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Dan Chen

Publications and source records attributed to Dan Chen.

At least 19 recordsLinked to original sources
PubMed2025

Chromatin assembly by the histone chaperone HIRA facilitates Human Papillomavirus replication.

The circular, double-stranded DNA genomes of Human papillomaviruses (HPV) exist in a nucleosomal state throughout the infectious cycle and rely on host histone epigenetic modifications and chromatin assembly processes to promote various phases of the viral life cycle. Here, we show that the histone H3.3 chaperone HIRA and its associated complex members are recruited to HPV replication factories during the late phase of the HPV life cycle. HIRA is also recruited to HPV replication factories generated by amplification of a replicon with a minimal origin and expression of the viral replication proteins E1 and E2, demonstrating that the E1 and E2 proteins are sufficient for HIRA recruitment. Downregulation of HIRA expression reduces HPV31 DNA amplification and viral transcription in differentiated keratinocytes. Histone H3.3 that is highly phosphorylated on serine residue 31 is also enriched at sites of HPV replication and this modification links the DNA damage response to chromatin that supports rapid gene activation. We propose that deposition of histone H3.3 generates viral minichromosomes that are highly primed to support the late stages of the HPV life cycle.

H3.3 phosphorylation↗
PubMed2024

Deciphering the molecular nexus of BTG2 in periodontitis and diabetic kidney disease.

OBJECTIVE: To investigate the role of BTG2 in periodontitis and diabetic kidney disease (DKD) and its potential underlying mechanism. METHODS: Gene expression data for periodontitis and DKD were acquired from the Gene Expression Omnibus (GEO) database. Differential expression analysis identified co-expressed genes between these conditions. The Nephroseq V5 online nephropathy database validated the role of these genes in DKD. Pearson correlation analysis identified genes associated with our target gene. We employed Gene Set Enrichment Analysis (GSEA) and Protein-Protein Interaction (PPI) networks to elucidate potential mechanisms. Expression levels of BTG2 mRNA were examined using quantitative polymerase Chain Reaction (qPCR) and immunofluorescence assays. Western blotting quantified proteins involved in epithelial-to-mesenchymal transition (EMT), apoptosis, mTORC1 signaling, and autophagy. Additionally, wound healing and flow cytometric apoptosis assays evaluated podocyte migration and apoptosis, respectively. RESULTS: Analysis of GEO database data revealed BTG2 as a commonly differentially expressed gene in both DKD and periodontitis. BTG2 expression was reduced in DKD compared to normal conditions and correlated with proteinuria. GSEA indicated enrichment of BTG2 in the EMT and mTORC1 signaling pathways. The PPI network highlighted BTG2's relevance to S100A9, S100A12, and FPR1. Immunofluorescence assays demonstrated significantly lower BTG2 expression in podocytes under high glucose (HG) conditions. Reduced BTG2 expression in HG-treated podocytes led to increased levels of EMT markers (α-SMA, vimentin) and the apoptotic protein Bim, alongside a decrease in nephrin. Lower BTG2 levels were associated with increased podocyte mobility and apoptosis, as well as elevated RPS6KB1 and mTOR levels, but reduced autophagy marker LC3. CONCLUSION: Our findings suggest that BTG2 is a crucial intermediary gene linking DKD and periodontitis. Modulating autophagy via inhibition of the mTORC1 signaling pathway, and consequently suppressing EMT, may be pivotal in the interplay between periodontitis and DKD.

Periodontitis↗
PubMed2007

Bone marrow-derived cells: roles in solid tumor. Minireview.

The role of cancer stem cells has been demonstrated for some cancers. Recently, research indicated that solid tumors may originate from bone marrow stem cells. Bone marrow-derived cells have recently been shown to contribute to stromal formation, especially angiogenesis and lymphvasculogenesis. Moreover, the interaction and the cell fusion between cancer cells and bone mesenchymal stem cells could enhance the aggregative ability of cancer cells. Bone marrow derived cells home to tumor-specific pre-metastatic sites to provide a permissive niche for incoming tumor cells. Since bone marrow-derived cells play an important role in carcinogenesis, angiogenesis and metastasis, bone marrow-derived cells are not only the tool for cancer therapy, but also the targets for cancer therapy.

