Qing-liang Wang

Tumor-Associated Microglia/Macrophages Enhance the Invasion of Glioma Stem-like Cells via TGF-β1 Signaling Pathway

The invasion of malignant glioma cells into the surrounding normal brain tissues is crucial for causing the poor outcome of this tumor type. Recent studies suggest that glioma stem-like cells (GSLCs) mediate tumor invasion. However, it is not clear whether microenvironment factors, such as tumor-associated microglia/macrophages (TAM/Ms), also play important roles in promoting GSLC invasion. In this study, we found that in primary human gliomas and orthotopical transplanted syngeneic glioma, the number of TAM/Ms at the invasive front was correlated with the presence of CD133+ GSLCs, and these TAM/Ms produced high levels of TGF-β1. CD133+ GSLCs isolated from murine transplanted gliomas exhibited higher invasive potential after being cocultured with TAM/Ms, and the invasiveness was inhibited by neutralization of TGF-β1. We also found that human glioma-derived CD133+ GSLCs became more invasive upon treatment with TGF-β1. In addition, compared with CD133− committed tumor cells, CD133+ GSLCs expressed higher levels of type II TGF-β receptor (TGFBR2) mRNA and protein, and downregulation of TGFBR2 with short hairpin RNA inhibited the invasiveness of GSLCs. Mechanism studies revealed that TGF-β1 released by TAM/Ms promoted the expression of MMP-9 by GSLCs, and TGFBR2 knockdown reduced the invasiveness of these cells in vivo. These results demonstrate that TAM/Ms enhance the invasiveness of CD133+ GSLCs via the release of TGF-β1, which increases the production of MMP-9 by GSLCs. Therefore, the TGF-β1 signaling pathway is a potential therapeutic target for limiting the invasiveness of GSLCs.

Preferential Expression of Chemokine Receptor CXCR4 by Highly Malignant Human Gliomas and Its Association with Poor Patient Survival

OBJECTIVECXCR4 is implicated in the growth, metastasis, and angiogenesis of malignant tumors. We investigated the potential role of CXCR4 in human gliomas. METHODSThe expression of CXCR4 messenger ribonucleic acid and protein by human glioma cell lines was examined by reverse-transcriptase polymerase chain reaction and immunocytochemistry analysis. Tumor cell chemotaxis and production of vascular endothelial growth factor induced by the CXCR4 ligand SDF-1β were measured. Xenograft models were used for evaluation of glioma cell tumorigenesis. CXCR4 expression by xenografted tumors and primary human glioma specimens were evaluated for CXCR4 protein expression. The relationship between CXCR4 expression and patient survival was analyzed. A synthetic lipoxygenase inhibitor, Nordy, was tested for its effects on glioma cell expression and function of CXCR4, as well as on glioma cell tumorigenicity. RESULTSCXCR4 expression correlated directly with the degree of malignancy of the human glioma cell lines and primary tumors. Activation of CXCR4 induced tumor cell chemotaxis and increased production of vascular endothelial growth factor. Glioma cells expressing higher levels of CXCR4 formed more rapidly growing and lethal tumors in nude mice. Primary human glioma specimens expressing CXCR4 contained high-density microvessels. Patients with CXCR4-positive gliomas had poorer prognosis after surgery. The lipoxygenase inhibitor Nordy diminished CXCR4 expression by glioma cell lines in vitro and reduced their tumorigenicity in nude mice. CONCLUSIONThe level of CXCR4 expression seems to correlate with the degree of malignancy of human gliomas and may contribute to their rapid growth.

The Expression of Functional Chemokine Receptor CXCR4 Is Associated with the Metastatic Potential of Human Nasopharyngeal Carcinoma

Purpose: Chemokine receptors are implicated in metastasis of several malignant tumors. This study was done to evaluate the contribution of chemokine receptors CXCR4 and CCR7 to metastasis of human nasopharyngeal carcinoma. Experimental Design: Reverse transcription-PCR, immunohistochemistry, and flow cytometry were used to evaluate mRNA and protein expression of CXCR4 and CCR7 in nasopharyngeal carcinoma tumor tissues and cell lines. Chemotaxis assays were used to evaluate the function of CXCR4 in nasopharyngeal carcinoma cells. Antisense CXCR4 was used to inhibit receptor expression and to block metastasis of human nasopharyngeal carcinoma cells in vivo in athymic mice. Results: CXCR4 protein was detected in tumor cells in 31 of 40 primary human nasopharyngeal carcinoma and in 13 of 15 lymph node metastases. CXCR4 transcripts were detected in eight CXCR4 protein–positive primary nasopharyngeal carcinoma tissues and seven nasopharyngeal carcinoma cell lines tested. On the other hand, the transcripts for CCR7 were detected only in four primary nasopharyngeal carcinoma tissues and in none of the nasopharyngeal carcinoma cell lines. In functional experiments, metastatic nasopharyngeal carcinoma cell lines that expressed high levels of CXCR4 were found to migrate in response to the CXCR4 ligand SDF-1α. Transfection of antisense CXCR4 in metastatic nasopharyngeal carcinoma cells inhibited the expression of CXCR4 and SDF-1α-induced cell migration in vitro and reduced the capacity of the tumor cells to form metastasis in the lungs and lymph nodes when injected in athymic mice. Conclusion: The expression of functional CXCR4 but not CCR7 is correlated with the metastatic potential of human nasopharyngeal carcinoma cells. Therefore, CXCR4 may be considered as a potential target for the prevention of nasopharyngeal carcinoma metastasis.

