Natural killer cells associate with epithelial cells in the pancreatic ductal adenocarcinoma tumor microenvironment.

Background: Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer. PDAC's poor prognosis and resistance to immunotherapy are attributed in part to its dense, fibrotic tumor microenvironment (TME), which is known to inhibit immune cell infiltration. We recently demonstrated that PDAC patients with higher natural killer (NK) cell content and activation have better survival rates. However, NK cell interactions in the PDAC TME have yet to be deeply studied. We show here that NK cells are present and active in the human PDAC TME. Methods: We used imaging mass cytometry (IMC) to assess NK cell content, function, and spatial localization in human PDAC samples. Then, we used CellChat, a tool to infer ligand-receptor interactions, on a human PDAC scRNAseq dataset to further define NK cell interactions in PDAC. Results: Spatial analyses showed for the first time that active NK cells are present in the PDAC TME, and both associate and interact with malignant epithelial cell ducts. We also found that fibroblast-rich, desmoplastic regions limit NK cell infiltration in the PDAC TME. CellChat analysis identified that the CD44 receptor on NK cells interacts with PDAC extracellular matrix (ECM) components such as collagen, fibronectin and laminin expressed by fibroblasts and malignant epithelial cells. This led us to hypothesize that these interactions play roles in regulating NK cell motility in desmoplastic PDAC TMEs. Using 2D and 3D in vitro assays, we found that CD44 neutralization significantly increased NK cell invasion through matrix. Conclusions: Targeting ECM-immune cell interactions may increase NK cell invasion into the PDAC TME.

Patterns of Failure Following Preoperative Chemotherapy and Stereotactic Body Radiation Therapy and Resection for Patients with Borderline Resectable or Locally Advanced Pancreatic Cancer.

BACKGROUND: The role of neoadjuvant stereotactic body radiation therapy (SBRT) in the treatment of pancreatic adenocarcinoma (PDAC) is controversial and the optimal target volumes and dose-fractionation are unclear. The aim of this study is to report on treatment outcomes and patterns of failure of patients with borderline resectable (BL) or locally advanced (LA) pancreatic cancer following preoperative chemotherapy and SBRT. METHODS: We conducted a single-institution, retrospective study of patients with BL or LA PDAC. Patients received neoadjuvant chemotherapy and SBRT was prescribed to 30 Gy over 5 fractions to the pancreas planning tumor volume (PTV). A subset of patients received a simultaneous integrated boost to the high risk vascular PTV and/or elective nodal irradiation (ENI). Following neoadjuvant chemoradiation, all patients underwent subsequent resection. Overall survival (OS), progression-free survival (PFS), locoregional recurrence-free survival (LRRFS), distant metastasis-free survival (DMPFS), and locoregional control (LRC) estimates were obtained using Kaplan-Meier analysis. RESULTS: Twenty-two patients with BL (18) or LA (4) PDAC were treated with neoadjuvant chemotherapy and SBRT followed by resection from 2011-2022. Following neoadjuvant treatment, 5 patients (23%) achieved a pathologic complete response (pCR) and 16 patients (73%) had R0 resection. At 24 months, there were no isolated locoregional recurrences (LRRs), 9 isolated distant recurrences (DRs), and 5 combined LRRs and DRs. Two LRRs were in-field, 2 LRRs were marginal, and 1 LRR was both in-field and marginal. 2-year median LRC, LRRFS, DMPFS, PFS, and OS were 77.3%, 45.5%, 31.8%, 31.8%, and 59.1%, respectively. For BL and LA cancers, 2-year LRC, DMPFS, and OS were 83% vs. 75%, (p = 0.423), 39% vs. 0% (p = 0.006), and 61% vs. 50% (p = 0.202), respectively. ENI was associated with improved LRC (p = 0.032) and LRRFS (p = 0.033). Borderline resectability (p = 0.018) and lower tumor grade (p = 0.027) were associated with improved DMPFS. CONCLUSIONS: Following preoperative chemotherapy and SBRT, locoregional failure outside of the target volume occurred in 3 of 5 recurrences; ENI was associated with improved LRC and LRRFS. Further studies are necessary to define the optimal techniques for preoperative radiation therapy.

The Role of Chemokines in Orchestrating the Immune Response to Pancreatic Ductal Adenocarcinoma.

