BRD4 promotes pancreatic ductal adenocarcinoma cell proliferation and enhances gemcitabine resistance

Leveraging epigenetic alterations in pancreatic ductal adenocarcinoma for clinical applications

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy characterized by late detection and poor prognosis. Recent research highlights the pivotal role of epigenetic alterations in driving PDAC development and progression. These changes, in conjunction with genetic mutations, contribute to the intricate molecular landscape of the disease. Specific modifications in DNA methylation, histone marks, and non-coding RNAs are emerging as robust predictors of disease progression and patient survival, offering the potential for more precise prognostic tools compared to conventional clinical staging. Moreover, the detection of epigenetic alterations in blood and other non-invasive samples holds promise for earlier diagnosis and improved management of PDAC. This review comprehensively summarises current epigenetic research in PDAC and identifies persisting challenges. These include the complex nature of epigenetic profiles, tumour heterogeneity, limited access to early-stage samples, and the need for highly sensitive liquid biopsy technologies. Addressing these challenges requires the standardisation of methodologies, integration of multi-omics data, and leveraging advanced computational tools such as machine learning and artificial intelligence. While resource-intensive, these efforts are essential for unravelling the functional consequences of epigenetic changes and translating this knowledge into clinical applications. By overcoming these hurdles, epigenetic research has the potential to revolutionise the management of PDAC and improve patient outcomes.

Recent advances in drug delivery and targeting for the treatment of pancreatic cancer

Despite significant treatment efforts, pancreatic ductal adenocarcinoma (PDAC), the deadliest solid tumor, is still incurable in the preclinical stages due to multifacet stroma, dense desmoplasia, and immune regression. Additionally, tumor heterogeneity and metabolic changes are linked to low grade clinical translational outcomes, which has prompted the investigation of the mechanisms underlying chemoresistance and the creation of effective treatment approaches by selectively targeting genetic pathways. Since targeting upstream molecules in first-line oncogenic signaling pathways typically has little clinical impact, downstream signaling pathways have instead been targeted in both preclinical and clinical studies. In this review, we discuss how the complexity of various tumor microenvironment (TME) components and the oncogenic signaling pathways that they are connected to actively contribute to the development and spread of PDAC, as well as the ways that recent therapeutic approaches have been targeted to restore it. We also illustrate how many endogenous stimuli-responsive linker-based nanocarriers have recently been developed for the specific targeting of distinct oncogenes and their downstream signaling cascades as well as their ongoing clinical trials. We also discuss the present challenges, prospects, and difficulties in the development of first-line oncogene-targeting medicines for the treatment of pancreatic cancer patients.

Role of the long non-coding RNAs in regulation of Gemcitabine response in tumor cells

Chemotherapy is widely used as one of the first line therapeutic methods in cancer patients. However, chemotherapeutic resistance is one of the most common problems in cancer patients, which leads to the therapeutic failure and tumor relapse. Considering the side effects of chemotherapy drugs in normal tissues, it is required to investigate the molecular mechanisms involved in drug resistance to improve the therapeutic strategies in cancer patients. Long non-coding RNAs (lncRNAs) have pivotal roles in regulation of cellular processes associated with drug resistance. LncRNAs deregulations have been frequently reported in a wide range of chemo-resistant tumors. Gemcitabine (GEM) as a nucleoside analog has a wide therapeutic application in different cancers. However, GEM resistance is considered as a therapeutic challenge. Considering the role of lncRNAs in the occurrence of GEM resistance, in the present review we discussed the molecular mechanisms of lncRNAs in regulation of GEM response among cancer patients. It has been reported that lncRNAs have mainly an oncogenic role as the inducers of GEM resistance through direct or indirect regulation of transcription factors, autophagy, polycomb complex, and signaling pathways such as PI3K/AKT, MAPK, WNT, JAK/STAT, and TGF-β. This review paves the way to present the lncRNAs as non-invasive markers to predict GEM response in cancer patients. Therefore, lncRNAs can be introduced as the efficient markers to reduce the possible chemotherapeutic side effects in GEM resistant cancer patients and define a suitable therapeutic strategy among these patients.

Roles of lncRNAs in pancreatic ductal adenocarcinoma: Diagnosis, treatment, and the development of drug resistance

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers, primarily due to its late diagnosis, high propensity to metastasis, and the development of resistance to chemo-/radiotherapy. Accumulating evidence suggests that long non-coding RNAs (lncRNAs) are intimately involved in the treatment resistance of pancreatic cancer cells via interacting with critical signaling pathways and may serve as potential diagnostic/prognostic markers or therapeutic targets in PDAC.

DATA SOURCES

We carried out a systematic review on lncRNAs-based research in the context of pancreatic cancer and presented an overview of the updated information regarding the molecular mechanisms underlying lncRNAs-modulated pancreatic cancer progression and drug resistance, together with their potential value in diagnosis, prognosis, and treatment of PDAC. Literature mining was performed in PubMed with the following keywords: long non-coding RNA, pancreatic ductal adenocarcinoma, pancreatic cancer up to January 2022. Publications relevant to the roles of lncRNAs in diagnosis, prognosis, drug resistance, and therapy of PDAC were collected and systematically reviewed.