Connexin 43 Reverses Malignant Phenotypes of Glioma Stem Cells by Modulating E-Cadherin†‡§

Malfunctioned gap junctional intercellular communication (GJIC) has been thought associated with malignant transformation of normal cells. However, the role of GJIC‐related proteins such as connexins in sustaining the malignant behavior of cancer stem cells remains unclear. In this study, we obtained tumorspheres formed by glioma stem cells (GSCs) and adherent GSCs and then examined their GJIC. All GSCs showed reduced GJIC, and differentiated glioma cells had more gap junction‐like structures than GSCs. GSCs expressed very low level of connexins, Cx43 in particular, which are key components of gap junction. We observed hypermethylation in the promoter of gap junction protein α1, which encodes Cx43 in GSCs. Reconstitution of Cx43 in GSCs inhibited their capacity of self‐renewal, invasiveness, and tumorigenicity via influencing E‐cadherin and its coding protein, which leads to changes in the expression of Wnt/β‐catenin targeting genes. Our results suggest that GSCs require the low expression of Cx43 for maintaining their malignant phenotype, and upregulation of Cx43 might be a potential strategy for treatment of malignant glioma. STEM CELLS 2012; 30:108‐120.

Overexpression of the Transcription Factor MEF2D in Hepatocellular Carcinoma Sustains Malignant Character by Suppressing G2–M Transition Genes

The underlying molecular pathogenesis in hepatocellular carcinoma remains poorly understood. The transcription factor MEF2D promotes survival in various cell types and it seems to function as an oncogene in leukemia. However, its potential contributions to solid cancers have not been explored. In this study, we investigated MEF2D expression and function in hepatocellular carcinoma, finding that MEF2D elevation in hepatocellular carcinoma clinical specimens was associated with poor prognosis. MEF2D-positive primary hepatocellular carcinoma cells displayed a faster proliferation rate compared with MEF2D-negative cells, and silencing or promoting MEF2D expression in these settings limited or accelerated cell proliferation, respectively. Notably, MEF2D-silencing abolished hepatocellular carcinoma tumorigenicity in mouse xenograft models. Mechanistic investigations revealed that MEF2D-silencing triggered G2-M arrest in a manner associated with direct downregulation of the cell-cycle regulatory genes RPRM, GADD45A, GADD45B, and CDKN1A. Furthermore, we identified MEF2D as an authentic target of miR-122, the reduced expression of which in hepatocellular carcinoma may be responsible for MEF2D upregulation. Together, our results identify MEF2D as a candidate oncogene in hepatocellular carcinoma and a potential target for hepatocellular carcinoma therapy.

Incorporation of endothelial progenitor cells into the neovasculature of malignant glioma xenograft

Endothelial progenitor cells (EPCs) are important initiators of vasculogenesis in the process of tumor neovascularization. However, it is unclear how circulating EPCs contribute to the formation of tumor microvessels. In this study, we isolated CD34+/CD133+ cells from human umbilical cord blood (HUCB) and obtained EPCs with the capacities of forming colonies, uptaking acetylated low-density lipoprotein (ac-LDL), binding lectins and expressing vascular endothelial growth factor (VEGF) receptor 2 (VEGFR-2, KDR), CD31 and von Willebrand factor (vWF). These EPCs were actively proliferative and migratory, and could formed capillary-like tubules in response to VEGF. When injected into mice bearing subcutaneously implanted human malignant glioma, EPCs specifically accumulated at the sites of tumors and differentiated into mature endothelial cells (ECs), which accounted for 18% ECs of the tumor microvessels. The incorporation of circulating EPCs into tumor vessel walls significantly affected the morphology and structure of the vasculature. Our results suggest that circulating EPCs constitute important components of tumor microvessel network and contribute to tumor microvascular architecture phenotype heterogeneity.

Tumor microvascular architecture phenotype (T-MAP) as a new concept for studies of angiogenesis and oncology

Heterogeneities exist in endothelial cells and microvascular architecture during tumor angiogenesis. We found significantly variable expression profiles of EC markers, including ephrinB2 and its receptor EphB4, and various types of the architecture. We propose a new concept of tumor microvascular architecture phenotype (T-MAP), reflecting the density, morphology, structure and the three-dimensional distribution of newly formed vessels. The pattern of T-MAP may represent the invasiveness of the tumor therefore predict the outcome of therapy. The presence of T-MAP heterogeneity (T-MAPH) may be utilized as additional diagnostic criteria and for therapeutic designs for antiangiogenesis.

