Control of tumorigenesis and chemoresistance by the DEK oncogene

DEK regulates B-cell proliferative capacity and is associated with aggressive disease in low-grade B-cell lymphomas

This study sheds light on the pivotal role of the oncoprotein DEK in B-cell lymphoma. We reveal DEK expression correlates with increased tumor proliferation and inferior overall survival in cases diagnosed with low-grade B-cell lymphoma (LGBCL). We also found significant correlation between DEK expression and copy number alterations in LGBCL tumors, highlighting a novel mechanism of LGBCL pathogenesis that warrants additional exploration. To interrogate the mechanistic role of DEK in B-cell lymphoma, we generated a DEK knockout cell line model, which demonstrated DEK depletion caused reduced proliferation and altered expression of key cell cycle and apoptosis-related proteins, including Bcl-2, Bcl-xL, and p53. Notably, DEK depleted cells showed increased sensitivity to apoptosis-inducing agents, including venetoclax and staurosporine, which underscores the therapeutic potential of targeting DEK in B-cell lymphomas. Overall, our study contributes to a better understanding of DEK's role as an oncoprotein in B-cell lymphomas, highlighting its potential as both a promising therapeutic target and a novel biomarker for aggressive LGBCL. Further research elucidating the molecular mechanisms underlying DEK-mediated tumorigenesis could pave the way for improved treatment strategies and better clinical outcomes for patients with B-cell lymphoma.

The Antitumor Effect of the DNA Polymerase Alpha Inhibitor ST1926 in Glioblastoma: A Proteomics Approach

Glioblastoma Multiforme (GBM) is the most aggressive form of malignant brain tumor. The median survival rate does not exceed two years, indicating an imminent need to develop novel therapies. The atypical adamantyl retinoid ST1926 induces apoptosis and growth inhibition in different cancer types. We have shown that ST1926 is an inhibitor of the catalytic subunit of DNA polymerase alpha (POLA1), which is involved in initiating DNA synthesis in eukaryotic cells. POLA1 levels are elevated in GBM versus normal brain tissues. Therefore, we studied the antitumor effects of ST1926 in several human GBM cell lines. We further explored the global protein expression profiles in GBM cell lines using liquid chromatography coupled with tandem mass spectrometry to identify new targets of ST1926. Low sub-micromolar concentrations of ST1926 potently decreased cell viability, induced cell damage and apoptosis, and reduced POLA1 protein levels in GBM cells. The proteomics profiles revealed 197 proteins significantly differentially altered upon ST1926 treatment of GBM cells involved in various cellular processes. We explored the differential gene and protein expression of significantly altered proteins in GBM compared to normal brain tissues.

Role of DEK in carcinogenesis, diagnosis, prognosis, and therapeutic outcome of breast cancer: An evidence-based clinical review

Breast cancer is a significantly burdening women's cancer with limited diagnostic modalities. DEK is a novel biomarker overexpressed in breast cancers, currently exhaustively researched for its diagnosis and prognosis. Search for relevant meta-analyses, cohorts, and experimental studies in the last fifteen years was done in five large scientific databases. Non-English, non-full text articles or unrelated studies were excluded. Thirteen articles discussed the potential of DEK to estimate breast cancer characteristics, treatment outcomes, and prognosis. This proto-oncogene plays a role in breast carcinogenesis, increasing tumour proliferation and invasion, preventing apoptosis, and creating an immunodeficient tumour milieu with M2 tumour-associated macrophages. DEK is also associated with worse clinicopathological features and survival in breast cancer patients. Using a Kaplan-Meier plotter data analysis, DEK expression predicts worse overall survival (HR 1.24, 95%CI: 1.01-1.52, p = 0.039), comparable to other biomarkers. DEK is a promising novel biomarker requiring further research to determine its bedside applications.

From ecology to oncology: To understand cancer stem cell dormancy, ask a Brine shrimp (Artemia)

The brine shrimp (Artemia), releases embryos that can remain dormant for up to a decade. Molecular and cellular level controlling factors of dormancy in Artemia are now being recognized or applied as active controllers of dormancy (quiescence) in cancers. Most notably, the epigenetic regulation by SET domain-containing protein 4 (SETD4), is revealed as highly conserved and the primary control factor governing the maintenance of cellular dormancy from Artemia embryonic cells to cancer stem cells (CSCs). Conversely, DEK, has recently emerged as the primary factor in the control of dormancy exit/reactivation, in both cases. The latter has been now successfully applied to the reactivation of quiescent CSCs, negating their resistance to therapy and leading to their subsequent destruction in mouse models of breast cancer, without recurrence or metastasis potential. In this review, we introduce the many mechanisms of dormancy from Artemia ecology that have been translated into cancer biology, and herald Artemia's arrival on the model organism stage. We show how Artemia studies have unlocked the mechanisms of the maintenance and termination of cellular dormancy. We then discuss how the antagonistic balance of SETD4 and DEK fundamentally controls chromatin structure and consequently governs CSCs function, chemo/radiotherapy resistance, and dormancy in cancers. Many key stages from transcription factors to small RNAs, tRNA trafficking, molecular chaperones, ion channels, and links with various pathways and aspects of signaling are also noted, all of which link studies in Artemia to those of cancer on a molecular and/or cellular level. We particularly emphasize that the application of such emerging factors as SETD4 and DEK may open new and clear avenues for the treatment for various human cancers.

A DEK domain-containing protein GhDEK2D mediated Gossypium hirsutum enhanced resistance to Verticillium dahliae

DEK is associated with DNA replication and break repair, mRNA splicing, and transcriptional regulation, which had been studied in humans and mammals. The function of DEK in plants was poorly understood. In this study, GhDEK2D was identified in Gossypium hirsutum by genome-wide and post-translational modifications. GhDEK2D had been phosphorylated, acetylated and ubiquitylated under Verticillium dahliae (Vd) challenge. The GhDEK2D-silenced cotton decreased resistance against Vd. In GhDEK2D-silenced cotton plants, the reactive oxygen species was activated, the callose, xylogen, hypersensitive reaction (HR) and expression levels of defense-related genes were reduced. Homozygous overexpressing-GhDEK2D transgenic Arabidopsis lines were more resistant to Verticillium wilt (Vw). We propose that GhDEK2D was a potential molecular target for improving resistance to Vw in cotton.

Nuclear expression of AFF2 C-terminus is a sensitive and specific ancillary marker for DEK::AFF2 carcinoma of the sinonasal tract

DEK::AFF2 carcinoma of the sinonasal tract is an emerging entity. The tumor is typically characterized by papillary proliferation of non-keratinizing squamous epithelial cells with monotonous cytologic features, which may mimic other sinonasal tumors. The confirmation of this gene fusion has thus far relied solely on next-generation sequencing, fluorescence in situ hybridization (FISH), or reverse transcription polymerase chain reaction (RT-PCR). This current study aimed to validate an immunohistochemical assay for AFF2 C-terminus as an ancillary marker. We first analyzed publicly available RNA sequencing data of sinonasal tumors from the national center for biotechnology information (NCBI) sequence read archive and identified 3 DEK::AFF2 carcinomas out of 28 sinonasal tumors. The gene expression of AFF2 was significantly higher in the fusion-positive cases compared to the wild-type tumors (p < 0.001), while DEK was not. We then optimized an immunohistochemical assay with an anti-AFF2 C-terminus antibody for ancillary diagnosis. Seventeen DEK::AFF2 carcinomas, including 11 cases with predominantly low-grade morphology and one showing glandular differentiation, as well as 78 DEK FISH-negative sinonasal tumors were evaluated by AFF2 immunohistochemistry (IHC). Sixteen of the 17 DEK::AFF2 carcinomas showed nuclear AFF2 expression in ≥30% of tumor cells, including one decalcified case that failed FISH and RT-PCR confirmation. The one case that was negative for AFF2 IHC in the tumor cells also lacked expression in the internal positive control. It was thus considered a failure of the IHC rather than a truly negative case and was excluded from the statistical analysis. All DEK FISH-negative sinonasal tumors were negative for nuclear AFF2 expression. The nuclear expression of AFF2 IHC showed 100% sensitivity and specificity for DEK::AFF2 carcinoma. Accordingly, AFF2 IHC is a highly sensitive and specific ancillary marker that distinguishes DEK-AFF2 carcinoma from the other sinonasal tumors with overlapping morphological features and may be an especially useful alternative for decalcified specimens.

