DEK oncoprotein regulates transcriptional modifiers and sustains tumor initiation activity in high-grade neuroendocrine carcinoma of the lung

Abstract

Lung cancer shows diverse histological subtypes. Largecell neuroendocrine cell carcinoma and small-cell lung carcinoma show similar histological features and clinical behaviors, and can be classified as high-grade neuroendocrine carcinoma (HGNEC) of the lung. Here we elucidated the molecular classification of pulmonary endocrine tumors by copy-number profiling. We compared alterations of copy number with the clinical outcome of HGNEC and identified a chromosomal gain of the DEK oncogene locus (6p22.3) that was significantly associated with poor prognosis. We further confirmed that DEK overexpression was associated with poor prognosis in a larger set of HGNEC. Downregulation of DEK by small hairpin RNA led to a marked reduction of in vitro colony formation, in vivo tumorigenicity and chemo-resistance, and was associated with loss of lung cancer stem cell markers. Gene expression profiling revealed that DEK downregulation was associated with altered expression of transcriptional regulators, which specifically include known targets of interchromosomal translocations in hematopoietic tumors, and knockdown of these epigenetic modifiers affected colony formation activity. Our study showed that DEK overexpression, partly through an increase in its gene dose, mediates the activity of global transcriptional regulators and is associated with tumor initiation activity and poor prognosis in HGNEC.

Stacking the DEK: From chromatin topology to cancer stem cells

“…136 Further support for DEK as a regulator of the Wnt/β-catenin signaling was published by Shibata et al, where DEK was shown to upregulate the expression of Wnt10b, a canonical Wnt ligand which can activate the Wnt/β-catenin pathway, in neuroendrocrine carcinomas of the lung. 142 Similar upregulation of Wnt10b was observed in human breast cancer cells using quantitative RT-PCR (our unpublished data). A feedback loop may exist as DEK has several GSK3β consensus sites, which, when phosphorylated, drive DEK ubiquitination and targeting for degradation by the Fbxw7 subunitcontaining SCF (Skp1/Cullin/F-box protein) E3 ubiquitin ligase complex.…”

“…144 Using cDNA microarrays from lung carcinoma cells expressing either non-targeting shRNA or DEK shRNA, Shibata et al also identified Notch pathway members Hes1 and NeuroD1 as downregulated in DEKsh cells. 142 The same study also identified a decrease in ABCA1 transporter, a member of the ABCG family of proteins responsible for drug resistance in stem cells, in DEKsh lung carcinoma cells. 142 In other cell types, including MDA-MB-468 breast cancer cells and near diploid immortalized keratinocytes that form skin (NIKS cells), high DEK expression resulted in increased levels of the p53 family member, ΔNp63α, which is thought to be an epithelial stem cell marker that can regulate Notch signaling.…”

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

“…Previous studies have revealed that DEK mRNA expression is increased in invasive ductal breast cancer, and has an increased gene expression in high-grade and late-stage breast cancer, therefore implicating it as a potential novel target in recurrent tumors (5,(22)(23)(24). In addition, Shibata et al (25) identified that DEK overexpression affects the activity of global transcriptional regulators and is associated with tumor development and a poor prognosis of patients with high-grade neuroendocrine carcinoma. Our previous study indicated that DEK was additionally significantly correlated with the prognostic characteristics of patients with colorectal cancer, and DEK depletion by RNAi in SW-620 and HCT116 cells significantly decreased cell proliferation and increased cell apoptosis.…”

Mutant IDH1 Confers an in Vivo Growth in a Melanoma Cell Line with BRAF Mutation

“…26 Colony formation assay and migration assay were performed as described. 27 To measure ROS accumulation, cells were stained with 5-(and-6)-chloromethyl-2,7-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H2DCFDA) (Molecular Probes, Eugene, OR), and fluorescence-activated cell sorting (FACS) analysis was performed using FACScalibur (BD Biosciences, San Jose, CA) as instructed by the manufacturer.…”

“…Data were normalized and statistical significance was measured by t-test with multiple testing correction (Benjamini and Hochberg false discovery rate) using GeneSpring software (Agilent Technologies). 27 Quantitative RT-PCR was performed in triplicate and evaluated using universal probes for each amplicon and the LightCycler system (Roche). Primers designed by ProbeFinder (Version 2.45; Roche).…”