Abstract 3138: Development of a tetracycline-inducible lentiviral system for RNAi screen in PDX tumors.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Patient-derived xenograft (PDX) tumors are believed to be more clinically relevant pre-clinical models for cancer target identification and validation. We used a tetracycline-inducible lentiviral vector that delivers shRNA expression which is tightly linked to a GFP reporter in PDX cells. Using shRNAs against PLK1 (polo-like kinase 1) as positive controls, we demonstrated that three of the four PLK1 hairpins resulted in growth inhibition of HT29 and A549 cells upon dox induction. Correspondingly, these 3 hairpins showed significant knockdown of PLK1 mRNA. To facilitate RNAi in PDX tumors, we have established an in vitro system to culture PDX tumor cells. Gene expression and IHC study demonstrated that tumors regenerated from colon PDX cells grown in vitro retained features of their parental tumors. PDX cells cultured in vitro also remained tumorigenic. When GFP/shRNA-transduced colon PDX cells were re-implanted in mice to form tumors, approximately 30% of the new tumor cells was GFP-positive, enabling us to capture shRNA-expressing cells by flow cytometry. Initial shRNA drop-out screens were carried out in HT29 and colon PDX cells transduced with a pool of ∼600 shRNAs targeting a set of potential cancer associated genes. Included amongst the hairpins demonstrating statistically significant depletion in HT29 were the exact same three PLK1 shRNAs previously functionally validated. These results demonstrated that we have established a robust in vivo shRNA drop-out screening platform in PDX tumors for identification of novel cancer drug targets. Citation Format: Lei Chen, Yi Geng, Dave Fruhling, Wenyan Zhong, Veronica Diesl, Jing Pan, Christine Loreth, Elizabeth Wang, Yaroslava Bulynko, Kim Arndt, Maximillian Follettie. Development of a tetracycline-inducible lentiviral system for RNAi screen in PDX tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3138. doi:10.1158/1538-7445.AM2013-3138