Gene Summary

Gene:MAP3K5; mitogen-activated protein kinase kinase kinase 5
Aliases: ASK1, MEKK5, MAPKKK5
Summary:Mitogen-activated protein kinase (MAPK) signaling cascades include MAPK or extracellular signal-regulated kinase (ERK), MAPK kinase (MKK or MEK), and MAPK kinase kinase (MAPKKK or MEKK). MAPKK kinase/MEKK phosphorylates and activates its downstream protein kinase, MAPK kinase/MEK, which in turn activates MAPK. The kinases of these signaling cascades are highly conserved, and homologs exist in yeast, Drosophila, and mammalian cells. MAPKKK5 contains 1,374 amino acids with all 11 kinase subdomains. Northern blot analysis shows that MAPKKK5 transcript is abundantly expressed in human heart and pancreas. The MAPKKK5 protein phosphorylates and activates MKK4 (aliases SERK1, MAPKK4) in vitro, and activates c-Jun N-terminal kinase (JNK)/stress-activated protein kinase (SAPK) during transient expression in COS and 293 cells; MAPKKK5 does not activate MAPK/ERK. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:mitogen-activated protein kinase kinase kinase 5
Source:NCBIAccessed: 11 August, 2015


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 11 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Signal Transduction
  • Transfection
  • MAP Kinase Kinase Kinases
  • Oligonucleotide Array Sequence Analysis
  • JNK Mitogen-Activated Protein Kinases
  • Enzyme Activation
  • Down-Regulation
  • Breast Cancer
  • Loss of Heterozygosity
  • Single Nucleotide Polymorphism
  • Cell Differentiation
  • Cell Cycle
  • Retroperitoneal Neoplasms
  • MAP Kinase Kinase Kinase 5
  • Chromosome 6
  • Melanoma
  • siRNA
  • Transcription Factor AP-1
  • Cancer Gene Expression Regulation
  • Reactive Oxygen Species
  • ras Proteins
  • beta Catenin
  • MicroRNAs
  • Sex Factors
  • Adipocytes
  • Xenograft Models
  • Skin Cancer
  • Tumor Suppressor Proteins
  • Up-Regulation
  • Gene Expression Profiling
  • Cell Proliferation
  • MAP Kinase Signaling System
  • Tumor Markers
  • Case-Control Studies
  • Western Blotting
  • Apoptosis
  • Immunohistochemistry
  • Liposarcoma
Tag cloud generated 11 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: MAP3K5 (cancer-related)

Park GB, Hur DY, Kim D
Combining CAL-101 with Celecoxib Enhances Apoptosis of EBV-transformed B-Cells Through MAPK-induced ER Stress.
Anticancer Res. 2015; 35(5):2699-708 [PubMed] Related Publications
BACKGROUND: Phosphoinositide-3 kinase (PI3K) inhibition attenuates proliferation and survival in B-cell malignancies. Celecoxib induces endoplasmic reticulum (ER) stress-induced apoptosis via a cyclo-oxgenase-2 (COX2)-independent manner in certain types of cancer cells. In the present study, we assessed the effects of combinations of drugs with a p110δ-specific inhibitor, CAL-101, and celecoxib to induce apoptosis in Epstein-Barr virus (EBV)-transformed B-cells and non-Hodgkin's lymphoma (NHL) cells.
MATERIALS AND METHODS: The apoptotic effect of combination treatment with CAL-101 and celecoxib on B-cell malignancies was determined by flow cytometry and immunoblotting.
RESULTS: Exposure to CAL-101 and celecoxib significantly increased apoptosis, which was accompanied by the inactivation of AKT, Ras homolog gene family, member A (RHOA), Rho-associated coiled-coil containing protein kinase 1 (ROCK1), and ROCK2 as well as up-regulation of Phosphatase and tensin homolog (PTEN). Co-treatment with CAL-101 and celecoxib triggered the ER stress response and the down-regulation of BCL2 and BCL-XL. SB203580, SP600125, and salubrinal effectively inhibited apoptosis and attenuated expression of phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (PERK) and CCAAT-enhancer-binding protein homologous protein (CHOP). Levels of apoptosis signal-regulating kinase 1 (ASK1) were also increased after treatment with CAL-101 and celecoxib.
CONCLUSION: The apoptosis of EBV-transformed B-cells and NHL cells caused by CAL-101 and celecoxib might be related to inhibiting the RHOA/ROCK pathway and might also be associated with mitogen-activated protein kinase (MAPK)-mediated ER stress.

El-Khattouti A, Sheehan NT, Monico J, et al.
CD133⁺ melanoma subpopulation acquired resistance to caffeic acid phenethyl ester-induced apoptosis is attributed to the elevated expression of ABCB5: significance for melanoma treatment.
Cancer Lett. 2015; 357(1):83-104 [PubMed] Related Publications
According to the cancer stem-like cell (CSC) hypothesis, neoplastic clones are maintained by a small fraction of cells with stem cell properties. Also, melanoma resistance to chemo- and radiotherapy is thought to be attributed to melanoma stem-like cells (MSCs). Caffeic acid phenethyl ester (CAPE) is a bioactive molecule, whose antitumor activity is approved in different tumor types. CAPE induced both apoptosis and E2F1 expression in CD133(-), but not in CD133(+) melanoma subpopulations. The resistance of CD133(+) melanoma subpopulation is attributed to the enhanced drug efflux mediated by ATP-binding cassette sub-family B member 5 (ABCB5), since the knockdown of ABCB5 was found to sensitize CD133(+) cells to CAPE. CAPE-induced apoptosis is mediated by E2F1 as evidenced by the abrogation of apoptosis induced in response to the knockdown of E2F1. The functional analysis of E2F1 in CD133(+) melanoma subpopulation demonstrated the ability of E2F1 gene transfer to trigger apoptosis of CD133(+) cells and to enhance the activation of apoptosis signal-regulating kinase (ASK1), c-Jun N-terminal kinase and p38, and the DNA-binding activities of the transcription factors AP-1 and p53. Also, the induction of E2F1 expression was found to enhance the expression of the pro-apoptotic proteins Bax, Noxa and Puma, and to suppress the anti-apoptotic protein Mcl-1. Using specific pharmacological inhibitors we could demonstrate that E2F1 overcomes the chemo-resistance of MSCs/CD133(+) cells by a mechanism mediated by both mitochondrial dysregulation and ER-stress-dependent pathways. In conclusion, our data addresses the mechanisms of CAPE/E2F1-induced apoptosis of chemo-resistant CD133(+) melanoma subpopulation.

