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

Potential of DEK proto-oncogene as a prognostic biomarker for colorectal cancer: An evidence-based review

Given its role in tumorigenesis and its correlation with various pathologic features of colorectal cancer (CRC), DEK is considered to have the potential to predict CRC prognosis. This review attempts to summarize current knowledge and evidence supporting the potential of DEK as a prognostic biomarker of CRC. We searched meta-analyses, systematic reviews, cohort studies, and cell line studies published in the last 10 years. A literature search was conducted in PubMed, Pubmed Central (PMC), Proquest, EBSCOHost, Scopus, and Cochrane Library using the keywords 'colorectal/colon/rectal cancer', 'DEK', 'biomarker', and 'prognosis'. Studies that were not published in English, without accessible full text, unrelated to clinical questions, or conducted with a design unsuitable for the eligibility criteria were excluded. Seven included studies reported the potential of DEK as a prognostic biomarker of CRC and its role in cancer cell proliferation, invasion, and metastasis. This role is achieved through the Wnt/β-catenin pathway, prevention of apoptosis through destabilization of p53, and bridging inflammation and tumorigenesis through the nuclear factor (NF)-κB pathway, causing chronic inflammation and activation of tumorigenic genes. DEK overexpression is also associated with CRC clinical and pathological features, such as tumor size, lymph node metastasis, serosal invasion, differentiation, tumor staging, and epithelial-mesenchymal transition. DEK overexpression was found to be associated with lower survival and recovery rates. Its prognostic value was comparable with other prognostic biomarkers of CRC, such as BRAF, topoisomerase-1, and CEA. A cohort study reported that DEK overexpression was associated with a better response to fluoropyrimidine-based chemotherapy, while a cell-line study indicated a correlation between DEK overexpression with a worse response to irinotecan-based chemotherapy. In conclusion, considering its correlation with CRC pathology, its association with worse CRC patient survival, and its possibility to forecast the therapeutic response of various chemotherapeutic regimens, DEK has the potential to be used as a CRC prognostic biomarker.

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.

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 unique DEK oncoprotein in women's health: A potential novel biomarker

Breast and cervical cancer are the first and fourth cancer types with the highest prevalence in women, respectively. The developmental profiles of cancer in women can vary by genetic markers and cellular events. In turn, age and lifestyle influence in the cellular response and also on the cancer progression and relapse. The human DEK protein, a histone chaperone, belongs to a specific subclass of chromatin topology modulators, being involved in the regulation of DNA-dependent processes. These epigenetic mechanisms have dynamic and reversible nature, have been proposed as targets for different treatment approaches, especially in tumor therapy. The expression patterns of DEK vary between healthy and cancer cells. High expression of DEK is associated with poor prognosis in many cancer types, suggesting that DEK takes part in oncogenic activities via different molecular pathways, including inhibition of senescence and apoptosis. The focus of this review was to highlight the role of the DEK protein in these two female cancers.

Dek overexpression in murine epithelia increases overt esophageal squamous cell carcinoma incidence

Esophageal cancer occurs as either squamous cell carcinoma (ESCC) or adenocarcinoma. ESCCs comprise almost 90% of cases worldwide, and recur with a less than 15% five-year survival rate despite available treatments. The identification of new ESCC drivers and therapeutic targets is critical for improving outcomes. Here we report that expression of the human DEK oncogene is strongly upregulated in esophageal SCC based on data in the cancer genome atlas (TCGA). DEK is a chromatin-associated protein with important roles in several nuclear processes including gene transcription, epigenetics, and DNA repair. Our previous data have utilized a murine knockout model to demonstrate that Dek expression is required for oral and esophageal SCC growth. Also, DEK overexpression in human keratinocytes, the cell of origin for SCC, was sufficient to cause hyperplasia in 3D organotypic raft cultures that mimic human skin, thus linking high DEK expression in keratinocytes to oncogenic phenotypes. However, the role of DEK over-expression in ESCC development remains unknown in human cells or genetic mouse models. To define the consequences of Dek overexpression in vivo, we generated and validated a tetracycline responsive Dek transgenic mouse model referred to as Bi-L-Dek. Dek overexpression was induced in the basal keratinocytes of stratified squamous epithelium by crossing Bi-L-Dek mice to keratin 5 tetracycline transactivator (K5-tTA) mice. Conditional transgene expression was validated in the resulting Bi-L-Dek_K5-tTA mice and was suppressed with doxycycline treatment in the tetracycline-off system. The mice were subjected to an established HNSCC and esophageal carcinogenesis protocol using the chemical carcinogen 4-nitroquinoline 1-oxide (4NQO). Dek overexpression stimulated gross esophageal tumor development, when compared to doxycycline treated control mice. Furthermore, high Dek expression caused a trend toward esophageal hyperplasia in 4NQO treated mice. Taken together, these data demonstrate that Dek overexpression in the cell of origin for SCC is sufficient to promote esophageal SCC development in vivo.

