Weiguo Dong

ROS and ROS-Mediated Cellular Signaling

It has long been recognized that an increase of reactive oxygen species (ROS) can modify the cell-signaling proteins and have functional consequences, which successively mediate pathological processes such as atherosclerosis, diabetes, unchecked growth, neurodegeneration, inflammation, and aging. While numerous articles have demonstrated the impacts of ROS on various signaling pathways and clarify the mechanism of action of cell-signaling proteins, their influence on the level of intracellular ROS, and their complex interactions among multiple ROS associated signaling pathways, the systemic summary is necessary. In this review paper, we particularly focus on the pattern of the generation and homeostasis of intracellular ROS, the mechanisms and targets of ROS impacting on cell-signaling proteins (NF-κB, MAPKs, Keap1-Nrf2-ARE, and PI3K-Akt), ion channels and transporters (Ca2+ and mPTP), and modifying protein kinase and Ubiquitination/Proteasome System.

Thymoquinone inhibits growth and augments 5-fluorouracil-induced apoptosis in gastric cancer cells both in vitro and in vivo.

Thymoquinone (TQ), a component derived from the bioactive constituent of black seed (Nigella sativa), has been shown to exert biological activity on various types of human cancers. However, there are few studies addressing its effects on gastric cancer. Here, we present the first report describing the chemosensitizing effect of thymoquinone and 5-fluorouracil (5-FU) on gastric cancer cells both in vitro and in vivo. Studies have shown that pretreatment with TQ significantly increased the apoptotic effects induced by 5-FU in gastric cancer cell lines in vitro. Moreover, we found that TQ enhanced the 5-FU-induced killing of gastric cancer cells by mediating the downregulation of the anti-apoptotic protein bcl-2, the upregulation of the pro-apoptotic protein bax, and the activation of both caspase-3 and caspase-9. In addition to the in vitro results, it has been shown that the combined treatment of TQ with 5-FU represents a significantly more effective antitumor agent than either agent alone in a xenograft tumor mouse model. These data suggest that the TQ/5-FU combined treatment induces apoptosis by enhancing the activation of both caspase-3 and caspase-9 in gastric cancer cells. These results, which provide molecular evidence both in vitro and in vivo, support our conclusion that thymoquinone can activate caspase-3 and caspase-9 and thus result in the chemosensitisation of gastric cancer cells to 5-FU-induced cell death.

Lentiviral‐mediated miRNA against liver‐intestine cadherin suppresses tumor growth and invasiveness of human gastric cancer

Liver‐intestine cadherin (CDH17) represents a novel type of cadherin within the cadherin superfamily, and is distinguished from other cadherins by its distinct structural and functional features. Our previous studies had identified that increased CDH17 was significantly associated with tumor differentiation and lymph node metastasis in gastric cancer. In this study, we tested the hypothesis that CDH17 was associated with proliferation and invasiveness in gastric cancer using recombinant lentivirus‐mediated miRNA targeting to CDH17 both in vitro and in vivo. We also detected the activity of matrix metalloproteinase (MMP)‐2 and MMP‐9 with gelatin zymography to explore the mechanisms underlying the inhibition of the CDH17 gene. Our results showed that a well‐differentiated gastric cancer cell line had higher CDH17 expression. Down‐regulation of CDH17 inhibited proliferation, adherence, and invasion of the poorly differentiated BGC823 gastric cancer cells in vitro, and induced cell cycle arrest. The activities of MMP‐2 and MMP‐9 were lower in the CDH17‐miRNA‐transfected cells compared to the control cells. Using an in vivo tumor growth assay, we confirmed that CDH17 silencing could obviously slow the growth of gastric cancer derived from BGC823 cells. Taken together, we have demonstrated that CDH17 maybe a positive regulator for proliferative, adhesive, and invasive behaviors of gastric cancer. (Cancer Sci 2010)

Meta-analysis of the effects of endoscopy with narrow band imaging in detecting dysplasia in Barrett's esophagus

Narrow band imaging (NBI) is a real-time imaging technique. The aim of this meta-analysis was to estimate the sensitivity, specificity, and diagnostic accuracy on the role of NBI in the detection and characterization of specialized intestinal metaplasia (SIM), high-grade dysplasia (HGD) in the Barretts esophagus. We identified studies by performing a literature search of Medline, EMBASE, and the Cochrane Library databases up to May 2013. We performed data analysis using Meta-DiSc (version 1.4) software. To assess study quality and potential for bias, we used the Quality Assessment of Diagnostic Accuracy Studies-2 tool (QUADAS-2). Overall, seven eligible studies including over 3988 lesions of 502 patients were retrieved. The results showed that endoscopic diagnosis of dysplasia performed using NBI has a high diagnostic performance, with an area under the summary receiver operating characteristic (SROC) curve near 0.90 both in HGD lesions and SIM lesions. We also found that NBI has a sensitive and specificity of 0.91 (95% confidence interval [CI] = 0.86-0.94) and 0.85 (95% CI = 0.76-0.92) on a per-patient element, and 0.97 (95% CI = 0.95-0.98) and 0.64 (95% CI = 0.59-0.68) on a per-lesion element for SIM diagnosis, respectively. The pooled per-patient sensitivity and specificity for identifying HGD are 0.91 (95% CI = 0.75-0.98) and 0.95 (95% CI = 0.91-0.97). The pooled per-lesion sensitivity and specificity for identifying HGD are 0.69 (95% CI = 0.63-0.74) and 0.90 (95% CI = 0.88-0.91). In conclusion, we found that endoscopic diagnosis with NBI is an accurate test to diagnosis dysplasia of Barretts esophagus.

