Regulation of phosphoglucose isomerase/autocrine motility factor activities by the poly(ADP-ribose) polymerase family-14

Cannabinoids induce cell death in leukaemic cells through Parthanatos and PARP-related metabolic disruptions

BACKGROUND

Several studies have described a potential anti-tumour effect of cannabinoids (CNB). CNB receptor 2 (CB2) is mostly present in hematopoietic stem cells (HSC). The present study evaluates the anti-leukaemic effect of CNB.

METHODS

Cell lines and primary cells from acute myeloid leukaemia (AML) patients were used and the effect of the CNB derivative WIN-55 was evaluated in vitro, ex vivo and in vivo.

RESULTS

We demonstrate a potent antileukemic effect of WIN-55 which is abolished with CB antagonists. WIN-treated mice, xenografted with AML cells, had better survival as compared to vehicle or cytarabine. DNA damage-related genes were affected upon exposure to WIN. Co-incubation with the PARP inhibitor Olaparib prevented WIN-induced cell death, suggesting PARP-mediated apoptosis which was further confirmed with the translocation of AIF to the nucleus observed in WIN-treated cells. Nicotinamide prevented WIN-related apoptosis, indicating NAD+ depletion. Finally, WIN altered glycolytic enzymes levels as well as the activity of G6PDH. These effects are reversed through PARP1 inhibition.

CONCLUSIONS

WIN-55 exerts an antileukemic effect through Parthanatos, leading to translocation of AIF to the nucleus and depletion of NAD+, which are reversed through PARP1 inhibition. It also induces metabolic disruptions. These effects are not observed in normal HSC.

Oncometabolism: A Paradigm for the Metabolic Remodeling of the Failing Heart

Heart failure is associated with profound alterations in cardiac intermediary metabolism. One of the prevailing hypotheses is that metabolic remodeling leads to a mismatch between cardiac energy (ATP) production and demand, thereby impairing cardiac function. However, even after decades of research, the relevance of metabolic remodeling in the pathogenesis of heart failure has remained elusive. Here we propose that cardiac metabolic remodeling should be looked upon from more perspectives than the mere production of ATP needed for cardiac contraction and relaxation. Recently, advances in cancer research have revealed that the metabolic rewiring of cancer cells, often coined as oncometabolism, directly impacts cellular phenotype and function. Accordingly, it is well feasible that the rewiring of cardiac cellular metabolism during the development of heart failure serves similar functions. In this review, we reflect on the influence of principal metabolic pathways on cellular phenotype as originally described in cancer cells and discuss their potential relevance for cardiac pathogenesis. We discuss current knowledge of metabolism-driven phenotypical alterations in the different cell types of the heart and evaluate their impact on cardiac pathogenesis and therapy.

Exome hits demystified: The next frontier

Severe mental illnesses such as schizophrenia and bipolar disorder have complex inheritance patterns, involving both common and rare variants. Whole exome sequencing is a promising approach to find out the rare genetic variants. We had previously reported several rare variants in multiplex families with severe mental illnesses. The current article tries to summarise the biological processes and pattern of expression of genes harbouring the aforementioned variants, linking them to known clinical manifestations through a methodical narrative review. Of the 28 genes considered for this review from 7 families with multiple affected individuals, 6 genes are implicated in various neuropsychiatric manifestations including some variations in the brain morphology assessed by magnetic resonance imaging. Another 15 genes, though associated with neuropsychiatric manifestations, did not have established brain morphological changes whereas the remaining 7 genes did not have any previously recorded neuropsychiatric manifestations at all. Wnt/b-catenin signaling pathway was associated with 6 of these genes and PI3K/AKT, calcium signaling, ERK, RhoA and notch signaling pathways had at least 2 gene associations. We present a comprehensive review of biological and clinical knowledge about the genes previously reported in multiplex families with severe mental illness. A 'disease in dish approach' can be helpful to further explore the fundamental mechanisms.

Autocrine motility factor and its receptor expression in musculoskeletal tumors

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Discovery of Autocrine Motility factor (AMF) and its receptor (AMFR), both triggering tumor invasion and metastasis, may alter the therapeutic concept.

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Here, in this review, we show a novel outlook suggesting a cross-talking between musculoskeletal tumors and the skeletal milieu regulated by AMF-AMFR signaling.

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This review will highlight the pharmacological need for AMF and AMFR inhibitors for patients with malignant musculoskeletal tumors.

