TFRC and cancer: A covalent conjugate of artemisinin (flavonoid from Artemisia annua) and transferrin (ART-Tf), an iron transport protein in human, are actively taken up by cancer cells through the transferrin receptor (TfR)-mediated endocytosis pathway, and show significantly higher anti-cancer activity than unconjugated artemisinin (Lai et al. 2005; Nakase et al. 2009).