Zhenguang Chen

Critical role of phosphoinositide 3-kinase cascade in adipogenesis of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent stem cells capable of differentiating into adipocytes in the presence of a hormone cocktail. These cells thus provide a promising model for studying the early events of adipogenesis. Here, we examine the involvement of the PI3K/Akt and mTOR/p70S6K signaling pathways in human MSC adipogenesis. We found that the two pathways were strongly activated with a similar temporal profile under the adipogenesis-inducing hormone cocktail and this activation could be blocked by LY294002, a specific inhibitor of PI3K. Furthermore, rapamycin, a specific inhibitor of mTOR, blocked the activation of mTOR/p70S6K but not PI3K/Akt. Both LY294002 and rapamycin severely suppressed lipid accumulation, as well as the expression of adipogenic markers, including PPARγ2 and C/EBPα, two master adipogenic transcription factors. Together, these data indicate that the mTOR/p70S6K pathway acts downstream of the PI3K/Akt pathway in mediating the adipogenic conversion of MSCs. In conclusion, our data suggest that the PI3K/Akt and mTOR/p70S6K signaling pathways are essential for adipogenesis of human MSCs.

Clinicopathological significance of non-small cell lung cancer with high prevalence of Oct-4 tumor cells.

BackgroundExpression of the stem cell marker octamer 4 (Oct-4) in various neoplasms has been previously reported, but very little is currently known about the potential function of Oct-4 in this setting. The purpose of this study was to assess the prognostic value of Oct-4 expression after surgery in primary non-small cell lung cancer (NSCLC) and investigate its possible molecular mechanism.MethodsWe measured Oct-4 expression in 113 NSCLC tissue samples and three cell lines by immunohistochemical staining and RT-PCR. The association of Oct-4 expression with demographic characteristics, proliferative marker Ki67, microvessel density (MVD), and expression of vascular endothelial growth factor (VEGF) were assessed.ResultsOct-4 expression was detected in 90.3% of samples and was positively correlated with poor differentiation and adenocarcinoma histology, and Oct-4 mRNA was found in each cell lines detected. Overexpression of Oct-4 had a strong association with cells proliferation in all cases, MVD-negative, and VEGF-negative subsets. A Kaplan-Meier analysis showed that overexpression of Oct-4 was associated with shorter overall survival in all cases, adenocarcinoma, squamous cell carcinoma, MVD-negative, and VEGF-negative subsets. A multivariate analysis demonstrated that Oct-4 level in tumor tissue was an independent prognostic factor for overall survival in all cases, MVD-negative, and VEGF-negative subsets.ConclusionOur findings suggest that, even in the context of vulnerable MVD status and VEGF expression, overexpression of Oct-4 in tumor tissue represents a prognostic factor in primary NSCLC patients. Oct-4 may maintain NSCLC cells in a poorly differentiated state through a mechanism that depends on promoting cell proliferation.

Role of the stem cell-associated intermediate filament nestin in malignant proliferation of non-small cell lung cancer.

Background Nestin is associated with neoplastic transformation, but the mechanisms by which nestin contributes to invasion and malignancy of lung cancer remain unknown. Considering that proliferation is necessary for malignant behavior, we investigated the mechanism of nestin action in association with the proliferative properties of non-small cell lung cancer (NSCLC). Methods Nestin expression was examined in NSCLC specimens and cell lines. Associations with clinicopathological features, including prognosis and proliferative markers, were evaluated. Effects of nestin knockdown on proliferation and the signaling pathways involved were further investigated. Results Nestin was expressed in most cancer specimens and all the tumor cell lines analyzed. High nestin expression in malignant tissue was associated with high Ki-67 or PCNA levels and poor patient outcomes. Conversely, knockdown of nestin expression led to significant inhibition of tumor cell proliferation, decreased colony forming ability, and cell cycle G1 arrest. Furthermore, nestin knockdown resulted in inhibition of Akt and GSK3β activation. Conclusions Our data demonstrate that nestin expression in NSCLC cells is associated with poor prognosis of patients and tumor cell proliferation pathway. Downregulation of nestin efficiently inhibited lung cancer cell proliferation, which might be through affecting cell cycle arrest and Akt-GSK3β-Rb signaling pathway.

Expression of nestin in lymph node metastasis and lymphangiogenesis in non-small cell lung cancer patients.

