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Endothelial cells are the interface between hemodynamic fluid flow and vascular tissue contact. They actively translate physical and chemical stimuli into intracellular signaling cascades which in turn regulate cell function, and endothelial dysfunction leads to inflammation and diseased conditions. For example, atherosclerosis, a chronic vascular disease, favorably develops in regions of disturbed fluid flow and low shear stress. Apoptosis, or programmed cell death, must be properly regulated to maintain homeostasis in the vascular wall. The loss of apoptosis control, as seen in low shear stress regions, is implicated in various diseases such as atherosclerosis and cancer. Death-associated protein kinase (DAPK) is a pro-apoptotic regulator for various cell types that is localized in the cell cytoskeleton and regulates changes in cytoplasm associated with apoptosis. Yet its role in endothelial cells remains unclear. Laminar shear stress inhibits cytokine, oxidative stress, and serum starvation induced endothelial apoptosis, while extended shearing elicit structural changes and cell alignment. We hypothesize that DAPK potentially plays a role in attenuating endothelial apoptosis in response to shear stress. We found that shear stress regulates DAPK expression and apoptotic activity in endothelial cells. In fact, shear stress alone induces DAPK and apoptosis, but has the opposite effect in the presence of apoptotic triggers such as tissue necrosis factor α (TNFα). This review summarizes mechanisms of endothelial mechanotransduction and apoptosis, and explores the potential of DAPK as a novel signaling pathway involved in mediating protective effects of shear stress on the vasculature., (© 2013.)

Dual leucine zipper kinase (DLK), a mitogen-activated protein kinase kinase kinase, controls axon growth, apoptosis and neuron degeneration during neural development, as well as neurodegeneration after various insults to the adult nervous system. Interestingly, recent studies have also highlighted a role of DLK in promoting axon regeneration in diverse model systems. Invertebrates and vertebrates, cold- and warm-blooded animals, as well as central and peripheral mammalian nervous systems all differ in their ability to regenerate injured axons. Here, we discuss how DLK-dependent signalling regulates apparently contradictory functions during neural development and regeneration in different species. In addition, we outline strategies to fine-tune DLK function, either alone or together with other approaches, to promote axon regeneration in the adult mammalian central nervous system.

Background: The majority of alveolar rhabdomyosarcoma (ARMS) are distinguished through the paired box 3-forkhead box protein O1 (PAX3-FOXO1) fusion oncoprotein, being generated by a 2;13 chromosomal translocation. This fusion-positive ARMS is the most clinically difficult type of rhabdomyosarcoma. The present study characterized four genes [gremlin 1 (GREM1), death-associated protein kinase-1 (DAPK1), myogenic differentiation-1 (MYOD1), and hairy/enhancer-of-split related with YRPW motif-1 (HEY1)] as targets of PAX3-FOXO1., Materials and Methods: The expression of the four genes, PAX3-FOXO1, and v-myc myelocytomatosis viral-related oncogene, neuroblastoma-derived (avian) (MYCN) was determined in various ARMS cell models and primary tumors. The roles of PAX3-FOXO1 and MYCN expression were examined., Results: Pulse-chase and cycloheximide experiments suggest that GREM1, DAPK1, and MYOD1 are directly regulated by PAX3-FOXO1. PAX3-FOXO1 appears to indirectly down-regulate HEY1 by up-regulating MYCN. Data reveal that the growth-suppressive activity of high PAX3-FOXO1 expression is closely-associated with up-regulation of the GREM1 and DAPK1 tumor-suppressor genes., Conclusion: This study characterized four downstream targets of PAX3-FOXO1 that contribute to the biological activities of growth suppression and myogenic differentiation.

Curcumin, an active polyphenol extracted from the perennial herb Curcuma longa, controls various molecules involved in tumor cell death. In this study, we found that the tumor suppressor death-associated protein kinase 1 (DAPK1) plays a vital role in the anti-carcinogenic effects of curcumin. We found that curcumin increased DAPK1 expression at the mRNA and protein levels in U251 cells, and that the siRNA-mediated knockdown of DAPK1 attenuated the curcumin-induced inhibition of STAT3 and NF-κB. Moreover, DAPK1 suppression diminished curcumin-induced caspase-3 activation. In addition, we confirmed that DAPK1 was required for a curcumin-induced G2/M cell cycle arrest and apoptosis. Thus, DAPK1 is involved in curcumin-mediated death pathways. Our data suggest novel mechanisms for curcumin in cancer therapy., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Objectives: In resected buccal cancer patients, an unexpected close surgical margin has been observed to correlate with poor clinical outcomes. However, close surgical margin alone does not independently guide post-operative therapies, revealing a clinical debate. Hence, the present study intended to explore epigenetic-based bio-predictors for further stratifying this debating patient population., Materials and Methods: Between 2000 and 2008, we retrospectively recruited 44 resected buccal cancer patients with a close surgical margin of ≤5 mm. All patients had post-operative radiotherapy. Genomic DNA was extracted from tumor-enrich areas that contained cancer cells of >70%. Methylation-specific PCR was performed to detect promoter methylation of four tumor suppressor genes, including RASSF1A, DAPK, IRF8, and SFRP1. Post-irradiation locoregional control was defined as the primary end point., Results: There were 40 males and 4 females, with a median age of 53.5 years (range, 32-82 years). Multivariate analysis identified two independent predictors for locoregional recurrence: very close margin of ≤1 mm (HR: 4.96; 95% CI, 1.63-15.09; P=0.018) and promoter hypermethylation of DAPK (HR: 2.83; 95% CI, 1.05-7.63; P=0.042). The highest risk of locoregional recurrence was observed in patients with both of the two factors (HR, 8.05; 95% CI, 2.56-25.82; P=0.002) when compared with patients with none. Shorter disease-free survival, but not overall survival, was also observed., Conclusion: More aggressive managements should be considered in resected buccal cancer patients with both very close margin and DAPK promoter hypermethylation rather than post-operative observation or radiotherapy alone., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

CCN family protein 2 (CCN2), also known as connective tissue growth factor, is a secreting protein that modulates multiple cellular events. We previously demonstrated the metastasis-suppressive effect of CCN2 in lung cancer cells. In this study, we investigate the role of CCN2 in anoikis, a form of programmed cell death that is critical in suppressing cancer metastasis. CCN2 binds to the epidermal growth factor receptor (EGFR) and triggers ubiquitination by inhibiting the formation of the β-pix/Cbl complex, resulting in the degradation of EGFR. Binding of CCN2 to EGFR suppresses the phosphorylation of c-Src and extracellular signal-regulated kinase but increases the expression of death-associated protein kinase, which leads to anoikis. Overall, our findings provide evidence validating the use of CCN2 as an anti-metastatic therapy in lung cancer patients, and prospect a potential therapeutic synergy between CCN2 and the anti-EGFR antibody for the treatment of lung cancer.

In this study, methylation-specific polymerase chain reaction was used to investigate the role and potential prognostic significance of the methylation status of p16, p15, MGMT and DAPK genes in 32 specimens of follicular lymphoma (FL). Hypermethylation of p15 gene was associated with lower hemoglobin level (P = 0.020) and MGMT/DAPK comethylation with relapsed disease (P = 0.018). Among all patients with FL, there was no significant difference in the overall survival between those with hypermethylated and unmethylated of any examined genes. Therefore, we analyzed methylation in the different groups according to FL International Prognostic Index (FLIPI) and tumor grade. In the high-risk group, patients with hypermethylated p16 gene had significant lower overall survival than those with unmethylated p16 (P = 0.006) and trend toward shorter failure-free survival (P = 0.068). In the same risk group, there was a trend toward longer overall survival for patients with hypermethylated MGMT gene, compared to those with unmethylated MGMT gene (P = 0.066). p15 methylation had impact on shorter overall survival in grade I group of patients (P = 0.013), and DAPK methylation tended to have impact on shorter failure-free survival in the whole examined group (P = 0.079). Our results suggest that promoter methylation of p16 and MGMT genes could have prognostic value when used in combination with the FLIPI and p15 methylation in combination with tumor grade. Concurrent methylation of MGMT and DAPK genes could be the marker of tumor chemoresistance and disease recurrence.