RESULTS

LncRNAs, such as HOTAIR, HOTTIP, and PVT1, play essential roles in regulating pancreatic cancer cell proliferation, invasion, migration, and drug resistance, thus may serve as potential diagnostic/prognostic markers or therapeutic targets in PDAC. They participate in tumorigenesis mainly by targeting miRNAs, interacting with signaling molecules, and involving in the epithelial-mesenchymal transition process.

CONCLUSIONS

The functional lncRNAs play essential roles in pancreatic cancer cell proliferation, invasion, migration, and drug resistance and have potential values in diagnosis, prognostic prediction, and treatment of PDAC.

The prognostic significance of bromodomain protein 4 expression in solid tumor patients: A meta-analysis

BACKGROUND

Cancer is a leading cause of death worldwide. At present, several inhibitors of bromodomain protein 4 have shown promising anti-tumor responses in clinical trials. Numerous studies have reported the value of bromodomain protein 4 expression in predicting the prognosis of patients with cancers, but their conclusions remain controversial. Therefore, we conducted a meta-analysis to explore the association between bromodomain protein 4 and patient prognosis with the aim to provide new directions for the development of strategies for targeted cancer therapy.

METHODS

The meta-analysis was registered in the International Prospective Register of Systematic Reviews (https://www.crd.york.ac.uk/prospero/; Registration No. CRD42020184948) and followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. PubMed Central, PubMed, Cochrane Library and Embase were thoroughly searched to identify eligible studies published through March 31, 2021. Odds ratios with 95% confidence intervals were calculated to demonstrate the relationship between bromodomain protein 4 expression and clinicopathological features. We computed pooled estimated hazard ratios with 95% confidence intervals using Stata 12.0 software to clarify the relationship between bromodomain protein 4 expression and overall survival of various cancers. A quality assessment of the eligible articles was performed based on the Newcastle-Ottawa scale.

RESULTS

A total of 974 patients from 10 studies were enrolled in the meta-analysis. Our results revealed that compared to low bromodomain protein 4 expression, high bromodomain protein 4 expression in cancer tissues was significantly associated with lymph node metastasis (Odds ratio = 3.59, 95% confidence interval: 2.62-4.91), distant metastasis (Odds ratio = 4.22, 95% confidence interval: 2.40-7.45), advanced TNM stage (III+IV vs. I+II: Odds ratio = 3.23, 95% confidence interval: 1.29-8.08), and poorly differentiated tumors (Odds ratio = 1.87, 95% confidence interval: 1.33-2.63). In addition, an elevated expression of bromodomain protein 4 tended to shorten survival time (Hazard ratio = 2.23, 95% confidence interval: 1.62-3.07). The subgroup analysis results showed that bromodomain protein 4 upregulation was related to poor prognosis in patients with digestive system cancers (Hazard ratio = 2.54, 95% confidence interval: 1.85-3.50).

CONCLUSION

This meta-analysis indicated that bromodomain protein 4 may serve as a promising prognostic biomarker for cancers and a direct effective cancer treatment target.

The Establishment of CDK9/ RNA PolII/H3K4me3/DNA Methylation Feedback Promotes HOTAIR Expression by RNA Elongation Enhancement in Cancer

Long non-coding RNA HOX Transcript Antisense RNA (HOTAIR) is overexpressed in multiple cancers with diverse genetic profiles. Importantly, since HOTAIR heavily contributes to cancer progression by promoting tumor growth and metastasis, HOTAIR becomes a potential target for cancer therapy. However, the underlying mechanism leading to HOTAIR deregulation is largely unexplored. Here, we performed a pan-cancer analysis using more than 4,200 samples and found that intragenic exon CpG island (Ex-CGI) was hypermethylated and was positively correlated to HOTAIR expression. Also, we revealed that Ex-CGI methylation promotes HOTAIR expression through enhancing the transcription elongation process. Furthermore, we linked up the aberrant intragenic tri-methylation on H3 at lysine 4 (H3K4me3) and Ex-CGI DNA methylation in promoting transcription elongation of HOTAIR. Targeting the oncogenic CDK7-CDK9-H3K4me3 axis downregulated HOTAIR expression and inhibited cell growth in many cancers. To our knowledge, this is the first time that a positive feedback loop that involved CDK9-mediated phosphorylation of RNA Polymerase II Serine 2 (RNA PolII Ser2), H3K4me3, and intragenic DNA methylation, which induced robust transcriptional elongation and heavily contributed to the upregulation of oncogenic lncRNA in cancer has been demonstrated. Targeting the oncogenic CDK7-CDK9-H3K4me3 axis could be a novel therapy in many cancers through inhibiting the HOTAIR expression.

