Death-associated protein kinase (DAPK) and signal transduction: additional roles beyond cell death

Evolution of Apoptotic Signaling Pathways Within Lophotrochozoans

Apoptosis is the main form of regulated cell death in metazoans. Apoptotic pathways are well characterized in nematodes, flies, and mammals, leading to a vision of the conservation of apoptotic pathways in metazoans. However, we recently showed that intrinsic apoptosis is in fact divergent among metazoans. In addition, extrinsic apoptosis is poorly studied in non-mammalian animals, making its evolution unclear. Consequently, our understanding of apoptotic signaling pathways evolution is a black box which must be illuminated by extending research to new biological systems. Lophotrochozoans are a major clade of metazoans which, despite their considerable biological diversity and key phylogenetic position as sister group of ecdysozoans (i.e. flies and nematodes), are poorly explored, especially regarding apoptosis mechanisms. Traditionally, each apoptotic signaling pathway was considered to rely on a specific initiator caspase, associated with an activator. To shed light on apoptosis evolution in animals, we explored the evolutionary history of initiator caspases, caspase activators, and the BCL-2 family (which control mitochondrial apoptotic pathway) in lophotrochozoans using phylogenetic analysis and protein interaction predictions. We discovered a diversification of initiator caspases in molluscs, annelids, and brachiopods, and the loss of key extrinsic apoptosis components in platyhelminths, along with the emergence of a clade-specific caspase with an ankyrin pro-domain. Taken together, our data show a specific history of apoptotic actors' evolution in lophotrochozoans, further demonstrating the appearance of distinct apoptotic signaling pathways during metazoan evolution.

Optogenetically engineered calcium oscillations promote autophagy-mediated cell death via AMPK activation

Autophagy is a double-edged sword for cells; it can lead to both cell survival and death. Calcium (Ca2+) signalling plays a crucial role in regulating various cellular behaviours, including cell migration, proliferation and death. In this study, we investigated the effects of modulating cytosolic Ca2+ levels on autophagy using chemical and optogenetic methods. Our findings revealed that ionomycin and thapsigargin induce Ca2+ influx to promote autophagy, whereas the Ca2+ chelator BAPTA-AM induces Ca2+ depletion and inhibits autophagy. Furthermore, the optogenetic platform allows the manipulation of illumination parameters, including density, frequency, duty cycle and duration, to create different patterns of Ca2+ oscillations. We used the optogenetic tool Ca2+-translocating channelrhodopsin, which is activated and opened by 470 nm blue light to induce Ca2+ influx. These results demonstrated that high-frequency Ca2+ oscillations induce autophagy. In addition, autophagy induction may involve Ca2+-activated adenosine monophosphate (AMP)-activated protein kinases. In conclusion, high-frequency optogenetic Ca2+ oscillations led to cell death mediated by AMP-activated protein kinase-induced autophagy.

Diagnostic Value of DAPK Methylation for Nasopharyngeal Carcinoma: Meta-Analysis

BACKGROUND

Methylation of DAPK has been reported to play a key role in the initiation and progression of nasopharyngeal cancer. However, there are differences between the studies on it. This meta-analysis was performed to evaluate the diagnostic value of DAPK promoter methylation for NPC.

METHOD

The study method involves the systematic research of eligible studies based on criteria. The frequency, odds ratios (OR), sensitivity as well as specificity with the corresponding 95% confidence intervals (CIs) were used to assess the effect sizes.

RESULTS

A total of 13 studies, including 1048 NPC samples and 446 non-cancerous samples, were used for the meta-analysis. The overall frequencies of DAPK methylation were 56.94% and 9.28% in NPC samples and non-cancerous samples, respectively. The association between DAPK methylation and risk of NPC was also confirmed by calculating the OR value which was 13.13 (95%CI = 54.24-40.72) based on a random-effect model (Q = 64.74; p < 0.0001; I2 = 81.47% with 95%CI for I2 = 69.39-88.78). Additionally, the study results suggest that testing for DAPK methylation in tissue samples or brushing may provide a promising method for diagnosing NPC.

CONCLUSION

This is the first meta-analysis that provided scientific evidence that methylation of the DAPK gene could serve as a potential biomarker for diagnosis, prognosis, and early screening of NPC patients.

Modulation of cellular autophagy by genotype 1 hepatitis E virus ORF3 protein

Hepatitis E virus (HEV) egresses from infected hepatocytes as quasienveloped particles containing open reading frame 3 (ORF3) protein. HEV ORF3 (small phosphoprotein) interacts with host proteins to establish a favourable environment for virus replication. It is a functional viroporin that plays an important role during virus release. Our study provides evidence that pORF3 plays a pivotal role in inducing Beclin1-mediated autophagy that helps HEV-1 replication as well as its exit from cells. The ORF3 interacts with host proteins involved in regulation of transcriptional activity, immune response, cellular and molecular processes, and modulation of autophagy, by interacting with proteins, DAPK1, ATG2B, ATG16L2 and also several histone deacetylases (HDACs). For autophagy induction, the ORF3 utilizes non-canonical NF-κB2 pathway and sequesters p52NF-κB and HDAC2 to upregulate DAPK1 expression, leading to enhanced Beclin1 phosphorylation. By sequestering several HDACs, HEV may prevent histone deacetylation to maintain overall cellular transcription intact to promote cell survival. Our findings highlight a novel crosstalk between cell survival pathways participating in ORF3-mediated autophagy.

Targeting Death-Associated Protein Kinases for Treatment of Human Diseases: Recent Advances and Future Directions

The death-associated protein kinase (DAPK) family is a member of the calcium/calmodulin-regulated serine/threonine protein kinase family, and studies have shown that its role, as its name suggests, is mainly to regulate cell death. The DAPK family comprises five members, including DAPK1, DAPK2, DAPK3, DRAK1 and DRAK2, which show high homology in the common N-terminal kinase domain but differ in the extra-catalytic domain. Notably, previous research has suggested that the DAPK family plays an essential role in both the development and regulation of human diseases. However, only a few small-molecule inhibitors have been reported. In this Perspective, we mainly discuss the structure, biological function, and role of DAPKs in diseases and the currently discovered small-molecule inhibitors, providing valuable information for the development of the DAPK field.

The role of pyrethroid derivatives in autophagy and apoptosis crosstalk signaling and potential risk for malignancies

Pyrethroids and its derivatives widespread and uncontrolled continuous use has influenced multiple deleterious effects resulting in as a potential risk factor causing damage to the organ systems. Allethrin and prallethrin are extensively used yet their influences on human primary cells are very limited or under reported. The potential mechanisms by which allethrin and prallethrin modulates human primary cells, especially the molecular mechanisms or interconnectivity of autophagy-apoptosis, their clinical relevance in human subjects or patients are not well defined. In this current study, we've furnished the evidence that both allethrin and prallethrin user samples significantly induced Ccl2 mRNA expression, increased amount of reactive oxygen intermediate, inhibited membrane bound enzymes and altered membrane fluidity. Pyrethroid derivative users had induced levels of lipid peroxidation and induced binding activities of transcription factors(tfs) like CEBP-β and NF-AT. Pyrethroid derivatives induced autophagy, elicited intracellular Ca2+ concentration, calcineurin and regulated proapoptotic genes, DAPK1, Bim. Our current study presumably comprises the initial investigation of a very new mechanism of pyrethroid derivatives-moderated programed cell death in various cell sets or types, like human primary cells where-in this is a late event, is documented. Hence, current research-study might be significant in the various pyrethroid derivatives-allied hematological-related cancers and immunosuppressant or auto-immune disorders. In the foremost instance, we present data stating that pyrethroid derivatives induces multiple cell signaling cascades, like CEBP-β, NF-AT, ERK and MAPK having a role in autophagy thereby; synchronously effectively impact on the apoptosis, therefore causing hematological tumors and toxic or immune related disorders.

