DUB3 Promotes BET Inhibitor Resistance and Cancer Progression by Deubiquitinating BRD4

FBP1 binds to the bromodomain of BRD4 to inhibit pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumour that is characteristically unresponsive to most chemotherapeutic regimens. Bromodomain and extra terminal domain (BET) inhibitors that specifically repress the function of BET family proteins, such as BRD4, are under evaluation in clinical trials for their activity in repressing cancer growth. However, resistance to BET inhibitors has hindered their further clinical application in pancreatic cancer. We previously reported that FBP1 contributes to the resistance to BET inhibitors, but the underlying mechanism of this resistance remains unclear. Herein, we demonstrate that FBP1 is a binding partner of BRD4 in pancreatic cancer cells. We reveal that FBP1 binds to the BD2 domain of BD4 in an acetylation-dependent manner. Moreover, we found that Tip60 and HDAC3 were key to the acetylation and de-acetylation of FBP1 at K110 and K113, which are critical for mediating FBP1-BRD4 binding in pancreatic cancer cells. Furthermore, our data indicate that FBP1 decreases the expression of genes downstream of BRD4 to inhibit pancreatic cancer cell progression. Our results, therefore, provide evidence of the novel anti-tumour effect of FBP1 via its blockade of BRD4 function in pancreatic cancer cells.

Bromodomain-containing protein 4 inhibition alleviates matrix degradation by enhancing autophagy and suppressing NLRP3 inflammasome activity in NP cells

An imbalance between matrix synthesis and degradation is the hallmark of intervertebral disc degeneration while inflammatory cytokines contribute to the imbalance. Bromodomain and extra-terminal domain (BET) family is associated with the pathogenesis of inflammation, and inhibition of BRD4, a vital member of BET family, plays an anti-inflammatory role in many diseases. However, it remains elusive whether BRD4 plays a similar role in nucleus pulposus (NP) cells and participates in the pathogenesis of intervertebral disc degeneration. The present study aims to observe whether BRD4 inhibition regulates matrix metabolism by controlling autophagy and NLRP3 inflammasome activity. Besides, the relationship was investigated among nuclear factor κB (NF-κB) signaling, autophagy and NLRP3 inflammasome in NP cells. Here, real-time polymerase chain reaction, western blot analysis and adenoviral GFP-LC3 vector transduction in vitro were used, and it was revealed that BRD4 inhibition alleviated the matrix degradation and increased autophagy in the presence or absence of tumor necrosis factor α. Moreover, p65 knockdown or treatment with JQ1 and Bay11-7082 demonstrated that BRD4 inhibition attenuated NLRP3 inflammasome activity through NF-κB signaling, while autophagy inhibition by bafilomycin A1 promoted matrix degradation and NLRP3 inflammasome activity in NP cells. In addition, analysis of BRD4 messenger RNA expression in human NP tissues further verified the destructive function of BRD4. Simply, BRD4 inhibition alleviates matrix degradation by enhancing autophagy and suppressing NLRP3 inflammasome activity through NF-κB signaling in NP cells.

Enhanced JunD/RSK3 signalling due to loss of BRD4/FOXD3/miR-548d-3p axis determines BET inhibition resistance

BET bromodomain inhibitors (BETi), such as JQ1, have been demonstrated to effectively kill multiple types of cancer cells. However, the underlying mechanisms for BETi resistance remain largely unknown. Our evidences show that JQ1 treatment evicts BRD4 from the FOXD3-localized MIR548D1 gene promoter, leading to repression of miR-548d-3p. The loss of miRNA restores JunD expression and subsequent JunD-dependent transcription of RPS6KA2 gene. ERK1/2/5 kinases phosphorylate RSK3 (RPS6KA2), resulting in the enrichment of activated RSK3 and blockade of JQ1 killing effect. Dual inhibition of MEKs/ERKs or single EGFR inhibition are able to mimic the effect of JunD/RSK3-knockdown to reverse BETi resistance. Collectively, our study indicates that loss of BRD4/FOXD3/miR-548d-3p axis enhances JunD/RSK3 signalling and determines BET inhibition resistance, which can be reversed by targeting EGFR-MEK1/2/5-ERK1/2/5 signalling.