Chemokines are small molecules that function as chemotactic factors which regulate the migration, infiltration, and accumulation of immune cells. Here, we comprehensively assess the structural and functional role of chemokines, examine the effects of chemokines that are present in the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME), specifically those produced by cancer cells and stromal components, and evaluate their impact on immune cell trafficking, both in promoting and suppressing anti-tumor responses. We further explore the impact of chemokines on patient outcomes in PDAC and their role in the context of immunotherapy treatments, and review clinical trials that have targeted chemokine receptors and ligands in the treatment of PDAC. Lastly, we highlight potential strategies that can be utilized to harness chemokines in order to increase cytotoxic immune cell infiltration and the anti-tumor effects of immunotherapy.

Phase 1 Study of Hypofractionated Proton Beam Radiation Therapy in Adjuvant Pancreatic Cancer (PROTON-PANC).

PURPOSE: Despite improvement in systemic therapy, patients with pancreatic ductal adenocarcinoma (PDAC) frequently experience local recurrence. We sought to determine the safety of hypofractionated proton beam radiation therapy (PBT) during adjuvant chemotherapy. METHODS AND MATERIALS: Nine patients were enrolled in a single-institution phase 1 trial (NCT03885284) between 2019 and 2022. Patients had PDAC of the pancreatic head and underwent R0 or R1 resection and adjuvant modified FOLFIRINOX (mFFX) chemotherapy. The primary endpoint was to determine the dosing schedule of adjuvant PBT (5 Gy × 5 fractions) using limited treatment volumes given between cycles 6 and 7 of mFFX. Patients received PBT on days 15 to 19 in a 28-day cycle before starting cycle 7 (dose level 1, DL1) or on days 8 to 12 in a 21-day cycle before starting cycle 7 (DL2). RESULTS: The median patient age was 66 years (range, 52-78), and the follow-up time from mFFX initiation was 12.5 months (range, 6.2-37.4 months). No patients received preoperative therapy. Four had R1 resections and 5 had node-positive disease. Three patients were enrolled on DL1 and 6 patients on DL2. One dose-limiting toxicity (DLT) occurred at DL2 (prolonged grade 3 neutropenia resulting in discontinuation of mFFX after cycle 7). No other DLTs were observed. Four patients completed 12 cycles of mFFX (range, 7-12; median, 11). No patients have had local recurrence. Five of 9 patients had recurrence: 3 in the liver, 1 in the peritoneum, and 1 in the bone. Six patients are still alive, 4 of whom are recurrence-free. The median time to recurrence was 12 months (95% CI, 4 to not reached [NR]), and median overall survival was NR (95% CI, 6 to NR; 2-year survival rate, 57%). CONCLUSIONS: PBT integrated within adjuvant mFFX was well tolerated, and no local recurrence was observed. These findings warrant further exploration in a phase 2 trial.

Antibody dependent cell-mediated cytotoxicity selection pressure induces diverse mechanisms of resistance.

Targeted monoclonal antibody therapy has emerged as a powerful therapeutic strategy for cancer. However, only a minority of patients have durable responses and the development of resistance remains a major clinical obstacle. Antibody-dependent cell-mediated cytotoxicity (ADCC) represents a crucial therapeutic mechanism of action; however, few studies have explored ADCC resistance. Using multiple in vitro models of ADCC selection pressure, we have uncovered both shared and distinct resistance mechanisms. Persistent ADCC selection pressure yielded ADCC-resistant cells that are characterized by a loss of NK cell conjugation and this shared resistance phenotype is associated with cell-line dependent modulation of cell surface proteins that contribute to immune synapse formation and NK cell function. We employed single-cell RNA sequencing and proteomic screens to interrogate molecular mechanisms of resistance. We demonstrate that ADCC resistance involves upregulation of interferon/STAT1 and DNA damage response signaling as well as activation of the immunoproteasome. Here, we identify pathways that modulate ADCC sensitivity and report strategies to enhance ADCC-mediated elimination of cancer cells. ADCC resistance could not be reversed with combinatorial treatment approaches. Hence, our findings indicate that tumor cells utilize multiple strategies to inhibit NK cell mediated-ADCC. Future research and development of NK cell-based immunotherapies must incorporate plans to address or potentially prevent the induction of resistance.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

SUMMARY: Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

SUMMARY: Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

AACR Cancer Centers Alliance: Fostering Collaboration and Innovation to Advance Lifesaving Scientific Discoveries for Patients.

Basic and clinical cancer research discoveries stemming from the nation's cancer centers have markedly improved outcomes for many cancer patients. Despite this forward momentum in our progress against this complex disease, cancer in all its forms remains a major public health challenge that touches the lives of nearly every American, either directly or indirectly. The newly formed AACR Cancer Centers Alliance will accelerate the pace of discovery by providing an ongoing mechanism for transferring new knowledge, sharing resources, developing national demonstration projects, and driving innovation that impacts cancer science, cancer care delivery, and science and health policy.

