Abstract 4166: Small-molecule inhibition of glycogen synthase kinase-3 (GSK-3) increases the efficacy of anti-PD-L1 therapy in a murine model of microsatellite stable colorectal cancer (CRC); Therapeutic response correlates with T cell ratios and serum cytokine profiles in mice
Authors: Huntington Kelsey E. , Louie Anna , Zhou Lanlan , Carneiro Benedito A. , El-Deiry Wafik 
Published: June 2022

Abstract
Immune checkpoint blockade (ICB) with αPD-1/PD-L1 has impressive efficacy in microsatellite unstable (MSI+) CRC but no significant activity in the 85% of CRC cases that are microsatellite stable (MSS). Our group previously demonstrated that 9-ING-41, a small-molecule inhibitor of GSK-3 in clinical development, stimulates both NK and T cell activity. This project characterizes the effects of 9-ING-41 in combination with ICB in vivo. In a syngeneic murine colon carcinoma BALB/c model using MSS cell line CT-26, we compared isotype, 9-ING-41 (70 mg/kg 2x/wk), αPD-1 (10 mg/kg 2x/wk), αPD-L1 (10 mg/kg 2x/wk), 9-ING-41 + αPD-1, and 9-ING-41 + αPD-L1 treatment groups. The median overall survival was 19 days (d) with 9-ING-41 (hazard ratio for death (HR) 0.12; 95% confidence interval (CI), 0.03-0.54; p=0.008), 16 d for 9-ING-41 + isotype (HR 0.40; 95% CI, 0.08-1.9; p=0.14), 20.5 d for αPD-1 (HR 0.15; 95% CI, 0.03-0.67; p=0.0185), 18 d for αPD-L1 (HR 0.21; 95% CI, 0.05-0.89; p=0.0559), 17 d for 9-ING-41 + αPD-1 (HR 0.37; 95% CI, 0.09-0.1.5; p=0.29), and 45.5 d for 9-ING-41 + αPD-L1 (HR 0.08; 95% CI, 0.02-0.36; p=0.0019), compared to 16 d for the isotype control group. Tumor response rates observed were 33.3% in the 9-ING-41 + αPD-L1 group, 16.6% in the αPD-1 group, and a 0% for all other treatment groups. We hypothesize that the 9-ING-41-mediated upregulation of PD-L1 in CRC cells (HCT-116, HT-29) observed via both flow cytometry (FC) and western blot analysis may contribute to the increased efficacy of combination therapy with αPD-L1, as compared to αPD-1. Significant differences between responders and non-responders in intratumoral and splenic natural killer (NK) and T cell subsets 14-days post-treatment initiation were shown by multi-color FC. Compared to non-responders, regardless of treatment group, responders had lower percentages of splenic CD4+ (p=0.0145) and CD8+ T cells (p=0.0001), increased percentages of splenic CD69+ activated T cells (p=0.0070) and FOXP3+ regulatory T cells (p=0.001), and increased percentages of tumor-infiltrating CD3+ (p=0.0006) and CD4+ T cells (p&lt;0.0001). Responders had lower splenic CD8+/Treg (p=0.0007) and CD4+/Treg (p=0.001) ratios and higher intra-tumoral CD8+/Treg (p=0.0032) and CD4+/Treg (p=0.0001) ratios. Murine serum cytokine profiling showed that responders had lower concentrations of tumorigenic cytokines (BAFF, CCL7, CCL12, VEGF, VEGFR2, CCL21) and higher concentrations of immunomodulatory cytokines (CCL4, TWEAK, GM-CSF, CCL22, IL-12p70) compared to non-responders. These results demonstrate that small-molecule inhibition of GSK-3 with 9-ING-41 may increase the anti-tumor effects of ICB and improve response in patients with MSS CRC via modulation of anti-tumor immunity and cytokine signaling.
Citation Format: Kelsey E. Huntington, Anna Louie, Lanlan Zhou, Benedito A. Carneiro, Wafik El-Deiry. Small-molecule inhibition of glycogen synthase kinase-3 (GSK-3) increases the efficacy of anti-PD-L1 therapy in a murine model of microsatellite stable colorectal cancer (CRC); Therapeutic response correlates with T cell ratios and serum cytokine profiles in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4166.