Sporamin suppresses growth of xenografted colorectal carcinoma in athymic BALB/c mice by inhibiting liver β-catenin and vascular endothelial growth factor expression

BACKGROUND Colorectal cancer (CRC) is the third most common malignancy of the digestive tract and the fifth leading cause of cancer-related mortality in China. Sporamin, a Kunitz-type trypsin inhibitor isolated from sweet potato, is a potential anti-cancer agent with activities against a number of malignant tumor cells in vitro. The liver secretes a myriad of endocrine factors that may facilitate the growth and transformation of tumors in the development of CRC. AIM To investigate the effects of sporamin on liver morphology and biomarkers of xenografted CRC in the liver of athymic BALB/c mice. METHODS Twenty-seven male BALB/c nude mice were randomly divided into control, vehide, and sporamin groups. Mice in the latter two groups were intraperitoneally xenografted w ith LoVo colorectal carcinoma cells and intragastrically infused with saline or sporamin (0.5 g/kg body weight/d), respectively, for 3 wk. Hematoxylin and eosin (HE) staining of the sections was performed to observe morphological changes in hepatic tissue and real-time fluorescent quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to measure the expression of beta-catenin and vascular endothelial growth factor (VEGF) in the liver. RESULTS Sporamin significantly reduced the number and weight of tumor nodules formed in the abdominal cavity. Compared with the vehicle group, the mean tumor weight (+/- SD) in the sporamin group was significantly reduced (0.44 +/- 0.10 g vs 0.26 +/- 0.15 g) and the total number of tumors decreased from 93 to 55. HE staining showed that enlargement of the nudeus and synthesis of proteins within hepatocytes, as well as infiltration of inflammatory cells into the liver, were attenuated by sporamin. Immunoliistochemical staining and ELISA showed that the concentrations of beta-catenin and VEGF in the liver were significantly reduced by sporamin. Compared with the vehide group, the expression of beta-catenin measured in integrated optical density units per area was reduced in the sporamin group (47.29 +/- 9.10 vs 26.14 +/- 1.72; P = 0.003). Expression of VEGF was also reduced after sporamin intervention from 20.78 +/- 2.06 in the vehide group to 15.80 +/- 1.09 in the sporamin group (P = 0.021). Compared with the vehide group, the concentration of beta-catenin decreased from 134.42 +/- 22.04 pg/mL to 109.07 +/- 9.65 pg/mL after sporamin intervention (P = 0.00002). qPCR indicated that compared to the vehicle group, relative mRNA expression of beta-catenin and VEGF in the liver of mice in the sporamin-treated group was significantly reduced to 71% +/- 1% (P = 0.000001) and 23% +/- 7% (P = 0.00002), respectively, of the vehide group levels. CONCLUSION Sporamin down-regulates the expression and secretion of beta-catenin and VEGF in the liver, which subsequently inhibits the transcription of downstream genes involved in cancer progression and angiogenesis.