1. Selective BH3 mimetics synergize with BET inhibition to induce mitochondrial apoptosis in rhabdomyosarcoma cells
- Author
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Ufuk Erdogdu, Nadezda Dolgikh, Stephanie Laszig, Vinzenz Särchen, Michael T. Meister, Marek Wanior, Stefan Knapp, and Cathinka Boedicker
- Subjects
BH3 mimetics ,PBMC, peripheral blood mononuclear cell ,Cancer Research ,chemical and pharmacologic phenomena ,Antineoplastic Agents ,Nerve Tissue Proteins ,Receptors, Cell Surface ,Apoptosis ,PI, propidium iodide ,BRD4, bromodomain-containing protein 4 ,MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide ,Biomimetics ,hemic and lymphatic diseases ,Cell Line, Tumor ,Proto-Oncogene Proteins ,Rhabdomyosarcoma ,BRD, bromodomain ,Humans ,BET proteins ,RC254-282 ,Original Research ,EV, empty vector ,zVAD.fmk, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone ,ATCC, American Type Culture Collection ,mBCL-2, murine BCL-2 ,CI, combination index ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,hemic and immune systems ,Drug Synergism ,BET protein, Bromo- and Extra-Terminal protein ,Peptide Fragments ,Mitochondria ,ERMS, embryonal rhabdomyosarcoma ,ARMS, alveolar rhabdomyosarcoma ,RMS, rhabdomyosarcoma ,FCS, fetal calf serum ,biological phenomena, cell phenomena, and immunity - Abstract
Highlights • Co-inhibition of BET proteins and anti-apoptotic BCL-2 proteins induces apoptosis in RMS. • JQ1 and BH3-mimetics synergistically induce cell death in RMS. • Cell death is caspase-dependent and displays hallmarks of intrinsic apoptosis. • JQ1/A-1331852-mediated apoptosis is dependent on BIM and NOXA. • JQ1/S638450-mediated apoptosis is dependent on BIM but not NOXA., BH3 mimetics are promising novel anticancer therapeutics. By selectively inhibiting BCL-2, BCL-xL, or MCL-1 (i.e. ABT-199, A-1331852, S63845) they shift the balance of pro- and anti-apoptotic proteins in favor of apoptosis. As Bromodomain and Extra Terminal (BET) protein inhibitors promote pro-apoptotic rebalancing, we evaluated the potential of the BET inhibitor JQ1 in combination with ABT-199, A-1331852 or S63845 in rhabdomyosarcoma (RMS) cells. The strongest synergistic interaction was identified for JQ1/A-1331852 and JQ1/S63845 co-treatment, which reduced cell viability and long-term clonogenic survival. Mechanistic studies revealed that JQ1 upregulated BIM and NOXA accompanied by downregulation of BCL-xL, promoting pro-apoptotic rebalancing of BCL-2 proteins. JQ1/A-1331852 and JQ1/S63845 co-treatment enhanced this pro-apoptotic rebalancing and triggered BAK- and BAX-dependent apoptosis since a) genetic silencing of BIM, BAK or BAX, b) inhibition of caspase activity with zVAD.fmk and c) overexpression of BCL-2 all rescued JQ1/A-1331852- and JQ1/S63845-induced cell death. Interestingly, NOXA played a different role in both treatments, as genetic silencing of NOXA significantly rescued from JQ1/A-1331852-mediated apoptosis but not from JQ1/S63845-mediated apoptosis. In summary, JQ1/A-1331852 and JQ1/S63845 co-treatment represent new promising therapeutic strategies to synergistically trigger mitochondrial apoptosis in RMS.
- Published
- 2022