287 Background: Greater than 95% of pancreatic adenocarcinomas (PDACs) are driven by KRAS activation; yet, despite decades of work, no RAS inhibitors have reached the clinic. Furthermore, the delivery of therapeutic agents of any kind to PDAC has been hindered by the extensive desmoplasia that accompanies these tumors. Herein, we show that serum-stable and pH-sensing nanoparticles (NPs) are taken up by PDAC cells, can deliver KRAS-specific siRNA into the cytoplasm and inhibit KRAS expression, thereby causing cell death. We go on to use a spontaneous model of pancreas cancer to show that this system can effectively deliver siRNA to stroma-rich tumors. Methods: The murine PDAC cell line KP1 was tested for NP uptake in vitro utilizing fluorescent siRNA NPs (fNPs) in combination with confocal microscopy and flow cytometry. KP1 cells were treated with KRAS-siRNA NP, and KRAS expression and cell viability were assessed with RT-PCR and CellTiter-Glo, respectively. Mice bearing subcutaneous KP1 tumors and KPPC mice with spontaneous PDAC were injected with fNP, and tumor fluorescence was assessed using an in vivo imaging system and fluorescence microscopy. Results: KP1 cells take up fNP in vitro, with > 99% of cells positive for fluorescent signal at 24 hours. Treatment with KRAS-siRNA NP of KP1 cells reduced KRAS expression by 69% (see Figure) and reduced cell viability by 45% compared to untreated and scramble-siRNA treated controls. Gemcitabine demonstrated an additive effect with anti-KRAS therapy. Tumors from KP1 cells grown in mice, and tumors from KPPC mice, were strongly fluorescent 24 hours after IV injection of fNP. Fluorescence microscopy showed successful delivery of fNP to tumors. Conclusions: Our NP system can precisely deliver siRNA to KP1 cells and spontaneous PDAC, overcoming the predominant stromal component in these tumors. KRAS-siRNA delivery downregulates KRAS expression, leading to cell death. This represents a novel treatment for PDAC. Furthermore, with its ability to deliver siRNA into the tumor microenvironment and suppress a known oncogene, this platform could be used to target other putative drivers of tumor progression across various cancer types.
Retraction: A highly antibacterial polymeric hybrid micelle with efficiently targeted anticancer siRNA delivery and anti-infection in vitro/in vivo