Iżykowska K, Zawada M, Nowicka K, et al.
Submicroscopic genomic rearrangements change gene expression in T-cell large granular lymphocyte leukemia.
Eur J Haematol. 2014; 93(2):143-9 [PubMed] Related Publications
OBJECTIVES: To better understand the molecular pathogenesis of T-cell large granular lymphocyte leukemia (T-LGL), we decided to search for those genetic alterations in T-LGL patients and MOTN-1 cell line (established from T-LGL patient) that have an impact on gene expression and as a result can influence cell biology.
METHODS: Multicolor fluorescence in situ hybridization (mFISH) analysis of the MOTN-1 cell line was performed as well as paired-end next-generation sequencing (NGS; Illumina HiSeq2000) of this cell line and one T-LGL patient. In addition, chosen 6q region was characterized in three T-LGL patients using high-resolution comparative genomic hybridization (FT-CGH) and LM-PCR. Gene expression was studied by RNA sequencing (RNAseq; SOLID5500).
RESULTS: Rearrangements were detected within 1p and 2q in MOTN-1 affecting expression of FGR, ZEB2, and CASP8, and within 6q in MOTN-1 and one T-LGL patient affecting MAP3K5 and IFNGR1. Nineteen genes, among them FOXN3, RIN3, AKT1, PPP2R5C, were overexpressed as a result of an amplification in 14q in one T-LGL patient. Two novel fusion transcripts were identified: CASP8-ERBB4 in MOTN-1 and SBF1-PKHD1L1 in T-LGL patient.
CONCLUSIONS: This study showed that submicroscopic genomic rearrangements change gene expression in T-LGL. Several genes involved in rearrangements were previously linked to cancer and survival pattern that characterizes T-LGL cells.

Ishaq M, Kumar S, Varinli H, et al.
Atmospheric gas plasma-induced ROS production activates TNF-ASK1 pathway for the induction of melanoma cancer cell apoptosis.
Mol Biol Cell. 2014; 25(9):1523-31 [PubMed] Free Access to Full Article Related Publications
Atmospheric gas plasmas (AGPs) are able to selectively induce apoptosis in cancer cells, offering a promising alternative to conventional therapies that have unwanted side effects such as drug resistance and toxicity. However, the mechanism of AGP-induced cancer cell death is unknown. In this study, AGP is shown to up-regulate intracellular reactive oxygen species (ROS) levels and induce apoptosis in melanoma but not normal melanocyte cells. By screening genes involved in apoptosis, we identify tumor necrosis factor (TNF)-family members as the most differentially expressed cellular genes upon AGP treatment of melanoma cells. TNF receptor 1 (TNFR1) antagonist-neutralizing antibody specifically inhibits AGP-induced apoptosis signal, regulating apoptosis signal-regulating kinase 1 (ASK1) activity and subsequent ASK1-dependent apoptosis. Treatment of cells with intracellular ROS scavenger N-acetyl-l-cysteine also inhibits AGP-induced activation of ASK1, as well as apoptosis. Moreover, depletion of intracellular ASK1 reduces the level of AGP-induced oxidative stress and apoptosis. The evidence for TNF-signaling dependence of ASK1-mediated apoptosis suggests possible mechanisms for AGP activation and regulation of apoptosis-signaling pathways in tumor cells.

Canaparo R, Varchi G, Ballestri M, et al.
Polymeric nanoparticles enhance the sonodynamic activity of meso-tetrakis (4-sulfonatophenyl) porphyrin in an in vitro neuroblastoma model.
Int J Nanomedicine. 2013; 8:4247-63 [PubMed] Free Access to Full Article Related Publications
PURPOSE: Sonodynamic therapy is a developing noninvasive modality for cancer treatment, based on the selective activation of a sonosensitizer agent by acoustic cavitation. The activated sonosensitizer agent might generate reactive oxygen species leading to cancer cell death. We investigated the potential poly-methyl methacrylate core-shell nanoparticles (NPs) loaded with meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS) have to function as an innovative sonosensitizing system, ie, TPPS-NPs.
METHODS: Shockwaves (SWs) generated by a piezoelectric device were used to induce acoustic cavitation. The cytotoxic effect of the sonodynamic treatment with TPPS-NPs and SWs was investigated on the human neuroblastoma cell line, SH-SY5Y. Cells were exposed for 12 hours to TPPS-NPs (100 μg/mL) and then to SWs (0.43 mJ/mm(2) for 500 impulses, 4 impulses/second). Treatment with SWs, TPPS, and NPs alone or in combination was carried out as control.
RESULTS: There was a statistically significant decrease in SH-SY5Y cell proliferation after the sonodynamic treatment with TPPS-NPs and SWs. Indeed, there was a significant increase in necrotic (16.91% ± 3.89%) and apoptotic (27.45% ± 3.03%) cells at 48 hours. Moreover, a 15-fold increase in reactive oxygen species production for cells exposed to TPPS-NPs and SWs was observed at 1 hour compared with untreated cells. A statistically significant enhanced mRNA (messenger ribonucleic acid) expression of NRF2 (P<0.001) and a significant downregulation of TIGAR (P<0.05) and MAP3K5 (P<0.05) genes was observed in cells exposed to TPPS-NPs and SWs at 24 hours, along with a statistically significant release of cytochrome c (P<0.01) at 48 hours. Lastly, the sonosensitizing system was also investigated in an in vitro three-dimensional model, and the sonodynamic treatment significantly decreased the neuroblastoma spheroid growth.
CONCLUSION: The sonosensitizing properties of TPPS were significantly enhanced once loaded onto NPs, thus enhancing the sonodynamic treatment's efficacy in an in vitro neuroblastoma model.

El-Khattouti A, Selimovic D, Haïkel Y, et al.
Identification and analysis of CD133(+) melanoma stem-like cells conferring resistance to taxol: An insight into the mechanisms of their resistance and response.
Cancer Lett. 2014; 343(1):123-33 [PubMed] Related Publications
The presence and the involvement of cancer stem-like cells (CSCs) in tumor initiation and progression, and chemo-resistance are documented. Herein, we functionally analyzed melanoma stem-like cells (MSC)/CD133(+) cells on their resistance and response to taxol-induced apoptosis. Besides being taxol resistant, the CD133(+) cells demonstrated a growth advantage over the CD133(-) subpopulation. Taxol induced apoptosis on CD133(-) cells, but not on CD133(+) cells. In the CD133(-) subpopulation, the exposure to taxol induced the activation of apoptosis signal-regulating kinase1 (ASK1)/c-jun-N-terminal kinase (JNK), p38, extracellular signal regulated kinase (ERK) pathways and Bax expression, while in CD133(+) cells taxol was able only to enhance the activity of the ERK pathway. In CD133(+) cells, the direct gene transfer of Bax overcame the acquired resistance to taxol. Taken together, our data provide an insight into the mechanistic cascade of melanoma resistance to taxol and suggest Bax gene transfer as a complementary approach to chemotherapy.

