Proteases and their involvement in cancer progression have been well addressed and documented; however, the emerging premise presented within this book is that Heparanase is a master regulator of aggressive cancer phenotypes and crosstalk with the tumor microenvironment. This endoglycosidase contributes to tumor-mediated remodeling of the extracellular matrix and cell surfaces, augmenting the bioavailability of pro-tumorigenic and pro-inflammatory growth factors and cytokines that are bound to Heparan sulfate. Compelling evidence ties Heparanase with all steps of tumor progression including tumor initiation, growth, angiogenesis, metastasis, and chemoresistance, supporting the notion that Heparanase is an important contributor to the poor outcome of cancer patients and a validated target for therapy. Unlike Heparanase, heparanase-2, a close homolog of Heparanase, lacks enzymatic activity, inhibits Heparanase, and regulates selected genes that promote normal differentiation and tumor suppression. Written by internationally recognized leaders in Heparanase biology, this volume presents a comprehensive understanding of Heparanase’s multifaceted activities in cancer, inflammation, diabetes and other diseases, as well as its related clinical applications to scientists, clinicians and advanced students in cell biology, tumor biology and oncology.