Phase III Prospectively Randomized Trial of Perioperative 5-FU After Curative Resection for Colon Cancer: An Intergroup Trial of the ECOG-ACRIN Cancer Research Group (E1292).

BACKGROUND: Studies suggest that adjuvant chemotherapy should be initiated at the earliest possible time. The Eastern Cooperative Oncology Group (ECOG) and Intergroup evaluated the effect of perioperative fluorouracil (5-FU) on overall survival (OS) for colon cancer. PATIENTS AND METHODS: This phase III trial randomized patients to receive continuous infusional 5-FU for 7 days starting within 24 h after curative resection (arm A) or no perioperative 5-FU (arm B). Patients with Dukes' B3 and C disease received adjuvant chemotherapy per standard of care. The primary endpoint of the trial was overall survival in patients with Dukes' B3 and C disease. The secondary objective was to determine whether a week of perioperative infusion would affect survival in patients with Dukes' B2 colon cancer with no additional chemotherapy. RESULTS: From August 1993 to May 2000, 859 patients were enrolled and 855 randomized (arm A: 427; arm B: 428). The trial was terminated early due to slow accrual. The median follow-up is 15.4 years (0.03-20.3 years). Among patients with Dukes' B3 and C disease, there was no statistically significant difference in OS [median 10.3 years (95% CI 8.4, 13.2) for perioperative chemotherapy and 9.3 years (95% CI 5.7, 12.3) for no perioperative therapy, one-sided log-rank p = 0.178, HR = 0.88 (95% CI 0.66, 1.16)] or disease-free survival (DFS). For patients with Dukes' B2 disease, there was also no significant difference in OS (median 16.1 versus 12.9 years) or DFS. There was no difference between treatment arms in operative complications. One week of continuous infusion of 5-FU was tolerable; 18% of arm A patients experienced grade 3 or greater toxicity.

The Next Generation of Cellular Immunotherapy: Chimeric Antigen Receptor-Natural Killer Cells.

The advent of chimeric antigen receptor (CAR) engineering has led to the development of powerful cellular therapies for cancer. CAR T cell-based treatments have had notable clinical success, but logistical issues and associated toxicities are recognized limitations. There is emerging interest in using other immune effector cell types for CAR therapy. Natural killer (NK) cells are part of the innate immune system, and these lymphocytes play major roles in immunosurveillance and antitumor immune responses. Incorporating CARs into NK cells provides the opportunity to harness and enhance their innate cytotoxic potential toward malignancies. In this review, we discuss the production of CAR-engineered NK cells, highlight data on their preclinical and clinical efficacy, and examine the obstacles and strategies to overcome them.

DPP inhibition alters the CXCR3 axis and enhances NK and CD8+ T cell infiltration to improve anti-PD1 efficacy in murine models of pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is projected to be the second leading cause of cancer death in the USA by 2030. Immune checkpoint inhibitors fail to control most PDAC tumors because of PDAC's extensive immunosuppressive microenvironment and poor immune infiltration, a phenotype also seen in other non-inflamed (ie, 'cold') tumors. Identifying novel ways to enhance immunotherapy efficacy in PDAC is critical. Dipeptidyl peptidase (DPP) inhibition can enhance immunotherapy efficacy in other cancer types; however, the impact of DPP inhibition on PDAC tumors remains unexplored. METHODS: We examined the effects of an oral small molecule DPP inhibitor (BXCL701) on PDAC tumor growth using mT3-2D and Pan02 subcutaneous syngeneic murine models in C57BL/6 mice. We explored the effects of DPP inhibition on the tumor immune landscape using RNAseq, immunohistochemistry, cytokine evaluation and flow cytometry. We then tested if BXCL701 enhanced anti-programmed cell death protein 1 (anti-PD1) efficacy and performed immune cell depletion and rechallenged studies to explore the relevance of cytotoxic immune cells to combination treatment efficacy. RESULTS: In both murine models of PDAC, DPP inhibition enhanced NK and T cell immune infiltration and reduced tumor growth. DPP inhibition also enhanced the efficacy of anti-PD1. The efficacy of dual anti-PD1 and BXCL701 therapy was dependent on both CD8+ T cells and NK cells. Mice treated with this combination therapy developed antitumor immune memory that cleared some tumors after re-exposure. Lastly, we used The Cancer Genome Atlas (TCGA) to demonstrate that increased NK cell content, but not T cell content, in human PDAC tumors is correlated with longer overall survival. We propose that broad DPP inhibition enhances antitumor immune response via two mechanisms: (1) DPP4 inhibition increases tumor content of CXCL9/10, which recruits CXCR3+ NK and T cells, and (2) DPP8/9 inhibition activates the inflammasome, resulting in proinflammatory cytokine release and Th1 response, further enhancing the CXCL9/10-CXCR3 axis. CONCLUSIONS: These findings show that DPP inhibition with BXCL701 represents a pharmacologic strategy to increase the tumor microenvironment immune cell content to improve anti-PD1 efficacy in PDAC, suggesting BXCL701 can enhance immunotherapy efficacy in 'cold' tumor types. These findings also highlight the potential importance of NK cells along with T cells in regulating PDAC tumor growth.