Prickett TD, Zerlanko B, Gartner JJ, et al.
Somatic mutations in MAP3K5 attenuate its proapoptotic function in melanoma through increased binding to thioredoxin.
J Invest Dermatol. 2014; 134(2):452-60 [PubMed] Free Access to Full Article Related Publications
Patients with advanced metastatic melanoma have poor prognosis and the genetics underlying its pathogenesis are poorly understood. High-throughput sequencing has allowed comprehensive discovery of somatic mutations in cancer samples. Here, on analysis of our whole-genome and whole-exome sequencing data of 29 melanoma samples, we identified several genes that harbor recurrent nonsynonymous mutations. These included MAP3K5 (mitogen-activated protein kinase kinase kinase-5), which in a prevalence screen of 288 melanomas was found to harbor a R256C substitution in 5 cases. All MAP3K5-mutated samples were wild type for BRAF, suggesting a mutual exclusivity for these mutations. Functional analysis of the MAP3K5 R256C mutation revealed attenuation of MKK4 (mitogen-activated protein kinase kinase 4) activation through increased binding of the inhibitory protein thioredoxin (TXN/TRX-1/Trx), resulting in increased proliferation and anchorage-independent growth of melanoma cells. This mutation represents a potential target for the design of new therapies to treat melanoma.

Shi W, Hou X, Li X, et al.
Differential gene expressions of the MAPK signaling pathway in enterovirus 71-infected rhabdomyosarcoma cells.
Braz J Infect Dis. 2013 Jul-Aug; 17(4):410-7 [PubMed] Related Publications
BACKGROUND: Mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in response to viral infection. The aim of this study was to explore the function and mechanism of MAPK signaling pathway in enterovirus 71 (EV71) infection of human rhabdomyosarcoma (RD) cells.
METHODS: Apoptosis of RD cells was observed using annexin V-FITC/PI binding assay under a fluorescence microscope. Cellular RNA was extracted and transcribed to cDNA. The expressions of 56 genes of MAPK signaling pathway in EV71-infected RD cells at 8h and 20h after infection were analyzed by PCR array. The levels of IL-2, IL-4, IL-10, and TNF-α in the supernatant of RD cells infected with EV71 at different time points were measured by ELISA.
RESULTS: The viability of RD cells decreased obviously within 48h after EV71 infection. Compared with the control group, EV71 infection resulted in the significantly enhanced releases of IL-2, IL-4, IL-10 and TNF-α from infected RD cells (p<0.05). At 8h after infection, the expressions of c-Jun, c-Fos, IFN-β, MEKK1, MLK3 and NIK genes in EV71-infected RD cells were up-regulated by 2.08-6.12-fold, whereas other 19 genes (e.g. AKT1, AKT2, E2F1, IKK and NF-κB1) exhibited down-regulation. However, at 20h after infection, those MAPK signaling molecules including MEKK1, ASK1, MLK2, MLK3, NIK, MEK1, MEK2, MEK4, MEK7, ERK1, JNK1 and JNK2 were up-regulated. In addition, the expressions of AKT2, ELK1, c-Jun, c-Fos, NF-κB p65, PI3K and STAT1 were also increased.
CONCLUSION: EV71 infection induces the differential gene expressions of MAPK signaling pathway such as ERK, JNK and PI3K/AKT in RD cells, which may be associated with the secretions of inflammatory cytokines and host cell apoptosis.

Chen MB, Zhang Y, Wei MX, et al.
Activation of AMP-activated protein kinase (AMPK) mediates plumbagin-induced apoptosis and growth inhibition in cultured human colon cancer cells.
Cell Signal. 2013; 25(10):1993-2002 [PubMed] Related Publications
Here we report that activation of AMP-activated protein kinase (AMPK) mediates plumbagin-induced apoptosis and growth inhibition in both primary cultured human colon cancer cells and cell lines. Knocking-down of AMPKα by the target shRNA significantly inhibits plumbagin-induced cytotoxicity in cultured colon cancer cells, while forced activation of AMPK by introducing a constitutively active AMPK (CA-AMPK), or by the AMPK activator, inhibits HT-29 colon cancer cell growth. Our Western-blots and immunoprecipitation (IP) results demonstrate that plumbagin induces AMPK/Apoptosis signal regulating kinase 1 (ASK1)/TNF receptor-associated factor 2 (TRAF2) association to activate pro-apoptotic c-Jun N-terminal kinases (JNK)-p53 signal axis. Further, after plumbagin treatment, activated AMPK directly phosphorylates Raptor to inhibit mTOR complex 1 (mTORC1) activation and Bcl-2 expression in colon cancer cells. Finally, we found that exogenously-added short-chain ceramide (C6) enhances plumbagin-induced AMPK activation and facilitates cell apoptosis and growth inhibition. Our results suggest that AMPK might be the key mediator of plumbagin's anti-tumor activity.

Tarapore RS, Yang Y, Katz JP
Restoring KLF5 in esophageal squamous cell cancer cells activates the JNK pathway leading to apoptosis and reduced cell survival.
Neoplasia. 2013; 15(5):472-80 [PubMed] Free Access to Full Article Related Publications
Esophageal cancer is the eighth most common cancer in the world and has an extremely dismal prognosis, with a 5-year survival of less than 20%. Current treatment options are limited, and thus identifying new molecular targets and pathways is critical to derive novel therapies. Worldwide, more than 90% of esophageal cancers are esophageal squamous cell cancer (ESCC). Previously, we identified that Krüppel-like factor 5 (KLF5), a key transcriptional regulator normally expressed in esophageal squamous epithelial cells, is lost in human ESCC. To examine the effects of restoring KLF5 in ESCC, we transduced the human ESCC cell lines TE7 and TE15, both of which lack KLF5 expression, with retrovirus to express KLF5 upon doxycycline induction. When KLF5 was induced, ESCC cells demonstrated increased apoptosis and decreased viability, with up-regulation of the proapoptotic factor BAX. Interestingly, c-Jun N-terminal kinase (JNK) signaling, an important upstream mediator of proapoptotic pathways including BAX, was also activated following KLF5 induction. KLF5 activation of JNK signaling was mediated by KLF5 transactivation of two key upstream regulators of the JNK pathway, ASK1 and MKK4, and inhibition of JNK blocked apoptosis and normalized cell survival following KLF5 induction. Thus, restoring KLF5 in ESCC cells promotes apoptosis and decreases cell survival in a JNK-dependent manner, providing a potential therapeutic target for human ESCC.

