Abstract A045: Amphiregulin neutralization reduces tumor burden and combats immunosuppression within the ovarian tumor microenvironment

Abstract Background: High grade serous ovarian cancer (HGSOC) patient response rates to clinically available immunotherapies have been low. In an effort to identify new clinically relevant immune targets in HGSOC, our group discovered that amphiregulin (AREG), a low affinity epidermal growth factor receptor (EGFR) ligand is significantly upregulated in post-neoadjuvant chemotherapy (NACT), treated HGSOC tumors, associated with chemoresistant disease, and compromises cytotoxic responses within the ovarian tumor immune microenvironment (OTIME). Furthermore, we have demonstrated that targeting AREG in combination with NACT led to a synergistic reduction in tumor burden in an HGSOC immunocompetent in vivo model. Objective: The purpose of this study was to evaluate tumorigenic and immunogenic adaptations that result from AREG neutralization. Methods: ID8p53-/- cells were administered intraperitoneally in C57/BL6 mice. 20 days post-inoculation, mice were treated three times with either a commercially available AREG neutralizing antibody (nab) (33ug) or respective IgG control. 7-days post-mortem all mice were euthanized, and tumors and serum were collected. Serum was submitted for multiplex cytokine/chemokine analysis to Eve Technologies. Intratumoral immunogenic and tumorigenic adaptations were evaluated by fluorescent immunohistochemistry, qPCR, or western blot. A cell viability analysis was employed to compare differences in synergism between a combinatorial AREG nab and chemotherapy treatment versus combinatorial gefitinib and chemotherapy treatment in the HGSOC chemoresistant cell line, PEA2. Finally, real-world patient data was employed to uncover how intratumoral AREG expression relates to HGSOC patient survival outcomes and somatic mutation profiles. Results: Mice treated with an AREG nab compared with an IgG control had a noteworthy reduction in tumor weight (p=0.065). Furthermore, mice treated with an AREG nab had significantly higher levels of CD8+ T cells (p<0.05). Moreover, intratumoral tumors treated with an AREG nab exhibited significantly lower (p<0.05) levels of p-ERK, PD-L1 and IL-6, all factors that are downstream of the EGFR pathway. Multiplex serum analysis revealed a significant (p<0.005) reduction in IL-1α in AREG nab treated mice. Cell viability analysis of PEA2 cells uncovered that unlike combinatorial treatment with an AREG nab and carboplatin which significantly reduced cell death compared to either AREG nab or carboplatin treatment alone, no significant synergism was observed with gefitinib. Finally, it was found that lower AREG expression is associated with improved progression-free survival and that basal AREG levels are highest in homologous recombination proficient and CCNE1 amplified HGSOC subtypes. Conclusions: AREG neutralization reduces tumor burden and immunosuppression within the OTIME. Furthermore, AREG neutralization, unlike EGFR synergizes with NACT. Future directions include testing a mono and dual AREG blockade with NACT in in vivo models that recapitulate the heterogenous nature of HGSOC disease. Citation Format: Angelica J. Salaverria, Julia McAdams, Payton De la Cruz, Julia Salinaro, Paul DiSilvestro, Nicole E. James, Cara Mathews. Amphiregulin neutralization reduces tumor burden and combats immunosuppression within the ovarian tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr A045.