Arsenic trioxide-dependent activation of thousand-and-one amino acid kinase 2 and transforming growth factor-beta-activated kinase 1

Spinal TAOK2 contributes to neuropathic pain via cGAS-STING activation in rats

Thousand and one amino acid kinase 2 (TAOK2) is a member of the mammalian sterile 20 kinase family and is implicated in neurodevelopmental disorders; however, its role in neuropathic pain remains unknown. Here, we found that TAOK2 was enriched and activated after chronic constriction injury (CCI) in the rat spinal dorsal horn. Meanwhile, cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling was also activated with hyperalgesia. Silencing TAOK2 reversed hyperalgesia and suppressed the activation of cGAS-STING signaling induced by CCI, while pharmacological activation of TAOK2 induced pain hypersensitivity and upregulation of cGAS-STING signaling in naive rats. Furthermore, pharmacological inhibition or gene silencing of cGAS-STING signaling attenuated CCI-induced hyperalgesia. Taken together, these data demonstrate that the activation of spinal TAOK2 contributes to CCI-induced hyperalgesia via cGAS-STING signaling activation, providing new molecular targets for the treatment of neuropathic pain.

Suppression of HSP70 inhibits the development of acute lymphoblastic leukemia via TAK1/Egr-1

Acute lymphoblastic leukemia (ALL), usually treated with chemotherapy, has limited therapeutic effects and high toxicity. Upregulation of HSP70 induces tumor development, however, the molecular mechanism of HSP70 in ALL remains unclear. In our research, we aimed to investigate the role of HSP70 in ALL, specifically the molecular mechanisms underlying cell apoptosis and proliferation. We found that HSP70 expression in leukomonocytes from ALL patients was increased compared with the control group. HSP70 expression in NALM-6 and BE-13 was also up-regulated contrast with AHH-1. Inhibition of HSP70 significantly promoted cell apoptosis and suppressed cell proliferation in ALL cell lines. Suppression of HSP70 decreased TAK1 and increased Egr-1 protein expression. Further experiments indicated that overexpression of TAK1 ameliorated the effect of HSP70 inhibition on Egr-1 protein expression, cell apoptosis and proliferation. In order to determine whether the effect of HSP70 inhibition on apoptosis and proliferation of ALL cell lines could be achieved via regulation of Egr-1, we performed a loss-of-function experiment for Egr-1. Egr-1 suppression was found to reverse the effect of HSP70 inhibition on cell apoptosis and proliferation in ALL. Taken together, our results suggest that HSP70 inhibition upregulates Egr-1 via TAK1, inducing apoptosis and restricting proliferation in ALL cells.

Differential Response of Glioma Stem Cells to Arsenic Trioxide Therapy Is Regulated by MNK1 and mRNA Translation

Mesenchymal (MES) and proneural (PN) are two distinct glioma stem cell (GSC) populations that drive therapeutic resistance in glioblastoma (GBM). We screened a panel of 650 small molecules against patient-derived GBM cells to discover compounds targeting specific GBM subtypes. Arsenic trioxide (ATO), an FDA-approved drug that crosses the blood-brain barrier, was identified as a potent PN-specific compound in the initial screen and follow-up validation studies. Furthermore, MES and PN GSCs exhibited differential sensitivity to ATO. As ATO has been shown to activate the MAPK-interacting kinase 1 (MNK1)-eukaryotic translation initiation factor 4E (eIF4E) pathway and subsequent mRNA translation in a negative regulatory feedback manner, the mechanistic role of ATO resistance in MES GBM was explored. In GBM cells, ATO-activated translation initiation cellular events via the MNK1-eIF4E signaling axis. Furthermore, resistance to ATO in intracranial PDX tumors correlated with high eIF4E phosphorylation. Polysomal fractionation and microarray analysis of GBM cells were performed to identify ATO's effect on mRNA translation and enrichment of anti-apoptotic mRNAs in the ATO-induced translatome was found. Additionally, it was determined that MNK inhibition sensitized MES GSCs to ATO in neurosphere and apoptosis assays. Finally, examination of the effect of ATO on patients from a phase I/II clinical trial of ATO revealed that PN GBM patients responded better to ATO than other subtypes as demonstrated by longer overall and progression-free survival.Implications: These findings raise the possibility of a unique therapeutic approach for GBM, involving MNK1 targeting to sensitize MES GSCs to drugs like arsenic trioxide. Mol Cancer Res; 16(1); 32-46. ©2017 AACR.

