Paricalcitol plus hydroxychloroquine enhances gemcitabine activity and induces mesenchymal to epithelial transition in pancreatic ductal adenocarcinoma: A single cell RNA-seq analysis.

Epithelial-mesenchymal transition (EMT) describes a process by which epithelial cells acquire mesenchymal properties associated with increased migration, invasion, and resistance to therapy. In pancreatic ductal adenocarcinoma (PDAC), targeting the molecular and intercellular communication pathways that drive EMT represents a promising therapeutic strategy. Here, we investigate the effects of combined treatment with gemcitabine (G), paricalcitol (P), and hydroxychloroquine (GPH) in KPC-Luc orthotopic mouse models of PDAC, using single-cell RNA sequencing (scRNA-seq), high-dimensional weighted gene co-expression network analysis (hdWGCNA), and cell-cell communication analysis. GPH treatment reduces EMT, which is associated with the downregulation of the essential gene fibronectin (Fn1). Collagen and Fn1 pathways co-expression decreases in GPH-treated KPC-Luc tumors. Cancer-associated fibroblasts (CAFs) appear dominant in collagen signaling, whereas macrophages mediate Fn1 signaling. GPH treatment reduces the expression interaction strength between ligands and receptors (collagen-integrin and Fn1-Cd44 or Fn1-Sdc4) compared to sham, PH, and G. Altogether, this study presents a comprehensive single-cell resolution map of the molecular and cellular mechanisms by which GPH treatment impairs EMT in PDAC, identifying potential therapeutic targets within the fibronectin and collagen signaling axes.