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., (Copyright © 2013 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Background: In the vasculature, misdirected apoptosis in endothelial cells leads to pathological conditions such as inflammation. Along with biochemical and molecular signals, the hemodynamic forces that the cells experience are also important regulators of endothelial functions such as proliferation and apoptosis. Laminar shear stress inhibits apoptosis induced by serum depletion, oxidative stress, and tumor necrosis factor α (TNFα). Death associated protein kinase (DAPK) is a positive regulator of TNFα induced apoptotic pathway. Here we investigate the effect of shear stress on DAPK in endothelial cells on glass or silicone membrane substrate. We have already shown a link between shear stress and DAPK expression and apoptosis in cells on glass. Here we transition our study to endothelial cells on non-glass substrates, such as flexible silicone membrane used for cyclic strain studies., Results: We modified the classic parallel plate flow chamber to accommodate silicone membrane as substrate for cells, and validated the chamber for cell viability in shear stress experiments. We found that adding shear stress significantly suppressed TNFα induced apoptosis in cells; while shearing cells alone also increased apoptosis on either substrate. We also found that shearing cells at 12 dynes/cm2 for 6 hours resulted in increased apoptosis on both substrates. This shear-induced apoptosis correlated with increased caspase 3/7 activities and DAPK expression and activation via dephosphorylation of serine 308., Conclusion: These data suggest that shear stress induced apoptosis in endothelial cells via increased DAPK expression and activation as well as caspase-3/7 activity. Most in vitro shear stress studies utilize the conventional parallel plate flow chamber where cells are cultured on glass, which is much stiffer than what cells encounter in vivo. Other mechanotransduction studies have utilized the flexible silicone membrane as substrate, for example, in cyclic stretch studies. Thus, this study bridges the gap between shear stress studies on cells plated on glass to studies on different stiffness of substrates or mechanical stimulation such as cyclic strain. We continue to explore the mechanotransduction role of DAPK in endothelial apoptosis, by using substrates of physiological stiffness for shear stress studies, and by using silicone substrate in cyclic stretch devices.

Background: Aberrant methylation patterns in CpG island are known to be influential in gene silencing. Histamine plays important physiological roles in the upper gastrointestinal tract and acts via the H2 receptor. We report an investigation into the effect of HRH2 promoter polymorphism (rs2607474 G > A) on the methylation of DAPK and CDH1., Methods: Non cancerous gastric mucosa samples were obtained from 115 subjects with gastric cancer (GC) and 412 non-cancer subjects (non-GC). Methylation status of genes was determined by MSP. The genotyping of rs2607474 was performed by PCR-SSCP., Results: Methylation of DAPK and CDH1 was observed in 296 and 246 subjects, respectively. The frequency of CDH1 methylation in the subjects with GC was significantly lower in cancer lesion than in non cancerous mucosa, whereas that of DAPK methylation was not different. The allelic distribution of rs2607474 was 401GG, 119GA and 7AA. The GG homozygote was associated with a significantly increased risk for methylation of both DAPK and CDH1 (p < 0.0001 and p = 0.0009, respectively). In the non-GC subjects or more than 60 years of age, GG homozygote was more closely associated with both DAPK and CDH1 methylation. However, this genotype did not show an increased risk for the development of methylation of both genes in patients with GC. In H. pylori negative subjects, GG homozygote showed an increased risk for the methylation of both DAPK and CDH1 (p = 0.0074 and p = 0.0016, respectively), whereas this genotype was associated with an increased risk for the development of DAPK methylation in H. pylori positive subjects (p = 0.0018). In addition, in subjects older than 60 years of age, atrophy and metaplasia scores were significantly higher in the GG homozygote (p = 0.011 and p = 0.039, respectively) and a significant correlation was observed between age and atrophy or metaplasia., Conclusions: Our results suggest that rs2607474 GG homozygote confers a significantly increased risk for age- and inflammation-related DAPK and CDH1 methylation.

We previously reported a rare germline variant (c.1-6531) that resulted in allele-specific expression (ASE) of death-associated protein kinase 1 (DAPK1) and predisposition to chronic lymphocytic leukemia (CLL). We investigated a cohort of CLL patients lacking this mutation for the presence of ASE of DAPK1. We developed a novel strategy that combines single-nucleotide primer extension (SNuPE) with MALDI-TOF mass spectrometry, and detected germline DAPK1 ASE in 17 out of 120 (14.2%) CLL patients associated with a trend towards younger age at diagnosis. ASE was absent in 63 healthy controls. Germline cells of CLL patients with ASE showed increased levels of DNA methylation in the promoter region, however, neither genetic nor further epigenetic aberrations could be identified in the DAPK1 5' upstream regulatory region, within distinct exons or in the 3'-UTR. We identified B-lymphoid malignancy related cell line models harboring allelic imbalance and found that allele-specific methylation in DAPK1 is associated with ASE. Our data indicate that ASE at the DAPK1 gene locus is a recurrent event, mediated by epigenetic mechanisms and potentially predisposing to CLL.

The histone deacetylase inhibitor (HDACi) LBH589 has been verified as an effective anticancer agent. The identification and characterization of new targets for LBH589 action would further enhance our understanding of the molecular mechanisms involved in HDACi therapy. The role of the tumor suppressor death-associated protein kinase (DAPK) in LBH589-induced cytotoxicity has not been investigated to date. Stable DAPK knockdown (shRNA) and DAPK overexpressing (DAPK+++) cell lines were generated from HCT116 wildtype colon cancer cells. LBH589 inhibited cell proliferation, reduced the long-term survival, and up-regulated and activated DAPK in colorectal cancer cells. Moreover, LBH589 significantly suppressed the growth of colon tumor xenografts and in accordance with the in vitro studies, increased DAPK levels were detected immunohistochemically. LBH589 induced a DAPK-dependent autophagy as assessed by punctuate accumulation of LC3-II, the formation of acidic vesicular organelles, and degradation of p62 protein. LBH589-induced autophagy seems to be predominantly caused by DAPK protein interactions than by its kinase activity. Caspase inhibitor zVAD increased autophagosome formation, decreased the cleavage of caspase 3 and PARP but didn't rescue the cells from LBH589-induced cell death in crystal violet staining suggesting both caspase-dependent as well as caspase-independent apoptosis pathways. Pre-treatment with the autophagy inhibitor Bafilomycin A1 caused caspase 3-mediated apoptosis in a DAPK-dependent manner. Altogether our data suggest that DAPK induces autophagy in response to HDACi-treatment. In autophagy deficient cells, DAPK plays an essential role in committing cells to HDACi-induced apoptosis.

DAPK (death-associated protein kinase) is a newly recognized member of the mammalian family of ROCO proteins, characterized by common ROC (Ras of complex proteins) and COR (C-terminal of ROC) domains. In the present paper, we review our recent work showing that DAPK is functionally a ROCO protein; its ROC domain binds and hydrolyses GTP. Furthermore, GTP binding regulates DAPK catalytic activity in a novel manner by enhancing autophosphorylation on inhibitory Ser308, thereby promoting the kinase 'off' state. This is a novel mechanism for in cis regulation of kinase activity by the distal ROC domain. The functional similarities between DAPK and the Parkinson's disease-associated protein LRRK2 (leucine-rich repeat protein kinase 2), another member of the ROCO family, are also discussed.

