Ursolic acid ameliorates azoxymethane/dextran sulfate sodium-caused colorectal cancer by inhibition of Wnt signaling cascade

OBJECTIVE To investigate the pharmacological effect of ursolic acid(UA)on colitis-associated colorectal cancer(CAC)and its underlying mechanism based on the Wnt signaling pathway.METHODS The CAC model in mice was established by azoxymethane(AOM)combined and dextran sulfate sodium salt(DSS),accompanied by treatment with various dosages of UA and concomitant appraisal of body weight,stool and physical state of the mice.After the sacrifice of the mice,the tumor and length of the colorectum were measured,followed by retrieval of the liver,spleen,thymus and tumor tissue for downstream assays.The levels of inflammatory factors interleukin-6(IL-6),IL^(-1)βand C-reactive protein(CRP)in the tumor and serum were examined by enzyme-linked immunosorbent assay(ELISA).The pathological changes of colorectal tissues were observed by HE staining.The levels in tumors of Wnt/β-catenin signaling pathway-related proteins Wnt4,GSK-3β,β-catenin,TCF4,LEF1,c-Myc,cyclin D1 and apoptosis-related protein Bcl-2 were assayed by immunohistochemistry(IHC).The mRNA expressions of Wnt4,GSK-3β,β-catenin,TCF4,LEF1,c-Myc,cyclin D1,Bcl-2,Bax,caspase-9 and caspase-3 in tumors were detected by real-time quantitative RT-PCR(RT-qPCR).The protein levels of Wnt4,GSK-3β,β-catenin,TCF4,LEF1,c-Myc,cyclin D1,phospho-β-catenin,phospho-GSK-3β,Bcl-2 and Bax in tumors were probed by analyzed by Western blotting(WB).Also,RNA-seq was employed to assess the gut microbiota in the mice.RESULTS UA significantly ameliorated the symptoms of AOM/DSS-induced mouse CAC,evidenced by improved physical state,body weight,survival rate,colorectal length,the mass of liver,thymus,spleen,and decreased CAC load and colorectal mass.UA attenuated the levels of IL-6,IL^(-1)βand CRP in the mouse serum and colorectal tumor in a dose-dependent manner.HE staining showed that UA lessened carcinogenesis in the colorectum,with lower infiltration of lymphocytes,versus the control.IHC indicated that UA mitigated the expression of Wnt4,β-catenin,TCF4,LEF1,c-Myc,cyclin D1,Bcl-2,and promoted the GSK-3βexpression,compared with the control.Furthermore,UA diminished the mRNA expressions of Wnt4,β-catenin,TCF4,LEF1,c-Myc,cyclin D1,Bcl-2,and heightened the mRNA levels of GSK-3β,caspase-3,capase-9 and Bax in CAC.The results of mRNA expressions were verified by WB analysis,which revealed that UA impeded the protein expression of Wnt4,β-catenin,c-Myc,cyclin D1,Bcl-2,TCF4,LEF1,and elevated the protein levels of GSK-3βand Bax,phospho-β-catenin in mouse CAC.In addition,UA substantially ameliorated the gut microbiota to store the metabolic function in the mice with CAC.CONCLUSION Ursolic acid may protect against CAC,potentially by downregulation of Wnt/β-catenin signaling pathway activity and restoration of gut microbiota.