Myeloid differentiation (MyD)/growth arrest DNA damage (GADD) genes in tumor suppression, immunity and inflammation

Integrated bioinformatic analysis identifies GADD45B as an immune-related prognostic biomarker in skin cutaneous melanoma

Skin cutaneous melanoma (SKCM) arises from melanocytes and is an aggressive form of skin cancer. If left untreated, most melanomas will metastasize, posing a major health risk. GADD45B, a member of the GADD45 family, is known to be involved in DNA damage repair; however, its specific role in SKCM remains largely unclear. In this study, we comprehensively investigated the function of GADD45B in SKCM. By integrating 26 SKCM-related datasets from The Cancer Genome Atlas (TCGA), Cancer Cell Line Encyclopedia (CCLE), cBioPortal for Cancer Genomics (cBioPortal), Gene Expression Omnibus (GEO), and other databases, we conducted functional enrichment, immune infiltration, and single-cell analyses using R. Additionally, transcriptome sequencing of 30 human SKCM cell lines, phenotype characterization of 29 SKCM lines in vitro, and macrophage polarization analysis were performed. We found that GADD45B expression was significantly downregulated in SKCM patients compared to normal controls (p < 0.001), and higher GADD45B levels correlated with better prognosis (p < 0.05). GADD45B also showed high diagnostic accuracy, with an area under the curve (AUC) of 0.986. GO and KEGG analyses revealed a strong association between GADD45B and immune-related pathways. Gene Set Variation Analysis (GSVA) and single-cell sequencing suggested that GADD45B may serve as a novel immune checkpoint, predominantly expressed in macrophages and promoting M1 polarization. In vitro, overexpression of GADD45B significantly inhibited SKCM cell proliferation, potentially via suppression of the PI3K/Akt signaling pathway, and also reduced chemotherapy resistance. Furthermore, in vivo experiments using a xenograft mouse model demonstrated that GADD45B overexpression significantly suppressed tumor growth. Mice injected with GADD45B-overexpressing tumor cells exhibited smaller tumor volumes from day 15 onwards compared to controls, with markedly reduced tumor volume and weight at the endpoint. These results underscore the potential of GADD45B as an effective tumor suppressor in SKCM. In conclusion, our findings highlight GADD45B as a key regulator in SKCM progression, capable of restraining tumor cell proliferation and enhancing apoptosis. GADD45B holds promise as a novel diagnostic and prognostic biomarker and a potential target for SKCM immunotherapy.

Deficiency of Growth Arrest and DNA Damage-Inducible 45 α -R-Loop Pathway and Kidney Injury in Diabetic Nephropathy

Background

Diabetic nephropathy is a primary cause of kidney failure. Persistent hyperglycemia causes metabolic perturbations epigenetically dysregulating gene expression in kidney cells, thereby leading to diabetic nephropathy pathogenesis. On analyzing the Gene Expression Omnibus database by using machine learning algorithms, our preliminary results demonstrated that growth arrest and DNA damage–inducible 45α (GADD45α) might serve as key regulators in diabetic nephropathy. Furthermore, emerging evidence has shown that R-loops, the three-stranded DNA–RNA structures, are crucial to gene expression during diabetic nephropathy. Therefore, this study aimed to investigate the role of GADD45α in diabetic nephropathy by modulating epigenetic alterations through interaction with R-loops.

Methods

A diabetic mouse model was established by injecting streptozotocin intraperitoneally into mice. Kidney histology and biochemical markers were analyzed in wild-type, GADD45α knockout, and renal tubule–specific GADD45α-overexpressing mice. The GADD45α lentivirus was used to induce the overexpression of GADD45α in human kidney-2 (a proximal tubular epithelial cell line) cells, while high-glucose treatment was applied to verify the mechanisms in vitro.

Results

GADD45α expression was reduced in kidneys of diabetic nephropathy, correlating with kidney dysfunction. GADD45α knockout worsened kidney injuries, while overexpression mitigated them. Mechanistically, GADD45α interacted with R-loops on the six-transmembrane epithelial antigen of the prostate 4 (STEAP4) promoter, recruiting ten eleven translocation 1 to activate STEAP4 transcription. Deficiency in the GADD45α-R-loop pathway exacerbated mitochondrial injury, disrupted lipid metabolism, and increased oxidative stress in diabetic nephropathy.

Conclusions

Deficiency of GADD45α exacerbates diabetic nephropathy by interacting with R-loops and inhibiting STEAP4 promoter demethylation. Targeting the GADD45α-R-loop pathway offers therapeutic potential against diabetic nephropathy.

Artesunate improves glucose and lipid metabolism in db/db mice by regulating the metabolic profile and the MAPK/PI3K/Akt signalling pathway

BACKGROUND

Diabetes is a metabolic disorder characterized by chronic hyperglycaemia. Chronic metabolic abnormalities and long-term hyperglycaemia may result in a wide range of acute and chronic consequences. Previous studies have demonstrated that artesunate(ART) has antidiabetic, anti-inflammatory, antiatherosclerotic, and other beneficial effects, but the specific regulatory mechanism is not completely clear.

AIM

This study investigated the effects of ART on metabolic disorders in type 2 diabetes mellitus (T2DM) model db/db mice and explored the underlying mechanisms involved.

METHODS

C57BL/KsJ-db/db mice were used to identify the targets and molecular mechanism of ART. Metabolomic methods were used to evaluate the efficacy of ART in improving T2DM-related metabolic disorders. Network pharmacology and transcriptomic sequencing were used to analyse the targets and pathways of ART in T2DM. Finally, molecular biology experiments were performed to verify the key targets and pathways selected by network pharmacology and transcriptomic analyses.

RESULTS

After a 7-week ART intervention (160 mg/kg), the glucose and lipid metabolism levels of the db/db mice improved. Additionally, the oxidative stress indices, namely, the MDA and SOD levels, significantly improved (p<0.01). Linoleic acid and glycerophospholipid metabolism, amino acid metabolism, bile acid synthesis, and purine metabolism disorders in db/db mice were partially corrected after ART treatment. Network pharmacology analysis identified important targets of ART for the treatment of metabolic disorders in T2DM . These targets are involved in key signalling pathways, including the highest scores observed for the PI3K/Akt signalling pathway. Transcriptomic analysis revealed that ART could activate the MAPK signalling pathway and two key gene targets, HGK and GADD45. Immunoblotting revealed that ART increases p-PI3K, p-AKT, Glut2, and IRS1 protein expression and suppresses the phosphorylation of p38, ERK1/2, and JNK, returning HGK and GADD45 to their preartesunate levels.

CONCLUSION

Treatment of db/db mice with 160 mg/kg ART for 7 weeks significantly reduced fasting blood glucose and lipid levels. It also improved metabolic imbalances in amino acids, lipids, purines, and bile acids, thereby improving metabolic disorders. These effects are achieved by activating the PI3K/AKT pathway and inhibiting the MAPK pathway, thus demonstrating the efficacy of the drug.

