AbstractAberrant activation or overexpression of histone deacetylase (HDAC) isoenzymes trigger disruptions of the functional acetylation landscape, therefore contributing to the development of numerous cancers. Accordingly, pan- or selective HDAC inhibitors (HDACi) represent a powerful class of epigenetically active therapeutic drugs that have already demonstrated promising anti-cancer properties in pre-clinical studies and are undergoing clinical trials for the therapy of many cancers. The main goal of this project is to develop new therapeutic approaches for the treatment of hematological malignancies combining HDACi to targeted therapies.
In this study, we assessed the anti-cancer activity of the novel hydroxamate-based pan-HDACi MAKV-8, which complied with the Lipinski’s “rule of 5”, in various chronic myeloid leukemia (CML) cell lines alone or in combination with imatinib. We validated the in vitro HDAC inhibitory potential of MAKV-8 and demonstrated efficient binding to the ligand-binding pocket of HDAC isoenzymes by docking analyses. In cellulo, MAKV-8 enhanced target protein acetylation, displayed cytostatic and cytotoxic properties, and triggered concomitant ER stress/protective autophagy leading to canonical caspase-dependent apoptosis. Considering the specific up-regulation of selected HDACs in LSCs from CML patients, we investigated the therapeutic potential of MAKV-8 in combination with imatinib against CML cells. First, we highlighted a differential toxicity of a co-treatment with MAKV-8 and imatinib in CML versus healthy cells. We also showed that beclin 1 knockdown prevented MAKV-8-imatinib combination-induced apoptosis. Moreover, MAKV-8 and imatinib co-treatment reduced BCR-ABL-related signaling pathways involved in CML cell growth and survival. Since our results showed that LSCs from CML patients overexpressed c-MYC, MAKV-8-imatinib co-treatment-induced c-MYC down-regulation was importantly accompanied with reduced LSC population. In vivo, tumor growth of xenografted K-562 cells in zebrafish was completely abrogated upon combined treatment with MAKV-8 and imatinib.
We also demonstrated that MAKV-15, a new hydroxamate-based compound derived from tubastatin A, acts as a potent and selective HDAC6i in vitro. Accordingly, MAKV-15 increases preferentially (about 10 times) the acetylation of the HDAC6 substrate α-tubulin in comparison to a non-HDAC6 substrate in cellulo. Interestingly, inhibiting selectively HDAC6 activity is insufficient to trigger any anti-cancer effects. Nevertheless, stronger accumulation of poly-ubiquitinated proteins accompanied with a potentiation of the anti-cancer effects are observed upon co-treatment of multiple myeloma cells with MAKV-15 and bortezomib, suggesting a potential sensitization of cells to a third compound. However, the variety of responses to tri-therapies highlights the heterogeneity among MM cell lines and suggests distinct mechanisms of action that require further investigations.
Collectively, the present findings provide a rational basis to further assess the potential of HDACi in combination treatments as novel therapeutic approaches for hematological malignancies.
|Date of Award||22 Nov 2019|
|Sponsors||FRS-FNRS-Télévie, Fondation de Recherche Cancer et Sang (FRCS), Recherches Scientifiques Luxembourg (RSL), Fondation Lions Luxembroug & A Heart for cancer-sick children association|
|Supervisor||Michael Schnekenburger (Supervisor), Marc DIEDERICH (Co-Supervisor), Carine MICHIELS (Co-Supervisor), Thierry ARNOULD (President), Pierre Sonveaux (Jury), Johan Wouters (Jury), Jean-Pierre Gillet (Jury) & Mario Dicato (Jury)|