Mahoney E, Byrd JC, Johnson AJ
Autophagy and ER stress play an essential role in the mechanism of action and drug resistance of the cyclin-dependent kinase inhibitor flavopiridol.
Autophagy. 2013; 9(3):434-5 [PubMed] Free Access to Full Article Related Publications
Chronic lymphocytic leukemia (CLL) is a mature B cell malignancy and is the most prevalent type of leukemia in adults. There is no curative therapy for this disease; however, several new agents have shown very promising results. Autophagy has not been studied in CLL and in this study we first sought to determine if autophagy was functional in CLL with classic inducers, and if this contributes to direct cytotoxicity or protection from cell death. While autophagy is activated with all classic stimuli of this process, only unfolded protein endoplasmic reticulum (ER) stress-mediated autophagy protects from cell death. Interestingly, select therapeutic agents (fludarabine, GS-1101, flavopiridol), which are active in CLL, also induce autophagy. Of interest, only the broad cyclin-dependent kinase inhibitor flavopiridol has improved efficacy when autophagy is antagonized biochemically (chloroquine) or by siRNA. This promoted an investigation which demonstrated unexpectedly that flavopiridol mediates ER stress and downstream activation of MAP3K5/ASK1, which ultimately is responsible for cell death. Similarly, autophagy activated in part via ER stress and also CDK5 inhibition is protective against cell death induced by this process. Collectively, our studies demonstrate that in CLL, autophagy is induced by multiple stimuli but only acts as a mechanism of resistance against ER stress-mediating agents. Similarly, flavopiridol mediates ER stress as a primary mechanism of action in CLL, and autophagy serves as a mechanism of resistance to this agent.

Tzeng HE, Tsai CH, Chang ZL, et al.
Interleukin-6 induces vascular endothelial growth factor expression and promotes angiogenesis through apoptosis signal-regulating kinase 1 in human osteosarcoma.
Biochem Pharmacol. 2013; 85(4):531-40 [PubMed] Related Publications
Osteosarcoma is characterized by a high malignant and metastatic potential. Angiogenesis is essential for the caner metastasis. Interleukin-6 (IL-6) is a multifunctional cytokine that is associated with the disease status and outcomes of cancers. However, the relationship between IL-6 and vascular endothelial growth factor (VEGF) expression in human osteosarcoma is mostly unknown. Here we found that the IL-6 and VEGF expression was correlated with tumor stage and significantly higher than that in normal bone. Incubation of osteosarcoma cells with IL-6 increased VEGF mRNA and protein expression. Pretreatment of cells with IL-6R antibody reduced IL-6-mediated VEGF production. The apoptosis signal-regulating kinase 1 (ASK1)/p38/AP-1 pathway was activated after IL-6 treatment, and IL-6-induced VEGF expression was abolished by the specific inhibitor and siRNA of ASK1, p38, and AP-1 cascades. Importantly, knockdown IL-6 reduced VEGF expression and abolished osteosarcoma conditional medium-mediated angiogenesis. Taken together, these results indicate that IL-6 occurs through ASK1 and p38, which in turn activates AP-1, resulting in the activations of VEGF expression and contributing the angiogenesis of human osteosarcoma cells.

Guo Y, Xu X, Liu Z, et al.
Apoptosis signal-regulating kinase 1 is associated with the effect of claudin-6 in breast cancer.
Diagn Pathol. 2012; 7:111 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Previous studies have demonstrated that claudin-6 functions as a cancer suppressor in human MCF-7 breast cancer cells. The growth inhibitory effect could be attributed to inhibition of cell proliferation and induction of apoptosis. The purpose of the current study was to examine the involvement of apoptosis signal-regulating kinase 1 (ASK1) in the anticancer effect of claudin-6.
METHODS: Immunohistochemical analysis was performed to evaluate the ASK1 protein expression and the correlation between ASK1, claudin-6 and clinicopathological features in 85 samples of breast invasive ductal carcinomas (IDC). Western blotting and RT-PCR was carried out to examine the expression of ASK1 and claudin-6 in MCF-7 cell clones transfected with claudin-6.
RESULTS: Immunohistochemical analysis showed that ASK1 expression was significantly related with that of claudin-6 in breast invasive ductal carcinomas (P < 0.05). In addition, a positive correlation between ASK1 and C-erb B 2 protein expression was identified (P < 0.05). Western blotting and RT-PCR consistently revealed that the level of ASK1 protein and mRNA was upregulated in MCF-7 cell clones transfected with claudin-6.
CONCLUSIONS: Our data suggests, for the first time, that the ASK1 signal may play a positive role in the inhibitory effect of claudin-6 in breast cancer.
VIRTUAL SLIDES: The virtual slide(s) for this article can be found here:

Sharma PK, Dwarakanath BS, Varshney R
Radiosensitization by 2-deoxy-D-glucose and 6-aminonicotinamide involves activation of redox sensitive ASK1-JNK/p38MAPK signaling in head and neck cancer cells.
Free Radic Biol Med. 2012; 53(7):1500-13 [PubMed] Related Publications
Our previous studies on simultaneous inhibition of glycolysis by 2-deoxy-D-glucose (2-DG) and pentose phosphate activity by 6-aminonicotinamide (6-AN) have been shown to induce oxidative stress mediated selective radiosensitization in wide range of human malignant cells. However, the mechanism of radiosensitization induced by this combination (2-DG+6-AN) is not completely understood. Since activation of apoptotic signal regulating kinase (ASK1) and subsequent apoptosis are implicated in oxidative stress response, the role of ASK1 activation in radiosensitization by this combination was investigated in the present study. Our results demonstrated that redox alterations induced by this combination activated ASK1 and subsequent apoptosis during radiosensitization of head and neck carcinoma cells (KB). In addition, mRNA and protein expression of thioredoxin and thioredoxin reductase decreased significantly under similar treatment conditions. Further, the downstream targets such as JNK and p38MAPK were also activated by this combination, and their pharmacological inhibition by SP600125 and SB201291 respectively resulted in suppression of 2-DG+6-AN mediated apoptosis in irradiated KB cells. Interestingly, the activation of ASK1 was mediated by hydrogen peroxide rather than superoxide anions as PEG-catalase but not PEG-SOD suppressed its activation. Our observations clearly suggest that redox alterations by inhibition of glucose metabolism serves as a molecular switch that activate ASK1-JNK/p38MAPK signaling in malignant cells during radiosensitization by 2-DG+6-AN. The present study emphasizes the importance of redox alterations in determining radiosensitivity of tumor cells that may greatly influence the outcome of radiation therapy.

