Abstract

Despite the continuously growing repertoire of new and improved anti-cancer therapies, triple-negative breast cancer (TNBC) remains a clinical challenge to treat. In this sense, targeting signaling pathways such as Notch and Wnt/β-catenin have attracted growing attention. This work aimed at investigating the possible antitumor effects of IMR-1 as a Notch inhibitor, PRI-724 as a Wnt/β-catenin inhibitor, as well as their combination and to explore the possible crosstalk between Notch and Wnt/β-catenin signaling pathways in MDA-MB-231 TNBC cell line. Microculture tetrazolium test (MTT) was used to determine the drug growth inhibition (GI50), and the results were analyzed using CompuSyn 3.0.1 software. MDA-MB-231 cells were divided into four treatment groups including positive control, IMR-1-treated, PRI-724-treated, and combination-treated groups. Sandwich enzyme-linked immunosorbent assay (ELISA) was used for the determination of the protein levels of hairy and enhancer of split-1 (HES-1), Notch-1, β-catenin, cyclin-D1, and vascular endothelial growth factor (VEGF1). HES-1 gene expression was assessed by quantitative real-time polymerase chain reaction. Statistical analyses were performed using GraphPad Prism Software. The GI50 for IMR-1 and PRI-724 were 15.3 μM and 0.69 μM, respectively. Upon treatment of MDA-MB-231 cells with these drugs, HES-1 gene expression was up-regulated due to single and combined treatments. Moreover, the protein levels of cyclin-D1, VEGF1, HES-1, and Notch-1 were reduced, while those of active β-catenin and active caspase-3 were elevated. IMR-1/PRI-724 combination augmented IMR-1- and PRI-724-mediated effects on MDA-MB-231 cells by initiating apoptotic cell death. Further in vitro and in vivo studies are warranted to support our findings.