Adaptation of the Kinome Promotes Resistance to BET Bromodomain Inhibitors in Ovarian Cancer
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ABSTRACT: Small molecule BET bromodomain inhibitors (BETi) are actively being pursued in clinical trials for the treatment of a variety of cancers, however, the mechanisms of resistance to targeted BET protein inhibitors remain poorly understood. Using a novel mass spectrometry approach that globally measures kinase signaling at the proteomic level, we evaluated the response of the kinome to targeted BET inhibitor treatment in a panel of BRD4-dependent ovarian carcinoma (OC) cell lines. Despite initial inhibitory effects of BETi, OC cells acquired resistance following sustained treatment with the BETi, JQ1. Through application of Multiplexed Inhibitor Beads (MIBs) and mass spectrometry, we demonstrate that BETi resistance is mediated by adaptive kinome reprogramming, where activation of compensatory pro-survival kinase networks overcomes BET protein inhibition. Furthermore, drug combinations blocking these kinases may prevent or delay the development of drug resistance and enhance the efficacy of BET inhibitor therapy. RNAseq was employed to identify changes in kinase RNA expression following short term (48h) or chronic (JQ1R) JQ1 treatment in three different ovarian cancer cell lines.
Project description:Small molecule BET bromodomain inhibitors (BETi) are actively being pursued in clinical trials for the treatment of a variety of cancers, however, the mechanisms of resistance to targeted BET protein inhibitors remain poorly understood. Using a novel mass spectrometry approach that globally measures kinase signaling at the proteomic level, we evaluated the response of the kinome to targeted BET inhibitor treatment in a panel of BRD4-dependent ovarian carcinoma (OC) cell lines. Despite initial inhibitory effects of BETi, OC cells acquired resistance following sustained treatment with the BETi, JQ1. Through application of Multiplexed Inhibitor Beads (MIBs) and mass spectrometry, we demonstrate that BETi resistance is mediated by adaptive kinome reprogramming, where activation of compensatory pro-survival kinase networks overcomes BET protein inhibition. Furthermore, drug combinations blocking these kinases may prevent or delay the development of drug resistance and enhance the efficacy of BET inhibitor therapy.
Project description:Targeting the epigenome to modulate gene expression programs driving cancer development has emerged as an exciting avenue for therapeutic intervention. Pharmacological inhibition of the bromodomain and extraterminal (BET) family of chromatin adapter proteins has proven effective in this regard, suppressing growth of diverse cancer types mainly through downregulation of the c-MYC oncogene and its downstream transcriptional program. While initially effective, resistance to BET inhibitors (BETi) typically occurs through mechanisms that reactivate MYC expression. We have previously shown that lung adenocarcinoma (LAC) is inhibited by JQ1 through suppression of FOSL1, suggesting that the epigenetic landscape of tumor cells from different origins and differentiation states influences BETi response. Here, we assessed how these differences affect mechanisms of BETi resistance through the establishment of isogenic pairs of JQ1 sensitive and resistant LAC cell lines. We found that resistance to JQ1 in LAC occurs independent of FOSL1 while MYC levels remain unchanged between resistant cells and their JQ1 treated parental counterparts. Furthermore, while epithelial-mesenchymal transition (EMT) is observed upon resistance, TGF- induced EMT did not confer resistance in JQ1 sensitive LAC lines, suggesting this is a consequence, rather than a driver of BETi resistance in our model systems. Importantly, siRNA knockdown demonstrated that JQ1 resistant cell lines are still dependent on BRD4 expression and we found that phosphorylation of BRD4 is elevated in resistant LACs, identifying casein kinase 2 (CK2) as a candidate protein mediating this effect. Inhibition of CK2, as well as downstream transcriptional targets of phosphorylated BRD4 - including AXL and activators of the PI3K pathway - synergize with JQ1 to inhibit BETi resistant LAC. Overall, this demonstrates that the mechanism of resistance to BETi varies depending on cancer type, with LAC cells developing JQ1 resistance independent of MYC re-activation, and identifying CK2 phosphorylation of BRD4 as a potential target to overcome resistance in this cancer.
Project description:Atherosclerosis is an important pathological factor in the development of cardiovascular diseases. In addition to increased plasma lipid concentrations, irregular/oscillatory shear stress and inflammatory processes trigger pathophysiological changes. Inhibitors of the transcription modulatory bromo- and extra-terminal domain (BET) protein family (BETi) could offer a possible therapeutic approach due to their anti-inflammatory properties. In this study, the influence of laminar shear stress, inflammation and BETi on human endothelial cells in an atherosclerosis in vitro model was investigated using global protein expression profiling. For this purpose, human umbilical cord derived vascular endothelial cells (HUVEC) were treated with TNFα to mimic the inflammatory condition and were exposed to 24h laminar shear stress in the presence or absence of a BRD4 inhibitor, JQ1. Data-independent acquisition mass spectrometry (DIA-MS) alloqed us to quantify 3316 proteins for further statistical analysis. Differentially regulated proteins indicate a clear influence of inflammation and shear stress on human endothelial cells. Overall, application of JQ1 is led to significant changes in the proteome, including a strong anti-inflammatory response as well as a potentially negative impact on atherosclerosis formation. To our knowledge, this is the first proteomics study on HUVEC which investigates the influence of shear stress and BET inhibition in TNFα inflammatory endothelial cell culture model.