Novel molecular mechanisms in Alzheimer's disease: The potential role of DEK in disease pathogenesis

Alzheimer's disease and age-related dementias (AD/ADRD) are debilitating diseases that exact a significant physical, emotional, cognitive, and financial toll on the individual and their social network. While genetic risk factors for early-onset AD have been identified, the molecular and genetic drivers of late-onset AD, the most common subtype, remain a mystery. Current treatment options are limited for the 35 million people in the United States with AD/ADRD. Thus, it is critically important to identify novel molecular mechanisms of dementia-related pathology that may be targets for the development of new interventions. Here, we summarize the overarching concepts regarding AD/ADRD pathogenesis. Then, we highlight one potential molecular driver of AD/ADRD, the chromatin remodeling protein DEK. We discuss in vitro, in vivo, and ex vivo findings, from our group and others, that link DEK loss with the cellular, molecular, and behavioral signatures of AD/ADRD. These include associations between DEK loss and cellular and molecular hallmarks of AD/ADRD, including apoptosis, Tau expression, and Tau hyperphosphorylation. We also briefly discuss work that suggests sex-specific differences in the role of DEK in AD/ADRD pathogenesis. Finally, we discuss future directions for exploiting the DEK protein as a novel player and potential therapeutic target for the treatment of AD/ADRD.

Doxorubicin induces prolonged DNA damage signal in cells overexpressing DEK isoform-2

DEK has a short isoform (DEK isoform-2; DEK2) that lacks amino acid residues between 49–82. The full-length DEK (DEK isoform-1; DEK1) is ubiquitously expressed and plays a role in different cellular processes but whether DEK2 is involved in these processes remains elusive. We stably overexpressed DEK2 in human bone marrow stromal cell line HS-27A, in which endogenous DEKs were intact or suppressed via short hairpin RNA (sh-RNA). We have found that contrary to ectopic DEK1, DEK2 locates in the nucleus and nucleolus, causes persistent γH2AX signal upon doxorubicin treatment, and couldn’t functionally compensate for the loss of DEK1. In addition, DEK2 overexpressing cells were more sensitive to doxorubicin than DEK1-cells. Expressions of DEK1 and DEK2 in cell lines and primary tumors exhibit tissue specificity. DEK1 is upregulated in cancers of the colon, liver, and lung compared to normal tissues while both DEK1 and DEK2 are downregulated in subsets of kidney, prostate, and thyroid carcinomas. Interestingly, only DEK2 was downregulated in a subset of breast tumors suggesting that DEK2 can be modulated differently than DEK1 in specific cancers. In summary, our findings show distinct expression patterns and subcellular location and suggest non-overlapping functions between the two DEK isoforms.

Crowberry inhibits cell proliferation and migration through a molecular mechanism that includes inhibition of DEK and Akt signaling in cholangiocarcinoma

Background

Cholangiocarcinoma (CCA) is a rare biliary adenocarcinoma related to poor clinical prognosis. Crowberry is an herbal medicine used to control inflammatory diseases and reestablish antioxidant enzyme activity. Although crowberry shows significant therapeutic efficacy in various tumors and diseases, its anticancer effects and specific molecular mechanisms in CCA are poorly understood.

Aim of the study

This study was conducted to characterize crowberry effects on CCA cells behavior.

Materials and methods

The chemical profiles of crowberry extract was qualitatively analyzed by high-performance liquid chromatography (HPLC) and HPLC–tandem mass spectrometry. MTT, colony formation and EdU assays were performed to measure cell proliferation. The effect of crowberry treatment on CCA cell migration was assessed by wound healing and migration assays. Moreover, Hoechst staining assay and flow cytometry were performed to assess the cell apoptosis rate. Western blotting was used to assess the protein expression levels of key factors associated with apoptosis, the Akt signaling pathway, and the epithelial-mesenchymal transition. A xenograft model was established and immunohistochemical and H&E staining was performed to assess crowberry antitumor effects in vivo.

Results

Crowberry clearly inhibited CCA cells proliferation and migration in a dose-dependent manner and induced apoptosis in vitro. Crowberry inactivated the PI3K/Akt signaling pathway by regulating DEK in vitro and significantly inhibited tumor growth by downregulating the DEK expression in xenograft models.

Conclusion

Crowberry inhibits CCA cells proliferation and migration through a molecular mechanism that includes inhibition of DEK and Akt signaling pathway inhibition in vitro and in vivo.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-022-00623-6.

Crowberry alterd expression levels of key mediators in PI3K/Akt signaling pathway.

Crowberry alterd expression levels of key mediators in PI3K/Akt signaling pathway.

Crowberry suppressed the expression of the proto-oncogene DEK in vivo and in vitro.

Crowberry inhibited CCA progression and migration through a molecular mechanism that includes inhibition of DEK and the Akt signaling pathway in vivo and in vitro.

The m6A Methyltransferase METTL3-Mediated N6-Methyladenosine Modification of DEK mRNA to Promote Gastric Cancer Cell Growth and Metastasis

Gastric cancer (GC) is the fifth most common cancer and the third deadliest cancer in the world, and the occurrence and development of GC are influenced by epigenetics. Methyltransferase-like 3 (METTL3) is a prominent RNA n6-adenosine methyltransferase (m6A) that plays an important role in tumor growth by controlling the work of RNA. This study aimed to reveal the biological function and molecular mechanism of METTL3 in GC. The expression level of METTL3 in GC tissues and cells was detected by qPCR, Western blot and immunohistochemistry, and the expression level and prognosis of METTL3 were predicted in public databases. CCK-8, colony formation, transwell and wound healing assays were used to study the effect of METTL3 on GC cell proliferation and migration. In addition, the enrichment effect of METTL3 on DEK mRNA was detected by the RIP experiment, the m6A modification effect of METTL3 on DEK was verified by the MeRIP experiment and the mRNA half-life of DEK when METTL3 was overexpressed was detected. The dot blot assay detects m6A modification at the mRNA level. The effect of METTL3 on cell migration ability in vivo was examined by tail vein injection of luciferase-labeled cells. The experimental results showed that METTL3 was highly expressed in GC tissues and cells, and the high expression of METTL3 was associated with a poor prognosis. In addition, the m6A modification level of mRNA was higher in GC tissues and GC cell lines. Overexpression of METTL3 in MGC80-3 cells and AGS promoted cell proliferation and migration, while the knockdown of METTL3 inhibited cell proliferation and migration. The results of in vitro rescue experiments showed that the knockdown of DEK reversed the promoting effects of METTL3 on cell proliferation and migration. In vivo experiments showed that the knockdown of DEK reversed the increase in lung metastases caused by the overexpression of METTL3 in mice. Mechanistically, the results of the RIP experiment showed that METTL3 could enrich DEK mRNA, and the results of the MePIP and RNA half-life experiments indicated that METTL3 binds to the 3'UTR of DEK, participates in the m6A modification of DEK and promotes the stability of DEK mRNA. Ultimately, we concluded that METTL3 promotes GC cell proliferation and migration by stabilizing DEK mRNA expression. Therefore, METTL3 is a potential biomarker for GC prognosis and a therapeutic target.

