Data from The CXCL12–CXCR4 Chemokine Pathway: A Novel Axis Regulates Lymphangiogenesis

<div>Abstract<p><b>Purpose:</b> Lymphangiogenesis, the growth of lymphatic vessels, contributes to lymphatic metastasis. However, the precise mechanism underlying lymphangiogenesis remains poorly understood. This study aimed to examine chemokine/chemokine receptors that directly contribute to chemoattraction of activated lymphatic endothelial cells (LEC) and tumor lymphangiogenesis.</p><p><b>Experimental Design:</b> We used quantitative RT-PCR to analyze specifically expressed chemokine receptors in activated LECs upon stimulation of vascular endothelial growth factor-C (VEGF-C). Subsequently, we established <i>in vitro</i> and <i>in vivo</i> models to show lymphangiogenic functions of the chemokine axis. Effects of targeting the chemokine axis on tumor lymphangiogenesis and lymphatic metastasis were determined in an orthotopic breast cancer model.</p><p><b>Results:</b> VEGF-C specifically upregulates CXCR4 expression on lymphangiogenic endothelial cells. Moreover, hypoxia-inducible factor-1α (HIF-1α) mediates the CXCR4 expression induced by VEGF-C. Subsequent analyses identify the ligand CXCL12 as a chemoattractant for LECs. CXCL12 induces migration, tubule formation of LECs <i>in vitro</i>, and lymphangiogenesis <i>in vivo</i>. CXCL12 also stimulates the phosphorylation of intracellular signaling Akt and Erk, and their specific antagonists impede CXCL12-induced chemotaxis. In addition, its level is correlated with lymphatic vessel density in multiple cancer tissues microarray. Furthermore, the CXCL12–CXCR4 axis is independent of the VEGFR-3 pathway in promoting lymphangiogenesis. Intriguingly, combined treatment with anti-CXCL12 and anti-VEGF-C antibodies results in additive inhibiting effects on tumor lymphangiogenesis and lymphatic metastasis.</p><p><b>Conclusions:</b> These results show the role of the CXCL12–CXCR4 axis as a novel chemoattractant for LECs in promoting lymphangiogenesis, and support the potential application of combined targeting of both chemokines and lymphangiogenic factors in inhibiting lymphatic metastasis. <i>Clin Cancer Res; 18(19); 5387–98. ©2012 AACR</i>.</p></div>