Management of aggressive malignant musculoskeletal tumors is clinically challenging and awaits the identification of regulator(s) that can be therapeutically used to improve patient outcome. Autocrine motility factor (AMF), a secreted cytokine, is known to alter the bone microenvironment by linking to its receptor AMFR (AMF Receptor), leading to tumor progression. It was noted that both the ligand and its receptor belong to the moonlighting family of proteins, as they contribute to intracellular metabolic function such as glycolysis and gluconeogenesis by expressing glucose-6-phosphate isomerase AMF/GPI and higher protein degradation by expressing AMFR/gp78 functioning as ubiquitin ligase activity. Thus, AMF/GPI and AMFR/gp78 contribute to higher metabolic turnover of protein and glucose. Recently, a large-scale cohort study including 23 different histological types of musculoskeletal tumors revealed that patients with osteosarcoma, multiple myeloma, rhabdomyosarcoma, and angiosarcoma tend to express higher levels of AMF, whereas multiple myeloma patients expressed high levels of AMFR. Consistently, the cellular data showed that a variety of musculoskeletal tumors express AMF and components of bone microenvironment express AMFR. Thus, a novel outlook suggests a cellular link and cross-talk between musculoskeletal tumors and the skeletal milieu are regulated by AMF-AMFR signaling. This review will highlight the pharmacological need for AMF and AMFR inhibitors as unmet medical needs for patients with malignant musculoskeletal tumors.

Autocrine motility factor secreted by HeLa cells inhibits the growth of many cancer cells by regulating AKT/ERK signaling

In cell competition, a secreted death signal can determine cell fate. However, the nature of such a signal remains unclear. In this study, conditioned medium from HeLa cells (HeLa CM) inhibited growth of A549 and MCF-7 cells. Through HeLa CM fractionation, glucose 6-phosphate isomerase/autocrine motility factor (GPI/AMF) was identified as the main growth inhibitor. Previously, AMF was known for its mitogenic, motogenic, and differentiation functions and was implicated in tumor progression and metastasis. HeLa CM lost its growth inhibitory property after treatment with erythrose-4-phosphate (E4P) or anti-GPI antibody. Purified HeLa recombinant AMF (rAMF) proteins inhibited the growth of A549, MDA-MB-232, MCF-7, AsPC-1, DU145, Hep-2, Hep G2, and HT-29 cells. However, growth of HL-60, SKOV3, U-87 MG, SNU-484, U-87 MG, and 3T3-L1 cells was little affected. In a Transwell assay, HeLa rAMF effectively reduced A549 cell migration and invasion. HeLa rAMF effectively induced apoptosis in A549 cells, apparently by reducing the levels of Bcl-2, GPI, and poly(ADP-ribose) polymerase (PARP)14 and activating caspase-3 and p53. HeLa rAMF antagonized HER2 and the AMF receptor (AMFR or GP78) in relation to the AKT/EKT signaling pathway. These results suggest that HeLa AMF could act as a diffusible death signal that could induce cancer cell-selective growth inhibition and apoptosis.

The role of ADP-ribose metabolism in metabolic regulation, adipose tissue differentiation, and metabolism

In this review, Szanto et al. summarize the metabolic regulatory roles of PARP enzymes and their associated pathologies.

Poly(ADP-ribose) polymerases (PARPs or ARTDs), originally described as DNA repair factors, have metabolic regulatory roles. PARP1, PARP2, PARP7, PARP10, and PARP14 regulate central and peripheral carbohydrate and lipid metabolism and often channel pathological disruptive metabolic signals. PARP1 and PARP2 are crucial for adipocyte differentiation, including the commitment toward white, brown, or beige adipose tissue lineages, as well as the regulation of lipid accumulation. Through regulating adipocyte function and organismal energy balance, PARPs play a role in obesity and the consequences of obesity. These findings can be translated into humans, as evidenced by studies on identical twins and SNPs affecting PARP activity.