Near-Infrared Light-Responsive Hydrogel for Specific Recognition and Photothermal Site-Release of Circulating Tumor Cells

Isolation of single circulating tumor cells (CTCs) from patients is a very challenging technique that may promote the process of individualized antitumor therapies. However, there exist few systems capable of highly efficient capture and release of single CTCs with high viability for downstream analysis and culture. Herein, we designed a near-infrared (NIR) light-responsive substrate for highly efficient immunocapture and biocompatible site-release of CTCs by a combination of the photothermal effect of gold nanorods (GNRs) and a thermoresponsive hydrogel. The substrate was fabricated by imprinting target cancer cells on a GNR-pre-embedded gelatin hydrogel. Micro/nanostructures generated by cell imprinting produce artificial receptors for cancer cells to improve capture efficiency. Temperature-responsive gelatin dissolves rapidly at 37 °C; this allows bulk recovery of captured CTCs at physiological temperature or site-specific release of single CTCs by NIR-mediated photothermal activation of embedded GNRs. Furthermore, the system has been applied to capture, individually release, and genetically analyze CTCs from the whole blood of cancer patients. The multifunctional NIR-responsive platform demonstrates excellent performance in capture and site-release of CTCs with high viability, which provides a robust and versatile means toward individualized antitumor therapies and also shows promising potential for dynamically manipulating cell-substrate interactions in vitro.

Overexpression of Dickkopf-3 induces apoptosis through mitochondrial pathway in human colon cancer

AIM To investigate the mechanisms of the biological roles of Dickkopf-3 (Dkk-3) in cell invasion, survival and apoptosis in colon cancer cells. METHODS Three human colon cancer cell lines, i.e., HT-29, LoVo and SW480, were used. Overexpression of Dkk-3 induced by pEGFP-N1-Dkk-3-GFP plasmid in LoVo cells was performed using Lipofectamine 2000 reagent. Reverse transcription polymerase chain reaction and Western blotting were performed to determine the mRNA and protein expression levels of Dkk-3, respectively. Cell proliferation assay, cell cycle analysis, hoechst 33258 assay and Matrigel invasion assay were performed on Dkk-3 overexpressing transfectants. RESULTS The mRNA and protein expressions of Dkk-3 in HT-29 (mRNA: 0.06 ± 0.02, protein: 0.06 ± 0.01) and LoVo (mRNA: 0.07 ± 0.02, protein: 0.07 ± 0.02) cells were significantly lower than that in SW480 cells (mRNA: 0.92 ± 0.04, protein: 0.69 ± 0.13; all P < 0.05), and the greatest levels of invasiveness was in LoVo cells. Dkk-3 overexpression inhibited the proliferation and invasion of LoVo cells and induced cell cycle arrest at G(0)/G(1) phase and subsequent apoptosis, as indicated by increased chromatin condensation and fragments, upregulated Bax and cytochrome c protein, downregulated survivin and Bcl-2 protein, and the activation of caspase-3 and caspase-9. Furthermore, Dkk-3 overexpression reduced the accumulation of cytosolic fraction of β-catenin. CONCLUSION Dkk-3 overexpression induced apoptosis in human colon cancer possibly through the mitochondrial pathway. Dkk-3 may be involved in the Wnt/β-catenin signaling pathways in colon cancer.

Analysis of HER2 gene amplification and protein expression in esophageal squamous cell carcinoma

The HER2 gene, which is located on chromosomes 17, is a therapeutic target for cancer. Amplification of HER2 has been described in several tumor types. However, few studies of HER2 gene amplification and protein expression in esophageal carcinoma have been conducted. This study was to investigate the relationship between the expression of HER2/neu and the clinical characteristics, including survival rate, of esophageal squamous carcinoma. The clinical data of 145 patients admitted in Renmin Hospital of Wuhan University, from 2000 to 2005, were reviewed. The HER2 protein expression and gene status in 145 esophageal carcinomas were evaluated using immunohistochemistry and fluorescence in situ hybridization. The survival rate was calculated by the Kaplan–Meier method and the log-rank test using SPSS13.0 software. Compared to normal esophageal epithelium (23/95, 24.2%), HER2 protein was overexpressed in most esophageal squamous carcinoma tissues (60/145, 41.4%), of which 45 (31.0%) were 2+ and 15 (10.4%) were 3+, HER2 overexpression associated significantly with HER2 gene amplification. There is a correlation between the overexpression of HER2 and the differentiation of the carcinoma, the HER2 gene amplification and the differentiation of the carcinoma and the tumor stage. According to univariate analysis, there was a significant difference in survival rates when cases with and without HER-2/neu overexpression or amplification were compared. HER-2/neu amplification/overexpression may be used as an independent prognostic factor in patients with esophageal squamous cancer, and patients with HER-2/neu amplification/overexpression might be potential candidates for new adjuvant therapies that involve the use of humanized monoclonal antibodies.

