PDPN and breast cancer: Lactic acid, a metabolite released by cancer cells and found to be enriched in tumor-draining LNs of preclinical melanoma and breast cancer models, was identified to modulate FRC metabolism and mitochondrial function, leading to FRC activation as marked by upregulation of PDPN and Thy1 and downregulation of IL-7, without affecting survival and proliferation of FRCs (Riedel et al., 2022).