Histology

Assessment of tumor burden in the kidneys of mice was performed as described previously [14]. Mouse kidneys were fixed in 10% buffered formalin saline (Thermo Scientific, Runcorn, UK) for 24 hours. Fixed kidneys were processed and paraffin embedded according to standard procedures. A series of 5-μm coronal kidney sections was prepared at 200-μm intervals from each kidney. Kidney sections were hematoxylin and eosin (HE)–stained and scanned to create virtual HE slides using an Aperio system (http://www.aperio.com/?gclid = CNXN-8by4a UCFcINfAods3eg1w). Virtual slides were used for lesion quantification. Maximum cross-sectional whole area and cellular area of each renal lesion were measured, respectively, using ImageJ (http://rsbweb.nih.gov/ij). Cellular areas of renal lesions were obtained from parenchyma and stroma. To estimate average size of tumor cells, cysts and papillary and solid tumors on HE-stained kidney sections were randomly chosen using ImageJ. Average size of tumor cells was determined from parenchyma (not stroma) through total area of all tumor cells divided by the number of tumor cells examined. Analysis was conducted blindly with respect to treatment status.