Yu JS, Kim AK
Platycodin D induces reactive oxygen species-mediated apoptosis signal-regulating kinase 1 activation and endoplasmic reticulum stress response in human breast cancer cells.
J Med Food. 2012; 15(8):691-9 [PubMed] Related Publications
Platycodin D (PD), a natural compound found in Platycodon grandiflorum, induces apoptotic cell death in various carcinoma cells. One mechanism of PD-mediated cell death is by activation of mitogen-activated protein kinases, as suggested in a recent report. In this study, we further examined upstream signal pathways and the relationship between these signals and reactive oxygen species (ROS). Using immunoblotting assays, we found that PD activated apoptosis signal-regulating kinase 1 (ASK1) through phosphorylation of ASK1 at threonine and dephosphorylation of ASK1 at serine. We also showed that PD caused activation of the endoplasmic reticulum (ER) stress response. This was supported by observations showing that treatment with PD induces phosphorylation of PKR-like ER kinase (PERK) and eukaryotic initiation factor 2 α (eIF 2α), up-regulating expression of glucose-regulated protein 78/immunoglobulin heavy chain binding protein (GRP78/Bip) and CCAAT/enhancer-binding protein homologous protein/growth arrest and DNA damage-inducible gene 153 (CHOP/GADD153) and activation of caspase-4. Furthermore, PD-induced ASK1 and ER stress responses were inhibited by the antioxidant N-acetyl-l-cysteine. These results suggest that ROS play a critical role for activation of ASK1 and ER stress in PD-treated cancer cells.

Mahoney E, Lucas DM, Gupta SV, et al.
ER stress and autophagy: new discoveries in the mechanism of action and drug resistance of the cyclin-dependent kinase inhibitor flavopiridol.
Blood. 2012; 120(6):1262-73 [PubMed] Free Access to Full Article Related Publications
Cyclin dependent kinase (CDK) inhibitors, such as flavopiridol, demonstrate significant single-agent activity in chronic lymphocytic leukemia (CLL), but the mechanism of action in these nonproliferating cells is unclear. Here we demonstrate that CLL cells undergo autophagy after treatment with therapeutic agents, including fludarabine, CAL-101, and flavopiridol as well as the endoplasmic reticulum (ER) stress-inducing agent thapsigargin. The addition of chloroquine or siRNA against autophagy components enhanced the cytotoxic effects of flavopiridol and thapsigargin, but not the other agents. Similar to thapsigargin, flavopiridol robustly induces a distinct pattern of ER stress in CLL cells that contributes to cell death through IRE1-mediated activation of ASK1 and possibly downstream caspases. Both autophagy and ER stress were documented in tumor cells from CLL patients receiving flavopiridol. Thus, CLL cells undergo autophagy after multiple stimuli, including therapeutic agents, but only with ER stress mediators and CDK inhibitors is autophagy a mechanism of resistance to cell death. These findings collectively demonstrate, for the first time, a novel mechanism of action (ER stress) and drug resistance (autophagy) for CDK inhibitors, such as flavopiridol in CLL, and provide avenues for new therapeutic combination approaches in this disease.

Yao C, Wu S, Li D, et al.
Co-administration phenoxodiol with doxorubicin synergistically inhibit the activity of sphingosine kinase-1 (SphK1), a potential oncogene of osteosarcoma, to suppress osteosarcoma cell growth both in vivo and in vitro.
Mol Oncol. 2012; 6(4):392-404 [PubMed] Related Publications
Elucidation of the mechanisms of chemo-resistance and implementation of strategies to overcome it will be pivotal to improve the survival for osteosarcoma (OS) patients. We here suggest that sphingosine kinase-1 (SphK1) might be the key factor contributing to chemo-resistance in OS. Our Western-blots and immunohistochemistry results showed that SphK1 is over-expressed in multiple clinical OS tissues. Over-expression of SphK1 in OS cell line U2OS promoted its growth and endorsed its resistance against doxorubicin, while knocking-down of SphK1 by shRNA inhibited U2OS cell growth and increased its sensitivity to doxorubicin. Co-administration phenoxodiol with doxorubicin synergistically inhibited SphK1 activity to trigger cellular ceramide accumulation, and achieved synergistic anti-OS growth effect, accompanied with a significant increased of apoptosis and cytotoxicity. Increased cellular level of ceramide by the co-administration induced the association between Akt and Protein Phosphatase 1 (PP1) to dephosphorylate Akt, and to introduce a constitutively active Akt (CA-Akt) restored Akt activation and diminished cell growth inhibition. Further, phenoxodiol and doxorubicin synergistically activated apoptosis signal-regulating kinase 1(ASK1)/c-jun-NH2-kinase (JNK) signaling, which also contributed to cell growth inhibition. Significantly, the role of SphK1 in OS cell growth and the synergistic anti-OS effect of phenoxodiol and doxorubicin were also seen in a mice OS xenograft model. In conclusion, our data suggest that SphK1 might be a critical oncogene of OS and co-administration phenoxodiol with doxorubicin synergistically inhibited the activity of SphK1 to suppress osteosarcoma cell growth both in vivo and in vitro.

Kim SM, Chung MJ, Ha TJ, et al.
Neuroprotective effects of black soybean anthocyanins via inactivation of ASK1-JNK/p38 pathways and mobilization of cellular sialic acids.
Life Sci. 2012; 90(21-22):874-82 [PubMed] Related Publications
AIMS: To investigate neuroprotective effects of three major anthocyanins (cyanidin-3-O-glucoside, delphinidin-3-O-glucoside, and petunidin-3-O-glucoside) isolated from the black soybean (Glycine max L.) cv. Cheongja 3 seed coat against H(2)O(2)-induced cell death of human brain neuroblastoma SK-N-SH cells.
MAIN METHODS: Cell viability, reactive oxygen species (ROS) generation, production and expression of heme oxygenase (HO)-1 and inactivation of mitogen-activated protein (MAP) kinase cascades were determined by MTT assay, 2,7-dichlorofluorescein diacetate (DCF-DA) assay, reverse transcriptase polymerase chain reaction (RT-PCR), and western blotting, respectively.
KEY FINDINGS: Pretreatment with anthocyanins reduced the cytotoxicity of H(2)O(2) on SK-N-SH cells, dose-dependently reduced the intracellular ROS level and inactivated apoptosis signal-regulating kinase (ASK1, Thr845), p38, and c-Jun N-terminal kinase (JNK) proteins. The HO-1 and Neu1 mRNA levels were increased by H(2)O(2) (25 μM) and further elevated by the pretreatment with anthocyanins. Sialic acids added to the culture plates not only attenuated the cytotoxicity of H(2)O(2) (25 μM) but also reduced intracellular ROS level. These results suggest that Cheongja 3 black soybean seed coat anthocyanins have brain neuroprotective effects against oxidative stress (H(2)O(2)) by inhibiting the activation of ASK1-JNK/p38 pathways, scavenging ROS, stimulating the expression of HO-1 and, more interestingly, recruiting cellular free sialic acids through up-regulation of Neu1 sialidase gene expression.
SIGNIFICANCE: This is the first report indicating potent health benefits of black soybean seed coat anthocyanins in neuroprotection by triggering mobilization of cellular free sialic acid and utilizing it as an additional biological antioxidant in brain neural cells.