Sirt7 associates with ELK1 to participate in hyperglycemia memory and diabetic nephropathy via modulation of DAPK3 expression and endothelial inflammation

Diabetic nephropathy (DN) is one of the most serious complications of advanced diabetes, and increases patient mortality. Recently, epigenetics-mediated hyperglycemic memory in pathological process of DN has received attention. The purpose of this study was to determine the underlying mechanism by which sirt7 modulates hyperglycemic memory in DN. In glomerular endothelial cells (GECs) cultured in high glucose and glomeruli of DN patients and rats, an increase in p65 phosphorylation and endothelial adhesion molecule levels persisted after glucose normalization but was reversed by glucose normalization associated with death-associated protein kinase-3 (DAPK3) knockout or DAPK3 inhibitor. High glucose-mediated decrease in sirt7, the deacetylase modulating H3K18-acetylation (H3K18ac), was sustained after normoglycemia. Sirt7 overexpression accompanied by glucose normalization suppressed DAPK3 expression and inflammation in GECs. Moreover, sh-sirt7-induced inflammation was inhibited by si-DAPK3. Furthermore, sirt7 and H3K18ac were located at the DAPK3 promoter region. ELK1 was found to combine with sirt7. si-ELK1 supplemented with normoglycemia inhibited high glucose-induced DAPK3 expression and inflammation in GECs. ELK1 overexpression-mediated inflammation was inhibited by si-DAPK3. In addition, ELK1 and sirt7 were located at the same promoter region of DAPK3. ELK1 overexpression enhanced DAPK3 promoter activity, which disappeared after specific binding site mutation. In vivo, sirt7 overexpression decreased inflammation and improved renal function during insulin treatment of DN rats, whereas insulin alone did not work. Our data demonstrated high glucose-mediated mutual inhibition between sirt7 and ELK1 induced DAPK3 transcription and inflammation despite normoglycemia in GECs, thus forming a vicious cycle and participating in the occurrence of hyperglycemic memory in DN.

DAPK1 Interacts with the p38 isoform MAPK14, Preventing its Nuclear Translocation and Stimulation of Bone Marrow Adipogenesis

Bone marrow (BM) adipose tissue (BMAT), a unique adipose depot, plays an important role in diseases such as osteoporosis and bone metastasis. Precise control of mesenchymal stem cell (MSC) differentiation is critical for BMAT formation and regeneration. Here, we show that death associated protein kinase 1 (DAPK1) negatively regulates BM adipogenesis in vitro and in vivo. Prx1 creDapk1 loxp/loxp mice showed more adipocytes in the femur than Dapk1 loxp/loxp mice. Further mechanistic analyses revealed that DAPK1 inhibits p38 mitogen-activated protein kinase (MAPK) signaling in the nucleus by binding the p38 isoform MAPK14, decreasing p38 nuclear activity, which subsequently inhibits BM adipogenesis. The inhibitory effect of DAPK1 against MAPK14 was independent of its kinase activity. In addition, the decreased DAPK1 was observed in the BM-MSCs of ageing mice. Our results reveal a previously undescribed function for DAPK1 in the regulation of adipogenesis, and may also reveal the underlying mechanism of BMAT formation in ageing.

The impact of DAPK1 and mTORC1 signaling association on autophagy in cancer

BACKGROUND

The autophagy pathway is used by eukaryotic cells to maintain metabolic homeostasis. Autophagy has two functions in cancerous cells which could inhibit tumorigenesis or lead to cancer progression by increasing cell survival and proliferation.

METHODS AND RESULTS

In this review article, Web of Science, PubMed, Scopus,  and Google Scholar were searched and summarized published studies to explore the relationship between DAPK1 and mTORC1 signaling association on autophagy in cancer. Autophagy is managed through various proteins including the mTOR, which is two separated structural and functional complexes known as mTORC1 and mTORC2. MTORC1 is an important component of the regulatory pathway affecting numerous cellular functions including proliferation, migration, invasion, and survival. This protein plays a key role in human cancers. The activity level of mTORC1 is regulated by the death-associated protein kinases (DAPks) family, especially DAPK1. In many cancers, DAPK1 acts as a tumor suppressor which can be attributed to its ability to suppress cellular transformation and to inhibit metastasis.

CONCLUSIONS

A deep investigation not only will reveal more about the function of DAPK1 but also might provide insights into novel therapies aimed to modulate the autophagy pathway in cancer and to achieve better cancer therapy.

Predictive significance of STK17A in patients with gastric cancer and association with gastric cancer cell proliferation and migration

Gastric cancer (GC) is one of the most frequently diagnosed types of cancer worldwide, and exploring its potential therapeutic targets is particularly important for improving the prognosis of patients with GC. The aim of the present study was to investigate the association between serine/threonine kinase 17a (STK17A) expression and GC prognosis. STK17A expression was measured by quantitative real-time PCR, western blotting and immunohistochemical staining. Standard stable transfection technology was also used to construct overexpression and knockdown cell lines. Wound healing, Transwell, Cell Counting Kit-8 and colony formation assays, as well as other methods, were used to explore the function and underlying molecular mechanism of STK17A in GC. The results indicated that STK17A overexpression significantly promoted the proliferation and migration of GC cells. The clinical significance of STK17A in a cohort of 102 cases of GC was assessed by clinical correlation and Kaplan-Meier analyses. Overexpression of STK17A was demonstrated to be associated with tumor invasion depth (P<0.001), lymph node metastasis (P<0.001) and poor prognosis in terms of 5-year survival (P<0.001). In addition, Cox multivariate analysis revealed that STK17A expression was an independent risk factor for overall and progress-free survival (P<0.001). Therefore, STK17A may be a valuable biomarker for the prognosis of patients with GC.

Identification and characterization of apoptosis-related gene serine/threonine kinase 17A (STK17A) from Japanese flounder Paralichthys olivaceus

Apoptosis plays important roles in regulation of the immune response and has a direct impact on disease resistance in teleost. Death associated protein kinase (DAPK)-related Serine/Threonine kinase 17A (STK17A) is a positive apoptosis regulator. However, the expression and function of STK17A in fish still remains uninvestigated. In this study, we identified and characterized a STK17A gene (termed PoSTK17A) from Japanese flounder Paralichthys olivaceus. We also investigated the pro-apoptotic role of PoSTK17A in fish. Real-time quantitative PCR analysis revealed that PoSTK17A is widely present in various Japanese flounder tissues, and dominantly expressed in liver. Immune challenge experiments showed that PoSTK17A expression was upregulated by inflammatory challenge, Edwardsiella tarda infection and DNA-damaging agent cisplatin treatment as well. Immunofluorescence microscopy revealed that the recombinant PoSTK17A proteins are mainly located in the nucleus of Japanese flounder FG-9307 cells, and human Hela and MCF7 cells. However, PoSTK17A was translocated from the nucleus to cytoplasm following cisplatin treatment. Overexpression of PoSTK17A significantly increased the apoptosis in human MCF7 cells through both cisplatin-dependent and independent manners. Importantly, PoSTK17A also promotes the ATP-gated P2X7 receptor-mediated apoptosis in Japanese flounder FG-9307 cells. Collectively, we characterized an inducible STK17A gene (PoSTK17A) that may play a conserved pro-apoptotic role in fish.

