Background: Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer-related death in the US. A key hallmark of this disease is that, while tumors initially show susceptibility to standard chemotherapeutic agents, most patients eventually develop resistance, leading to poor survival. While the mechanisms of chemoresistance are unclear, murine studies have implicated the myeloid compartment of the tumor immune microenvironment. Correlative data in human tumors supports this notion, however, mechanistic studies are lacking, thus impairing translation to the clinic. The study of human pancreatic cancer has historically been challenging due to difficulty of fresh biospecimen acquisition, patient heterogeneity, and a diverse tumor microenvironment. Moreover, the vast majority of pancreatic cancer patients do not qualify for surgical resection, further limiting tissue availability. We have overcome these difficulties by developing a pipeline to analyze human tumor samples and matched blood using high-fidelity techniques including single-cell RNA sequencing (scRNAseq) and mass cytometry (CyTOF), together with establishment of organoids from the same tumors. Notably, in this pipeline we can use small amounts of tissue from endoscopic fine needle biopsies, thus allowing us to sample tumors from patients at any disease stage. Results: We performed CyTOF on longitudinally-matched peripheral blood mononuclear cells (PBMCs) from 30 patients and single-cell RNA sequencing on 6 patients in the treatment naïve and on-treatment (FOLFIRINOX) state. CyTOF revealed distinct alterations in the myeloid population, with a shift toward CXCR2hiPD-L1hi granulocytes with FOLFIRINOX treatment over time. Analysis of PBMCs from scRNAseq showed a distinct myeloid gene signature with FOLFIRINOX and in particular highlighted interleukin-8 (IL8), a chemokine involved in myeloid cell chemotaxis that is associated with poor prognosis in pancreatic cancer. Further mapping of IL8 in tumor tissue by scRNAseq showed that it is highly expressed in subpopulations of tumor epithelial cells and tumor-infiltrating granulocytes. IL8-high tumor-infiltrating granulocytes also highly expressed VEGF and CXCR4, suggesting immunosuppressive and angiogenic roles. IL8-high tumor epithelial cells were found to have a basal-like phenotype and also expressed a network of other chemokines including CXCL1, CXCL3, CXCL5, which are known to recruit immunosuppressive myeloid cells. Conclusions: Through longitudinal and multimodal mapping using PDAC patient blood and tumor biospecimens, we have identified IL8 as a potential mediator of epithelial-myeloid crosstalk in PDAC chemoresistance and tumor aggression. Validation studies using an all-human co-culture system of PDAC patient-derived organoids and myeloid cells are currently underway.

Citation Format: Eileen S. Carpenter, Samantha Kemp, Padma Kadiyala, Nina Steele, Ahmed Elhossiny, Stephanie The, Valerie Gunchick, Rémy Nicolle, Michelle Anderson, Wenting Du, Carlos Espinoza, Richard Kwon, Erik-Jan Wamsteker, Anoop Prabhu, Allison Schulman, Vaibhav Sahai, Timothy Frankel, Filip Bednar, Marina Pasca di Magliano. Longitudinal profiling of pancreatic cancer patients identifies interleukin-8 as a mediator of myeloid-epithelial crosstalk [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-098.