The clinical use of BET inhibitors (BETi) is limited by primary and acquired resistance. Here, the authors report that BETi resistance is determined by JunD/RSK3 signalling activation induced by the loss of BRD4/Foxd3/miR-548d-3p, which can be reverted by targeting the EGFR-MEK-ERK pathway.

Smoothened Promotes Glioblastoma Radiation Resistance Via Activating USP3-Mediated Claspin Deubiquitination

PURPOSE

Glioblastoma (GBM) is one of the most aggressive and lethal cancer types in humans. The standard treatment approach is surgery followed by chemoradiation. However, the molecular mechanisms of innate tumor radioresistance remain poorly understood.

EXPERIMENTAL DESIGN

We tested the expression of Smoothened (Smo) in primary and recurrent GBM tissues and cells. Then, we determined radiation effectiveness against primary and recurrent GBM cells. Lastly, the functional role of Smo in GBM radioresistance was further confirmed by in vitro and in vivo experiments.

RESULTS

We reported that Smo was significantly upregulated in recurrent GBM cell lines and tumor tissues following radiation treatment. Higher Smo expression indicated poor prognosis of GBM patients after radiation treatment. Smo had radioresistance effects in both GBM cells and human tumor xenografts. The mechanisms underlying these effects involved the attenuation of DNA damage repair caused by IR. Importantly, we found that the effect of Smo on radioresistance was mediated by Claspin polyubiquitination and proteasomal degradation, leading to the regulation of ATR-Chk1 signaling. Moreover, we found that Smo reduced Claspin polyubiquitination and proteasomal degradation by promoting USP3 transcription. Furthermore, we demonstrated that the Smo inhibitor GDC-0449 induced radiosensitivity to GBM.

CONCLUSIONS

These data suggest that Smo confers radiation resistance in GBM by promoting USP3 transcription, leading to the activation of Claspin-dependent ATR-Chk1 signaling. These findings identify a potential mechanism of GBM resistance to radiation and suggest a potential therapeutic target for radiation resistance in GBM.

A patent review of BRD4 inhibitors (2013-2019)

Introduction: The bromodomain-containing protein 4 (BRD4), a member of the bromodomain and extra-terminal (BET) family, functions as an 'epigenetic reader' that binds to acetylated lysine (KAc) residues on histone tails sophisticatedly regulating chromatin structure and gene expression. Recently, emerging evidence demonstrates that BRD4 plays a significant role in the occurrence and progression of several malignant human diseases especially cancers, making it a hot target in cancer therapy.Areas covered: This review mainly summarizes the patents of BRD4 inhibitors that have been authorized from 2013 to 2019. The patents are mostly described in terms of chemical structures, molecular mechanisms of action, pharmacological activities and potential clinical applications, including combination therapies. The development of BRD4 inhibitors in the clinical phase has been highlighted. Prospects for further development of more selective BRD4 inhibitors are provided.Expert opinion: In 2013-2019, several previously known chemical scaffolds have been further developed and disclosed. Although many small molecule BRD4 inhibitors with high potency and diverse scaffolds have been developed, the selectivity of most BRD4 inhibitors still needs to be improved. Therefore, the development of more selective small molecule inhibitors or combined use of drugs such as immunotherapy may provide new ideas for drug development.

BRD4 promotes tumor progression and NF-κB/CCL2-dependent tumor-associated macrophage recruitment in GIST

The most commonly occurring sarcoma of the soft tissue is gastrointestinal stromal tumor (GIST). Treatment and prevention of the disease necessitate an understanding of the molecular mechanisms involved. However, the role of BRD4 in the progression of GIST is still unclear. While it is known there are abundant infiltrating tumor-associated macrophages (TAMs) in the tumor microenvironment, the exact role of these cells has yet to be studied. This work showed an upregulation of BRD4 in GIST that was associated with GIST prognosis. Through gain and loss of function studies, it was found that BRD4 promotes GIST growth and angiogenesis in vitro and in vivo. Mechanistically, BRD4 enhances CCL2 expression by activating the NF-κB signaling pathway. Furthermore, this CCL2 upregulation causes recruitment of macrophages into the tumor leading to tumor growth. A likely mechanism for interactions in the GIST microenvironment has been outlined by this work to show the role and potential use of BRD4 as a treatment target in GIST.