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

Current Landscape of Epigenetics in Lung Cancer: Focus on the Mechanism and Application

Lung cancer is the leading cause of cancer-related mortality worldwide. Tumorigenesis involves a multistep process resulting from the interactions of genetic, epigenetic, and environmental factors. Genome-wide association studies and sequencing studies have identified many epigenetic alterations associated with the development of lung cancer. Epigenetic mechanisms, mainly including DNA methylation, histone modification, and noncoding RNAs (ncRNAs), are heritable and reversible modifications that are involved in some important biological processes and affect cancer hallmarks. We summarize the major epigenetic modifications in lung cancer, focusing on DNA methylation and ncRNAs, their roles in tumorigenesis, and their effects on key signaling pathways. In addition, we describe the clinical application of epigenetic biomarkers in the early diagnosis, prognosis prediction, and oncotherapy of lung cancer. Understanding the epigenetic regulation mechanism of lung cancer can provide a new explanation for tumorigenesis and a new target for the precise treatment of lung cancer.

Inhibition of miR-34a-5p can rescue disruption of the p53-DAPK axis to suppress progression of clear cell renal cell carcinoma

DAPK, a transcriptional target of the p53 protein, has long been characterized as a tumor suppressor that acts as a negative regulator in multiple cellular processes. However, increasing studies have suggested that the role of DAPK may vary depending on cell type and cellular context. Thus far, the expression and function of DAPK in clear cell renal cell carcinoma (ccRCC) remain ambiguous. Since ccRCC behaves in an atypical way with respect to p53, whether the p53‐DAPK axis functions normally in ccRCC is also an intriguing question. Here, tissue specimens from 61 ccRCC patients were examined for DAPK expression. Functional studies regarding apoptosis, growth, and migration were used to determine the role of DAPK in renal cancer cells. The validity of the p53‐DAPK axis in ccRCC was also determined. Our study identified DAPK as a negative regulator of ccRCC, and its expression was reduced in certain subgroups. However, the p53‐DAPK axis was disrupted due to upregulation of miR‐34a‐5p under stressed conditions. miR‐34a‐5p was identified as a novel repressor of DAPK acting downstream of p53. Inhibition of miR‐34a‐5p can correct the p53‐DAPK axis disruption by upregulating DAPK protein and may have potential to be used as a therapeutic target to improve outcomes for ccRCC patients.

Death-Associated Protein Kinase 1 Phosphorylation in Neuronal Cell Death and Neurodegenerative Disease

Regulated neuronal cell death plays an essential role in biological processes in normal physiology, including the development of the nervous system. However, the deregulation of neuronal apoptosis by various factors leads to neurodegenerative diseases such as ischemic stroke and Alzheimer’s disease (AD). Death-associated protein kinase 1 (DAPK1) is a calcium/calmodulin (Ca²⁺/CaM)-dependent serine/threonine (Ser/Thr) protein kinase that activates death signaling and regulates apoptotic neuronal cell death. Although DAPK1 is tightly regulated under physiological conditions, DAPK1 deregulation in the brain contributes to the development of neurological disorders. In this review, we describe the molecular mechanisms of DAPK1 regulation in neurons under various stresses. We also discuss the role of DAPK1 signaling in the phosphorylation-dependent and phosphorylation-independent regulation of its downstream targets in neuronal cell death. Moreover, we focus on the major impact of DAPK1 deregulation on the progression of neurodegenerative diseases and the development of drugs targeting DAPK1 for the treatment of diseases. Therefore, this review summarizes the DAPK1 phosphorylation signaling pathways in various neurodegenerative diseases.

Death-associated protein kinase 3 deficiency alleviates vascular calcification via AMPK-mediated inhibition of endoplasmic reticulum stress

Vascular calcification (VC) is a critical feature of chronic kidney disease (CKD), diabetes, hypertension, and atherosclerosis. Death-associated protein kinase 3 (DAPK3) is involved in vascular remodeling in hypertension. However, it remains to be clarified whether DAPK3 controls vascular smooth muscle cell (VSMC) phenotypic transition into an osteogenic cell phenotype, which is an important process for VC. In vivo VC was induced in rats by vitamin D3 and nicotine. VSMCs were incubated with calcifying media containing β-glycerophosphate and Ca²⁺ to induce VC in vitro. Herein, we demonstrated increased expression of DAPK3 in the aortas of VC rats and VSMCs cultured in calcifying media. Knockdown of DAPK3 significantly inhibited calcifying media-induced VSMC mineralization and retarded the phenotypic transformation of VSMCs into osteogenic cells. Silencing of DAPK3 suppressed endoplasmic reticulum stress (ERS) related protein expressions, but upregulated the phosphorylation level of AMP-activated protein kinase (AMPK) in calcified VSMCs. Moreover, pretreatment with AMPK inhibitor Compound C abolished DAPK3 shRNA-mediated inhibition of ERS in VSMCs. In vivo, DAPK inhibitor significantly prevented calcium deposition in the aortas of VC rats. The present results revealed that DAPK3 modulated VSMC calcification through AMPK-mediated ERS signaling.

Drak/STK17A Drives Neoplastic Glial Proliferation through Modulation of MRLC Signaling

Glioblastoma (GBM) and lower grade gliomas (LGG) are the most common primary malignant brain tumors and are resistant to current therapies. Genomic analyses reveal that signature genetic lesions in GBM and LGG include copy gain and amplification of chromosome 7, amplification, mutation, and overexpression of receptor tyrosine kinases (RTK) such as EGFR, and activating mutations in components of the PI3K pathway. In Drosophila melanogaster, constitutive co-activation of RTK and PI3K signaling in glial progenitor cells recapitulates key features of human gliomas. Here we use this Drosophila glioma model to identify death-associated protein kinase (Drak), a cytoplasmic serine/threonine kinase orthologous to the human kinase STK17A, as a downstream effector of EGFR and PI3K signaling pathways. Drak was necessary for glial neoplasia, but not for normal glial proliferation and development, and Drak cooperated with EGFR to promote glial cell transformation. Drak phosphorylated Sqh, the Drosophila ortholog of nonmuscle myosin regulatory light chain (MRLC), which was necessary for transformation. Moreover, Anillin, which is a binding partner of phosphorylated Sqh, was upregulated in a Drak-dependent manner in mitotic cells and colocalized with phosphorylated Sqh in neoplastic cells undergoing mitosis and cytokinesis, consistent with their known roles in nonmuscle myosin-dependent cytokinesis. These functional relationships were conserved in human GBM. Our results indicate that Drak/STK17A, its substrate Sqh/MRLC, and the effector Anillin/ANLN regulate mitosis and cytokinesis in gliomas. This pathway may provide a new therapeutic target for gliomas.Significance: These findings reveal new insights into differential regulation of cell proliferation in malignant brain tumors, which will have a broader impact on research regarding mechanisms of oncogene cooperation and dependencies in cancer.See related commentary by Lathia, p. 1036.

Methyl-donor depletion of head and neck cancer cells in vitro establishes a less aggressive tumour cell phenotype

PURPOSE

DNA methylation plays a fundamental role in the epigenetic control of carcinogenesis and is, in part, influenced by the availability of methyl donors obtained from the diet. In this study, we developed an in-vitro model to investigate whether methyl donor depletion affects the phenotype and gene expression in head and neck squamous cell carcinoma (HNSCC) cells.

