Cancers develop in complex tissue environments, which they depend upon for sustained growth, invasion and metastasis. The tumor microenvironment comprises innate and adaptive immune cells, fibroblasts, extracellular matrix, and blood and lymphatic vascular networks, which collectively have critical modulatory functions in tumor development and metastasis (Figure 1). Our lab is interested in the critical influence that non-cancerous stromal cells can have on tumor progression and response to therapy. We investigate both positive and negative signals provided by the normal tissue stroma to the cancer cells, and how normal cells can be modified by the cancer cells to produce a variety of factors that enhance tumor malignancy. One of the critical regulatory cell types in the microenvironment are tumor-associated macrophages (TAMs), which have a potent ability to promote tumor progression.