ABSTRACT
Avoidance of apoptosis is critical for the development and sustained growth of tumours. The pro-survival protein myeloid cell leukemia 1 (MCL1) is overexpressed in many cancers, but the development of small molecules targeting this protein that are amenable for clinical testing has been challenging. Here we describe S63845, a small molecule that specifically binds with high affinity to the BH3-binding groove of MCL1. Our mechanistic studies demonstrate that S63845 potently kills MCL1-dependent cancer cells, including multiple myeloma, leukaemia and lymphoma cells, by activating the BAX/BAK-dependent mitochondrial apoptotic pathway. In vivo, S63845 shows potent anti-tumour activity with an acceptable safety margin as a single agent in several cancers. Moreover, MCL1 inhibition, either alone or in combination with other anti-cancer drugs, proved effective against several solid cancer-derived cell lines. These results point towards MCL1 as a target for the treatment of a wide range of tumours.
Subject(s)
Antineoplastic Agents/pharmacology , Antineoplastic Agents/therapeutic use , Models, Biological , Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors , Neoplasms/drug therapy , Neoplasms/pathology , Pyrimidines/pharmacology , Pyrimidines/therapeutic use , Thiophenes/pharmacology , Thiophenes/therapeutic use , Animals , Antineoplastic Agents/administration & dosage , Apoptosis/drug effects , Cell Line, Tumor , Female , Humans , Leukemia/drug therapy , Leukemia/metabolism , Leukemia/pathology , Lymphoma/drug therapy , Lymphoma/metabolism , Lymphoma/pathology , Male , Mice , Models, Molecular , Multiple Myeloma/drug therapy , Multiple Myeloma/metabolism , Multiple Myeloma/pathology , Myeloid Cell Leukemia Sequence 1 Protein/chemistry , Myeloid Cell Leukemia Sequence 1 Protein/metabolism , Neoplasms/metabolism , Pyrimidines/administration & dosage , Thiophenes/administration & dosage , Xenograft Model Antitumor Assays , bcl-2 Homologous Antagonist-Killer Protein/metabolism , bcl-2-Associated X Protein/metabolismABSTRACT
In order to explore the molecular interaction between cyclothiazide (CTZ) and gamma-aminobutyric acidA (GABAA) receptors, possibly underlying inhibition of GABAA receptor currents, [3H]-CTZ was synthesized. Binding of [3H]-CTZ to rat brain synaptic membranes could be observed only in the presence of the GABAA receptor antagonist (-)[1S,9R]-bicuculline methiodide (BMI) (EC(50,BMI)=500+/-80microM). GABA decreased [(3)H]-CTZ binding induced by the presence 300microM and 3mM BMI with IC(50,GABA) values of 300+/-50microM and 5.0+/-0.7mM, respectively. Binding of CTZ to [3H]-CTZ labeled sites was characterized by IC(50,CTZ) values of 0.16+/-0.03muM ([BMI]=300microM) and 7.0+/-0.5microM ([BMI]=3mM). Binding of the diastereomeric fraction [3H]-(3R,1'S,4'S,5'R+3S,1'R,4'R,5'S)-CTZ induced by 3mM BMI was quantitatively the more significant in cerebrocortical and hippocampal membranes. It was characterized by IC(50,CTZ)=80+/-15nM and IC(50,GABA)=13+/-3mcapital EM, Cyrillic. In the absence of BMI, CTZ (1mM) significantly decreased GABA-induced enhancement of [3H]-flunitrazepam binding. Our findings suggest that functional inhibition may occur through binding of CTZ to an allosteric site of GABAA receptors. This allosteric site is possibly emerged in the receptor conformation, stabilized by BMI binding.