Regulatory Molecules and Corresponding Processes of BCR-ABL Protein Degradation

The BCR-ABL fusion protein with strong tyrosine kinase activity is one of the molecular biological bases of leukemia. Imatinib (Gleevec), a specific targeted drug for the treatment of chronic myeloid leukemia (CML), was developed for inhibiting the kinase activity of the BCR-ABL fusion protein. Despite the positive clinical efficacy of imatinib, the proportion of imatinib resistance has gradually increased. The main reason for the resistance is a decrease in sensitivity to imatinib caused by mutation or amplification of the BCR-ABL gene. In response to this phenomenon, the new generation of tyrosine kinase inhibitors (TKIs) targeting the BCR-ABL fusion protein was developed to solve the problem. However this strategy only selectively inhibits the tyrosine kinase activity of the BCR-ABL protein without eliminating the BCR-ABL protein, it does not fundamentally cure the BCR-ABL-positive leukemia patients. With the accumulation of the knowledge of cellular molecular biology, it has become possible to specifically eliminate certain proteins by cellular proteases in a specific way. Therefore, the therapeutic strategy to induce the degradation of the BCR-ABL fusion protein is superior to the strategy of inhibiting its activity. The protein degradation strategy is also a solution to the TKI resistance caused by different BCR-ABL gene point mutations. In order to provide possible exploration directions and clues for eliminating the BCR-ABL fusion protein in tumor cells, we summarize the significant molecules involved in the degradation pathway of the BCR-ABL protein, as well as the reported potent compounds that can target the BCR-ABL protein for degradation.

ADP-ribosylation signalling and human disease

ADP-ribosylation (ADPr) is a reversible post-translational modification of proteins, which controls major cellular and biological processes, including DNA damage repair, cell proliferation and differentiation, metabolism, stress and immune responses. In order to maintain the cellular homeostasis, diverse ADP-ribosyl transferases and hydrolases are involved in the fine-tuning of ADPr systems. The control of ADPr network is vital, and dysregulation of enzymes involved in the regulation of ADPr signalling has been linked to a number of inherited and acquired human diseases, such as several neurological disorders and in cancer. Conversely, the therapeutic manipulation of ADPr has been shown to ameliorate several disorders in both human and animal models. These include cardiovascular, inflammatory, autoimmune and neurological disorders. Herein, we summarize the recent findings in the field of ADPr, which support the impact of this modification in human pathophysiology and highlight the curative potential of targeting ADPr for translational and molecular medicine.

PARP14 promotes the proliferation and gemcitabine chemoresistance of pancreatic cancer cells through activation of NF-κB pathway

Pancreatic cancer (PC) is the most fatal gastrointestinal malignancy in the world, with a 5-year relative survival of only 8%. Poly(ADP-ribose) polymerase (PARP)14, a member of the macro-PARP subfamily proteins, has been reported to participate in various biologic and pathologic processes in multiple cancers. The roles and underlying molecular mechanisms of PARP14 in PC carcinogenesis, however, remain to be elucidated. In this study, we for the first time discovered that PARP14 was highly expressed in human primary PC specimens and significantly correlated with poor patient prognosis. Using loss-of-function studies in vitro and in vivo, we showed that the knockdown of PARP14 led to enhanced apoptosis, repressed proliferation, and gemcitabine (GEM) resistance of PC cells. Further investigations revealed that PARP14 was significantly overexpressed in GEM-resistant PC cells (SW1990/GZ). And silencing of PARP14 significantly reversed the GEM resistance of SW1990/GZ cells. To the mechanism, PARP14 could stimulate PC progression by the activation of nuclear factor-κB (NF-κB) signaling pathway. And inhibition of NF-κB signal could significantly reverse PARP14-overexpression triggered PC carcinogenesis. In conclusion, PARP14 could promote PC cell proliferation, antiapoptosis, and GEM resistance via NF-κB signaling pathway, highlighting its potential role as a therapeutic target for PC.

A macrodomain-linked immunosorbent assay (MLISA) for mono-ADP-ribosyltransferases

ADP-ribosyltransferases (ARTs) catalyze reversible additions of mono- and poly-ADP-ribose onto diverse types of proteins by using nicotinamide adenine dinucleotide (NAD⁺) as a cosubstrate. In the human ART superfamily, 14 out of 20 members are shown to catalyze endogenous protein mono-ADP-ribosylation and play important roles in regulating various physiological and pathophysiological processes. Identification of new modulators of mono-ARTs can thus potentially lead to discovery of novel therapeutics. In this study, we developed a macrodomain-linked immunosorbent assay (MLISA) for characterizing mono-ARTs. Recombinant macrodomain 2 from poly-ADP-ribose polymerase 14 (PARP14) was generated with a C-terminal human influenza hemagglutinin (HA) tag for detecting mono-ADP-ribosylated proteins. Coupled with an anti-HA secondary antibody, the generated HA-tagged macrodomain 2 reveals high specificity for mono-ADP-ribosylation catalyzed by distinct mono-ARTs. Kinetic parameters of PARP15-catalyzed automodification were determined by MLISA and are in good agreement with previous studies. Eight commonly used chemical tools for PARPs were examined by MLISA with PARP15 and PARP14 in 96-well plates and exhibited moderate inhibitory activities for PARP15, consistent with published reports. These results demonstrate that MLISA provides a new and convenient method for quantitative characterization of mono-ART enzymes and may allow identification of potent mono-ART inhibitors in a high-throughput-compatible manner.