Circular RNA circ-CCT3 promotes bortezomib resistance in multiple myeloma via modulating miR-223-3p/BRD4 axis

Multiple myeloma is a frequent hematologic malignancy. Bortezomib is the first-line drug for multiple myeloma chemotherapy. The present study aimed to investigate the potential role and mechanism of circular RNA chaperonin containing TCP1 subunit 3 (circ-CCT3) in bortezomib resistance of multiple myeloma. The levels of circ-CCT3, microRNA-223-3p (miR-223-3p), and bromodomain-containing 4 (BRD4) were detected by quantitative real-time PCR or western blot. Cell Counting Kit-8 (CCK-8) method was used to measure the half-inhibitory concentration of bortezomib and cell viability. Cell cycle distribution, apoptosis, proliferation and migration were determined by flow cytometry, 5-ethynyl-2'-deoxyuridine, and wound healing assay. The levels of relevant proteins were checked via western blot. The binding association between miR-223-3p and circ-CCT3/BRD4 was validated via a dual-luciferase reporter assay. Circ-CCT3 and BRD4 were upregulated, while miR-223-3p was downregulated in bortezomib-resistant multiple myeloma patients and cells. Silencing of circ-CCT3 enhanced the sensitivity of bortezomib-resistant multiple myeloma cells to bortezomib. Circ-CCT3 knockdown weakened bortezomib resistance via modulating miR-223-3p. Moreover, miR-223-3p increased bortezomib sensitivity by inhibiting BRD4. Downregulation of circ-CCT3 attenuated bortezomib resistance of multiple myeloma via regulating miR-223-3p/BRD4 pathway, which provided a new potential target for multiple myeloma chemoresistance.

circDENND4C Promotes Proliferation and Metastasis of Lung Cancer by Upregulating BRD4 Signaling Pathway

Objective

To investigate the effects of circDENND4C on the malignant biological behavior of lung cancer and its downstream target genes and molecular mechanisms.

Methods

The expression of circDENND4C in lung cancer tissues and cells was detected. After transfection with silenced circDENND4C, the expression levels of circDENND4C, miR-141-3p, and BRD4 in lung cancer cells were detected by qRT-PCR. The targeting relationship between circDENND4C and miR-141-3p as well as miR-141-3p and BRD4 was verified. Cell activity was detected by CCK-8 and EdU assay. Transwell assay was used to detect the invasiveness of A549 and NCI-H1299 in each group. Effects of circDENND4C on proliferation and metastasis of lung cancer in nude mice were studied.

Results

In vitro and in vivo results showed that circDENND4C silencing reduced the proliferation, invasion, and metastasis of lung cancer cells. Mechanism studies showed that circDENND4C has a targeting relationship with miR-141-3p. However, miR-141-3p has a targeting relationship with BRD4. circDENND4C indirectly upregulated BRD4 through sponge adsorption of miR-141-3p, thereby promoting metastasis and proliferation of NSCLC.

Conclusion

circDENND4C, as an oncogene, promotes the proliferation, invasion, and metastasis of lung cancer cells.

The Role of the Hedgehog Pathway in Chemoresistance of Gastrointestinal Cancers

The hedgehog pathway, which plays a significant role in embryonic development and stem cell regulation, is activated in gastrointestinal cancers. Chemotherapy is widely used in cancer treatment. However, chemoresistance becomes a substantial obstacle in cancer therapy. This review focuses on the recent advances in the hedgehog pathway's roles in drug resistance of gastrointestinal cancers and the novel drugs and strategies targeting hedgehog signaling.

NR5A2 transcriptional activation by BRD4 promotes pancreatic cancer progression by upregulating GDF15

NR5A2 is a transcription factor regulating the expression of various oncogenes. However, the role of NR5A2 and the specific regulatory mechanism of NR5A2 in pancreatic ductal adenocarcinoma (PDAC) are not thoroughly studied. In our study, Western blotting, real-time PCR, and immunohistochemistry were conducted to assess the expression levels of different molecules. Wound-healing, MTS, colony formation, and transwell assays were employed to evaluate the malignant potential of pancreatic cancer cells. We demonstrated that NR5A2 acted as a negative prognostic biomarker in PDAC. NR5A2 silencing inhibited the proliferation and migration abilities of pancreatic cancer cells in vitro and in vivo. While NR5A2 overexpression markedly promoted both events in vitro. We further identified that NR5A2 was transcriptionally upregulated by BRD4 in pancreatic cancer cells and this was confirmed by Chromatin immunoprecipitation (ChIP) and ChIP-qPCR. Besides, transcriptome RNA sequencing (RNA-Seq) was performed to explore the cancer-promoting effects of NR5A2, we found that GDF15 is a component of multiple down-regulated tumor-promoting gene sets after NR5A2 was silenced. Next, we showed that NR5A2 enhanced the malignancy of pancreatic cancer cells by inducing the transcription of GDF15. Collectively, our findings suggest that NR5A2 expression is induced by BRD4. In turn, NR5A2 activates the transcription of GDF15, promoting pancreatic cancer progression. Therefore, NR5A2 and GDF15 could be promising therapeutic targets in pancreatic cancer.