Transfer learning between preclinical models and human tumors identifies a conserved NK cell activation signature in anti-CTLA-4 responsive tumors.

BACKGROUND: Tumor response to therapy is affected by both the cell types and the cell states present in the tumor microenvironment. This is true for many cancer treatments, including immune checkpoint inhibitors (ICIs). While it is well-established that ICIs promote T cell activation, their broader impact on other intratumoral immune cells is unclear; this information is needed to identify new mechanisms of action and improve ICI efficacy. Many preclinical studies have begun using single-cell analysis to delineate therapeutic responses in individual immune cell types within tumors. One major limitation to this approach is that therapeutic mechanisms identified in preclinical models have failed to fully translate to human disease, restraining efforts to improve ICI efficacy in translational research. METHOD: We previously developed a computational transfer learning approach called projectR to identify shared biology between independent high-throughput single-cell RNA-sequencing (scRNA-seq) datasets. In the present study, we test this algorithm's ability to identify conserved and clinically relevant transcriptional changes in complex tumor scRNA-seq data and expand its application to the comparison of scRNA-seq datasets with additional data types such as bulk RNA-seq and mass cytometry. RESULTS: We found a conserved signature of NK cell activation in anti-CTLA-4 responsive mouse and human tumors. In human metastatic melanoma, we found that the NK cell activation signature associates with longer overall survival and is predictive of anti-CTLA-4 (ipilimumab) response. Additional molecular approaches to confirm the computational findings demonstrated that human NK cells express CTLA-4 and bind anti-CTLA-4 antibodies independent of the antibody binding receptor (FcR) and that similar to T cells, CTLA-4 expression by NK cells is modified by cytokine-mediated and target cell-mediated NK cell activation. CONCLUSIONS: These data demonstrate a novel application of our transfer learning approach, which was able to identify cell state transitions conserved in preclinical models and human tumors. This approach can be adapted to explore many questions in cancer therapeutics, enhance translational research, and enable better understanding and treatment of disease.

A Grant-Based Experiment to Train Clinical Investigators: The AACR/ASCO Methods in Clinical Cancer Research Workshop.

To address the need for clinical investigators in oncology, American Association for Cancer Research (AACR) and American Society for Clinical Oncology (ASCO) established the Methods in Clinical Cancer Research Workshop (MCCRW). The workshop's objectives were to: (i) provide training in the methods, design, and conduct of clinical trials; (ii) ensure that clinical trials met federal and international ethical guidelines; (iii) evaluate the effectiveness of the workshop; and (iv) create networking opportunities for young investigators with mentoring senior faculty. Educational methods included: (i) didactic lectures, (ii) Small Group Discussion Sessions, (iii) Protocol Development Groups, and (iv) one-on-one mentoring. Learning focused on the development of an Institutional Review Board (IRB)-ready protocol, which was submitted on the last day of the workshop. Evaluation methods included: (i) pre- and postworkshop tests, (ii) students' workshop evaluations, (iii) faculty's ratings of protocol development, (iv) students' productivity in clinical research after the workshop, and (v) an independent assessment of the workshop. From 1996 to 2014, 1,932 students from diverse backgrounds attended the workshop. There was a significant improvement in the students' level of knowledge from the pre- to the postworkshop exams (P < 0.001). Across the classes, student evaluations were very favorable. At the end of the workshop, faculty rated 92% to 100% of the students' protocols as ready for IRB submission. Intermediate and long-term follow-ups indicated that more than 92% of students were actively involved in patient-related research, and 66% had implemented five or more protocols. This NCI-sponsored MCCRW has had a major impact on the training of clinicians in their ability to design and implement clinical trials in cancer research.

