Abstract 6333: Repurposing NSAIDs for chemo-immunotherapy: mechanisms beyond COX inhibition

Abstract It has been well-established that some nonsteroidal anti-inflammatory drugs (NSAIDs) have antitumor activities. The beneficial effects of these NSAIDs are mainly attributed to their ability to inhibit the production and activity of cyclooxygenases (COX1 and COX2) and prostaglandin (PGE2), which are known to promote tumor progression, angiogenesis, metastasis and immunosuppression. We recently reported that administration of indomethacin, a prototypical NSAID, can enhance the antitumor efficacy of adoptive T cell therapy in animal models. However, currently adoptive T cell therapy as a treatment option is only suitable for selected patients with certain types of cancer. Here, we set out to explore the utility of indomethacin in a chemo-immunotherapy setting that is readily applicable to a wide range of cancers. Cyclophosphamide (CTX) is a widely used antineoplastic chemotherapeutic agent with immunostimulatory activities when used at low-medium doses. We show that indomethacin had no impact on tumor growth but can significantly enhance the antitumor effect of CTX in multiple mouse tumor models. The beneficial effect of indomethacin was diminished in immunodeficient mice or CD8 T cell-depleted wild-type mice, indicating the requirement for the host immunity. Furthermore, the CTX and indomethacin regimen can sensitize tumors to anti-PD1 immunotherapy. scRNAseq analysis of tumor samples revealed the impact of indomethacin on the tumor microenvironment. Our data also indicate that the immunopotentiating effect of indomethacin can be independent of PGE2 inhibition, and involves the TRAIL-DR5 axis in promoting tumor regression. Other potential mechanisms, including modulation of chronic interferon signaling in tumor cells, have also been investigated. Altogether, our study sheds light on the multiple mechanisms underlying indomethacin’s beneficial effects, and highlights the potential of NSAID administration as a readily applicable and cost-effective approach to augment the efficacy of chemo-immunotherapy. Citation Format: Ogacheko D. Okoko, Md Y. Gazi, Xin Wang, Caitlin Brandle, Mercy Kehinde-Ige, Gary A. Piazza, Huidong Shi, Gang Zhou. Repurposing NSAIDs for chemo-immunotherapy: mechanisms beyond COX inhibition [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 6333.