PET/CT-based deep learning grading signature to optimize surgical decisions for clinical stage I invasive lung adenocarcinoma and biologic basis under its prediction: a multicenter study

PURPOSE

No consensus on a grading system for invasive lung adenocarcinoma had been built over a long period of time. Until October 2020, a novel grading system was proposed to quantify the whole landscape of histologic subtypes and proportions of pulmonary adenocarcinomas. This study aims to develop a deep learning grading signature (DLGS) based on positron emission tomography/computed tomography (PET/CT) to personalize surgical treatments for clinical stage I invasive lung adenocarcinoma and explore the biologic basis under its prediction.

METHODS

A total of 2638 patients with clinical stage I invasive lung adenocarcinoma from 4 medical centers were retrospectively included to construct and validate the DLGS. The predictive performance of the DLGS was evaluated by the area under the receiver operating characteristic curve (AUC), its potential to optimize surgical treatments was investigated via survival analyses in risk groups defined by the DLGS, and its biological basis was explored by comparing histologic patterns, genotypic alternations, genetic pathways, and infiltration of immune cells in microenvironments between risk groups.

RESULTS

The DLGS to predict grade 3 achieved AUCs of 0.862, 0.844, and 0.851 in the validation set (n = 497), external cohort (n = 382), and prospective cohort (n = 600), respectively, which were significantly better than 0.814, 0.810, and 0.806 of the PET model, 0.813, 0.795, and 0.824 of the CT model, and 0.762, 0.734, and 0.751 of the clinical model. Additionally, for DLGS-defined high-risk population, lobectomy yielded an improved prognosis compared to sublobectomy p = 0.085 for overall survival [OS] and p = 0.038 for recurrence-free survival [RFS]) and systematic nodal dissection conferred a superior prognosis to limited nodal dissection (p = 0.001 for OS and p = 0.041 for RFS).

CONCLUSION

The DLGS harbors the potential to predict the histologic grade and personalize the surgical treatments for clinical stage I invasive lung adenocarcinoma. Its applicability to other territories should be further validated by a larger international study.

Transcriptome of the Krushinsky-Molodkina Audiogenic Rat Strain and Identification of Possible Audiogenic Epilepsy-Associated Genes

Audiogenic epilepsy (AE), inherent to several rodent strains is widely studied as a model of generalized convulsive epilepsy. The molecular mechanisms that determine the manifestation of AE are not well understood. In the present work, we compared transcriptomes from the corpora quadrigemina in the midbrain zone, which are crucial for AE development, to identify genes associated with the AE phenotype. Three rat strains without sound exposure were compared: Krushinsky-Molodkina (KM) strain (100% AE-prone); Wistar outbred rat strain (non-AE prone) and “0” strain (partially AE-prone), selected from F2 KM × Wistar hybrids for their lack of AE. The findings showed that the KM strain gene expression profile exhibited a number of characteristics that differed from those of the Wistar and “0” strain profiles. In particular, the KM rats showed increased expression of a number of genes involved in the positive regulation of the MAPK signaling cascade and genes involved in the positive regulation of apoptotic processes. Another characteristic of the KM strain which differed from that of the Wistar and “0” rats was a multi-fold increase in the expression level of the Ttr gene and a significant decrease in the expression of the Msh3 gene. Decreased expression of a number of oxidative phosphorylation-related genes and a few other genes was also identified in the KM strain. Our data confirm the complex multigenic nature of AE inheritance in rodents. A comparison with data obtained from other independently selected AE-prone rodent strains suggests some common causes for the formation of the audiogenic phenotype.

Distinct human Langerhans cell subsets orchestrate reciprocal functions and require different developmental regulation

Langerhans cells (LCs) play a pivotal role in skin homeostasis, and the heterogeneity of LCs has long been considered. In this study, we have identified two steady-state (LC1 and LC2) and two activated LC subsets in the epidermis of human skin and in LCs derived from CD34+ hemopoietic stem cells (HSC-LCs) by utilizing single-cell RNA sequencing and mass cytometry. Analysis of HSC-LCs at multiple time-points during differentiation revealed that EGR1 and Notch signaling were among the top pathways regulating the bifurcation of LC1 and LC2. LC1 were characterized as classical LCs, mainly related to innate immunity and antigen processing. LC2 were similar to monocytes or myeloid dendritic cells, involving in immune responses and leukocyte activation. LC1 remained stable under inflammatory microenvironment, whereas LC2 were prone to being activated and demonstrated elevated expression of immuno-suppressive molecules. We revealed distinct human LC subsets that require different developmental regulation and orchestrate reciprocal functions.

Transcriptional and Metabolic Dissection of ATRA-Induced Granulocytic Differentiation in NB4 Acute Promyelocytic Leukemia Cells

Acute promyelocytic leukemia (APL) is a hematological disease characterized by a balanced reciprocal translocation that leads to the synthesis of the oncogenic fusion protein PML-RARα. APL is mainly managed by a differentiation therapy based on the administration of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO). However, therapy resistance, differentiation syndrome, and relapses require the development of new low-toxicity therapies based on the induction of blasts differentiation. In keeping with this, we reasoned that a better understanding of the molecular mechanisms pivotal for ATRA-driven differentiation could definitely bolster the identification of new therapeutic strategies in APL patients. We thus performed an in-depth high-throughput transcriptional profile analysis and metabolic characterization of a well-established APL experimental model based on NB4 cells that represent an unevaluable tool to dissect the complex mechanism associated with ATRA-induced granulocytic differentiation. Pathway-reconstruction analysis using genome-wide transcriptional data has allowed us to identify the activation/inhibition of several cancer signaling pathways (e.g., inflammation, immune cell response, DNA repair, and cell proliferation) and master regulators (e.g., transcription factors, epigenetic regulators, and ligand-dependent nuclear receptors). Furthermore, we provide evidence of the regulation of a considerable set of metabolic genes involved in cancer metabolic reprogramming. Consistently, we found that ATRA treatment of NB4 cells drives the activation of aerobic glycolysis pathway and the reduction of OXPHOS-dependent ATP production. Overall, this study represents an important resource in understanding the molecular “portfolio” pivotal for APL differentiation, which can be explored for developing new therapeutic strategies.

Azacitidine regulates DNA methylation of GADD45γ in myelodysplastic syndromes

Background

Myelodysplastic syndrome (MDS) is a heterogeneous clonal disease originated from hematopoietic stem cells. Epigenetic studies had demonstrated that DNA methylation and histone acetylation were abnormal in MDS. Azacitidine is an effective drug in the treatment of demethylation.

Methods

RT‐PCR was performed to determine GADD45γ in 15 MDS clinical samples. Myelodysplastic syndrome cell lines SKM‐1 and HS‐5 were transfected with GADD45γ eukaryotic expression vector and/or GADD45γ shRNA interference plasmid, and treated with azacitidine. Proliferation and apoptosis were examined by CCK‐8 and Western blot analysis to confirm the function role of GADD45γ and azacitidine. The methylation level of GADD45γ gene was detected by bisulfite conversion and PCR.

Results

This study found that GADD45γ gene was down‐expressed in MDS patients' bone marrow and MDS cell lines, and the down‐regulation of GADD45γ in MDS could inhibit MDS cell apoptosis and promote proliferation. Azacitidine, a demethylation drug, could restore the expression of GADD45γ in MDS cells and inhibit the proliferation of MDS cells by inducing apoptosis, which was related to prognosis and transformation.