Molecular Classification and Overcoming Therapy Resistance for Acute Myeloid Leukemia with Adverse Genetic Factors

The European LeukemiaNet (ELN) criteria define the adverse genetic factors of acute myeloid leukemia (AML). AML with adverse genetic factors uniformly shows resistance to standard chemotherapy and is associated with poor prognosis. Here, we focus on the biological background and real-world etiology of these adverse genetic factors and then describe a strategy to overcome the clinical disadvantages in terms of targeting pivotal molecular mechanisms. Different adverse genetic factors often rely on common pathways. KMT2A rearrangement, DEK-NUP214 fusion, and NPM1 mutation are associated with the upregulation of HOX genes. The dominant tyrosine kinase activity of the mutant FLT3 or BCR-ABL1 fusion proteins is transduced by the AKT-mTOR, MAPK-ERK, and STAT5 pathways. Concurrent mutations of ASXL1 and RUNX1 are associated with activated AKT. Both TP53 mutation and mis-expressed MECOM are related to impaired apoptosis. Clinical data suggest that adverse genetic factors can be found in at least one in eight AML patients and appear to accumulate in relapsed/refractory cases. TP53 mutation is associated with particularly poor prognosis. Molecular-targeted therapies focusing on specific genomic abnormalities, such as FLT3, KMT2A, and TP53, have been developed and have demonstrated promising results.

Gigantol inhibits cell proliferation and induces apoptosis by regulating DEK in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a common type of cancer, with a mortality of >80% worldwide. Gigantol is a bibenzyl compound that displays anticancer activity. The aim of the present study was to determine the biological activity of gigantol in NSCLC and to elucidate the underlying molecular mechanism of its action. The expression of DEK proto-oncogene (DEK) was measured in NSCLC tissues and cell lines by reverse transcription-quantitative PCR (RT-qPCR). The results suggested that DEK levels were significantly increased in NSCLC tissues and cell lines compared with adjacent non-tumor tissues and BEAS-2B normal bronchial epithelial cells, respectively. A549 cells were exposed to a series of gigantol concentrations (0, 25, 50 and 100 µM) and transfected with DEK small interfering RNA. The results of cell viability measured by MTT assay indicated that gigantol significantly decreased cell viability. Additionally, cell proliferation was assessed by CCK-8 and apoptosis was measured by flow cytometry. In comparison with the control group, gigantol treatment inhibited cell proliferation and promoted apoptosis, whereas DEK knockdown increased gigantol-induced suppression of proliferation and acceleration of apoptosis. Additionally, DEK overexpression reversed gigantol-induced effects on proliferation and apoptosis. Moreover, compared with the control group, gigantol treatment decreased Ki-67 and Bcl-2 expression levels, increased Bax expression levels and inactivated the Wnt/β-catenin signaling pathway, as assessed by RT-qPCR and/or western blot. DEK knockdown further increased gigantol-induced effects, but DEK overexpression reversed gigantol-induced effects. To conclude, the results of the present study suggested that gigantol inhibited cell proliferation and induced apoptosis by decreasing Ki-67 and Bcl-2 expression, increasing Bax expression and activating the Wnt/β-catenin signaling pathway by regulating DEK. The present study indicated the therapeutic potential of gigantol in patients with NSCLC. In addition, DEK may serve as a novel therapeutic target to enhance the effects of gigantol treatment.

Nuclear DEK preserves hematopoietic stem cells potential via NCoR1/HDAC3-Akt1/2-mTOR axis

The oncogene DEK is found fused with the NUP214 gene creating oncoprotein DEK-NUP214 that induces acute myeloid leukemia (AML) in patients, and secreted DEK protein functions as a hematopoietic cytokine to regulate hematopoiesis; however, the intrinsic role of nuclear DEK in hematopoietic stem cells (HSCs) remains largely unknown. Here, we show that HSCs lacking DEK display defects in long-term self-renew capacity, eventually resulting in impaired hematopoiesis. DEK deficiency reduces quiescence and accelerates mitochondrial metabolism in HSCs, in part, dependent upon activating mTOR signaling. At the molecular level, DEK recruits the corepressor NCoR1 to repress acetylation of histone 3 at lysine 27 (H3K27ac) and restricts the chromatin accessibility of HSCs, governing the expression of quiescence-associated genes (e.g., Akt1/2, Ccnb2, and p21). Inhibition of mTOR activity largely restores the maintenance and potential of Dek-cKO HSCs. These findings highlight the crucial role of nuclear DEK in preserving HSC potential, uncovering a new link between chromatin remodelers and HSC homeostasis, and have clinical implications.

Bacterial Growth Inhibition Screen (BGIS) identifies a loss-of-function mutant of the DEK oncogene, indicating DNA modulating activities of DEK in chromatin

The DEK oncoprotein regulates cellular chromatin function via a number of protein-protein interactions. However, the biological relevance of its unique pseudo-SAP/SAP-box domain, which transmits DNA modulating activities in vitro, remains largely speculative. As hypothesis-driven mutations failed to yield DNA-binding null (DBN) mutants, we combined random mutagenesis with the Bacterial Growth Inhibition Screen (BGIS) to overcome this bottleneck. Re-expression of a DEK-DBN mutant in newly established human DEK knockout cells failed to reduce the increase in nuclear size as compared to wild type, indicating roles for DEK-DNA interactions in cellular chromatin organization. Our results extend the functional roles of DEK in metazoan chromatin and highlight the predictive ability of recombinant protein toxicity in E. coli for unbiased studies of eukaryotic DNA modulating protein domains.

Bacterial Growth Inhibition Screen (BGIS): harnessing recombinant protein toxicity for rapid and unbiased interrogation of protein function

In two proof-of-concept studies, we established and validated the Bacterial Growth Inhibition Screen (BGIS), which explores recombinant protein toxicity in Escherichia coli as a largely overlooked and alternative means for basic characterization of functional eukaryotic protein domains. By applying BGIS, we identified an unrecognized RNA-interacting domain in the DEK oncoprotein (this study) and successfully combined BGIS with random mutagenesis as a screening tool for loss-of-function mutants of the DNA modulating domain of DEK [1]. Collectively, our findings shed new light on the phenomenon of recombinant protein toxicity in E. coli. Given the easy and rapid implementation and wide applicability, BGIS will extend the repertoire of basic methods for the identification, analysis and unbiased manipulation of proteins.

The FBXW7-NOTCH interactome: A ubiquitin proteasomal system-induced crosstalk modulating oncogenic transformation in human tissues

BACKGROUND

Ubiquitin ligases or E3 ligases are well programmed to regulate molecular interactions that operate at a post-translational level. Skp, Cullin, F-box containing complex (or SCF complex) is a multidomain E3 ligase known to mediate the degradation of a wide range of proteins through the proteasomal pathway. The three-dimensional domain architecture of SCF family proteins suggests that it operates through a novel and adaptable "super-enzymatic" process that might respond to targeted therapeutic modalities in cancer.

RECENT FINDINGS

Several F-box containing proteins have been characterized either as tumor suppressors (FBXW8, FBXL3, FBXW8, FBXL3, FBXO1, FBXO4, and FBXO18) or as oncogenes (FBXO5, FBXO9, and SKP2). Besides, F-box members like βTrcP1 and βTrcP2, the ones with context-dependent functionality, have also been studied and reported. FBXW7 is a well-studied F-box protein and is a tumor suppressor. FBXW7 regulates the activity of a range of substrates, such as c-Myc, cyclin E, mTOR, c-Jun, NOTCH, myeloid cell leukemia sequence-1 (MCL1), AURKA, NOTCH through the well-known ubiquitin-proteasome system (UPS)-mediated degradation pathway. NOTCH signaling is a primitive pathway that plays a crucial role in maintaining normal tissue homeostasis. FBXW7 regulates NOTCH protein activity by controlling its half-life, thereby maintaining optimum protein levels in tissue. However, aberrations in the FBXW7 or NOTCH expression levels can lead to poor prognosis and detrimental outcomes in patients. Therefore, the FBXW7-NOTCH axis has been a subject of intense study and research over the years, especially around the interactome's role in driving cancer development and progression. Several studies have reported the effect of FBXW7 and NOTCH mutations on normal tissue behavior. The current review attempts to critically analyze these mutations prognostic value in a wide range of tumors. Furthermore, the review summarizes the recent findings pertaining to the FBXW7 and NOTCH interactome and its involvement in phosphorylation-related events, cell cycle, proliferation, apoptosis, and metastasis.

