Guang-Hui Li

STAT3 silencing with lentivirus inhibits growth and induces apoptosis and differentiation of U251 cells

Glioblastoma multiforme (GBM), the most common type of central nervous system tumor in humans, is highly proliferative and resistant to apoptosis associated with genetic mutations that deregulate cell cycle. Signal transduction and activation of transcription 3 (Stat3) is a key signal transduction protein that mediated signaling by cytokines and contributed to oncogenesis. It is constitutively activated in numerous cancers including glioblastoma. To determine the effect on proliferation and differentiation of glioblastoma U251 cells after inhibiting STAT3 expression by RNAi, STAT3 gene was silenced with lentivirus vector in U251 cells. We demonstrate that a lentivirus-based shRNA vector had highly infecting efficiency to U251 cells and lentivirus vector-mediated RNAi significantly suppressed Stat3 expression and activation in U251 cells. Knockdown of STAT3 expression by RNAi suppressed the growth and induced apoptosis of U251 cells by down-regulating expression of Bcl-2. It was found that the cell proportion of G0/G1 phase significantly increased after silencing Stat3 by down-regulating expression of cyclin D1. Knockdown of Stat3 also induces morphological changes of U251 cell. It increases significantly expression of myelin basic protein (MBP) in U251 cells. This study demonstrates that STAT3 silencing with lentivirus effectively inhibits STAT3 gene expression and activation. Stat3 is associated with the survival, growth and differentiation of U251 cells. Lentivirus vector-mediated RNAi may be serve as a novel therapeutic strategy for treatment of GBM with expression constitutively and activation of STAT3 gene.

Activation of the phosphorylation of ATM contributes to radioresistance of glioma stem cells

Ionizing radiation (IR) is currently the most efficient therapy available for malignant glioma. Unfortunately, this strategy is palliative due to the characteristics of radioresistance of malignant glioma. The aim of our study was to compare glioma stem cells (GSCs) with glioma cells (GCs) to determine whether GSCs are responsible for the radioresistance phenotype and to elucidate whether cell cycle checkpoint proteins are responsible for the radioresistance of GSCs. In this study, CD133 (a marker of brain cancer stem cells) and nestin were co-expressed in GSCs isolated from GCs. The percent of CD133+ cells in GSCs and GCs were >80 and <2%, respectively. Significantly more GSCs survived following 2, 4, 6 and 8 Gy IR than GCs. IR kills cancer cells primarily through DNA double-strand breaks (DSBs). The neutral comet assay is often used to intuitively show the level of DSBs. Significantly fewer GSCs showed DNA damage than GCs following 2 Gy IR. This demonstrated that GSCs are more resistant to in vitro radiation than GCs. Furthermore, activated ataxia telangiectasia mutated (ATM) is essential for the activation of downstream effector kinases, such as checkpoint kinase 2 (Chk2) and p53 which mainly contribute to the proper regulation of IR-induced arrest in the G1 phase. DNA damage induced by IR potently initiated activation of phosphorylation of the ATM, p53 and Chk2 checkpoint proteins. Activation of the phosphorylation of these checkpoint proteins was significantly higher in the GSCs compared to GCs. We found that inhibition of ATM activation induced cell cycle checkpoint defects and increased the rate of apoptosis of GSCs following IR. Our results suggest that GSCs were more resistant to radiation compared to GCs due to high expression of phosphorylated cell cycle checkpoint proteins, and inhibition of ATM could significantly reduce the radioresistance of GSCs and GCs. ATM may represent a source of radioresistance in GSCs and a target of improved radiosensitivity of GSCs.

ABCG2 regulates the pattern of self-renewing divisions in cisplatin-resistant non-small cell lung cancer cell lines.

Overexpression of ABCG2 is considered a major mechanism of cancer drug resistance. Recent studies have shown that ABCG2 can regulate the switch between symmetric and asymmetric cell division in adult stem cells; however, the relationship between ABCG2 and cell division in drug-resistant cancer cells remains to be determined. In the present study, we demonstrated that ABCG2 is involved in the cell division of drug-resistant cancer cells. We first established drug-resistant H460 and A549 cell lines by repeated exposure to cisplatin and found that the expression of ABCG2 in these cell lines was significantly increased. As evidenced by PKH-26 staining, these drug-resistant cell lines favored symmetric division, which differed from the asymmetric division of the parental cells. Furthermore, we established stable ABCG2‑overexpressing and stable shRNA-ABCG2‑knockdown cell lines to evaluate the potential role of ABCG2 in cancer cell division. The results showed that overexpression of ABCG2 in A549 parental cells significantly increased the proportion of symmetric division, whereas knockdown of ABCG2 in drug-resistant A549 cells significantly increased the proportion of asymmetric division. Taken together, our findings suggest that ABCG2 is involved in the modulation of cancer drug resistance by regulating the pattern of cell division. The present study provides novel insight into the role of ABCG2 in cancer treatment resistance.

