Pancreatic ductal adenocarcinoma (PDAC) is characterized by desmoplasia, with macrophages as one of the most abundant, multifunctional immune cell populations in the tumor microenvironment (TME) and a major component of the immune infiltrate. To best improve clinical outcomes, consideration must be placed on targeted therapeutics that blunt heterotypic interactions between tumor cells and supporting cells within the TME. Here, we provide new insight into the dichotomous relationship between epithelial and mesenchymal phenotypes of PDAC cells in 3D culture. We report the ability of PDAC mesenchymal cells to form vascular mimicry-like structures in a 3D in vitro assay of invasion. Additionally, we demonstrate that macrophages have the ability to impart a proinvasive phenotype to PDAC cells when co-cultured in 3D, irrespective of EMT (epithelial-to-mesenchymal transition) status. To elucidate a mechanism for this macrophage-mediated proinvasive phenotype, we employed an unbiased, multi-omics approach. First, PDAC cell lines and primary macrophages were CTAP (cell-type specific labeling using amino acid precursors) labeled and admixed together for a prolonged period of time. To identify cell of origin of novel RNA and proteins, these mixed co-cultures were FACS sorted for downstream RNA-sequencing analysis or harvested in bulk for downstream proteome and secretome analysis. Preliminary integration of cell culture transcriptomes with CTAP-TMT (tandem mass tag) proteomes and secretomes implicates several key epithelial- and macrophage-derived signaling molecules as principal instructing signals for mediating the observed proinvasive phenotype. Blockade of this signaling axis, by inhibition of the signaling molecules or their receptors, disrupted the crosstalk between the two cell types and impaired the ability of macrophages to impart a proinvasive phenotype to PDAC cells. These preliminary preclinical data, recapitulated in vivo, suggest that targeting the TME of patients by using a staging regimen of chemokine inhibitor to disrupt tumor-macrophage cell interactions, followed with therapeutic modalities such as gemcitabine (and/or immunotherapy), would improve upon standard of care and inform future treatment options for PDAC in the clinic.

Citation Format: Tony J. Wu, Oliver Cast, Danish Memon, Alejandro Jimenez-Sanchez, Anne Machel, Sebastian Kehrloesser, Michael B. Gill, Martin L. Miller. Identifying mechanisms of macrophage-mediated metastasis and therapy resistance in PDAC [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C65.