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.

Decreased plasma DEK Oncogene Levels Correlate with p16-Negative Disease and Advanced Tumor Stage in a Case-Control Study of Patients with Head and Neck Squamous Cell Carcinoma

Head and neck cancer (HNC) remains the sixth most common malignancy worldwide and survival upon recurrence and/or metastasis remains poor. HNSCC has traditionally been associated with alcohol and nicotine use, but more recently the Human Papilloma Virus (HPV) has emerged as a favorable prognostic risk factor for oropharyngeal HNSCC. However, further stratification with additional biomarkers to predict patient outcome continues to be essential. One candidate biomarker is the DEK oncogenic protein, which was previously detected in the urine of patients with bladder cancer and is known to be secreted by immune cells such as macrophages. Here, we investigated if DEK could be detected in human plasma and if DEK levels correlated with clinical and pathological variables of HNSCC. Plasma was separated from the peripheral blood of newly diagnosed, untreated HNSCC patients or age-matched normal healthy controls and analyzed for DEK protein using ELISA. Plasma concentrations of DEK protein were lower in p16-negative tumors compared to both normal controls and patients with p16-positive tumors. Patients with lower plasma concentrations of DEK were also more likely to have late stage tumors and a lower white blood cell count. Contrary to previously published work demonstrating a poor prognosis with high intratumoral DEK levels, we show for the first time that decreased concentrations of DEK in patient plasma correlates with poor prognostic factors, including HPV-negative status as determined by negative p16 expression and advanced tumor stage.

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.

LCMR1 interacts with DEK to suppress apoptosis in lung cancer cells

To win the war against lung cancer, the molecular mechanisms underlying its oncogenesis and metastasis must be identified in order to develop novel diagnosis and treatment strategies. We previously identified a novel gene, namely lung cancer metastasis related protein 1 (LCMR1; GenBank accession no. AY148462), which was demonstrated to be overexpressed in non‑small‑cell lung cancer. LCMR1 expression was significantly associated with clinical stage. To further understand the mechanism of LCMR1 in lung cancer, the present study screened a cDNA library from the lung cancer cell line 95D for proteins interacting with LCMR1 by yeast two‑hybrid assay, and the protein DEK was identified. Co‑immunoprecipitation and glutathione S‑transferase pull‑down assays were performed to confirm the interaction between LCMR1 and DEK in vivo and in vitro. The results demonstrated that the interaction was mediated primarily by the N‑terminal region of DEK, suggesting that LCMR1 may be involved in the regulation of cell apoptosis. Using RNA interference, DEK and LCMR1 were demonstrated to cooperate in the inhibition of apoptosis in lung cancer cells, and this effect was associated with the induced myeloid leukemia protein cell differentiation protein 1 pathway. The present findings suggest that LCMR1 might serve as a potential molecular target for lung cancer therapy.

Arctii Fructus Inhibits Colorectal Cancer Cell Proliferation and MMPs Mediated Invasion via AMPK

Although Arctii Fructus (AF) has been shown to have various pharmacological effects, there have been no studies concerning the inhibitory effects of AF on the metastatic properties of colorectal cancer (CRC). The aim of this study was to investigate whether AF could suppress CRC progression by inhibiting cell growth, epithelial-mesenchymal transition (EMT), migration, and the invasion ability of CRC cells. AF decreased proliferation of CRC cells by inducing cell cycle arrest and apoptosis via extrinsic and intrinsic apoptotic pathways. Regarding metastatic properties, AF inhibited EMT by increasing the expression of the epithelial marker, E-cadherin, and decreasing the expression of the mesenchymal marker, N-cadherin, in CT26 cells. Moreover, AF decreased the migration and invasion of CT26 cells by inhibiting matrix metalloproteinase-2 (MMP-2) and MMP-9 activity. We confirmed that the decreased invasion ability and MMP-9 activity by AF treatment involved AMP-activated protein kinase (AMPK) activation. Collectively, this study demonstrates that AF inhibits the proliferation and metastatic properties of CRC cells.

