Cancer Progression Related with Tumor-associated Macrophages

Tumor-associated macrophages are one of the main populations of inflammatory cells in cancers that favor tumor cell growth and survival. Tumor-derived factors such as VEGF-A and CSF-1 recruit the macrophages in tumor micro environment and alter their phenotype in M1 to M2 or tumor-associated macrophages by secretion of several cytokines including IL-4, IL-13 and VEGF-A. In return tumor-associated macrophages released growth factors and cytokine that helps in cancer cell proliferation and metastasis. Tumor-associated macrophage secreted cytokines promotes the angiogenesis and lymphangiogenesis that assist tumor cell to metastasize in distant organs. Importantly, tumor-associated macrophages promote an immunosuppressive environment with the help of other immune cells in the tumor-bearing host that helps tumor to grow unchecked and unchallenged. In addition, tumor-associated macrophages induce resistance against cancer therapy and boost tumor regrowth after therapy. In this review, we discuss the role of tumor-associated macrophages in the pathobiology of cancer. Understanding of the crucial role of tumor-associated macrophages in cancer progression may help to assess potential therapeutic strategies.