Bone Marrow Cells↗
PubMed2006

Performance of a new-generation chemiluminescent assay for hepatitis B surface antigen.

BACKGROUND: The usual criteria for analysis of hepatitis B surface antigen (HBsAg) are detection of HBsAg and result confirmation by antibody neutralization. We observed that with the Immulite 2000 HBsAg assay [Diagnostics Product Corporation (DPC)] a relatively high percentage of weakly reactive (WR) samples did not pass the neutralization step. METHODS: For each of 3 lots of Immulite 2000 HBsAg reagent (DPC), we collected and analyzed HBsAg data from approximately 3000 to 4000 patient blood samples and compared these data with HBsAg data from 3393 samples tested with the Abbott Auszyme assay. For 127 samples with initially WR detection signals (relative signal/cutoff index of 1.00-2.5) on the Immulite 2000 HBsAg assay, we then measured hepatitis B (HB) viral load and/or other HB serologic markers. RESULTS: The Immulite 2000 HBsAg assay produced more initially reactive results than the Abbott Auszyme method. Many of these reactive samples, however, were WR and did not meet the confirmation criteria in the neutralization test. Moreover, DNA PCR testing indicated that 22 of the 38 WR samples (58%) that did meet the confirmation criteria had no detectable HB viral DNA. CONCLUSIONS: Immulite 2000 HBsAg assay results include a unique group of WR samples that are associated with both false-positive and false-negative results, regardless of neutralization status, and require careful interpretation. WR HBsAg samples should be reported as confirmed HBsAg reactive only if the samples not only meet the neutralization criteria but also are positive for other HB serologic markers such as anti-HB core total and anti-HB core IgM.

Biomarkers↗
PubMed2006

Effects of Gekko sulfated polysaccharide on the proliferation and differentiation of hepatic cancer cell line.

Gekko swinhonis Gūenther has been used as an anti-cancer drug in traditional Chinese medicine. Gekko sulfated polysaccharide (Gepsin) was investigated for its activity in hepatocellular carcinoma. Hepatocarcinoma cell line (Bel-7402) and liver cell line (L-02) were exposed to Gepsin (100 microg/ml and 10 microg/ml). Gepsin did not suppress the proliferation and viability of normal liver L-02 cells, but strongly inhibited the proliferation of hepatocarcinoma Bel-7402 cells. Gepsin did not induce the apoptosis of Bel-7402 cells, but blocked cells in G2/M phase. Treated with Gepsin, Bel-7402 cells showed ultrastructural features of differentiation. AFP secretion decreased while ALB secretion increased markedly on Gepsin-treated cells. The data show that Gepsin suppressed the proliferation and induced differentiation of hepatocarcinoma, but the toxicity to normal liver cells was negligible.

Animals↗
PubMed2006

Extracellular matrix remodeling in hepatocellular carcinoma: effects of soil on seed?

Extracellular matrix plays two-edged roles, inhibitor and promoter, in the carcinogenesis and progression of hepatocellular carcinoma. On the one hand, extracellular matrix provides the survival signals, and controls the proliferation, differentiation and metastasis of hepatocellular carcinoma. On the other hand, hepatocarcinoma cells create a permissive soil by extracellular matrix remodeling, result in high proliferation, low differentiation, apoptosis block, invasion and metastasis. These malignant phenotypes are related with the change of the capsule around hepatocarcinoma cells that composed by collagens I and IV, the cell-extracellular matrix interaction induced by laminin and its receptor-integrins, and the degradation of ECM which is regulated by proteolytic enzymes and their inhibitor. Thus, normalization of ECM may represent a novel therapeutic strategy for hepatocarcinoma cells.