Mo C, Dai Y, Kang N, et al.
Ectopic expression of human MutS homologue 2 on renal carcinoma cells is induced by oxidative stress with interleukin-18 promotion via p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) signaling pathways.
J Biol Chem. 2012; 287(23):19242-54 [PubMed] Free Access to Full Article Related Publications
Human MutS homologue 2 (hMSH2), a crucial element of the highly conserved DNA mismatch repair system, maintains genetic stability in the nucleus of normal cells. Our previous studies indicate that hMSH2 is ectopically expressed on the surface of epithelial tumor cells and recognized by both T cell receptor γδ (TCRγδ) and natural killer group 2 member D (NKG2D) on Vδ2 T cells. Ectopically expressed hMSH2 could trigger a γδ T cell-mediated cytolysis. In this study, we showed that oxidative stress induced ectopic expression of hMSH2 on human renal carcinoma cells. Under oxidative stress, both p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) pathways have been confirmed to mediate the ectopic expression of hMSH2 through the apoptosis-signaling kinase 1 (ASK1) upstream and activating transcription factor 3 (ATF3) downstream of both pathways. Moreover, renal carcinoma cell-derived interleukin (IL)-18 in oxidative stress was a prominent stimulator for ectopically induced expression of hMSH2, which was promoted by interferon (IFN)-γ as well. Finally, oxidative stress or pretreatment with IL-18 and IFN-γ enhanced γδ T cell-mediated cytolysis of renal carcinoma cells. Our results not only establish a mechanism of ectopic hMSH2 expression in tumor cells but also find a biological linkage between ectopic expression of hMSH2 and activation of γδ T cells in stressful conditions. Because γδ T cells play an important role in the early stage of innate anti-tumor response, γδ T cell activation triggered by ectopically expressed hMSH2 may be an important event in immunosurveillance for carcinogenesis.

Teicher BA
Searching for molecular targets in sarcoma.
Biochem Pharmacol. 2012; 84(1):1-10 [PubMed] Related Publications
Sarcoma are about 1% of cancers. Within that 1% are widely varied tumors now divided into types and subtypes. Sarcoma occur in patients of all ages with frequency spread evenly over the human age range. Although the specific cell of origin of many sarcoma remains unclear, sarcoma are all tumors of mesenchymal origin. The mesenchymal stem cell, a pluripotent cell, which gives rise to varied differentiated cells including osteocytes, adipocytes, chondrocytes, muscle cells, fibroblasts, neural cells and stromal cells, is the most likely ultimate cell of origin for sarcoma. When mesenchymal stem cell genetics go awry and malignant transformation occurs sarcoma including osteosarcoma, Ewing's sarcoma, chondrosarcoma, rhabdomyosarcoma, synovial sarcoma fibrosarcoma, liposarcoma and many others can initiate. Our knowledge of sarcoma genetics is increasing rapidly. Two general groups, sarcoma arising from chromosomal translocations and sarcoma with very complex genetics, can be identified. Genes that are frequently mutated in sarcoma include TP53, NF1, PIK3CA, HDAC1, IDH1 and 2, KDR, KIT and MED12. Genes that are frequently amplified in sarcoma include CDK4, YEATS4, HMGA2, MDM2, JUN, DNM3, FLT4, MYCN, MAP3K5, GLI1 and the microRNAs miR-214 and miR-199a2. Genes that are upregulated in sarcoma include MUC4, CD24, FOXL1, ANGPTL2, HIF1α, MDK, cMET, TIMP-2, PRL, PCSK1, IGFR-1, TIE1, KDR, TEK, FLT1 and several microRNAs. While some alterations occur in specific subtypes of sarcoma, others cross several sarcoma types. Discovering and developing new therapeutic approaches for these relentless diseases is critical. The detailed knowledge of sarcoma genetics may allow development of sarcoma subtype-targeted therapeutics.

Zhou JP, Chen X, Feng S, et al.
Systems biology modeling reveals a possible mechanism of the tumor cell death upon oncogene inactivation in EGFR addicted cancers.
PLoS One. 2011; 6(12):e28930 [PubMed] Free Access to Full Article Related Publications
Despite many evidences supporting the concept of "oncogene addiction" and many hypotheses rationalizing it, there is still a lack of detailed understanding to the precise molecular mechanism underlying oncogene addiction. In this account, we developed a mathematic model of epidermal growth factor receptor (EGFR) associated signaling network, which involves EGFR-driving proliferation/pro-survival signaling pathways Ras/extracellular-signal-regulated kinase (ERK) and phosphoinositol-3 kinase (PI3K)/AKT, and pro-apoptotic signaling pathway apoptosis signal-regulating kinase 1 (ASK1)/p38. In the setting of sustained EGFR activation, the simulation results show a persistent high level of proliferation/pro-survival effectors phospho-ERK and phospho-AKT, and a basal level of pro-apoptotic effector phospho-p38. The potential of p38 activation (apoptotic potential) due to the elevated level of reactive oxygen species (ROS) is largely suppressed by the negative crosstalk between PI3K/AKT and ASK1/p38 pathways. Upon acute EGFR inactivation, the survival signals decay rapidly, followed by a fast increase of the apoptotic signal due to the release of apoptotic potential. Overall, our systems biology modeling together with experimental validations reveals that inhibition of survival signals and concomitant release of apoptotic potential jointly contribute to the tumor cell death following the inhibition of addicted oncogene in EGFR addicted cancers.

Sau A, Filomeni G, Pezzola S, et al.
Targeting GSTP1-1 induces JNK activation and leads to apoptosis in cisplatin-sensitive and -resistant human osteosarcoma cell lines.
Mol Biosyst. 2012; 8(4):994-1006 [PubMed] Related Publications
The effect of the glutathione transferase P1-1 (GSTP1-1) targeting has been investigated in both sensitive (U-2OS) and cisplatin-resistant (U-2OS/CDDP4 μg) human osteosarcoma cell lines. Despite the different enzyme's content, inhibition of GSTP1-1 by 6-(7-nitro-2,1,3-benzoxadiazol-4-ylthio)hexanol (NBDHEX) causes the activation of c-Jun N-terminal kinase (JNK) and apoptosis in both cell lines. However, different time courses of JNK activation and cell responses are observed. Whereas in the U-2OS/CDDP4 μg cell line drug treatment results in an early increase of caspase activity and secondary necrosis, in the U-2OS cells it mainly causes an early cell cycle arrest followed by apoptosis. In order to elucidate the action mechanism of NBDHEX we performed a proteomic investigation by label-free nLC-MS(E). The high-throughput analysis associated with a bioinformatic tool suggested the involvement of the TNF receptor associated factor (TRAF) family in the cellular response to the drug treatment. We report experimental evidence of the interaction between GSTP1-1 and TRAF2 and we demonstrate that NBDHEX is able to dissociate the GSTP1-1 : TRAF2 complex. This restores the TRAF2 : ASK1 signaling, thereby leading to the simultaneous and prolonged activation of JNK and p38. These mitogen-activated protein kinases (MAPKs) mediate different effects: JNK is crucial for apoptosis, whereas p38 causes an increase in the p21 level and a concomitant cell cycle arrest. Our study shows that GSTP1-1 plays an important regulatory role in TRAF signaling of osteosarcoma and discloses new features of the action mechanism of NBDHEX that suggest potentially practical consequences of these findings.