Arsenic Triglutathione [As(GS)3] Transport by Multidrug Resistance Protein 1 (MRP1/ABCC1) Is Selectively Modified by Phosphorylation of Tyr920/Ser921 and Glycosylation of Asn19/Asn23

The ATP-binding cassette (ABC) transporter multidrug resistance protein 1 (MRP1/ABCC1) is responsible for the cellular export of a chemically diverse array of xenobiotics and endogenous compounds. Arsenic, a human carcinogen, is a high-affinity MRP1 substrate as arsenic triglutathione [As(GS)3]. In this study, marked differences in As(GS)3 transport kinetics were observed between MRP1-enriched membrane vesicles prepared from human embryonic kidney 293 (HEK) (Km 3.8 µM and Vmax 307 pmol/mg per minute) and HeLa (Km 0.32 µM and Vmax 42 pmol/mg per minute) cells. Mutant MRP1 lacking N-linked glycosylation [Asn19/23/1006Gln; sugar-free (SF)-MRP1] expressed in either HEK293 or HeLa cells had low Km and Vmax values for As(GS)3, similar to HeLa wild-type (WT) MRP1. When prepared in the presence of phosphatase inhibitors, both WT- and SF-MRP1-enriched membrane vesicles had a high Km value for As(GS)3 (3-6 µM), regardless of the cell line. Kinetic parameters of As(GS)3 for HEK-Asn19/23Gln-MRP1 were similar to those of HeLa/HEK-SF-MRP1 and HeLa-WT-MRP1, whereas those of single glycosylation mutants were like those of HEK-WT-MRP1. Mutation of 19 potential MRP1 phosphorylation sites revealed that HEK-Tyr920Phe/Ser921Ala-MRP1 transported As(GS)3 like HeLa-WT-MRP1, whereas individual HEK-Tyr920Phe- and -Ser921Ala-MRP1 mutants were similar to HEK-WT-MRP1. Together, these results suggest that Asn19/Asn23 glycosylation and Tyr920/Ser921 phosphorylation are responsible for altering the kinetics of MRP1-mediated As(GS)3 transport. The kinetics of As(GS)3 transport by HEK-Asn19/23Gln/Tyr920Glu/Ser921Glu were similar to HEK-WT-MRP1, indicating that the phosphorylation-mimicking substitutions abrogated the influence of Asn19/23Gln glycosylation. Overall, these data suggest that cross-talk between MRP1 glycosylation and phosphorylation occurs and that phosphorylation of Tyr920 and Ser921 can switch MRP1 to a lower-affinity, higher-capacity As(GS)3 transporter, allowing arsenic detoxification over a broad concentration range.

Resveratrol enhances the suppressive effects of arsenic trioxide on primitive leukemic progenitors

Efforts to enhance the antileukemic properties of arsenic trioxide are clinically relevant and may lead to the development of new therapeutic approaches for the management of certain hematological malignancies. We provide evidence that concomitant treatment of acute myeloid leukemia (AML) cells or chronic myeloid leukemia (CML) cells with resveratrol potentiates arsenic trioxide-dependent induction of apoptosis. Importantly, clonogenic assays in methylcellulose demonstrate potent suppressive effects of the combination of these agents on primitive leukemic progenitors derived from patients with AML or CML. Taken together, these findings suggest that combinations of arsenic trioxide with resveratrol may provide an approach for targeting of early leukemic precursors and, possibly, leukemia initiating stem cells.

Regulatory effects of sestrin 3 (SESN3) in BCR-ABL expressing cells

Chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL) are characterized by the presence of the BCR-ABL oncoprotein, which leads to activation of a plethora of pro-mitogenic and pro-survival pathways, including the mTOR signaling cascade. We provide evidence that in BCR-ABL expressing cells, treatment with tyrosine kinase inhibitors (TKIs) results in upregulation of mRNA levels and protein expression of sestrin3 (SESN3), a unique cellular inhibitor of mTOR complex 1 (mTORC1). Such upregulation appears to be mediated by regulatory effects on mTOR, as catalytic inhibition of the mTOR kinase also induces SESN3. Catalytic mTOR inhibition also results in upregulation of SESN3 expression in cells harboring the TKI-insensitive T315I-BCR-ABL mutant, which is resistant to imatinib mesylate. Overexpression of SESN3 results in inhibitory effects on different Ph+ leukemic cell lines including KT-1-derived leukemic precursors, indicating that SESN3 mediates anti-leukemic responses in Ph+ cells. Altogether, our findings suggest the existence of a novel mechanism for the generation of antileukemic responses in CML cells, involving upregulation of SESN3 expression.