Project description:Bromodomain and extra terminal protein inhibitors (BETi) are epigenetic therapies aimed to target dysregulated gene expression in cancer cells. Despite early success of BETi in a range of malignancies, the development of drug resistance may limit their clinical application. We evaluated the mechanisms of BETi resistance in uveal melanoma (UM), a disease with little treatment options, using two approaches: a high-throughput combinatorial drug screen with the clinical BET inhibitor PLX51107, and RNA sequencing of BETi-resistant cells. We found that the NF-kB inhibitors synergistically sensitized UM cells to PLX51107 treatment. Furthermore, genes involved in NF-kB signaling were upregulated in BETi-resistant cells and the transcription factor CEBPD contributed to the mechanism of resistance. These findings suggest that inhibitors of NF-kB signaling may improve the efficacy of BET inhibition in patients with advanced UM.
Project description:Mutation or deletion of Neurofibromin (NF1), an inhibitor of RAS signaling, frequently occurs in epithelial ovarian cancer (EOC), supporting therapies that target downstream RAS effectors, such as the RAF-MEK-ERK pathway. However, no comprehensive studies have been carried out testing the efficacy of MEK inhibition in NF1-deficient EOC. Here, we performed a detailed characterization of MEK inhibition in NF1-deficient EOC cell lines using kinome profiling and RNA sequencing. Our studies showed MEK inhibitors were ineffective at providing durable growth inhibition in NF1-deficient cells due to kinome reprogramming. MEKi-mediated destabilization of FOSL1 resulted in induced expression of RTKs and their downstream RAF and PI3K signaling overcoming MEKi therapy. MEKi synthetic enhancement screens identified BRD2 and BRD4 as integral mediators of the MEKi-induced RTK signatures. Inhibition of BET proteins using BET bromodomain inhibitors (BETi) blocked MEKi-induced RTK reprogramming, indicating BRD2 and BRD4 represent promising therapeutic targets in combination with MEKi to block resistance due to kinome reprogramming in NF1-deficient EOC.
Project description:Small molecule inhibitors of the bromodomain and extraterminal (BET) family of proteins are in clinical trials for a variety of cancers, but patient selection strategies are limited. This is due in part to the heterogeneity of response following BET inhibition (BETi), which includes differentiation, senescence, and cell death in subsets of cancer cell lines. To elucidate the dominant features defining response to BETi, we carried out phenotypic and gene expression analysis of both treatment naïve cell lines and engineered tolerant lines. We found that both de novo and acquired tolerance to BET inhibition are driven by the robustness of the apoptotic response and that genetic or pharmacological manipulation of the apoptotic signaling network can modify the phenotypic response to BETi. We further identify that ordered expression of the apoptotic genes BCL2, BCL2L1, and BAD significantly predicts response to BETi. Our findings highlight the role of the apoptotic network in response to BETi, providing a molecular basis for patient stratification and combination therapies. Gene expression profiling of A375 melanoma cells or NOMO-1 AML cells treated with DMSO or the BET inhibitor, CPI203. Also, gene expression profiling of the respective derived BETi-tolerant cells treated with DMSO or CPI203.
Project description:To determine the global transcriptome changes in mantle cell lymphoma cells following treatment with the BET bromodomain antagonist, JQ1 Mantle Cell Lymphoma (MCL) cells exhibit increased B cell receptor and NFkB activities. The BET protein BRD4 is essential for the transcriptional activity of NFkB. Here, we demonstrate that treatment with the BET protein bromodomain antagonist (BA) JQ1 attenuates MYC and CDK4/6, inhibits the nuclear RelA levels and the expression of NFκB target genes including Brutonâs Tyrosine Kinase (BTK) in MCL cells. While lowering the levels of the anti-apoptotic BCL2 family proteins, BA treatment induces the pro-apoptotic protein BIM and exerts dose-dependent lethality against cultured and primary MCL cells. Co-treatment with BA and the BTK inhibitor ibrutinib synergistically induces apoptosis of MCL cells. Compared to each agent alone, co-treatment with BA and ibrutinib markedly improved the median survival of mice engrafted with the MCL cells. BA treatment also induced apoptosis of the in vitro isolated, ibrutinib-resistant MCL cells which overexpress CDK6, BCL2, Bcl-xL, XIAP and AKT, but lack ibrutinib resistance-conferring BTK mutation. Co-treatment with BA and panobinostat (pan-histone deacetylase inhibitor) or palbociclib (CDK4/6 inhibitor) or ABT-199 (BCL2 antagonist) synergistically induced apoptosis of the ibrutinib-resistant MCL cells. These findings highlight and support further in vivo evaluation of the efficacy of the BA-based combinations with these agents against MCL, including ibrutinib-resistant MCL. MO2058 cells treated with vehicle, 250 nM or 1000 nM JQ1 for 8 hours. Samples were acquired and analyzed in duplicate.