Conclusion

This study indicated that GADD45γ was expected to become a new target of MDS‐targeted therapy. The findings of this study provided a new direction for the research and development of new MDS clinical drugs, and gave a new idea for the development of MDS demethylation drug to realize precise treatment.

Knockdown of GADD34 in neonatal mutant SOD1 mice ameliorates ALS

Mutations in Cu/Zn superoxide dismutase (SOD1) cause ~20% of familial ALS (FALS), which comprises 10% of total ALS cases. In mutant SOD1- (mtSOD1-) induced ALS, misfolded aggregates of SOD1 lead to activation of the unfolded protein response/integrated stress response (UPR/ISR). Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), a kinase that phosphorylates eukaryotic translation initiator factor 2α (p-eIF2α), coordinates the response by causing a global suppression of protein synthesis. Growth arrest and DNA damage 34 (GADD34) dephosphorylates p-eIF2α, allowing protein synthesis to return to normal. If the UPR/ISR is overwhelmed by the amount of misfolded protein, CCAAT/enhancer-binding homologous protein (CHOP) is activated leading to apoptosis. In the current study we investigated the effect of knocking down CHOP and GADD34 on disease of G93A and G85R mtSOD1 mice. Although a CHOP antisense oligonucleotide had no effect on survival, an intravenous injection of GADD34 shRNA encoded in adeno-associated virus 9 (AAV9) into neonatal G93A as well as neonatal G85R mtSOD1 mice led to a significantly increased survival. G85R mtSOD1 mice had a reduction in SOD1 aggregates/load, astrocytosis, and microgliosis. In contrast, there was no change in disease phenotype when GADD34 shRNA was delivered to older G93A mtSOD1 mice. Our current study shows that GADD34 shRNA is effective in ameliorating disease when administered to neonatal mtSOD1 mice. Targeting the UPR/ISR may be beneficial in mtSOD1-induced ALS as well as other neurodegenerative diseases in which misfolded proteins and ER stress have been implicated.

Effects of Ferroportin-Mediated Iron Depletion in Cells Representative of Different Histological Subtypes of Prostate Cancer

AIMS

Ferroportin (FPN) is an iron exporter that plays an important role in cellular and systemic iron metabolism. Our previous work has demonstrated that FPN is decreased in prostate tumors. We sought to identify the molecular pathways regulated by FPN in prostate cancer cells.

RESULTS

We show that overexpression of FPN induces profound effects in cells representative of multiple histological subtypes of prostate cancer by activating different but converging pathways. Induction of FPN induces autophagy and activates the transcription factors tumor protein 53 (p53) and Kruppel-like factor 6 (KLF6) and their common downstream target, cyclin-dependent kinase inhibitor 1A (p21). FPN also induces cell cycle arrest and stress-induced DNA-damage genes. Effects of FPN are attributable to its effects on intracellular iron and can be reproduced with iron chelators. Importantly, expression of FPN not only inhibits proliferation of all prostate cancer cells studied but also reduces growth of tumors derived from castrate-resistant adenocarcinoma C4-2 cells in vivo.

INNOVATION

We use a novel model of FPN expression to interrogate molecular pathways triggered by iron depletion in prostate cancer cells. Since prostate cancer encompasses different subtypes with a highly variable clinical course, we further explore how histopathological subtype influences the response to iron depletion. We demonstrate that prostate cancer cells that derive from different histopathological subtypes activate converging pathways in response to FPN-mediated iron depletion. Activation of these pathways is sufficient to significantly reduce the growth of treatment-refractory C4-2 prostate tumors in vivo.

CONCLUSIONS

Our results may explain why FPN is dramatically suppressed in cancer cells, and they suggest that FPN agonists may be beneficial in the treatment of prostate cancer.

Another look at phenolic compounds in cancer therapy the effect of polyphenols on ubiquitin-proteasome system

Inhibitors of the ubiquitin-proteasome system (UPS) have been the object of research interests for many years because of their potential as anti-cancer agents. Research in this field is aimed at improving the specificity and safety of known proteasome inhibitors. Unfortunately, in vitro conditions do not reflect the processes taking place in the human body. Recent reports indicate that the components of human plasma affect the course of many signaling pathways, proteasome activity and the effectiveness of synthetic cytostatic drugs. Therefore, it is believed that the key issue is to determine the effects of components of the human diet, including effects of chemically active polyphenols on the ubiquitin-proteasome system activity in both physiological and pathological (cancerous) states. The following article summarizes the current knowledge on the direct and indirect synergistic and antagonistic effects between polyphenolic compounds present in the human diet and the efficiency of protein degradation via the UPS.

GADD45B as a Prognostic and Predictive Biomarker in Stage II Colorectal Cancer

GADD45B acts as a member of the growth arrest DNA damage-inducible gene family, which has demonstrated to play critical roles in DNA damage repair, cell growth, and apoptosis. This study aimed to explore the potential relationship between GADD45B expression and tumor progression and evaluate the clinical value of GADD45B in stage II colorectal cancer (CRC). The expression patterns and prognostic value of GADD45B in CRC were analyzed based on The Cancer Genomic Atlas (TCGA). GADD45B expression features of 306 patients with stage II CRC and 201 patients with liver metastasis of CRC were investigated using immunochemical staining on tissue microarrays. Afterward, survival analysis and stratification analysis were performed in stage II to explore the prognostic and predictive significance of GADD45B. Overexpressed GADD45B is associated with poorer prognosis for CRC patients both in overall survival (OS) (p < 0.001) and disease-free survival (DFS) (p = 0.001) based on the TCGA database. Analysis results according to the stage II CRC cohort and the liver metastatic CRC cohort revealed that GADD45B was gradually upregulated in normal mucosa including primary colorectal cancer (PCC). Colorectal liver metastases (CLM) tissues were arranged in order (normal tissue vs. PCC p = 0.005 and PCC vs. CLM p = 0.001). The low GADD45B group had a significantly longer five-year OS (p = 0.001) and progression-free survival (PFS) (p < 0.001) than the high GADD45B group for the stage II patients. The multivariate Cox regression analysis results proved that the expression level of GADD45B was an independent prognostic factor for stage II after radical surgery (OS: Hazard Ratio (HR) 0.479, [95% confidence interval (CI) 0.305⁻0.753] and PFS:HR 0.490, [95% CI 0.336⁻0.714]). In high GADD45B expression subgroup of stage II cohort, the patients who underwent adjuvant chemotherapy had longer PFS than those who did not (p = 0.008). High expression levels of GADD45B is an independent prognostic factor of decreased OS and PFS in stage II CRC patients. The stage II CRC patients with high GADD45B expression might benefit from adjuvant chemotherapy.