Comparison of Total Body Irradiation Before and After Chemotherapy in Pretreatment for Hematopoietic Stem Cell Transplantation

OBJECTIVE To explore the best time to carry out total body irradiation (TBI) in hematopoietic stem cell transplantation (HSCT) pretreatment. METHODS Retrospective analysis was applied in 88 cases of HSCT using TBI as pretreatment from March 2001 to June 2009 in our hospital. Using 8 MV X-ray, all the patients were irradiated by linear accelerator in 2 consecutive days, with a total dose of 7-11 Gy and an instantaneous dose rate ranging between 4.0 and 5.0 cGy/min. Of the 88 cases, 40 cases were given traditional high-dose chemotherapy before TBI (Group CT/TBI), and 48 cases were given TBI before chemotherapy (Group TBI/CT) instead. RESULTS Eighty-seven cases of transplantation were successful, with no serious complications, including radiation pneumonia. Compared with Group CT/TBI, Group TBI/CT showed similar incidence of complications (p=0.08), similar recent chemotherapy toxicity (p=0.833), and significantly lower recent radiation toxicity (p=0.000). CONCLUSIONS TBI in the pretreatment of HSCT is safe and effective. Using TBI before the high-dose chemotherapy can maintain the same pretreatment effect, effectively reduce apparent immediate reaction/discomfort during TBI, reduce preparation workload of radiotherapy, and lower radiation side-effects. Further research is needed to expand its clinical application.

Effects of Berberine Against Radiation-Induced Intestinal Injury in Mice

PURPOSE Radiation-induced intestinal injury is a significant clinical problem in patients undergoing abdominal radiotherapy (RT). Berberine has been used as an antimicrobial, anti-inflammatory, and antimotility agent. The present study investigated the protective effect of berberine against radiation-induced intestinal injury. METHODS AND MATERIALS The mice were administrated berberine or distilled water. A total of 144 mice underwent 0, 3, 6, 12, or 16 Gy single session whole-abdominal RT and 16 mice underwent 3 Gy/fraction/d for four fractions of fractionated abdominal RT. Tumor necrosis factor-alpha, interleukin-10, diamine oxidase, intestinal fatty acid-binding protein, malonaldehyde, and apoptosis were assayed in the mice after RT. The body weight and food intake of the mice receiving fractionated RT were recorded. Another 72 mice who had undergone 12, 16, or 20 Gy abdominal RT were monitored for mortality every 12 h. RESULTS The body weight and food intake of the mice administered with distilled water decreased significantly compared with before RT. After the same dose of abdominal RT, tumor necrosis factor-alpha, diamine oxidase, intestinal fatty acid-binding protein in plasma and malonaldehyde and apoptosis of the intestine were significantly greater in the control group than in the mice administered berberine (p < .05-.01). In contrast, interleukin-10 in the mice with berberine treatment was significantly greater than in the control group (p < .01). A similar result was found in the fractionated RT experiment and at different points after 16 Gy abdominal RT (p < .05-.01). Berberine treatment significantly delayed the point of death after 20 Gy, but not 16 Gy, abdominal RT (p < .01). CONCLUSION Treatment with berberine can delay mortality and attenuated intestinal injury in mice undergoing whole abdominal RT. These findings could provide a useful therapeutic strategy for radiation-induced intestinal injury.

Overexpression of centrosomal protein 55 regulates the proliferation of glioma cell and mediates proliferation promoted by EGFRvIII in glioblastoma U251 cells

The epidermal growth factor receptor (EGFR) is often amplified in glioma, with the most common extracellular domain mutation being EGFR variant III (EGFRvIII). Abnormal EGFRvIII signaling has been shown to be important in driving tumor progression. Centrosomal protein 55 (CEP55), a member of the centrosomal relative proteins family, participates cytokinesis in the cell cycle. It exists in a few normal tissues and various tumor cells. The expression and function of CEP55 in human glioma cells need to investigate. In this study, the expression of CEP55 was detected in 40 cases of glioma tissues and 10 cases of non-tumor brain tissue. The proliferation of glioblastoma U251 cells was analyzed after transfection with EGFRvIII and CEP55 siRNA. We found that the expression of CEP55 was increased significantly in the glioma tissues than in normal brain tissue. The proliferation of U251 cells increased remarkably after transfection with EGFRvIII. Knockdown of CEP55 inhibited proliferation of U251 cells and was able to eliminate the effect of promoting proliferation induced by EGFRvIII in U251 cells. CEP55 played a key role in the proliferation of glioma cells and mediated EGFRvIII-stimulated proliferation in glioma cells. CEP55 might be a novel molecular therapeutic target in patients with gliomas expressing EGFRvIII.

