Anti-CD22 antibody targeting of pH-responsive micelles enhances small interfering RNA delivery and gene silencing in lymphoma cells.

The application of small interfering RNA (siRNA) for cancer treatment is a promising strategy currently being explored in early phase clinical trials. However, efficient systemic delivery limits clinical implementation. We developed and tested a novel delivery system comprised of (i) an internalizing streptavidin-conjugated monoclonal antibody (mAb-SA) directed against CD22 and (ii) a biotinylated diblock copolymer containing both a positively charged siRNA condensing block and a pH-responsive block to facilitate endosome release. The modular design of the carrier facilitates the exchange of different targeting moieties and siRNAs to permit its usage in a variety of tumor types. The polymer was synthesized using the reversible addition fragmentation chain transfer (RAFT) technique and formed micelles capable of binding siRNA and mAb-SA. A hemolysis assay confirmed the predicted membrane destabilizing activity of the polymer under acidic conditions typical of the endosomal compartment. Enhanced siRNA uptake was demonstrated in DoHH2 lymphoma and transduced HeLa-R cells expressing CD22 but not in CD22 negative HeLa-R cells. Gene knockdown was significantly improved with CD22-targeted vs. nontargeted polymeric micelles. Treatment of DoHH2 cells with CD22-targeted polymeric micelles containing 15 nmol/l siRNA produced 70% reduction of gene expression. This CD22-targeted polymer carrier may be useful for siRNA delivery to lymphoma cells.