Abstract 471: RNAi target evaluation in clinically relevant murine model of colon cancer metastasis

Abstract

Abstract Significant challenges remain before RNA interference (RNAi) becomes a reality in practice. Identifying the appropriate genes to target and evaluating these agents in clinically relevant animal models of metastatic cancer are critical. Short- and long-term side effects and potential in vivo toxicities of RNAi therapy are largely unknown due to lack of animal models to simultaneously evaluate RNAi effect on both cancer cells, tumor microenvironment and the host organism. The purpose of our present study was to establish a murine model for metastatic colon cancer which will allow us to evaluate the effect of RNAi on tumor metastases as well as potential side effects to the normal host. METHODS. Murine colon cancer cell lines, CT26 and MC26, expressing green fluorescent protein (GFP) were injected intrasplenically into either Balb/C or Swiss-Webster mice at concentrations of 1×106, 2.5×106 and 5×106 in a volume of 100 uL. Tumor growth and metastasis were monitored for 30 days. To demonstrate siRNA delivery into colon cancer metastasis to the liver, Cy3-labeled siRNA was used. siRNA formulated in DOTAP was administered via tail vein, and mice were sacrificed at 1, 4 and 24 h postinjection. Frozen-section fluorescence microscopy was used to evaluate siRNA delivery and distribution in metastatic liver tumors. RESULTS. We observed extensive metastases in Balb/C mice injected intrasplenically with CT26 cells. The optimal concentration for metastasis was 2.5×106 cells. No intrasplenic tumor growth or metastasis was observed in Swiss-Webster mice after intrasplenic CT26 tumor cell injection or in Balb/C and Swiss-Webster mice after MC26 injection. We also demonstrated Cy3-labeled siRNA delivery into metastatic liver tumors as early as 1 h postinjection. CONCLUSIONS. Intrasplenic injection of CT26 cells offers a clinically relevant murine model for metastatic colorectal cancer and will facilitate evaluation of RNAi therapeutic targets against metastatic cancer. This model will also be useful in the assessment of the effects of RNAi on the tumor microenvironment and possible toxicity to normal host cells. Furthermore, this model may predict the clinical course and the ultimate in vivo response to RNAi therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 471.