METHODS

HNSCC cell lines (UD-SCC2 and UPCI-SCC72) were cultured in medium deficient in methionine, folate, and choline or methyl donor complete medium. Cell doubling-time, proliferation, migration, and apoptosis were analysed. The effects of methyl donor depletion on enzymes controlling DNA methylation and the pro-apoptotic factors death-associated protein kinase-1 (DAPK1) and p53 upregulated modulator of apoptosis (PUMA) were examined by quantitative-PCR or immunoblotting.

RESULTS

HNSCC cells cultured in methyl donor deplete conditions showed significantly increased cell doubling times, reduced cell proliferation, impaired cell migration, and a dose-dependent increase in apoptosis when compared to cells cultured in complete medium. Methyl donor depletion significantly increased the gene expression of DNMT3a and TET-1, an effect that was reversed upon methyl donor repletion in UD-SCC2 cells. In addition, expression of DAPK1 and PUMA was increased in UD-SCC2 cells cultured in methyl donor deplete compared to complete medium, possibly explaining the observed increase in apoptosis in these cells.

CONCLUSION

Taken together, these data show that depleting HNSCC cells of methyl donors reduces the growth and mobility of HNSCC cells, while increasing rates of apoptosis, suggesting that a methyl donor depleted diet may significantly affect the growth of established HNSCC.

5-Azacytidine treatment induces demethylation of DAPK1 and MGMT genes and inhibits growth in canine mammary gland tumor cells

Background

Canine mammary gland tumors (CMGTs) are the most common, spontaneous types of neoplasias in female dogs. Aberrant DAPK1 and MGMT methylation associated with tumor formation and development in various cancers. 5-Azacytidine is a known specific demethylation drug that covalently binds to DNA methyltransferase. However, the methylation of the DAPK1 and MGMT is unknown with respect to CMGTs. Therefore, we sought to demonstrate the effects of 5-azacytidine on the proliferation of CMGTs cell, and elucidate the potential molecular mechanisms of action in these cancerous cells.

Materials and methods

The effects of 5-azacytidine on CHMm and CHMp cell proliferation were evaluated by MTT assay. The DAPK1 and MGMT gene methylation patterns in CHMm and CHMp cells and CMGTs blood/tissue samples were analyzed by MSP assay. Effect of 5-azacytidine on the methylation of DAPK1 and MGMT gene, and DAPK1 and MGMT mRNA expression in CHMm and CHMp cells were analyzed by MSP assay and qRT-PCR assay, respectively.

Results

5-Azacytidine may suppress the proliferation of CHMm and CHMp cells. Furthermore, the DAPK1 and MGMT genes were hypermethylated in CHMm/CHMp cells and clinical malignant tumor samples, but not in normal female dogs’ blood and tissue. However, the DAPK1 and MGMT genes were re-inducible in CHMm and CHMp cells treated with 5 μM 5-azacytidine. Meanwhile, 5-azacytidine increased the expression of DAPK1 and MGMT mRNA.

Conclusion

These results suggest that DAPK1 and MGMT methylation can serve as sensitive diagnostic biomarkers and therapeutic targets for CMGTs. 5-Azacytidine also could be a potential therapeutic candidate for CMGTs.

Evaluation of the prognostic and physiological functions of death associated protein kinase 1 in breast cancer

Death associated protein kinase 1 (DAPK1) is a notable serine/threonine kinase involved in the regulation of multiple cellular pathways, including apoptosis and autophagy. Although DAPK1 is usually considered to be a tumor suppressor, it was previously reported to promote the viability of p53 mutant cancer cell lines and possess physiological oncogenic functions in breast cancer. However, the ability of endogenous DAPK1 to suppress breast cancer cell mobility has not been assessed. In the present study, the prognostic function of DAPK1 in a Chinese patient cohort was evaluated, and no significant association was observed between DAPK1 expression and patient survival or lymph node metastasis. In order to investigate the physiological function of endogenous DAPK1, stable inducible DAPK1 knockdown MCF7 and MDA-MB-231 cell lines were established. Consistent with previous studies, endogenous DAPK1 only regulated cell viability in p53 mutant MDA-MB-231 cells. However, knockdown of DAPK1 did not significantly affect cell motility of either MCF7 or MDA-MB-231 cells. Altogether, these results further explored the function of endogenous DAPK1 in breast cancer and may shed light in understanding the molecular signaling pathways regulating the physiological function of DAPK1.

Gene methylation as a powerful biomarker for detection and screening of non-small cell lung cancer in blood

DNA methylation has been reported to become a potential powerful tool for cancer detection and diagnosis. However, the possibilities for the application of blood-based gene methylation as a biomarker for non-small cell lung cancer (NSCLC) detection and screening remain unclear. Hence, we performed this meta-analysis to evaluate the value of gene methylation detected in blood samples as a noninvasive biomarker in NSCLC. A total of 28 genes were analyzed from 37 case-control studies. In the genes with more than three studies, we found that the methylation of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT was significantly associated with risks of NSCLC. The methylation statuses of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT were not linked to age, gender, smoking behavior, and tumor stage and histology in NSCLC. Therefore, the use of the methylation status of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT could become a promising and powerful biomarker for the detection and screening of NSCLC in blood in clinical settings. Further large-scale studies with large sample sizes are necessary to confirm our findings in the future.

Quantitative and correlation analysis of the DNA methylation and expression of DAPK in breast cancer

Background

Death-associated protein kinase 1 (DAPK) is an important tumor suppressor kinase involved in the regulation of multiple cellular activities such as apoptosis and autophagy. DNA methylation of DAPK gene was found in various types of cancers and often correlated with the clinicopathological characteristics. However, the mRNA and protein expression of DAPK in the same sample was rarely measured. Thus, it was unclear if the correlation between DAPK gene methylation and clinicopathological parameters was due to the loss of DAPK expression.

Methods

In this study, the DNA methylation rate, mRNA and protein expression of DAPK was quantitatively detected in 15 pairs of breast cancer patient samples including tumor (T) and adjacent non-tumor (N) tissues.

Results

The correlation between DNA methylation rate and mRNA expression, together with the correlation between mRNA and protein expression, was calculated. No correlation was observed between any levels using either the measurement value of each sample or the T/N ratio of each pair.

Discussion

These data suggested that the DNA methylation status of DAPK did not correlate well with its mRNA or protein expression. Extra caution is needed when interpreting the DNA methylation data of DAPK gene in clinical studies.

DANGER is involved in high glucose-induced radioresistance through inhibiting DAPK-mediated anoikis in non-small cell lung cancer

¹⁸F-labeled fluorodeoxyglucose (FDG) uptake during FDG positron emission tomography seems to reflect increased radioresistance. However, the exact molecular mechanism underlying high glucose (HG)-induced radioresistance is unclear. In the current study, we showed that ionizing radiation-induced activation of the MEK-ERK-DAPK-p53 signaling axis is required for anoikis (anchorage-dependent apoptosis) of non-small cell lung cancer (NSCLC) cells in normal glucose media. Phosphorylation of DAPK at Ser734 by ERK was essential for p53 transcriptional activity and radiosensitization. In HG media, overexpressed DANGER directly bound to the death domain of DAPK, thus inhibiting the catalytic activity of DAPK. In addition, inhibition of the DAPK-p53 signaling axis by DANGER promoted anoikis-resistance and epithelial-mesenchymal transition (EMT), resulting in radioresistance of HG-treated NSCLC cells. Notably, knockdown of DANGER enhanced anoikis, EMT inhibition, and radiosensitization in a mouse xenograft model of lung cancer. Taken together, our findings offered evidence that overexpression of DANGER and the subsequent inhibitory effect on DAPK kinase activity are critical responses that account for HG-induced radioresistance of NSCLC.

