Abstract 5191: An orthotopic xenograft renal cell carcinoma Sunitinib resistant murine model
Authors: Frees Sebastian K. , Moskalev Igor , Zhou Betty , Raven Peter , Chavez-Munoz Claudia , Black Peter , So Alan I. 
Published: July 2016

Abstract
Purpose of study
To develop a reproducible and reliable orthopic xenograft mouse model for Sunitinib resistant renal cell carcinoma (RCC).
Introduction
Clear-cell renal cell carcinoma (ccRCC) is the most common malignancy of the kidneys and has been steadily increasing at a rate of 3% yearly over the last decade. Furthermore, 30% of patients with ccRCC have de novo metastatic disease. Until the last decade, immunotherapy was the only option for metastatic ccRCC treatment. Current first-line systemic therapies for metastatic ccRCC all primarily target the angiogenesis pathway via tyrosine kinase inhibition (TKI) and have increased progression free survival dramatically. However, durable responses are rare, drug resistance invariably arises after short-term disease stabilization and metastatic ccRCC remains almost uniformly lethal. There is currently no animal model for TKI resistance in RCC. We developed a reliable and reproducible orthotopic xenograft mouse model of Suntinib resistance in RCC.
Methods
Luciferin expressing-CAKI-1 human renal cancer cells were injected under the renal capsule of athymic nude mice using ultrasound guidance. After initial tumor growth mice were treated with Sunitinib malate at an initial dose of 40mg/kg which was increased sequentially (60 and 80 mg/kg) at each tumor passage (Fig.1). Tumors were monitored twice weekly by ultrasound and bioluminescence (IVIS system). Tumors exceeding 200mm3 by ultrasound or 10⁁10 photons/sec by IVIS were considered end points. Before passaging, tumors were harvested and immediately dissociated with a Dispase/Collagenase mix. 5×105 cells were injected into the following batch of mice, considering all these steps as one cycle or passage. Tumors were passaged with increasing doses of Sunitinib 5 times.
Results
Tumor take rates were above 95% in each cycle. Initial treatment of Sunitinib at 40mg/kg resulted in a decrease in tumor size via ultrasound and IVIS of about 30%. At around 14 days of treatment tumors started to regrow despite further treatment. In the second cycle tumors did not show a response to a subsequent treatment of 40mg/kg, proving resistance. Even after increasing the dose of Suntinib in the following cycles to 60 and 80 mg/kg respectively, there was no response observed. The fifth cycle (100mg/kg) had to be terminated due to severe side effects in the animals (skin coloring, weight loss), however no decrease in tumor size was observed. We therefore created a Sunitinib resistance model in the range of the maximal tolerated long-term dose in vivo.
Conclusions
This study describes the first orthotopic xenograft renal cell carcinoma Sunitinib resistant mouse model created in situ. The development of Sunitinib resistance in an angiogenic environment establishes a more realistic and translational model, which opens the possibility to study not only the mechanism of Sunitinib resistance but also to find alternative therapies to overcome Sunitinib resistance.
Citation Format: Sebastian K. Frees, Igor Moskalev, Betty Zhou, Peter Raven, Claudia Chavez-Munoz, Peter Black, Alan I. So. An orthotopic xenograft renal cell carcinoma Sunitinib resistant murine model. [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 5191.