PGP and cancer: These compounds have contributed to cancer treatment for a long time; however, drug resistance occurs through the anti-apoptotic functions of heat shock proteins (HSPs) overexpressed in several cancer cells [1], the occurrence of cancer stem cells (CSCs) resistant to current anti-cancer drugs [2, 3], activation of DNA repair pathways [4], mutation of treatment targets [5], activation of detoxifying enzymes [6], and expression of the drug efflux transporter P-glycoprotein (P-gp) [7].