DUSP16 is an epigenetically regulated determinant of JNK signalling in Burkitt's lymphoma
ABSTRACT The mitogen-activated protein kinase (MAPK) phosphatases or dual specificity phosphatases (DUSPs) are a family of proteins that catalyse the inactivation of MAPK in eukaryotic cells. Little is known of the expression, regulation or function of the DUSPs in human neoplasia.
We used RT-PCR and quantitative PCR (qPCR) to examine the expression of DUSP16 mRNA. The methylation in the DUSP16 CpG island was analysed using bisulphite sequencing and methylation-specific PCR. The activation of MAPK was determined using western blotting with phospho-specific antibodies for extra-cellular signal-related kinase (ERK), p38 and c-Jun N-terminal kinase (JNK). The proliferation of cell lines was assessed using the CellTiter 96 Aqueous One assay.
The expression of DUSP16, which inactivates MAPK, is subject to methylation-dependent transcriptional silencing in Burkitt's Lymphoma (BL) cell lines and in primary BL. The silencing is associated with aberrant methylation in the CpG island in the 5' regulatory sequences of the gene blocking its constitutive expression. In contrast to BL, the CpG island of DUSP16 is unmethylated in other non-Hodgkin's lymphomas (NHLs) and epithelial malignancies. In BL cell lines, neither constitutive nor inducible ERK or p38 activity varied significantly with DUSP16 status. However, activation of JNK was increased in lines with DUSP16 methylation. Furthermore, methylation in the DUSP16 CpG island blocked transcriptional induction of DUSP16, thereby abrogating a normal physiological negative feedback loop that limits JNK activity, and conferred increased cellular sensitivity to agents, such as sorbitol and anthracycline chemotherapeutic agents that activate JNK.
DUSP16 is a new epigenetically regulated determinant of JNK activation in BL.
Full-textDOI: · Available from: Eleftheria Hatzimichael, May 29, 2015
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ABSTRACT: Genetic and epigenetic alterations are essential for the initiation and progression of human cancer. We previously reported that primary human medulloblastomas showed extensive cancer-specific CpG island DNA hypermethylation in critical developmental pathways. To determine whether genetically engineered mouse models (GEMMs) of medulloblastoma have comparable epigenetic changes, we assessed genome-wide DNA methylation in three mouse models of medulloblastoma. In contrast to human samples, very few loci with cancer-specific DNA hypermethylation were detected, and in almost all cases the degree of methylation was relatively modest compared with the dense hypermethylation in the human cancers. To determine if this finding was common to other GEMMs, we examined a Burkitt lymphoma and breast cancer model and did not detect promoter CpG island DNA hypermethylation, suggesting that human cancers and at least some GEMMs are fundamentally different with respect to this epigenetic modification. These findings provide an opportunity to both better understand the mechanism of aberrant DNA methylation in human cancer and construct better GEMMs to serve as preclinical platforms for therapy development.Epigenetics: official journal of the DNA Methylation Society 10/2013; 8(12). DOI:10.4161/epi.26486 · 5.11 Impact Factor
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ABSTRACT: Type 1 diabetes (T1D) is an autoimmune disease with a strong inflammatory component. The cytokines interleukin-1β and interferon-γ contribute to beta cell apoptosis in T1D. These cytokines induce endoplasmic reticulum stress and the unfolded protein response (UPR), contributing to loss of beta cells. IRE1α, one of the UPR mediators, triggers insulin degradation and inflammation in beta cells and is critical for the transition from ″physiological″ to ″pathological″ UPR. The mechanisms regulating IRE1α activation, and its signalling for beta cell ″adaptation″, ″stress response″ or ″apoptosis″ remain to be clarified. To address these questions we combined MAPPIT (MAmmalian Protein-Protein Interaction Trap)-based IRE1α interactome and functional genomic analysis of human and rodent beta cells exposed to pro-inflammatory cytokines to identify novel cytokine-induced regulators of IRE1α. Based on this approach, we identified N-myc interactor (NMI) as an IRE1α-interacting/modulator protein in rodent and human pancreatic beta cells. An increased expression of NMI was detected in islets from non-obese diabetic (NOD) mice with insulitis, and in rodent or human beta cells exposed in vitro to the pro-inflammatory cytokines interleukin-1β and interferon-γ. Detailed mechanistic studies demonstrated that NMI negatively modulates IRE1α-dependent activation of JNK and apoptosis in rodent and human pancreatic beta cells. In conclusion, by using a combined omics approach, we identified NMI induction as a novel negative feedback mechanism that decreases IRE1α-dependent activation of JNK and apoptosis in cytokine-exposed beta cells.
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ABSTRACT: Several dual-specificity phosphatases (DUSPs) that play key roles in the direct or indirect inactivation of different MAP kinases (MAPKs) have been implicated in human cancers over the past decade. This has led to a growing interest in identifying DUSPs and their specific inhibitors for further testing and validation as therapeutic targets in human cancers. However, the lack of understanding of the complex regulatory mechanisms and cross-talks between MAPK signaling pathways, combined with the fact that DUSPs can act as a double-edged sword in cancer progression, calls for a more careful and thorough investigation. Among the various types of brain cancer, glioblastoma multiforme (GBM) is notorious for its aggressiveness and resistance to current treatment modalities. This has led to the search for new molecular targets, particularly those involving various signaling pathways. DUSPs appear to be a promising target, but much more information on DUSP targets and their effects on GBM is needed before potential therapies can be developed, tested, and validated. This review identifies and summarizes the specific roles of DUSP1, DUSP4, DUSP6 and DUSP26 that have been implicated in GBM.Cell Biology International 02/2014; 38(2). DOI:10.1002/cbin.10201 · 1.64 Impact Factor