CSPG4 and cancer: This unique glycosaminoglycan (GAG) chain is covalently attached to multiple proteoglycans such as the cluster of differentiation 44 (CD44), chondroitin sulfate proteoglycan 4 (CSPG4), or Syndecan-1 (SDC1) in various cancer cells or secreted into the microenvironment surrounding the cells and bodily fluids including blood and urine24–27.