s Carbon Nanotubes Enhance the Chemotherapy Sensitivity of Tumors with Multidrug Resistance

Background: Chemotherapy is the most important treatment method against cancer, in addition to surgery and radiotherapy. However, Multidrug Resistance (MDR) in cancer always results in the failure of chemotherapy. Effective chemotherapy agents need to be delivered efficiently, distributed mostly in the tumor tissue, and highly internalized by tumor cells to eventually inhibit proliferation or promote death of the tumor cells. A growing number of studies have indicated that any defects that emerge during these steps could contribute to the occurrence of MDR in tumors. Carbon Nanotubes (CNTs) are newly developed biocompatible materials that can be designed to deliver anticancer agents by functionalizing the CNTs with drugs. Enhanced drug delivery efficiency and improved treatment efficacy have been observed through CNT-based drug delivery systems. However, some reports have shown that the simple administration of CNTs can reverse MDR in cancer and enhance chemotherapy efficacy without anticancer agents attached to the surface of the CNTs. Objective: Through an extensive review of previous reports in regard to CNTs and chemotherapy, this paper aims to identify the various mechanisms of CNTs that inhibit MDR in cancer and enhance chemotherapy sensitivity. Results: CNTs can increase the antitumor effects of chemotherapy agents. CNTs can not only increase drug delivery accuracy and efficiency but also promote drug uptake, decrease drug efflux, improve tumor hypoxia conditions, and induce autophagy and apoptosis in tumor cells, which make the tumor more sensitive to antitumor agents.