Abstract 609: An established ex vivo 3D culture platform using patient-derived xenograft (PDX) tumors replicate the anti-tumor efficacy observed in vivo
Authors: Xu Xiaoxi , Zhang Wenna , Xie Bingying , Bao Zheng Zheng , Mei Zhu , Wery Jean-Pierre , Ning Jinying 
Published: July 2016

Abstract
Patient-derived xenograft (PDX) models closely mimic the pathological phenotypes of the original tumors, thus they are ideal surrogates for preclinical anticancer drugs efficacy testing. However, there is an increasing demand to rapidly and reliably screen out candidate drugs at earlier stages, and in vivo animal studies usually take months to produce efficacy data. Compared to traditional two-dimensional (2D) culture, three-dimensional (3D) culture systems more closely reflect in vivo responses. Therefore, we developed an ex vivo 3D culture platform using freshly isolated PDX-derived tumor cells, cultured on the natural methylcellulose polymer as an ex vivo drug screening system to meet the need for patient relevant, lower cost and high-throughput methods.
Single-cell suspensions freshly isolated from PDX tumors are seeded in semisolid methylcellulose media and the drug efficacy is quantitatively evaluated by CellTiter-Glo® (CTG) luminescent assay. The main advantage of this method is the possibility of testing cytotoxicity within days (7 days on average), rather than months. Also, the process is carried out in mild condition and the scaffold material is inert to avoid unwanted cellular response. Moreover, cell spheroids can be easily retrieved for further analysis.
Dissociated primary tumor cells derived from either fresh or frozen PDX tumors remain highly viable and form colonies when cultured in 3D. The success rate of generating ex vivo 3D culture from PDX tumors is higher than 90%, and over 60 PDX models were validated from cancer of various origins. We monitored tumor colony formation and generated a fitted drug concentration-response curve with small variations in CTG cell viability assays. Most importantly, the ex vivo 3D drug response profiling correlated well with the response obtained in vivo from PDX models (over 80% in average), for anticancer drugs with a variety of mechanisms of action including kinase inhibitor, antineoplastic agent and antibodies. Compared with a commercialized 3D drug testing plates, similar results were obtained in our system, with the advantage of a significant reduction in the cost. These data suggest that our 3D ex vivo cell culture platform from freshly isolated or frozen PDX-derived cells is a feasible and authentic method for testing drug efficacy in a short time period before transitioning to multiple PDX models.
To sum up, our ex vivo 3D culture platform can save time and reduce costs, and is extremely useful for preclinical evaluation of anticancer drug, filling the gap between cell line-based and tumor bearing mice-based drug studies, allowing low cost, high throughput in vitro drug screening and the clinically relevant in vivo drug efficacy studies.
Citation Format: Xiaoxi Xu, Wenna Zhang, Bingying Xie, Zheng Zheng Bao, Zhu Mei, Jean-Pierre Wery, Jinying Ning. An established ex vivo 3D culture platform using patient-derived xenograft (PDX) tumors replicate the anti-tumor efficacy observed in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 609.