Fig. 5

Cotreatment with the HDAC inhibitor panobinostat and the bromodomain inhibitor OTX015 synergistically suppresses cell growth in GBM cells. a Cotreatment with the HDAC inhibitor panobinostat and the bromodomain inhibitor OTX015 at various indicated dosages synergistically inhibits cell viability in U87 and U251 cells. The combination indices are shown on the left. b Cell proliferation analyses of GBM cells treated with DMSO, panobinostat, OTX015 or panobinostat/OTX015 for 24 h using an EdU incorporation FACS assay. Percentages of EdU+ cells are presented on the bar chart on the right. c Apoptosis analyses of GBM cells treated with DMSO, panobinostat, OTX015 or panobinostat/OTX015 for 48 h by an Annexin-V staining FACS assay. Percentages of Annexin-V+ cells are presented on the bar chart on the right. d qPCR results showing that GBM-associated oncogenic genes related to the mitotic nuclear division, cell division and cell cycle, etc. were significantly downregulated by the combined drug treatment compared with each drug treatment alone in U87 and U251 cells. Blue or red asterisks indicate P-values of panobinsotat or OTX015 treatment alone compared with the combined drug treatment respectively. *p < 0.05, ** p < 0.01, *** p < 0.001, Students’ two-tailed t-test. e qPCR results showing that GBM-associated tumor-suppressive genes related to the FoxO signaling pathway and regulation of interferon-gamma-mediated signaling pathway were significantly upregulated by the combined drug treatment compared with each drug treatment alone in U87 and U251 cells. Blue or red asterisks indicate P-values of panobinsotat or OTX015 treatment alone compared with the combined drug treatment respectively. *p < 0.05, ** p < 0.01, *** p < 0.001, Students’ two-tailed t-test. f Immunoblotting analyses of p-AKT, AKT and c-Myc in GBM cells treated with DMSO, panobinostat, OTX015 or panobinostat/OTX015 for 16 h. g Cotreatment with the HDAC inhibitor panobinostat and the bromodomain inhibitor OTX015 at various indicated dosages synergistically inhibits cell viability in primary GBM cell line. The combination indices are shown on the left