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
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
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.