Lactate-activated macrophages induced aerobic glycolysis and epithelial-mesenchymal transition in breast cancer by regulation of CCL5-CCR5 axis: a positive metabolic feedback loop

Aberrant energy metabolism is critical for cancer progression. Tumor-associated macrophages (TAMs) can stimulate tumor angiogenesis and enhance cancer metastasis; however, the metabolic interaction between cancer cells and macrophages characterized by lactate shuttles remains unclear. Here, we showed that lactate activated human macrophages to a TAM-like phenotype and stimulated the secretion of CCL5 by activation of Notch signaling in macrophages. Reciprocally, CCL5 increased cell migration, induced cancer cell EMT, and promoted aerobic glycolysis in breast cancer cells, suggesting a positive metabolic feedback loop in the co-culture system. Inhibition of CCR5, the cognate receptor of CCL5, or neutralization of CCL5, broke the metabolic loop and decreased cancer cell migration and EMT. Inhibition of aerobic glycolysis significantly reduced breast cancer cell EMT, indicated that aerobic glycolysis was necessary for the invasive phenotype of cancer cells. We further showed that TGF-β signaling regulated the expression of CCR5 in the co-culture system, and CCL5 induced glycolysis by mediation of AMPK signaling. The expression of CCL5-CCR5 axis was highly associated with macrophage infiltration, TGF-β and p-AMPK in clinical samples. CCL5-CCR5 axis promoted breast cancer metastasis in vivo. Our findings suggested a pivotal role of CCL5-CCR5 axis in the metabolic communication between cancer cells and macrophages.