Plasmacytoid dendritic cells are guided into tumors by chemokine gradients produced by malignant and stromal cells. Key chemokine axes implicated in this trafficking determine whether pDCs amplify antitumor immunity or become tolerogenic actors that support immune evasion. Evidence from reviews and experimental studies identifies several recurrent pathways and links them to functional outcomes in different cancers.
Chemokine axes that recruit pDCs
Major pathways include CXCL12-CXCR4, CXCL9/CXCL10/CXCL11-CXCR3, and lymphoid homing via CCL19/CCL21-CCR7. Marco Swiecki and Andrea Colonna at Washington University School of Medicine describe pDC expression of CXCR4 and responsiveness to CXCL12, a chemokine often upregulated in tumor stroma. Studies by Sophie Wittamer at Université Libre de Bruxelles identified chemerin and its receptor CMKLR1 as additional chemoattractant signals relevant to plasmacytoid dendritic cell recruitment in inflamed tissues, and chemerin has been detected in some tumor microenvironments. Tumor production of CXCL9, CXCL10, and CXCL11 can also attract CXCR3-expressing pDC subsets during inflammatory responses, while CCR7-dependent cues direct pDCs toward lymphoid structures associated with tumors.
Causes, relevance, and consequences
Tumor cells and associated fibroblasts release chemokines in response to hypoxia, oncogenic signaling, and cytokine stimulation; these conditions vary by tumor type and geographic or environmental exposures and shape local chemokine landscapes. Research from Laurence Zitvogel at Institut Gustave Roussy and collaborators links pDC infiltration in ovarian and other cancers to a shift from type I interferon production toward immunoregulatory functions, including indoleamine 2,3-dioxygenase expression and induction of regulatory T cells. The consequence is often suppressed cytotoxic T cell activity and poorer clinical outcomes in contexts where pDCs are skewed to tolerance rather than antiviral-like activation.
pDC recruitment therefore reflects a balance between inflammatory and tolerogenic signals: the same chemokine axes that enable beneficial antiviral or antitumor responses can, in specific tumor microenvironments, seed a population of pDCs that promotes immune escape. Therapeutic strategies targeting CXCL12-CXCR4 signaling or modulating chemerin pathways are under investigation to alter pDC localization and function, with the aim of restoring effective antitumor immunity while respecting the diverse cultural and tissue-specific contexts in which tumors arise.