PARP14 promotes the Warburg effect in hepatocellular carcinoma by inhibiting JNK1-dependent PKM2 phosphorylation and activation

Most tumour cells use aerobic glycolysis (the Warburg effect) to support anabolic growth and evade apoptosis. Intriguingly, the molecular mechanisms that link the Warburg effect with the suppression of apoptosis are not well understood. In this study, using loss-of-function studies in vitro and in vivo, we show that the anti-apoptotic protein poly(ADP-ribose) polymerase (PARP)14 promotes aerobic glycolysis in human hepatocellular carcinoma (HCC) by maintaining low activity of the pyruvate kinase M2 isoform (PKM2), a key regulator of the Warburg effect. Notably, PARP14 is highly expressed in HCC primary tumours and associated with poor patient prognosis. Mechanistically, PARP14 inhibits the pro-apoptotic kinase JNK1, which results in the activation of PKM2 through phosphorylation of Thr365. Moreover, targeting PARP14 enhances the sensitization of HCC cells to anti-HCC agents. Our findings indicate that the PARP14-JNK1-PKM2 regulatory axis is an important determinant for the Warburg effect in tumour cells and provide a mechanistic link between apoptosis and metabolism.

DTX3L and ARTD9 inhibit IRF1 expression and mediate in cooperation with ARTD8 survival and proliferation of metastatic prostate cancer cells

Background

Prostate cancer (PCa) is one of the leading causes of cancer-related mortality and morbidity in the aging male population and represents the most frequently diagnosed malignancy in men around the world. The Deltex (DTX)-3-like E3 ubiquitin ligase (DTX3L), also known as B-lymphoma and BAL-associated protein (BBAP), was originally identified as a binding partner of the diphtheria-toxin-like macrodomain containing ADP-ribosyltransferase-9 (ARTD9), also known as BAL1 and PARP9. We have previously demonstrated that ARTD9 acts as a novel oncogenic survival factor in high-risk, chemo-resistant, diffuse large B cell lymphoma (DLBCL). The mono-ADP-ribosyltransferase ARTD8, also known as PARP14 functions as a STAT6-specific co-regulator of IL4-mediated proliferation and survival in B cells.

Methods

Co-expression of DTX3L, ARTD8, ARTD9 and STAT1 was analyzed in the metastatic PCa (mPCa) cell lines PC3, DU145, LNCaP and in the normal prostate luminal epithelial cell lines HPE and RWPE1. Effects on cell proliferation, survival and cell migration were determined in PC3, DU145 and/or LNCaP cells depleted of DTX3L, ARTD8, ARTD9, STAT1 and/or IRF1 compared to their proficient control cells, respectively. In further experiments, real-time RT-PCR, Western blot, immunofluorescence and co-immunoprecipitations were conducted to evaluate the physical and functional interactions between DTX3L, ARTD8 and ARTD9.

Results

Here we could identify DTX3L, ARTD9 and ARTD8 as novel oncogenic survival factors in mPCa cells. Our studies revealed that DTX3L forms a complex with ARTD8 and mediates together with ARTD8 and ARTD9 proliferation, chemo-resistance and survival of mPCa cells. In addition, DTX3L, ARTD8 and ARTD9 form complexes with each other. Our study provides first evidence that the enzymatic activity of ARTD8 is required for survival of mPCa cells. DTX3L and ARTD9 act together as repressors of the tumor suppressor IRF1 in mPCa cells. Furthermore, the present study shows that DTX3L together with STAT1 and STAT3 is implicated in cell migration of mPCa cells.

Conclusions

Our data strongly indicate that a crosstalk between STAT1, DTX3L and ARTD-like mono-ADP-ribosyltransferases mediates proliferation and survival of mPCa cells. The present study further suggests that the combined targeted inhibition of STAT1, ARTD8, ARTD9 and/or DTX3L could increase the efficacy of chemotherapy or radiation treatment in prostate and other high-risk tumor types with an increased STAT1 signaling.

