Abstract
The human mitochondrial ClpXP protease complex (HsClpXP) has recently attracted major attention as a target for novel anti-cancer therapies. Despite its important role in disease progression, the cellular role of HsClpXP is poorly characterized and only few small molecule inhibitors have been reported. Herein, we screened previously established S. aureus ClpXP inhibitors against the related human protease complex and identified potent small molecules against human ClpXP. The hit compounds showed anti-cancer activity in a panoply of leukemia, liver and breast cancer cell lines. We found that the bacterial ClpXP inhibitor 334 impairs the electron transport chain (ETC), enhances the production of mitochondrial reactive oxygen species (mtROS) and thereby promotes protein carbonylation, aberrant proteostasis and apoptosis. In addition, 334 induces cell death in re-isolated patient-derived xenograft (PDX) leukemia cells, potentiates the effect of DNA-damaging cytostatics and re-sensitizes resistant cancers to chemotherapy in non-apoptotic doses.
Highlights
Abbreviations acute myeloid leukemia (AML) Acute myeloid leukemia CDDO-ME Bardoxolone methyl C/EBP Homologous Protein (CHOP) C/EBP homologous protein chronic myeloid leukemia (CML) Chronic myeloid leukemia ER Endoplasmatic reticulum electron transport chain (ETC) Electron transport chain hepatocellular carcinoma (HCC) Hepatocellular carcinoma HsClpXP Human ClpXP HspX Heat shock protein X high-throughput screen (HTS) High-throughput screen MMP Mitochondrial membrane potential
MtUPR Mitochondrial unfolded protein response mass spectrometry (MS) Mass spectrometry oxygen consumption rate (OCR) Oxygen consumption rate PARP Poly [ADP-ribose] polymerase peripheral blood mononuclear cells (PBMCs) Peripheral blood mononuclear cell patient-derived xenograft (PDX) Patient-derived xenograft reactive oxygen species (ROS) Reactive oxygen species S. aureus ClpXP (SaClpXP) Staphylococcus aureus (S. aureus) ClpXP SILAC Stable isotope labeling with amino acids in cell culture T-ALL T-cell acute lymphoblastic leukemia TEM Transmission electron microscopy VCR Vincristine-resistant
The mitochondrial proteolytic complex ClpXP has recently gained attention in the search for novel therapeutic targets for the treatment of cancer[4]. This prominent proteolytic machinery consists of two stacked heptameric rings of the caseinolytic peptidase ClpP that associate with the hexameric AAA + (ATPase associated with diverse cellular activities) unfoldase ClpX to form a fully functional proteolytic c omplex[5,6]
Summary
Abbreviations AML Acute myeloid leukemia CDDO-ME Bardoxolone methyl CHOP C/EBP homologous protein CML Chronic myeloid leukemia ER Endoplasmatic reticulum ETC Electron transport chain HCC Hepatocellular carcinoma HsClpXP Human ClpXP HspX Heat shock protein X HTS High-throughput screen MMP Mitochondrial membrane potential. The mitochondrial proteolytic complex ClpXP has recently gained attention in the search for novel therapeutic targets for the treatment of cancer[4] This prominent proteolytic machinery consists of two stacked heptameric rings of the caseinolytic peptidase ClpP that associate with the hexameric AAA + (ATPase associated with diverse cellular activities) unfoldase ClpX to form a fully functional proteolytic c omplex[5,6]. Compounds targeting the whole human ClpXP complex rather than just the ClpP subunits bear a great potential as novel drug candidates To this end we set out to reinvestigate a previous high-throughput screen (HTS) conducted to identify S. aureus ClpXP (SaClpXP) inhibitors, which target human ClpXP15. The compound exhibited anticancer activity, induced cell death in re-isolated patient-derived xenograft (PDX) leukemia cells, potentiated the effect of DNA-damaging cytostatics and re-sensitized chemoresistant cancers to therapy
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