Abstract Pancreatic ductal adenocarcinoma (PDAC) remains a lethal cancer, with only 13% of patients surviving 5 years. The limited efficacy of anti-PD-1/PD-L1 therapies indicates that additional immunoregulatory pathways sustain the immunosuppressive tumor microenvironment (TME) that restricts T-cell infiltration. Our recent studies (Ravindranathan Nat Com 2022) demonstrated that combined blockade of vasoactive intestinal peptide (VIP) receptor (VPAC) and PD-1 signaling eradicated PDAC in ∼50% of mice, although the underlying mechanism of VPAC inhibition remains undefined. Therefore, we hypothesized that VPAC blockade reshapes the immune microenvironment to enhance antigen presentation and T cell responses to anti-PD1 immunotherapy in PDAC.To address this, we characterized the expression of VIP and VPAC on cancer cells, immune cells, and stromal cells in the PDAC TME. We studied the impact of VPAC signaling on the immune functions of myeloid/lymphoid cells and on the architecture of the TME using PDAC patient specimens, murine models, and relevant in vitro/ex vivo systems. Tumor growth kinetics were performed to assess the anti-tumor potential of VPAC blockade.In vitro secretome analysis showed that murine MT5 PDAC cells secrete more VIP than KPC-luc, consistent with their faster tumor-growth kinetics. To assess host-intrinsic VIP effects in TME we compared tumor progression in WT and vip-knockout (vip-ko) mice and found markedly slower growth in vip-ko mice, especially in females vs. males. To explore the cellular basis of the anti-tumor response, we depleted immune cell subsets and compared tumor growth kinetics in both female and male vip-ko mice. Depletion of CD8+ or CD4+ T cells and of CSF1R+ myeloid cells accelerated tumor growth in vip-ko mice, whereas clodronate depletion of phagocytic macrophages attenuated anti-tumor responses only in females. Androgen blockade (ARB) with degarelix restored male responsiveness to VPAC inhibition, highlighting androgen-driven resistance in male against VPAC blockade. Mechanistically, VIP from CD29+PD-L1+ fibroblasts suppressed macrophage phagocytosis of PDAC cells, while VIP loss restored this activity. Strikingly, AR activation further suppressed macrophage phagocytosis selectively in males. Mechanistically, TNF-α and MIF secreted from γδ-T cells and GZMK+CD8+ T cells, respectively, enhanced anti-tumor phagocytosis in female vip-ko mice. Combined AR blockade, anti-PD-1, VPAC antagonism, and taxotere markedly extended survival in WT male mice bearing orthotopic MT5 PDAC (MST 54 vs. 18 days for untreated control).These findings show that VPAC signaling restrains TNF-α– and MIF-dependent immune crosstalk and limits phagocytic PDAC clearance. These data also reveal androgen-suppressed phagocytosis as a driver of sexual dimorphism in response to VPAC antagonism and suggest translatable approaches for PDAC treatment. Citation Format: Sonia Mecorapaj, Tenzin Passang, Fanyuan Zeng, Zihan Chen, Shuhua Wang, Tuisha Gupta, Shayna Jankowski, Jian-Ming Li, Cynthia R. Giver, Swapnaa Balaji, Kiranj Chaudagar, Edmund K. Waller. Androgen-driven sexual dimorphism reshapes immune crosstalk and limits immunotherapy response in PDAC abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3441.
Mecorapaj et al. (Fri,) studied this question.