GADD45β plays a protective role in acute lung injury by regulating apoptosis in experimental sepsis in vivo

Sepsis is a systemic inflammatory response syndrome due to microbial infection. Growth arrest and DNA-damage-inducible 45 beta (GADD45β) are induced by genotoxic stress and inflammatory cytokines. However, the role of GADD45β during bacterial infection remains unclear. This study was aimed at investigating the role of GADD45β in sepsis. We used GADD45β-knockout (KO) mice and C57BL/6J wild-type (WT) mice. Experimental sepsis was induced by lipopolysaccharide (LPS) administration or cecal ligation and puncture (CLP). Sepsis-induced mortality was higher in GADD45β-KO mice than in WT mice. Histopathological data demonstrated LPS treatment markedly increased lung injury in GADD45β-KO mice as compared to that in WT mice; however, no significant difference was observed in the liver and kidney. Further, mRNA levels of inflammatory cytokines, such as Il-1β, Il-6, Il-10, and Tnf-α, were higher in the lungs of LPS-treated GADD45β-KO mice than in WT mice. Interestingly, plasma levels of these inflammatory cytokines were decreased in LPS-administered GADD45β-KO mice. A significant increase in lung cell apoptosis was observed at early time points in GADD45β-KO mice after administration of LPS as compared to that in WT mice. In line with LPS-induced apoptosis, JNK, and p38 activity was higher in the lung of GADD45β-KO mice at 3 hr after LPS treatment than that in WT mice. In summary, this study is the first to demonstrate the protective role of GADD45β in sepsis and the results suggest that GADD45β could be used as a novel therapeutic target to cure sepsis.

Identification of RNA biomarkers for chemical safety screening in mouse embryonic stem cells using RNA deep sequencing analysis

Although it is not yet possible to replace in vivo animal testing completely, the need for a more efficient method for toxicity testing, such as an in vitro cell-based assay, has been widely acknowledged. Previous studies have focused on mRNAs as biomarkers; however, recent studies have revealed that non-coding RNAs (ncRNAs) are also efficient novel biomarkers for toxicity testing. Here, we used deep sequencing analysis (RNA-seq) to identify novel RNA biomarkers, including ncRNAs, that exhibited a substantial response to general chemical toxicity from nine chemicals, and to benzene toxicity specifically. The nine chemicals are listed in the Japan Pollutant Release and Transfer Register as class I designated chemical substances. We used undifferentiated mouse embryonic stem cells (mESCs) as a simplified cell-based toxicity assay. RNA-seq revealed that many mRNAs and ncRNAs responded substantially to the chemical compounds in mESCs. This finding indicates that ncRNAs can be used as novel RNA biomarkers for chemical safety screening.

Impacts of Early Life Stress on the Methylome and Transcriptome of Atlantic Salmon

Exposure to environmental stressors during early-life stages can change the rate and timing of various developmental processes. Epigenetic marks affecting transcriptional regulation can be altered by such environmental stimuli. To assess how stress might affect the methylome and transcriptome in salmon, fish were treated using cold-shock and air-exposure from the eye-stage until start-feeding. The fish were either stressed prior to hatching (E), post-hatching (PH), pre- and post-hatching (EPH) or not stressed (CO). Assessing transcriptional abundances just prior to start feeding, E and PH individuals were found to have modified the expression of thousands of genes, many with important functions in developmental processes. The EPH individuals however, showed expression similar to those of CO, suggesting an adaptive response to extended periods of stress. The methylome of stressed individuals differed from that of the CO, suggesting the importance of environment in shaping methylation signatures. Through integration of methylation with transcription, we identified bases with potential regulatory functions, some 10s of kb away from the targeted genes. We then followed fish growth for an additional year. Individuals in EPH showed superior growth compared to other treatment groups, highlighting how stress can potentially have long-lasting effects on an organism's ability to adapt to environmental perturbations.

Differential transcriptional responses to Ebola and Marburg virus infection in bat and human cells

The unprecedented outbreak of Ebola in West Africa resulted in over 28,000 cases and 11,000 deaths, underlining the need for a better understanding of the biology of this highly pathogenic virus to develop specific counter strategies. Two filoviruses, the Ebola and Marburg viruses, result in a severe and often fatal infection in humans. However, bats are natural hosts and survive filovirus infections without obvious symptoms. The molecular basis of this striking difference in the response to filovirus infections is not well understood. We report a systematic overview of differentially expressed genes, activity motifs and pathways in human and bat cells infected with the Ebola and Marburg viruses, and we demonstrate that the replication of filoviruses is more rapid in human cells than in bat cells. We also found that the most strongly regulated genes upon filovirus infection are chemokine ligands and transcription factors. We observed a strong induction of the JAK/STAT pathway, of several genes encoding inhibitors of MAP kinases (DUSP genes) and of PPP1R15A, which is involved in ER stress-induced cell death. We used comparative transcriptomics to provide a data resource that can be used to identify cellular responses that might allow bats to survive filovirus infections.

Fasting-induced liver GADD45β restrains hepatic fatty acid uptake and improves metabolic health

Recent studies have demonstrated that repeated short‐term nutrient withdrawal (i.e. fasting) has pleiotropic actions to promote organismal health and longevity. Despite this, the molecular physiological mechanisms by which fasting is protective against metabolic disease are largely unknown. Here, we show that, metabolic control, particularly systemic and liver lipid metabolism, is aberrantly regulated in the fasted state in mouse models of metabolic dysfunction. Liver transcript assays between lean/healthy and obese/diabetic mice in fasted and fed states uncovered “growth arrest and DNA damage‐inducible” GADD45β as a dysregulated gene transcript during fasting in several models of metabolic dysfunction including ageing, obesity/pre‐diabetes and type 2 diabetes, in both mice and humans. Using whole‐body knockout mice as well as liver/hepatocyte‐specific gain‐ and loss‐of‐function strategies, we revealed a role for liver GADD45β in the coordination of liver fatty acid uptake, through cytoplasmic retention of FABP1, ultimately impacting obesity‐driven hyperglycaemia. In summary, fasting stress‐induced GADD45β represents a liver‐specific molecular event promoting adaptive metabolic function.

Multifaceted functions and roles of HBZ in HTLV-1 pathogenesis

Human T cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus responsible for the development of adult T-cell leukemia (ATL). Although HTLV-1 harbors an oncogene, tax, that transforms T cells in vitro and induces leukemia in transgenic mice, tax expression is frequently disrupted in ATL, making the oncogenesis of ATL a bit mysterious. The HTLV-1 bZIP factor (HBZ) gene was discovered in 2002 and has been found to promote T-cell proliferation and cause lymphoma in transgenic mice. Thus HBZ has become a novel hotspot of HTLV-1 research. This review summarizes the current findings on HBZ with a special focus on its potential links to the oncogenesis of ATL. We propose viewing HBZ as a critical contributing factor in ATL development.

Transcriptional signatures of unfolded protein response implicate the limitation of animal models in pathophysiological studies

Background

The unfolded protein response (UPR) refers to intracellular stress signaling pathways that protect cells from the stress caused by accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER). The UPR signaling is crucially involved in the initiation and progression of a variety of human diseases by modulating transcriptional and translational programs of the stressed cells. In this study, we analyzed the gene expression signatures of primary stress sensors and major mediators of UPR pathways in a variety of tissues/organs of human and murine species.

Methods

We first analyzed protein sequence similarities of major UPR transducers and mediators of human and murine species, and then examined their gene expression profiles in 26 human and mouse common tissues based on the microarray datasets of public domains. The differential expression patterns of the UPR genes in human diseases were delineated. The involvements of the UPR genes in mouse pathology were also analyzed with mouse gene knockout models.

Results

The results indicated that expression patterns and pathophysiologic involvements of the major UPR stress sensors and mediators significantly differ in 26 common tissues/organs of human and murine species. Gene expression profiles suggest that the IRE1α/XBP1-mediated UPR pathway is induced in secretory and metabolic tissues or organs. While deletion of the UPR trans-activator XBP1 leads to pathological phenotypes in mice, alteration in XBP1 is less associated with human disease conditions.