Noncanonical Fungal Autophagy Inhibits Inflammation in Response to IFN-γ via DAPK1

Defects in a form of noncanonical autophagy, known as LC3-associated phagocytosis (LAP), lead to increased inflammatory pathology during fungal infection. Although LAP contributes to fungal degradation, the molecular mechanisms underlying LAP-mediated modulation of inflammation are unknown. We describe a mechanism by which inflammation is regulated during LAP through the death-associated protein kinase 1 (DAPK1). The ATF6/C/EBP-β/DAPK1 axis activated by IFN-γ not only mediates LAP to Aspergillus fumigatus but also concomitantly inhibits Nod-like receptor protein 3 (NLRP3) activation and restrains pathogenic inflammation. In mouse models and patient samples of chronic granulomatous disease, which exhibit defective autophagy and increased inflammasome activity, IFN-γ restores reduced DAPK1 activity and dampens fungal growth. Additionally, in a cohort of hematopoietic stem cell-transplanted patients, a genetic DAPK1 deficiency is associated with increased inflammation and heightened aspergillosis susceptibility. Thus, DAPK1 is a potential drugable player in regulating the inflammatory response during fungal clearance initiated by IFN-γ.

Clinical effect of DAPK promoter methylation in gastric cancer: A systematic meta-analysis

BACKGROUND

The loss of death-associated protein kinase (DAPK) gene expression through promoter methylation is involved in many tumors. However, the relationship between DAPK promoter methylation and clinicopathological features of gastric cancer (GC) remains to be done. Therefore, we performed a meta-analysis to assess the role of DAPK promoter methylation in GC.

METHODS

Literature databases were searched to retrieve eligible studies. The pooled odds ratios (ORs) with its 95% confidence intervals (CIs) were calculated using the Stata 12.0 software.

RESULTS

Final 22 available studies with 1606 GC patients and 1508 nonmalignant controls were analyzed. A significant correlation was found between DAPK promoter methylation and GC (OR = 3.23, 95% CI = 1.70-6.14, P < 0.001), but we did not find any significant association in Caucasian population, and in blood samples in subgroup analyses. DAPK promoter methylation was associated with tumor stage and lymph node status (OR = 0.69, 95% CI = 0.49-0.96, P = 0.03; OR = 1.50, 95% CI = 1.12-2.01, P = 0.007; respectively). However, we did not find that DAPK promoter methylation was associated with gender status and tumor histology.

CONCLUSION

Our findings suggested that DAPK promoter methylation may play a key role in the carcinogenesis and progression of GC. In addition, methylated DAPK was a susceptible gene for Asian population. However, more studies with larger subjects should be done to further evaluate the effect of DAPK promoter methylation in GC patients, especially in blood and Caucasian population subgroup.

Molecular analysis of apoptosis pathway after photodynamic therapy in breast cancer: Animal model study

BACKGROUND

Molecular investigation of breast tumors has permitted better understanding about interaction of genes and pathways involved in tumor progression.

OBJECTIVE

The aim of this study was to evaluate the association between genes belonging to the pathway of apoptosis with tumor response to photodynamic therapy.

STUDY DESIGN/MATERIALS AND METHODS

The mammary tumors were induced in twenty-four Spraguey-Dawley female rats by oral gavage of 7,12-dimethylbenz(a)anthracene (8mg/Kg body weight). Animals were divided into three groups: G1 (normal tissue), G2 (tumors without treatment), G3 (animals euthanized 48h after treatment). The photosensitizer used was a chlorin, 5,15-bis-(2-bromo-5-hydroxyphenyl) chlorin in the dose of 8mg/kg for each animal. Light source of diode laser at a wavelength of 660nm, fluence rate of 100mW/cm, and light dose of 100J/cm was delivery to lesions for treatment. A sample from each animal was investigated by quantitative real time PCR using Rat Apoptosis RT(2) Profiler™ PCR Array platform.

RESULTS

Pro-apoptotic BAK1, CARD6, CASP8, CIDEA, CIDEB, DAPK1, TNF, TNFRSF10B, FASLG, LOC687813, and TP73 genes showed increased expression, and CD40 anti-apoptotic gene showed decreased expression in the group who underwent PDT (G3) in relation to G2.

CONCLUSION

The results indicated that these genes are involved more directly with cellular apoptosis induced by PDT using the Chlorin photosensitizer.

Expression and localization of calmodulin-related proteins in brain, heart and kidney from spontaneously hypertensive rats

Blood pressure is regulated not only by peripheral arterial resistance, but also by heart, kidney, and central nervous system. We have previously demonstrated that expression level of calmodulin-related proteins including eukaryotic elongation factor 2 kinase (eEF2K), death-associated protein kinase (DAPK)3, and histone deacetylase (HDAC)4 was specifically elevated in mesenteric artery from spontaneously hypertensive rats (SHR), which partly contributes to the development of hypertension via vascular inflammation and structural remodeling. We tested the hypothesis whether expression and localization of eEF2K, DAPK3, and HDAC4 are altered in brain, heart, and kidney from SHR. After brain, left ventricles (LV), and kidney were isolated from 12-week-old male Wistar Kyoto rats (WKY) and SHR, Western blotting and histological analysis were performed. In brain tissue, protein expression of eEF2K and HDAC4 was abundant, whereas DAPK3 protein was less. HDAC4 protein expression in SHR brain was significantly higher than that in WKY brain. In LV, protein expression of eEF2K was relatively higher than DAPK3 or HDAC4, and it was significantly higher in SHR than WKY. In kidney tissue, protein expression of DAPK3 was the highest and seemed to be localized specifically to renal tubule. The present results indicate that the increased HDAC4 in brain and increased eEF2K in LV might be at least in part related to the development of hypertension.

Overexpression of microRNA-133a inhibits ischemia-reperfusion-induced cardiomyocyte apoptosis by targeting DAPK2

To examine microRNA-133a (miR-133a) endogenous expression in cardiomyocytes after ischemia-reperfusion (I/R) injury and study the effects of miR-133a overexpression on I/R injury-induced cardiomyocyte apoptosis. Dual-Luciferase Reporter Assay detected dynamic expression of miR-133a. In an in vitro hypoxia-reoxygenation (HR) injury model and an in vivo rat model of I/R injury, rat cardiomyocytes were transfected with miR-133a mimic to test the effects of miR-133a overexpression on apoptosis. MiR-133a and Death Associated Protein Kinase 2 (DAPK2) mRNA expression was measured using real-time-PCR, and DAPK2 protein expression was detected by western blotting. Annexin V-fluorescein isothiocyanate/propidium iodide (PI) double-staining measured the apoptosis rate in H9C2 cells and transferase dUTP nick end labeling assay quantified the cardiomyocyte apoptosis rate in tissues obtained from in vivo the rat model. DAPK2 is a target of miR-133a. Both in vitro and in vivo results confirmed that after expression of miR-133a mimics, miR-133a levels increased, which was accompanied by decrease in DAPK2 mRNA and protein expression. In H9C2 cells, HR injury caused a sharp decrease in miR-133a expression and a significant upregualtion of DAPK2 mRNA and protein levels. However, exogenous miR-133a expression led to a significant reduction in DAPK2 mRNA and protein levels despite HR injury. Similar results were obtained from in vivo I/R injury model. After HR injury or I/R injury the apoptosis rate of myocardial cells was highly elevated and decreased significantly only after transfection of miR-133a into cardiomyocytes. MiR-133a overexpression may inhibit I/R injury-mediated cardiomyocyte apoptosis by targeting DAPK2, leading to reduced DAPK2 protein, thus miR-133a may potentially have a high therapeutic value in I/R injury.

