Research on human glioma stem cells in China.

Research on human glioma stem cells began early in the 21st century and since then has become a rapidly growing research field with the number of publications increasing year by year. The research conducted by our diverse group of investigators focused primarily on cell culture techniques, molecular regulation, signaling pathways, cancer treatment, the stem cell microenvironment and the cellular origin and function of glioma stem cells. In particular, we put forward our view that there are inverse or forward transformations among neural stem cells, glial cells and glioma stem cells in glioma tissues under certain conditions. Based on the background of the progress of international research on human glioma stem cells, we aim to share our progress and current findings of human glioma stem cell research in China with colleagues around the world.

[Host glial cell canceration induced by glioma stem cells in GFP/RFP dual fluorescence orthotopic glioma models in nude mice].

OBJECTIVE: During the process of tissue remodeling in human tumor transplantation models, the roles of the inoculated tumor cells and host tissue in tumor progression is still largely unknown. The aim of this study was to investigate the relationships and interactions between these two sides using GFP-RFP double fluorescence tracing technique. METHODS: Red fluorescence protein (RFP) gene was stably transfected into glioma stem cell line SU3, then SU3-RFP cells were transplanted into the brain of athymic nude mice with green fluorescence protein (GFP) expression. After the intracerebral tumors were formed, the relationship and interaction between GFP cells and RFP cells were analyzed. Highly proliferative GFP cells were screened out, and monocloned with micro-pipetting. DNA content assay, chromosome banding and carcinogenicity test of the GFP cells were performed to observe the GFP cells' cancerous phenotype in nude mice. RESULTS: In the transplantable tumor tissue, besides a great quantity of RFP cells, there were still a proportion of GFP cells and GFP/RFP fusion cells. The proportion of RFP cells, GFP cells and GFP/RFP cells were (88.99 ± 1.46)%, (5.59 ± 1.00)%, and (4.11 ± 1.020)%, respectively. Two monoclonal host GFP cells (H1 and H9) were cloned, which demonstrated the properties of immortality, loss of contact inhibition, and ultra-tetraploid when cultured in vitro. Both H1 and H9 cells expressed CNP, a specific marker of oligodendrocytes. The GFP cells also demonstrated 100% tumorigenic rate and high invasive properties in vivo. CONCLUSIONS: In this glioma transplantation model, the transplanted tumor tissues contained not only transplanted glioma stem cells but also cancerous host GFP cells. Our findings offer important clues to further research on the relationships among different members in the tumor microenvironment.

Incubation and application of transgenic green fluorescent nude mice in visualization studies on glioma tissue remodeling.