Adaptation, Physiological↗
PubMed2006

Helicobacter pylori and hepatocellular carcinoma: correlated or uncorrelated?

Helicobacter pylori can be detected in liver tissue resected from patients with hepatocellular carcinoma. Conflicting reports regarding the relationship between H. pylori and hepatocellular carcinoma mean it is uncertain whether H. pylori acts as a troublemaker, co-risk factor or innocent bystander to the development of hepatocellular carcinoma. Clinical studies in patients without known causes of hepatocellular carcinoma are important to discover whether H. pylori is involved in the carcinogenesis of hepatocellular carcinoma. High quality prospective studies in patients with hepatocellular carcinoma, hepatitis C virus infection and no cirrhosis are needed to determine whether H. pylori is a co-risk factor for hepatocellular carcinoma.

Carcinoma, Hepatocellular↗
PubMed2006

Origin of hepatocellular carcinoma: role of stem cells.

The question of whether hepatocellular carcinoma (HCC) arises from the differentiation block of stem cells or dedifferentiation of mature cells remains controversial. Recently, researchers suggested that HCC may originate from the transdifferentiation of bone marrow cells. Interestingly, there are four levels of cells in the hepatic stem cell lineage: bone marrow cells, hepato-pancreas stem cells, oval cells and hepatocytes. Hematopoietic stem cells and the liver are known to have a close relationship in early development. Bone marrow stem cells could differentiate into oval cells, which could differentiate into hepatocytes and duct cells. The development of pancreatic and liver buds in embryogenesis suggests the existence of a common progenitor cell to both the pancreas and liver. Cellular events during hepatocarcinogenesis illustrate that HCC may arise from cells at various stages of differentiation in the hepatic stem cell lineage.

Animals↗
PubMed2006

[Application of 16-slice spiral CT angiography in aortic dissection].

OBJECTIVE: To explore the value of 16-slice spiral CT angiography in the diagnosis of aortic dissection (AD). METHODS: Twenty patients with AD underwent 16-slice spiral CT angiography with multi-planar reformation (MPR), curved planar reformation (CPR), maximum intensity projection (MIP), volume rendering (VR) and CT virtual endoscopy (CTVE). All the original and reconstructed images were studied. RESULTS: The original transverse axial images most reliably preserved the fundamental information. The reconstructed images gave better performance in displaying the spatial relation between the blood vessels and the lesions. Images obtained by different reconstruction methods had different characteristics, and combining different display modes allowed clear representation of the features of aortic dissection such as the extension of the lesion, true and false cavity, disrepair of the intimal flap, aortal branch involvement, thrombi and outcome of endoluminal stenting. CONCLUSION: Multislice spiral CT angiography can fully display the details of aortic dissection and is therefore of important value for the diagnosis and preoperative and postoperative evaluations.

Adult↗
PubMed2006

[The localization of arabinogalactan-proteins in stigma and style of Nicotiana tabacum L].

The distribution patterns of arabinogalactan-proteins (AGPs) in stigma and style of Nicotiana tabacum L. were studied with western blotting, immunohistochemistry and ultracytochemistry techniques. The results showed abundant AGPs accumulated in the stigmas and styles (Fig.1, Plate I). AGPs were mainly distributed in the cytoplasm of epidermal cells and extracellular matrix of the secretory zone of stigma (Plate II) and no significant changes of the distribution of AGPs in stigma were detected before and after pollination. In styles, AGPs were mainly distributed in the outer cell walls of the epidermal cells, the cytoplasm of peripheral cells of vascular bundles and the extracellular matrix of the transmitting tissues (Plate III). As the pollen tube tips penetrated through, the accumulations of AGPs in the extracellular matrix of the stylar transmitting tissues decreased, but abundant AGPs were founded in the cytoplasm and cell walls of the passing pollen tubes (Plate III).