Prognostic role of DEK in human solid tumors: a meta-analysis

Recently, the oncogenic role of DEK has been recognized in several cancer types. However, its prognostic role in human solid tumor remains unclear. Thus, the present meta-analysis, based on 14 published studies (2208 patients) searched from PubMed, Web of Science, and EMBASE databases, assessed the prognostic value of DEK in human solid tumors. Furthermore, the pooled hazard ratio (HR) for overall survival (OS) was evaluated with fixed-effects models. A subgroup analysis was also performed according to the patients' ethnicities and tumor types. Data from these published studies were extracted, and the results showed that the overexpression of DEK was significantly associated with poor OS in human solid tumors. The combined hazards ratio was (HR = 1.83; 95% CI, 1.64-2.05, P < 0.00001) for OS (univariable analysis) with a fixed-effects model without any significant heterogeneity (P = 0.71, I² = 0%). The combined HR was (HR = 1.70; 95% CI, 1.48-1.96, P < 0.00001) for OS (multivariable analysis) with a fixed-effects model, and no significant heterogeneity was observed (P = 0.36, I² = 9%). Therefore, the overexpression of DEK was correlated with poor survival in human solid tumors, which suggests that the expression status of DEK is a valuable biomarker for the prediction of prognosis and serves as a novel therapeutic target in human solid tumors.

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.

MiR-200a Suppresses the Proliferation and Metastasis in Pancreatic Ductal Adenocarcinoma through Downregulation of DEK Gene

MiR-200a has been reported to be able to suppress the epithelial-mesenchymal transition process in pancreatic cancer stem cells, suggesting that miR-200a could suppress the metastasis of pancreatic ductal adenocarcinoma (PDAC). However, its role in proliferation and metastasis of PDAC and the underlying mechanism by which miR-200a works in PDAC have not been elucidated. In our study, we for the first time identified that DEK gene is a direct downstream target of miR-200a. It was found that overexpression of miR-200a decreased DEK expression, suppressing the proliferation, migration, and invasion of PDAC cells. Meanwhile, knockdown of miR-200a can increase DEK level, promoting the proliferation, migration, and invasion of PDAC cells. Our study demonstrated that miR-200a suppresses the metastasis in pancreatic PDAC through downregulation of DEK, suggesting that miR-200a may be used as a novel potential marker in prediction of metastasis of PDAC.

Divergent clonal evolution of castration-resistant neuroendocrine prostate cancer

An increasingly recognized resistance mechanism to androgen receptor (AR)-directed therapy in prostate cancer involves epithelial plasticity, in which tumor cells demonstrate low to absent AR expression and often have neuroendocrine features. The etiology and molecular basis for this 'alternative' treatment-resistant cell state remain incompletely understood. Here, by analyzing whole-exome sequencing data of metastatic biopsies from patients, we observed substantial genomic overlap between castration-resistant tumors that were histologically characterized as prostate adenocarcinomas (CRPC-Adeno) and neuroendocrine prostate cancer (CRPC-NE); analysis of biopsy samples from the same individuals over time points to a model most consistent with divergent clonal evolution. Genome-wide DNA methylation analysis revealed marked epigenetic differences between CRPC-NE tumors and CRPC-Adeno, and also designated samples of CRPC-Adeno with clinical features of AR independence as CRPC-NE, suggesting that epigenetic modifiers may play a role in the induction and/or maintenance of this treatment-resistant state. This study supports the emergence of an alternative, 'AR-indifferent' cell state through divergent clonal evolution as a mechanism of treatment resistance in advanced prostate cancer.

Overexpression of DEK is an indicator of poor prognosis in patients with gastric adenocarcinoma