An ASK1-p38 signalling pathway mediates hydrogen peroxide-induced toxicity in NG108-15 neuronal cells

Reactive oxygen species (ROS) are believed to be involved in many forms of neurodegeneration, including ischaemic infarct damage and Alzheimer's disease. Despite the known involvement of p38 and JNK MAP kinases in mediating apoptosis and cell death in a variety of cell types, the details of the signalling pathways activated in neuronal cells by ROS are poorly characterised. Recently TAK1 (MAP3K7), a kinase upstream of JNK and p38, has attracted attention as a possible mediator of ischaemic cell death. This study tested the hypothesis that hydrogen peroxide (H2O2), which produces ROS, induces apoptosis in the NG108-15 neuronal cell line via activation of either TAK1 or the related kinase ASK1 (MAP3K5). H2O2 caused a concentration-dependent reduction in cell viability associated with caspase 3 activation. Loss of cell viability was inhibited by a selective caspase 3 inhibitor, and by the p38 inhibitor SB203580, but was not affected by the JNK inhibitor SP600125. The selective TAK1 inhibitor 5Z-7-oxozeaenol (5Z-7) exacerbated the loss of cell viability, whereas the ASK1 inhibitor NQDI-1 completely prevented caspase activation and cell death. These results show that pharmacological inhibition of ASK1 is neuroprotective, implicating an ASK1-p38 signalling pathway in ROS-induced apoptosis in neurones. The results also imply that the role of TAK1 may be neuroprotective rather than pro-degenerative.

Regulation of the kinase RSK1 by arsenic trioxide and generation of antileukemic responses

Arsenic Trioxide (As₂O₃) is one of the most effective agents in the treatment of acute promyelocytic leukemia (APL), but has no significant efficacy in other forms of AML. The mechanisms of relative resistance of non-APL cells are not well understood, but emerging evidence suggests that activation of negative feedback regulatory loops and pathways contributes to such resistance. We provide evidence that a signaling cascade involving the kinase RSK1 is engaged in a negative feedback manner during arsenic-treatment of cells and exhibits regulatory effects on growth and survival of AML cells in response to treatment with As₂O₃. Our data demonstrate that pharmacological inhibition or molecular disruption of expression of RSK1 enhances As₂O₃-dependent apoptosis and/or growth inhibition of AML cells. Importantly, combination of a pharmacological inhibitor of RSK and As₂O₃ results in enhanced suppression of primary AML leukemic progenitors. Altogether, our findings suggest an important regulatory role for RSK1 in the generation of the effects of As₂O₃ in AML cells. They also raise the potential of RSK1 targeting in combination with As₂O₃ as a novel approach to promote antileukemic responses.

Positive transforming growth factor-β activated kinase-1 expression has an unfavorable impact on survival in T3N1-3M0 esophageal squamous cell carcinomas

BACKGROUND

Transforming growth factor-β activated kinase-1 (TAK1) is a serine/threonine kinase in the mitogen-activated protein kinase kinase family. Previous studies have reported the role of TAK1 in cancer occurrence and progression; however, its role and clinical significance in esophageal squamous cell carcinoma (ESCC) has not been elucidated. We investigated the correlation of TAK1 expression and clinical outcome in T3N1-3M0 surgically resected ESCCs.

METHODS

Tissue microarrays constructed of 234 surgically resected T3N1-3M0 ESCC primary tumors were used for TAK1 evaluation by immunohistochemistry. The clinical and prognostic significance of TAK1 expression was analyzed statistically.

RESULTS

Positive expression of TAK1 was observed in 38.5% (90 of 234). The expression level of TAK1 in ESCCs at stage N2-3 was significantly higher than the expression level in those at stage N1 (p = 0.041). Patients with negative TAK1 expression demonstrated better overall survival than those with positive expression (median, 22.7 vs 17.4 months; p = 0.023). Multivariate analysis showed that TAK1 expression was an independent prognostic factor in ESCC (relative risk, 1.429; p = 0.021).

CONCLUSIONS

TAK1 expression correlates with lymph node metastasis and is a negative, independent prognostic factor in resected T3N1-3M0 ESCCs.