Media type: E-Article Title: Antibody-Mediated Delivery of Anti–KRAS-siRNA In Vivo Overcomes Therapy Resistance in Colon Cancer Contributor: Bäumer, Sebastian; Bäumer, Nicole; Appel, Neele; Terheyden, Lisa; Fremerey, Julia; Schelhaas, Sonja; Wardelmann, Eva; Buchholz, Frank; Berdel, Wolfgang E.; Müller-Tidow, Carsten Published: American Association for Cancer Research (AACR), 2015 Published in: Clinical Cancer Research, 21 (2015) 6, Seite 1383-1394 Language: English DOI: 10.1158/1078-0432.ccr-13-2017 ISSN: 1557-3265; 1078-0432 Origination: Footnote: Description: Abstract Purpose: KRAS mutations are frequent driver mutations in multiple cancers. KRAS mutations also induce anti-EGFR antibody resistance in adenocarcinoma such as colon cancer. The aim of this study was to overcome anti-EGFR antibody resistance by coupling the antibody to KRAS-specific siRNA. Experimental Design: The anti-EGFR antibody was chemically coupled to siRNA. The resulting complex was tested for antibody binding efficiency, serum stability and ability to deliver siRNA to EGFR-expressing cells. Western blotting, viability, apoptosis, and colony formation assays were performed for efficacy evaluation in vitro. Furthermore, therapeutic activity of the antibody–KRAS-siRNA complexes was examined in in vivo xenograft mouse tumor models. Results: Antibody–siRNA complexes were targeted and internalized via the EGFR receptor. Upon internalization, target gene expression was strongly and specifically repressed, followed by a reduced proliferation and viability, and induced apoptosis of the cells in vitro. Clonogenic growth of mutant KRAS-bearing cells was suppressed by KRAS-siRNA–anti-EGFR antibody complexes. In xenograft mouse models, anti-EGFR antibody–KRAS-siRNA complexes significantly slowed tumor growth in anti-EGFR–resistant cells. Conclusions: The coupling of siRNA against KRAS to anti-EGFR antibodies provides a novel therapy approach for KRAS-mutated EGFR-positive cancer cells in vitro and in vivo. These findings provide an innovative approach for cancer-specific siRNA application and for enhanced therapeutic potential of monoclonal antibody therapy and personalized treatment of cancer entities. Clin Cancer Res; 21(6); 1383–94. ©2015 AACR. Access State: Open Access