Investigation of antineoplastic effects of new proteasome inhibitor MLN9708 in leukemia and colon cancer cells

Inhibition of the proteasome has emerged as a clinically effective anti-cancer therapeutic approach in recent years. Bortezomib showed extremely high potency against a wide range of cancer cell lines. Bortezomib specifically shows a high efficiency in multiple myeloma, non-small lung cancer, mantle cell lymphomas, and pancreatic cancer. MLN9708, selectivity and potency were similar to that of bortezomib, is currently being investigated in phase I studies. It has an improved second generation new proteasome inhibitor and shows superior antitumor activity in both solid tumor and hematologic malignancy. Preclinical studies show that MLN9708 immediately hydrolyzed to MLN2238, the biologically active form, when it is exposed to aqueous solutions or plasma. In this study, we investigated antineoplastic effects of MLN2238 and Bortezomib on K562 human myelogenous leukemia cells and Caco2 human colon cancer cells. Antiproliferative effects of MLN2238 and Bortezomib were determined by the 4-[3-(4-Iodo-phenyl)-2-(4-nitrophenyl)-2H-5tetrazolio]-1,3-benzene disulphonate (WST-1) assay. Apoptosis was determined by increased Annexin V-PI binding capacity and mitochondrial membrane potential (JC-1) and caspase-3 activity were analyzed using flow cytometry. NF-kB and c-myc get involved in the impact pathway of proteosome inhibition and play an important role in cell inhibition and apoptosis. NF-kB and c-myc mRNA expression levels were determined by Real Time-PCR method. We found that MLN2238 and Bortezomib had significant time- and concentration-dependent antiproliferative effects on K562 and Caco2 cells. It was determined that MLN2238 and Bortezomib induced apoptosis at 24 hours. Also they evaluated apoptosis for increase mitochondria depolarization and caspase-3 activation in both cell lines. MLN2238 and Bortezomib downregulated NF-?B mRNA expression at 24 hours both in K562 and Caco2 cell lines. Concentrations of MLN2238 and Bortezomib decreased mRNA expression of c-myc on K562 cell line at both 24 and 48 incubation time, but they downregulated c-myc mRNA expression on Caco2 cells only at 24 hour. As a result of our study, MLN2238 has important antiproliferative and apoptotic effects on K562 and Caco2 cells. It shows that MLN2238 might be potential agent for leukemia and colon cancer chemotherapy.