ATP-binding cassette (ABC) transporters in cancer: A review of recent updates.

The ATP-binding cassette (ABC) transporter superfamily is one of the largest membrane protein families existing in wide spectrum of organisms from prokaryotes to human. ABC transporters are also known as efflux pumps because they mediate the cross-membrane transportation of various endo- and xenobiotic molecules energized by ATP hydrolysis. Therefore, ABC transporters have been considered closely to multidrug resistance (MDR) in cancer, where the efflux of structurally distinct chemotherapeutic drugs causes reduced itherapeutic efficacy. Besides, ABC transporters also play other critical biological roles in cancer such as signal transduction. During the past decades, extensive efforts have been made in understanding the structure-function relationship, transportation profile of ABC transporters, as well as the possibility to overcome MDR via targeting these transporters. In this review, we discuss the most recent knowledge regarding ABC transporters and cancer drug resistance in order to provide insights for the development of more effective therapies.

Revisiting the role of nanoparticles as modulators of drug resistance and metabolism in cancer.

INTRODUCTION: Drug resistance is the major obstacle impeding the efficacy of chemotherapeutic agents. Although numerous drug delivery techniques have been developed to combat drug resistance, their limitations of non-specific targeting and inconsistent bioavailability has led to the search of novel delivering strategies, such as nanoparticles. AREAS COVERED: Nanoparticles for anti-cancer drug delivery are microscopic preparations encapsulating a chemotherapeutic and a chemosensitizer into a rationally designed drug delivery vehicle. Nano-strategies directed against multi-drug resistance (MDR) can be categorized into those inhibiting the drug efflux pumps, those effective against the cellular factors of drug resistance, and the combinational based strategies. Here, we review the most recent literature to reposition nanoparticles as chemotherapeutics and inhibitors of MDR. EXPERT OPINION: Novelty in anti-cancer drug delivery has led to the formulation of chemotherapeutics and MDR inhibitors as nano-preparations, which are multi-functional and have better tumor cell-targeting effects. Their characteristics of size and surface attachments make them readily diffusible through the tumor vasculature and increase their retention time as well. With a better understanding of the molecular mechanisms of drug resistance, more potent and multi-targeted nano-preparations can be formulated in the near future.