Scutellaria barbata D. Don inhibits colorectal cancer growth via suppression of Wnt/β-catenin signaling pathway

To investigate the effect of the ethanol extract of Scutellaria barbata D. Don (EESB) on colorectal cancer (CRC) growth and Wnt/beta-catenin signaling pathway in vivo and in vitro. In vivo experiment, CRC xenograft mouse model was constructed with injection of HT-29 cells. Following xenograft implantation, twenty mice were randomly divided into EESB-treated group (n=10) and control group (n=10) by a random number table, and were given with intra-gastric administration of 2 g/kg EESB or saline, 5 days a week for 16 days, respectively. At the end of experiment, tumors were removed and weighed by electronic scales. The proliferation biomarker Ki-67 of tumor was evaluated by immunohistochemistry (IHC) assay. In vitro study, HT-29 cells were treated with 0, 0.5, 1.5, 2.5 mg/mL EESB for 24 h. At the end of the treatment, the viability and survival of HT-29 cells were determined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay and colony formation assay, respectively. The mRNA expression of c-Myc, Survivin and adenomatous polyposis coli (APC) was examined by reverse transcription-polymerase chain reaction (RT-PCR) both in tumor tissues of CRC xenograft mice and HT-29 cells. Protein expression of c-Myc, Survivin, APC, and beta-catenin as well as beta-catenin phosphorylation level were evaluated by IHC assay or Western blotting. EESB significantly reduced tumor weight in CRC xenografts mice, compared with the control group (P < 0.05). IHC assay showed that EESB significantly inhibited protein expression of Ki-67 in tumor tissues (P < 0.05). MTT assay showed that EESB significantly reduced HT-29 cell viability in a dose-dependent manner (P < 0.05). Colony formation assay showed that EESB dose-dependently decreased the survival of HT-29 cells (P < 0.05). In addition, RT-PCR assay showed that EESB decreased the mRNA expression of c-Myc and Survivin and increased APC expression, both in tumor tissues of CRC xenograft mice and HT-29 cells (P < 0.05). IHC assay or Western blotting showed that EESB decreased protein expression of beta-catenin, c-Myc and Survivin, as well as increased APC expression and beta-catenin phosphorylation in tumor tissues or HT-29 cells (P < 0.05). EESB significantly reduced tumor growth in CRC xenografts mice, and inhibited the viability and survival of HT-29 cells. EESB could suppress the activation of the Wnt/beta-catenin pathway, which might be one of the mechanisms whereby Scutellaria barbata D. Don exerts its anticancer activity.