The functional network of biglycan: A new frontier in tumor progression

Abstract Biglycan is a member of the small leucine‐rich proteoglycan family. Dysregulation of biglycan leads to a broad range of clinical consequences, such as osteoclastogenesis, inflammation, cardiovascular disease, and cancer. Biglycan binding to toll‐like receptor (TLR)−2 or TLR‐4 on immune cells lead to infiltration of immune cells to mediate the inflammatory response. Additionally, the extracellular matrix‐secreted soluble biglycan functions as a danger‐associated molecular pattern molecule involved in the induction of inflammation and cancer. High expression of biglycan is demonstrated in tumor endothelial cells (TECs) of various cancers and correlates with metastatic potential and poor clinical outcomes. This comprehensive review addresses the role of biglycan in both tumor cells and tumor stromal cells, especially TECs, in regulating tumor angiogenesis, tumor growth, metastasis, and chemotherapy resistance.