ABSTRACT
Selective Mcl-1 inhibitors may overcome the drug resistance caused by current anti-apoptotic Bcl-2 protein inhibitors in tumors with Mcl-1 overexpression. Based on previously discovered compounds with a 3-phenylthiophene-2-sulfonamide core moiety, in this work, we have obtained new compounds with improved binding affinity and/or selectivity under the guidance of structure-based design. The most potent compounds achieved sub-micromolar binding affinities to Mcl-1 (Ki â¼ 0.4 µM) and good cytotoxicity (IC50 < 10 µM) on several tumor cells. 15N-heteronuclear single-quantum coherence NMR spectra suggested that these compounds bound to the BH3-binding groove on Mcl-1. Several cellular assays revealed that FWJ-D4 as well as its precursor FWJ-D5 effectively induced caspase-dependent apoptosis, and their target engagement at Mcl-1 was confirmed by co-immunoprecipitation experiments. Treatment with FWJ-D5 at 50 mg/kg every 2 days on an RS4;11 xenograft mouse model for 22 days led to 75% reduction in tumor volume without body weight loss.
Subject(s)
Antineoplastic Agents/pharmacology , Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Apoptosis/drug effects , Cell Line , Cell Proliferation/drug effects , Cell Survival/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Humans , Male , Mice , Mice, Inbred NOD , Mice, SCID , Molecular Structure , Myeloid Cell Leukemia Sequence 1 Protein/metabolism , Neoplasms, Experimental/drug therapy , Neoplasms, Experimental/metabolism , Neoplasms, Experimental/pathology , Structure-Activity RelationshipABSTRACT
Targeting cancer-related Hsp70-Bim protein-protein interactions (PPIs) offers a new strategy for the design of Hsp70 inhibitors. Herein, we discovered a novel Hsp70 inhibitor, S1g-6, based on the established BH3 mimetics. S1g-6 exhibited sub-µM binding affinity toward Hsp70 and selectively disrupted Hsp70-Bim PPI. The target specificity of S1g-6in situ was validated by affinity-based protein profiling, co-immunoprecipitation, and cell-based shRNA assays. S1g-6 specifically antagonized the ATPase activity of Hsp70 upon recruiting Bim and showed selective apoptosis induction in some cancer cell lines over normal ones through suppression of some oncogenic clients of Hsp70, representing a new class of antitumor candidates. Hsp70-Bim PPI exhibited cancer-dependent role as a potential anti-cancer target.