Improved functional expression of human cardiac kv1.5 channels and trafficking-defective mutants by low temperature treatment

We herein investigated the effect of low temperature exposure on the expression, degradation, localization and activity of human Kv1.5 (hKv1.5). In hKv1.5-expressing CHO cells, the currents were significantly increased when cultured at a reduced temperature (28°C) compared to those observed at 37°C. Western blot analysis indicated that the protein levels (both immature and mature proteins) of hKv1.5 were significantly elevated under the hypothermic condition. Treatment with a proteasome inhibitor, MG132, significantly increased the immature, but not the mature, hKv1.5 protein at 37°C, however, there were no changes in either the immature or mature hKv1.5 proteins at low temperature following MG132 exposure. These observations suggest that the enhancement of the mature hKv1.5 protein at reduced temperature may not result from the inhibition of proteolysis. Moreover, the hKv1.5 fluorescence signal in the cells increased significantly on the cell surface at 28°C versus those cultured at 37°C. Importantly, the low temperature treatment markedly shifted the subcellular distribution of the mature hKv1.5, which showed considerable overlap with the trans-Golgi component. Experiments using tunicamycin, an inhibitor of N-glycosylation, indicated that the N-glycosylation of hKv1.5 is more effective at 28°C than at 37°C. Finally, the hypothermic treatment also rescued the protein expression and currents of trafficking-defective hKv1.5 mutants. These results indicate that low temperature exposure stabilizes the protein in the cellular organelles or on the plasma membrane, and modulates its maturation and trafficking, thus enhancing the currents of hKv1.5 and its trafficking defect mutants.

A systematic analysis of the PARP protein family identifies new functions critical for cell physiology

The poly(ADP-ribose) polymerase (PARP) family of proteins use NAD⁺ as their substrate to modify acceptor proteins with adenosine diphosphate-ribose (ADPr) modifications. The function of most PARPs under physiological conditions is unknown. Here, to better understand this protein family, we systematically analyze the cell cycle localization of each PARP and of poly(ADP-ribose), a product of PARP activity, then identify the knock-down phenotype of each protein and perform secondary assays to elucidate function. We show that most PARPs are cytoplasmic, identify cell cycle differences in the ratio of nuclear to cytoplasmic poly(ADP-ribose), and identify four phenotypic classes of PARP function. These include the regulation of membrane structures, cell viability, cell division, and the actin cytoskeleton. Further analysis of PARP14 shows that it is a component of focal adhesion complexes required for proper cell motility and focal adhesion function. In total, we show that PARP proteins are critical regulators of eukaryotic physiology.

Poly(ADP-ribose) polymerase family member 14 (PARP14) is a novel effector of the JNK2-dependent pro-survival signal in multiple myeloma

Regulation of cell survival is a key part of the pathogenesis of multiple myeloma (MM). Jun N-terminal kinase (JNK) signaling has been implicated in MM pathogenesis, but its function is unclear. To elucidate the role of JNK in MM, we evaluated the specific functions of the two major JNK proteins, JNK1 and JNK2. We show here that JNK2 is constitutively activated in a panel of MM cell lines and primary tumors. Using loss-of-function studies, we demonstrate that JNK2 is required for the survival of myeloma cells and constitutively suppresses JNK1-mediated apoptosis by affecting expression of poly(ADP-ribose) polymerase (PARP)14, a key regulator of B-cell survival. Strikingly, we found that PARP14 is highly expressed in myeloma plasma cells and associated with disease progression and poor survival. Overexpression of PARP14 completely rescued myeloma cells from apoptosis induced by JNK2 knockdown, indicating that PARP14 is critically involved in JNK2-dependent survival. Mechanistically, PARP14 was found to promote the survival of myeloma cells by binding and inhibiting JNK1. Moreover, inhibition of PARP14 enhances the sensitization of MM cells to anti-myeloma agents. Our findings reveal a novel regulatory pathway in myeloma cells through which JNK2 signals cell survival via PARP14, and identify PARP14 as a potential therapeutic target in myeloma.

A role of intracellular mono-ADP-ribosylation in cancer biology

During the development, progression and dissemination of neoplastic lesions, cancer cells can hijack normal pathways and mechanisms. This includes the control of the function of cellular proteins through reversible post-translational modifications, such as ADP-ribosylation, phosphorylation, and acetylation. In the case of mono-ADP-ribosylation and poly-ADP-ribosylation, the addition of one or several units of ADP-ribose to target proteins occurs via two families of enzymes that can generate ADP-ribosylated proteins: the diphtheria toxin-like ADP-ribosyltransferase (ARTD) family, comprising 17 different proteins that are either poly-ADP-ribosyltransferases or mono-ADP-ribosyltransferases or inactive enzymes; and the clostridial toxin-like ADP-ribosyltransferase family, with four human members, two of which are active mono-ADP-ribosyltransferases, and two of which are enzymatically inactive. In line with a central role for poly-ADP-ribose polymerase 1 in response to DNA damage, specific inhibitors of this enzyme have been developed as anticancer therapeutics and evaluated in several clinical trials. Recently, in combination with the discovery of a large number of enzymes that can catalyse mono-ADP-ribosylation, the role of this modification has been linked to human diseases, such as inflammation, diabetes, neurodegeneration, and cancer, thus revealing the need for the development of specific ARTD inhibitors. This will provide a better understanding of the roles of these enzymes in human physiology and pathology, so that they can be targeted in the future to generate new and efficacious drugs. This review summarizes our present knowledge of the ARTD enzymes that are involved in mono-ADP-ribosylation reactions and that have roles in cancer biology. In particular, the well-documented role of macro-containing ARTD8 in lymphoma and the putative role of ARTD15 in cancer are discussed.