Death-associated protein kinase (DAPK) is a Ca2+/calmodulin-regulated serine/threonine kinase that mediates cell death. Our recent study demonstrated that DAPK3 protein increases in the mesenteric artery from spontaneously hypertensive rats compared with Wistar Kyoto rats. Pathogenesis of hypertension is modulated at least in part by vascular inflammation. We examined whether DAPK3 mediates vascular inflammatory responses and development of hypertension. In rat mesenteric arterial smooth muscle cells, small interfering RNA against DAPK3 inhibited vascular cell adhesion molecule 1 expression and monocyte adhesion induced by tumor necrosis factor-α. DAPK3 small interfering RNA inhibited phosphorylation of c-Jun amino-terminal kinase, p38, and Akt, as well as reactive oxygen species (ROS) production induced by tumor necrosis factor-α. In human umbilical vein endothelial cells, expressions of vascular cell adhesion molecule 1, endothelial selectin, and cyclooxygenase 2, as well as ROS production induced by tumor necrosis factor-α, were inhibited by DAPK inhibitor. In vivo, blood pressure, ROS production, inflammatory molecule expression (vascular cell adhesion molecule 1 and endothelial selectin), and hypertrophy in isolated mesenteric artery were elevated in spontaneously hypertensive rats (10 weeks old), which were prevented by long-term treatment with a DAPK inhibitor (500 µg/kg per day for 6 weeks). In isolated mesenteric artery, the increased angiotensin II-induced contraction and the impaired acetylcholine-induced endothelium-dependent relaxation in spontaneously hypertensive rats were reversed by a DAPK inhibitor. The present results for the first time demonstrated in cultured smooth muscle cells and endothelial cells that DAPK3 mediates tumor necrosis factor-induced inflammatory responses via ROS-dependent mechanisms. It is also suggested that DAPK3 mediates the development of hypertension in spontaneously hypertensive rats likely via ROS-dependent inflammation, hypertrophy, and hypercontractility.

Background: CpG island aberrant methylation is shown to be an important mechanism in gene silencing. The important role of IL-17 in inflammatory response to H. pylori colonization has been indicated. We investigated the influence of IL17A polymorphisms, -197 G > A (rs2275913) and *1249 C > T (rs3748067), on the methylation of DAPK and CDH1., Methods: Gastric mucosal samples were obtained from 401 subjects without malignancies. Methylation status of gene was determined by MSP. The genotyping of IL17A was performed by PCR-SSCP., Results: Methylations of DAPK and CDH1 were seen in 196 and 149 of all 401 subjects, respectively. Overall, *1249 T carrier was associated with a decreased risk for DAPK methylation, whereas -197 G > A was not. In the subjects older than 60 years old, *1249 T carrier was more strongly associated with gene methylation and -197 A carrier tended to be associated with an increased risk for CDH1 methylation. When evaluating by inflammation promoting haplotype (-197 mutant carrier with *1249 homozygote), this haplotype had a more strongly increased risk for both DAPK and CDH1 methylations in comparatively older subjects. Both atrophy and metaplasia scores were significantly increased with age in -197 A carrier or *1249 CC homozygote, whereas were not in -197 GG homozygote or *1249 T carrier. PG I/II ratio was more significantly decreased in -197 A carrier than in GG homozygote under influence of H. pylori infection., Conclusions: In -197 A allele carrier with *1249 CC homozygote, the methylations of both DAPK and CDH1 may be increased gradually, but more rapidly than the other genotypes, with age and altered gastric mucosal structure induced by H. pylori infection.

Aberrant DNA methylation and concomitant transcriptional silencing of death-associated protein kinase 1 (DAPK1) have been demonstrated to be key pathogenic events in chronic lymphocytic leukemia (CLL). In acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), however, the presence of elevated DNA methylation levels has been a matter of continued controversy. Several studies demonstrated highly variable frequencies of DAPK1 promoter methylation by the use of methylation-specific PCR (MSP). By quantitative high-resolution assessment, we demonstrate that aberrant DNA methylation is an extremely rare event in this region. We observed elevated levels just in one out of 246 (0.4%) AML patients, all 42 MDS patients were unmethylated. In conclusion, we present a refined DAPK1 methylation analysis in a large representative patient cohort of AML and MDS patients proofing almost complete absence of elevated DNA methylation. Our results highlight the importance of quantitative measurements for translational research questions on primary patient specimens, particularly., (Copyright © 2011 UICC.)

Metastasis is the major cause of poor prognosis in colorectal cancer (CRC), and increasing evidence supports the contribution of miRNAs to cancer progression. Here, we found that high expression of miR-103 and miR-107 (miR-103/107) was associated with metastasis potential of CRC cell lines and poor prognosis in patients with CRC. We showed that miR-103/107 targeted the known metastasis suppressors death-associated protein kinase (DAPK) and Krüppel-like factor 4 (KLF4) in CRC cells, resulting in increased cell motility and cell-matrix adhesion and decreased cell-cell adhesion and epithelial marker expression. miR-103/107 expression was increased in the presence of hypoxia, thereby potentiating DAPK and KLF4 downregulation and hypoxia-induced motility and invasiveness. In mouse models of CRC, miR-103/107 overexpression potentiated local invasion and liver metastasis effects, which were suppressed by reexpression of DAPK or KLF4. miR-103/107-mediated downregulation of DAPK and KLF4 also enabled the colonization of CRC cells at a metastatic site. Clinically, the signature of a miR-103/107 high, DAPK low, and KLF4 low expression profile correlated with the extent of lymph node and distant metastasis in patients with CRC and served as a prognostic marker for metastasis recurrence and poor survival. Our findings therefore indicate that miR-103/107-mediated repression of DAPK and KLF4 promotes metastasis in CRC, and this regulatory circuit may contribute in part to hypoxia-stimulated tumor metastasis. Strategies that disrupt this regulation might be developed to block CRC metastasis.

Recent studies have shown DAPk as a molecular modulator induced by the second messenger, responsible for controlling cell destiny decisions, but the detailed mechanism mediating the role of DAPk1 during cell death is still not fully understood. In this present report, we attempted to characterize the effects of TNF-α and INF-γ on DAPk1 in human ovarian carcinoma cell lines, OVCAR-3. Both TNF-α and INF-γ significantly induce DAPk1 levels in a time-dependent manner. At the same time, they both arrested cell cycle progression in the G(0)-G(1) and G2/M phase, down-regulated cyclin D1, CDK4 and NF-κB expression, while also up-regulating p27 and p16 expression. Subsequently, the efficacy of the combined treatment with DAPk1 was investigated. In the presence of DAPk1, TNF-α or INF-γ-induced apoptosis was additively increased, while TNF-α or INF-γ-induced NF-κB activity was inhibited. Conversely, TNF-α or INF-γ-dependent NF-κB activity was further enhanced by the inhibition of DAPk1 with its specific siRNA. The activity of NF-κB was dependent on the level of DAPk1, indicating the requirement of DAPk1 for the activation of NF-κB. Low levels of DAPk1 expression were frequently observed in different human patient's tissue and cancer cell lines compared to normal samples. In addition, over-expression of DAPk1 from either TNF-α or INF-γ-treatment cells suppressed the anti-apoptosis protein XIAP as well as COX-2 and ICAM-1, more than control. Taken together, our data findings suggest that DAPk1 can mediate the pro-apoptotic activity of TNF-α and INF-γ via the NF-κB signaling pathways., (Copyright © 2012 Elsevier Inc. All rights reserved.)

A recent study showed that both 5-fluorouracil (5FU)-stimulated apoptosis and Fas-mediated apoptosis in human endometrial adenocarcinoma cells are enhanced by targeted knockdown of endogenous death-associated protein kinase (DAPK) with DAPK small-interfering RNAs. Therefore, we investigated the DAPK survival signals in three 5FU-resistant subclones. DAPK knockdown did not enhance 5FU-stimulated or Fas-mediated apoptosis in any of the three 5FU-resistant subclones, but the subclones acquired resistance to VP16-stimulated cell death that was DAPK-independent. Semi-quantitative flow cytometric analyses showed that there was no differential expression in nine cell surface antigens, including Fas, and six intracellular molecules, including DAPK, that may regulate cell death or survival between the parent cells and 5FU-resistant cells. DAPK mRNA and protein were expressed in the 5FU-resistant subclones at similar levels to the parent cells. These results indicate that acquisition of 5FU-resistance may be accompanied by impairment of common apoptotic signals regulating both DAPK-dependent and DAPK-independent pathways.