Conclusions

Expression signatures of the major UPR genes differ among tissues or organs and among human and mouse species. The differential induction of the UPR pathways reflects the pathophysiologic differences of tissues or organs. The difference in UPR induction between human and mouse suggests the limitation of using animal models to study human pathophysiology or drugology associated with environmental stress.

Retinoids induce Nur77-dependent apoptosis in mouse thymocytes

Nur77 is a transcription factor, which plays a determinant role in mediating T cell receptor-induced cell death of thymocytes. In addition to regulation of transcription, Nur77 contributes to apoptosis induction by targeting mitochondria, where it can convert Bcl-2, an anti-apoptotic protein into a proapoptotic molecule. Previous studies have demonstrated that retinoids are actively produced in the mouse thymus and can induce a transcription-dependent apoptosis in mouse thymocytes. Here we show that retinoic acids induce the expression of Nur77, and retinoid-induced apoptosis is completely dependent on Nur77, as retinoids were unable to induce apoptosis in Nur77 null thymocytes. In wild-type thymocytes retinoids induced enhanced expression of the apoptosis-related genes FasL, TRAIL, NDG-1, Gpr65 and Bid, all of them in a Nur77-dependent manner. The combined action of these proteins led to Caspase 8-dependent Bid cleavage in the mitochondria. In addition, we could demonstrate the Nur77-dependent induction of STAT1 leading to enhanced Bim expression, and the mitochondrial translocation of Nur77 leading to the exposure of the Bcl-2/BH3 domain. The retinoid-induced apoptosis was dependent on both Caspase 8 and STAT1. Our data together indicate that retinoids induce a Nur77-dependent cell death program in thymocytes activating the mitochondrial pathway of apoptosis.

Effects of cadmium on cell proliferation, apoptosis, and proto-oncogene expression in zebrafish liver cells

Cadmium (Cd) is one of the major transitional metal that has toxic effects in aquatic organisms and their associated ecosystem; however, its hepatic toxicity and carcinogenicity are not very well characterized. We used a zebrafish liver (ZFL) cell line as a model to investigate the mechanism of Cd-induced toxicity on hepatocytes. Our results showed that Cd can be effectively accumulated in ZFL cells in our exposure experiments. Cell cytotoxicity assays and flow cytometer measurements revealed that Cd(2+) stimulated ZFL cell proliferation with decreasing apoptotic cell numbers indicating potentially tumorigenic effects of Cd in ZFL cells. Gene expression profiles also indicated that Cd downregulated oncogenes p53 and rad51 and upregulated immediate response oncogenes, growth arrest and DNA damage-inducible (gadd45) genes, and growth factors. We also found dramatic changes in the gene expression of c-jun and igf1rb at different exposure time points, supporting the notion that potentially tumorigenic of Cd-is involved in the activation of immediate early genes or genes related to apoptosis in cancer promotion.

Myelodysplastic syndromes and autoimmune diseases--case series and review of literature

Our objective was to recognize the association of autoimmune diseases (AD) in patients with myelodysplastic syndromes (MDS) and understand how this association could affect prognosis and management of both diseases. We describe our cohort of 10 patients and 34 patients reported in the English literature in addition to ten cohort studies. Interestingly, four cases showed improvement in AD after 5-azacitidine treatment. The mechanism(s) of the association between AD and MDS are discussed. Treatment could be targeted against AD, MDS or both, though based on recent reports, treating MDS with hypomethylating agents alone could improve the associated AD.

Intracellular antibody-bound pathogens stimulate immune signaling via the Fc receptor TRIM21

Antibodies can be carried into the cell during pathogen infection where they are detected by the ubiquitously expressed cytosolic antibody receptor TRIM21. Here we show that TRIM21 recognition of intracellular antibodies activates immune signaling. TRIM21 catalyses K63-ubiquitin chain formation, stimulating transcription factor pathways NF-κB, AP-1 and IRF3, IRF5, IRF7. Activation results in proinflammatory cytokine production, modulation of natural killer (NK) stress ligands and the induction of an antiviral state. Intracellular antibody signaling is abrogated by genetic deletion of TRIM21 and is recovered by ectopic TRIM21 expression. Antibody sensing by TRIM21 can be stimulated upon infection by DNA or RNA non-enveloped viruses or intracellular bacteria. The antibody-TRIM21 detection system provides potent, comprehensive innate immune activation, independent of known pattern recognition receptors.

Preeclampsia-associated stresses activate Gadd45a signaling and sFlt-1 in placental explants

Accumulating evidence suggests that placental stresses during pregnancy can play an important role in the pathogenesis of preeclampsia. A common signal pathway that senses and converts placental stresses into intracellular stress response may be contributing to this pathology. Based on our previous findings, we extended our investigation to establish that Gadd45a stress signaling regulates sFlt-1 levels, particularly in placenta, when exposed to various preeclampsia-associated stresses including AT-1 receptor agonist (Angiotensin II), hypoxia, and inflammatory cytokines. Using a placental explant model, we found that Gadd45a was induced in response to all the preeclampsia stresses stated above. Although stress induced Gadd45a was associated with the activation of its downstream effectors phospho-p38 and phospho-JNK, the subsequent regulation of sFlt-1 levels occurred through either one of these effectors, but not both. These observations indicate that Gadd45a signaling may work as a hub connecting placental stresses and the pathogenesis of preeclampsia. It also provides evidence to justify testing the role of Gadd45 in the etiology of preeclampsia using in vivo mouse (i.e., Gadd45a null mice) models.

Single-agent therapy with sorafenib or 5-FU is equally effective in human colorectal cancer xenograft--no benefit of combination therapy

BACKGROUND

We initiated this preclinical study in order to analyze the impact of sorafenib single treatment versus combination treatment in human colorectal cancer.

METHODS

The effect of increasing sorafenib doses on proliferation, apoptosis, migration, and activation of signal cascades was analyzed in vitro. The effect of sorafenib single treatment versus 5-fluorouracil (5-FU) single treatment and combination therapy on in vivo proliferation and target cytokine receptor/ligand expression was analyzed in a human colon cancer xenograft mouse model using HT29 tumor cells.

RESULTS

In vitro, SW480 and HT29 cell lines were sensitive to sorafenib, as compared to Caco2 and SW620 cell lines, independent of the mutation status of K-ras, Raf, PTEN, or PI3K. The effect on migration was marginal, but distinct differences in caspases activation were seen. Combination strategies were beneficial in some settings (sorafenib + 5-FU; irinotecan) and disadvantageous in others (sorafenib + oxaliplatin), depending on the chemotherapeutic drug and cell line chosen. Sensitive cell lines revealed a downregulation of AKT and had a weak expression level of GADD45β. In resistant cell lines, pp53 and GADD45β levels decreased upon sorafenib exposure. In vivo, the combination treatment of sorafenib and 5-FU was equally effective as the respective monotherapy concerning tumor proliferation. Interestingly, treatment with either sorafenib or 5-FU resulted in a significant decrease of VEGFR1 and PDGFRβ expression intensity.

