Six-week-old female BALB/c nude mice were purchased from Byrness Weil Biotechnology Ltd. (Chengdu, China) and housed in a specific pathogen-free environment with a 12-h light/dark cycle and controlled temperature and humidity, and food and water were provided ad libitum. Three million designated treated PLC5 cells were collected and injected subcutaneously into mice. At least 4 mice were used in each group in each experiment. Once the tumours reached a mean volume of 200 mm³, the mice were treated intraperitoneally with sorafenib every 3 days. The mice were then euthanized at the indicated time after injection. Each tumour was dissected, fixed with 4% formaldehyde, and embedded in paraffin. The tumour growth was monitored weekly by calliper measurements.