Abstract: Tie2 expressing monocytes (TEMs) only present in human circulating blood and tumor organs, and have an important role in tumor angiogenesis and progression. TEMs are effectively recruited to tumors by angiopoietin 2 （Ang2） and hypoxia and then differentiate into macrophages, which promote the angiogenesis in experimental tumor models by providing paracrine support to nascent blood vessels. Studies show that TEMs are up-regulated in hepatocellular carcinoma, colorectal cancer, breast cancer, malignant glioma and other human cancers, which suggests that TEMs are conducive to diagnosis and prognosis of tumors. With the further research, TEMs are applied to deliver drugs which can obtain significant anti-tumor responses and inhibit metastasis with the ability of tumor-homing. Meanwhile, TEMs may also be a potential target for the anticancer drugs. However, the present researches indicate that the effects of TEMs in tumor microvessel density, clinical stage and prognosis are still questionable. Current works that aim at describing and predicting the concrete function of TEMs have attracted significant attention from researchers.

Key words: Angiogenesis, Neoplasms, Tie2 expressing monocytes, Angiopoietin 2