Targeted Therapies for Pancreatic Cancer: Overview of Current Treatments and New Opportunities for Personalized Oncology

Cytotoxic chemotherapy remains the only treatment option for most pancreatic ductal adenocarcinoma patients. Currently, the median overall survival of patients with advanced disease rarely exceeds 1 year. The complex network of pancreatic cancer composed of immune cells, endothelial cells, and cancer-associated fibroblasts confers intratumoral and intertumoral heterogeneity with distinct proliferative and metastatic propensity. This heterogeneity can explain why tumors do not behave uniformly and are able to escape therapy. The advance in technology of whole-genome sequencing has now provided the possibility of identifying every somatic mutation, copy-number change, and structural variant in a given cancer, giving rise to personalized targeted therapies. In this review, we provide an overview of the current and emerging treatment strategies in pancreatic cancer. By highlighting new paradigms in pancreatic ductal adenocarcinoma treatment, we hope to stimulate new thoughts for clinical trials aimed at improving patient outcomes.

Long noncoding RNA LINC00941 promotes pancreatic cancer progression by competitively binding miR-335-5p to regulate ROCK1-mediated LIMK1/Cofilin-1 signaling

An accumulation of evidence indicates that long noncoding RNAs are involved in the tumorigenesis and progression of pancreatic cancer (PC). In this study, we investigated the functions and molecular mechanism of action of LINC00941 in PC. Quantitative PCR was used to examine the expression of LINC00941 and miR-335-5p in PC tissues and cell lines, and to investigate the correlation between LINC00941 expression and clinicopathological features. Plasmid vectors or lentiviruses were used to manipulate the expression of LINC00941, miR-335-5p, and ROCK1 in PC cell lines. Gain or loss-of-function assays and mechanistic assays were employed to verify the roles of LINC00941, miR-335-5p, and ROCK1 in PC cell growth and metastasis, both in vivo and in vitro. LINC00941 and ROCK1 were found to be highly expressed in PC, while miR-335-5p exhibited low expression. High LINC00941 expression was strongly associated with larger tumor size, lymph node metastasis, and poor prognosis. Functional experiments revealed that LINC00941 silencing significantly suppressed PC cell growth, metastasis and epithelial–mesenchymal transition. LINC00941 functioned as a molecular sponge for miR-335-5p, and a competitive endogenous RNA (ceRNA) for ROCK1, promoting ROCK1 upregulation, and LIMK1/Cofilin-1 pathway activation. Our observations lead us to conclude that LINC00941 functions as an oncogene in PC progression, behaving as a ceRNA for miR-335-5p binding. LINC00941 may therefore have potential utility as a diagnostic and treatment target in this disease.

BRD4 inhibition sensitizes renal cell carcinoma cells to the PI3K/mTOR dual inhibitor VS-5584

Activation of the PI3K/AKT/mTOR pathway promotes the progression of renal cell carcinoma (RCC). This study tested the anti-RCC cell activity of the PI3K/mTOR dual inhibitor, VS-5584. We show that VS-5584 inhibited PI3K/AKT/mTORC1/2 activation in established (786-O and A498 lines) and primary RCC cells, thereby suppressing cell survival, proliferation, migration and cell cycle progression. VS-5584 induced significant apoptosis in RCC cells. A daily single oral dose of VS-5584 (20 mg/kg) significantly inhibited 786-O tumor growth in vivo. VS-5584 treatment of 786-O tumor xenografts and RCC cells resulted in feedback upregulation of bromodomain-containing protein 4 (BRD4). Furthermore, BRD4 inhibition (by JQ1 and CPI203), knockdown or complete knockout potentiated VS-5584-induced RCC cell death and apoptosis. Conversely, forced overexpression of BRD4 attenuated the cytotoxicity of VS-5584 in 786-O cells. Collectively, VS-5584 potently inhibits RCC cell proliferation and survival. Its anti-tumor activity is further enhanced by the targeted inhibition of BRD4.

Inhibitory effect of microRNA-608 on lung cancer cell proliferation, migration, and invasion by targeting BRD4 through the JAK2/STAT3 pathway

