Abstract: The acquisition of multiple drug resistance (MDR) phenotype is associated with the overexpression of multidrug resis -tance-associated genes, such as MDR 1, MRP 1, and BCRP. P- glycoprotein (P- gp), encoded by MDR 1, is one of the most extensively characterized MDR transporters in cancer. P- gp mainly functions as a drug pump that excretes chemotherapeutic drugs from cancer cells. However, P- gp participates in cancer progression- related processes, such as cancer cell proliferation, growth, apoptosis, migra -tion, and invasion. Several functions are independent of drug transporter activities. These data suggest that novel mechanisms are em -ployed by P-gp to promote cancer progression. Thus, novel functions of P-gp should be understood and mechanisms by which P-gp pro motes cancer aggravation should be determined to improve cancer diagnosis and treatment. In this review, recent research progress on novel contributions of P-gp to cancer progression is summarized.