The IFN family of cytokines operates a frontline defense against pathogens and neoplastic cells in vivo by controlling the expression of several genes. The death-associated protein kinase 1 (DAPK1), an IFN-γ-induced enzyme, controls cell cycle, apoptosis, autophagy, and tumor metastasis, and its expression is frequently down-regulated in a number of human tumors. Although the biochemical action of DAPK1 is well understood, mechanisms that regulate its expression are unclear. Previously, we have shown that transcription factor C/EBP-β is required for the basal and IFN-γ-induced expression of DAPK1. Here, we show that ATF6, an ER stress-induced transcription factor, interacts with C/EBP-β in an IFN-stimulated manner and is obligatory for Dapk1 expression. IFN-stimulated proteolytic processing of ATF6 and ERK1/2-mediated phosphorylation of C/EBP-β are necessary for these interactions. More importantly, IFN-γ failed to activate autophagic response in cells lacking either ATF6 or C/EBP-β. Consistent with these observations, the Atf6(-/-) mice were highly susceptible to lethal bacterial infections compared with the wild-type mice. These studies not only unravel an IFN signaling pathway that controls cell growth and antibacterial defense, but also expand the role of ATF6 beyond ER stress.

cGMP-dependent protein kinase-I (cGK-I) induces apoptosis in various cancer cell lines. However, the signaling mechanisms involved remain unknown. Using protein microarray technology, we identified a novel cGK substrate, death-associated protein kinase 2 (DAPK2), which is a Ca(2+)/calmodulin-regulated serine/threonine kinase. cGK-I phosphorylated DAPK2 at Ser(299), Ser(367) and Ser(368). Interestingly, a phospho-mimic mutant, DAPK2 S299D, significantly enhanced its kinase activity in the absence of Ca(2+)/calmodulin, while a S367D/S368D mutant did not. Overexpression of DAPK2 S299D also resulted in a twofold increase in apoptosis of human breast cancer MCF-7 cells as compared with wild-type DAPK2. These results suggest that DAPK2 is one of the targets of cGK-I in apoptosis induction., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Death-associated protein kinase (DAPK) has been suggested as a tumor suppressor gene. A high frequency of DAPK promoter hypermethylation has been noted in head and neck cancers and other solid tumors, and it has been used as a tumor marker in molecular detection strategies. Our aim was to examine DAPK promoter hypermethylation in tissue, blood, and salivary rinse samples of oral precancer patients (OPs) and to explore the potential role in oral carcinogenesis. DAPK hypermethylation was analyzed in 77 OPs and 32 oral squamous cell carcinomas (OSCCs) by real-time quantitative methylation-specific PCR (QMSP). We compared the hypermethylation expression between two groups and analyzed the associations with clinicopathologic parameters. The promoter hypermethylation frequency of DAPK in tissue (46.9%) and blood (52.2%) of OSCCs was significantly higher than those in OPs (19.5%, P = 0.004; 22.4%, P = 0.007, respectively). DAPK promoter hypermethylation expression in blood was correlated with its expression in tissue (r = 0.49, P < 0.000). The OP patients who smoked more than 20 years were found 40.0% tissue DAPK hypermethylation in contrast with 10.7% tissue DAPK hypermethylation in the patients whose smoking duration ≦20 years (P = 0.010). Our results suggest that DAPK hypermethylation is an early event in oral carcinogenesis and blood DAPK hypermethylation might be a potential minimal invasive biomarker for OSCC early detection.

Death associated protein kinase (DAPK) is a positive regulator in tumor necrosis factor α (TNFα)-induced apoptotic pathway, and DAPK expression is lost in cancer cells. In the vasculature, misdirected apoptosis in endothelial cells leads to pathological conditions such as inflammation and physiological shear stress is protective against apoptosis. Using bovine aortic endothelial cells, we found that DAPK expression increased, while the auto-inhibitory phosphorylation of serine 308 decreased with shear stress at 12 dynes/cm(2) for 6 h. Quantitative RT-PCR revealed a corresponding increase in DAPK mRNA [P < 0.01]. We found that after 18-h TNFα induction, shearing cells for another 6 h significantly reduced apoptosis based on TUNEL staining [P < 0.05], although cell necrosis was not affected. Under the same conditions, we observed significantly decreased overall DAPK, as well as phospho-serine 308 DAPK [P < 0.05] compared to TNFα treatment alone. Caspase-3 and -7 activities downstream of DAPK were also attenuated. Shearing cells alone resulted in enhanced apoptosis, likely due to increased DAPK activity. Our findings were further supported by DAPK siRNA, which yielded contrary results. We present conclusive evidence for the first time that shear stress of up to 6 h up-regulates DAPK expression and activation. However, in the presence of apoptotic stimuli such as TNFα, shear stress caused decrease in DAPK activity. In fact, long-term shear stress of 24 h significantly reduced overall DAPK expression. Our findings strongly support a novel role for DAPK in mediating effects of shear stress in suppressing cytokine-activated apoptosis., (Copyright © 2011 Wiley Periodicals, Inc.)

Death-associated protein kinase (DAPK) is a novel serine/threonine kinase involved in apoptosis and tumor suppression. Promoter methylation is an important mechanism by which tumor suppressor gene transcription is repressed in cancer cells. Although reduced expression and aberrant methylation of DAPK has been reported in various human cancers, including gastric cancer (GC), the results remain discrepant. We aimed to investigate DAPK mRNA and protein expression in primary GC tissues from Chinese patients and establish a possible relationship between the promoter methylation status and the decreased expression of DAPK. The mRNA level, protein expression, and promoter methylation of DAPK were examined, in the cancer tissues and the corresponding, adjacent nontumor tissues of the 62 GC cases, by RT-PCR, western blotting and methylation-specific PCR, respectively. DAPK mRNA and protein expression in GC tissues was significantly reduced compared with corresponding nontumor tissues (P<0.0001). The methylation frequency of the DAPK promoter in primary GC tissues is significantly higher than in the corresponding nontumor tissues (54.8 vs. 17.7%, P<0.0001). Furthermore, DAPK mRNA expression in tissues containing aberrant promoter methylation was significantly reduced compared with GC tissues with unmethylated DAPK promoter (P<0.0001). Moreover, a significant correlation was demonstrated between the TNM stage and the degree of DAPK promoter methylation in primary GCs (P=0.04). DAPK protein and mRNA expression was reduced in GC tissues of Chinese patients. Diminished expression of DAPK was associated with promoter methylation.

Hypermethylated genomic DNA is a common feature in tumoral tissues, although the prevalence of this modification remains poorly understood. We aimed to determine the frequency of five tumor suppressor (TS) genes in prostate cancer and the correlation between promoter hypermethylation of these genes and low and high grade of prostate carcinomas. A total of 30 prostate tumor specimens were investigated for promoter methylation status of TS hypermethylated in cancer 1 (HIC1), death-associated protein kinase 1 (DAPK1), secreted frizzled-related protein 2 (SFRP2), cyclin-dependent kinase inhibitor 2A (p16), and O-6-methylguanine-DNA methyltransferase (MGMT) genes by using bisulfite modifying method. A high frequency of promoter hypermethylation was found in HIC1 (70.9%), SFRP2 (58.3%), and DAPK1 (33.3%) genes in tumor samples that were examined. The current data show high frequency of hypermethylation changes in HIC1, SFRP2, and DAPK1 genes in prostate carcinomas of high Gleason Score (GS).

Autophagy, a process in which cellular components are engulfed and degraded within double-membrane vesicles termed autophagosomes, has an important role in the response to oxidative damage. Here we identify a novel cascade of phosphorylation events, involving a network of protein and lipid kinases, as crucial components of the signaling pathways that regulate the induction of autophagy under oxidative stress. Our findings show that both the tumor-suppressor death-associated protein kinase (DAPk) and protein kinase D (PKD), which we previously showed to be phosphorylated and consequently activated by DAPk, mediate the induction of autophagy in response to oxidative damage. Furthermore, we map the position of PKD within the autophagic network to Vps34, a lipid kinase whose function is indispensable for autophagy, and demonstrate that PKD is found in the same molecular complex with Vps34. PKD phosphorylates Vps34, leading to activation of Vps34, phosphatydilinositol-3-phosphate (PI(3)P) formation, and autophagosome formation. Consistent with its identification as a novel inducer of the autophagic machinery, we show that PKD is recruited to LC3-positive autophagosomes, where it localizes specifically to the autophagosomal membranes. Taken together, our results describe PKD as a novel Vps34 kinase that functions as an effecter of autophagy under oxidative stress.