Lung cancer is the leading cause of cancer-related mortality around the world. This malignancy has a 5-year survival rate of 21%, because most of the patients are diagnosed in the middle or late stage of the disease when local metastasis and tumor invasion have already progressed. Therefore, the investigation of the pathogenesis of lung cancer is an issue of crucial importance. MicroRNAs (miRNAs) seem to be involved in the evolution and development of lung cancer. MicroRNA-608 is likely to be downregulated in lung cancer tissues. Regarding this, the current study involved the determination of the fundamental mechanism of microRNA-608 in the development of lung cancer. Based on the results of quantitative reverse transcription polymerase chain reaction (RT-qPCR), the expression level of microRNA-608 was downregulated in 40 lung cancer tissues, compared to that in the adjacent normal tissues. The results of dual-luciferase reporter assay revealed that bromodomain-containing protein 4 (BRD4) was the direct target of microRNA-608. Accordingly, the lung cancer tissues had an elevated expression level of BRD4, in contrast to the adjacent normal tissues. The results of Cell Counting Kit 8 assay demonstrated that the high expression of microRNA-608 notably restrained lung cancer cell proliferation. The scratch wound and transwell assays showed that the upregulation of microRNA-608 suppressed the migration and invasion of lung cancer cells. Finally, the western blot assay showed that in the microRNA-608 mimics group, the expression levels of BRD4, p-JAK2, p-STATA3, CD44, and MMP9 were significantly decreased, compared with those in the negative control miRNA mimics group. Our results indicate that high expression of microRNA-608 inhibits the proliferation, migration, and invasion of lung cancer cells by targeting BRD4 via the JAK2/STAT3 pathway.

Nanoformulation of PROteolysis TArgeting Chimera targeting ‘undruggable’ c-Myc for the treatment of pancreatic cancer

Aim: To explore the anticancer activity of a novel BRD4 protein degrader ARV-825 (ARV) and its nanoformulation development (ARV-NP) for treatment of pancreatic cancer. Materials & methods: ARV-NP were prepared using nanoprecipitation method and characterized for their physicochemical properties and various anticancer cell culture assays. Results: ARV-NP (89.63 ± 16.39 nm) demonstrated good physical stability, negligible hemolysis and improved half-life of ARV. ARV-NP showed significant cytotoxicity, apoptosis and anticlonogenic effect in pancreatic cancer cells. Significant downregulation of target proteins BRD4, c-Myc, Bcl-2 and upregulation of apoptotic marker cleaved caspase-3 was observed. Most importantly, ARV-NP treatment significantly inhibited the cell viability of 3D tumor spheroids of pancreatic cancer. Conclusion: ARV-NP represents a novel therapeutic strategy for pancreatic cancer.

Targeting Super-Enhancers via Nanoparticle-Facilitated BRD4 and CDK7 Inhibitors Synergistically Suppresses Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignant cancer with complex genomic variations, and no targetable genomic lesions have been found yet. Super-enhancers (SEs) have been found to contribute to the continuous and robust oncogenic transcription. Here, histone H3 lysine 27 acetylation (H3K27ac) is profiled in PDAC cell lines to establish SE landscapes. Concurrently, it is also shown that PDAC is vulnerable to the perturbation of the SE complex using bromodomain-containing protein 4 (BRD4) inhibitor, JQ1, synergized with cyclin-dependent kinase 7 (CDK7) inhibitor, THZ1. Formulations of hydrophobic l-phenylalanine-poly (ester amide) nanoparticles (NPs) with high drug loading of JQ1 and THZ1 (J/T@8P4s) are further designed and developed. J/T@8P4s is assessed for size, encapsulation efficiency, morphology, drug release profiles, and drug uptake in vitro. Compared to conventional free drug formulation, the nanodelivery system dramatically reduces the hepatotoxicity while significantly enhancing the tumor inhibition effects and the bioavailability of incorporated JQ1 and THZ1 at equal doses in a Gemcitabine-resistant PDAC patient-derived xenograft (PDX) model. Overall, the present study demonstrates that the J/T@8P4s can be a promising therapeutic treatment against the PDAC via suppression of SE-associated oncogenic transcription, and provides a strategy utilizing NPs to assist the drug delivery targeting SEs.

Caveolin-2 is regulated by BRD4 and contributes to cell growth in pancreatic cancer

Background

The bromodomain and extra-terminal domain (BET) family of proteins, especially BRD4 play an important role in epigenetic regulation, and are essential for cell survival and also are promising anticancer targets. This study aims to analyze the effect of BRD4 on the cell growth and progression of pancreatic cancer and novel mechanisms involved.

Methods

Expression of BRD4 in pancreatic cancer and paired adjacent noncancerous tissues from 76 patients was analyzed by western blotting, immunohistochemistry, and real time PCR. Its correlation with the clinicopathological characteristics and prognosis of pancreatic cancer patients was analyzed. The effects of BRD4 on the cell proliferation were detected by colony formation assay and sulforhodamine B assay. Migration and invasion were determined by Transwell assays, and the effect of BRD4 on subcutaneous tumor formation was verified in nude mice. Cell cycle analysis was detected by flow cytometry. The potential downstream targets of BRD4 and related molecular mechanisms were clarified by RNA sequencing, chromatin immunoprecipitation and dual luciferase reporter assay.

