Figure 1.

Diverse outcomes of tumor-derived CCL2. CCL2 expression by mammary tumors can recruit and activate circulating tumor-activated neutrophils ('N1' TANs) to kill disseminated tumor cells. However, when these tumors are also producing factors such as transforming growth factor beta (TGFβ) and granulocytic colony-stimulating factor (GCSF), immature granulocytes such as granulocyte myeloid-derived suppressor cells (G-MDSC), 'N2' TANs and inflammatory monocytes are preferentially recruited in response to CCL2, and these cells in turn favor disseminated cell survival and proliferation. TAM, tumor-associated macrophage.