Several reports have elucidated the mechanisms of DOX resistance in cancer cells such as up-regulation of multidrug resistance protein 1 (also known as P-glycoprotein), high-expression of anti-apoptotic proteins of B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra-large (Bcl-xL), down-regulation or mutation of topoisomerase II, decreased apoptosis caused by p53 mutation and altered proliferation of cancer cells 30-34. The gene discussed is ABCB1; the disease is cancer.