Abstract 182: Cyclooxygenase-2 blockade is crucial to restore natural killer cell activity before anti-CTLA-4 therapy against high-grade serous ovarian cancer

Abstract Objective: Here our goal was to evaluate the impact of the immunosuppressive enzyme cyclooxygenase-2 (COX-2) expression on the immune effector capacity against high-grade serous ovarian cancer (HGSOC) tumor cells through bioinformatic tools and in vitro validation. Methods: We performed an integrated bioinformatics analysis from transcriptomic data based on RNAseq (TCGA-OV, n=368; Australian cohort AOCS, n=80) and RNA microarrays (GSE26193, n=62; GSE30161, n=45). We estimated the proportion and characteristics of immune cells employing Gene Set Variation Analysis (GSVA), MIXTURE and Ecotyper cell deconvolution algorithms. Survival curves and Cox-regression models were built up according to known risk factors and immune scores predicted by in-silico analysis. Afterward, we validated these results using flow cytometry and cytotoxicity assays on circulating NK cells collected from advanced HGSOC patients treated at our institution (n=5). After three days of incubation, isolated NK cell cultures were stimulated with three pulses of a selective COX-2 inhibitor (celecoxib) or MOCK, daily. An anti-CTLA-4 monoclonal antibody (ipilimumab) or MOCK was added at the third pulse. Two ovarian cancer cell lines (SKOV3 and HeyA8) were treated similarly. Next, NK cells were co-cultured with SKOV3 or HeyA8 and cytotoxicity on these cells was examined using lactate dehydrogenase (LDH) cell viability assay. Results: Transcriptomic data evidenced a non-linear relationship between COX-2 gene, PTGS2, and CTLA4 in advanced stages of HGSOC. Hence, PTGS2/CTLA4 ratio allows us to investigate how COX-2 influences changes in the immune profile of these patients. Based on bioinformatics, a high PTGS2/CTLA4 ratio determines particularly dysfunctional NK cell states, along with the reduction of NK gene score associated with infiltration, cytotoxicity, and survival in HGSOC. Additionally, selective COX-2 blockade improves NK cell cytotoxicity against HGSOC cell lines independently of the CTLA-4 signaling. In fact, ipilimumab effect was almost absent in those cases with high COX2 activity. Interestingly, previous treatment with celecoxib on NK cells mainly explains the difference in cytotoxicity (p= 0. 0253, two-way ANOVA test with Tukey’s multiple comparisons). Conclusions: This work represents the first evidence of the influence of COX-2 on NK cell function as a crucial factor for the efficacy of anti-CTLA-4 therapy in HGSOC patients who exhibited high tumoral levels of CTLA-4. HGSOC patients present dysfunctional circulating NK cells preferentially due to the strong CO-2 expression. Last, we emphasize the modulation of chronic inflammation to direct an immune pattern with greater antitumor capacity in HGSOC. (Funding: Fondecyt 1201083 and FONDAP 152220002 MAC, CONICYT/Doctorado Nacional 2019-Folio 21190421 FGV, CONICYT FONDAP 15130011 MAC, IW). Citation Format: Fernan Gomez-Valenzuela, Ignacio Wichmann, Felipe Suárez, Sumie Kato, Enrique Ossandón, Marcela Hermoso, Elmer Fernández, Mauricio A. Cuello. Cyclooxygenase-2 blockade is crucial to restore natural killer cell activity before anti-CTLA-4 therapy against high-grade serous ovarian cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 182.