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,vehicle,and sporamin groups.Mice in the latter two groups were intraperitoneally xenografted with 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 ofβ-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 nucleus and synthesis of proteins within hepatocytes,as well as infiltration of inflammatory cells into the liver,were attenuated by sporamin.Immunohistochemical staining and ELISA showed that the concentrations ofβ-catenin and VEGF in the liver were significantly reduced by sporamin.Compared with the vehicle group,the expression ofβ-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 vehicle group to 15.80±1.09 in the sporamin group(P=0.021).Compared with the vehicle group,the concentration ofβ-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 ofβ-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 vehicle group levels.CONCLUSION Sporamin down-regulates the expression and secretion ofβ-catenin and VEGF in the liver,which subsequently inhibits the transcription of downstream genes involved in cancer progression and angiogenesis.

Anticancer effects of sweet potato protein on human colorectal cancer cells

AIM: To investigate the effects of proteins purified from sweet potato storage roots on human colorectal cancer cell lines. METHODS: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Hoechst 33258 nuclear staining and Boyden transwell chamber methods were used to determine whether purified sweet potato protein (SPP) from fresh sweet potato roots affected proliferation, migration and invasion, respectively, of human colorectal cancer SW480 cells in vitro . The inhibitory effects of SPP on growth of human colorectal cancer HCT-8 cells intraperitoneally xenografted in nude mice and spontaneous lung metastasis of murine Lewis lung carcinoma 3LL cells subcutaneously transplanted in C57 BL/6 mice were also investigated in vivo . RESULTS: SPP inhibited the proliferation of SW480 cells in a dose-dependent manner, with an IC 50 value of 38.732 μmol/L (r2 = 0.980, P = 0.003) in the MTT assay. Hoechst 33258 nuclear staining further revealed inhibition of cell viability and induction of apoptosis by SPP. The transwell assay disclosed significant reduction in migrated cells/field by 8 μmol/L SPP (8.4 ± 2.6 vs 23.3 ± 5.4, P = 0.031) and invaded cells/field through the ECMatrix by 0.8 μmol/L SPP, compared with the control (25.2 ± 5.2 vs 34.8 ± 6.1, P = 0.038). Both intraperitoneal (ip) and intragastric (ig) administration of SPP led to significant suppression of growth of intraperitoneally inoculated HCT-8 cells in nude mice to 58.0% ± 5.9% (P = 0.037) and 43.5% ± 7.1% (P = 0.004) of the controls, respectively, after 9 d treatment. Bloody ascites additionally disappeared after ip injection of trypsin inhibitor. Notably, ig and ip administration of SPP induced a significant decrease in spontaneous pulmonary metastatic nodule formation in C57 BL/6 mice (21.0 ± 12.3 and 27.3 ± 12.7 nodules/lung vs 42.5 ± 4.5 nodules/lung in controls, respectively, P < 0.05) after 25 d treatment. Moreover, the average weight of primary tumor nodules in the hind leg of mice decreased from 8.2 ± 1.3 g/mice in the control to 6.1 ± 1.4 g/mice in the ip group (P = 0.035). CONCLUSION: SPP exerts significant antiproliferative and antimetastatic effects on human colorectal cancer cell lines, both in vitro and in vivo .