Inhibition of EGR1 inhibits glioma proliferation by targeting CCND1 promoter

BackgroundGliomas are the most common primary tumors in central nervous system. The prognosis of the patients with glioma is poor regardless of the development of therapeutic strategies. Its aggressive behavior mainly depends on the potent ability of proliferation. The transcription factor EGR1 (early growth response 1) is a member of a zinc finger transcription factor family which plays an essential role in cell growth and proliferation.MethodsEGR1 expression levels in 39 glioma tissues and 10 normal brain tissues were tested by RT-qPCR and Western-blotting. The effects of EGR1 on U251 cells, U251 stem-like cells (GSCs), and U87 cells proliferation were assessed using in vitro and in vivo cell proliferation assays. The specific binding between EGR1 and CCND1 promoter was confirmed by CHIP assay. EGF was used to improve EGR1 expression in this assay.ResultsEGR1 expression levels in human gliomas are decreased compared with normal brain tissues, however, the patients with low EGR1 expression level showed significantly enhanced patient survival in all glioma patients. EGR1 silencing inhibited proliferation and induced G1 phase arrest in glioma cells. EGR1 contributed to proliferation by directly raising CCND1. Meanwhile, EGR1 overexpression induced by EGF was able to promote the proliferation of glioma cells.ConclusionsOur results show that stable knockdown EGR1 would inhibit glioma proliferation. The results suggest EGR1 showing lower expression in cancer tissues compared with normal tissues maybe still play an important role in tumor proliferation.

Microarray analysis of the aberrant microRNA expression pattern in gliomas of different grades

Previous studies have focused on miRNA expression in brain gliomas. However, both the expression pattern of miRNAs in gliomas of different grades and various miRNAs involved in malignant progression of gliomas are poorly understood. In the present study, we used miRNA microarray-based screening to investigate the miRNA expression profile in gliomas, which was further verified by qRT-PCR in selected miRNAs. In total, we found 13 differentially expressed miRNAs between gliomas and their matched surrounding tissues. Among them, 12 miRNAs were upregulated and only one (miR-4489) was downregulated compared with the control. Furthermore, the lower expression level of miR-4489 was confirmed by qRT-PCR in 26 glioma samples. Our microarray result revealed 8, 9 and 15 aberrantly expressed miRNAs in gliomas of World Health Organization (WHO) grade II-IV, respectively. Gene Ontology (GO) and Pathway analysis indicated that target genes of the 13 miRNAs were significantly enriched in central nervous system- and tumor-related biological processes and signaling pathways. The dysregulated miRNAs identified in the present study contribute to the tumorigenesis and malignant progression of gliomas and may serve as useful markers for advanced glioma pathological grading and prognosis.

The clinical feasibility and performance of an orthogonal X-ray imaging system for image-guided radiotherapy in nasopharyngeal cancer patients: Comparison with cone-beam CT

The demand for greater accuracy of intensity-modulated radiotherapy (IMRT) has driven the development of more advanced verification systems for image-guided radiotherapy (IGRT). The purpose of this study is to investigate setup discrepancies measured between an orthogonal X-ray guidance system (XGS-10) and cone-beam computed tomography (CBCT) of Varian in the IMRT of patients with nasopharyngeal cancer (NPC). The setup errors measured by XGS-10 and CBCT at the treatment unit with respect to the planning CTs were recorded for 30 patients with NPC. The differences in residual setup errors between XGS-10 system and CBCT were computed and quantitatively analyzed. The time of image acquisition and image registration was recorded. The radiation doses delivered by CBCT and XGS-10 were measured using PTW0.6CC ionization chambers and a water phantom. The differences between setup errors measured by the XGS-10 system and CBCT were generally <1.5 mm for translations, indicating a reasonably good agreement between the two systems for patients with NPC in the translation directions of A-P (P = 0.856), L-R (P = 0.856) and S-I (P = 0.765). Moreover, compared with CBCT, XGS-10 took much shorter image acquisition and registration time (P <0.001) and delivered only a small fraction of extra radiation dose to the patients (P <0.001). These results indicate that XGS-10 offers high localization accuracy similar to CBCT and additional benefits including prompt imaging process, low imaging radiation exposure, real time monitoring, which therefore represents a potential attractive alternative to CBCT for clinical use.