Abstract 4533: Lymphotoxin-mediated tumor immunosuppressive regulation in ovarian cancer recurrence

Abstract Background: Recurrence is the major leading cause of death in patients with ovarian cancer. We previously report that inflammatory cytokine, lymphotoxin, derived from ovarian cancer cells, stimulates chemokine expressions in stromal fibroblasts via lymphotoxin-beta receptor, LTBR. These lymphotoxin-driven reciprocal tumor-stromal interactions in turn promote ovarian cancer progression via chemokine receptor CXCR3. However, the role of lymphotoxin in tumor immune microenvironment (TIME) and its contribution to recurrence remain poorly understood. This study aims to investigate the immunosuppressive regulation mediated by tumor-derived lymphotoxin in relation to ovarian cancer recurrence. Methods: We determined the expression of a panel of immunosuppressive genes in a cohort of 202 primary ovarian cancer tissues, which included both high-risk (n=132) and low-risk (n=70) recurrence, using qPCR. Findings were validated by TCGA data analysis. Cell lines and syngeneic mouse models were used. Results: Using multiplex immunofluorescence staining (mIF), we identified IFN-γ+ CD8+ T cell infiltration in ovarian tumors from patients following neoadjuvant chemotherapy with paclitaxel. While paclitaxel did not directly affect PD-L1 expression, IFN-γ significantly upregulated both PD-L1 gene expression and surface protein expression in most of ovarian cancer cell lines (14/17) as demonstrated by qPCR and flow cytometry. Primary tumors from high-risk recurrence patients showed elevated expression of IFN-γ signature genes (IFNG, STAT1, CCL5, CXCL9, CXCL10, HLA-DRA, CD8A, LAG3) and lymphotoxin-associated genes (LTA, LTB, CCL5, CXCL10, CXCL11). In our mouse models, lymphotoxin (Lta/Ltb) overexpression activated the NF-κB pathway and significantly reduced survival (p=0.0018). In situ immune profiling and mIF revealed that lymphotoxin overexpression specifically enriched regulatory B cells and LAG3+CD3+CD8+ exhausted T cells in the tumor microenvironment. Analysis of TCGA data confirmed that patients with high lymphotoxin expression showed significantly elevated levels of IFN-γ signature genes (IFNG, STAT1, CXCL9), lymphotoxin-stimulated chemokines (CCL5, CXCL10, CXCL11), and immunosuppressive cell markers (CD244, LAG3, FOXP3, TGFB1, EOMES, GZMB, ICOS, IL10, CCL2). These findings were further validated at the protein level using mIF in patient samples, which showed increased LAG3+CD3+CD8+ T cells and CD20+ B cells in recurrent tumors. Conclusions: Our findings reveal that an immunosuppressive tumor microenvironment contributed to primary tumors from ovarian cancer patients with high recurrence risk. A distinct set of immunosuppressive regulators orchestrated by cancer-derived lymphotoxin through recruitment of B-regs and exhausted T cells suggests new therapeutic strategies targeting ovarian cancer recurrence. Citation Format: Zhewei Zhang, Kit Ying Chan, Ho Sze Jacqueline Lee, Joseph Kwong, Tat San Lau, Chi Chiu Wang. Lymphotoxin-mediated tumor immunosuppressive regulation in ovarian cancer recurrence [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4533.