Novel Cancer Therapeutics with Allosteric Modulation of the Mitochondrial C-Raf-DAPK Complex by Raf Inhibitor Combination Therapy

Mitochondria are the powerhouses of cells. Mitochondrial C-Raf is a potential cancer therapeutic target, as it regulates mitochondrial function and is localized to the mitochondria by its N-terminal domain. However, Raf inhibitor monotherapy can induce S338 phosphorylation of C-Raf (pC-Raf(S338)) and impede therapy. This study identified the interaction of C-Raf with S308 phosphorylated DAPK (pDAPK(S308)), which together became colocalized in the mitochondria to facilitate mitochondrial remodeling. Combined use of the Raf inhibitors sorafenib and GW5074 had synergistic anticancer effects in vitro and in vivo, but targeted mitochondrial function, rather than the canonical Raf signaling pathway. C-Raf depletion in knockout MEF(C-Raf-/-) or siRNA knockdown ACHN renal cancer cells abrogated the cytotoxicity of combination therapy. Crystal structure simulation showed that GW5074 bound to C-Raf and induced a C-Raf conformational change that enhanced sorafenib-binding affinity. In the presence of pDAPK(S308), this drug-target interaction compromised the mitochondrial targeting effect of the N-terminal domain of C-Raf, which induced two-hit damages to cancer cells. First, combination therapy facilitated pC-Raf(S338) and pDAPK(S308) translocation from mitochondria to cytoplasm, leading to mitochondrial dysfunction and reactive oxygen species (ROS) generation. Second, ROS facilitated PP2A-mediated dephosphorylation of pDAPK(S308) to DAPK. PP2A then dissociated from the C-Raf-DAPK complex and induced profound cancer cell death. Increased pDAPK(S308) modification was also observed in renal cancer tissues, which correlated with poor disease-free survival and poor overall survival in renal cancer patients. Besides mediating the anticancer effect, pDAPK(S308) may serve as a predictive biomarker for Raf inhibitors combination therapy, suggesting an ideal preclinical model that is worthy of clinical translation.

Death-associated protein kinase: A molecule with functional antagonistic duality and a potential role in inflammatory bowel disease (Review)

The cytoskeleton-associated serine/threonine kinase death-associated protein kinase (DAPK) has been described as a cancer gene chameleon with functional antagonistic duality in a cell type and context specific manner. The broad range of interaction partners and substrates link DAPK to inflammatory processes especially in the gut. Herein we summarize our knowledge on the role of DAPK in different cell types that play a role under inflammatory conditions in the gut. Besides some promising experimental data suggesting DAPK as an interesting drug target in inflammatory bowel disease there are many open questions regarding direct evidence for a role of DAPK in intestinal inflammation.

DAPK and cytoskeleton-associated functions

Death-associated protein kinase (DAPK) undergoes activation in response to various death stimuli, and they have been associated with an increase in DAPK catalytic activity. One of the most prominent features of DAPK-induced cell death is the effect on the cytoskeleton, including loss of matrix attachment, and membrane blebbing. One known cytoskeletal-associated substrate of DAPK is the myosin-II light chain, phosphorylated by DAPK on Ser(19), thus stabilizing actin stress fibres. Moreover, paxillin, a component of focal adhesions, was found to be localized in close proximity to the tips of the DAPK-positive filaments, indicating that stress fibres containing DAPK extend to focal contacts. Forced expression of DAPK in multiple cell types results in morphological changes such as cell rounding, membrane blebbing, shrinking and detachment. During directed migration, DAPK functions as a potent inhibitor of cell polarization, as evidenced by its perturbation of the formation of static protrusion at the leading edge. Furthermore, DAPK inhibits random migration by suppressing directional persistence. One of the studies considered DAPK as an anoikis inducer. Others showed that DAP-kinase inhibits the activities of cell surface integrins by converting them into an inactive conformation. Biochemical experiments have established the DAPK binding to Syntaxin1 and its subsequent phosphorylation at Ser(188) in a Ca(2+) dependent manner. This phosphorylation event has been shown to decrease the binding of Syntaxin to MUNC18-1, a protein critically involved in synaptic vesicle docking. Here, we have investigated the structural interactions that modulate DAPK phosphorylation with Syntaxin and its functional role in binding to the MUNC18-1 to regulate vesicle docking. This review will summarize our current knowledge of the role of DAPK on cytoskeleton reorganization and report the mechanisms that regulate these changes.

Insights into the functions of the death associated protein kinases from C. elegans and other invertebrates

The death associated protein kinases (DAPK) are a phylogenetically widespread family of calcium-regulated serine/threonine kinases, initially identified from their roles in apoptosis. Subsequent studies, principally in vertebrate cells or models, have elucidated the functions of the DAPK family in autophagy and tumor suppression. Invertebrate genetic model organisms such as Drosophila and C. elegans have revealed additional functions for DAPK and related kinases. In the nematode C. elegans, the sole DAPK family member DAPK-1 positively regulates starvation-induced autophagy. Genetic analysis in C. elegans has revealed that DAPK-1 also acts as a negative regulator of epithelial innate immune responses in the epidermis. This negative regulatory role for DAPK in innate immunity may be analogous to the roles of mammalian DAPK in inflammatory responses.

Regulation of inflammation by DAPK

Death-associated protein kinase (DAPK) is a tumor suppressor and negatively regulates several activation signals. Consistent with its potential anti-inflammatory activity, DAPK promotes the formation of IFN-γ-activated inhibitor of translation (GAIT) complex that suppresses the translation of selected inflammatory genes. DAPK has been found to inhibit tumor necrosis factor-α (TNF-α)- or lipopolysaccharides (LPS)-induced NF-κB activation and pro-inflammatory cytokine expression. Inflammation is always associated with T cell activation, while DAPK attenuates T cell activation by a selective suppression in T cell receptor-triggered NF-κB activation. Recent studies, however, also reveal a contribution of DAPK to pro-inflammatory processes. DAPK is shown to mediate pro-inflammatory signaling downstream of TNF-α, LPS, IL-17, or IL-32. In addition, DAPK is required for the full formation of NLRP3 inflammasome, essential for the generation of IL-1β and IL-18. These results suggest the complicated role of DAPK in the regulation of inflammation that is likely dependent on cell types and environmental cues.

Promoter methylation of DAPK gene may contribute to the pathogenesis of nonsmall cell lung cancer: a meta-analysis

We performed a meta-analysis of cohort studies to determine whether promoter methylation of the death-associated protein kinase (DAPK) gene contributes to the pathogenesis of nonsmall cell lung cancer (NSCLC). A range of electronic databases were searched: MEDLINE (1966 ∼ 2013), the Cochrane Library Database (Issue 12, 2013), EMBASE (1980 ∼ 2013), CINAHL (1982 ∼ 2013), Web of Science (1945 ∼ 2013), and the Chinese Biomedical Database (CBM; 1982 ∼ 2013) without any language restrictions. Meta-analysis was conducted using the STATA 12.0 software. Crude odds ratio (OR) with 95 % confidence interval (95 % CI) was calculated. Our meta-analysis integrated results from 12 clinical cohort studies that met all inclusion criteria with a total of 1,027 NSCLC patients. We observed that the frequency of DAPK gene methylation in cancer tissues were significantly higher than that in the adjacent normal and benign tissues (cancer tissues vs. benign tissues: OR=8.50, 95 % CI=5.88 ∼ 12.28, P<0.001; cancer tissues vs. adjacent tissues: OR=5.95, 95 % CI=4.11 ∼ 8.60, P<0.001; cancer tissues vs. normal tissues: OR=4.75, 95 % CI=3.28 ∼ 6.87, P<0.001; respectively). Subgroup analysis by ethnicity demonstrated that DAPK gene methylation was closely associated with the development and progression of NSCLC among both Asians and Caucasians (all P<0.05). Furthermore, we conducted a subgroup analysis based on sample source and discovered that DAPK gene methylation was implicated in the pathogenesis of NSCLC in both blood and tissue subgroups (all P<0.05). Our results suggest that DAPK promoter methylation may be involved in NSCLC carcinogenesis. Thus, the detection of aberrant DAPK methylation may be helpful in the diagnosis and prognosis of NSCLC.

