Cancer associated fibroblasts, also known as activated fibroblasts, are the most abundant cell type present in the tumor stroma. Under normal conditions, fibroblasts secrete factors to maintain tissue homeostasis. However, in the tumor microenvironment, fibroblasts undergo changes that stimulate tumor growth and invasion. They secrete growth factors, cytokines and enzymes that promote cancer cell proliferation, survival, angiogenesis, metastasis and remodeling of extracellular matrix. Fibroblasts also suppress anti-tumor immune responses by secreting immune modulatory factors. Targeting these activated fibroblasts is emerging as a promising therapeutic strategy to impair tumor promoting microenvironment.

Immune cells such as macrophages, neutrophils, mast cells, dendritic cells and lymphocytes infiltrate solid tumors and modulate cancer progression. Tumor Microenvironment is associated macrophages release factors that enhance tumor cell survival, growth, angiogenesis and metastasis. Chronic inflammation mediated by immune cells within tumors also contributes to genetic instability in cancer cells, driving further progression. While T cells are the most abundant immune cell type, tumors evade immune detection by inducing an immunosuppressive state dominated by regulatory T cells and myeloid derived suppressor cells within the microenvironment. New immunotherapies aim to reverse this immunosuppression.

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