CONCLUSION

The review concludes by positioning FBXW7 as an effective diagnostic marker in tumors and by listing out recent advancements made in cancer therapeutics in identifying protocols targeting the FBXW7-NOTCH aberrations in tumors.

Sevoflurane Limits Glioma Progression by Regulating Cell Proliferation, Apoptosis, Migration, and Invasion via miR-218-5p/DEK/β-Catenin Axis in Glioma

Purpose

Sevoflurane (SEV) is a frequently used volatile anesthetic in cancer surgery. Sevoflurane treatment has been shown to suppress the migration and invasion of several human cancer cells. However, the effect of sevoflurane on glioma remains largely unclear.

Methods

Glioma cell lines (U251 and U343) were treated by various concentrations of sevoflurane. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), flow cytometry assay, and transwell assay were performed to detect the cell viability, apoptosis, migration and invasion. Western blot assay was employed to detect the protein levels of β-catenin, c-Myc, CyclinD1, β-catenin, N-cadherin, vimentin, and DEK. Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) was used to examine the expression level of miR-218-5p. The target interaction between miR-218-5p and DEK was predicted through bioinformatics analysis and verified by dual-luciferase reporter assay system.

Results

We found that sevoflurane aberrantly inhibited the abilities on viability, migration, invasion, EMT and β-catenin signaling and promoted cell apoptosis in U251 and U343 cells in a dose-dependent manner. MiR-218-5p strikingly suppressed the abilities of proliferation, migration, invasion rather than apoptosis and activation of β-catenin signaling. Sevoflurane could facilitate the miR-218-5p expression, and its suppressing effects on glioma cells were reversed by pre-treatment with miR-218-5p inhibitors or pcDNA3.1/DEK in vitro and in vivo. Silencing of miR-218-5p reverted sh-DEK and sevoflurane-induced repression on proliferation, migration, invasion, and β-catenin signaling, and promotion on apoptosis in the glioma cells.

Conclusion

Our data showed that sevoflurane inhibited the proliferation, migration, invasion, and enhanced the apoptosis in glioma cells through regulating miR-218-5p/DEK/β-catenin axis.

MiR-138-5p Inhibits the Proliferation of Gastric Cancer Cells by Targeting DEK

Background

Increasing evidence suggests that microRNAs (miRNAs) play critical roles in cancer progression. Therefore, investigating the function of miRNAs that are aberrantly expressed in gastric cancer (GC) and characterizing the involved underlying mechanism are essential for the treatment of gastric cancer. MiR-138-5p was found to be down-regulated in multiple cancers, which acted as a tumor suppressor in cancer progression; however, whether and how miR-138-5p regulates the malignant behaviors of GC has not been fully understood.

Methods

The level of miR-138-5p in GC tissues and cell lines was detected by RT-qPCR. The effects of miR-138-5p on the growth of GC cells were evaluated by the in vitro Cell Counting Kit-8 (CCK-8) assay, cell apoptosis, cell cycle analysis, wound-healing assay, and in vivo xenograft mice model. The targets of miR-138-5p were predicted using the miRDB online tool, confirmed by luciferase report assay and Western blot.

Results

MiR-138-5p was frequently decreased in GC tissues and cell lines. Decreased expression of miR-138-5p was significantly associated with the lymph node metastasis of GC patients. Overexpression of miR-138-5p suppressed GC cell proliferation, migration, increased cell apoptosis as well as inhibited the tumor growth in vivo. DEK oncogene was predicted as a potential target of miR-138-5p. MiR-138-5p bound the 3'-UTR of DEK and inhibited the level of DEK in GC cells. Restoration of DEK abrogated miR-138-5p overexpression-mediated suppression of GC cell proliferation and cell cycle arrest.

Conclusion

Our results demonstrated the anti-cancer role of miR-138-5p in GC by targeting DEK, which suggested miR-138-5p as a potential therapeutic target for the treatment of patient with GC.

Role of the DEK oncogene in the development of squamous cell carcinoma

DEK is a highly conserved nuclear factor that plays an important role in the regulation of multiple cellular processes. DEK was discovered to be an oncogene as a fusion with NUP214 gene, which results in producing DEK-NUP214 proteins, in a subset of patients with acute myeloid leukemia. Subsequently, DEK overexpression was reported in many cancers, thus DEK itself is considered to be an oncoprotein. DEK has been reported to play important roles in the progression of early and late stage squamous cell carcinoma (SCC) and is useful for early diagnosis of the disease. These findings have made DEK an attractive therapeutic target, especially for human papillomavirus (HPV)-associated SCC. However, the mechanism of DEK in SCC remains unclear. In this review, we discuss human DEK oncogene-related SCC.

Cordycepin Inhibits Cancer Cell Proliferation and Angiogenesis through a DEK Interaction via ERK Signaling in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a malignant tumor that arises from the epithelial cells of the bile duct and is notorious for its poor prognosis. The clinical outcome remains disappointing, and thus more effective therapeutic options are urgently required. Cordycepin, a traditional Chinese medicine, provides multiple pharmacological strategies in antitumors, but its mechanisms have not been fully elucidated. In this study, we reported that cordycepin inhibited the viability and proliferation capacity of CCA cells in a time- and dose-dependent manner determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and colony formation assay. Flow cytometry and Hoechst dye showed that cordycepin induced cancer cell apoptosis via extracellular signal-regulated kinase (ERK) 1/2 deactivation. Moreover, cordycepin significantly reduced the angiogenetic capabilities of CCA in vitro as examined by tube formation assay. We also discovered that cordycepin inhibited DEK expression by using Western blot assay. DEK serves as an oncogenic protein that is overexpressed in various gastrointestinal tumors. DEK silencing inhibited CCA cell viability and angiogenesis but not apoptosis induction determined by Western blot and flow cytometry. Furthermore, cordycepin significantly inhibited tumor growth and angiogenic capacities in a xenograft model by downregulating the expression of DEK, phosphorylated ERK1/2 CD31 and von Willebrand factor (vWF). Taken together, we demonstrated that cordycepin inhibited CCA cell proliferation and angiogenesis with a DEK interaction via downregulation in ERK signaling. These data indicate that cordycepin may serve as a novel agent for CCA clinical treatment and prognosis improvement. SIGNIFICANCE STATEMENT: Cordycepin provides multiple strategies in antitumors, but its mechanisms are not fully elucidated, especially on cholangiocarcinoma (CCA). We reported that cordycepin inhibited the viability of CCA cells, induced apoptosis via extracellular signal-regulated kinase 1/2 deactivation and DEK inhibition, and reduced the angiogenetic capabilities of CCA both in vivo and in vitro.

