ABSTRACT
Chemotherapy is the most widely used treatment for cancer therapy, but its efficacy is limited by the side effects of non-specificcytotoxic drugs. Ligand-based targeting drug-delivery system is a solution to circumvent this issue. In this study, an ABCG2aptamer–doxorubicin complex was prepared, and its efficacy in targeted drug delivery to mitoxantrone-resistance breast cancer cellline (MCF7/MX) was evaluated. The formation of aptamer–doxorubicin physical complex was analyzed by fluorometric analysis.The cytotoxicities of doxorubicin and aptamer–doxorubicin complex on MCF7 and MCF7/MX cell lines were evaluated by theMTT assay, and IC50 values were obtained. Cellular uptake of aptamer–doxorubicin complex was assessed by flow cytometrycellular uptake assay. Results: Fluorometric analysis of aptamer–doxorubicin showed 1–1.5 molar ratio of the drug to the aptamercould efficiently quench Dox fluorescence. MTTassay results showed that MCF7/MX cells were more resistant to doxorubicin thanMCF7 cells (IC50 : 3.172 ± 0.536 and 1.456 ± 0.154 lM, respectively). Flow cytometry and MTT assay results showed that theaptamer–doxorubicin complex could increase the uptake and cytotoxicity of doxorubicin in MCF7/MX cell line in comparison withfree doxorubicin, while the same treatments had no effect on IC50 of Dox on MCF7 cells. The results proposed that the ABCG2aptamer–drug complex can be effectively used for specific drug delivery to ABCG2-overexpressing cells.
ABSTRACT
Breast cancer resistance protein (BCRP, ABCP or MXR)/ATP-binding cassette subfamily G member 2 (ABCG2) was characterized as a multidrug resistance efflux transporter in 1998. ABCG2 physiologically acts as a part of a selfdefence mechanism for the organism; it enhances eliminating of toxic xenobiotic substances and harmful agents in the intestine, as well as through the blood–brain barrier and placenta. ABCG2 recognizes and transports numerous anticancer drugs including conventional chemotherapeutic and new targeted small therapeutic molecules in clinical usage. Development of ABCG2 inhibitors for clinical usage may allow increased penetration of therapeutic agents into sanctuary sites and increases their intestinal absorption. Here we review the mechanisms that modulate MDR mediated by the ABC transporter ABCG2 in normal and cancer cells by different levels including, epigenetic modifications, transcriptional, post-transcriptional, translation and post-translational regulation. Some clinical applications of ABCG2 inhibitors are also explained.