Ricolinostat (ACY‐1215) induced inhibition of aggresome formation accelerates carfilzomib‐induced multiple myeloma cell death |
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Authors: | Yuko Mishima Loredana Santo Homare Eda Diana Cirstea Neeharika Nemani Andrew J. Yee Elizabeth O'Donnell Martin Karl Selig Steven N. Quayle Shirin Arastu‐Kapur Christopher Kirk Lawrence H. Boise Simon S. Jones Noopur Raje |
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Affiliation: | 1. Division of Hematology and Oncology, Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA, USA;2. Department of Pathology, Massachusetts General Hospital, Boston, MA, USA;3. Acetylon Pharmaceuticals, Inc., Boston, MA, USA;4. Onyx Pharmaceuticals, Inc., an Amgen Subsidiary, South San Francisco, CA, USA;5. Winship Cancer Institute of Emory University School of Medicine, Atlanta, GA, USA |
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Abstract: | Proteasome inhibition induces the accumulation of aggregated misfolded/ubiquitinated proteins in the aggresome; conversely, histone deacetylase 6 (HDAC6) inhibition blocks aggresome formation. Although this rationale has been the basis of proteasome inhibitor (PI) and HDAC6 inhibitor combination studies, the role of disruption of aggresome formation by HDAC6 inhibition has not yet been studied in multiple myeloma (MM). The present study aimed to evaluate the impact of carfilzomib (CFZ) in combination with a selective HDAC6 inhibitor (ricolinostat) in MM cells with respect to the aggresome‐proteolysis pathway. We observed that combination treatment of CFZ with ricolinostat triggered synergistic anti‐MM effects, even in bortezomib‐resistant cells. Immunofluorescent staining showed that CFZ increased the accumulation of ubiquitinated proteins and protein aggregates in the cytoplasm, as well as the engulfment of aggregated ubiquitinated proteins by autophagosomes, which was blocked by ricolinostat. Electron microscopy imaging showed increased autophagy triggered by CFZ, which was inhibited by the addition of ACY‐1215. Finally, an in vivo mouse xenograft study confirmed a decrease in tumour volume, associated with apoptosis, following treatment with CFZ in combination with ricolinostat. Our results suggest that ricolinostat inhibits aggresome formation, caused by CFZ‐induced inhibition of the proteasome pathway, resulting in enhanced apoptosis in MM cells. |
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Keywords: | multiple myeloma carfilzomib HDAC6 inhibitor aggresome proteasome inhibitor |
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