Blotting, Western↗
PubMed2006

[Effects of deltamethrin on permeability of mitochondrial membrane and expression of cytochrome C in brain tissue of rats].

OBJECTIVE: To study the effects of deltamethrin (DM) on the permeability of mitochondrial membrane and the expression of cytochrome C in brain tissue of rats. METHODS: Wistar rats were randomizedly divided into five groups (including four treated groups and one control group). In the treated groups, DM of 12.5 mg/kg was administered intraperitoneally once in rats and the rats were sacrificed 5, 24, 48 and 72 hours later while in the control group, the salad oil of 5 mg/kg was administered intraperitoneally once. The mitochondria in brain tissue of rats were extracted to measure the membrane permeability and the activity of cytochrome C oxidase as well as the expression of cytochrome C in cortex and hippocampus. RESULTS: After the treatment the permeability of mitochondrial membrane was significantly increased in the treated groups compared with the control group. The expression of cytochrome C was increased in cortex and hippocampus CA1 and CA2 5 h, 24 h and 48 h groups and CA4 24 h group (0.57 +/- 0.04, 0.67 +/- 0.09, 0.58 +/- 0.04) and (0.81 +/- 0.18) (P < 0.05 or P < 0.01) while there was no significant difference in the expression of cytochrome C in cortex and hippocampus CA2 72 h group and CA3 and CA4 5 h, 48 h and 72 h groups between the treated groups and the control group (P > 0.05). The activity of cytochrome C oxidase was inhibited (P < 0.01). CONCLUSION: Deltamethrin can significantly increase the permeability of mitochondrial membrane and the expression of cytochrome C in brain tissue of rats.

Animals↗
PubMed2005

Genomic sequence of the pathogenic and allergenic filamentous fungus Aspergillus fumigatus.

Aspergillus fumigatus is exceptional among microorganisms in being both a primary and opportunistic pathogen as well as a major allergen. Its conidia production is prolific, and so human respiratory tract exposure is almost constant. A. fumigatus is isolated from human habitats and vegetable compost heaps. In immunocompromised individuals, the incidence of invasive infection can be as high as 50% and the mortality rate is often about 50% (ref. 2). The interaction of A. fumigatus and other airborne fungi with the immune system is increasingly linked to severe asthma and sinusitis. Although the burden of invasive disease caused by A. fumigatus is substantial, the basic biology of the organism is mostly obscure. Here we show the complete 29.4-megabase genome sequence of the clinical isolate Af293, which consists of eight chromosomes containing 9,926 predicted genes. Microarray analysis revealed temperature-dependent expression of distinct sets of genes, as well as 700 A. fumigatus genes not present or significantly diverged in the closely related sexual species Neosartorya fischeri, many of which may have roles in the pathogenicity phenotype. The Af293 genome sequence provides an unparalleled resource for the future understanding of this remarkable fungus.

Allergens↗
PubMed2005

Chlorinated river and lake water extract caused oxidative damage, DNA migration and cytotoxicity in human cells.

Consumption of chlorinated drinking water is suspected to be associated with adverse health effects, including mutations and cancer. In the present study, the genotoxic potential of water from Donghu lake, Yangtze river and Hanjiang river in Wuhan, an 8-million metropolis in China, was investigated using HepG2 cells and the alkaline version of the comet assay. It could be shown that all water extracts caused dose-dependent DNA migration in concentrations corresponding to dried extracts of 0.167-167 ml chlorinated drinking water per ml medium. To explore whether the intracellular redox status is regulated by chlorinated drinking water, we determined lipid peroxidation (LPO) and depletion of reduced glutathione (GSH). The malondialdehyde (thiobarbituric acid (TBA)-reactive aldehydes) concentration increased after chlorinated drinking water treatment of HepG2 cells in a dose-dependent manner, the GSH content decreased. The activity of lactate dehydrogenase (LDH) increased in chlorinated drinking water treated HepG2 cells indicating cytotoxicity. In accordance with former studies which dealt with in vivo and in vitro micronucleus induction the present study shows that chlorinated drinking water from polluted raw water may entail genetic risks.

