Drug delivery nanoparticles in treating chemoresistant tumor cells

Intrinsic or acquired chemoresistance represents the main obstacle to the successful treatment of cancer patients. Several mechanisms are involved in multidrug resistance: decreased uptake of hydrophilic drugs, increase of energy dependent efflux, alteration of the redox state, alteration of apoptotic pathways, and modification of the tumor microenvironment. In recent years, several types of nanoparticles have been developed to overcome these obstacles and improve the accumulation and release of drugs at the pathological site. In this review we describe the main mechanisms involved in multidrug resistance and the nanovehicles which have been proposed to target specific aspects of this phenomenon.