Results

BRD4 was overexpressed in pancreatic cancer. Biological results showed that BRD4 functioned as tumor promoter, facilitated cell proliferation, migration and invasion in vitro and in vivo. Further, caveolin-2 was selected as the downstream gene of BRD4 by RNA sequencing. Caveolin-2 overexpression can partially reverse the decreased cell growth ability caused by BRD4 knockdown, but did not affect cell migration and invasion. Chromatin immunoprecipitation assay and dual luciferase reporter assay revealed BRD4 could bind to the promoter region of caveolin-2 and upregulate caveolin-2 expression. Clinical data further indicated a positive correlation between BRD4 and caveolin-2 expression. BRD4 (high)/caveolin-2 (high) correlated with shorter overall survival of patients with pancreatic cancer. Multivariate analysis revealed that both BRD4 and caveolin-2 were independent factors.

Conclusions

Our findings reveal the oncogenic effects of BRD4 in pancreatic cancer and elucidate a possible mechanism by which BRD4 and caveolin-2 act to enhance cell growth. Targeting the BRD4-caveolin-2 interaction by development of BET inhibitors will be a therapeutic strategy for pancreatic cancer.

Autophagy in Osteosarcoma

Osteosarcoma (OS) remains a difficult disease to treat. The standard chemotherapy regimen has not improved survival for the past three decades. Resistance to chemotherapy remains a challenge and constitutes a major concern to clinical investigators. Autophagy has been recognized as a survival mechanism implicated in resistance to chemotherapy. We previously demonstrated chemotherapy to induce autophagy in OS. However, whether induction of autophagy will lead to survival or death has been the focus of many laboratories. Autophagy is a very context-dependent process, and no specific biomarker has been identified to define whether the process will lead to survival or death. In the present chapter, we present some of the mechanisms involved in the process of autophagy and summarize some of the most recent work related to autophagy in OS and the challenges encountered with the use of old and new autophagy inhibitors.

The BET inhibitor JQ1 attenuates double-strand break repair and sensitizes models of pancreatic ductal adenocarcinoma to PARP inhibitors

BACKGROUND

DNA repair deficiency accumulates DNA damage and sensitizes tumor cells to PARP inhibitors (PARPi). Based on our observation that the BET inhibitor JQ1 increases levels of DNA damage, we evaluated the efficacy of JQ1 + the PARPi olaparib in preclinical models of pancreatic ductal adenocarcinoma (PDAC). We also addressed the mechanism by which JQ1 increased DNA damage.

METHODS

The effect of JQ1 + olaparib on in vivo tumor growth was assessed with patient-derived xenograft (PDX) models of PDAC. Changes in protein expression were detected by immunohistochemistry and immunoblot. In vitro growth inhibition and mechanistic studies were done using alamarBlue, qRT-PCR, immunoblot, immunofluorescence, ChIP, and shRNA knockdown assays.

FINDINGS

Tumors exposed in vivo to JQ1 had higher levels of the DNA damage marker γH2AX than tumors exposed to vehicle only. Increases in γH2AX was concomitant with decreased expression of DNA repair proteins Ku80 and RAD51. JQ1 + olaparib inhibited the growth of PDX tumors greater than either drug alone. Mechanistically, ChIP assays demonstrated that JQ1 decreased the association of BRD4 and BRD2 with promoter loci of Ku80 and RAD51, and shRNA data showed that expression of Ku80 and RAD51 was BRD4- and BRD2-dependent in PDAC cell lines.

INTERPRETATION

The data are consistent with the hypothesis that JQ1 confers a repair deficient phenotype and the consequent accumulation of DNA damage sensitizes PDAC cells to PARPi. Combinations of BET inhibitors with PARPi may provide a novel strategy for treating PDAC. FUND: NIH grants R01CA208272 and R21CA205501; UAB CMB T32 predoctoral training grant.

Long non-coding RNA LINC00346 promotes pancreatic cancer growth and gemcitabine resistance by sponging miR-188-3p to derepress BRD4 expression

BACKGROUND

Long non-coding RNA LINC00346 has been recently suggested as a prognostic marker in pancreatic cancer. However, its biological function in pancreatic cancer has not yet been determined. In this study, we attempted to ascertain the role of LINC00346 in regulating the aggressiveness of pancreatic cancer.

METHODS

The effects of overexpression and knockdown of LINC00346 on the proliferation, cell cycle progression, apoptosis, and gemcitabine resistance were investigated. Bioinformatic analysis, luciferase reporter assay, and RNA immunoprecipitation assay were performed to search for potential microRNAs (miRs) that can interact with LINC00346.

RESULTS

Overexpression of LINC00346 significantly enhanced the proliferation, colony formation, and tumorigenesis of pancreatic cancer cells. Conversely, knockdown of LINC00346 suppressed pancreatic cancer cell proliferation and caused a cell-cycle arrest at the G2/M-phase. Depletion of LINC00346 also enhanced gemcitabine sensitivity in pancreatic cancer cells both in vitro and in vivo. Mechanistic investigation revealed that LINC00346 acted as a sponge for miR-188-3p and blocked the repression of BRD4 by miR-188-3p in pancreatic cancer cells. Clinical evidence indicated a negative correlation between LINC00346 and miR-188-3p in pancreatic cancer specimens. Rescue experiments showed that LINC00346 attenuated the growth-suppressing and chemosensitizing effects of miR-188-3p on pancreatic cancer cells. In addition, silencing of BRD4 significantly inhibited LINC00346-induced pancreatic cancer cell proliferation and colony formation.

