P2RY6+ tumor-associated macrophages as a therapeutic target: suppressing tumor growth and enhancing chemosensitivity in triple-negative breast cancer

Background: Triple-negative breast Cancer (TNBC) harbors an immunosuppressive tumor microenvironment dominated by tumor-associated macrophages (TAMs). P2RY6, a UDP-sensitive purinergic receptor, is implicated in immune modulation, but its functional role in TNBC TAMs remains elusive.

Methods: The clinical relevance of P2RY6⁺ TAMs was assessed via bioinformatics, tissue microarrays, and survival analysis. In vitro, P2RY6 function in macrophage polarization, signaling, and paracrine regulation of TNBC cells was evaluated using genetic/pharmacological approaches, RNA Sequencing, calcium imaging, and secretome analysis. The downstream effector S100A9 and its receptor (TLR4/RAGE)-NF-κB axis in TNBC cells were validated. Orthotopic TNBC mouse models were used to evaluate therapeutic targeting of P2RY6 and S100A9 in vivo.

Results: P2RY6⁺ TAM infiltration correlates with poor prognosis in TNBC patients. UDP activation of P2RY6 drives M2-like macrophage polarization via the PLC-IP3-Ca²⁺/CREB1 pathway, leading to transcriptional upregulation and secretion of S100A9. Macrophage-derived S100A9 binds TLR4/RAGE on TNBC cells, activates NF-κB signaling, and promotes tumor proliferation. Genetic or pharmacological inhibition of P2RY6, or neutralization of S100A9, suppresses TNBC growth in vitro and in vivo, and synergizes with chemotherapy to enhance antitumor efficacy.

Conclusions: Our study unveils a UDP-P2RY6-S100A9 paracrine axis wherein P2RY6⁺ TAMs foster an immunosuppressive and pro-tumorigenic niche in TNBC. This axis represents a novel therapeutic target to disrupt TAM-tumor crosstalk and overcome chemoresistance in TNBC.