Multidrug resistance in gastric cancer: recent research advances and ongoing therapeutic challenges.

Gastric cancer is the second leading cause of cancer mortality worldwide. The major cause of treatment failure for gastric cancer is the development of multidrug resistance (MDR) to chemotherapy, which is currently one of the primary treatment options. Recently, research into the MDR of gastric cancer has revealed that, in addition to the classical ATP-binding cassette transporters, such as P-glycoprotein (P-gp) and MDR-associated protein (MRP)1, a number of other molecules might mediate the drug resistance of human gastric cancer. The absence of P-gp and MRP1 expression in some gastric cancer cases also indicates that there might be other mechanisms responsible for human gastric cancer MDR. These molecules belong to different functional families and might work together to confer MDR phenotypes. The new findings may provide new clues to the mechanisms of MDR and enable the selection of new candidates for targeting MDR in human gastric cancer.