Posttranslational regulation of androgen dependent and independent androgen receptor activities in prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer among men in western countries. Androgen receptor (AR) signaling plays key roles in the development of PCa. Androgen deprivation therapy (ADT) remains the standard therapy for advanced PCa. In addition to its ligand androgen, accumulating evidence indicates that posttranscriptional modification is another important mechanism to regulate AR activities during the progression of PCa, especially in castration resistant prostate cancer (CRPC). To date, a number of posttranscriptional modifications of AR have been identified, including phosphorylation (e.g. by CDK1), acetylation (e.g. by p300 and recognized by BRD4), methylation (e.g. by EZH2), ubiquitination (e.g. by SPOP), and SUMOylation (e.g. by PIAS1). These modifications are essential for the maintenance of protein stability, nuclear localization and transcriptional activity of AR. This review summarizes posttranslational modifications that influence androgen-dependent and -independent activities of AR, PCa progression and therapy resistance. We further emphasize that in addition to androgen, posttranslational modification is another important way to regulate AR activity, suggesting that targeting AR posttranslational modifications, such as proteolysis targeting chimeras (PROTACs) of AR, represents a potential and promising alternate for effective treatment of CRPC. Potential areas to be investigated in the future in the field of AR posttranslational modifications are also discussed.

Non-canonical transcriptional consequences of BET inhibition in cancer

Inhibition of the bromo and extra-terminal domain (BET) protein family in preclinical studies has demonstrated that BET proteins are critical for cancer progression and important therapeutic targets. Downregulation of the MYC oncogene, CDK6, BCL2 and FOSL1 are just a few examples of the effects of BET inhibitors that can lead to cell cycle arrest and apoptosis in cancer cells. However, BET inhibitors have had little success in the clinic as a single agent, and there are an increasing number of reports of resistance to BET inhibition emerging after sustained treatment of cancer cells in vitro. Here we summarize the non-canonical consequences of BET inhibition in cancer, and discuss how these may both lead to resistance and inform rational combinations that could greatly enhance the clinical application of these inhibitors.

Akt/mTOR-Mediated Autophagy Confers Resistance To BET Inhibitor JQ1 In Ovarian Cancer

Background

Bromodomain and extra-terminal domain inhibitors like JQ1 have proved to be promising epigenetic agents for the treatment of malignant ovarian carcinoma. However, the resistance of ovarian cancer cells to BET inhibitors has not been elucidated. In this study, we investigated the potential mechanisms underlying the resistance of ovarian cancer cell lines to the BET inhibitor JQ1.

Materials and methods

We evaluated the apoptotic and proliferative response of four ovarian cancer cell lines to JQ1. The cell lines were designated as resistant (A2780 and HO-8910) and sensitive groups (SKOV-3 and HEY). Further experiments detected the different levels of JQ1-induced autophagy. Anti-tumour effect of the combination of JQ1 and autophagy inhibitors was tested both in vitro and in vivo.

Results

In the JQ1-sensitive group, JQ1 effectively inhibited proliferation and apoptosis in a concentration-dependent manner. Conversely, JQ1 showed modest inhibition of proliferation and negligible apoptosis in the resistant group. We detected increased LC3-II lipidation, autophagosome formation, upregulation of Beclin-1 and ATG5, and downregulation of P62/SQSTM1 in the resistant group. Inhibition of JQ1-induced autophagy by pharmacologic inhibitors 3-MA and CQ enhanced the inhibition of proliferation and significantly increased the apoptosis in the JQ1-resistant group, which was also verified by in vivo experiments, indicating that JQ1-induced autophagy played a cytoprotective role. Inactivation of Akt (Ser473)/mTOR(Ser2448) pathway was associated with JQ1-induced autophagy in the resistant group. Overexpression of Akt1 suppressed autophagy and increased the anti-tumour effect of JQ1.

Conclusion

These findings revealed that JQ1-induced pro-survival autophagy might be a potential mechanism in the resistance of ovarian cancer cells to BET inhibition by JQ1. Combination of JQ1 and autophagy inhibitors could be an effective therapeutic strategy for overcoming BET inhibitor resistance in ovarian cancer.