CONCLUSIONS

In colorectal cancer, a sensitivity towards sorafenib exists, which seems similarly effective as a 5-FU monotherapy. A combination therapy, in contrast, does not show any additional effect.

Gadd45 stress sensors in preeclampsia

Preeclampsia is a pregnancy-induced complex of multiple pathological changes. Numerous stresses during pregnancy, including hypoxia, immune activation, inflammatory cytokines, and oxidative stress were reported as contributing factors to the preeclamptic pathology. Seeking common sensors of various stressors in preeclampsia is of new interest and can potentially benefit in disease prevention and treatment. Recent studies have highlighted the role of the Gadd45a protein as a stress sensor in preeclampsia. In response to various pathophysiological stressors, notably hypoxia, inflammatory cytokines, and AT1-AAs, Gadd45a activates Mkk3-p38 and or JNK signaling. This, in turn, results in immunological and inflammatory changes as well as triggering the production of circulating factors such as sFlt-1, which are believed to account for many of the pathophysiological-related symptoms of preeclampsia. Activation of inflammatory/immune responses in preeclampsia may function in a feedback loop to maintain elevated expression of Gadd45a protein.

Development of high-resolution melting analysis for the detection of the MYD88 L265P mutation

OBJECTIVE

Recurrent L265P mutation of myeloid differentiation primary response gene 88 (MYD88) has been identified in a proportion of diffuse large B-cell lymphoma (DLBCL) and chronic lymphocytic leukemia. The present study aimed to establish a rapid, sensitive, and reliable method using high-resolution melting analysis (HRMA) to detect MYD88 L265P mutation in DLBCL.

DESIGNS AND METHODS

The sensitivity of HRMA in the detection of MYD88 L265P mutation was evaluated. MYD88 L265P mutation was further screened in 120 patients with DLBCL. The results of HRMA were validated by direct DNA sequencing.

RESULTS

For the detection of MYD88 L265P mutation, the reproducible maximal sensitivity of HRMA was 5% higher than that obtained by direct DNA sequencing (25%). Heterozygous MYD88 L265P mutations were identified in 11 (9.2%) DLBCL cases, all of which were diagnosed as non-germinal-center B cell (non-GCB) DLBCL.

CONCLUSIONS

The HRMA assay is a rapid, sensitive, reliable, and high-throughput method to screen MYD88 L265P mutation and could be used in clinical diagnostic laboratories.

Nitric oxide pathway-related gene alterations in inflammatory bowel disease

OBJECTIVE

To reveal specific gene activation in nitric oxide (NO)-related inflammation we studied differential gene expression in inflammatory bowel disease (IBD).

METHODS

Total RNA was isolated from 20 biopsies of inflamed mucosa from Crohn's disease (CD) and ulcerative colitis (UC) patients each as well as from six controls, labeled with (32)P-dCTP and hybridized to a human NO gene array. Significant genes were analyzed for functional gene interactions and heatmaps generated by hierarchical clustering. A selection of differentially expressed genes was further evaluated with immunohistochemical staining.

RESULTS

Significant gene expression differences were found for 19 genes in CD and 23 genes in UC compared to controls, both diseases with high expression of ICAM1 and IL-8. Correlation between microarray expression and corresponding protein expression was significant (r = 0.47, p = 0.002). Clustering analysis together with functional gene interaction analysis revealed clusters of coregulation and coexpression in CD and UC: transcripts involved in angiogenesis, inflammatory response mediated by the transcription factor hypoxia-inducible factor 1, and tissue fibrosis. Also, a fourth cluster with transcripts regulated by the transcription factor Sp1 was found in UC.

CONCLUSIONS

Expression analysis in CD and UC revealed disease-specific regulation of NO-related genes, which might be involved in perpetuating inflammatory disease activity in IBD.

Abnormal expression of GADD45B in human colorectal carcinoma

Background

GADD45B is a member of the growth arrest DNA damage-inducible gene family associated with cell growth control, apoptosis, and DNA damage repair response. The aim of this study is to detect the role of GADD45B in colorectal carcinoma (CRC); the area not studied in depth to date.

Methods

The mRNA and protein levels of GADD45B were examined by Real-Time quantitative PCR (RT-qPCR) and immunohistochemistry (IHC) in CRC tissues and adjacent noncancerous tissues (ANCT). Over-expression plasmids and SiRNA were used to regulate GADD45B expression in CRC cell lines in vitro and flow cytometry and Western blotting were used to detect apoptotic changes.

Results

The mRNA and protein levels of GADD45B were significantly higher in CRC tissues than those in ANCT (P<0.05). Up-regulation of GADD45B was also correlated with relapse and death of CRC patients (P<0.05). The Kaplan-Meier survival curves indicated that disease-free survival (DFS) was significantly worse in CRC patients who showed GADD45B overexpression. A Cox multivariate analysis revealed that GADD45B overexpression and TNM stage were significant factors affecting patients’ survival. On the other hand, as a tumor suppressor gene, GADD45B amplified from normal colorectal tissues could induce apoptosis in CRC cell lines and may be associated with the p53-mediated apoptotic pathways.

Conclusion

GADD45B, a tumor suppressor gene potentially through the p53-mediated apoptotic pathways, is paradoxically overexpressed in CRC and as such may play an unappreciated role in tumorigenesis. The exact mechanism of GADD45B inactivation and overexpression requires further investigation. GADD45B could be a potential therapeutic target for CRC treatment in future.

Family-based association study of early growth response gene 3 with child bipolar I disorder

BACKGROUND

The risk for relapse of child bipolar I disorder (BP-I) is highly correlated with environmental factors. Immediate early genes of the early growth response (EGR) gene family are activated at high levels in the brain in response to environmental events, including stress, and mediate numerous neurobiological processes that have been associated with mental illness risk. The objective of this study is to evaluate whether single nucleotide polymorphisms (SNPs) in EGR genes are associated with the risk to develop child bipolar I disorder.

METHODS

To investigate whether EGR genes may influence susceptibility to child bipolar I disorder (BP-I), we used Family Based Association Tests to examine whether SNPs in each of the EGR genes were associated with illness in 49 families.

RESULTS

Two SNPs in EGR3 displayed nominally significant associations with child BP-I (p=0.027 and p=0.028); though neither was statistically significant following correction for multiple comparisons. Haplotype association analysis indicated that these SNPs are in linkage disequilibrium (LD). None of the SNPs tested in EGR1, EGR2, or EGR4 was associated with child BP-I.

LIMITATIONS

This study was limited by small sample size, which resulted in it being underpowered to detect a significant association after correction for multiple comparisons.

CONCLUSIONS

Our study revealed a preliminary finding suggesting that EGR3, a gene that translates environmental stimuli into long-term changes in the brain, warrants further investigation for association with risk for child BP-I disorder in a larger sample. Such studies may help reveal mechanisms by which environment can interact with genetic predisposition to influence this severe mental illness.

