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Comment
. 2015 Jan;12(1):1-4.
doi: 10.1038/cmi.2014.83. Epub 2014 Sep 15.

The origin and function of tumor-associated macrophages

Yang Liu, Xuetao Cao
Comment

The origin and function of tumor-associated macrophages

Yang Liu et al. Cell Mol Immunol. 2015 Jan.
No abstract available

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Figures

Figure 1
Figure 1
Origin and differentiation of TAMs. TAMs originate from the circulating Ly6C+CCR2+ monocytes, which are derived from bone marrow hematopoietic stem cells. The inflammatory monocytes are recruited to the tumor tissues and then differentiate into TAMs. At the early stage of differentiation, the inflammatory monocytes exhibit an increase in CD11c and a decrease in Ly6C; this process involves RBPJ-mediated Notch signaling. However, at a relatively late stage of differentiation, RBPJ induces the upregulation of MHC-II and downregulation of CD11b, then the significant upregulation of Vcam1 on the inflammatory monocytes, finally driving the differentiation of the CCR2+ inflammatory monocytes to Ly6C−CD11c+MHCII+CD11bloVcam1+ TAMs that can further proliferate in the tumor tissue and mediate the suppression of T-cell immunity against cancer. TAM, tumor-associated macrophage.
Figure 2
Figure 2
Multiple functions of TAMs in tumor progression. TAMs can promote tumor progression in a variety of ways. Monocyte-derived, RBPJ-dependent TAMs can induce the expansion of PD-1+GzmB−CD8+ T cells in the tumor tissue to mediate immunosuppression; TAMs can inhibit the proliferation of effector T cells or recruit more Th2 or regulatory T cells to the tumor tissue to suppress the anti-tumor immune response. TAMs can release a large number of angiogenic factors, such as VEGF and PDGF, which can promote tumor angiogenesis. In addition, TAMs can secrete numerous growth factors, MMPs, which can work jointly to promote tumor cell proliferation, invasion and metastasis. MMP, matrix metalloproteinase; PDGF, platelet-derived growth factor; TAM, tumor-associated macrophage; VEGF, vascular endothelial growth factor.
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