NT5E and breast cancer: The production of extracellular adenosine by tumor-derived CD73 promotes breast cancer metastasis to the lung through the activation of A2B adenosine receptors since the administration of anti-CD73 mAb can reduce the number of spontaneous lung metastases originating from the injection of breast cancer 4T1.2 cells into the mammary fat pad of female wild-type BALB/c mice [85].