Development and Investigation of a Dihydroartemisinin-Resistant Human Leukemia Cell Line

Abstract

Artemisinin generates cytotoxic free radicals when it reacts with ferrous iron, and induces molecular damages and apoptosis in cells. Its toxicity is more selective toward cancer cells because cancer cells contain a higher level of intracellular free iron. Dihydroartemisinin (DHA), an active metabolite of artemisinin, has selective cytotoxicity toward Molt-4 human lymphoblastoid cells and could be a potent cancer chemotherapeutic compound. A major concern is whether cancer cells could develop resistance to DHA after repeated administrations, thus limiting its therapeutic efficacy. In the present study, a DHA-resistant Molt-4 cell line (RTN) was developed by exposing Molt-4 cells to gradually increasing concentrations of DHA in vitro. The half maximal inhibitory concentration (IC50) of DHA for RTN cells was significantly higher than that of Molt-4 cells. However, RTN cells did not exhibit any significant cross resistance to artemisinin-tagged holotransferrin (ART-TF), a synthetic artemisinin compound. In addition, DNA damage induced by DHA and ART-TF in both Molt-4 and RTN cells was investigated using the Comet assay. RTN cells exhibited a significantly lower level of basal and X-ray induced DNA damage compared to Molt-4 cells. Both DHA and ART-TF induced DNA damage in normal Molt-4 cells, whereas DNA damage was induced in RTN cells by ART-TF, and not DHA. This research shows that ART-TF is a potent anticancer agent against DHA- resistant RTN cells and could be used as a replacement when resistance to DHA is developed.