Noscapine induces mitochondria-mediated apoptosis in human colon cancer cells in vivo and in vitro

Noscapine, a phthalide isoquinoline alkaloid derived from opium, has been widely used as a cough suppressant for decades. Noscapine has recently been shown to potentiate the anti-cancer effects of several therapies by inducing apoptosis in various malignant cells without any detectable toxicity in cells or tissues. However, the mechanism by which noscapine induces apoptosis in colon cancer cells remains unclear. The signaling pathways by which noscapine induces apoptosis were investigated in colon cancer cell lines treated with various noscapine concentrations for 72 h, and a dose-dependent inhibition of cell viability was observed. Noscapine effectively inhibited the proliferation of LoVo cells in vitro (IC(50)=75 μM). This cytotoxicity was reflected by cell cycle arrest at G(2)/M and subsequent apoptosis, as indicated by increased chromatin condensation and fragmentation, the upregulation of Bax and cytochrome c (Cyt-c), the downregulation of survivin and Bcl-2, and the activation of caspase-3 and caspase-9. Moreover, in a xenograft tumor model in mice, noscapine injection clearly inhibited tumor growth via the induction of apoptosis, which was demonstrated using a TUNEL assay. These results suggest that noscapine induces apoptosis in colon cancer cells via mitochondrial pathways. Noscapine may be a safe and effective chemotherapeutic agent for the treatment of human colon cancer.

Blockade of proliferation and migration of gastric cancer via targeting CDH17 with an artificial microRNA

Liver-intestine cadherin (CDH17) is a novel member of the cadherin superfamily implicated in gastric cancer progression. To determine the role of CDH17 in the process of gastric cancer invasive growth, in the present study, RNA interference mediated by recombinant lentivirus vectors expressing artificial CDH17 miRNA was applied to induce a long-lasting down-regulation of CDH17 gene expression in BGC823 cells. The expression levels of CDH17, tumor cell motility, migration potential, and proliferation were measured by flow cytometry, real-time RT–PCR, Western blot analysis, immunofluorescence staining, wound healing assay, and MTT assay, respectively. Results show that four recombinant plasmid expression vectors encoding pre-miRNA against CDH17, pcDNA-CDH17-miR-SR1, -SR2, -SR3, and -SR4 were constructed correctly and down-regulated the CDH17 mRNA levels by 5.5, 57, 91, and 98%, respectively, in BGC823 cells which had an overexpression of CDH17. We packaged the recombinant lentiviral vector for CDH17 RNA interference with pcDNA-CDH17-miR-SR4 which had the highest interfering efficiency and succeeded in construction of the stable transfectants. Of note, more than 90% knockdown of CDH17 expression in BGC823 cells was obtained by miRNA technique. The CDH17-miRNA-transfected cells showed significant decrease in cell proliferation, cell motility, and migration in comparison with the control cells. Thus, we proposed that CDH17 may be an oncogene up-regulating invasive features of gastric cancer cells and could be a hopeful target for the control of gastric cancer progression.

EBP50 gene transfection promotes 5-fluorouracil-induced apoptosis in gastric cancer cells through Bax- and Bcl-2-triggered mitochondrial pathways.

5-Fluorouracil (5-FU) plays an important role in the chemotherapy of advanced gastric cancer. However, genetic factors that affect therapeutic efficacy of 5-FU warrant further investigation. In the present study, using stable transfection of the ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) gene, we explored the genetic influences on 5-FU-induced apoptosis of human gastric cancer cells. Stable overexpression of the EBP50 gene was determined by reverse transcription polymerase chain reaction (RT-PCR) assay and western blot analysis. After treatment with 5-FU, cell growth activities in vitro were investigated by MTT assay. Cell apoptosis was evaluated by Hoechst 33258 staining and flow cytometry of Annexin V-FITC/PI staining. Compared with the BGC823 or BGC823/neo cells, EBP50 mRNA and protein levels in the BGC823/EBP50 cells (EBP50-transfected BGC823 cells) were markedly higher. Chemosensitivity and apoptosis rates of the BGC823/EBP50 cells were higher compared to the BGC823 and BGC823/neo cells following treatment with 5-FU. Stable overexpression of extrinsic EBP50 distinctly increases the 5-FU-induced apoptosis of gastric cancer cells, and is a novel strategy by which to improve the chemosensitivity of gastric cancer to 5-FU.