The role of Netrin-1 and Reelin in the mechanisms of tyrosine kinase inhibitor (TKI) resistance in Renal Cell Carcinoma.

• Applicant: Dr. Sebastian Karl Frees
• Subject Area: Reproductive Medicine, Urology
• Term: from 2013 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 248736438

In Germany, the incidence of renal cell carcinoma (RCC), comprises nearly 3% of all malignant disease (1). Despite a shift towards an early diagnosis of the disease in a curable stage through incidental findings on ultrasound and CT-scans, the RCC still has a poor prognosis. The 5-year survival rate is only about 65% (1). The last decade has seen a significant paradigm shift in the management of advanced RCC - from immunotherapy to novel approaches targeting angiogenesis - that has resulted in an improvement of the median survival of metastatic RCC from 12 months to up to 24-30 months (2). Nevertheless, metastatic renal cell carcinoma remains a serious, mostly deadly disease. These high mortality rates reflect the inherent limitations of the targeted therapy: durable responses are rare and treatment has typically been associated with the development of resistance after short term disease stabilization. Up to 25% of renal tumors do not respond initially to targeted therapy, complete responses are generally anecdotal, and most tumors develop resistance with a median time to disease progression of only 5-11 months. (3-5)Instrumental to enhanced angiogenesis in clear cell renal cell carcinoma is an upregulation of the vascular endothelial growth factor (VEGF). This growth factor stimulates endothelial proliferation, migration, invasion and survival. Since RCC is dependent on VEGF, systemic therapy for RCC has primarily involved targeting the VEGF pathway either through inhibition of VEGF (monoclonal antibody Bevacizumab) or disruption of the VEGF receptor (Sunitinib,Pazopranib, Sorafenib) (6-7).In preliminary investigations at the Vancouver Prostate Centre, two proteins could be identified that seem to play an essential role in the development of a resistance of renal cell carcinoma cells towards targeted therapy: Reelin and Netrin-1. These molecules were identified to be overexpressed in Sunitinib-conditioned (Caki1-SC) but not in parental (Caki1) or hypoxia-conditioned renal cell carcinoma cells (Caki1-HC) (8). Both proteins have a primarily role in neuronal development and chemotaxis (9-10). In addition, both genes are essential in vascular development during embyogenesis (11). Netrin-1 and Reelin have been found to be overexpressed and associated with worse tumor grade and prognosis in many cancers (12-19).The proposed project is designed to investigate and characterize the role of Netrin-1 and Reelin in the mechanisms of tyrosine kinase inhibitor (TKI) resistance in RCC. Therefore in vivo and in vitro investigations, which analyse the consequences of knockdown of Netrin-1 and Reelin for a Sunitinib treatment, will be performed in the conditioned cells. We will also determine the effect of forced overexpression of the proteins in native Caki1-cells. We believe that further pre-clinical study of these proteins is important to establish the adaptive mechanisms of TKI resistance that may later be utilized to develop new therapies for RCC.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. Martin Gleave