Macro domains as metabolite sensors on chromatin

How metabolism and epigenetics are molecularly linked and regulate each other is poorly understood. In this review, we will discuss the role of direct metabolite-binding to chromatin components and modifiers as a possible regulatory mechanism. We will focus on globular macro domains, which are evolutionarily highly conserved protein folds that can recognize NAD(+)-derived metabolites. Macro domains are found in histone variants, histone modifiers, and a chromatin remodeler among other proteins. Here we summarize the macro domain-containing chromatin proteins and the enzymes that generate relevant metabolites. Focusing on the histone variant macroH2A, we further discuss possible implications of metabolite binding for chromatin function.

BAL1/ARTD9 represses the anti-proliferative and pro-apoptotic IFNγ-STAT1-IRF1-53 axes in diffuse large B-cell lymphoma

The B-aggressive lymphoma-1 protein and ADP-ribosyltransferase BAL1/ARTD9 has been recently identified as a novel risk-related gene product in aggressive diffuse large B-cell lymphoma (DLBCL). BAL1 is constitutively expressed in a subset of high-risk DLBCL with an active host inflammatory response and suggested to be associated with interferon related gene expression. Here we identify BAL1 as a novel oncogenic survival factor in DLBCL and show that constitutive overexpression of BAL1 in DLBCL tightly associates with intrinsic interferon-gamma (IFNγ) signaling and constitutive activity of signal transducer and activator of transcription (STAT)-1. Remarkably, BAL1 stimulates the phosphorylation of both STAT1 isoforms STAT1α and STAT1β, on Y701 and thereby promoting the nuclear accumulation of the antagonistically acting and transcriptionally repressive isoform STAT1β. Moreover, BAL1 physically interacts with both isoforms of STAT1, STAT1α and STAT1β through its macro domains in an ADP-ribosylation dependent manner. BAL1 directly inhibits together with STAT1β the expression of tumor suppressor and interferon response factor (IRF)-1. Conversely, BAL1 enhances the expression of the proto-oncogenes IRF2 and B-cell CLL/lymphoma (BCL)-6 in DLBCL. Our results show the first time that BAL1 represses the anti-proliferative and pro-apoptotic IFNγ-STAT1-IRF1-53 axes and mediates proliferation, survival and chemo-resistance in DLBCL. As a consequence constitutive IFNγ-STAT1 signaling does not lead to apoptosis but rather to chemo-resistance in DLBCL overexpressing BAL1. Our results suggest that BAL1 may induce an oncogenic switch in STAT1 from a tumor suppressor to an oncogene in high-risk DLBCL.

PARP6, a mono(ADP-ribosyl) transferase and a negative regulator of cell proliferation, is involved in colorectal cancer development

Poly(ADP-ribose) polymerase (PARP) is an enzyme that mediates post-translational modification of proteins. Seventeen known members of the PARP superfamily can be grouped into three classes based on catalytic activity: (i) classical poly(ADP-ribose) polymerases, (ii) mono(ADP‑ribosyl) transferases and (iii) catalytically inactive members. PARP6 belongs to the mono(ADP-ribosyl) transferase class, and here we have found that PARP6 is a negative regulator of cell proliferation. Forced expression of PARP6 in HeLa cells induced growth suppression, but a PARP6 mutant with a C-terminal deletion lacking the catalytic domain had no effect. The PARP6-expressing cells accumulated in the S-phase, and the magnitude of S-phase accumulation was observed to be greater in cells expressing a PARP6 mutant with an N-terminal deletion, lacking a putative regulatory domain. Immunohistochemical analysis revealed that PARP6 positivity was found at higher frequencies in colorectal cancer tissues with well-differentiated histology compared to those with poorly differentiated histology. Furthermore, PARP6 positivity negatively correlated with the Ki-67 proliferation index. Kaplan-Meier analysis showed that PARP6-positive colorectal cancer had a good prognosis. Based on these results, we propose that PARP6 acts as a tumor suppressor through its role in cell cycle control.