DEK terminates diapause by activation of quiescent cells in the crustacean Artemia

To cope with harsh environments, the Artemia shrimp produces gastrula embryos in diapause, a state of obligate dormancy, having cellular quiescence and suppressed metabolism. The mechanism behind these cellular events remains largely unknown. Here, we study the regulation of cell quiescence using diapause embryos of Artemia We found that Artemia DEK (Ar-DEK), a nuclear factor protein, was down-regulated in the quiescent cells of diapause embryos and enriched in the activated cells of post-diapause embryos. Knockdown of Ar-DEK induced the production of diapause embryos whereas the control Artemia released free-swimming nuaplii. Our results indicate that Ar-DEK correlated with the termination of cellular quiescence via the increase in euchromatin and decrease in heterochromatin. The phenomena of quiescence have many implications beyond shrimp ecology. In cancer cells, for example, knockdown of DEK also induced a short period of cellular quiescence and increased resistance to environmental stress in MCF-7 and MKN45 cancer cell lines. Analysis of RNA sequences in Artemia and in MCF-7 revealed that the Wnt and AURKA signaling pathways were all down-regulated and the p53 signaling pathway was up-regulated upon inhibition of DEK expression. Our results provide insight into the functions of Ar-DEK in the activation of cellular quiescence during diapause formation in Artemia.

Expression of DEK in pancreatic cancer and its correlation with clinicopathological features and prognosis

Background: The oncogene DEK, which was originally identified as part of the protein product of the DEK-CAN fusion oncogene, has been shown to promote tumorigenesis in a variety of cancer cell types. However, little is known about the expression and role of DEK in pancreatic ductal adenocarcinoma (PDAC), which is one of the most refractory malignant tumors worldwide and has poor prognosis. Our study aimed to understand the role of DEK in the development and progression of pancreatic adenocarcinoma.

Materials and methods: We used western blotting and immunohistochemistry to examine the expression of DEK in pancreatic adenocarcinoma cells and tissues. We analyzed the correlation between DEK expression and clinicopathological characteristics and prognosis in 163 pancreatic adenocarcinoma patients.

Results: Protein levels of DEK in pancreatic adenocarcinoma tissues (76/136, 55.9%) were significantly higher than those in adjacent non-tumor tissues (16.2%, 22/136). A high expression level of DEK was associated with poor prognosis (P<0.001).In addition, the combination of CA19-9 and DEK expression (P<0.001) was a better prognostic indicator than CA19-9 expression alone (P=0.012).

Conclusions: DEK may play a significant role as a valuable biomarker in the development and progression of pancreatic adenocarcinoma. The combination of DEK and CA19-9 improves the prognostic prediction in patients with pancreatic adenocarcinoma.

Roles of DEK in the endometrium of mice in early pregnancy

Embryo implantation is a complex process requiring reciprocal interactions between implantation-competent blastocysts and receptive uteri. Accumulating evidence from Digital Protein Expression Profiling indicates that DEK protein expression at implantation sites (ISs) was much higher than that at inter-implantation sites (IISs). In this study, we investigated the expression of DEK in mouse uterus by immunohistochemistry (IHC), Western blotting. We explored its function during decidualization of uterine stromal cells by inhibiting the expression of DEK. In further study of mechanism, the cell proliferation, apoptosis and DNA damage were detected after inhibiting DEK during decidualization of stromal cells. The results suggest that DEK participates in decidualization of stromal cells through mediating cell proliferation, apoptosis and DNA repair.

Epithelial‑mesenchymal transition in colorectal carcinoma cells is mediated by DEK/IMP3

To investigate the inhibitory effects of DEK/insulin‑like growth factor II mRNA binding protein 3 (IMP3) on epithelial‑mesenchymal transition (EMT) in colorectal carcinoma cells. SW620 and SW480 cell lines were selected. DEK‑interfering lentivirus was transfected to knockdown DEK expression. Subsequently, MTT assays and flow cytometry were utilized to measure cell viability, and apoptosis, respectively. Cell invasion was detected using a Transwell assay. Quantitative polymerase chain reaction and western blot analysis were used to detect the expression of E‑cadherin, vimentin, and matrix metalloproteinase (MMP)‑9. Compared with the blank control, cells transfected with DEK‑interfering lentivirus demonstrated a remarkable reduction in cell viability (P<0.05). The apoptotic rate in the DEK‑interfering lentivirus group was significantly enhanced compared with the blank control group (P<0.05). In the DEK‑interfering lentivirus group, the expression of E‑cadherin was significantly elevated (P<0.05), while the expression of vimentin and MMP‑9 were significantly reduced in both cell lines (P<0.05). The results of the present study demonstrated that EMT of colorectal carcinoma cells was partially mediated by DEK, which likely affected the invasive ability of colorectal carcinoma cells. In addition, cell proliferation and apoptosis were susceptible to DEK silencing. The current study has provided experimental evidence for the treatment of colorectal carcinoma using DEK silencing.

Systems analysis identifies melanoma-enriched pro-oncogenic networks controlled by the RNA binding protein CELF1

Melanomas are well-known for their altered mRNA expression profiles. Yet, the specific contribution of mRNA binding proteins (mRBPs) to melanoma development remains unclear. Here we identify a cluster of melanoma-enriched genes under the control of CUGBP Elav-like family member 1 (CELF1). CELF1 was discovered with a distinct prognostic value in melanoma after mining the genomic landscape of the 692 known mRBPs across different cancer types. Genome-wide transcriptomic, proteomic, and RNA-immunoprecipitation studies, together with loss-of-function analyses in cell lines, and histopathological evaluation in clinical biopsies, revealed an intricate repertoire of CELF1-RNA interactors with minimal overlap with other malignancies. This systems approach uncovered the oncogene DEK as an unexpected target and downstream effector of CELF1. Importantly, CELF1 and DEK were found to represent early-induced melanoma genes and adverse indicators of overall patient survival. These results underscore novel roles of CELF1 in melanoma, illustrating tumor type-restricted functions of RBPs in cancer.

Neuroanatomical Distribution of DEK Protein in Corticolimbic Circuits Associated with Learning and Memory in Adult Male and Female Mice

DEK, a chromatin-remodeling gene expressed in most human tissues, is known for its role in cancer biology and autoimmune diseases. DEK depletion in vitro reduces cellular proliferation, induces DNA damage subsequently leading to apoptosis, and down-regulates canonical Wnt/β-catenin signaling, a molecular pathway essential for learning and memory. Despite a recognized role in cancer (non-neuronal) cells, DEK expression and function is not well characterized in the central nervous system. We conducted a gene ontology analysis (ToppGene), using a cancer database to identify genes associated with DEK deficiency, which pinpointed several genes associated with cognitive-related diseases (i.e., Alzheimer's disease, presenile dementia). Based on this information, we examined DEK expression in corticolimbic structures associated with learning and memory in adult male and female mice using immunohistochemistry. DEK was expressed throughout the brain in both sexes, including the medial prefrontal cortex (prelimbic, infralimbic and dorsal peduncular). DEK was also abundant in all amygdalar subdivisions (basolateral, central and medial) and in the hippocampus including the CA1, CA2, CA3, dentate gyrus (DG), ventral subiculum and entorhinal cortex. Of note, compared to males, females had significantly higher DEK immunoreactivity in the CA1, indicating a sex difference in this region. DEK was co-expressed with neuronal and microglial markers in the CA1 and DG, whereas only a small percentage of DEK cells were in apposition to astrocytes in these areas. Given the reported inverse cellular and molecular profiles (e.g., cell survival, Wnt pathway) between cancer and Alzheimer's disease, these findings suggest a potentially important role of DEK in cognition.

DEK promoted EMT and angiogenesis through regulating PI3K/AKT/mTOR pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer associated with poor prognosis. As an oncogene, DEK involves in regulation of various cellular metabolisms and plays an important role in tumor growth and progression. Increasing evidences suggested that abnormal expression of DEK is closely related to multiple malignant tumors. However, the possible involvement of DEK in epithelial to mesenchymal transition (EMT) and angiogenesis in TNBC remains unclear. In the present study, we revealed that the over-expression of DEK was significantly correlated with clinical stage, differentiation, and lymph node (LN) metastasis of TNBC and indicated poor overall survival of TNBC patients. Moreover, we demonstrated that DEK depletion could significantly reduce cell proliferation, migration, invasion and angiogenesis in vitro. We also found that DEK promoted cancer cell angiogenesis and metastasis by activating the PI3K/AKT/mTOR pathway. Furthermore, we revealed the inhibitory effect of DEK depletion on tumor growth and progression in a xenograft tumor model in mice. These data indicated that DEK promotes TNBC cell proliferation, angiogenesis, and metastasis via PI3K/AKT/mTOR signaling pathway, and therefore, it might be a potential target in TNBC therapy.