Objective: Methylated genes have the potential to provide a new generation of cancer biomarkers. The aim of this study was to investigate: (1) the promoter methylation status of DAPK1, RAR-β2 and MGMT in randomly selected normal cytology of the general female population; (2) the effectiveness of gene methylation in liquid-based cytology to help in the early diagnosis of HSIL; (3) the relationship between HPV infection and gene methylation., Methods: Methylation of DAPK1, RAR-β2 and MGMT in 667 cervical samples with 331 cases of abnormal cytology and 336 randomly selected normal cytology controls was detected by methylation-specific PCR and denaturing high-performance liquid chromatography method (MSP-DHPLC). The methylation frequencies of each gene were compared., Results: Methylation frequencies for MGMT, RAR-β2 and DAPK1 in normal cytology were 36.9, 42.0 and 46.7%, respectively. There was a trend toward increasing methylation frequency for any gene with age (p = 0.0133). Among abnormal cytology, there was a trend toward increasing number of methylation of any gene with severity of cytology grade (r = 0.1178, p = 0.0026). Methylation frequencies for MGMT and RAR-β2 among cytology of each grade were significantly different (χ ( 2 ) = 6.8976, p = 0.0086; χ ( 2 ) = 33.2477, p < 0.0001), and methylation frequencies for RAR-β2 in ASC were significantly higher than that in negative cytology (χ ( 2 ) = 8.7128, p = 0.0032). The relationship between MGMT, RAR-β2 and DAPK1 gene methylation and HPV infection was not found., Conclusion: This study reported methylation frequencies for MGMT, RAR-β2 and DAPK1 in normal cytology of the general female population. The combination of MGMT methylation, cytology and HPV infection is preferable for early detection of CIN2+ in cytology samples. There was no relationship between MGMT, RAR-β2 and DAPK1 gene methylation and HPV infection.

Pyruvate kinase M2 (PKM2) may occur in both a tetrameric and a dimeric form. When the majority of PKM2 molecules are in the highly active tetrameric conformation, glucose is primarily degraded to pyruvate and lactate with the regeneration of energy. A tumor suppressor protein, death-associated protein kinase (DAPK), interacts with PKM2 protein and stabilizes PKM2 in its active tetrameric form in normal proliferating cells. However, DAPK is widely inactivated in cancer cells, leading to the loss of the active conformation of PKM2. This may render PKM2 sensitive to cellular oxidants, switching the enzyme into its inactive dimeric form. Consequently, inhibition of PKM2 after oxidative stress contributes optimal tumor growth and allows cancer cells to withstand oxidative stress.

Anti-EGFR therapy is among the most promising molecular targeted therapies against cancer developed in the past decade. However, drug resistance eventually arises in most, if not all, treated patients. Emerging evidence has linked epigenetic changes, such as DNA methylation at CpG islands, to the development of resistance to multiple anticancer drugs. In addition, genes that are differentially methylated have increasingly been appreciated as a source of clinically relevant biomarker candidates. To identify genes that are specifically methylated during the evolution of resistance to anti-EGFR therapeutic agents, we performed a methylation-specific array containing a panel of 56 genes that are commonly known to be regulated through promoter methylation in two parental non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC) cell lines and their resistant derivatives to either erlotinib or cetuximab. We found that death-associated protein kinase (DAPK) was hypermethylated in drug-resistant derivatives generated from both parental cell lines. Restoration of DAPK into the resistant NSCLC cells by stable transfection re-sensitized the cells to both erlotinib and cetuximab. Conversely, siRNA-mediated knockdown of DAPK induced resistance in the parental sensitive cells. These results demonstrate that DAPK plays important roles in both cetuximab and erlotinib resistance, and that gene silencing through promoter methylation is one of the key mechanisms of developed resistance to anti-EGFR therapeutic agents. In conclusion, DAPK could be a novel target to overcome resistance to anti-EGFR agents to improve the therapeutic benefit, and further evaluation of DAPK methylation as a potential biomarker of drug response is needed.

SB203580 is a well-known inhibitor of p38 mitogen-activated protein kinase (MAPK). However, it can suppress cell proliferation in a p38 MAPK independent manner. The inhibitory mechanism remains unknown. Here, we showed that SB203580 induced autophagy in human hepatocellular carcinoma (HCC) cells. SB203580 increased GFP-LC3-positive cells with GFP-LC3 dots, induced accumulation of autophagosomes, and elevated the levels of microtubule-associated protein light chain 3 and Beclin 1. It stimulated the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and p53, but inhibited the phosphorylation of death-associated protein kinase (DAPK). Inhibition of AMPK, p53, or DAPK attenuated SB203580-induced autophagy. AMPK activation appeared to predate the DAPK signal. The activation of both AMPK and DAPK prompted the phosphorylation of p53 and enhanced Beclin 1 expression. Neither the downregulation of p38 MAPK by its siRNA or chemical inhibitor nor the upregulation of p38 MAPK by p38 MAPK DNA transfection affected B203580-induced autophagy. Collectively, the findings demonstrate a novel function of SB203580 to induce autophagy via activating AMPK and DAPK but independent of p38 MAPK. The induction of autophagy can thus account for the antiproliferative effect of SB203580 in HCC cells.

Objective: Genetic factors are thought to be one of the causes of individual variability in the adverse reactions observed in cancer patients who received gemcitabine therapy. However, genetic factors determining the risk of adverse reactions of gemcitabine are not fully understood., Patients and Methods: To identify a genetic factor(s) determining the risk of gemcitabine-induced leukopenia/neutropenia, we conducted a genome-wide association study, by genotyping over 610 000 single nucleotide polymorphisms (SNPs), and a replication study in a total of 174 patients, including 54 patients with at least grade 3 leukopenia/neutropenia and 120 patients without any toxicities., Results: We identified four loci possibly associated with gemcitabine-induced leukopenia/neutropenia [rs11141915 in DAPK1 on chromosome 9q21, combined P=1.27×10, odds ratio (OR)=4.10; rs1901440 on chromosome 2q12, combined P=3.11×10, OR=34.00; rs12046844 in PDE4B on chromosome 1p31, combined P=4.56×10, OR=4.13; rs11719165 on chromosome 3q29, combined P=5.98×10, OR=2.60]. When we examined the combined effects of these four SNPs, by classifying patients into four groups on the basis of the total number of risk genotypes of these four SNPs, significantly higher risks of gemcitabine-induced leukopenia/neutropenia were observed in the patients having two and three risk genotypes (P=6.25×10, OR=11.97 and P=4.13×10, OR=50.00, respectively) relative to patients with zero or one risk genotype., Conclusion: We identified four novel SNPs associated with gemcitabine-induced severe leukopenia/neutropenia. These SNPs might be applicable in predicting the risk of hematological toxicity in patients receiving gemcitabine therapy.

Epigenetic mechanisms of histone acetylation/deacetylation play an important role in the regulation of gene expression associated with the cell cycle and apoptosis. Recently, sodium butyrate, a histone deacetylase (HDAC) inhibitor, has been shown to exhibit anticancer effects via differentiation and apoptosis of cancer cells. Sodium butyrate may be a potential anticancer chemotherapeutic drug; however, the precise mechanism underlying the anticancer effects of sodium butyrate has not been clearly elucidated. In the present study, we investigated the role of death-associated protein kinase (DAPK) on the apoptosis of human gastric cancer cells induced by sodium butyrate. We observed that sodium butyrate induced apoptosis in human gastric cancer cells. Treatment with the HDAC inhibitor sodium butyrate increased the expression of caspase-3 and DAPK1/2 genes but decreased the expression of Bcl-2 in human gastric cancer cells. The expression of DAPK3, p53 and p21 were not altered by sodium butyrate treatment. Analysis of the general expression patterns revealed that sodium butyrate increased the expression of DAPK1/2 but decreased the expression of FAK and induced changes in the proliferation of apoptosis-related genes in human gastric cancer cells. These data suggest that DAPK expression prompts apoptosis by reducing the FAK protein level in sodium butyrate-induced apoptosis of human gastric cancer cells.