Cellular and Molecular Mechanisms Underlying Prostate Cancer Development: Therapeutic Implications

Prostate cancer is the most frequent nonskin cancer and second most common cause of cancer-related deaths in man. Prostate cancer is a clinically heterogeneous disease with many patients exhibiting an aggressive disease with progression, metastasis, and other patients showing an indolent disease with low tendency to progression. Three stages of development of human prostate tumors have been identified: intraepithelial neoplasia, adenocarcinoma androgen-dependent, and adenocarcinoma androgen-independent or castration-resistant. Advances in molecular technologies have provided a very rapid progress in our understanding of the genomic events responsible for the initial development and progression of prostate cancer. These studies have shown that prostate cancer genome displays a relatively low mutation rate compared with other cancers and few chromosomal loss or gains. The ensemble of these molecular studies has led to suggest the existence of two main molecular groups of prostate cancers: one characterized by the presence of ERG rearrangements (~50% of prostate cancers harbor recurrent gene fusions involving ETS transcription factors, fusing the 5' untranslated region of the androgen-regulated gene TMPRSS2 to nearly the coding sequence of the ETS family transcription factor ERG) and features of chemoplexy (complex gene rearrangements developing from a coordinated and simultaneous molecular event), and a second one characterized by the absence of ERG rearrangements and by the frequent mutations in the E3 ubiquitin ligase adapter SPOP and/or deletion of CDH1, a chromatin remodeling factor, and interchromosomal rearrangements and SPOP mutations are early events during prostate cancer development. During disease progression, genomic and epigenomic abnormalities accrued and converged on prostate cancer pathways, leading to a highly heterogeneous transcriptomic landscape, characterized by a hyperactive androgen receptor signaling axis.

Super-enhancers: critical roles and therapeutic targets in hematologic malignancies

Super-enhancers (SEs) in a broad range of human cell types are large clusters of enhancers with aberrant high levels of transcription factor binding, which are central to drive expression of genes in controlling cell identity and stimulating oncogenic transcription. Cancer cells acquire super-enhancers at oncogene and cancerous phenotype relies on these abnormal transcription propelled by SEs. Furthermore, specific inhibitors targeting SEs assembly and activation have offered potential targets for treating various tumors including hematological malignancies. Here, we first review the identification, functional significance of SEs. Next, we summarize recent findings of SEs and SE-driven gene regulation in normal hematopoiesis and hematologic malignancies. The importance and various modes of SE-mediated MYC oncogene amplification are illustrated. Finally, we highlight the progress of SEs as selective therapeutic targets in basic research and clinical trials. Some open questions regarding functional significance and future directions of targeting SEs in the clinic will be discussed too.

Bromodomains: a new target class for drug development

Less than a decade ago, it was shown that bromodomains, acetyl lysine 'reader' modules found in proteins with varied functions, were highly tractable small-molecule targets. This is an unusual property for protein-protein or protein-peptide interaction domains, and it prompted a wave of chemical probe discovery to understand the biological potential of new agents that targeted bromodomains. The original examples, inhibitors of the bromodomain and extra-terminal (BET) class of bromodomains, showed enticing anti-inflammatory and anticancer activities, and several compounds have since advanced to human clinical trials. Here, we review the current state of BET inhibitor biology in relation to clinical development, and we discuss the next wave of bromodomain inhibitors with clinical potential in oncology and non-oncology indications. The lessons learned from BET inhibitor programmes should affect efforts to develop drugs that target non-BET bromodomains and other epigenetic readers.

VDAC1 is regulated by BRD4 and contributes to JQ1 resistance in breast cancer

Voltage-dependent anion channels (VDACs) are situated in the outer membrane of the mitochondria and serve as gatekeepers that control metabolite and ion exchange between the cytosol and mitochondria. VDAC1 is one of the most studied members of the VDAC protein family and is overexpressed in multiple types of cancer. However, the specific biological function and regulatory mechanism of VDAC1 in breast cancer remains unclear. The present study investigated the biological role of VDAC1 in breast cancer cells using an MTS assay. The association of clinicopathological features with VDAC1 in breast cancer was analyzed by Gene Expression Profiling Interactive Analysis. The regulatory mechanism of VDAC1 was determined by cell transfection, western blot analysis, reverse transcription-quantitative (q)PCR analysis, chromatin immunoprecipitation (ChIP) and ChIP-qPCR analysis. The results of the present study demonstrated that VDAC1 promoted breast cancer proliferation and was associated with a poor prognosis in patients with breast cancer. Additionally, it was observed that the expression of VDAC1 could be decreased by the bromodomain inhibitor (JQ1), and bromodomain-containing protein 4 (BRD4) was indicated to be a regulator of VDAC1. Furthermore, results suggested that VDAC1 may be involved in the resistance of breast cancer to JQ1. Collectively, the present findings uncovered important aspects of the function of VDAC1 in the tumor progression of breast cancer, and may provide a basis for potential therapeutic strategies for the treatment of breast cancer.