DEK proto-oncogene is highly expressed in astrocytic tumors and regulates glioblastoma cell proliferation and apoptosis

Astrocytic tumors are the most common neuroepithelial neoplasms with high relapse rate after surgery. Understanding the molecular mechanisms for astrocytic tumorigenesis and progression will lead to early diagnosis and effective treatment of astrocytic tumors. The DEK mRNA and protein expression in normal brain tissues and astrocytic tumors was quantified. To investigate DEK functions in tumor cells, DEK gene was silenced with siRNA in U251 glioblastoma cells. Cell proliferation, cell cycle and apoptosis were then measured. The expression and activity of key genes that regulate cell proliferation and apoptosis were also measured. We identified DEK as a high expressed gene in astrocytic tumor tissues. DEK expression level was positively correlated with the pathological grade of astrocytic tumors. Gene silencing of DEK in U251 glioblastomas inhibited cell proliferation and blocked cells at G0/G1 phase of cell cycle. DEK depletion also induced cell apoptosis, with up-regulated expression of P53 and P21 and down-regulated expression of Bcl-2 and C-myc. The Caspase-3 activity in U251 cells was also significantly increased after knockdown. Our results provided evidences that DEK regulates proliferation and apoptosis of glioblastomas. DEK gene silencing may induce apoptosis through P53-dependent pathway. Our data indicated DEK plays multiple roles to facilitate tumor growth and maintenance. It can be used as a potential target for astrocytic tumor diagnosis and gene therapy.

DEK protein level is a biomarker of CD138positive normal and malignant plasma cells

Overexpression of DEK oncogene is associated with increased proliferation of carcinoma cells and it is observed in several solid tumors due to the amplification of the 6p22.3 chromosomal region where DEK locates. Although the same chromosomal amplification occurs in multiple myeloma (MM), a plasma cell neoplasm, whether the expression and the copy number of the DEK gene are affected in MM remains elusive. We show that despite the increased copy number in CD138positive MM cells (4 out of 41 MM samples), DEK mRNA expression was down-regulated compared with that in CD138negative bone marrow (BM) cells of the same patients (P<0.0001). DEK protein was not detectable by immunohistochemistry (IHC) in CD138positive normal plasma cells or in malignant plasma cells of MM patients (n = 56) whereas it was widely expressed in normal and neoplastic B-cells. Stable knockdown or overexpression of DEK in CD138positive MM cell lines did not affect the proliferation and viability of the cells profoundly in the presence or absence of chemotherapeutic agent melphalan whereas knockdown of DEK moderately but significantly increased the expression level of CD138 (p<0.01). Decreased DEK expression in plasma cells suggests a potential role of this gene in plasma cell development and lack of detectable DEK protein by IHC could be used as a biomarker for normal and malignant plasma cells.

DEK oncogene is overexpressed during melanoma progression

DEK is an oncoprotein involved in a variety of cellular functions, such as DNA repair, replication, and transcriptional control. DEK is preferentially expressed in actively proliferating and malignant cells, including melanoma cell lines in which DEK was previously demonstrated to play a critical role in proliferation and chemoresistance. Still, the impact of this protein in melanoma progression remains unclear. Thus, we performed a comprehensive analysis of DEK expression in different melanocytic tumors. The immunostaining results of 303 tumors demonstrated negligible DEK expression in benign lesions. Conversely, malignant lesions, particularly in metastatic cases, were largely positive for DEK expression, which was partially associated with genomic amplification. Importantly, DEK overexpression was correlated with histological features of aggressiveness in primary tumors and poor prognosis in melanoma patients. In conclusion, our study provides new insight into the involvement of DEK in melanoma progression, as well as proof of concept for its potential application as a marker and therapeutic target of melanoma.

Lineage-specific roles of the cytoplasmic polyadenylation factor CPEB4 in the regulation of melanoma drivers

Nuclear 3'-end-polyadenylation is essential for the transport, stability and translation of virtually all eukaryotic mRNAs. Poly(A) tail extension can also occur in the cytoplasm, but the transcripts involved are incompletely understood, particularly in cancer. Here we identify a lineage-specific requirement of the cytoplasmic polyadenylation binding protein 4 (CPEB4) in malignant melanoma. CPEB4 is upregulated early in melanoma progression, as defined by computational and histological analyses. Melanoma cells are distinct from other tumour cell types in their dependency on CPEB4, not only to prevent mitotic aberrations, but to progress through G1/S cell cycle checkpoints. RNA immunoprecipitation, sequencing of bound transcripts and poly(A) length tests link the melanoma-specific functions of CPEB4 to signalling hubs specifically enriched in this disease. Essential in these CPEB4-controlled networks are the melanoma drivers MITF and RAB7A, a feature validated in clinical biopsies. These results provide new mechanistic links between cytoplasmic polyadenylation and lineage specification in melanoma.

Cytoplasmic polyadenylated transcripts have been poorly characterized, particularly in cancer. Here the authors identify a lineage-specific requirement of the cytoplasmic polyadenylation binding protein 4 (CPEB4) in malignant melanoma and show that it controls melanoma drivers MITF and RAB27A.

Transformation of human CD34+ hematopoietic progenitor cells with DEK-NUP214 induces AML in an immunocompromised mouse model

Acute myeloid leukemia (AML) is a heterogeneous disease comprising a large number of subtypes defined by specific chromosome abnormalities. One such subtype carries the t(6;9)(p22;q34) chromosome rearrangement, which leads to expression of the DEK-NUP214 chimeric gene, and has a particularly poor outcome. To provide a better understanding of the molecular etiology of these relatively rare individual AML variants, it is necessary to generate in vivo models, which can also serve as a means to evaluate targeted therapies based on their specific genetic abnormalities. Here, we describe the development of a human cell AML, generated in CD34+ human hematopoietic progenitor cells xenografted into immunocompromised mice that express human myeloid cell growth factors. Within 6 months, these mice develop a human cell AML with phenotypic characteristics of the primary t(6;9) disease and a CD45+CD13+CD34+CD38+ immunophenotype. Gene expression studies show that members of the HOX family of genes (HOXA9, 10, B3, B4 and PBX3) are highly upregulated in the AML from this mouse model as well as from primary human t(6;9) AML. Gene expression analysis also identified several other significantly disregulated pathways involving KRAS, BRCA1 and ALK, for example. This is the first report of a humanized model of the DEK-NUP214 disease and provides a means to study the development and treatment of this particular subtype of AML.

Creating chemotherapeutic-resistant breast cancer cell lines: advances and future perspectives

The development of resistance remains the most significant impediment to generating effective treatments for cancer. In the modern age of personalized medicine, it is of critical importance to understand the principles of both innate and acquired resistance to achieve the most effective therapeutic outcomes. Significant differences exist between cancer cells that exhibit innate resistance verses those that acquire resistance over time. Studying the acquisition of resistance is essential to obtaining a complete understanding of how treatments contribute to disease recurrence and progression. This review will evaluate the current understanding of chemotherapeutic resistance and its role in personalized medicine. This review will also explore how generating resistant cells in culture is essential to the development of improved cancer therapeutics.

