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Nanoparticles (NP) as carriers for anti-cancer drugs have shown great promise. Specific targeting of NP to malignant cells, however, remains an unsolved problem. Conjugation of antibodies specific for tumor membrane antigens to NP represents one approach to improve specificity and to increase therapeutic efficacy. In the present study, for the first time a novel membrane heat shock protein (Hsp70)-specific antibody (cmHsp70.1) was coupled to human serum albumin (HSA) NP, loaded with microRNA (miRNA) plasmids to target the inhibitor of apoptosis protein survivin. The physicochemical properties of monodisperse miRNA-loaded NP showed a diameter of 180 nm to 220 nm, a plasmid incorporation of more than 95% and a surface binding capacity of the antibody of 70-80%. Antibody-conjugated NP displayed an increased cellular uptake in U87MG and LN229 glioblastoma cells compared to isotype control antibody, PEG-coupled controls and peripheral blood lymphocytes (PBL). Survivin expression was significantly reduced in cells treated with the Hsp70-miRNA-NP as compared to non-conjugated NP. Hsp70-miRNA-NP enhanced radiation-induced increase in caspase 3/7 activity and decrease in clonogenic cell survival. In summary, cmHsp70.1 miRNA-NP comprise an enhanced tumor cell uptake and increased therapeutic efficacy of radiation therapy in vitro and provide the basis for the development of antibody-based advanced carrier systems for a tumor cell specific targeting., (© 2013.)

One of the main challenges in radiation oncology is to overcome the resistance of cancer cells against treatment by molecular targeted approaches. Among the most promising targets is the inhibitor of apoptosis protein survivin, known to be associated with increased tumour aggressiveness and therapy resistance. The objective of this study was the development of a human serum albumin-based nanoparticulate carrier system for plasmid-mediated RNA interference (miRNA) and the investigation of its in vitro efficacy on survivin knockdown and cellular toxicity in SW480 colorectal cancer cells. The results demonstrate a robust nanoparticulate system of a size around 220 nm with a plasmid incorporation efficacy of about 90%. Moreover, treatment of carcinoma cells with survivin-miRNA nanoparticles resulted in reduction of survivin expression by 50% and increased cytotoxicity if combined with ionising irradiation. These nanoparticles comprise a promising option to enhance the response of carcinoma cells to therapy with ionising irradiation.