Lumican, a Small Leucine-Rich Proteoglycan, and Its Biological Function in Tumor Progression

Lumican is a member of the small leucine-rich proteoglycan (SLRP) family that was originally discovered in the chick cornea and is found in many other tissues throughout the human body. The SLRP family includes decorin, lumican, biglycan, and fibromodulin and constitutes an abundant component of the extracellular matrix (ECM). Lumican plays a significant role in the ECM as an organizer of collagen, although recent studies demonstrate that lumican also modulates numerous cellular functions including proliferation, migration, and differentiation. The contribution of lumican to cancer progression has been noted in several cancers including breast, colorectal, and pancreatic; however, its precise biologic function is still being uncovered. In cancer, lumican appears to play a context-specific role, where high levels of lumican are associated with a poor prognosis in some cancers and a better prognosis in others. This chapter focuses on the function of lumican in cell biology and the ECM of solid tumors and is aimed at providing insights into molecular mechanisms surrounding lumican and tumor biology.