Ecto-5′-nucleotidase (CD73) promotes tumor angiogenesis

Angiogenesis is essential for tumor growth, progression and metastasis. Studies indicate that expression and activity of ecto-5′-nucleotidase (CD73) are elevated in metastatic carcinomas. Our previous studies found that angiogenesis of tumor xenografts was decreased when the activity of CD73 in cancer cells was inhibited, implying that this enzyme is involved in tumor angiogenesis. To elucidate the mechanism, we investigated CD73 influence on tumor angiogenesis in both in vitro assays and in tumor bearing mice. We found that capillary-like structures were formed more in CD73+/+ pulmonary microvascular endothelial cells (PMECs) than CD73−/− PMECs, and this was more pronounced when the cells were cultured in cancer-conditioned medium. Meanwhile, CD73 decreased endothelial cells adhesion to collagen IV and promoted migration. Additionally, the extent of tumor angiogenesis and the size of tumors were greater in CD73+/+ mice than in CD73−/− mice. Thus, we concluded that CD73 can promote endothelial cells forming new vessels in cancer condition, facilitating tumor growth and hematogenous metastasis.