CONCLUSIONS

LINC00346 shows the ability to promote pancreatic cancer growth and gemcitabine resistance, which is in part mediated by antagonization of miR-188-3p and induction of BRD4. Targeting LINC00346 may improve gemcitabine-based therapeutic efficacy.

Bromodomain‑containing protein 4 is critical for the antiproliferative and pro‑apoptotic effects of gambogic acid in anaplastic thyroid cancer

Gambogic acid (GA) has been widely used as an anticancer drug for different tumors, including thyroid cancer. However, the potential function and molecular mechanisms of GA in anaplastic thyroid cancer (ATC) has not been illustrated thus far. The aim of the present study was to demonstrate the antitumor effects of GA on ATC cells and investigate its underlying molecular mechanisms. The results revealed that GA significantly decreased the viability and proliferation, as well as induced cell apoptosis in ATC cell lines. Next, it was demonstrated that GA decreased the expression of bromodomain‑containing protein 4 (BRD4), which has been reported to function as an oncogene in various types of cancer. BRD4 expression was significantly higher in ATC tissues compared with that in adjacent normal thyroid tissues. In addition, BRD4 silencing significantly repressed the cell viability and proliferation, and increased the cell apoptotic rate in vitro, while it also delayed the tumor growth in vivo. Notably, ectopic BRD4 expression significantly weakened the biological effects of GA on ATC cells in vitro and in vivo, which suggested that GA served its anticancer functions partially via downregulating BRD4. In conclusion, BRD4, functioning as an oncogene in ATC, is important for the antiproliferative and pro‑apoptotic effects of GA.

LARP7 in papillary thyroid carcinoma induces NIS expression through suppression of the SHH signaling pathway

The incidence of thyroid cancer has increased the past few decades, the most frequent type has been identified to be the papillary thyroid carcinoma (PTC). Following thyroidectomy, radioiodine ablation treatment on PTC is routinely performed. However, many patients do not benefit from radioiodine therapy. Therefore, novel targeted therapies to suppress tumor growth and improve radioiodine uptake are required. La ribonucleoprotein domain family member (LARP)7 is a member of the LARP family and functions as a potential suppressor of the progression of carcinoma. In the present study, the expression status of LARP7 in PTC tissues and cell lines was investigated, and the cell viability, proliferation and apoptotic rate, radioiodine uptake ability of PTC cells with overexpression of LARP7 in vitro was determined. Expression levels of LARP7 were significantly downregulated in PTC tissues and cell lines. Overexpression of LARP7 inhibited the proliferation and increased the radioiodine uptake ability of PTC cells in vitro and inhibited the tumor growth in vivo. Furthermore, LARP7 overexpression inhibited the sonic hedgehog (SHH) signaling pathway and increased sodium/iodide symporter (NIS) expression. However, treatment with recombinant human SHH partially reduced radioiodine uptake ability and NIS expression induced by LARP7. In conclusion, LARP7 may act as a tumor suppressor in PTC by inhibiting the SHH signaling pathway and may be a promising therapeutic target in patients with PTC.

miR-3140 suppresses tumor cell growth by targeting BRD4 via its coding sequence and downregulates the BRD4-NUT fusion oncoprotein

Bromodomain Containing 4 (BRD4) mediates transcriptional elongation of the oncogene MYC by binding to acetylated histones. BRD4 has been shown to play a critical role in tumorigenesis in several cancers, and the BRD4-NUT fusion gene is a driver of NUT midline carcinoma (NMC), a rare but highly lethal cancer. microRNAs (miRNAs) are endogenous small non-coding RNAs that suppress target gene expression by binding to complementary mRNA sequences. Here, we show that miR-3140, which was identified as a novel tumor suppressive miRNA by function-based screening of a library containing 1090 miRNA mimics, directly suppressed BRD4 by binding to its coding sequence (CDS). miR-3140 concurrently downregulated BRD3 by bind to its CDS as well as CDK2 and EGFR by binding to their 3' untranslated regions. miR-3140 inhibited tumor cell growth in vitro in various cancer cell lines, including EGFR tyrosine kinase inhibitor-resistant cells. Interestingly, we found that miR-3140 downregulated the BRD4-NUT fusion protein and suppressed in vitro tumor cell growth in a NMC cell line, Ty-82 cells. Furthermore, administration of miR-3140 suppressed in vivo tumor growth in a xenograft mouse model. Our results suggest that miR-3140 is a candidate for the development of miRNA-based cancer therapeutics.

