Integrated single cell RNA sequencing and flow cytometry analysis identifies elevated S100A6+ and S100A8+ myeloid subsets in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is among the most lethal malignancies, underscoring the need for minimally invasive biomarkers to support patient stratification and disease monitoring. In this study, we aimed to identify PDAC-associated immune signatures by reanalyzing a single-cell RNA-sequencing dataset and to validate key findings using flow cytometry in an independent cohort predominantly composed of advanced-stage PDAC. Analysis of peripheral blood mononuclear cells from patients with PDAC and healthy donors revealed increased expression of S100A6, S100A8, and S100A12, particularly within monocytes and dendritic cells. These transcriptional changes were confirmed at the protein level, demonstrating enrichment of S100A6+ monocytes, S100A6+/S100A8+ DCs, activated monocytes, and plasmacytoid DCs in PDAC. Univariate ROC analyses identified S100A6+ plasmacytoid DCs, S100A8+ plasmacytoid DCs, and CD14+CD86+S100A8+ monocytes as candidate PDAC-associated immune features. However, further validation incorporating benign pancreatic conditions and multivariable modeling is required before conclusions can be drawn regarding diagnostic specificity and clinical applicability.