ± 100 U/ml exogenous IFN ± 1 µM diABZI for 24 h.

Purpose: STING (Stimulator of Interferon Genes) agonists are currently in development for treatment of solid tumors, including pancreatic ductal adenocarcinoma (PDAC). Response rates to STING agonists alone have been promising yet modest and combination therapies will likely be required to elicit their full potency. We sought to identify combination therapies and mechanisms that augment the tumor-cell intrinsic effect of therapeutically relevant STING agonists apart from their known effects on tumor immunity. Experimental Design: We screened 430 kinase inhibitors to identify synergistic effectors of tumor cell death with diABZI, an intravenously administered and systemically available STING agonist. We deciphered the mechanisms of synergy with STING agonism that cause tumor cell death in vitro and tumor regression in vivo. Results: We found that MEK inhibitors caused the greatest synergy with diABZI and that this effect was most pronounced in cells with high STING expression. MEK inhibition enhanced the ability of STING agonism to induce Type I interferon-dependent cell death in vitro and tumor regression in vivo. We parsed NF-κB-dependent and independent mechanisms that mediate STING-driven Type I interferon production and show that MEK signaling inhibits this effect by suppressing NF-κB activation. Conclusions: Our results highlight the cytotoxic effects of STING agonism on PDAC cells that are independent of tumor immunity, and that these therapeutic benefits of STING agonism can be synergistically enhanced by MEK inhibition.