PGP and melanoma: In Adriamycin-selected and P-gp positive multidrug-resistant human leukemia cell K562/ADM and its parental K562 cells (Wang et al., 2018), human melanoma celllines (BOWES and A375) (Pastorek et al., 2014) and human osteosarcoma cell lines (143B, MG-63, HOS and U2OS) (Wang et al., 2017), realgar induced cell cycle arrest or induced cell autophagy and apoptosis.