The membrane-bound transcription factor CREB3L1 is activated in response to virus infection to inhibit proliferation of virus-infected cells

CREB3L1/OASIS is a cellular transcription factor synthesized as a membrane-bound precursor and activated by regulated intramembrane proteolysis in response to stimuli like ER stress. Comparing gene expression between Huh7 subclones that are permissive for hepatitis C virus (HCV) replication versus the nonpermissive parental Huh7 cells, we identified CREB3L1 as a host factor that inhibits proliferation of virus-infected cells. Upon infection with diverse DNA and RNA viruses, including murine γ-herpesvirus 68, HCV, West Nile virus (WNV), and Sendai virus, CREB3L1 was proteolytically cleaved, allowing its NH(2) terminus to enter the nucleus and induce multiple genes encoding inhibitors of the cell cycle to block cell proliferation. Consistent with this, we observed a necessity for CREB3L1 expression to be silenced in proliferating cells that harbor replicons of HCV or WNV. Our results indicate that CREB3L1 may play an important role in limiting virus spread by inhibiting proliferation of virus-infected cells.

Gadd45a and Gadd45g regulate neural development and exit from pluripotency in Xenopus

Gadd45 genes encode a small family of multifunctional stress response proteins, mediating cell proliferation, apoptosis, DNA repair and DNA demethylation. Their role during embryonic development is incompletely understood. Here we identified Xenopus Gadd45b, compared Gadd45a, Gadd45b and Gadd45g expression during Xenopus embryogenesis, and characterized their gain and loss of function phenotypes. Gadd45a and Gadd45g act redundantly and double Morpholino knock down leads to pleiotropic phenotypes, including shortened axes, head defects and misgastrulation. In contrast, Gadd45b, which is expressed at very low levels, shows little effect upon knock down or overexpression. Gadd45ag double Morphants show reduced neural cell proliferation and downregulation of pan-neural and neural crest markers. In contrast, Gadd45ag Morphants display increased expression of multipotency marker genes including Xenopus oct4 homologs as well as gastrula markers, while mesodermal markers are downregulated. The results indicate that Gadd45ag are required for early embryonic cells to exit pluripotency and enter differentiation.

GADD45α and annexin A1 are involved in the apoptosis of HL-60 induced by resveratrol

Resveratrol (3,4',5-trihydroxy-trans-stilbene), one of secondary metabolites of low molecular weight present in plant, has various important biological effects. It can induce apoptosis in human leukemia cell types in vitro, although the mechanism is not fully understood. In the present study, we demonstrated reduced viability and DNA synthesis, as well as increased proportion of the subdiploid cell population, in HL-60 cells as determined by cell cycle analysis with resveratrol. Resveratrol treatment resulted in a gradual time-dependent decrease in the expression of anti-apoptotic Bcl-2 and increase in that of Bax, annexin A1, growth arrest- and DNA damage-induced gene 45α (GADD45α), and cleaved caspase-3. In addition, resveratrol markedly increased caspase-3 activity in cells. Our results suggest that resveratrol could inhibit the proliferation and induce apoptosis of HL-60 cells through a GADD45α and annexin A1/caspase-3 pathway.

Genomics of Acute Lung Injury and Vascular Barrier Dysfunction

Acute lung injury (ALI) is a devastating ­syndrome of diffuse alveolar damage that develops via a variety of local and systemic insults such as sepsis, trauma, ­pneumonia, and aspiration. It is interestingly to note that only a subset of individuals exposed to potential ALI-inciting insults develop the disorder and the severity of the disease varies from complete resolution to death. In addition, ALI susceptibility and severity are also affected by ethnicity as evidenced by the higher mortality rates observed in African-American ALI patients compared with other ethnic groups in the USA. Moreover, marked differences in strain-specific ALI responses to inflammatory and injurious agents are observed in preclinical animal models. Together, these observations strongly indicate genetic components to be involved in the pathogenesis of ALI. The identification of genes contributing to ALI would potentially provide a better understanding of ALI pathobiology, yield novel biomarkers, identify individuals or populations at risk, and prove useful for the development of novel and individualized therapies. Genome-wide searches in animal models have identified a number of quantitative trait loci that associate with ALI susceptibility. In this chapter, we utilize a systems biology approach combining cellular signaling pathway analysis with population- based association studies to review established and suspected candidate genes that contribute to dysfunction of endothelial cell barrier integrity and ALI susceptibility.

Marinobufagenin is an upstream modulator of Gadd45a stress signaling in preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy, in which marinobufagenin (MBG), a circulating cardiotonic steroid, is increased. The Gadd45a stress sensor protein is an upstream modulator of the pathophysiological changes observed in PE. However, the effects of MBG on Gadd45a stress signaling remain unknown. We examined the expression of Gadd45a, the sFlt-1 receptor, and p38, as well as caspase 3 and 8 activities in placental samples from four groups of rats. These were: normal pregnant (NP, n=8); pregnant rats which received weekly injections of desoxycorticosterone acetate and 0.9% saline as their drinking water (PDS, n=9); normal pregnant rats injected with MBG (NPM, n=8); and PDS rats injected with resibufogenin (RBG), an in vivo antagonist of MBG (PDSR, n=8). Utilizing human cytotrophoblast (CTB) cells, we examined the effect of MBG on these stress signaling proteins in vitro. Placental Gadd45a expression, caspase 3 and 8 activities, sFlt-1 concentrations, and sFlt-1 receptor expression were significantly higher in PDS and NPM compared to NP and PDSR rats. Gadd45a protein was significantly upregulated in the CTB cells when MBG was present in concentrations ≥1nM. Treatment with MBG (≥1nM) also significantly arrested cell cycle progression and activated the expression of the Gadd45a-mediated stress signaling proteins. Inhibition of Gadd45a through RNAi-mediation attenuated MBG-induced CTB cell stress signaling. In conclusion, MBG is involved in the alteration in Gadd45a stress signaling both in vivo and in vitro and RBG prevents these changes when administered in vivo.

Antitumor activity of an adenovirus harboring human IL-24 in colon cancer

Data have increasingly shown that melanoma differentiation associated gene-7 (Mda-7/IL-24) has growth suppression activity and can induce apoptosis in many tumor cells, but to our knowledge there have been few studies about its role in colon cancer. We examined its anti-cancer effect on colon cancer. We constructed a recombinant replication-deficient adenovirus carrying human melanoma differentiation associated gene-7 (Ad-IL-24) and examined its apoptosis-inducing efficacy on the colon cancer HT-29 cell line and on an oxaliplatin-resistant cell line HT-29/oxa, using a combination of flow cytometry, growth suppressive activity by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and xenografts. Furthermore, we tested the suppression activity of Mda-7/IL-24 on vascular endothelial growth factor (VEGF) and microvessel density (MVD), as well as the inductive effect on expression of the growth arrest and DNA damage gene (GADD) in xenograft tumors by immunohistochemistry. Melanoma differentiation associated gene-7 can inhibit the growth of colon cancer cell lines and induced apoptosis in about (5.6±0.3)% of HT-29 cells (P<0.05). Xenograft growth was retarded in vivo in mice treated with melanoma differentiation associated gene-7, but the tumor proliferation rate for this group was not significantly different in comparison to controls (P>0.05). Furthermore, melanoma differentiation associated gene-7 induced expression of a growth arrest and DNA damage (GADD) gene and reduced the expression of both VEGF and MVD in xenograft tumors. This study supports a potential therapeutic effect for melanoma differentiation associated gene-7 on colon cancer.

