gsk1210151a and Neoplasms

BET inhibitor (BETi) has potential therapeutic effects on human cancer especially in breast cancer. However, the detailed mechanisms remain unclear. Herein, we found that BETi JQ1 and I-BET-151 (I-BET) activated ATF2 through JNK1/2 pathway in breast cancer cells MDA-MB-231 (MB-231). In addition, overexpression of ATF2 blocked the reduction of cell viability induced by JQ1 or I-BET in breast cancer MB-231 and BT-549 cells, cervical cancer HeLa cells and lung cancer A549 cells. The induction of cell death by BETi was also attenuated by ATF2 in MB-231 and BT-549 cells. By contrast, depletion of ATF2 increased cancer cell sensitivity to BETi. In MB-231 cells xenograft model, ATF2 significantly inhibited the anti-tumor effects of JQ1. By detection of the oxidized form gluthione, malondialdehyde and lipid ROS, we showed that overexpression of ATF2 inhibited ferroptosis induced by BETi, whereas depletion of ATF2 promoted ferroptosis by BETi. Furthermore, the underlying mechanisms of ATF2-reduced ferroptosis were investigated. Overexpressed and depleted ATF2 were found to significantly upregulate and downregulate NRF2 protein and mRNA expression, respectively. The significantly positive correlations between NRF2 and ATF2 gene expression were found in breast, lung and cervical cancer tissues from TCGA database. In NRF2-depleted MB-231 cells, ATF2 failed to attenuate JQ1-stimulated ferroptosis. All these results suggested that ATF2 inhibited BETi-induced ferroptosis by increasing NRF2 expression. Altogether, our findings illustrated ATF2 suppressed ani-tumor effects of BETi in a negative feedback manner by attenuating ferroptosis. BETi combined with ATF2 or NRF2 inhibitor might be a novel strategy for treatment of human cancer.

Topics: A549 Cells; Activating Transcription Factor 2; Animals; Antineoplastic Agents; Azepines; Breast Neoplasms; Cell Line, Tumor; Drug Resistance, Neoplasm; Feedback, Physiological; Female; Ferroptosis; HeLa Cells; Heterocyclic Compounds, 4 or More Rings; Humans; MAP Kinase Signaling System; Mice; Mice, Nude; Neoplasms; NF-E2-Related Factor 2; Proteins; RNA, Messenger; Triazoles; Xenograft Model Antitumor Assays

Mutations in succinate dehydrogenase B (SDHB) gene are frequently observed in several tumors and associated with poor prognosis in these tumors. Therefore, drugs effective for SDHB-deficient tumors could fulfill an unmet medical need. In addition, such drugs would have an advantage in that selection of patients with SDHB-mutant cancer could increase the probability of success in clinical trials. Currently, however, the characteristics of SDHB-deficient cancers are not completely understood. Here, we established SDHB knockout cancer cell lines from human colon cancer HCT116 cells using the clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 knockout system, and clarified its metabolic characteristics.In the SDHB knockout cells, succinate was accumulated and fumarate was decreased. The oxygen consumption rate was decreased while the extracellular acidification rate was increased in the SDHB knockout cells. Accordingly, an enhanced glycolysis pathway in the SDHB knockout cells was demonstrated by metabolomics analysis. Tracer experiments showed bidirectional metabolic flow in the tricarboxylic acid (TCA) cycle, possibly to maintain the necessary amounts of metabolites in the SDHB knockout cells. The proliferation of SDHB knockout cells was suppressed by a glycolysis inhibitor but not by a mitochondrial inhibitor. Additionally, partial dependence on glutaminolysis was observed in the SDHB knockout cells. Compound screening revealed that a bromodomain and extra-terminal (BET) inhibitor, which downregulated c-Myc, suppressed the growth of the SDHB knockout cells more potently than that of control cells. These findings provide an understanding of the metabolic characteristics of SDHB-deficient cancer and its vulnerabilities, which may lead to new therapeutic options.

Topics: Antineoplastic Agents; Azepines; Benzodiazepines; Citric Acid Cycle; CRISPR-Cas Systems; Dehydroepiandrosterone; Fumarates; Gene Knockout Techniques; Glucosephosphate Dehydrogenase; Glycolysis; HCT116 Cells; Heterocyclic Compounds, 4 or More Rings; Humans; Isoenzymes; L-Lactate Dehydrogenase; Lactate Dehydrogenase 5; Metabolomics; Mitochondria; Mutation; Neoplasms; Oxygen Consumption; Phenformin; Phosphoglycerate Dehydrogenase; Proto-Oncogene Proteins c-myc; RNA Interference; RNA, Small Interfering; Succinate Dehydrogenase; Succinic Acid; Triazoles

Recent studies suggest that BET inhibitors are effective anti-cancer therapeutics. Here we show that BET inhibitors are effective against murine primary mammary tumors, but not pulmonary metastases. BRD4, a target of BET inhibitors, encodes two isoforms with opposite effects on tumor progression. To gain insights into why BET inhibition was ineffective against metastases the pro-metastatic short isoform of BRD4 was characterized using mass spectrometry and cellular fractionation. Our data show that the pro-metastatic short isoform interacts with the LINC complex and the metastasis-associated proteins RRP1B and SIPA1 at the inner face of the nuclear membrane. Furthermore, histone binding arrays revealed that the short isoform has a broader acetylated histone binding pattern relative to the long isoform. These differential biochemical and nuclear localization properties revealed in our study provide novel insights into the opposing roles of BRD4 isoforms in metastatic breast cancer progression.

Topics: Animals; Apoptosis Regulatory Proteins; Cell Cycle Proteins; Cell Line, Tumor; Cell Nucleus; Chromosomal Proteins, Non-Histone; Disease Models, Animal; Female; GTPase-Activating Proteins; Heterocyclic Compounds, 4 or More Rings; Histones; Humans; Intracellular Signaling Peptides and Proteins; Membrane Proteins; Mice; Microtubule-Associated Proteins; N-Terminal Acetyltransferase E; N-Terminal Acetyltransferases; Neoplasm Metastasis; Neoplasms; Nuclear Envelope; Nuclear Proteins; Protein Binding; Protein Isoforms; Protein Transport; Transcription Factors; Tumor Burden