Abstract B50: A patient-derived renal cell carcinoma model as a platform for the identification of novel diagnostic markers and therapeutic targets
Authors: Rigo-Watermeier Teresa , Klein Corinna , Vogel Vanessa , Eisen Christian , Hoefner Thomas , Weichert Wilko , Pahernik Sascha , Hohenfellner Markus , Sprick Martin R. , Trumpp Andreas 
Published: August 2014

Abstract
Clear-cell renal cell carcinoma (ccRCC) is highly resistant to conventional therapies and to date effective treatment is restricted to surgical resection. Pre-clinical in vitro and in vivo models, which accurately mimic this disease, are critical for the development of novel effective therapies. Previous attempts to culture ccRCC cells have been proven difficult and thus, only few ccRCC cell lines are currently available. In addition long-term culturing often causes loss of primary tumor characteristics including tumor heterogeneity. This might explain why in contrast to other tumor entities, tumor-initiating cell (TIC) subpopulations have so far not been reported for ccRCC. TICs have been associated with tumor progression, metastasis and drug-resistance. Consequently these cells have also been named cancer stem cells (CSCs). Furthermore, distinct combinations of genetic and epigenetic alterations result in profound inter-patient heterogeneity and can in part promote TIC activity. Therefore, the development and characterization of clinically relevant patient derived ccRCC-models would provide an experimental basis to study the complex mechanisms leading to and maintaining ccRCCs.
Hence, we established a patient-derived serum-free spheroid culture system that can be used to propagate primary ccRCC cells. These ccRCC cells retain their tumor-initiating potential and mimic the human malignancy upon orthotopic injection into immunodeficient mice. They not only mirror the histological properties but also the molecular features of the parental tumor. Moreover, these cells show the capacity to form de novo metastasis in lungs, which is the most common metastatic site for ccRCC in patients. The established ccRCC cultures were then used as a screening platform for the identification of surface proteins, which are heterogeneously expressed among tumor cells. Functional in vitro and in vivo assays showed that subpopulations defined by expression of these markers also displayed distinct functional characteristics including TIC activity. Gene Set Enrichment Analysis (GSEA) revealed differences in the signaling networks active in these sub-populations. In addition, molecular and cellular assays addressed the significance of these pathways for the maintenance of ccRCC malignancy. Currently the identified surface markers and underlying pathways are validated as potential novel diagnostic and therapeutic targets.
Therefore, our novel patient-derived serum-free spheroid culture system serves as a platform to expand patient derived ccRCCs. It further allows the analysis and characterization of different subpopulations, which may ultimately contribute to the understanding of the molecular basis underlying progression, therapy-resistance and metastasis of this disease.
Citation Format: Teresa Rigo-Watermeier, Corinna Klein, Vanessa Vogel, Christian Eisen, Thomas Hoefner, Wilko Weichert, Sascha Pahernik, Markus Hohenfellner, Martin R. Sprick, Andreas Trumpp. A patient-derived renal cell carcinoma model as a platform for the identification of novel diagnostic markers and therapeutic targets. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B50.