CONTEXTMutations of the beta-catenin (CTNNB1) gene are frequently found in adrenocortical tumors. This has important consequences to deregulate the expression of transcriptional targets of the Wnt pathway, which may contribute to tumorigenesis.OBJECTIVEThe objective of the study was to investigate the effect of the small-molecule inhibitor of the T cell factor (Tcf)/beta-catenin complex PKF115-584 on beta-catenin-dependent transcription and proliferation of H295R adrenocortical tumor cells, which harbor mutations in CTNNB1 as well as the TP53 tumor suppressor gene.MAIN OUTCOME MEASURESImmunofluorescence, transient transfection, proliferation assays, and flow cytometric analyses were used.RESULTSNuclear localization of beta-catenin and constitutive activation of beta-catenin-dependent transcription was observed in H295R cells. PKF115-584 dose-dependently inhibited beta-catenin-dependent transcription and H295R proliferation, even in the presence of increased steroidogenic factor-1 levels, which augment proliferation in this cell line. The drug had no effect on HeLa cells, a cell line in which the beta-catenin pathway is not activated. PKF115-584 decreased the percentage of H295R cells in S-phase and increased the percentage of apoptotic cells.CONCLUSIONSInhibitors of the Tcf/beta-catenin complex may prove useful in the treatment of adrenocortical tumors in which multiple genetic alterations have accumulated.