| Multidrug resistance (MDR), defined as the ability of cancer cells to gain resistance to both conventional and novel chemotherapy agents, is an important
barrier in treating malignancies. Initially, it was discovered that cellular pumps
dependent on ATP were the cause of resistance to chemotherapy, and further
studies have found that other mechanisms such as increased metabolism of
drugs, decreased drug entry, and defective apoptotic pathways are involved in
this process. MDR has been the focus of numerous initiatives and countless
studies have been undertaken to better understand MDR and formulate strategies to overcome its effects. The current review highlights various nano-drug
delivery systems including polymeric/solid lipid/mesoporous silica/metal
nanoparticles, dendrimers, liposomes, micelles, and nanostructured lipid carriers to overcome the mechanism of MDR. Nanoparticles are novel gateways
to enhance the therapeutic efficacy of anticancer agents at the target site of
action due to their tumor-targeting abilities, which can limit the unwanted systemic effects of chemotherapy agents and also reduce drug resistance. Additionally, other innovative strategies including RNA interference as a biological
process used to inhibit or silence specific gene expression, natural products as
MDR modulators with little systemic toxic effects, which interfere with the
functions of proteins involved in drug efflux, and physical approaches such as
combination of conventional drug administration with thermal/ultrasound/
photodynamic strategies are also highlighted. |