Hyperthermia reduces migration of osteosarcoma by suppression of autocrine motility factor

Autocrine motility factor (AMF) plays an important role in the development of metastasis by regulating tumor cell motility. The expression of AMF is associated with metastasis in malignant musculoskeletal tumors including osteosarcoma. Recent studies indicated that hyperthermia contributes to the improvement of the prognosis of patients with soft tissue sarcomas; however, few reports have evaluated the impact of hyperthermia on tumor cell motility, which is an important factor of metastasis. The purpose of this study was to evaluate the effect of hyperthermia with or without heat shock protein (HSP) inhibitors on the motility and AMF expression in an osteosarcoma cell line. Hyperthermia was carried out at 41°C for 24 h. According to microarray results, HSP90, HSP70 and HSP27 expression was upregulated in osteosarcoma cells under hyperthermia. The intracellular, secreted AMF, mRNA of AMF and cell motility were evaluated by western blotting, ELISA, RT-PCR, wound healing and phagokinetic track assays, respectively. The protein secretion and mRNA levels of AMF and tumor cell motility were significantly decreased by hyperthermia. Of note, the downregulated AMF expression and motility were recovered by the addition of an HSP27 inhibitor. By contrast, the HSP90 and HSP70/72/105 inhibitors had no effect on AMF expression and motility downregulated by hyperthermia. In conclusion, hyperthermia reduced AMF expression and tumor cell motility via HSP27 and may therefore be applied as osteosarcoma treatment.

Glycolytic rate and lymphomagenesis depend on PARP14, an ADP ribosyltransferase of the B aggressive lymphoma (BAL) family

Poly(ADP-ribose)polymerase (PARP)14--a member of the B aggressive lymphoma (BAL) family of macrodomain-containing PARPs--is an ADP ribosyltransferase that interacts with Stat6, enhances induction of certain genes by IL-4, and is expressed in B lymphocytes. We now show that IL-4 enhancement of glycolysis in B cells requires PARP14 and that this process is central to a role of PARP14 in IL-4-induced survival. Thus, enhancements of AMP-activated protein kinase activity restored both IL-4-induced glycolytic activity in Parp14(-/-) B cells and prosurvival signaling by this cytokine. Suppression of apoptosis is central to B-lymphoid oncogenesis, and elevated macro-PARP expression has been correlated with lymphoma aggressiveness. Strikingly, PARP14 deficiency delayed B lymphomagenesis and reversed the block to B-cell maturation driven by the Myc oncogene. Collectively, these findings reveal links between a mammalian ADP ribosyltransferase, cytokine-regulated metabolic activity, and apoptosis; show that PARP14 influences Myc-induced oncogenesis; and suggest that the PARP14-dependent capacity to increase cellular metabolic rates may be an important determinant of lymphoma pathobiology.

Human IGF binding protein-3 overexpression impairs glucose regulation in mice via an inhibition of insulin secretion

Human IGF binding protein-3 (hIGFBP-3) overexpression in mice causes hyperglycemia, but its effect on β-cell function is unknown. We compared wild-type mice with mice overexpressing hIGFBP-3 [phoshoglycerate kinase (PGK)BP3] and mutant (Gly⁵⁶/Gly⁸⁰/Gly⁸¹)hIGFBP-3 devoid of IGF binding affinity (PGKmBP3). Intraperitoneal glucose and insulin tolerance tests were performed, and glucose, IGFBP-3, IGF-I, and insulin were determined. Pancreatic sections were used for islet histomorphometry and stained with antibodies against insulin, glucagon, and hIGFBP-3. Pancreatic islets were isolated to determine the expression of IGFBP-3, and glucose-stimulated insulin secretion was measured using both islet batch incubation and perifusion. IGFBP-3 was expressed in β-cells but not in other islet cell types. Fasting glucose concentration was elevated in PGKBP3 mice (6.27 ± 0.31 mm) compared with PGKmBP3 mice (3.98 ± 0.36 mm) and wild-type mice (4.84 ± 0.07 mm). During glucose tolerance test, glucose declined more slowly in PGKBP3 and PGKmBP3 mice than in wild-type mice, and insulin secretion was impaired in PGKBP3 mice. During insulin tolerance test, insulin declined more slowly in both transgenic mice compared with wild-type mice. Insulin secretion in islets incubated with 3.3 mm glucose was similar among groups, but islet insulin response to 16.7 mm glucose alone, or with carbachol and cAMP enhancers, was reduced in PGKBP3 and PGKmBP3 mice compared with wild-type controls. ATP content, Akt phosphorylation, and phosphoglucose isomerase activity were reduced in islets from both transgenic mice. Thus, overexpression of hIGFBP-3 in mice delays in vivo insulin clearance and reduces glucose-stimulated insulin secretion in pancreatic islets by both IGF-dependent and IGF-independent mechanisms.

