TEK and brain neoplasm: Albeit TEMs compose a minor subset of TAMs, they have been found to be highly relevant in promoting tumor angiogenesis because TEM depletion experiments using antibody-mediated neutralization of the Tie2 ligand Ang2 or Tie2 promoter-driven thymidine kinase both reduced angiogenesis and tumor propagation in mammary, pancreatic neuroendocrine and brain tumor mouse models (76, 77).