Selimovic D, Ahmad M, El-Khattouti A, et al.
Apoptosis-related protein-2 triggers melanoma cell death by a mechanism including both endoplasmic reticulum stress and mitochondrial dysregulation.
Carcinogenesis. 2011; 32(8):1268-78 [PubMed] Related Publications
Metastatic cancers including melanoma are frequently associated with increased resistance to apoptosis induced by various therapeutic modalities, and the success of systemic therapy for the treatment of metastatic melanoma is minimal. In the present study, we demonstrated the ability of apoptosis-related protein (APR)-2 to trigger cell death via mechanism mediated by both endoplasmic reticulum (ER) stress [as evidenced by the increase of intracellular Ca(2+) release, the activation of both, inositol-requiring enzyme 1α (IRE1α) and calpain and cleavage of caspase-4] and mitochondrial dysregulation as evidenced by the loss of mitochondrial membrane potential, Cytochrome c release and cleavage of caspases-9 and -3, and poly adenosine diphosphate ribose polymerase (PARP). Also, the activation of apoptosis signal-regulating kinase (ASK) 1, c-jun-N-terminal kinase (JNK) and the transcription factors AP-1 and p53, and the induction of Bax expression were noted in APR-2-expressing cells. Both immune fluorescence staining and western blotting revealed the localization of APR-2 at ER and Bax protein at both mitochondria and ER. However, data of inhibitory experiments demonstrated that APR-2-induced apoptosis of melanoma cells is mediated by three parallel pathways: one of them IRE1/tumour necrosis factor receptor-associated factor 2/ASK1/JNK/Cyt.c/caspase-9/caspase-3/PARP) seems to be mitochondrial dependent, whereas, the other two pathways namely calpain/caspase-4/caspase-9/caspase-3/PARP and protein kinase RNA-like ER kinase/ATF4/C/EBP homologous protein (CHOP)/Bim seem to be mitochondrial independent. In conclusion, our data provide insight into the molecular mechanism of APR-2-induced apoptosis and suggest APR-2 gene transfer as an alternative approach for the treatment of chemoresistance melanoma metastasis.

Yi M, Yang J, Chen X, et al.
RASSF1A suppresses melanoma development by modulating apoptosis and cell-cycle progression.
J Cell Physiol. 2011; 226(9):2360-9 [PubMed] Free Access to Full Article Related Publications
The tumor suppressor candidate gene Ras association domain family 1, isoform A (RASSF1A) encodes a microtubule-associated protein that is implicated in the regulation of cell proliferation, migration, and apoptosis. Several studies indicate that down-regulation of RASSF1A resulting from promoter hypermethylation is a frequent epigenetic abnormality in malignant melanoma. In this study, we report that compared with melanocytes in normal skins or benign skin lesions, RASSF1A is down-regulated in melanoma tissues as well as cell lines, and its expression negatively correlates with lymph node metastasis. Following ectopic expression in RASSF1A-deficient melanoma A375 cell line, RASSF1A reduces cell viability, suppresses cell-cycle progression but enhances apoptotic cell death. In vivo, RASSF1A expression inhibits the tumorigenic potential of A375 cells in nude mice, which also correlates with decreased cell proliferation and increased apoptosis. On the molecular level, ectopic RASSF1A expression leads to differential expression of 209 genes, including 26 down-regulated and 183 up-regulated ones. Among different signaling pathways, activation of the apoptosis signal-regulating kinase 1 (ASK1)/p38 MAP kinase signaling is essential for RASSF1A-induced mitochondrial apoptosis, and the inhibition of the Akt/p70S6 kinase/eIF4E signaling is also important for RASSF1A-mediated apoptosis and cell-cycle arrest. This is the first study exploring the biological functions and the underlying mechanisms of RASSF1A during melanoma development. It also identifies potential targets for further diagnosis and clinical therapy.

Stępkowski TM, Kruszewski MK
Molecular cross-talk between the NRF2/KEAP1 signaling pathway, autophagy, and apoptosis.
Free Radic Biol Med. 2011; 50(9):1186-95 [PubMed] Related Publications
Oxidative stress, perturbations in the cellular thiol level and redox balance, affects many cellular functions, including signaling pathways. This, in turn, may cause the induction of autophagy or apoptosis. The NRF2/KEAP1 signaling pathway is the main pathway responsible for cell defense against oxidative stress and maintaining the cellular redox balance at physiological levels. The relation between NRF2/KEAP1 signaling and regulation of apoptosis and autophagy is not well understood. In this hypothesis article we discuss how KEAP1 protein and its direct interactants (such as PGAM5, prothymosin α, FAC1 (BPTF), and p62) provide a molecular foundation for a possible cross-talk between NRF2/KEAP1, apoptosis, and autophagy pathways. We present a hypothesis for how NRF2/KEAP1 may interfere with the cellular apoptosis-regulatory machinery through activation of the ASK1 kinase by a KEAP1 binding partner-PGAM5. Based on very recent experimental evidence, new hypotheses for a cross-talk between NF-κB and the NRF2/KEAP1 pathway in the context of autophagy-related "molecular hub" protein p62 are also presented. The roles of KEAP1 molecular binding partners in apoptosis regulation during carcinogenesis and in neurodegenerative diseases are also discussed.

Hayakawa Y, Hirata Y, Nakagawa H, et al.
Apoptosis signal-regulating kinase 1 and cyclin D1 compose a positive feedback loop contributing to tumor growth in gastric cancer.
Proc Natl Acad Sci U S A. 2011; 108(2):780-5 [PubMed] Free Access to Full Article Related Publications
Mitogen-activated protein kinase (MAPK) pathways regulate multiple cellular functions and are highly active in many types of human cancers. Apoptosis signal-regulating kinase 1 (ASK1) is an upstream MAPK involved in apoptosis, inflammation, and carcinogenesis. This study investigated the role of ASK1 in the development of gastric cancer. In human gastric cancer specimens, we observed increased ASK1 expression, compared to nontumor epithelium. Using a chemically induced murine gastric tumorigenesis model, we observed increased tumor ASK1 expression, and ASK1 knockout mice had both fewer and smaller tumors than wild-type (WT) mice. ASK1 siRNA inhibited cell proliferation through the accumulation of cells in G1 phase of the cell cycle, and reduced cyclin D1 expression in gastric cancer cells, whereas these effects were uncommon in other cancer cells. ASK1 overexpression induced the transcription of cyclin D1, through AP-1 activation, and ASK1 levels were regulated by cyclin D1, via the Rb-E2F pathway. Exogenous ASK1 induced cyclin D1 expression, followed by elevated expression of endogenous ASK1. These results indicate an autoregulatory mechanism of ASK1 in the development of gastric cancer. Targeting this positive feedback loop, ASK1 may present a potential therapeutic target for the treatment of advanced gastric cancer.

