Tumor microenvironment plays a critical role in tumor initiation and progression. Components in the microenvironment can modulate the growth of tumor cells, their ability to progress and metastasize. A major venue of communication between tumor cells and their microenvironment is through polypeptide growth factors and receptors for these growth factors. This article discusses three major classes of growth-stimulatory polypeptide growth factors and receptors for these growth factors. It also discusses how deregulation of these growth factors or their receptors can drive malignant transformation and progression.