Identification, sequence analysis, and characterization of serine/threonine protein kinase 17A from Clonorchis sinensis

This is the first report of a novel protein from Clonorchis sinensis (C. sinensis), serine/threonine protein kinase 17A (CsSTK17A), which belongs to a member of the death-associated protein kinase (DAPK) family known to regulate diverse biological processes. The full-length sequence encoding CsSTK17A was isolated from C. sinensis adult cDNA plasmid library. Two transcribed isoforms of the gene were identified from the genome of C. sinensis. CsSTK17A contains a kinase domain at the N-terminus that shares a degree of conservation with the DAPK families. Besides, the catalytic domain contains 11 subdomains conserved among STKs and shares the highest identity with STK from Schistosoma mansoni (55.9%). Three-dimensional structure of CsSTK17A displays the canonical STK fold, including the helix C, P-loop, and the activation loop. We obtained recombinant CsSTK17A (rCsSTK17A) and anti-rCsSTK17A IgG. The rCsSTK17A could be probed by anti-rCsSTK17A rat serum, C. sinensis-infected rat serum and the sera from rats immunized with C. sinensis excretory-secretory products, indicating that it is a circulating antigen possessing a strong immunocompetence. Moreover, quantitative RT-PCR and western blotting analyses revealed that CsSTK17A exhibited the highest mRNA and protein expression level in eggs, followed by metacercariae and adult worms. Intriguingly, in the immunolocalization assay, CsSTK17A was intensively localized to the operculum region of eggs in uterus, as well as the vitelline gland of both adult worm and metacercaria, implying that the protein was associated with the reproduction and development of C. sinensis. Overall, these fundamental studies might contribute to further researches on signaling systems of the parasite.

Serine/threonine kinase 17A is a novel candidate for therapeutic targeting in glioblastoma

STK17A is a relatively uncharacterized member of the death-associated protein family of serine/threonine kinases which have previously been associated with cell death and apoptosis. Our prior work established that STK17A is a novel p53 target gene that is induced by a variety of DNA damaging agents in a p53-dependent manner. In this study we have uncovered an additional, unanticipated role for STK17A as a candidate promoter of cell proliferation and survival in glioblastoma (GBM). Unexpectedly, it was found that STK17A is highly overexpressed in a grade-dependent manner in gliomas compared to normal brain and other cancer cell types with the highest level of expression in GBM. Knockdown of STK17A in GBM cells results in a dramatic alteration in cell shape that is associated with decreased proliferation, clonogenicity, migration, invasion and anchorage independent colony formation. STK17A knockdown also sensitizes GBM cells to genotoxic stress. STK17A overexpression is associated with a significant survival disadvantage among patients with glioma which is independent of age, molecular phenotype, IDH1 mutation, PTEN loss, and alterations in the p53 pathway and partially independent of grade. In summary, we demonstrate that STK17A provides a proliferative and survival advantage to GBM cells and is a potential target to be exploited therapeutically in patients with glioma.

Hepatitis B virus x protein induces autophagy via activating death-associated protein kinase

Hepatitis B virus x protein (HBX), a product of hepatitis B virus (HBV), is a multifunctional protein that regulates viral replication and various cellular functions. Recently, HBX has been shown to induce autophagy; however, the responsible mechanism is not fully known. In this study, we established stable HBX-expressing epithelial Chang cells as the platform to study how HBX induced autophagy. The results showed that the overexpression of HBX resulted in starvation-induced autophagy. HBX-induced autophagy was related to its ability to dephosphorylate/activate death-associated protein kinase (DAPK). The block of DAPK by its siRNA significantly counteracted HBX-mediated autophagy, confirming the positive role of DAPK in this process. HBX also induced Beclin 1, which functions at the downstream of the DAPK-mediated autophagy pathway. Although HBX could activate JNK, a kinase known to participate in autophagy in certain conditions, the change in JNK failed to influence HBX-induced autophagy. In conclusion, HBX induces autophagy via activating DAPK in a pathway related to Beclin 1, but not JNK. This new finding should help us to understand the role of autophagy in HBX-mediated pathogenesis and thus may provide targets for intervening HBX-related disorders.

The many faces of calmodulin in cell proliferation, programmed cell death, autophagy, and cancer

Calmodulin (CaM) is a ubiquitous Ca(2+) receptor protein mediating a large number of signaling processes in all eukaryotic cells. CaM plays a central role in regulating a myriad of cellular functions via interaction with multiple target proteins. This review focuses on the action of CaM and CaM-dependent signaling systems in the control of vertebrate cell proliferation, programmed cell death and autophagy. The significance of CaM and interconnected CaM-regulated systems for the physiology of cancer cells including tumor stem cells, and processes required for tumor progression such as growth, tumor-associated angiogenesis and metastasis are highlighted. Furthermore, the potential targeting of CaM-dependent signaling processes for therapeutic use is discussed.

Estrogen-related genome-based expression profiling study of uterosacral ligaments in women with pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

The aim of the study was to identify the differential expression of estrogen-related genes that may be involved in the menopause and pelvic organ prolapse (POP) using microarray analysis.

METHODS

An age, parity, and menopausal status-matched case-control study with 12 POP patients and 5 non-POP patients was carried out. The study was conducted from January to December 2010 at Yonsei University, Severance Hospital. We examined microarray gene expression profiles in uterosacral ligaments (USLs) from POP and non-POP patients. Total RNA was extracted from USL samples to generate labeled cDNA, which was hybridized to microarrays and analyzed for the expression of 44,049 genes. We identified differentially expressed genes and performed functional clustering. After clustering, we focused on transcriptional response and signal transduction gene clusters, which are associated with estrogen, and then validated the changes of gene expression levels observed with the microarray analysis using quantitative polymerase chain reaction (qPCR).

RESULTS

The data from the microarray analysis using more than a 1.5-fold change with p value <0.05 resulted in 143 upregulated genes and 87 downregulated genes. Of 59 genes identified to be associated with signal transduction and transcription, 4 genes were chosen for qPCR that have been classified to be associated with estrogen. We found that estrogen receptor-related receptor-α (ERRα) was downregulated and that the expression of death-associated protein kinase 2 (DAPK 2), signal-transducing adaptor protein-2 (STAP-2), and interleukin (IL)-15 were upregulated.

CONCLUSIONS

We found four differentially expressed genes by microarray analysis that may account for the way in which changes in estrogen level affect POP pathophysiology.

