Abstract 5112: Immune biomarkers of clinical response after NSAID treatment in combination with vaccination targeting EGFR-COX2-CDC25B in the APC(Min/+) mouse model

Abstract

Abstract Studies from our group have shown that administration of NSAIDs in mouse models of Familial Adenomatous Polyposis (FAP) results in a decrease in the development in small intestinal polyps with a significant increase in CD8 tumor infiltrating lymphocytes (TIL) and downregulation of PD-L1 on tumors. Furthermore, we have demonstrated that NSAIDs could be used in combination with vaccination to even further reduce the development of intestinal polyps. We questioned what tissue specific biomarkers could define the efficacy of response with the combination treatment. APC(Min/+) male and female mice (4-6 weeks old) were immunized with a multi-antigen (EGFR, COX2, CDC25B) peptide vaccine with CFA/IFA as an adjuvant. Control mice received immune adjuvant alone. Regular chow or chow containing 400 ppm naproxen was provided intermittently (3 weeks on, 3 weeks off for 3 cycles) or continuously (18 weeks on) at the initiation of the vaccine regimen. Animals were euthanized at 22 weeks and tumors quantified. TIL were evaluated by flow cytometry. Since intermittent naproxen treatment was just as effective at inhibiting tumor development as continuous naproxen treatment, with or without vaccine, we did not differentiate between NSAID regimens. We observed an increase in CD8+ (83%; p<0.0001), Tbet+CD4+ (94%; p<0.001), effector memory (EM) CD4+ (76%; p<0.0001) and EM CD8+ (94%; p<0.0001) TIL in the tumors that did develop in the mice treated with the combination NSAID and vaccination as compared to control. There was increased CD8+ (Pearson correlation coefficient: −0.506, p<0001), Tbet+CD4+ (Pearson correlation coefficient: -0.6222, p<0.001), EM CD4+ (Pearson correlation coefficient: 0.-6074, p<0.001) and EM CD8+ (Pearson correlation coefficient: -0.7155, p<0.001) in mice with greater tumor inhibition than those with less protection. Receiver operator curves revealed that CD8+ (AUC: 0.7623; p=0.002), Tbet+CD4+ (AUC 0.7273; p=0.008), EM CD4+ (AUC 0.6782; p=0.04) and EM CD8 (AUC 0.7897; p<0.001) TIL can differentiate mice receiving the combination of NSAID and vaccination as compared to either monotherapy alone. These data define potential biomarkers of response that can guide human clinical trials of NSAIDs +/- vaccination in patients with FAP. Citation Format: Denise L. Cecil, Ying Liu, Lauren Corulli, Mary L. Disis. Immune biomarkers of clinical response after NSAID treatment in combination with vaccination targeting EGFR-COX2-CDC25B in the APC(Min/+) mouse model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5112.