Evolutionary history of the poly(ADP-ribose) polymerase gene family in eukaryotes

BACKGROUND

The poly(ADP-ribose) polymerase (PARP) superfamily was originally identified as enzymes that catalyze the attachment of ADP-ribose subunits to target proteins using NAD+ as a substrate. The family is characterized by the catalytic site, termed the PARP signature. While these proteins can be found in a range of eukaryotes, they have been best studied in mammals. In these organisms, PARPs have key functions in DNA repair, genome integrity and epigenetic regulation. More recently it has been found that proteins within the PARP superfamily have altered catalytic sites, and have mono(ADP-ribose) transferase (mART) activity or are enzymatically inactive. These findings suggest that the PARP signature has a broader range of functions that initially predicted. In this study, we investigate the evolutionary history of PARP genes across the eukaryotes.

RESULTS

We identified in silico 236 PARP proteins from 77 species across five of the six eukaryotic supergroups. We performed extensive phylogenetic analyses of the identified PARPs. They are found in all eukaryotic supergroups for which sequence is available, but some individual lineages within supergroups have independently lost these genes. The PARP superfamily can be subdivided into six clades. Two of these clades were likely found in the last common eukaryotic ancestor. In addition, we have identified PARPs in organisms in which they have not previously been described.

CONCLUSIONS

Three main conclusions can be drawn from our study. First, the broad distribution and pattern of representation of PARP genes indicates that the ancestor of all extant eukaryotes encoded proteins of this type. Second, the ancestral PARP proteins had different functions and activities. One of these proteins was similar to human PARP1 and likely functioned in DNA damage response. The second of the ancestral PARPs had already evolved differences in its catalytic domain that suggest that these proteins may not have possessed poly(ADP-ribosyl)ation activity. Third, the diversity of the PARP superfamily is larger than previously documented, suggesting as more eukaryotic genomes become available, this gene family will grow in both number and type.

The complex biology of autocrine motility factor/phosphoglucose isomerase (AMF/PGI) and its receptor, the gp78/AMFR E3 ubiquitin ligase

Phosphoglucose isomerase (PGI) is a glycolytic enzyme that exhibits a dual function as an extracellular cytokine, under the name autocrine motility factor (AMF). Its cell surface receptor, gp78/AMFR, is also localized to the endoplasmic reticulum where it functions as an E3 ubiquitin ligase. Expression of both AMF/PGI and gp78/AMFR is associated with cancer and, in this review, we will discuss various aspects of the biology of this ligand-receptor complex and its role in tumor progression.

Drug development against metastasis-related genes and their pathways: a rationale for cancer therapy

It is well recognized that the majority of cancer related deaths is caused by metastatic diseases. Therefore, there is an urgent need for the development of therapeutic intervention specifically targeted to the metastatic process. In the last decade, significant progress has been made in this research field, and many new concepts have emerged that shed light on the molecular mechanism of metastasis cascade which is often portrayed as a succession of six distinct steps; localized invasion, intravasation, translocation, extravasation, micrometastasis and colonization. Successful metastasis is dependent on the balance and complex interplay of both the metastasis promoters and suppressors in each step. Therefore, the basic strategy of our interventions is aimed at either blocking the promoters or potentiating the suppressors in this disease process. Toward this goal, various kinds of antibodies and small molecules have been designed. These include agents that block the ligand-recepter interaction of metastasis promoters (HGF/c-Met), antagonize the metastasis-promoting enzymes (AMF, uPA and MMP) and inhibit the transcriptional activity of metastasis promoter (beta-Catenin). On the other hand, the intriguing roles of metastasis suppressors and their signal pathways have been extensively studied and various attempts have been made to potentiate these factors. Small molecules have been developed to restore the expression or mimic the function of metastasis-suppressor genes such as NM23, E-cadherin, Kiss-1, MKK4 and NDRG1, and some of them are under clinical trials. This review summarizes our current understanding of the molecular pathway of tumor metastasis and discusses strategies and recent development of anti-metastatic drugs.