Aberrant promoter hypermethylation of cancer associated genes occur frequently during carcinogenesis and may serve as a cancer biomarker. The aim of this study was to investigate the occurrence and relevance of promoter methylation of the tumor suppressor DAPK-1, APAF-1 () and SPARC in relation to different pathological stages and histological grades of tumor progression that might act as possible independent prognostic factor in the susceptibility towards renal cell carcinoma (RCC) in North Indian population. Three tumor suppressor gene promoters namely APAF-1, DAPK-1 and SPARC were assessed by methylation-specific PCR (MS-PCR) in 196 primarily resected renal cell tumors paired with the corresponding normal tissue samples. After genomic DNA isolation and sodium bisulfite modification, methylation levels were determined and correlated with standard clinicopathological parameters, pathological stage and Fuhrman nuclear grade of RCC. Significant differences in methylation frequency among the four subtypes of renal tumors were found for APAF-1 (p < 0.001), DAPK-1 (p < 0.001) and SPARC (p = 0.182), when compared with the corresponding normal tissue. Male subjects showed stronger association of methylation frequency of all the three genes with RCC than the female subjects. Additionally, higher frequency of APAF-1, DAPK-1 and SPARC promoter methylation were directly correlated with higher tumor stage (p (trend) < 0.001). Higher frequency of promoter methylation of APAF-1 and SPARC were also associated with higher nuclear grade (p < 0.001 and p = 0.036, respectively). This gene panel might contribute to a more optimal diagnostic coverage and information, improving preoperative assessment and therapeutic decision-making in patients harboring suspicious renal masses.

Objective: The purpose of this study was to discuss our investigation of the hypermethylation of promoter regions of tumor suppressor genes, such as death-associated protein kinase (DAPK) and p16, in vulvar lichen sclerosus (LS), in comparison with a control group., Materials and Methods: Promoter hypermethylation of DAPK and p16 was investigated using 24 vulvar biopsies of patients with LS who had received no previous treatment. The control group was composed of 15 patients with no vulvar disease. The DNA of subjects was treated with sodium bisulphate, and the genes under study were subjected to methylation-specific polymerase chain reaction. The resulting polymerase chain reaction products were amplified and analyzed using a 10% polyacrylamide gel., Results: The mean age of the patients with LS was 57 years (the majority were postmenopausal). In the control group, the mean age of the patients was 50 years (p = .151). Methylation of the promoter region of DAPK was found in 4 (17%) of the 23 patients analyzed, and p16 promoter region methylation was found in 8 patients (35%). Two cases of methylation of the DAPK gene were also found to be methylated for the p16 gene. In the control group, no methylation was found in the patients analyzed for the DAPK gene and methylation was found in 3 (21%) of the 14 patients analyzed for the p16 gene (p = .190 and p = .316, respectively)., Conclusions: Methylation of the DAPK and p16 genes, although not sufficient to dictate prognosis of the disease, should not be underestimated because it may form part of a process of genetic and epigenetic alterations that in the future could become relevant to malignant transformation.

Background: Intestinal edema development after trauma resuscitation inhibits intestinal motility which results in ileus, preventing enteral feeding and compromising patient outcome. We have shown previously that decreased intestinal motility is associated with decreased smooth muscle myosin light chain (MLC) phosphorylation. The purpose of the present study was to investigate the mechanism of edema-induced decreases in MLC in a rodent model of intestinal edema., Methods: Intestinal edema was induced by a combination of resuscitation fluid administration and mesenteric venous hypertension. Sham operated animals served as controls. Contractile activity and alterations in the regulation of MLC including the regulation of MLC kinase (MLCK) and MLC phosphatase (MLCP) were measured., Key Results: Contraction amplitude and basal tone were significantly decreased in edematous intestinal smooth muscle compared with non-edematous tissue. Calcium sensitivity was also decreased in edematous tissue compared with non-edematous intestinal smooth muscle. Although inhibition of MLCK decreased contractile activity significantly less in edematous tissue compared with non-edematous tissue, MLCK activity in tissue lysates was not significantly different. Phosphorylation of MYPT was significantly lower in edematous tissue compared with non-edematous tissue. In addition, activities of both rho kinase and zipper-interacting kinase were significantly lower in edematous tissue., Conclusions & Inferences: We conclude from these data that interstitial intestinal edema inhibits MLC phosphorylation predominantly by decreasing inhibitory phosphorylation of the MLC targeting subunit (MYPT1) of MLC phosphatase via decreased ROCK and ZIPK activities, resulting in more MLC phosphatase activity., (© 2012 Blackwell Publishing Ltd.)

Death-associated protein kinase (DAPk) is a tumor suppressor thought to inhibit cancer by promoting apoptosis and autophagy. Because cancer progression is linked to inflammation, we investigated the in vivo functions of DAPk in lung responses to various acute and chronic inflammatory stimuli. Lungs of DAPk knockout (KO) mice secreted higher concentrations of IL-6 and keratinocyte chemoattractant (or chemokine [C-X-C motif] ligand 1) in response to transient intranasal administrations of the Toll-like receptor-4 (TLR4) agonist LPS. In addition, DAPk-null macrophages and neutrophils were hyperresponsive to ex vivo stimulation with LPS. DAPk-null neutrophils were also hyperresponsive to activation via Fc receptor and Toll-like receptor-3, indicating that the suppressive functions of this kinase are not restricted to TLR4 pathways. Even after the reconstitution of DAPk-null lungs with DAPk-expressing leukocytes by transplanting wild-type (WT) bone marrow into lethally irradiated DAPk KO mice, the chimeric mice remained hypersensitive to both acute and chronic LPS challenges, as well as to tobacco smoke exposure. DAPk-null lungs reconstituted with WT leukocytes exhibited elevated neutrophil content and augmented cytokine secretion in the bronchoalveolar space, as well as enhanced epithelial cell injury in response to both acute and chronic inflammatory conditions. These results suggest that DAPk attenuates a variety of inflammatory responses, both in lung leukocytes and in lung epithelial cells. The DAPk-mediated suppression of lung inflammation and airway injury may contribute to the tumor-suppressor functions of this kinase in epithelial carcinogenesis.

Objective: To assess the correlation of promoter methylation of DAPK1, RAR-β and MGMT with cervical lesions from cytology to histology, and to reveal the clinical value of DNA methylation in diagnosis of cervical intraepithelial neoplasia (CIN)., Methods: A total of 103 random-selected cervical samples were collected from residual liquid-based cytology specimens after clinical use in cytopathological diagnosis in outpatient clinic of obstetrics and gynecology, Peking Union Medical Collage Hospital from March 2010 to October 2010. Informed consent was obtained from each woman before the initiation of the study. The methylation sensitive-high resolution melt (MS-HRM) assay was used to evaluate promoter methylation of three genes (DAPK1, RAR-β and MGMT) in 103 biopsy-confirmed liquid-based cervical cytology samples. Methylation levels and high-risk HPV DNA loading (HCII values) were analyzed in relation to both cytological and histological diagnosis., Results: The methylation level of all three genes showed significant difference among the different cytological groups (P = 0.000, 0.011 and 0.002, respectively). The methylation level of DAPK1 and RAR-β showed significant difference among the different histological groups (P = 0.000 and 0.021), while there was no significant difference for MGMT. DAPK1 methylation levels was 1.47% in the CINII/high-grade precancerous lesions group, and 20.98% in the normal/CINI groups (P = 0.000), but there was no significant difference between CINII/high-grade precancerous lesions and normal/CINI groups for RAR-β and MGMT. The combination of DAPK1/HR-HPV loading showed a sensitivity of 0.825 and an area under the receiver operating characteristic curve (ROC) curve (AUC) of 0.695 as diagnostic methods for detecting CINII/high-grade precancerous lesions., Conclusions: DNA methylation such as DAPK1 and RAR-β, in combination with HR-HPV detection, may serve as biomarkers to detect CINII/high-grade precancerous lesions. Detection of methylated DNA from liquid-based cervical cytology specimens is technically feasible with the MS-HRM assay.