Correction: USP17 mediates macrophage-promoted inflammation and stemness in lung cancer cells by regulating TRAF2/TRAF3 complex formation

A correction to this paper has been published and can be accessed via a link at the top of the paper.

BRD4 promotes the stemness of gastric cancer cells via attenuating miR-216a-3p-mediated inhibition of Wnt/β-catenin signaling

The bromodomain and extra-terminal domain (BET) protein BRD4 is emerging as a potential target for cancer therapy. However, BRD4 roles in regulating the stemness of gastric cancer cells are unclear. Here, we demonstrated that BRD4 expression was significantly increased in gastric cancer tissues, cell spheroids, and BRD4 knockdown attenuated the stemness of gastric cancer cells characterized as the decrease of stemness markers expression, capacity of cells spheroids formation and ALDH1 activity. Importantly, BRD4 expression was negatively correlated with overall survival, first progression survival and post progression survival of gastric cancer patients. Mechanistic investigations revealed that miR-216a-3p was the most remarkably upregulated miRNA in response to BRD4 knockdown and Wnt/β-catenin signaling was necessary for BRD4-mediated promotion on the stemness of gastric cancer cells. Additionally, BRD4 directly bound to the promoter and promoted the methylation level of MIR216A promoter, thus decreasing miR-216a-3p level. Notably, Wnt3a was identified as the direct target of miR-216a-3p in gastric cancer cells. Therefore, our results defined a BRD4/miR-216a-3p/Wnt/β-catenin pathway in regulating the stemness of gastric cancer cells.

HDAC3 modulates cancer immunity via increasing PD-L1 expression in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the second leading cause of cancer-related deaths worldwide. Despite immune checkpoints based immunotherapy highlights a new therapeutic strategy and achieves a remarkable therapeutic effect in various types of malignant tumors. Pancreatic cancer is one of the non-immunogenic cancers and is resistant to immunotherapy. Programmed death ligand 1 (PD-L1) is expressed on the surface of tumor cells and its level is a key determinant of the checkpoint immunotherapy efficacy. Here, we reported that the specific inhibitor of histone deacetylase 3 (HDAC3) decreased the protein and mRNA level of PD-L1 in pancreatic cancer cells. Furthermore, we showed that HDAC3 was critical for PD-L1 regulation and positively correlated with PD-L1 in PDAC patient specimens. Finally, we demonstrated that HDAC3/signal transducer and activator of transcription 3 (STAT3) pathway transcriptionally regulated PD-L1 expression. Collectively, our data contributes to a better understanding of the function of HDAC3 in cancer immunity and the regulatory mechanism of PD-L1. More importantly, these data suggest that the HDAC3 inhibitors might be used to improve immunotherapy in pancreatic cancer.

Therapeutic Targeting of BRD4 in Head Neck Squamous Cell Carcinoma

The bromodomain and extraterminal family members are epigenetic readers and transcriptional coactivators which are critically involved in various biological processes including tumorigenesis. BRD4 has been increasingly appreciated as a key oncogene and promising anticancer target. Here, we sought to characterize the expression of BRD4 and its tumorigenic roles as well as therapeutic targeting in HNSCC.

Methods: Expression of BRD4 mRNA and protein was determined by bioinformatics interrogation of publically available databases, primary HNSCC samples and 4NQO-induced HNSCC animal model. The tumorigenic roles of BRD4 in HNSCC were evaluated by genetic and pharmacological approach in vitro and in vivo. Therapeutic efficiency of BRD4 targeting by JQ1 was assessed in three preclinical models including xenograft model, 4NQO-induced model and patients-derived xenograft model. Gene candidates responsible for therapeutic effects of JQ1 were identified by transcriptional profiling in HNSCC cells after JQ1 exposure.