Stem cell marker nestin has been reported to be activated in various neoplasms, and its expression is correlated with poor prognosis. However, nestin expression in non-small cell lung cancer still remains unclear. The present study aimed to investigate nestin expression in 52 tissue samples of non-small cell lung cancer by immunohistochemical staining and explore its correlation with some clinicopathologic characteristics. The associations of nestin with lymphatic vessel density, microvessel density, vascular endothelial growth factor, vascular endothelial growth factor-C, and cyclooxygenase-2 (COX-2) were further observed to determine the linkage between nestin and lymphangiogenesis. The results showed that nestin expressed in tumor cells of 45 samples. High nestin expression correlated significantly with poor differentiation (P = .007), adenocarcinoma (P = .000), N2 lymph node metastasis (P = .006), high microvessel density (P = .033), and lymphatic vessel density (P = .020). Multivariate analysis of N1 and N2 lymph node metastasis revealed a 1.086-fold increase in hazard ratio of N2 lymph node involvement (P = .011) in patients with high nestin expression in primary tumor. More important, multivariate analysis showed a significant correlation of lymphatic vessel density with nestin and vascular endothelial growth factor-C expression (P = .039 and P = .045), independent of vascular endothelial growth factor, COX-2, and other clinicopathologic characteristics. The results demonstrated that nestin expressed in most tumor cells of non-small cell lung cancer tissue and had a direct linkage to lymph node metastasis and tumor-induced lymphangiogenesis, independent of COX-2 signal pathway.

Comparative Clinical Features and Immune Responses After Extended Thymectomy for Myasthenia Gravis in Patients With Atrophic Versus Hyperplastic Thymus

BACKGROUND Although extended thymectomy is believed to be suitable for myasthenia gravis (MG) patients with hyperplastic thymus, it is not clear whether surgical treatment is indicated for MG patients with atrophic thymus. We therefore assessed the clinical features and immune responses in 175 MG patients who underwent thymectomy between 1990 and 2004. METHODS All patients underwent extended thymectomy by the transsternal approach. Clinical features, prognosis, and immune response after extended thymectomy were compared in patients with atrophic and hyperplastic thymuses. RESULTS Of the 175 patients, 47 had atrophic and 128 had hyperplastic thymuses. Although the median times to complete stable remission of the two groups were similar (4.9 versus 4.8 years; p=0.513), the median time to clinical improvement was significantly longer in patients with atrophic thymus (3.3 versus 2.3 years; p=0.005). Patients with atrophic thymus showed a greater increase in ectopic thymus in the anterior mediastinal adipose tissue. Elevated B-cell activating factor receptor, CD19, and CD21 were observed in both hyperplastic and atrophic thymuses, although serum immunoglobulin G concentration after thymectomy increased more in patients with atrophic than in those with hyperplastic thymus. CONCLUSIONS Atrophic thymus may contribute to the progression of MG. Patients with MG who have a atrophic thymus show similar postoperative prognosis as those with hyperplastic thymus, suggesting that surgical therapy should also be considered for the former subset.

Effects of thymic polypeptides on the thymopoiesis of mouse embryonic stem cells

The thymus provides a unique cellular and hormonic microenvironment for the development of immunocompetent T cells. Thymic polypeptides have been widely used clinically for the treatment of tumors, infectious diseases and immune deficiency diseases. They have already shown the ability to stimulate the maturation of hematopoietic stem cells towards the CD3+CD4+ T cell lineage. However, their effects on the thymopoiesis of embryonic stem cells are still unexplored.

Cyclooxygenase-2 up-regulates vascular endothelial growth factor via a protein kinase C pathway in non-small cell lung cancer

BackgroundVascular endothelial growth factor (VEGF) expression is up-regulated via a cyclooxygenase-2 (COX-2)-dependent mechanism in non-small cell lung cancer (NSCLC), but the specific signaling pathway involved is unclear. Our aim was to investigate the signaling pathway that links COX-2 with VEGF up-regulation in NSCLC.Material and methodsCOX-2 expression in NSCLC samples was detected immunohistochemically, and its association with VEGF, microvessel density (MVD), and other clinicopathological characteristics was determined. The effect of COX-2 treatment on the proliferation of NSCLC cells (A549, H460 and A431 cell lines) was assessed using the tetrazolium-based MTT method, and VEGF expression in tumor cells was evaluated by flow cytometry. COX-2-induced VEGF expression in tumor cells was monitored after treatment with inhibitors of protein kinase C (PKC), PKA, prostaglandin E2 (PGE2), and an activator of PKC.ResultsCOX-2 over-expression correlated with MVD (P = 0.036) and VEGF expression (P = 0.001) in NSCLC samples, and multivariate analysis demonstrated an association of VEGF with COX-2 expression (P = 0.001). Exogenously applied COX-2 stimulated the growth of NSCLCs, exhibiting EC50 values of 8.95 × 10-3, 11.20 × 10-3, and 11.20 × 10-3 μM in A549, H460, and A431 cells, respectively; COX-2 treatment also enhanced tumor-associated VEGF expression with similar potency. Inhibitors of PKC and PGE2 attenuated COX-2-induced VEGF expression in NLCSCs, whereas a PKC activator exerted a potentiating effect.ConclusionCOX-2 may contribute to VEGF expression in NSCLC. PKC and downstream signaling through prostaglandin may be involved in these COX-2 actions.

