Myeloid Cells in Cancer Progression: Unique Subtypes and Their Roles in Tumor Growth, Vascularity, and Host Immune Suppression

Leukocytic infiltrates, particularly myeloid cells, can stimulate an anti-tumor immune response, but more often they stimulate tumor development, including promoting invasion, tumor growth, angiogenesis, and metastasis. Distinct myeloid phenotypes are being characterized that have been shown to promote tumor growth, angiogenesis, and metastasis. This review provides an overview of myeloid differentiation and spotlights specific pro-tumorogenic myeloid populations and their role in cancer progression. Efforts to characterize these pro-tumorogenic myeloid cell immunophenotypes may lead to novel targets for cancer therapy.