Abstract B108: CXCR4 inhibition reprograms immune checkpoint networks and enhances anti-tumor immunity in patient-derived pancreatic cancer organoid–PBMC co-cultures
ILENIA PELLICCIOTTA, Gulam Manji, Alex Raufi, Emily AlouaniAbstract
Background:
Pancreatic ductal adenocarcinoma (PDAC) remains largely refractory to immunotherapy because of its immunosuppressive, T-cell–excluded microenvironment. Immune checkpoint blockade, alone or with chemotherapy, has shown limited efficacy, likely due to redundant suppressive pathways. CAF-derived CXCL12 acting through CXCR4 is a key mediator of immune exclusion. We recently demonstrated a 65% response rate in a small phase II trial combining gemcitabine-based chemotherapy, CXCR4 inhibition, and PD-1 blockade. To build on this activity, we developed a patient-specific ex vivo organoid model to define CXCL12/CXCR4-mediated immune regulation and identify additional cellular and molecular targets to enhance antitumor efficacy.
Methods:
Patient-derived tumor organoids (PDTOs) were established from surgical resections of treatment-naïve patients with pancreatic cancer and co-cultured with matched peripheral blood mononuclear cells (PBMCs). PBMC migration toward PDTOs was assessed in a three-dimensional co-culture system. Immune-cell activation and infiltration and tumor-cell apoptosis were evaluated by flow cytometry and immunofluorescence. The effects of the CXCR4 antagonist AMD3100 on immune checkpoint receptor expression in PBMCs and corresponding ligand expression in PDTOs were assessed alone and with immune checkpoint blockade.
Results:
Co-culture of PDAC patient–derived PBMCs with MiaPaCa-2 and PANC-1 cells and with allogeneic and autologous PDTOs reduced tumor cell numbers in the range of 3.5 to 4.9-fold. In contrast, PBMCs from healthy donors produced minimal tumor-cell killing. Relative to PBMC monoculture, patient-derived co-cultures increased activated CD69+ immune cells, including CD8+ T cells and CD56+ NK cells, with variable CD4+ T-cell activation; no lymphocyte activation was observed with healthy-donor PBMCs. AMD3100 pretreatment enhanced CD8+ T-cell migration toward autologous PDTOs in Matrigel and, following infiltration, increased PBMC proliferation and the abundance of activated T and NK cells expressing IFNγ, CD69, and granzyme B. CXCR4 inhibition also modulated PD-1, TIGIT, NKG2A, LAG-3, and TIM-3 expression in a patient-specific manner. PDAC-derived organoids expressed multiple immune-regulatory molecules, including PD-L1, TIGIT-L, HLA-E, CD73, FasL, IL-10, CXCL12, and calreticulin, indicating both checkpoint-dependent and soluble immune regulation. AMD3100 similarly altered checkpoint expression in PDTOs. Combined treatment of PBMCs and PDTOs with AMD3100 and PD-1 blockade further enhanced T-cell migration and activation and increased PDTO apoptosis, supporting the activity of this combination.
Conclusions:
Patient-specific PDTO–PBMC models demonstrate that CXCR4 inhibition enhances immune-cell infiltration and activation, modulates checkpoint expression, and promotes tumor-cell killing, supporting combined CXCR4 and PD-1 blockade. A randomized phase II trial evaluating this strategy with gemcitabine and nab-paclitaxel is ongoing.
Citation Format:
ILENIA PELLICCIOTTA, Gulam Manji, Alex Raufi, Emily Alouani. CXCR4 inhibition reprograms immune checkpoint networks and enhances anti-tumor immunity in patient-derived pancreatic cancer organoid–PBMC co-cultures [abstract]. In: Proceedings of the AACR Conference on Pancreatic Cancer: New Frontiers in Biology and Therapeutic Development; 2026 Sep 25-28; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(18_Suppl_2):Abstract nr B108.