The pancreatic and duodenal homeobox factor-1 (Pdx1) is essential for pancreatic development and insulin gene transcription whereas c-Myc has a deleterious effect on islet function. However, the relationship between c-Myc and Pdx1 is poorly concerned. Here we demonstrated that Pdx1 could suppress c-Myc promoter activity, which relied on Tcf binding elements harbored in c-Myc promoter. Furthermore, the transcription activity of -catenin/Tcf was markedly decreased upon Pdx1 expression, but cotransfection of Pdx1 shRNA abrogated this effect. Pdx1 expression did not induce -catenin degradation nor did it alter their subcellular distribution. The mutation analysis showed that the amino acids (1-209) of Pdx1 harboring an inhibitory domain, which might lead to the reduction of -catenin/Tcf/p300 complex levels and attenuate their binding activity with c-Myc promoter sequences. Moreover, Adenovirus-mediated Pdx1 interference caused cell proliferation and cytokine-induced apoptosis via the dysregulation of c-Myc transcription. These results indicated that the Pdx1 functioned as a key regulator for maintenance of cells function, at least in part, through controlling c-Myc expression and the loss of its regulatory function may be an alternative mechanism for -cell neogenesis and apoptosis found in diabetes.