Critical role of DEK and its regulation in tumorigenesis and metastasis of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related mortality globally. Therefore, it is quite essential to identify novel HCC-related molecules for the discovery of new prognostic markers and therapeutic targets. As an oncogene, DEK plays an important role in cell processes and participates in a variety of cellular metabolic functions, and its altered expression is associated with several human malignancies. However, the functional significance of DEK and the involved complex biological events in HCC development and progression are poorly understood. Here, combing the results from clinical specimens and cultured cell lines, we uncover a critical oncogenic role of DEK, which is highly expressed in HCC cells. DEK protein encompasses two isoforms (isoforms 1 and 2) and isoform 1 is the most frequently expressed DEK isoform in HCC cells. DEK depletion by using shRNA inhibited the cell proliferation and migration in vitro and suppressed tumorigenesis and metastasis in mouse models. Consistently, DEK overexpression regardless of which isoform produced the opposite effects. Further studies showed that DEK induced cell proliferation through upregulating cell cycle related CDK signaling, and promoted cell migration and EMT, at least in part, through the repression of β-catenin/E-cadherin axis. Interestingly, isoform 1 induced cell proliferation more efficiently than isoform 2, however, no functional differences existed between these two isoforms in cell migration. Together, our study indicates that DEK expression is required for tumorigenesis and metastasis of HCC, providing molecular insights for DEK-related pathogenesis and a basis for developing new strategies against HCC.

The DEK Oncoprotein Is a Critical Component of the EKLF/KLF1 Enhancer in Erythroid Cells

Understanding how transcriptional regulators are themselves controlled is important in attaining a complete picture of the intracellular effects that follow signaling cascades during early development and cell-restricted differentiation. We have addressed this issue by focusing on the regulation of EKLF/KLF1, a zinc finger transcription factor that plays a necessary role in the global regulation of erythroid gene expression. Using biochemical affinity purification, we have identified the DEK oncoprotein as a critical factor that interacts with an essential upstream enhancer element of the EKLF promoter and exerts a positive effect on EKLF levels. This element also binds a core set of erythroid transcription factors, suggesting that DEK is part of a tissue-restricted enhanceosome that contains BMP4-dependent and -independent components. Together with local enrichment of properly coded histones and an open chromatin domain, optimal transcriptional activation of the EKLF locus can be established.

MicroRNA-592 targets DEK oncogene and suppresses cell growth in the hepatocellular carcinoma cell line HepG2

MicroRNAs (miRNAs) are classes of small, non-coding RNAs that regulate the translation of target mRNA transcripts. In this study, we demonstrated that miR-592 was downregulated in human hepatocellular carcinoma (HCC) and could suppress growth of the human HCC cell line HepG2. A tumor oncogene, DEK, was identified as a direct target of miR-592. Luciferase report assay indicated miR-592 regulates DEK expression though bind to its 3'UTR. Furthermore, knockdown of DEK also suppressed cell proliferation of HepG2 cells, which was consist with miR-592. At last, we suggested that DEK was upregulated in HCC tissues inversely with miR-592. These results demonstrated that miR-592 targets DEK transcript and suppresses HCC cell growth, and may provide potential therapeutic target in human HCC.

Dissecting the Potential Interplay of DEK Functions in Inflammation and Cancer

There is a long-standing correlation between inflammation, inflammatory cell signaling pathways, and tumor formation. Understanding the mechanisms behind inflammation-driven tumorigenesis is of great research and clinical importance. Although not entirely understood, these mechanisms include a complex interaction between the immune system and the damaged epithelium that is mediated by an array of molecular signals of inflammation—including reactive oxygen species (ROS), cytokines, and NFκB signaling—that are also oncogenic. Here, we discuss the association of the unique DEK protein with these processes. Specifically, we address the role of DEK in chronic inflammation via viral infections and autoimmune diseases, the overexpression and oncogenic activity of DEK in cancers, and DEK-mediated regulation of NFκB signaling. Combined, evidence suggests that DEK may play a complex, multidimensional role in chronic inflammation and subsequent tumorigenesis.

The human oncoprotein and chromatin architectural factor DEK counteracts DNA replication stress

DNA replication stress is a major source of DNA strand breaks and genomic instability, and a hallmark of precancerous lesions. In these hyperproliferative tissues, activation of the DNA damage response results in apoptosis or senescence preventing or delaying their development to full malignancy. In cells, in which this antitumor barrier is disabled by mutations (for example, in p53), viability and further uncontrolled proliferation depend on factors that help to cope with replication-associated DNA damage. Replication problems preferentially arise in chromatin regions harboring complex DNA structures. DEK is a unique chromatin architectural factor which binds to non-B-form DNA structures, such as cruciform DNA or four-way junctions. It regulates DNA topology and chromatin organization, and is essential for the maintenance of heterochromatin integrity. Since its isolation as part of an oncogenic fusion in a subtype of AML, DEK has been consistently associated with tumor progression and chemoresistance. How DEK promotes cancer, however, is poorly understood. Here we show that DEK facilitates cellular proliferation under conditions of DNA replication stress by promoting replication fork progression. DEK also protects from the transmission of DNA damage to the daughter cell generation. We propose that DEK counteracts replication stress and ensures proliferative advantage by resolving problematic DNA and/or chromatin structures at the replication fork.

SiRNA knockdown of the DEK nuclear protein mRNA enhances apoptosis and chemosensitivity of canine transitional cell carcinoma cells

Transitional cell carcinoma (TCC) in dogs is an aggressive malignant neoplasm, originating in the epithelium of the urinary bladder. The DEK nuclear protein is overexpressed in several types of human bladder cancer, where it is involved in chromatin reconstruction, gene transcription and apoptosis. Since DEK represents a potential therapeutic target for canine TCC, this study was designed to investigate DEK expression in canine TCC and to determine the effects of DEK mRNA silencing on TCC cells in vitro. The gene expression profiles of seven selected cancer-associated genes was assessed in four canine TCC cell lines and expression of DEK protein was evaluated in bladder tissue biopsies from healthy dogs and those affected with cystitis or TCC. After transfection of four canine TCC cell lines with DEK-specific or scrambled siRNA, annexin V staining was performed to evaluate apoptosis, and methylthiazole tetrazolium assays were performed to assess both cell viability and sensitivity to carboplatin. DEK mRNA expression was relatively high in canine TCC cells and expression of the DEK protein was significantly greater in TCC tumours compared with the other tissue samples. After transfection with DEK-specific siRNA, apoptosis, cell growth inhibition, and enhanced sensitivity to carboplatin were observed in all TCC cells assessed. These research findings suggest that DEK could be a potential therapeutic target for canine TCC.

Identification of DEK as a potential therapeutic target for neuroendocrine prostate cancer

Neuroendocrine prostate cancer (NEPC) is an aggressive subtype of prostate cancer which does not respond to hormone therapy. Research of NEPC has been hampered by a lack of clinically relevant in vivo models. Recently, we developed a first-in-field patient tissue-derived xenograft model of complete neuroendocrine transdifferentiation of prostate adenocarcinoma. By comparing gene expression profiles of a transplantable adenocarcinoma line (LTL331) and its NEPC subline (LTL331R), we identified DEK as a potential biomarker and therapeutic target for NEPC. In the present study, elevated DEK protein expression was observed in all NEPC xenograft models and clinical NEPC cases, as opposed to their benign counterparts (0%), hormonal naïve prostate cancer (2.45%) and castration-resistant prostate cancer (29.55%). Elevated DEK expression was found to be an independent clinical risk factor, associated with shorter disease-free survival of hormonal naïve prostate cancer patients. DEK silencing in PC-3 cells led to a marked reduction in cell proliferation, cell migration and invasion. The results suggest that DEK plays an important role in the progression of prostate cancer, especially to NEPC, and provides a potential biomarker to aid risk stratification of prostate cancer and a novel target for therapy of NEPC.