Increased expression of the human DEK proto-oncogene (DEK) gene has been associated with numerous human malignancies. The DEK protein is associated with chromatin reconstruction and gene transcription, and is important in cell apoptosis. The present study aimed to elucidate the role of DEK with regard to gastric adenocarcinoma tumor progression and patient prognosis. DEK protein expression was analyzed using immunohistochemistry in 192 tumors paired with adjacent non-cancerous gastric mucosa that had been surgically resected from patients with primary gastric adenocarcinoma. The association between DEK expression and the clinicopathological characteristics of the patients was evaluated using the χ² test and Fisher's exact test. The survival rates of the patients were calculated using the Kaplan-Meier method. Cox analysis evaluated the association between the expression of DEK and the survival rate of the patients. The DEK protein was expressed in 84 patients with gastric adenocarcinoma (43.8%) and in 20 of the paired normal gastric mucosa tissues (11.5%). The DEK expression rate was found to be associated with tumor size (P=0.006), tumor grade (P=0.023), lymph node metastasis (P=0.018), serous invasion (P=0.026), tumor stage (P=0.001) and Ki-67 expression (P=0.003). Furthermore, patients with gastric adenocarcinoma that expressed DEK had decreased disease-free (log-rank, 16.785; P<0.0001) and overall (log-rank, 15.759; P<0.0001) survival rates compared with patients without DEK expression. Patients with late-stage gastric adenocarcinoma that expressed DEK exhibited a lower overall survival rate compared with patients without DEK expression (P=0.002). Additional analysis revealed that DEK expression was an independent prognostic factor for the prognosis of gastric adenocarcinoma (hazard ratio, 0.556; 95% confidence interval, 0.337-0.918; P=0.022). From the results of the present study, it can be concluded that the detection of DEK protein expression in gastric adenocarcinoma tissues may be important for the diagnosis and prognosis of patients, and may be a targeted therapy for the treatment of gastric adenocarcinoma.

Significance of DEK overexpression for the prognostic evaluation of non-small cell lung carcinoma

In the present study, we explored the role of DEK expression for the prognostic evaluation of non-small cell lung carcinoma (NSCLC). DEK protein and mRNA expression levels were detected in NSCLC cells and fresh tissue samples of NSCLC paired with adjacent non-tumor tissues, respectively. NSCLC cases (n=196) meeting strict follow-up criteria were selected for immunohistochemical staining of DEK protein. Correlations between DEK expression and clinicopathological features of the NSCLC cases were evaluated using Chi-square tests. Survival rates were calculated using the Kaplan-Meier method, and the relationship between prognostic factors and patient overall survival was analyzed using Cox proportional hazard analysis. Based on the results, the levels of DEK protein and mRNA were significantly upregulated in 6 fresh tissue samples of NSCLC. Immunohistochemical analysis showed that the DEK expression rate was significantly higher in the NSCLC samples compared with either the adjacent non-tumor tissues or normal lung tissues. DEK expression was correlated with poor differentiation and late pathological stage of NSCLC. DEK expression was also correlated with low disease-free survival and overall survival rates. In the early-stage group, disease-free and overall survival rates of patients with DEK expression were significantly lower than those of patients without DEK expression. Further analysis using a Cox proportional hazard regression model revealed that DEK expression emerged as a significant independent hazard factor for the overall survival rate of patients with NSCLC. Consequently, DEK plays an important role in the progression of NSCLC. DEK may potentially be used as an independent biomarker for the prognostic evaluation of NSCLC.

DEK is a potential marker for aggressive phenotype and irinotecan-based therapy response in metastatic colorectal cancer

BACKGROUND

DEK is a transcription factor involved in stabilization of heterochromatin and cruciform structures. It plays an important role in development and progression of different types of cancer. This study aims to analyze the role of DEK in metastatic colorectal cancer.

METHODS

Baseline DEK expression was firstly quantified in 9 colorectal cell lines and normal mucosa by WB. SiRNA-mediated DEK inhibition was carried out for transient DEK silencing in DLD1 and SW620 to dissect its role in colorectal cancer aggressiveness. Irinotecan response assays were performed with SN38 over 24 hours and apoptosis was quantified by flow cytometry. Ex-vivo assay was carried out with 3 fresh tumour tissues taken from surgical resection and treated with SN38 for 24 hours. DEK expression was determined by immunohistochemistry in 67 formalin-fixed paraffin-embedded tumour samples from metastatic colorectal cancer patients treated with irinotecan-based therapy as first-line treatment.

RESULTS

The DEK oncogene is overexpressed in all colorectal cancer cell lines. Knock-down of DEK on DLD1 and SW620 cell lines decreased cell migration and increased irinotecan-induced apoptosis. In addition, low DEK expression level predicted irinotecan-based chemotherapy response in metastatic colorectal cancer patients with KRAS wild-type.

CONCLUSIONS

These data suggest DEK overexpression as a crucial event for the emergence of an aggressive phenotype in colorectal cancer and its potential role as biomarker for irinotecan response in those patients with KRAS wild-type status.