Antibody targeting facilitates effective intratumoral siRNA nanoparticle delivery to HER2-overexpressing cancer cells

// Maria C. Palanca-Wessels 1, 2, * , Garrett C. Booth 1 , Anthony J. Convertine 3 , Brittany B. Lundy 3 , Geoffrey Y. Berguig 3 , Michael F. Press 4 , Patrick S. Stayton 3 , Oliver W. Press 1, 3 1 Clinical Research Division and Center for Intracellular Delivery of Biologics, Fred Hutchinson Cancer Research Center, Seattle, WA, USA 2 Department of Medicine, Hematology Division, University of Washington, Seattle, WA, USA 3 Department of Bioengineering and Center for Intracellular Delivery of Biologics, University of Washington, Seattle, WA, USA 4 Department of Pathology, University of Southern California, Los Angeles, CA, USA * This work was performed in Seattle, WA, USA. M.C.P.W. performed this work while at the Fred Hutchinson Cancer Research Center, but is now employed by Seattle Genetics Correspondence to: Oliver W. Press, e-mail: press@u.washington.edu Keywords: HER2 antibody, siRNA, targeted antibody delivery, ovarian cancer, breast cancer Received: August 28, 2015     Accepted: January 19, 2016     Published: January 30, 2016 ABSTRACT The therapeutic potential of RNA interference (RNAi) has been limited by inefficient delivery of short interfering RNA (siRNA). Tumor-specific recognition can be effectively achieved by antibodies directed against highly expressed cancer cell surface receptors. We investigated the utility of linking an internalizing streptavidin-conjugated HER2 antibody to an endosome-disruptive biotinylated polymeric nanocarrier to improve the functional cytoplasmic delivery of siRNA in breast and ovarian cancer cells in vitro and in an intraperitoneal ovarian cancer xenograft model in vivo , yielding an 80% reduction of target mRNA and protein levels with sustained repression for at least 96 hours. RNAi-mediated site specific cleavage of target mRNA was demonstrated using the 5′ RLM-RACE (RNA ligase mediated-rapid amplification of cDNA ends) assay. Mice bearing intraperitoneal human ovarian tumor xenografts demonstrated increased tumor accumulation of Cy5.5 fluorescently labeled siRNA and 70% target gene suppression after treatment with HER2 antibody-directed siRNA nanocarriers. Detection of the expected mRNA cleavage product by 5′ RLM-RACE assay confirmed that suppression occurs via the expected RNAi pathway. Delivery of siRNA via antibody-directed endosomolytic nanoparticles may be a promising strategy for cancer therapy.