Status of Cancer Care at Network Sites of the Nation's Academic Cancer Centers.

BACKGROUND: Cancer care coordination across major academic medical centers and their networks is evolving rapidly, but the spectrum of organizational efforts has not been described. We conducted a mixed-methods survey of leading cancer centers and their networks to document care coordination and identify opportunities to improve geographically dispersed care. METHODS: A mixed-methods survey was sent to 91 cancer centers in the United States and Canada. We analyzed the number and locations of network sites; access to electronic medical records (EMRs); clinical research support and participation at networks; use of patient navigators, care paths, and quality measures; and physician workforce. Responses were collected via Qualtrics software between September 2017 and December 2018. RESULTS: Of the 69 responding cancer centers, 74% were NCI-designated. Eighty-seven percent of respondents were part of a matrix health system, and 13% were freestanding. Fifty-six reported having network sites. Forty-three respondents use navigators for disease-specific populations, and 24 use them for all patients. Thirty-five respondents use ≥1 types of care path. Fifty-seven percent of networks had complete, integrated access to their main center's EMRs. Thirty-nine respondents said the main center provides funding for clinical research at networks, with 22 reporting the main center provides all funding. Thirty-five said the main center provided pharmacy support at the networks, with 15 indicating the main center provides 100% pharmacy support. Certification program participation varied extensively across networks. CONCLUSIONS: The data show academic cancer centers have extensive involvement in network cancer care, often extending into rural communities. Coordinating care through improved clinical trial access and greater use of patient navigation, care paths, coordinated EMRs, and quality measures is likely to improve patient outcomes. Although it is premature to draw firm conclusions, the survey results are appropriate for mapping next steps and data queries.

Understanding and Targeting Natural Killer Cell-Cancer-Associated Fibroblast Interactions in Pancreatic Ductal Adenocarcinoma.

Interactions between natural killer (NK) cells and cancer-associated fibroblasts (CAFs) comprise a relevant but relatively understudied crosstalk relationship within the tumor microenvironment (TME). This review discusses the relevance of both natural killer cell and cancer-associated fibroblast function and activity in cancers, with an emphasis on pancreatic ductal adenocarcinoma (PDAC), incorporating additional insights from other malignancies to inform future directions for research. We describe what is currently known about NK cell-CAF crosstalk and their molecular interactions, how it is possible to exploit NK cell cytotoxicity in tumors and how to target CAFs to enhance efficacy of cancer therapies and cytotoxic immune cells. Although not previously tested in combination, there is an abundance of evidence demonstrating that targeting tumor-promoting CAFs and exploiting NK cells, separately, are beneficial as therapeutic strategies. This raises the possibility that a novel combination regimen addressing these two cell targets may be even more beneficial to eradicate PDAC and other solid tumors.

Antitumor T-cell Immunity Contributes to Pancreatic Cancer Immune Resistance.

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer death in the United States. Pancreatic tumors are minimally infiltrated by T cells and are largely refractory to immunotherapy. Accordingly, the role of T-cell immunity in pancreatic cancer has been somewhat overlooked. Here, we hypothesized that immune resistance in pancreatic cancer was induced in response to antitumor T-cell immune responses and that understanding how pancreatic tumors respond to immune attack may facilitate the development of more effective therapeutic strategies. We now provide evidence that T-cell-dependent host immune responses induce a PDAC-derived myeloid mimicry phenomenon and stimulate immune resistance. Three KPC mouse models of pancreatic cancer were used: the mT3-2D (Kras+/LSL-G12D; Trp53+/LSL-R172H; Pdx1-Cre) subcutaneous and orthotopic models, as well as the KP1 (p48-CRE/LSL-Kras/Trp53 flox/flox ) subcutaneous model. KPC cancer cells were grown in immunocompetent and immunodeficient C57BL/6 mice and analyzed to determine the impact of adaptive immunity on malignant epithelial cells, as well as on whole tumors. We found that induced T-cell antitumor immunity, via signal transducer and activator of transcription 1 (STAT1), stimulated malignant epithelial pancreatic cells to induce the expression of genes typically expressed by myeloid cells and altered intratumoral immunosuppressive myeloid cell profiles. Targeting the Janus Kinase (JAK)/STAT signaling pathway using the FDA-approved drug ruxolitinib overcame these tumor-protective responses and improved anti-PD-1 therapeutic efficacy. These findings provide future directions for treatments that specifically disable this mechanism of resistance in PDAC.