Effects of ischemic preconditioning on ischemia/reperfusion-induced arrhythmias by upregulatation of connexin 43 expression

BackgroundThe susceptibility of hypertrophied myocardium to ischemia-reperfusion injury is associated with increased risk of postoperative arrhythmias. We investigate the effects of ischemic preconditioning (IP) on post-ischemic reperfusion arrhythmias in hypertrophic rabbit hearts.MethodsThirty-three rabbit models of myocardial hypertrophy were randomly divided into three groups of 11 each: non-ischemia-reperfusion group (group A), ischemia-reperfusion group (group B), and ischemic preconditioning group (group C). Another ten healthy rabbits with normal myocardium served as the healthy control group. Rabbit models of myocardial hypertrophy were induced by abdominal aortic banding. Surface electrocardiogram (ECG) was recorded and Curtis-Ravingerova score was used for arrhythmia quantification. Connexin 43 (Cx43) expression was assessed by immunohistochemistry.ResultsRatios of heart weight to body weight and left ventricular weight to body weight increase significantly in the three groups compared with the healthy control group (p < 0.05). Arrhythmia incidence in group C is significantly lower than group B (p < 0.05). Curtis-Ravingerova score in group C is lower than group B (p < 0.05). Cx43 expression area in group A is smaller by comparison with the healthy control group (p < 0.05). Cx43 expression area and fluorescence intensity in group B are reduced by 60.9% and 23.9%, respectively, compared with group A (p < 0.05). In group C, Cx43 expression area increases by 32.5% compared with group B (p < 0.05), and decreases by 54.8% compared with group A (p < 0.05).ConclusionsThe incidence of ischemia/reperfusion-induced arrhythmias in hypertrophic rabbit hearts decreases after IP, which plays an important protecting role on the electrophysiology of hypertrophied myocardium by up-regulating the expression of Cx43.

Frequency of EGFR mutations in lung adenocarcinoma with malignant pleural effusion: Implication of cancer biological behaviour regulated by EGFR mutation

Objective A retrospective single-centre study to compare the clinical features of patients with lung adenocarcinoma with and without epidermal growth factor receptor (EGFR) mutations. Methods Pretreatment medical records of patients with lung adenocarcinoma were reviewed. DNA was extracted from paraffin wax-embedded tumour tissue for analysis of EGFR mutations. Malignant pleural effusion (MPE) was diagnosed by cytopathological testing of pleural fluid. Results EGFR mutations (19-Del and L858R) were recorded in 81/283 patients (28.6%). MPE was found in 42/283 patients (14.8%). In patients with stage IV disease, the frequency of EGFR mutations was higher in those with MPE than in those without MPE. EGFR mutations were independently associated with female sex, no history of smoking and presence of MPE. Conclusions There was a positive association between EGFR mutation and the presence of MPE. EGFR mutations may play an important role in the formation of MPE.

Comparative pulmonary functional recovery after Nuss and Ravitch procedures for pectus excavatum repair: a meta-analysis

BackgroundPectus excavatum (PE) is a common chest wall malformation, with surgery being the only method known to correct the defect. Although the Nuss and Ravitch procedures are commonly used, there is no consensus as to whether surgical repair improves pulmonary function. We therefore investigated whether pulmonary function recovers after surgical repair, and if recovery is dependent on the type of procedure or time after surgery.MethodsLiterature searches were performed using PubMed, EMBASE, Health Periodicals Database, and CNKI (Chinese National Knowledge Index) from January 1990 to December 2007. The following keywords were used: pectus excavatum, chest wall deformity, funnel chest, pulmonary function, respiratory, lung function, and pectus severity index. The primary outcome of interest was possible changes in pulmonary function following surgical repair.ResultsMeta-analysis of 23 studies showed that, although there was evidence of statistically significant heterogeneity among studies (Chi-square, 17.11, p < 0.05), changes in pulmonary functional indices, including forced expiratory volume over 1 s (FEV1), forced vital capacity (FVC), vital capacity (VC), and total lung capacity (TLC), were similar 1 year after the Ravitch and Nuss procedures. Several years after surgery and bar removal, however, the changes in pulmonary functional indices significantly favored the Nuss procedure.ConclusionsPulmonary function tends to improve after the surgical correction of pectus excavatum. Although the Nuss procedure was not significantly better 1 year after surgery, long-term postoperative pulmonary function improvement was significantly better after bar removal.