The therapeutic target Hsp90 and cancer hallmarks

Hsp90 is a major molecular chaperone that is expressed abundantly and plays a pivotal role in assisting correct folding and functionality of its client proteins in cells. The Hsp90 client proteins include a wide variety of signal transducing molecules such as protein kinases and steroid hormone receptors. Cancer is a complex disease, but most types of human cancer share common hallmarks, including self-sufficiency in growth signals, insensitivity to growth-inhibitory mechanism, evasion of programmed cell death, limitless replicative potential, sustained angiogenesis, and tissue invasion and metastasis. A surprisingly large number of Hsp90-client proteins play crucial roles in establishing cancer cell hallmarks. We start the review by describing the structure and function of Hsp90 since conformational changes during the ATPase cycle of Hsp90 are closely related to its function. Many co-chaperones, including Hop, p23, Cdc37, Aha1, and PP5, work together with Hsp90 by modulating the chaperone machinery. Post-translational modifications of Hsp90 and its cochaperones are vital for their function. Many tumor-related Hsp90-client proteins, including signaling kinases, steroid hormone receptors, p53, and telomerase, are described. Hsp90 and its co-chaperones are required for the function of these tumor-promoting client proteins; therefore, inhibition of Hsp90 by specific inhibitors such as geldanamycin and its derivatives attenuates the tumor progression. Hsp90 inhibitors can be potential and effective cancer chemotherapeutic drugs with a unique profile and have been examined in clinical trials. We describe possible mechanisms why Hsp90 inhibitors show selectivity to cancer cells even though Hsp90 is essential also for normal cells. Finally, we discuss the "Hsp90-addiction" of cancer cells, and suggest a role for Hsp90 in tumor evolution.

The therapeutic target Hsp90 and cancer hallmarks

Hsp90 is a major molecular chaperone that is expressed abundantly and plays a pivotal role in assisting correct folding and functionality of its client proteins in cells. The Hsp90 client proteins include a wide variety of signal transducing molecules such as protein kinases and steroid hormone receptors. Cancer is a complex disease, but most types of human cancer share common hallmarks, including self-sufficiency in growth signals, insensitivity to growth-inhibitory mechanism, evasion of programmed cell death, limitless replicative potential, sustained angiogenesis, and tissue invasion and metastasis. A surprisingly large number of Hsp90-client proteins play crucial roles in establishing cancer cell hallmarks. We start the review by describing the structure and function of Hsp90 since conformational changes during the ATPase cycle of Hsp90 are closely related to its function. Many co-chaperones, including Hop, p23, Cdc37, Aha1, and PP5, work together with Hsp90 by modulating the chaperone machinery. Post-translational modifications of Hsp90 and its cochaperones are vital for their function. Many tumor-related Hsp90-client proteins, including signaling kinases, steroid hormone receptors, p53, and telomerase, are described. Hsp90 and its co-chaperones are required for the function of these tumor-promoting client proteins; therefore, inhibition of Hsp90 by specific inhibitors such as geldanamycin and its derivatives attenuates the tumor progression. Hsp90 inhibitors can be potential and effective cancer chemotherapeutic drugs with a unique profile and have been examined in clinical trials. We describe possible mechanisms why Hsp90 inhibitors show selectivity to cancer cells even though Hsp90 is essential also for normal cells. Finally, we discuss the "Hsp90-addiction" of cancer cells, and suggest a role for Hsp90 in tumor evolution.

Stem cells isolated from adipose tissue of obese patients show changes in their transcriptomic profile that indicate loss in stemcellness and increased commitment to an adipocyte-like phenotype

BACKGROUND

The adipose tissue is an endocrine regulator and a risk factor for atherosclerosis and cardiovascular disease when by excessive accumulation induces obesity. Although the adipose tissue is also a reservoir for stem cells (ASC) their function and "stemcellness" has been questioned. Our aim was to investigate the mechanisms by which obesity affects subcutaneous white adipose tissue (WAT) stem cells.

RESULTS

Transcriptomics, in silico analysis, real-time polymerase chain reaction (PCR) and western blots were performed on isolated stem cells from subcutaneous abdominal WAT of morbidly obese patients (ASCmo) and of non-obese individuals (ASCn). ASCmo and ASCn gene expression clustered separately from each other. ASCmo showed downregulation of "stemness" genes and upregulation of adipogenic and inflammatory genes with respect to ASCn. Moreover, the application of bioinformatics and Ingenuity Pathway Analysis (IPA) showed that the transcription factor Smad3 was tentatively affected in obese ASCmo. Validation of this target confirmed a significantly reduced Smad3 nuclear translocation in the isolated ASCmo.

CONCLUSIONS

The transcriptomic profile of the stem cells reservoir in obese subcutaneous WAT is highly modified with significant changes in genes regulating stemcellness, lineage commitment and inflammation. In addition to body mass index, cardiovascular risk factor clustering further affect the ASC transcriptomic profile inducing loss of multipotency and, hence, capacity for tissue repair. In summary, the stem cells in the subcutaneous WAT niche of obese patients are already committed to adipocyte differentiation and show an upregulated inflammatory gene expression associated to their loss of stemcellness.

The tumor suppressor gene DAPK2 is induced by the myeloid transcription factors PU.1 and C/EBPα during granulocytic differentiation but repressed by PML-RARα in APL

DAPK2 is a proapoptotic protein that is mostly expressed in the hematopoietic tissue. A detailed DAPK2 expression analysis in two large AML patient cohorts revealed particularly low DAPK2 mRNA levels in APL. DAPK2 levels were restored in APL patients undergoing ATRA therapy. PML-RARA is the predominant lesion in APL causing transcriptional repression of genes important for neutrophil differentiation. We found binding of PML-RARA and PU.1, a myeloid master regulator, to RARA and PU.1 binding sites in the DAPK2 promoter. Ectopic expression of PML-RARA in non-APL, as well as knocking down PU.1 in APL cells, resulted in a significant reduction of DAPK2 expression. Restoring DAPK2 expression in PU.1 knockdown APL cells partially rescued neutrophil differentiation, thereby identifying DAPK2 as a relevant PU.1 downstream effector. Moreover, low DAPK2 expression is also associated with C/EBPα-mutated AML patients, and we found C/EBPα-dependent regulation of DAPK2 during APL differentiation. In conclusion, we identified first inhibitory mechanisms responsible for the low DAPK2 expression in particular AML subtypes, and the regulation of DAPK2 by two myeloid transcription factors underlines its importance in neutrophil development.

Death-associated protein kinase controls STAT3 activity in intestinal epithelial cells

The TNF-IL-6-STAT3 pathway plays a crucial role in promoting ulcerative colitis-associated carcinoma (UCC). To date, the negative regulation of STAT3 is poorly understood. Interestingly, intestinal epithelial cells of UCC in comparison to ulcerative colitis show high expression levels of anti-inflammatory death-associated protein kinase (DAPK) and low levels of pSTAT3. Accordingly, epithelial DAPK expression was enhanced in STAT3(IEC-KO) mice. To unravel a possible regulatory mechanism, we used an in vitro TNF-treated intestinal epithelial cell model. We identified a new function of DAPK in suppressing TNF-induced STAT3 activation as DAPK siRNA knockdown and treatment with a DAPK inhibitor potentiated STAT3 activation, IL-6 mRNA expression, and secretion. DAPK attenuated STAT3 activity directly by physical interaction shown in three-dimensional structural modeling. This model suggests that DAPK-induced conformational changes in the STAT3 dimer masked its nuclear localization signal. Alternatively, pharmacological inactivation of STAT3 led to an increase in DAPK mRNA and protein levels. Chromatin immunoprecipitation showed that STAT3 restricted DAPK expression by promoter binding, thereby reinforcing its own activation by inducing IL-6. This novel negative regulation principle might balance TNF-induced inflammation and seems to play an important role in the inflammation-associated transformation process as confirmed in an AOM+DSS colon carcinogenesis mouse model. DAPK as a negative regulator of STAT3 emerges as therapeutic option in the treatment of ulcerative colitis and UCC.