DEK oncogene expression during normal hematopoiesis and in Acute Myeloid Leukemia (AML)

DEK is important in regulating cellular processes including proliferation, differentiation and maintenance of stem cell phenotype. The translocation t(6;9) in Acute Myeloid Leukemia (AML), which fuses DEK with NUP214, confers a poor prognosis and a higher risk of relapse. The over-expression of DEK in AML has been reported, but different studies have shown diminished levels in pediatric and promyelocytic leukemias. This study has characterized DEK expression, in silico, using a large multi-center cohort of leukemic and normal control cases. Overall, DEK was under-expressed in AML compared to normal bone marrow (NBM). Studying specific subtypes of AML confirmed either no significant change or a significant reduction in DEK expression compared to NBM. Importantly, the similarity of DEK expression between AML and NBM was confirmed using immunohistochemistry analysis of tissue mircorarrays. In addition, stratification of AML patients based on median DEK expression levels indicated that DEK showed no effect on the overall survival of patients. DEK expression during normal hematopoiesis did reveal a relationship with specific cell types implicating a distinct function during myeloid differentiation. Whilst DEK may play a potential role in hematopoiesis, it remains to be established whether it is important for leukemagenesis, except when involved in the t(6;9) translocation.

EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma

The aberrant transcription factor EWS-FLI1 drives Ewing sarcoma, but its molecular function is not completely understood. We find that EWS-FLI1 reprograms gene regulatory circuits in Ewing sarcoma by directly inducing or repressing enhancers. At GGAA repeat elements, which lack evolutionary conservation and regulatory potential in other cell types, EWS-FLI1 multimers induce chromatin opening and create de novo enhancers that physically interact with target promoters. Conversely, EWS-FLI1 inactivates conserved enhancers containing canonical ETS motifs by displacing wild-type ETS transcription factors. These divergent chromatin-remodeling patterns repress tumor suppressors and mesenchymal lineage regulators while activating oncogenes and potential therapeutic targets, such as the kinase VRK1. Our findings demonstrate how EWS-FLI1 establishes an oncogenic regulatory program governing both tumor survival and differentiation.

A DEK domain-containing protein modulates chromatin structure and function in Arabidopsis

Chromatin is a major determinant in the regulation of virtually all DNA-dependent processes. Chromatin architectural proteins interact with nucleosomes to modulate chromatin accessibility and higher-order chromatin structure. The evolutionarily conserved DEK domain-containing protein is implicated in important chromatin-related processes in animals, but little is known about its DNA targets and protein interaction partners. In plants, the role of DEK has remained elusive. In this work, we identified DEK3 as a chromatin-associated protein in Arabidopsis thaliana. DEK3 specifically binds histones H3 and H4. Purification of other proteins associated with nuclear DEK3 also established DNA topoisomerase 1α and proteins of the cohesion complex as in vivo interaction partners. Genome-wide mapping of DEK3 binding sites by chromatin immunoprecipitation followed by deep sequencing revealed enrichment of DEK3 at protein-coding genes throughout the genome. Using DEK3 knockout and overexpressor lines, we show that DEK3 affects nucleosome occupancy and chromatin accessibility and modulates the expression of DEK3 target genes. Furthermore, functional levels of DEK3 are crucial for stress tolerance. Overall, data indicate that DEK3 contributes to modulation of Arabidopsis chromatin structure and function.

Mechanisms underlying cancer growth and apoptosis by DEK overexpression in colorectal cancer

Our previous study indicated that DEK protein was overexpressed in colorectal carcinoma (CRC) compared with the normal colorectal mucosa. DEK was also significantly correlated with the prognostic characteristics of patients with CRC, demonstrating that DEK played an important role in CRC progression. In this work, we evaluate the effects of DEK on biological behaviors in CRC and explore the related molecular mechanisms. The results showed that DEK was overexpressed in human CRC tissues, and was correlated with the Ki-67 index and the apoptotic index. DEK depletion by RNAi in SW-620 and HCT116 cells significantly decreased cell proliferation, but increased cell apoptosis. Upregulation of DEK was involved in the p53/MDM, Bcl-2 family, and caspase pathways. Our study demonstrates that DEK promotes the growth of CRC, and could be a therapeutic target in CRC.

Prostate cancer. Ubiquitylome analysis identifies dysregulation of effector substrates in SPOP-mutant prostate cancer

Cancer genome characterization has revealed driver mutations in genes that govern ubiquitylation; however, the mechanisms by which these alterations promote tumorigenesis remain incompletely characterized. Here, we analyzed changes in the ubiquitin landscape induced by prostate cancer-associated mutations of SPOP, an E3 ubiquitin ligase substrate-binding protein. SPOP mutants impaired ubiquitylation of a subset of proteins in a dominant-negative fashion. Of these, DEK and TRIM24 emerged as effector substrates consistently up-regulated by SPOP mutants. We highlight DEK as a SPOP substrate that exhibited decreases in ubiquitylation and proteasomal degradation resulting from heteromeric complexes of wild-type and mutant SPOP protein. DEK stabilization promoted prostate epithelial cell invasion, which implicated DEK as an oncogenic effector. More generally, these results provide a framework to decipher tumorigenic mechanisms linked to dysregulated ubiquitylation.

The DEK oncoprotein binds to highly and ubiquitously expressed genes with a dual role in their transcriptional regulation

BACKGROUND

The DEK gene is highly expressed in a wide range of cancer cells, and a recurrent translocation partner in acute myeloid leukemia. While DEK has been identified as one of the most abundant proteins in human chromatin, its function and binding properties are not fully understood.

METHODS

We performed ChIP-seq analysis in the myeloid cell line U937 and coupled it with epigenetic and gene expression analysis to explore the genome-wide binding pattern of DEK and its role in gene regulation.

RESULTS

We show that DEK preferentially binds to open chromatin, with a low degree of DNA methylation and scarce in the heterochromatin marker H3K9me(3) but rich in the euchromatin marks H3K4me(2/3), H3K27ac and H3K9ac. More specifically, DEK binding is predominantly located at the transcription start sites of highly transcribed genes and a comparative analysis with previously established transcription factor binding patterns shows a similarity with that of RNA polymerase II. Further bioinformatic analysis demonstrates that DEK mainly binds to genes that are ubiquitously expressed across tissues. The functional significance of DEK binding was demonstrated by knockdown of DEK by shRNA, resulting in both significant upregulation and downregulation of DEK-bound genes.

CONCLUSIONS

We find that DEK binds to transcription start sites with a dual role in activation and repression of highly and ubiquitously expressed genes.

High expression of DEK predicts poor prognosis of gastric adenocarcinoma

BACKGROUND

DEK, as an oncoprotein, plays an important role in cancer development and progression. This study aimed to investigate the clinicopathological significance of DEK overexpression in patients with gastric cancer.

MATERIALS AND METHODS

The expression of DEK protein was evaluated by immunohistochemical (IHC) staining of 172 gastric cancer samples with complete clinicopathological features, and the correlation between DEK expression and clinicopathological features was examined. Survival rates were also calculated using the Kaplan-Meier method in gastric cancer patients with complete survival data.

RESULTS

DEK protein showed a strictly nuclear staining pattern in gastric cancers with IHC and immunofluorescence. The strongly positive rate of DEK protein was 60.5% (104/172) in gastric cancers, which was significantly higher than that in either gastric dysplasia (19.4%, 7/36) or adjacent normal mucosa (0%, 0/27). DEK expression in gastric cancer correlated to tumor size, differentiation, clinical stage, disease-free survival, and overall survival rates. Further analysis showed that patients with early-stage gastric cancer and high DEK expression had shorter disease-free survival and overall survival duration than those with low DEK expression.

CONCLUSION

High level of DEK protein expression predicts the poor prognosis of patients with gastric cancer. DEK expression might be potentially used as an independent effective biomarker for prognostic evaluation of gastric cancers.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/5050145571193097.