PDX mouse models

The PDX studies were carried out by WuXi AppTec (Shanghai, China). HCC-PDX models were originally established from surgically resected tumor tissue that was implanted in 6–8-week-old female BALB/c nude mice [20]. Animal studies were performed according to the guidelines approved by the Institutional Animal Care and Use Committee of Wuxi AppTec, which follow the guidance of the Association for the Assessment and Accreditation of Laboratory Animal Care. Animals were routinely monitored for their health status and their body weights. Treatment was suspended and/or doses reduced at body weight losses >10%. Animals were euthanized when the tumor size exceeded 2000 mm³. Pieces from tumor xenografts (∼30 mm³) from passages 4–8 (ST1) were implanted subcutaneously at the right flank, and tumors were grown to an average size of about 150–200 mm³. Mice were randomized into groups of 10 and treated by oral gavage once daily with: a) regorafenib at 10 mg/kg dissolved in polypropylene glycol, PEG400, Pluronic F68, water (34:34:12:20); b) sorafenib 30 mg/kg dissolved in Cremophor ethanol, water (12.5:12.5:75); or c) with an unspecific control murine IgG1 antibody (1B711) [31] dissolved in saline, which was given intraperitoneally at a dose of 25 mg/kg every other week and served as a control. This control was used because the study reported here was part of a larger investigation, and previous experiments demonstrated that various vehicles had no influence on tumor growth in comparison to non-treatment (Figure ​(Figure1).1). Tumor size was measured twice weekly using caliper measurements. Tumor volume (mm³) was calculated using the formula 0.5 a × b², where a and b are the long and short diameters of the tumor, respectively. TGI was assessed either by calculating the ratio of the mean tumor volumes of treated and control groups or by determination of the RTV, which relates tumor volumes at any given day of treatment to the volume at the first treatment day.