Results: Significant upregulation of BRD4 was found in primary HNSCC samples and 4NQO-induced HNSCC model. Its overexpression associated with aggressive clinicopathological features and inferior overall and disease-free survival. BRD4 depletion by genetic silencing or pharmacological inhibition impaired cell proliferation, migration and invasion and reduced tumor growth and metastasis in vivo. Transcriptional profiling of HNSCC cells following JQ1 exposure identified hundreds of genes which might mediated its antitumor effects and enriched in cancer-relevant pathways. A novel prognostic risk score derived from JQ1-regulated genes was developed to stratify patients into subgroups with favorable or inferior prognosis.

Conclusions: Our findings reveal that BRD4 serves as a novel and critical mediator underlying tumorigenesis and a robust prognostic biomarker in HNSCC. Therapeutic targeting of BRD4 represents a potent and promising strategy against HNSCC.

MGMT-activated DUB3 stabilizes MCL1 and drives chemoresistance in ovarian cancer

Chemoresistance is a severe outcome among patients with ovarian cancer that leads to a poor prognosis. MCL1 is an antiapoptotic member of the BCL-2 family that has been found to play an essential role in advancing chemoresistance and could be a promising target for the treatment of ovarian cancer. Here, we found that deubiquitinating enzyme 3 (DUB3) interacts with and deubiquitinates MCL1 in the cytoplasm of ovarian cancer cells, which protects MCL1 from degradation. Furthermore, we identified that O⁶-methylguanine-DNA methyltransferase (MGMT) is a key activator of DUB3 transcription, and that the MGMT inhibitor PaTrin-2 effectively suppresses ovarian cancer cells with elevated MGMT-DUB3-MCL1 expression both in vitro and in vivo. Most interestingly, we found that histone deacetylase inhibitors (HDACis) could significantly activate MGMT/DUB3 expression; the combined administration of HDACis and PaTrin-2 led to the ideal therapeutic effect. Altogether, our results revealed the essential role of the MGMT-DUB3-MCL1 axis in the chemoresistance of ovarian cancer and identified that a combined treatment with HDACis and PaTrin-2 is an effective method for overcoming chemoresistance in ovarian cancer.

Overexpressed histone acetyltransferase 1 regulates cancer immunity by increasing programmed death-ligand 1 expression in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma is one of the leading causes of cancer-related death worldwide. Immune checkpoint blockade therapy, including anti-PD-1 and anti-PD-L1, is a new therapeutic strategy for cancer treatment but the monotherapy with PD-L1 inhibitors for pancreatic cancer is almost ineffective for pancreatic cancer. Thus, exploring the regulatory mechanism of PD-L1 in cancer cells, especially in pancreatic cancer cells, is one of the key strategies to improving cancer patient response to PD-L1 blockade therapy. Histone acetyltransferase 1(HAT1) is a classic type B histone acetyltransferase and the biological role of HAT1 in pancreatic cancer is unclear.

METHODS

The clinical relevance of HAT1 was examined by the GEPIA web tool, Western blotting and immunohistochemistry of pancreatic cancer tissue microarray slides. Tumor cell motility was investigated by MTS assay, colony formation assay and xenografts. The relationship between HAT1 and PD-L1 was examined by Western blot analysis, RT-qPCR and immunohistochemistry.

RESULTS

HAT1 was upregulated in PDAC and associated with poor prognosis in PDAC patients. The knockdown of HAT1 decreased the proliferation of pancreatic cancer cells in vivo and in vitro. Strikingly, we showed that HAT1 transcriptionally regulated PD-L1, and this process was mainly mediated by BRD4 in pancreatic cancer. The knockdown of HAT1 improved the efficacy of immune checkpoint blockade by decreasing the PD-L1.

CONCLUSIONS

The recognition of HAT1 in regulating tumor cell proliferation and cancer immunity indicated that HAT1 might be employed as a new diagnostic and prognostic marker and a predictive marker for pancreatic cancer therapy, especially in immune checkpoint blockade therapy. Targeting HAT1 highlights a novel therapeutic approach to overcome immune evasion by tumor cells.

