Lumican is a 40 kD secreted protein which belongs to the small leucine-rich repeat proteoglycans (SLRPs) and the class II subfamily. Human Lumican is synthesized as a 338 amino acid precursor then cut the 18 aa signal sequence. The mature Human Lumican contains 12 leucine-rich repeats (LRRs), 4 potential sites of N-linked glycosylation, and a C- terminal with two conserved cyst-eines. Lumican can be existed in extracellular matrix of human articular cartilage. Lumican participates in the maintenance of tissue homeostasis and regulates cellular functions in vivo, such as cell proliferation, adhesion, migration, and differentiation. The overexpression of lumican has been correlated to colorectal tumor, breast, neuroendocrine, and pancreatic cancers.