BACKGROUND: The primary reasons for local recurrence and therapeutic failure in the treatment of malignant gliomas are the invasion and interactions of tumor cells with surrounding normal brain cells. However, these tumor cells are hard to be visualized directly in histopathological preparations, or in experimental glioma models. Therefore, we developed an experimental human dual-color in vivo glioma model, which made tracking solitary invasive glioma cells possible, for the purpose of visualizing the interactions between red fluorescence labeled human glioma cells and host brain cells. This may offer references for further studying the roles of tumor microenvironment during glioma tissue remodeling. METHODS: Transgenic female C57BL/6 mice expressing enhanced green fluorescent protein (EGFP) were crossed with male Balb/c nude mice. Then sib mating was allowed to occur continuously in order to establish an inbred nude mice strain with 50% of their offspring that are EGFP positive. Human glioma cell lines U87-MG and SU3 were transfected with red fluorescent protein (RFP) gene, and a rat C6 glioma cell line was stained directly with CM-DiI, to establish three glioma cell lines emitting red fluorescence (SU3-RFP, U87-RFP, and C6-CM-DiI). Red fluorescence tumor cells were inoculated via intra-cerebral injection into caudate nucleus of the EGFP nude mice. Tumor-bearing mice were sacrificed when their clinical symptoms appeared, and the whole brain was harvested and snap frozen for further analysis. Confocal laser scanning microscopy was performed to monitor the mutual interactions between tumor cells and host brain cells. RESULTS: Almost all the essential tissues of the established EGFP athymic Balb/c nude mice, except hair and erythrocytes, fluoresced green under excitation using a blue light-emitting flashlight with a central peak of 470 nm, approximately 50% of the offsprings were nu/nu EGFP+. SU3-RFP, U87-RFP, and C6-CM-DiI almost 100% expressed red fluorescence under the fluorescence microscope. Under fluorescence microscopic view, RFP+ cells were observed growing wherever they arrived at, locating in the brain parenchyma, ventricles, and para-vascular region. The interactions between the transplanted tumor cells and host adjacent cells could be classified into three types: (1) interweaving; (2) mergence; and (3) fusion. Interweaving was observed in the early stage of tumor remodeling, in which both transplantable tumor cells and host cells were observed scattered in the tumor invading and spreading area without organic connections. Mergence was defined as mutual interactions between tumor cells and host stroma during tumorigenesis. Direct cell fusion between transplantable tumor cells and host cells could be observed occasionally. CONCLUSIONS: This study showed that self-established EGFP athymic nude mice offered the possibility of visualizing tumorigenesis of human xenograft tumor, and the dual-color xenograft glioma model was of considerable utility in studying the process of tumor remodeling. Based on this platform, mutual interactions between glioma cells and host tissues could be observed directly to further elucidate the development of tumor microenvironment.

Expression of miR-125b in the new, highly invasive glioma stem cell and progenitor cell line SU3.

MicroRNA (miR)-125b has been shown to play a potential role in the development of glioma stem cells. However, the relationship between miRNA and glioma stem cells is still elusive. This study was designed to elucidate this potential relationship. We established a highly invasive glioma stem cell and progenitor (GSCP) cell line SU3. SU3 cell suspensions were injected into nude mice brains in situ, and the invasiveness of graft tumors was analyzed using hematoxylin and eosin staining as well as immunohistochemistry. Real-time polymerase chain reaction (PCR) was used to measure the expression levels of miR-125b in SU3 and other cells. In vitro, SU3 cells expressed CD133 and nestin as well as differentiation markers glial fibrillary acidic protein (GFAP) and ß-tubulin III, which were consistent with the characteristics of glioma stem cells. Scratch assays indicated that the migration ability of SU3 cells was stronger than that of U251 stem cells (U251s). In vivo, SU3 cells invaded into each part of the mouse brain from the caudate nucleus in a diffuse pattern and highly expressed invasive and proliferative cell markers matrix metalloprotease 2 (MMP2), MMP9, and Ki-67. Real-time PCR results revealed that the levels of miR-125b and MMP9 were significantly higher in SU3 and SU2, also a highly invasive GSCP cell line we established before, than in U251s. High expression of miR-125b both in newly established GSCPs, SU3, and long-term cultured GSCPs, SU2 suggests that miR-125b exhibits oncogene-like behavior. This behavior should be considered in further studies of miR-125b in cancer stem cells. Furthermore, MMP9, which plays a role in cancer stem cell invasion, may be a target gene of miR-125b.

[Preliminary studies on cell derivation of neovascularization in human glioma and its functional evaluation].

