A novel cancer targeting approach based on estrone anchored stealth liposome for site-specific breast cancer therapy

We here report the successful utilization of estrogen receptor (ER) for the delivery of anticancer drug doxorubicin (DOX) encapsulated within pegylated liposome for the treatment of breast cancer. Estrone (ES) was anchored as ligand on to stealth liposome (ES-SL-DOX) for targeting to ERs. In vitro cytotoxicity study was conducted on ER positive and negative breast carcinoma cells. The fluorescent microscopy studies were performed with estrone anchored stealth liposome (ES-SL) loaded with 6-carboxyfluorescein (6-CF). Pharmacokinetic, tissue distribution studies and tumor growth inhibition were carried out followed by intravenous (i.v.) administration of liposomal formulations. ES-SL-DOX demonstrated strongest cytotoxicity to the ER positive cell lines as compared to non-targeted formulations i.e. SL-DOX and plain DOX confirming that ES-SL-DOX was effectively taken up by cells expressing ERs. The half-life (t(1/2)) of SL-DOX and ES-SL-DOX was about 9 and 13 fold higher than that of the free DOX, respectively. Accumulation of ES-SL-DOX in the tumor tissue was 24.27 and 6.04 times higher as compared to free DOX and SL-DOX respectively, after 8 h. ES-SL-DOX at a dose of 5 mg DOX/kg resulted in effective retardation of tumor growth. These findings support that estrogen receptor(s) may be utilized as potential target for chemotherapy of cancers and estrone anchored stealth liposomes could be one of the promising solutions for the delivery of anticancer agent to breast tumors with reduced side-effects.