TIE-2 expressing monocytes in human cancers

Abstract

Tumor-associated macrophages (TAM) are well known as a key player in the tumor microenvironment, which support cancer progression. More recently, a lineage of monocytes characterized by the expression of the TIE-2/Tek angiopoietin receptor identified a subset of circulating and tumor-associated monocytes endowed with proangiogenic activity. TIE-2 expressing monocytes (TEM) were found both in humans and mice. Here, we review the phenotypes and functions of TEM reported so far in human cancer and their potential use as markers of cancer progression and metastasis. Finally, we discuss the therapeutic approaches currently used or proposed to target TEM.

Standardization of sampling and sample preparation for analysis of human monocyte subsets in peripheral blood

“…Monocytes seem to be important in stem cell mobilisation and the regulation of hematopoiesis [409,464], and they are a part of the bone marrow stem cell niche [465,466]. A subset of monocytes characterised by the expression of the Tek tyrosine kinase receptor TIE-2 also seems important for the paracrine induction of angiogenesis in malignant diseases [467]. Such bone marrow cells have also been detected in various haematological malignancies [467]; in these cases, this monocyte subset seems to support the growth of malignant cells [467].…”

“…A subset of monocytes characterised by the expression of the Tek tyrosine kinase receptor TIE-2 also seems important for the paracrine induction of angiogenesis in malignant diseases [467]. Such bone marrow cells have also been detected in various haematological malignancies [467]; in these cases, this monocyte subset seems to support the growth of malignant cells [467]. Bone marrow monocytes may, thereby, support the survival and growth of myeloma stem cells [468].…”

Role of Angiopoietins in Development of Cancer and Neoplasia Associated with Viral Infection

“…However, as described earlier, Ang-2 directly interacts with monocytes and TEMs through both Tie-2 and integrin signaling [170][171][172]. These myeloid cells, once present in a KSHV infection microenvironment, rapidly differentiated into TAMs [157,173], which, as described earlier, are well known to promote tumor growth and progression [171,174,175]. Therefore, as shown in Figure 3, KSHV-induced Ang-2 plays a pivotal role in the development of KS by promoting both tumor angiogenesis and inflammation.…”

Expression pattern of immune- and cancer-associated genes in peripheral blood of mice bearing melanoma cells

“…RE changes were 2-3 fold. The Cd14 upregulation could be due to the infiltration of monocytes into tumor, and could serve as a marker for cancer progression and metastasizing [20,21].…”