OBJECTIVE: The finding of vasculogenic mimicry (VM) in many solid tumors indicates that tumor cells themselves could participate in the construction of tumor vessels. However the origin of these cells is still not fully elucidated, and whether these vessels have the ability of blood-supply is still unclear. Preliminary studies were performed to investigate whether part of tumor neovascularity is derived from tumor stem cells (TSCs) and whether TSCs-derived vessels are functional. METHODS: Transplanted glioma tissues obtained from subcutaneous and orthotopic transplantation nude mouse models were processed into paraffin sections. In order to identify the cell origin and types of tumor vessels, sections were stained with CD31, CD34, CD133, GFAP, Ki67 and HLA, respectively. CD34-PAS staining was performed as well. A part of tumor-bearing mice were perfused with activated carbon through the systemic circulation and the distribution of activated carbon was observed. RESULTS: CD34-PAS staining showed that endothelium-dependent vessels (CD34(+), PAS(+)), VM vessels (CD34(-), PAS(+)), and the MVs (CD34(+), PAS(-)) could be seen in the transplantated tumors. Activated carbon particles were observed in all three types of vessels. CD31(+) cells adherent to the luminal surface of vessel wall. CD34(+) cells distributed along the vessels as well, but morphologically were more like a transition type between tumor cells and endothelial cells. Human specific Ki67 and HLA positive cells could be seen in the tumor vessels indicating that these vessels were derived from human tumor cells. Moreover, cells of tumor vessels were proved to be constructed by human tumor cells mainly and fusion cells of host cells and tumor cells under confocal microscope. CONCLUSIONS: Three types of blood supply sources including endothelium-dependent vessels, vasculogenic mimicry (VMs) and mosaic vessels (MVs) exist in transplantation tumors of human glioma. Glioma stem and progenitor cells (GSCPs) have the potential to differentiate and transdifferentiate into VMs and MVs.

[Autophagy is involved in 6-OHDA-induced dopaminergic cell death].

OBJECTIVE: To study the role of autophagy in the death of dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA). METHODS: Rat models of Parkinson disease (PD) were established by stereotaxic administration of 6-OHDA (8 µg) into the unilateral substantia nigra par compact (SNpc). Autophagosomes in the SNpc were observed with transmission electron microscopy (TEM), and the expression of autophagy-related protein LC3 was determined with immunofluorescence (IF) assay. RESULTS: Under TEM, the autophagosomes were found in the ipsilateral SNpc 6-24 h after 6-OHDA injection, which suggested the activation of autophagy. IF assay showed significantly increased LC3 expression in 6-OHDA-damaged TH-positive neurons as compared to the control group. CONCLUSIONS: The increase of autophagosomes and activation of autophagy may play a role in dopaminergic neuron death induced by 6-OHDA.

[Preliminary interpretation on the relationship between the phenotype of CD133+ cells and niche in transplanted human glioma in mice].

OBJECTIVE: CD133(+) tumor cells are regarded as cancer stem cells (CSCs), responsible for tumor initiation, development, and relevant with chemo- and radio-resistance of tumors. However, how the destiny of CD133(+) cells is regulated by their niche remains largely unknown. In this study the interpretation of the relationship between CD133(+) cells and their niche were performed through investigating the distribution characteristics of CD133(+) cells in transplanted human glioma xenograft. METHODS: CD133(+) tumor cell spheres or tumor cells transfected with red fluorescent protein (RFP) gene were implanted in situ, subcutaneously or intraperitonealy in nude mice, then the xenografts were dissected and embedded in paraffin, stained with hematoxylin-eosin (HE), tumor tissues were further stained against CD133 with immunohistochemical and immunofluorescent techniques. The pathological structures of tumors and distribution characteristics of CD133(+) tumor cells were observed under microscope and confocal fluorescence microscope. RESULTS: Under microscope, distribution of CD133(+) glioma cells showed certain regularity and can be classified morphologically into three types: cell clusters, in pairs and single cells. Distribution of CD133(+) cells can also be classified according to their distribution location: accumulating around tumor vasculature areas, among the vascular endothelial cells, or in the normal brain tissue and ventricles. Under fluorescence microscope and laser confocal microscope, some of vascular endothelial cells inside the tumor region and some cells around tumor vessels co-express CD133 and RFP. CONCLUSION: CD133(+) tumor cell clusters in nude mice are actually similar to those in CSCs spheres cultured in vitro. The single CD133(+) cells and CD133(+) cells in pairs represent asymmetric and symmetric division of CSCs within the CSCs niche, respectively. CD133(+) cells residing along tumor vessels are CSCs depending on CSC niche, and those locating far away from tumor blood vessels or tumor tissues, residing in normal brain tissues are the disseminated CSCs or neural stem cells which are not controlled or regulated by CSCs niche.

