Tie2-expressing monocytes (TEMs): novel targets and vehicles of anticancer therapy?
There is a growing interest in understanding the complex interactions between bone marrow-derived myeloid-lineage cells and angiogenesis in tumors. Such interest has been revived recently by the observation that tumor-infiltrating myeloid cells convey proangiogenic programs that can counteract the activity of antiangiogenic drugs in mouse tumor models. Among myeloid cells, Tie2-expressing monocytes (TEMs) appear to have nonredundant function in promoting tumor angiogenesis and growth in mouse models. The identification and functional characterization of TEMs in mice and humans may provide novel molecular targets for anticancer therapy. Moreover, TEMs may be exploited to deliver antitumor drugs specifically to the tumor microenvironment.