Proteoglycans in Prostate Cancer Progression and Therapy Resistance

The extracellular matrix (ECM) is a complex noncellular network of (macro-)molecules that surrounds and supports diverse cells in tissues and organs. In cancer, ECM is a part of the tumor microenvironment (TME) that embeds its cellular components including cancer cells and the neighboring non-cancerous stromal cells such as fibroblasts, endothelial, and immune cells. Given the complexity of players and interactions that the ECM participates in and is exposed to in the TME, it does not come as a surprise that many of the processes that drive cancer progression take part precisely in the ECM compartment of the TME. Along with diverse glycoproteins and collagens, proteoglycans (PGs) are among the main components of the core ECM. PGs are composed of a protein core to which glycosaminoglycan chains are attached. Considering the structural diversity of these molecules and their 'hybrid' nature, it is not surprising that they are involved in a variety of processes that are vital for surrounding cells. Moreover, they are secreted by both cancer and stromal cells, contributing to the complexity of interactions in the TME. In prostate cancer, PGs have been shown to be involved in many steps of its progression; the most prominent examples include the seemingly tumor-promoting roles of versican, perlecan, and biglycan, and the tumor-suppressive roles of decorin and betaglycan. The role of syndecan 1 is a bit more complex; namely, the nature of its role is context dependent. In this narrative review article, the roles of PGs in prostate cancer progression and therapy resistance are discussed in more detail.