Development of clinically relevant orthotopic xenograft mouse model of metastatic lung cancer and glioblastoma through surgical tumor tissues injection with trocar.

OBJECTIVE: Orthotopic models are important in cancer research. Here we developed orthotopic xenograft mouse model of metastatic lung cancer and glioblastoma with a specially designed system. METHODS: Tiny fragments of surgical tumors were implanted into the mice brain with a trocar system. Immunohistochemistry was performed to detect brain tumor stem cells among glioblastoma tissues, including both the original and resulting ones with monoclonal antibody against CD133. RESULTS: Besides the constant high take rates in both models; brain transplants perfectly resembled their original tumors in biological behaviors. The brain tumor stem cells, positively stained with CD133 were found, though not frequently, in both original and resulting glioblastoma tissues. CONCLUSIONS: Orthotopic model established with a trocar system is effective and injection of tumor tissues containing stem cells promise the forming of new tumor mass when grafted.

Olomoucine inhibits cathepsin L nuclear translocation, activates autophagy and attenuates toxicity of 6-hydroxydopamine.

The finding of nuclear translocation of cathepsin L and its ability to process the CDP/Cux transcription factor uncovers an important role of cathepsin L in control of cell cycle progression. As the expression of certain cell cycle regulators is associated with nigral neuronal death, the present study was sought to investigate if nuclear translocation of cathepsin L and expression of certain cyclins were induced in DA neurons by 6-hydroxydopamine (6-OHDA). The neuroprotective effects of the cell cycle inhibitor olomoucine against 6-OHDA-induced death of nigral neurons were examined. Using immunocytochemistry and real-time PCR we demonstrated that cyclin D1, cyclin B1 and proliferating cell nuclear antigen (PCNA) were aberrantly expressed in some dopaminergic neurons after 6-OHDA infusion. The nuclear translocation of cathepsin L and up-regulation of LC3, a protein involved in autophagy, were observed in nigral DA neurons. Olomoucine, a cyclin dependent kinase (CDK) inhibitor, reduced contralateral rotations and the loss of TH-positive neurons in substantia nigra induced by lesion with 6-OHDA. Pretreatment of rats or primary DA neurons with olomoucine resulted in a partial blockade of nuclear translocation of cathepsin L. Olomoucine also increased the expression of punctate LC3 immunoreactivity, indicating activation of autophagy. These findings suggest that olomoucine may exert neuroprotective effects through inhibiting cathepsin L nuclear translocation and activating autophagy.

Bilobalide inhibits 6-OHDA-induced activation of NF-kappaB and loss of dopaminergic neurons in rat substantia nigra.

AIM: To investigate the effects of bilobalide on the activation of NF-kappaB, and apoptosis of dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA). METHODS: A rat model of Parkinson's disease was produced with a unilateral infusion of 6-OHDA (8 mug) into the substantia nigra par compact. Bilobalide was administered 5, 10, and 20 mg/kg (ip) once a day for 7 d, starting 6 d prior to the 6- OHDA infusion. The rats were subjected to locomotor activity and rotational behavior testing 2 or 3 weeks after the 6-OHDA infusion. The expressions of tyrosine hydroxylase (TH) and NF-kappaB p65 were examined by immunofluorescence. The loss of dopaminergic neurons was detected by Nissl's staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to identify apoptosis. RESULTS: The behavioral changes due to 6-OHDA were significantly restored by bilobalide pretreatment. Bilobalide inhibited the 6-OHDA-induced loss of TH-positive neurons, decreased the activation of NF-kappaB, and protected dopaminergic neurons from apoptosis remarkably. CONCLUSION: NF-kappaB activation contributes to the 6-OHDA-induced loss of dopaminergic neurons, and the inhibition of the NF-kappaB pathway is likely to be involved in the neuroprotective effect of bilobalide.