Death-associated protein kinase (DAPk), a multi-domain serine/threonine kinase, regulates numerous cell death mechanisms and harbors tumor suppressor functions. In this study, we report that DAPk directly binds and functionally activates pyruvate kinase M2 (PKM2), a key glycolytic enzyme, which contributes to the regulation of cancer cell metabolism. PKM2 was identified as a novel binding partner of DAPk by a yeast two-hybrid screen. This interaction was validated in vitro by enzyme-linked immunosorbent assay using purified proteins and in vivo by co-immunoprecipitation of the two endogenous proteins from cells. In vitro interaction with full-length DAPk resulted in a significant increase in the activity of PKM2. Conversely, a fragment of DAPk harboring only the functional kinase domain (KD) could neither bind PKM2 in cells nor activate it in vitro. Indeed, DAPk failed to phosphorylate PKM2. Notably, transfection of cells, with a truncated DAPk lacking the KD, elevated endogenous PKM2 activity, suggesting that PKM2 activation by DAPk occurs independently of its kinase activity. DAPk-transfected cells displayed changes in glycolytic activity, as reflected by elevated lactate production, whereas glucose uptake remained unaltered. A mild reduction in cell proliferation was detected as well in these transfected cells. Altogether, this work identifies a new role for DAPk as a metabolic regulator, suggesting the concept of direct interactions between a tumor suppressor and a key glycolytic enzyme to limit cell growth. Moreover, the work documents a unique function of DAPk that is independent of its catalytic activity and a novel mechanism to activate PKM2 by protein-protein interaction.

Purpose: Death-associated protein kinase 1 (DAPK1), a tumor suppressor, is a rate-limiting effector in an endoplasmic reticulum (ER) stress-dependent apoptotic pathway. Its expression is epigenetically suppressed in several tumors. A mechanistic basis for epigenetic/transcriptional repression of DAPK1 was investigated in certain forms of acute myeloid leukemia (AML) with poor prognosis, which lacked ER stress-induced apoptosis., Experimental Design: Heterogeneous primary AMLs were screened to identify a subgroup with Flt3ITD in which repression of DAPK1, among NF-κB-and c-Jun-responsive genes, was studied. RNA interference knockdown studies were carried out in an Flt3ITD(+) cell line, MV-4-11, to establish genetic epistasis in the pathway Flt3ITD-TAK1-DAPK1 repression, and chromatin immunoprecipitations were carried out to identify proximate effector proteins, including TAK1-activated p52NF-κB, at the DAPK1 locus., Results: AMLs characterized by normal karyotype with Flt3ITD were found to have 10- to 100-fold lower DAPK1 transcripts normalized to the expression of c-Jun, a transcriptional activator of DAPK1, as compared with a heterogeneous cytogenetic category. In addition, Meis1, a c-Jun-responsive adverse AML prognostic gene signature was measured as control. These Flt3ITD(+) AMLs overexpress relB, a transcriptional repressor, which forms active heterodimers with p52NF-κB. Chromatin immunoprecipitation assays identified p52NF-κB binding to the DAPK1 promoter together with histone deacetylase 2 (HDAC2) and HDAC6 in the Flt3ITD(+) human AML cell line MV-4-11. Knockdown of p52NF-κB or its upstream regulator, NF-κB-inducing kinase (NIK), de-repressed DAPK1. DAPK1-repressed primary Flt3ITD(+) AMLs had selective nuclear activation of p52NF-κB., Conclusions: Flt3ITD promotes a noncanonical pathway via TAK1 and p52NF-κB to suppress DAPK1 in association with HDACs, which explains DAPK1 repression in Flt3ITD(+) AML., (©2011 AACR.)

Apoptosis is correlated with various forms of dementia. Death-associated protein kinase 1 (DAPK1) plays an important role in neuronal apoptosis and could influence the pathology of late-onset Alzheimer's disease (LOAD) and frontotemporal dementia (FTD). It has been reported that two common polymorphisms (rs4878104 and rs4877365) are associated with LOAD, thus we examined the genotype and allele distributions of the above polymorphisms in 681 Italian subjects, including patients with LOAD and FTD. We showed a positive association between rs4878104 and FTD, suggesting a possible implication of the DAPK1 genetic variant in the susceptibility to FTD.

Objective: To investigate the methylation levels of death-associated protein kinase (DAPK) in Uyghur female patients with different cervical lesions in Xinjiang, and to discuss the relationship of the expression and significance of DAPK in normal cervix, chronic cervicitis, cervical intraepithelial neoplasia (CINI, CIN II/III) and invasive cervical squamous cell carcinoma., Methods: 30 cases of normal cervix and chronic cervicitis, 30 cases of CINI, 30 cases of CINII/III and 30 cases of cervical squamous cell carcinoma were tested by methylation specific PCR (MSP). Expressions of DAPK in 30 cases of normal cervix and chronic cervicitis, 30 cases of CINI, 30 cases of CINII/III and 30 cases of cervical squamous cell carcinoma were assayed using immunohistochemical SP staining., Results: The methylation rate of DAPK gene in normal cervix and chronic cervicitis was 3.33%, 10% in cervical intraepithelial neoplasia CINI, 36.7% in CINII/III, and 63.3% in invasive cervical squamous cell carcinoma. The methylation rate of DAPK in the SCC group was significantly higher than that in the other groups (P < 0.05). Aberrant promoter methylation of the DAPK gene was positively correlated with the degree of cervical lesions. The positive rate of DAPK protein in normal cervix and chronic cervicitis was 93.3%, 83.3% in cervical intraepithelial neoplasia CINI, 60.0% in CINII/III, and 33.3% in invasive cervical squamous cell carcinoma. The expression of DAPK in the SCC group was significantly lower than that in the other groups (P < 0.05). The positive rate of DAPK protein was negatively correlated with the degree of cervical lesions (r(s) = -0.603, P < 0.001)., Conclusions: Methylation of DAPK is involved in the cervical carcinogenesis and DAPK gene promoter methylation occurs in the early development of cervical cancer in Uyghur women in Xinjiang. Detection of DAPK gene methylation may provide a basis for use in early detection of cervical cancer. DAPK protein expression is decreasing even disappears along with the progression of cervical lesions.

Objective: To explore the amplification and expression status of DAPK1 and CD147 in esophageal squamous cell carcinoma (ESCC) and their relationship with the prognosis of ESCC., Methods: Immunohistochemical staining and RT-PCR were used to detect the expression and amplification of DAPK1 and CD147 in esophageal squamous carcinoma tissue and normal esophageal mucosa. Statistical analysis of the clinocopathological data was performed with SPSS 11.5 software package., Results: The positive rates of expression of DAPK1 protein and CD147 protein in the specimens of esophageal carcinoma were 31.3% and 58.5%, and in normal esophageal mucosa 57.5% and 25.0%, respectively, with a statistically significant difference (P < 0.001). The expressions of DAPK1 and CD147 were significant correlated with invasion depth, lymph node metastasis, TNM stage and the degree of cancer differentiation. (P < 0.05). The negative expression of DAPK1 and positive expression of CD147 indicated a poor prognosis. In 52 ESCC cases, the expression of DAPK1 in cancer tissues was 0.236 ± 0.049, and 0.395 ± 0.058 in normal esophageal mucosa, while that of CD147 mRNA expression was 0.942 ± 0.204 and 0.821 ± 171, respectively, statistically both with a very significant difference (P < 0.01). There was a higher expression level of DAPK1 mRNA in the cancer tissue in patients with no lymph node metastasis, well differentiation, and earlier pathological stage, and a higher expression level of CD147 mRNA in the cancer tissues in patients with lymph node metastasis, poor differentiation, and later pathological stage., Conclusions: The expression of DAPK1 and CD147 proteins is closely correlated with the clinicopathological characteristics of ESCC. The genes DAPK1 and CD147 may participate in the metastasis and apoptosis of ESCC. The expression of DAPK1 and CD147 may be used as important prognostic predictors in ESCC.

