The Calcineurin-NFAT-Angiopoietin-2 Signaling Axis in Lung Endothelium Is Critical for the Establishment of Lung Metastases

• Calcineurin-NFAT is activated in lung endothelium of the premetastatic niche
• Calcineurin-NFAT signaling upregulates ANG2 promoting the angiogenic switch
• Hyperactivation of calcineurin in Dscr1−/− mice leads to increased lung metastases
• Inhibiting calcineurin or ANG2 blocks endothelial activation and lung metastases

SummaryThe premetastatic niche is a predetermined site of metastases, awaiting the influx of tumor cells. However, the regulation of the angiogenic switch at these sites has not been examined. Here, we demonstrate that the calcineurin and nuclear factor of activated T cells (NFAT) pathway is activated specifically in lung endothelium prior to the detection of tumor cells that preferentially metastasize to the lung. Upregulation of the calcineurin pathway via deletion of its endogenous inhibitor Dscr1 leads to a significant increase in lung metastases due to increased expression of a newly identified NFAT target, Angiopoietin-2 (ANG2). Increased VEGF levels specifically in the lung, and not other organ microenvironments, trigger a threshold of calcineurin-NFAT signaling that transactivates Ang2 in lung endothelium. Further, we demonstrate that overexpression of DSCR1 or the ANG2 receptor, soluble TIE2, prevents the activation of lung endothelium, inhibiting lung metastases in our mouse models. Our studies provide insights into mechanisms underlying angiogenesis in the premetastatic niche and offer targets for lung metastases.

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