Synergistic effect of JQ1 and rapamycin for treatment of human osteosarcoma

Abstract

Bromodomain and extra terminal domain (BET) proteins are important epigenetic regulators facilitating the transcription of genes in chromatin areas linked to acetylated histones. JQ1, a BET protein inhibitor, has antiproliferative activity against many cancers, mainly through inhibition of c-MYC and upregulation of p21. In this research, we investigated the use of JQ1 for human osteosarcoma (OS) treatment. JQ1 significantly inhibited the proliferation and survival of OS cells inducing G1 cell cycle arrest, premature senescence, but little effect on apoptosis. Interestingly, c-MYC protein levels in JQ1-treated cells remained unchanged, whereas the upregulation of p21 protein was still observable. Although effective in vitro, JQ1 alone failed to reduce the size of the MNNG/HOS xenografts in immunocompromised mice. To overcome the resistance of OS cells to JQ1 treatment, we combined JQ1 with rapamycin, an mammalian target of rapamycin (mTOR) inhibitor. JQ1 and rapamycin synergistically inhibited the growth and survival of OS cells in vitro and in vivo. We also identified that RUNX2 is a direct target of bromodomain-containing protein 4 (BRD4) inhibition by JQ1 in OS cells. Chromatin immunoprecipitation (ChIP) showed that enrichment of BRD4 protein around RUNX2 transcription start sites diminished with JQ1 treatment in MNNG/HOS cells. Overexpression of RUNX2 protected JQ1-sensitive OS cells from the effect of JQ1, and siRNA-mediated inhibition of RUNX2 sensitized the same cells to JQ1. In conclusion, our findings suggest that JQ1, in combination with rapamycin, is an effective chemotherapeutic option for OS treatment. We also show that inhibition of RUNX2 expression by JQ1 partly explains the antiproliferative activity of JQ1 in OS cells.

Implication of Inflammation and Epigenetic Readers in Coronary Artery Remodeling in Patients With Pulmonary Arterial Hypertension

“…9 Thus, BRD4 is a key regulator of the proliferation/apoptosis balance 12,13 by modulating gene expression and plays a critical role in post-DNA damage events. 17 In cancer, BRD4 is a known trigger of the osteogenic factor Runt-related transcription factor 2 expression, 18,19 which was recently associated with PAH lung abnormalities (including proliferation and calcification), 20 and, interestingly, BRD4 inhibition by JQ1 suppressed vascular calcification/atherogenic processes in a hypercholesterolemic murine model. 15 Furthermore, in addition to promoting DNA damage, 17 atherogenic processes 15 and increased proliferation, 12,13 BRD4 is also associated with inflammation, diabetes mellitus, obesity, and metabolic abnormalities, 13 all playing a role in VRDs, and particularly in coronary artery disease (CAD).…”

Bromodomain-Containing Protein 4 (BRD4) Inhibition Sensitizes Palomid 529-Induced Anti-Renal Cell Carcinoma Cell Activity in Vitro and in Vivo

“…First, pharmacologic inhibition of BRD4 enhanced Palomid 529-induced 786-O cell death Inhibition of BRD4 could be a fine strategy to sensitize Palomid 529 in RCC cells. Previous studies have established synergistic to additive effects between mTORC1 inhibitors and bromodomain protein inhibition in various human cancers [52][53][54]. For example, Lee et al, reported the synergistic anti-osteosarcoma activity by the BRD4 inhibitor JQ1 and rapamycin [54].…”

“…Previous studies have established synergistic to additive effects between mTORC1 inhibitors and bromodomain protein inhibition in various human cancers [52][53][54]. For example, Lee et al, reported the synergistic anti-osteosarcoma activity by the BRD4 inhibitor JQ1 and rapamycin [54]. Berenguer-Daize et al, reported that OTX015 (a novel BET inhibitor) and the mTORC1 inhibitor everolimus synergisticly inhibited glioblastoma cell growth [52].…”

402 Selective and Reversible Suppression of Intestinal Stem Cell Differentiation by Pharmacological Inhibition of Bet Bromodomains

“…To verify inhibition of BET bromodomains within the small intestine, mice were administered three doses (10 mg/kg) of BETi in 24 hours. Four hours after the last dose, villi and crypts of the small intestine were isolated and qPCR performed to examine the expression of PHF15, a gene that is downregulated upon BET bromodomain inhibition in a wide variety of cell types [16][17][18] . PHF15 expression was decreased by more than 75% in both villi and crypts of mice treated with BETi relative to control, demonstrating effective delivery of BETi throughout the small intestine (Fig.…”