Tap WD, Eilber FC, Ginther C, et al.
Evaluation of well-differentiated/de-differentiated liposarcomas by high-resolution oligonucleotide array-based comparative genomic hybridization.
Genes Chromosomes Cancer. 2011; 50(2):95-112 [PubMed] Related Publications
Well-differentiated/de-differentiated liposarcomas (WDLS/DDLS) encompass an intriguing disease model in which a temporal intersection occurs between the malignant transformation of mesenchymal cells and the process of adipogenesis. Deciphering the molecular events that trigger and are characteristic of the intersection of these oncogenic and normal processes is critical to affect the often morbid and lethal consequences of malignant tumors of fat. High-resolution genome-wide oligonucleotide array-based comparative genomic hybridization (aCGH) with matched gene expression analyses was performed on seven lipomas, one hibernoma, and 38 WD and DDLS to define and compare the genomic events associated with these tumors. WD and DDLS had complex karyotypes. On average, WDLS had 11.1 and DDLS had 22.7 chromosomal copy number aberrations. All of the liposarcomas had 12q13-q15 amplifications with varying peaks at CDK4 (12q14.1), HMGA2 (12q14.3), and MDM2 (12q15); 24% of the DDLS and no WDLS had 1p32.2 (JUN) amplifications; 33% WDLS and 35% DDLS had 1q24.3 amplifications involving DNM3 and miR-214/miR-199a2; 24% of the liposarcomas had 6q23-q24 amplifications (including MAP3K5). Amplifications in GLI1 (12q13.3), JUN, and MAP3K5 (6q23.3) were mutually exclusive and occurred predominately in the DDLS. 6q amplifications occurred primarily in retroperitoneal tumors and females represented the majority of those patients who developed fatty tumors prior to the age of 50 years old. This detailed genetic mapping provides insight into the heterogeneity of WD and DDLS and the chromosomal and genetic abnormalities that are present in and distinguish these mesenchymal malignancies.

Calvisi DF, Ladu S, Conner EA, et al.
Inactivation of Ras GTPase-activating proteins promotes unrestrained activity of wild-type Ras in human liver cancer.
J Hepatol. 2011; 54(2):311-9 [PubMed] Free Access to Full Article Related Publications
BACKGROUND & AIMS: Aberrant activation of the RAS pathway is ubiquitous in human hepatocarcinogenesis, but the molecular mechanisms leading to RAS induction in the absence of RAS mutations remain under-investigated. We defined the role of Ras GTPase activating proteins (GAPs) in the constitutive activity of Ras signaling during human hepatocarcinogenesis.
METHODS: The mutation status of RAS genes and RAS effectors was assessed in a collection of human hepatocellular carcinomas (HCC). Levels of RAS GAPs (RASA1-4, RASAL1, nGAP, SYNGAP1, DAB2IP, and NF1) and the RASAL1 upstream inducer PITX1 were determined by real-time RT-PCR and immunoblotting. The promoter and genomic status of RASAL1, DAB2IP, NF1, and PITX1 were assessed by methylation assays and microsatellite analysis. Effects of RASAL1, DAB2IP, and PITX1 on HCC growth were evaluated by transfection and siRNA analyses of HCC cell lines.
RESULTS: In the absence of Ras mutations, downregulation of at least one RAS GAP (RASAL1, DAB2IP, or NF1) was found in all HCC samples. Low levels of DAB2IP and PITX1 were detected mostly in a HCC subclass from patients with poor survival, indicating that these proteins control tumor aggressiveness. In HCC cells, reactivation of RASAL1, DAB2IP, and PITX1 inhibited proliferation and induced apoptosis, whereas their silencing increased proliferation and resistance to apoptosis.
CONCLUSIONS: Selective suppression of RASAL1, DAB2IP, or NF1 RAS GAPs results in unrestrained activation of Ras signaling in the presence of wild-type RAS in HCC.

Noh KT, Cho SG, Choi EJ
Knockdown of apoptosis signal-regulating kinase 1 modulates basal glycogen synthase kinase-3β kinase activity and regulates cell migration.
FEBS Lett. 2010; 584(18):4097-101 [PubMed] Related Publications
GSK-3β is a basally active kinase. Axin forms a complex with GSK-3β and β-catenin; this complex promotes the GSK-3β-dependent phosphorylation of β-catenin, thereby inducing its degradation. However, the inhibition of GSK-3β provokes cell migration via the dysregulation of β-catenin. In this study, we determined that the level of apoptosis signal-regulating kinase 1 (ASK1) was lower in a metastatic breast cancer cell line, compared to that of non-metastatic cancer cell lines and the knockdown of ASK1 not only induces β-catenin activation via the inhibition of GSK-3β and collapsing the subsequent protein complex by regulating Axin dynamics, but also stimulates cell migration. Together, the blockage of the GSK-3β-β-catenin pathway resulting from the knockdown of ASK1 modulates the migration of breast cancer cells.

Chun JN, Choi B, Lee KW, et al.
Cytosolic Hsp60 is involved in the NF-kappaB-dependent survival of cancer cells via IKK regulation.
PLoS One. 2010; 5(3):e9422 [PubMed] Free Access to Full Article Related Publications
Cytoplasmic presence of Hsp60, which is principally a nuclear gene-encoded mitochondrial chaperonin, has frequently been stated, but its role in intracellular signaling is largely unknown. In this study, we demonstrate that the cytosolic Hsp60 promotes the TNF-alpha-mediated activation of the IKK/NF-kappaB survival pathway via direct interaction with IKKalpha/beta in the cytoplasm. Selective loss or blockade of cytosolic Hsp60 by specific antisense oligonucleotide or neutralizing antibody diminished the IKK/NF-kappaB activation and the expression of NF-kappaB target genes, such as Bfl-1/A1 and MnSOD, which thus augmented intracellular ROS production and ASK1-dependent cell death, in response to TNF-alpha. Conversely, the ectopic expression of cytosol-targeted Hsp60 enhanced IKK/NF-kappaB activation. Mechanistically, the cytosolic Hsp60 enhanced IKK activation via upregulating the activation-dependent serine phosphorylation in a chaperone-independent manner. Furthermore, transgenic mouse study showed that the cytosolic Hsp60 suppressed hepatic cell death induced by diethylnitrosamine in vivo. The cytosolic Hsp60 is likely to be a regulatory component of IKK complex and it implicates the first mitochondrial factor that regulates cell survival via NF-kappaB pathway.

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