Thermal ablation is increasingly used for local control of pancreatic ductal adenocarcinoma (PDAC), but its capacity to induce systemic antitumor immunity and the mechanisms limiting this response remain incompletely defined. Using a bilateral LSL-Kras ^G12D/+; LSL-Trp53 ^R172H/+ ; Pdx1-Cre (KPC) flank tumor model, we show serial radiofrequency ablation (RFA) enhances local tumor control and induces a robust abscopal response. This effect was associated with increased activation of CD8⁺ T cells and natural killer cells, and was abrogated by CD8⁺ T cell depletion. Single-cell RNA sequencing revealed expansion of cytotoxic immune programs alongside induction of a CSF1R-driven myeloid response consistent with adaptive immune resistance. Although combinatorial blockade of PD-L1 and CD73 augmented systemic antitumor responses, and the addition of CSF1R inhibition in this context further enhanced both local and distant tumor control. These findings identify a CSF1R-dependent myeloid resistance program which constrains ablation-induced systemic immunity and demonstrate that rational combination immunotherapy can potentiate the systemic efficacy of tumor ablation in PDAC. STATEMENT OF TRANSLATIONAL RELEVANCE: Radiofrequency ablation is a local thermal therapy that induces tumor destruction and modulation of the tumor microenvironment used for treatment of many solid tumors, including pancreatic cancer. Serial thermal ablations induce a CD8+ T cells and NK cell antitumor immunological response; however, Nt5e (CD73) is increased in tumor cells, PD-1 is increased in CD8+ T cells, and serial ablations increase a CSF1R+ macrophage cluster in ablated tumors. Combinational targeting of CD73, PD-L1, and CSF1R alleviates CSF1R-dependent therapeutic resistance and enhances local and systemic tumor control. This study identifies targetable countervailing mechanisms to local ablation therapy and provides a rationale for combinatorial strategies integrating serial tumor ablation with systemic immunomodulatory agents. Future prospective studies should evaluate the influence of timing, dosage, and sequence of ablation on immune priming to improve clinical interventions in pancreatic cancer.

Dietary macronutrient composition has emerged as a key modulator of pancreatic tumorigenesis, yet the impact of lipid-rich diets, particularly ketogenic diets (KD), on the earliest stages of pancreatic cancer development remains unclear. To investigate how dietary lipids shape the initiation and progression of Kras-driven neoplasia, we examined the effects of a low-fat diet (LFD), high-fat diet (HFD), and KD in the Ptf1aCreERT2;KrasG12V (AcinarKrasG12V) mouse model. KD-fed mice showed the shortest survival (median 26 ± 7 days) compared with the standard diet (SD, 87 ± 29; P = 0.02) and LFD (57 ± 27; P = 0.02), whereas HFD-fed mice also exhibited reduced survival relative to SD (35 ± 25; P = 0.05). KD feeding was associated with severe glucose intolerance and elevated circulating β-hydroxybutyrate levels. Histologically, KD-fed AcinarKrasG12V mice developed invasive, sarcomatoid-like pancreatic ductal adenocarcinoma (PDAC), whereas HFD-fed mice showed increased poorly differentiated PDAC; in both groups, these aggressive tumors were associated with extensive fibrosis and increased stromal CD39 expression relative to tumor compartments. Proteomic analysis demonstrated activation of the PI3K–Akt–mTOR and EGFR signaling pathways in tumors from KD- and HFD-fed AcinarKrasG12V mice. Serum cytokine/chemokine profiling revealed a proinflammatory and proangiogenic milieu in KD-fed AcinarKrasG12V mice. Collectively, these results suggest that dietary lipid enrichment prior to oncogenic Kras activation is associated with accelerated early pancreatic neoplasia and a microenvironment conducive to tumor progression. These findings underscore the need for careful consideration of KD use in individuals at elevated risk for pancreatic cancer. Significance: This article evaluates the impact of KDs and HFDs prior to oncogenic Kras activation in the AcinarKrasG12V model. These findings reveal that lipid-rich diets accelerate PDAC progression and have important implications for dietary recommendations in individuals at elevated pancreatic cancer risk.

Pathologic evaluation of pancreatic tissue sections from AcinarKrasG12V mice under different diets.

Supplementary Table S1 shows the diet compositions.

Background/Objectives: Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with a desmoplastic, immunosuppressive tumor microenvironment enriched in extracellular adenosine. High adenosine levels disrupt anti-tumor immunity by engaging adenosine receptors on T cells, macrophages, and dendritic cells. In this context, strategies to reduce extracellular adenosine signaling within the TME are in focus. Among them, enzymatic degradation of extracellular adenosine levels has emerged as a promising approach to overcome immune suppression and restore anti-tumor immune responses. Methods: Here, we engineered an E. coli strain to express a surface-bound form of a bacterial ADA2 enzyme and used the outer membrane vesicles produced by this strain as nanoparticles carrying the functional enzyme. Our data indicate robust surface expression and enzymatic activity of ADA2 on OMV particles. Results: In a PDAC subcutaneous flank tumor model, intratumoral administration of OMV-ADA2 particles was associated with significantly increased infiltration of CD8⁺ T cells and Granzyme B expression and concomitant decreases in collagen deposition and α-smooth muscle actin (α-SMA) positive stromal cells, suggesting modulation of the desmoplastic stroma. Conclusions: These findings support further investigation of OMV–bADA2 as a potential platform to modulate tumor metabolism and stroma, activate anti-tumor immunity, and serve as a carrier for co-delivery of additional anticancer modalities in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a dense desmoplastic microenvironment that promotes therapeutic resistance and disease progression. Here, we investigated the impact of pulsed field ablation (PFA), a non-thermal electroporation-based therapy, on tumor and stromal remodeling in a syngeneic murine PDAC model. PFA induced rapid apoptotic and necrotic tumor cell death, transient neutrophil infiltration, and durable suppression of tumor growth. Single-cell RNA sequencing following repeated PFA treatments revealed enrichment of a classical secretory tumor cell state associated with complement and stress-response pathways and reduced epithelial-to-mesenchymal transition (EMT) programs. Although overall immune composition was largely unchanged, PFA markedly remodeled the stromal compartment, decreasing αSMA-positive activation and shifting cancer-associated fibroblasts (CAFs) from tumor-promoting myofibroblastic CAFs toward Dpp4 + complement-secreting CAFs. This transition was accompanied by increased IL-1 signaling potential, reduced Tgfb1 expression, and diminished tumor cell TGF-β response signatures. Serial PFA treatments further suppressed EMT-associated programs, identifying stromal reprogramming as a potential mechanism through which PFA enhances tumor control. Statement of Significance: PFA suppresses PDAC growth while reprogramming the tumor stroma. PFA shifts CAFs from myofibroblastic to Dpp4+ complement-secreting states, reduces TGF-β and EMT signaling, and promotes durable tumor control through stromal remodeling.