B7-H3 is regulated by BRD4 and promotes TLR4 expression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies worldwide. PDAC is resistant to chemotherapy and radiotherapy which leads to the poor prognosis of PDAC patients and a 5-year survival rate of less than 5%. Exploring the mechanism of the pancreatic cancer tumorigenesis is the key to finding a novel therapeutic strategy for cancer treatment. B7-H3 belongs to the B7 family of immunoregulatory proteins, and the overexpression of B7-H3 is found in various types of cancer. The regulation of B7-H3 expression in pancreatic cancer is still unclear. Here, we showed that B7-H3 acted as a negative prognostic biomarker in PDAC and promoted cell proliferation, invasion and metastasis in pancreatic cancer. Next, we applied the drug screening method to identify bromodomain and extra-terminal motif (BET) inhibitors that decreased the protein and mRNA levels of B7-H3 in pancreatic cancer cells. Moreover, we verified that BRD4 was responsible for regulating the expression of B7-H3 at the transcriptional level. Finally, our data indicated that the BRD4/B7-H3 axis modulated the expression of TLR4 in pancreatic cancer cells. Taken together, our results elucidated the regulation of B7-H3 expression in pancreatic cancer and uncovered the importance of BRD4/B7-H3/TLR4 pathway. The targeting of B7-H3 by the BET inhibitors may be a novel therapeutic strategy to overcome the immunotherapy and chemotherapy resistance in pancreatic cancer.

FBP1 loss contributes to BET inhibitors resistance by undermining c-Myc expression in pancreatic ductal adenocarcinoma

Background

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal tumor types worldwide. BET inhibitors display anti-tumor activity in pancreatic cancer, however the cells often develop resistance after a long-term treatment and the underlying molecular basis is not fully understood.

Methods

Drug screening assay in Fructose-1, 6-biphosphatase (FBP1) knockdown or overexpressing pancreatic cancer cells was performed. Tumor cell motility, FBP1 protein and mRNA changes were investigated after BET inhibitors treatment. The interaction between TRIM28 and FBP1 after BET inhibitors treatment was examined by Co-immunoprecipitation (IP) and GST pull-down. The relationship between FBP1 and c-Myc was examined by western blot, RT-qPCR and immunohistochemistry (IHC).

Results

The expression of FBP1 protein increased the sensitivity of pancreatic cancer cells to JQ1. Furthermore, we showed that JQ1 stabilized FBP1 protein level by disrupting the interaction between FBP1 and TRIM28 in pancreatic cancer cells. Moreover, we demonstrated that FBP1 promoted c-Myc degradation through disrupting the ERK-c-Myc axis.

Conclusions

FBP1 modulates the sensitivity of pancreatic cancer cells to BET inhibitors by decreasing the expression of c-Myc. These findings highlight FBP1 could be used as a therapeutic niche for patient-tailored therapies.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0888-y) contains supplementary material, which is available to authorized users.

PES1 is transcriptionally regulated by BRD4 and promotes cell proliferation and glycolysis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. However, the mechanism underlying the tumorigenesis of HCC is still unclear. Improper recruitment of Pescadillo homologue 1 (PES1) can lead to tumorigenesis in multiple cancer types, such as gastric cancer and colon cancer. Here, we reported that PES1 was upregulated and associated with a poor prognosis in HCC specimens. Next, we found that PES1 promoted the growth of HCC in vivo and in vitro. Furthermore, we showed that the knockdown of PES1 decreased glycolysis via altering the gene expression of GLUT1, PKM2, ENO1, FBP1, and PCK1, which are related to glucose metabolism in HCC cells. Moreover, we demonstrated that PES1 is regulated by bromodomain-containing protein 4 (BRD4) and is partially responsible for modulating the antitumor effect of BET inhibitors in HCC. Taken together, our results suggest that PES1 plays an important role in promoting the proliferation of human liver cancer cells, suggesting that PES1 may be an ideal molecular target for HCC therapy.

Ubiquitin Regulation: The Histone Modifying Enzyme's Story

Histone post-translational modifications influence many fundamental cellular events by regulating chromatin structure and gene transcriptional activity. These modifications are highly dynamic and tightly controlled, with many enzymes devoted to the addition and removal of these modifications. Interestingly, these modifying enzymes are themselves fine-tuned and precisely regulated at the level of protein turnover by ubiquitin-proteasomal processing. Here, we focus on recent progress centered on the mechanisms regulating ubiquitination of histone modifying enzymes, including ubiquitin proteasomal degradation and the reverse process of deubiquitination. We will also discuss the potential pathophysiological significance of these processes.