A total of 30 specific pathogen-free (SPF) female nude Balb/c mice (6–8 weeks old) were purchased from Shanghai Laboratory Animal Center (Shanghai, China). All rats were housed in a temperature-controlled facility at 23±1°C with a relative humidity of 50±5% and were exposed to a 12-h light/dark cycle. The mammary glands of mice were subcutaneously implanted with βig-h3-overexpressed, si-Rβig-h3-treated or si-Rvector-transfected MCF-7 cells (1×107) and were subsequently divided into three groups (n=10 in each group). Mice were observed for 40 days following tumor inoculation. Tumor diameters were recorded every 2 days and tumor volume was calculated using the following formula: 0.52 × smallest diameter2 × largest diameter (17 (link)). Experimental mice were euthanized when the tumor diameter reached 10 mm. The present study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of China (18 (link)). The present study was also approved by the Ethics Committee of Pingdu People's Hospital (Qingdao, China). All surgery was performed following intraperitoneal injection of sodium pentobarbital (40 mg/kg, Sigma-Aldrich; Merck KGaA, Darmstadt, Germany) to induce anesthesia and all efforts were made to minimize suffering.