Fig. 7: β-catenin directly represses ACOX1 transcription and indirectly activates DUSP14 transcription via c-Myc.

a, b Upregulated ACOX1 expression and downregulated DUSP14 and c-Myc expression by β-catenin inhibition in CRC cells, but not in HIEC-6 cells. Indicated cells were treated with iCRT14 (100 μM) for 24 h and analyzed by RT-qPCR (a) and immunoblotting (b). c, d Schematic presentation of TCF/LEFs-binding element on the ACOX1 locus (c) and c-Myc-binding sites on the DUSP14 locus (d). TBE, TCF/LEFs-binding element; RE, c-Myc-responsive element. Consensus sequence mutations are shown as TBE Mut and RE Mut. e Downregulated ACOX1 expression and upregulated DUSP14 expression by β-catenin overexpression. f Upregulated DUSP14 expression by c-Myc overexpression. HIEC-6 cells transfected with Flag-β-catenin (e) or Flag-c-Myc (f) were subjected to western blot analysis. g, h β-catenin occupancy on the ACOX1 promoter (g) and c-Myc occupancy on the DUSP14 promoter (h). HCT15 and RKO cells were analyzed by ChIP assays. i Assessed Luciferase reporter activities in the presence of exogenous β-catenin (left) and c-Myc (right) in HCT15 and RKO cells. j, k Downregulation of ACOX1 and upregulation of DUSP14 in APC^Min/+ intestinal tumors. ACOX1 and DUSP14 expression was analyzed in normal small intestinal tissues and intestinal adenoma samples from APC^Min/+ mouse (21 weeks of age) by RT-qPCR (j) and western blot analysis (k). Data were analyzed using unpaired Student’s t-test (a, i, j). Data are presented as means ± SD; *P < 0.05, **P < 0.01, ***P < 0.001; n, number of mouse samples.