Identifying mechanisms of macrophage-mediated metastasis and treatment resistance in pancreatic cancer

Abstract

Abstract Background Pancreatic ductal adenocarcinoma (PDAC) is a lethal, incurable disease and desmoplasia is one of its fundamental characteristics. Though a significant body of literature has been published regarding the disease, mechanisms for PDAC progression, invasion and metastasis still remain unclear. Stromal elements have been demonstrated to serve both pro- and anti-tumoural functions. Macrophages, one of the most abundant immune cell populations in the tumour microenvironment (TME), are a major component of the immune infiltrate in PDAC. Methods Employing a multi-omics approach, PDAC cell lines and primary macrophages were CTAP (cell-type specific labelling using amino acid precursors)-labelled 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 Tandem mass tag (TMT)- proteome and secretome analysis. Results 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 pro-invasive phenotype to PDAC cells when co-cultured in 3D, regardless of EMT status. Preliminary integration of cell culture transcriptomes with CTAP-TMT proteomes and secretomes implicates several key epithelial- and macrophage-derived signalling molecules as principal instructing signals for mediating the observed pro-invasive phenotype. Conclusion Blockade of these signalling molecules or their receptors disrupted the crosstalk between PDAC cells and macrophages within the TME and impaired the ability of macrophages to induce a pro-invasive phenotype to PDAC cells. Legal entity responsible for the study The author. Funding Has not received any funding. Disclosure The author has declared no conflicts of interest.