Gadd45a stress signaling regulates sFlt-1 expression in preeclampsia

Preeclampsia, which affects approximately 5-8% of all pregnancies and is one of the leading causes of maternal and fetal morbidity and mortality, is a pregnancy induced complex of multiple pathological changes, including elevated blood pressure, proteinuria and edema manifested after 20 weeks gestation. There is growing evidence that placental stresses during pregnancy, notably hypoxia, and an increase in circulating soluble Flt-1 (sFlt-1) are important in the etiopathogenesis of preeclampsia. How placental stress results in elevated sFlt-1 expression is currently unknown. Here we provide novel data implicating the Gadd45a stress sensor protein as an upstream modulator of pathophysiological changes observed in preeclampsia. It is shown that Gadd45a expression and activation of its downstream effector p38 kinase are elevated in preeclamptic placentas compared to non-preeclamptic controls, and correlate with elevated sFlt-1. Furthermore, a regulatory loop is demonstrated where stress, including hypoxia, IL-6 or hypertonic stress, caused induction of Gadd45a, leading to p38 activation and ultimately increasing sFlt-1 secretion in endothelial cells. These data provide a compelling working frame to further test the role of Gadd45 stress sensors in the etiology of preeclampsia, and set the stage for considering novel therapeutic regimens, including p38 inhibitors, for treatment of preeclampsia.

Apoptotic signaling by c-MYC

c-MYC has a pivotal function in growth control, differentiation and apoptosis, and its abnormal expression is associated with many tumors. Overexpression of c-MYC sensitizes cells to apoptosis by a variety of stimuli. The decision of a cell to undergo apoptosis and how this apoptotic response is regulated by c-MYC depends on the specific cell type and the physiological status of the cell. Multiple cooperating molecular pathways of cell survival and apoptosis determine whether a cell lives or dies, and understanding how c-MYC interfaces with these pathways to influence the survival of cells is important to understand normal and abnormal development, tumor initiation and progression, and response of tumors to different treatment regimens. This article will provide an overview of the function of the tumor suppressor gene product p53 in the c-MYC-mediated apoptotic response and how c-MYC amplifies the intrinsic mitochondrial pathway and triggers and/or amplifies the death receptor pathways. Finally, a model for how deregulated c-MYC prematurely triggers the normal apoptotic response associated with terminal myeloid differentiation while also blocking the differentiation program is presented.

Hypoxia enhances the replication of oncolytic herpes simplex virus

Hypoxia contributes to the resistance of tumors to conventional therapies. We hypothesized that their replication in hypoxic environments like brain or oral mucosa would make oncolytic herpes simplex viruses (HSVs) such as G207 (which has undergone clinical trials) replicate to a greater extent in hypoxic tumors like glioblastoma. Hypoxic cultured U87 cells yielded 4% more wild-type HSV (P = 0.04) and 3.6-fold more G207 (P = 0.001) after 48 hours of infection when compared with normoxic cells. Real-time RT-PCR confirmed a fivefold hypoxia-induced U87 upregulation of GADD34 mRNA, a factor complementing the gamma34.5 gene deletion in G207. The viral yield under conditions of hypoxia, as against normoxia, in GADD34 siRNA-treated U87 cells was 65% of that in control siRNA-treated cells. Treating subcutaneous U87 tumors in athymic mice with erythropoietin lowered the tumoral hypoxic fraction from 57.5 to 24.5%. Tumoral hypoxia dropped to 2.5% during 4 hours/day of hyperbaric chamber treatment. Each tumor-oxygenating maneuver reduced the G207 yield fourfold (P = 0.0001). Oncolytic HSV G207 exhibited enhanced replication in hypoxic environments, partly on account of increased GADD34 expression in hypoxic cells. The unique tropism of oncolytic HSVs for hypoxic environments contrasts with the hypoxia-mediated impairment of standard (radiation, chemotherapy) and other experimental therapies, and enhances HSV's appeal and efficacy in treating tumors like glioblastoma.

Gadd45 in stress signaling

Gadd45 genes have been implicated in stress signaling in response to physiological or environmental stressors, which results in cell cycle arrest, DNA repair, cell survival and senescence, or apoptosis. Evidence accumulated implies that Gadd45 proteins function as stress sensors is mediated by a complex interplay of physical interactions with other cellular proteins that are implicated in cell cycle regulation and the response of cells to stress. These include PCNA, p21, cdc2/cyclinB1, and the p38 and JNK stress response kinases. What deterministic factors dictate whether Gadd45 and partner proteins function in either cell survival or apoptosis remains to be determined. An attractive working model to consider is that the extent of cellular/DNA damage, in a given cell type, dictates the association of different Gadd45 proteins with particular partner proteins, which determines the outcome.

Does imiquimod histologically rejuvenate ultraviolet radiation-damaged skin?

BACKGROUND

Imiquimod (IMI) 5% is believed by some to result in an improved cosmetic appearance of chronically ultraviolet radiation (UV)-damaged skin.

OBJECTIVE

The objective was to determine what histologic and immunohistologic changes were present in actinically damaged skin after treatment with IMI.

METHODS AND MATERIALS

Pre- and posttherapy biopsies of 12 patients with histories of actinic keratoses were evaluated with routine histology and immunohistochemical stains including p53, p63, proliferating cell nuclear antigen (PCNA), c-kit, and Factor XIIIa.

RESULTS

After IMI therapy there was less compact hyperkeratosis, a more uniform rete ridge pattern with a more ordered proliferation of the epidermis, and a decrease in sun-damaged melanocytes. The papillary dermis showed a more uniform cellularity, and there was increased cellularity within the area of solar elastosis. After therapy, staining for p53, p63, and PCNA was decreased within the epidermis; staining for c-kit was decreased but more uniform in the basal cell; and Factor XIIIa expression was increased within the papillary dermis with a more ordered pattern of staining.

CONCLUSION

These morphologic and immunohistochemical patterns may explain some of the improvement in overall skin appearance after IMI therapy and may be related to the spectrum of signaling pathways induced by the imidazoquinolines.

Human non-synonymous single nucleotide polymorphisms can influence ubiquitin-mediated protein degradation

Ubiquitin-mediated proteolysis plays a critical role in the degradation of proteins important in the cellular processes, such as cell cycle/division, differentiation and development, DNA repair, transcriptional regulation, and signaling. It is carried out by a complex cascade of enzymes that contain a high degree of specificity to motifs found in many proteins with rapid turnover. For example, the PEST motifs are hydrophilic stretches of amino acids that serve as signals for proteolytic degradation. In this study, we propose that amino acid altering non-synonymous single nucleotide polymorphisms (nsSNP) result in the abolishment or creation of putative PEST motifs, and thus lead to abnormal stabilization or degradation of the proteins. Using a web-based algorithm, PESTFind, we analyzed a total of 253 nsSNPs from proteins involved in cell cycle (n = 24), DNA repair (n = 128), and TGFbeta signaling pathway (n = 101). Fifteen nsSNPs were located within putative PEST sequences, and 9/15 (60%) either created or abolished these PEST motifs. PEST motifs were abolished in the presence of nsSNPs in CCND3, PMS2, POLE4, SITPEC, and PPARG and putative PEST motifs were created in NEIL2, BIRC4, MLL2, and PPP1R15A. Although experimental analyses are required to confirm these results, they suggest that nsSNPs can induce changes in ubiquitin-mediated protein degradation.