ABSTRACT
The development of tumor multidrug resistance (MDR) is a signifi cant clinical obstacle that often results in non-responsive, recurrent disease and eventual metastasis (Dong and Mumper 2010; Yusuf et al. 2003). MDR refers to a state of resilience against structurally and/or functionally unrelated drugs, and can be intrinsic or acquired due to initial exposure to chemotherapeutic agents. Intrinsic MDR may be genetically inherent or may develop as a response to selection pressures within the tumor microenvironment; a tumor cell confronted with survival challenges may undergo transformations resulting in MDR cells. Regardless of the mechanism of MDR, the clinical manifestation occurs due to inability of standard chemotherapeutic regimens to treat the disease effectively. Approaches that increase the dosage or combination of multiple agents in different therapeutic regimens generally do not lead to better clinical outcomes.