Pharmacoepigenetics and pharmacoepigenomics of gastrointestinal cancers

Our understanding of the epigenetic changes occurring in gastrointestinal cancers has gained tremendous advancements in recent years, and some epigenetic biomarkers are already translated into the clinics for cancer diagnostics. In parallel, pharmacoepigenetics and pharmacoepigenomics of solid tumors are relevant novel, but emerging and promising fields. Areas covered: A comprehensive review of the literature to summarize and update the emerging field of pharmacoepigenetics and pharmacoepigenomics of gastrointestinal cancers. Expert commentary: Several epigenetic modifications have been proposed to account for interindividual variations in drug response in gastrointestinal cancers. Similarly, single-agent or combined strategies with high doses of drugs that target epigenetic modifications (epi-drugs) were scarcely tolerated by the patients, and current research has moved to their combination with standard therapies to achieve chemosensitization, radiosensitization, and immune modulation of cancerous cells. In parallel, recent genome-wide technologies are revealing the pathways that are epigenetically deregulated during cancer-acquired resistance, including those targeted by non-coding RNAs. Indeed, novel, less toxic, and more specific molecules are under investigation to specifically target those pathways. The field is rapidly expanding and gathering together information coming from these investigations has the potential to lead to clinical applications in the coming new years.

Hsa-miR-599 suppresses the migration and invasion by targeting BRD4 in breast cancer

Breast cancer is the second leading cause of cancer-associated mortality in females in the USA. Hsa-miR-599 was demonstrated to function as a tumour suppressor during cancer progression. However, the function and mechanism of the hsa-miR-599 in human breast cancer remain elusive. Thus, the aim of the present study was to investigate the potential role of hsa-miR-599 in breast cancer biology. The expression levels of hsa-miR-599 in 40 pairs of surgical specimens and human breast cancer cell lines were detected using quantitative polymerase chain reaction analysis. The overexpression of hsa-miR-599 was established by transfecting mimics into the MCF-7 and MDA-MB-231 cell lines. Cell counting kit-8, colony formation and transwell assays were used to investigate the potential function of hsa-miR-599 in MCF-7 and MDA-MB-231 cell lines. Luciferase assays combined with western blot analysis was performed to validate the regulation of a putative target of hsa-miR-599. The results demonstrated that hsa-miR-599 was downregulated in the breast cancer tissues and breast cancer cell lines. Overexpression of hsa-miR-599 was revealed to inhibit the viability and proliferation of cell in vitro and tumour growth in vivo. The results of the luciferase assay indicate that bromodomain containing 4 (BRD4) is a direct target of hsa-miR-599. Furthermore, the xenograft mouse model demonstrated that overexpressed hsa-miR-599 reduced BRD4 expression. These results suggest that hsa-miR-599 serves as an oncosuppressive microRNA that impairs breast cancer tumorigenesis and progression by directly targeting BRD4. Furthermore, increased BRD4 expression partially reversed the suppressive effect of hsa-miR-599. In conclusion, the results of the present study demonstrated that hsa-miR-599 suppressed breast cancer progression by downregulating BRD4. The overexpression of hsa-miR-599 may be considered as a novel therapeutic target for the treatment of patients with breast cancer.

Hedgehog Signaling in Pancreatic Fibrosis and Cancer

The hedgehog signaling pathway was first discovered in the 1980s. It is a stem cell-related pathway that plays a crucial role in embryonic development, tissue regeneration, and organogenesis. Aberrant activation of hedgehog signaling leads to pathological consequences, including a variety of human tumors such as pancreatic cancer. Multiple lines of evidence indicate that blockade of this pathway with several small-molecule inhibitors can inhibit the development of pancreatic neoplasm. In addition, activated hedgehog signaling has been reported to be involved in fibrogenesis in many tissues, including the pancreas. Therefore, new therapeutic targets based on hedgehog signaling have attracted a great deal of attention to alleviate pancreatic diseases. In this review, we briefly discuss the recent advances in hedgehog signaling in pancreatic fibrogenesis and carcinogenesis and highlight new insights on their potential relationship with respect to the development of novel targeted therapies.

Downregulation of miR-329 promotes cell invasion by regulating BRD4 and predicts poor prognosis in hepatocellular carcinoma

Increasing evidence indicates that abnormal microRNA (miRNA) expression is related to hepatocellular carcinoma (HCC) development. Our study aimed to elucidate the essential role of miR-329 in HCC progression. Real-time PCR was used to analyze miR-329 and bromodomain containing 4 (BRD4) expression in HCC samples (n = 135). Cell Counting Kit-8 (CCK-8) and flow cytometric analysis were used to investigate cell proliferation and apoptosis. The transwell assay was used to examine the cell invasive ability. The regulation mechanism was confirmed by luciferase reporter and western blot assays. Kaplan-Meier analysis was used to detect the function of miR-329 on the prognosis of HCC patients. miR-329 was decreased in HCC samples and was related to tumor development. Furthermore, miR-329 significantly regulated cell invasion by targeting BRD4 but had no effect on cell proliferation and apoptosis. Moreover, downregulation of miR-329 predicted poor prognosis of HCC patients. miR-329 could control cell invasion via regulating BRD4 expression and may be a prognostic marker in HCC.