Project description:The bromodomain and extra terminal domain (BET) family of proteins, including BRD2, BRD3, and BRD4, play a key role in many cellular processes, including inflammatory gene expression, mitosis, and viral/host interaction by controlling the assembly of histone acetylation-dependent chromatin complexes. Previous studies have shown that multiple BET inhibitors (BETi), including JQ1, have therapeutic effects in cancer and cardiovascular diseases. Some BETi have entered different phases of clinical trials. Pharmacologically, JQ1 functions by displacing BET proteins from chromatin by competitively binding to the acetyl-lysine recognition pocket of BET bromodomains. JQ1 has been used as a chemical probe to investigate the role of BET bromodomains in the transcriptional regulation of cardiovascular diseases. For example, JQ1 has been shown to attenuates inflammation and experimental atherosclerosis (Mol Cell. 2014 Oct 23; 56(2): 219–231.). JQ1 has also recently been shown to reduce EndoMT and cardiac fibrosis (J Mol Cell Cardiol. 2019 Feb;127:83-96.). However, the molecular targets of JQ1 dependent or independent of BRD4 remains unknown. To depict the transcriptomic signature of JQ1 in human endothelial cells, we observed a vasoprotective and atheroprotective transcriptome by JQ1 treatment using genome-wide RNA-seq based transcriptomic profiling. JQ1 is a magic bullet in cardiovascular disease prevention. Further elucidation of new molecular targets of JQ1 will lead to the identification of potentially new therapeutic targets to treat cardiovascular diseases.
Project description:Triple negative breast cancer (TNBC) is heterogeneous with patients exhibiting at least two molecular subtypes, basal-like (BL) and claudin-low (CL). MEK inhibitor (MEKi) treatment of BL and CL cell lines and mouse model tumors induced subtype-specific alterations in overall kinome activity referred to as protein kinase reprogramming. BL- and CL-specific reprogramming involving increases in receptor tyrosine kinases was also seen in TNBC patients comparing tumor samples before and after a one week treatment with the MEKi, trametinib. Combination of kinase inhibitors targeted to the BL and CL reprogrammed signatures would need to be individually selected due to the heterogeneous resiliency of BL and CL kinomes. To overcome this “reprogramming dilemma” we targeted the transcriptional co-activator BRD4 with BET bromodomain inhibitors, JQI and IBET151; both strongly inhibited kinome reprogramming and onset of MEKi resistance in BL and CL cells. Targeting chromatin modifiers may therapeutically block resistance due to kinome reprogramming.BL and CL TNBC are commonly treated as a single disease despite genomic studies showing they represent distinct molecular subtypes1. Recent Cancer Genome Atlas data demonstrated that the 518 protein kinases in the human genome (the kinome) were infrequently mutated in BL breast cancer; however, EGFR, KRAS and BRAF were amplified in 22, 32 and 31% of BL tumors, respectively. These findings are consistent with frequent activation of the BRAF-MEK-ERK pathway in TNBC2,3 and inhibitors targeting kinases in this pathway are currently in clinical trials for TNBC. As single agents, targeted kinase inhibitors generally fail to sustain durable responses when used to treat a range of human cancers including TNBC4-6. Onset of kinase inhibitor resistance can be due to selection of mutations in the targeted kinase7,8, activating mutations or amplification of RAS or downstream kinases9,10 or kinome reprogramming, a process in which there are system-wide changes in kinase networks11-13. Each of these resistance mechanisms allows the cancer cell to circumvent the targeted inhibition of specific kinases14. We previously developed chemical, proteomic methods that assay the activation state of protein kinases en masse15,16. Our methods utilize ¬Multiplexed Inhibitor Beads (MIBs), mixtures of covalently immobilized, linker adapted, kinase inhibitors. The immobilized inhibitors are primarily type I kinase inhibitors that preferentially bind activated (versus inactive) kinase17. Kinase capture is highly reproducible and is a function of kinase affinity for different immobilized inhibitors as well as the kinase activation state. Activated kinases preferentially bind, inactive kinases do not. By coupling MIB capture with mass spectrometry (MIB/MS), the technique allows quantitative interrogation of hundreds of kinases in a single mass spectrometry run. This also interrogates kinases known by sequence but which have been understudied due to lack of reagents such as specific phospho-antibodies. We report here both in preclinical models and patients that BL and CL TNBC have different baseline kinome activation states and both respond differently to MEKi with subtype-specific tyrosine kinase reprogramming. To avoid treatment strategy that uses multiple kinase inhibitors in individual patients, we discovered a novel pharmacologic strategy to block the initial reprogramming response to MEKi involving inhibition of epigenetic processes.
Project description:BET bromodomain inhibitors effectively kill several types of cancer cells. However, the underlying mechanism of BET inhibition resistance remains obscure. We sought to identify the gene expression change upon treatment of JQ1, a well-known BET inhibitor, in basal-like breast cancer cells. In this dataset, we used RNA-sequencing to characterize the mRNA expression profiles from DMSO and JQ1-treated MDA-MB-231 breast tumor cells.