We have studied the interactions between calmodulin (CaM) and three target peptides from the death-associated protein kinase (DAPK) protein family using both experimental and modeling methods, aimed at determining the details of the underlying biological regulation mechanisms. Experimentally, calorimetric binding free energies were determined for the complexes of CaM with peptides representing the DAPK2 wild-type and S308D mutant, as well as DAPK1. The observed affinity of CaM was very similar for all three studied peptides. The DAPK2 and DAPK1 peptides differ significantly in sequence and total charge, while the DAPK2 S308D mutant is designed to model the effects of DAPK2 Ser308 phosphorylation. The crystal structure of the CaM-DAPK2 S308D mutant peptide is also reported. The structures of CaM-DAPK peptide complexes present a mode of CaM-kinase interaction, in which bulky hydrophobic residues at positions 10 and 14 are both bound to the same hydrophobic cleft. To explain the microscopic effects underlying these interactions, we performed free energy calculations based on the approximate MM-PBSA approach. For these highly charged systems, standard MM-PBSA calculations did not yield satisfactory results. We proposed a rational modification of the approach which led to reasonable predictions of binding free energies. All three complexes are strongly stabilized by two effects: electrostatic interactions and buried surface area. The strong favorable interactions are to a large part compensated by unfavorable entropic terms, in which vibrational entropy is the largest contributor. The electrostatic component of the binding free energy followed the trend of the overall peptide charge, with strongest interactions for DAPK1 and weakest for the DAPK2 mutant. The electrostatics was dominated by interactions of the positively charged residues of the peptide with the negatively charged residues of CaM. The nonpolar binding free energy was comparable for all three peptides, the largest contribution coming from the Trp305. About two-thirds of the buried surface area corresponds to nonpolar residues, showing that hydrophobic interactions play an important role in these CaM-peptide complexes. The simulation results agree with the experimental data in predicting a small effect of the S308D mutation on CaM interactions with DAPK2, suggesting that this mutation is not a good model for the S308 phosphorylation.

The ROCO proteins are a family of large, multidomain proteins characterised by the presence of a Ras of complex proteins (ROC) domain followed by a COR, or C-terminal of ROC, domain. It has previously been shown that the ROC domain of the human ROCO protein Leucine Rich Repeat Kinase 2 (LRRK2) controls its kinase activity. Here, the ability of the ROC domain of another human ROCO protein, Death Associated Protein Kinase 1 (DAPK1), to bind GTP and control its kinase activity has been evaluated. In contrast to LRRK2, loss of GTP binding by DAPK1 does not result in loss of kinase activity, instead acting to modulate this activity. These data highlight the ROC domain of DAPK1 as a target for modifiers of this proteins function, and casts light on the role of ROC domains as intramolecular regulators in complex proteins with implications for a broad range of human diseases.

Background: Azacytidine (Aza) was the first demethylation agent identified that may inhibit DNA methyltransferases and reverse DNA hypermethylation, restoring the expression of silenced tumor suppressor genes in patients with myelodysplastic syndromes (MDS). It is unclear whether azacytidine can alter the proliferative and apoptotic changes in myeloid leukemia cells, and methylation changes induced by this drug have remained poorly characterized in therapy-related models., Methods: The proliferation rate of azacytidine on HL60 cells was determined by the MTT protocol. Methylation-specific PCR (MSP) and RT-PCR were used respectively to detect gene methylation status changes and expression levels of p16, Death associated protein kinase (DAPK) and O(6)-methylguanine-DNA methyltransferase (MGMT) before and after treatment with azacytidine., Results: Azacytidine inhibited HL60 cell proliferation and showed a time- and dose-dependent effect. MSP showed hypermethylated p16, DAPK, and MGMT genes before azacytidine treatment. Complete demethylation was seen in p16 and DAPK genes and partial demethylation in the MGMT gene after co-culture with azacytidine. The expression level of p16, DAPK and MGMT genes in HL60 cells was up-regulated after treatment with azacytidine., Conclusions: The CpG islands of p16, DAPK and MGMT genes are hypermethylated in HL60 cells. Azacytidine inhibits proliferation of leukemic cells by hypomethylation of p16, DAPK and MGMT genes.

We studied the localization of myosin-activating protein kinases in cardiomyocytes obtained from fetal human heart at 8-9 weeks gestation. It was found that at this developmental stage, smooth muscle/nonmuscle myosin light chain kinase (MLCK, 108 kDa) and its high-molecular weight isoform (MLCK, 210 kDa), skeletal MLCK and death-associated protein kinase (DAPK) are co-localized with nonmuscle myosin IIB in the premyofibrils. The data obtained suggest that cardiac nonmuscle myosin at 8-9 weeks gestation may serve as the substrate of the studied myosin-activating protein kinases that are likely to cooperatively regulate the formation of myofibrils. We revealed high-molecular weight isoform of smooth muscle/nonmuscle kinase MLCK-210 in developing human heart and determined the ratios of MLCK-108 and MLCK-210 at different gestational stages. In this case, the approximate time period of changes in these isoforms ratio was revealed (between 8-9 and 13 weeks), that can be associated with functional changes in the developing myocardium.

Grifolin, a secondary metabolite isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens, has been shown to induce G1 phase cell-cycle arrest in tumor cells in previous studies of our group. However, the mechanisms of action are not completely understood. Our group further demonstrated that grifolin upregulates death-associated protein kinase 1 (DAPK1) in nasopharyngeal carcinoma cells (NPCs). Here, we found that grifolin induced dephosphorylation of DAPK1 (Ser308) to activate DAPK1 and subsequent phosphorylation of its potential downstream effector p21 (Thr145) in nasopharyngeal carcinoma cell CNE1. Inhibition of DAPK1 by introducing siRNA targeting DAPK1 reversed the grifolin- induced phosphorylation of p21. Furthermore, we confirmed that grifolin increased the half-life of p21 and promoted its stability. Flow cytometry analysis demonstrated that DAPK1 was involved in grifolin-induced G1 phase arrest in CNE1 cells. The similar effects induced by grifolin and mechanism beneath were identified in another nasopharyngeal carcinoma cell HONE1. In addition, we observed that grifolin promoted the protein-protein interaction of DAPK1 and ERK1/2 to prevent ERK1/2 nucleolus translocation. Our findings indicate that DAPK1 plays a crucial role in the induction of cell-cycle arrest at G1 phase by grifolin. Grifolin might represent a promising candidate in the prevention and intervention of cancer by targeting DAPK1 signaling to induce cell cycle G1 phase arrest., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Zipper-interacting protein kinase (ZIPK) has been implicated in Ca(2+)-independent smooth muscle contraction, although its specific role is unknown. The addition of ZIPK to demembranated rat caudal arterial strips induced an increase in force, which correlated with increases in LC(20) and MYPT1 phosphorylation. However, because of the number of kinases capable of phosphorylating LC(20) and MYPT1, it has proven difficult to identify the mechanism underlying ZIPK action. Therefore, we set out to identify bona fide ZIPK substrates using a chemical genetics method that takes advantage of ATP analogs with bulky substituents at the N(6) position and an engineered ZIPK capable of utilizing such substrates. (32)P-Labeled 6-phenyl-ATP and ZIPK-L93G mutant protein were added to permeabilized rat caudal arterial strips, and substrate proteins were detected by autoradiography following SDS-PAGE. Mass spectrometry identified LC(20) as a direct target of ZIPK in situ for the first time. Tissues were also exposed to 6-phenyl-ATP and ZIPK-L93G in the absence of endogenous ATP, and putative ZIPK substrates were identified by Western blotting. LC(20) was thereby confirmed as a direct target of ZIPK; however, no phosphorylation of MYPT1 was detected. We conclude that ZIPK is involved in the regulation of smooth muscle contraction through direct phosphorylation of LC(20).

Background: The benefit of tissue microarray (TMA) is its capability to analyse large numbers of tissue samples in a uniform fashion. This study was designed to evaluate the capability of TMA for analyzing the status of death-associated protein kinase 1 (DAPK1) in breast cancer patient and to explore its potential in the management of breast cancer., Patients and Methods: Over a 60-month period, tissue specimens of 99 patients with primary invasive breast cancer were selected. Tissue microarray (TMA) was applied to detect the DAPK1 expression. The data for the other clinicopathologic variables, including age, histological grading, estrogen receptor status and TNM staging were also recorded., Results: Tumor in 11 patients (11.1%) scored 1 for DAPK1 expression, 55 patients (55.6%) scored 2 and 33 (33.3%) scored 3. We found no obvious link between DAPK1 expression and age, histologic grading, primary tumor staging, lymph node status, estrogen receptor and TNM stage. TNM staging was found to be significantly linked to the overall five-year survival rate through multivariate analysis., Conclusion: DAPK1 expression did not show any meaningful value in predicting outcome for patients with breast cancer.