China↗
PubMed2005

The Aspergillus fumigatus StuA protein governs the up-regulation of a discrete transcriptional program during the acquisition of developmental competence.

Members of the Asm1p, Phd1p, Sok2p, Efg1p, and StuAp (APSES) family of fungal proteins regulate morphogenesis and virulence in ascomycetes. We cloned the Aspergillus fumigatus APSES gene encoding StuAp and demonstrated that stuA transcription is markedly up-regulated after the acquisition of developmental competence. A. fumigatus DeltastuA mutants were impaired in their ability to undergo asexual reproduction. Conidiophore morphology was markedly abnormal, and only small numbers of dysmorphic conidia were produced, which exhibited precocious germination. Whole genome transcriptional analysis during the onset of developmental competence was performed and identified a subset of developmentally regulated genes that were stuA dependent, including a cluster of putative secondary metabolite biosynthesis genes, genes encoding proteins implicated in the regulation of morphogenesis, and genes encoding allergens and other antigenic proteins. Additionally, hyphae of the DeltastuA mutant displayed reduced expression of the catalase gene CAT1 and were hypersusceptible to hydrogen peroxide.

Amino Acid Sequence↗
PubMed2005

Monoclonal antibodies against soybean Bowman-Birk inhibitor recognize the protease-reactive loops.

Monoclonal antibodies against soybean Bowman-Birk protease inhibitor (BBI) have been generated and used to detect and quantify BBI in foods, soybean germplasm, and animal tissues and fluids. The purpose of this study was to determine the recognition sites of two monoclonal antibodies to BBI (mAb 238 and mAb 217) in relation to the protease-inhibitory sites of BBI. The results showed that (1) the binding of mAb 238 can be blocked by trypsin and that of mAb 217 by chymotrypsin; (2) the trypsin or chymotrypsin inhibitory activities of BBI are blocked by mAb 238 or mAb 217, respectively; and (3) mAb 238 failed to recognize a tryptic loop mutant BBI variant and mAb 217 was unable to bind a chymotryptic loop mutant BBI variant. These findings demonstrate that the epitopes recognized by mAb 238 and mAb 217 reside, at least in part, in the tryptic and chymotryptic loops of BBI, respectively.

Antibodies, Monoclonal↗
PubMed2005

Evaluation of two chemiluminescent immunoassays of ADVIA Centaur for hepatitis B serology markers.

BACKGROUND: This study evaluated the performance of 2 Bayer Hepatitis B Chemiluminescent Assays by comparing their performance to the corresponding DPC Immulite 2000 assays. METHODS: 953 samples were tested by both Immulite 2000 and Centaur HBsAg methods; and 75 samples were tested by both Immulite 2000 and Centaur anti-HBc IgM methods. RESULTS: The overall agreement between Immulite 2000 and ADVIA Centaur anti-HBc IgM assays was 100%. The agreement between Immulite 2000 and Centaur HBsAg assays was 100% for Immulite 2000 positive samples. The overall agreement for HBsAg negative samples was 99.9% after confirmation result was included. However, discrepancy between the 2 assays was observed in 53 samples which were tested initially as "weakly reactive"(index 1.0-1.95) but were not confirmed subsequently by the neutralization test on Immulite 2000. All 53 samples tested negative by Centaur HBsAg assay at the initial run. Furthermore, one Immulite 2000 HBsAg negative sample was reactive and confirmed by Centaur assay. CONCLUSIONS: While the performance of Bayer Hepatitis B HBsAg and aHBc IgM assays are in good agreement with corresponding DPC assays, the Bayer HBsAg assay is more efficient than the Immulite 2000 assay with its better separation of signal and background noise, and its complete automation features.

Automation↗