PGP and leukemia: Here, the authors proposed that P-gp functions to protect the nucleus and prevent DNA-drug interactions that might cause damage [64]; similarly, it has been proposed that P-gp could be expressed in the mitochondria of three different doxorubicin-resistant cancer cells lines: K562 (leukemia), PLC/PRF/5 (hepatocellular carcinoma), and MCF7 (breast).