Desenvolvimento, caracterização e avaliação da atividade antiproliferativa de paclitaxel e rapamicina em lipossomas alvo-específicos contra células de câncer de mama HER2-positivas

Liposomes are vesicles in which one or more phospholipid bilayers enclose an inner aqueous compartment. Liposomes may be designed as drug delivery systems for either hydrophilic and lipophilic drugs, also, surface modifications can promote active targeting of the drug carrier to the pharmacologic target site. Immunoliposomes are prepared with antibodies on their surface used for active targeting. Overexpression of the human epidermal growth factor receptor 2 (HER2) occurs in 20-35% of breast cancer. Trastuzumab (anti-HER 2) is a humanized monoclonal antibody designed to specifically antagonize HER’s function. Paclitaxel is a potent drug used against solid tumors including ovarian carcinoma and metastatic breast cancer. Rapamycin is a lipophilic macrolide antibiotic developed as an immunosuppressant and was subsequently found to display potent antitumour activity in a variety of solid tumors. In this work, the encapsulation of rapamycin and paclitaxel in liposomes and immunolipossomes was investigated to evaluate the antiproliferative efficiency of these drugs using the monoclonal antibody (trastuzumab) which targets HER2 receptors present in breast cancer cells (SKBR3). Smalls liposomes with mean diameter of about 100 nm were prepared by lipid film hydratation, followed by extrusion. Immunoliposomes were produced by covalently linking thiolated trastuzumab to DSPE-PEG(2000)-maleimide followed by its insertion into pre-formed liposomes. Co-encapsulation of paclitaxel and rapamycin in liposomes and immunoliposomes was successfully obtained. These systems were more cytotoxic to tumor cells than liposomes containing one of the drugs. Approximately 12 anti-HER2 antibody units were covalently coupled to each liposomal surface. Immnuliposomes showed higher citotoxicity in comparison to liposomes without antibody in their surface. The inhibitory concentrations 50% (IC50) of paclitaxel and rapamycin encapsulated in immunolipossomes was, respectively, 71% and 80% lower than non-targeted liposomes after 48 hours of incubation Fluorescence microscopy demonstrated that immunoliposomes (labeled with rhodamine) were able to interact with the surface of SKBR3 cells. The imunoliposomes represent a promising drug delivery system to improve the efficacy of co-encapsulated paclitaxel and rapamycin using the active targeting approach.