Downregulating FPR restrains xenograft tumors by impairing the angiogenic potential and invasive capability of malignant glioma cells.

G-protein-coupled formylpeptide receptor (FPR) has recently been found to be functionally expressed in gliomas and are probably involved in their malignant biological behavior. In an attempt to explore the therapeutic significance of FPRs, we used wild-type human glioblastoma cells (U87), the corresponding FPR short-interfering RNA transfected (siRNA U87) cells, and mock-transfected U87 cells (mock U87) to establish xenografts in mice brains. Compared to wild-type and mock transfected cells, siRNA U87 cells formed smaller and more well-differentiated xenografts with fewer mitotic figures and more glial filaments within their cytoplasm. The density of microvessels, which presented as a nearly normal morphous, was also decreased significantly in FPR knockdown cells. Moreover, fewer invasive foci could be observed in the xenografts derived from siRNA U87 cells, which also showed a poor migratory capacity in vitro. We suggest that decreased VEGF and MMP-2/-9 expression might be a possible mechanism for the decreasing angiogenic potential and invasive capability of U87 cells after FPR knockdown. Functional FPR might be essential for sustaining the growth and aggressive phenotype of gliomas, and could therefore be a potential therapeutic target.

The ectopic expression of IFN regulatory factor 4-binding protein is correlated with the malignant behavior of human breast cancer cells

Many proteins that are aberrantly expressed in malignant tumors play important roles in promoting tumorigenesis, metastasis and immune escape. IFN regulatory factor 4-binding protein (IBP), which is a novel PH-DH-like protein related to SWAP-70, and functions as an upstream activator of Rho GTPases. It is widely expressed in cells of the immune system and is involved in coupling activated cell receptors to downstream signaling events that mediate cell proliferation, differentiation and polarization. Although IBP was detected in human chondrosarcoma, its function in tumor cells remains unknown. In this study, newly generated monoclonal anti-IBP antibodies were employed and they detected higher level expression of IBP in some human invasive breast carcinoma tissues and in two breast cancer cell lines that form highly invasive tumors in nude mice. In contrast, the levels of IBP mRNA and protein were low or undetectable in normal human breast tissues, benign breast lesions or low-tumorigenic breast cancer cell lines. Over-expression of wild-type IBP in an IBP-negative breast cancer cell line markedly increased its proliferation and invasiveness in vitro. Conversely, RNA interference-mediated knockdown of IBP expression in an IBP-positive breast cancer cell line significantly reduced cell growth and invasiveness. Our results indicate that IBP is expressed in more highly invasive human breast cancer cells, such as MCF-7 and MDA-MB-231, with lower expression in normal breast tissue, benign tumors and less aggressive breast cancer cells, such as SKBR3 and MDA-MB-453. Thus, expression of IBP is correlated with the degree of malignant breast tumors. Nevertheless, it should be pointed our that further study with more tumor types is required to fully elucidate the role of IBP in tumorigenesis and the potential of IBP as a marker for more highly malignant tumors.

Overexpression of the Interferon regulatory factor 4-binding protein in human colorectal cancer and its clinical significance

BACKGROUND IFN regulatory factor 4-binding protein (IBP) is a novel type of activator of Rho GTPases. It has been linked with differentiation and apoptosis of lymphocytes, but its function in oncogenesis remains unclear. Here we studied the expression of endogenous IBP in four human colorectal cancer cell lines, normal, adenoma and tumor colorectal tissues. METHODS Molecular (Western blot and RT-PCR), and confocal analyses were used to investigate IBP expression in human colorectal cancer cell lines. Matched normal and tumor tissue sections of 63 patients and 15 adenoma tissue sections were analyzed for IBP expression by immunohistochemistry (IHC). RESULTS IBP was ubiquitely expressed in human colorectal cancer cell lines. The expression of IBP can be detected at both the mRNA and protein level in SW480, SW620 and HT29 cells. Clinically, IBP were elevated in human colorectal cancer specimens in comparison to normal colorectal tissues. Substantial high expression of IBP was observed in colorectal cancer tissues (67%), whereas corresponding normal tissues and 15 adenoma tissues showed consistently absent immunoreactivity of IBP. Moreover, IBP expression is correlated with the differentiation level of colorectal cancer cells (p<0.05) and clinical stage of patients (p<0.01). CONCLUSIONS Our data show, for the first time, a dysregulated expression of IBP in human colorectal cancer, offering new perspectives for its role in cancer development and progression. IBP may be a novel tumor marker and a therapeutic target for colorectal cancer.