EFEMP2 is upregulated in gliomas and promotes glioma cell proliferation and invasion

Gliomas are the most common and aggressive form of primary brain tumor. Although EGF-containing fibulin-like extracellular matrix protein 2 (EFEMP2), an extracellular matrix (ECM) glycoprotein, is regarded as a candidate oncogene, little is known about the association of EFEMP2 and gliomas. Here, the expression of EFEMP2 was significantly increased in glioma tissues (n=60) compared to non-tumorous brain tissues (n=25). Silencing of EFEMP2 expression through RNA interference in two glioma cell lines (U87 and U373) remarkably inhibited cell proliferation and G1/S transition. More importantly, EFEMP2 silencing significantly induced cell apoptosis via increasing the ratio of Bax and Bcl-2. Additionally, knockdown of EFEMP2 significantly inhibited the invasive ability of both glioma cells, which was associated with the downregulated expression of metalloproteinase-2 (MMP-2) and MMP-9. In conclusion, expression of EFEMP2 was associated with the oncogenic potential of gliomas and silencing of its expression can suppress cancer cell growth and metastasis. Inhibition of EFEMP2 may be a therapeutic strategy for gliomas.     

Knockdown of HOXC6 inhibits glioma cell proliferation and induces cell cycle arrest by targeting WIF-1 in vitro and vivo

Background

Homeobox C6 (HOXC6) is one of several HOXC genes and is frequently overexpressed in multiple cancers. However, the function and mechanism of HOXC6 in glioma remain unclear.

人恶性胶质瘤细胞裸鼠脑原位移植瘤FPR表达与VEGF关系

目的观测甲酰肽受体(formylpeptide receptor,FPR)在人恶性胶质瘤细胞系U87细胞裸鼠脑原位移植瘤组织中的表达,以及与血管内皮生长因子(VEGF)的关系,探讨FPR在恶性胶质瘤血管生成过程中的作用。方法培养U87细胞,以立体定向注射技术制作U87裸鼠脑原位移植瘤模型;采用间接免疫荧光染色在激光共聚焦显微镜下分别观测FPR在U87细胞和移植瘤组织的表达;免疫组化方法检测VEGF在U87细胞裸鼠脑移植瘤上的表达。结果培养的U87细胞及其原位移植瘤组织均可见FPR表达,定位于瘤细胞胞膜,VEGF阳性着色主要位于胞质,两者阳性表达程度呈正相关性。结论人恶性胶质瘤细胞系U87细胞裸鼠脑原位移植瘤组织存在FPR表达,与VEGF的产生密切相关,在胶质瘤血管生成过程中可能起重要作用。     

MACC1基因在脑胶质瘤中的表达及其对U87细胞凋亡和增殖的影响

目的 探讨MACC1基因与脑胶质瘤的相关性及其表达改变对胶质瘤U87细胞凋亡和增殖能力的影响.方法 荧光定量PCR检测45例脑胶质瘤及相应癌旁组织MACC1基因的表达;设计并合成MACC1基因特异性的siRNA,转染U87细胞;Western blot检测转染后MACCI蛋白的表达;双标流式细胞法检测细胞凋亡;MTT法...     

Is Mda‐7/IL‐24 a Potential Target and Biomarker for Enhancing Drug Sensitivity in Human Glioma U87 Cell Line?

Gliomas are the most common form of primary brain tumor with the highest mortality rates. Drug resistance is a major cause of treatment failure in patients with glioma. Melanoma differentiation associated gene‐7/interleukin‐24 (mda‐7/IL‐24) has been demonstrated to play an important role in drug resistance in human cancer cell lines. However, the reversing effect of mda‐7/IL‐24 on drug resistance of human glioma is not fully clear. Here, we investigated the effects of overexpression of the mda‐7/IL‐24 gene in human glioma. We established a cisplatin‐resistant U87 glioma cell line and found that mda‐7/IL‐24 was highly correlated with drug resistance. Furthermore, we investigated the apoptotic rate, intracellular accumulation of Rhodamine‐123, and expression of glutathione and P‐glycoprotein. The over‐expression of mda‐7/IL‐24 enhanced cisplatin cytotoxicity and reversal of drug resistance in glioma cells. The reversing effect of mda‐7/IL‐24 on drug resistance was induced mainly through the regulation of drug resistance‐related genes and efflux drug pumps. Thus, mda‐7/IL‐24 can be used as a promising predictive biomarker and potential therapeutic target for chemotherapy in glioma. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.     

KDELR2 is an unfavorable prognostic biomarker and regulates CCND1 to promote tumor progression in glioma

BackgroundThe KDEL receptor is a seven-transmembrane-domain protein, which plays a key role in ER quality control and in the ER stress response, KDELR2 involved in regulation of cellular functions, including cell proliferation, survival, promotes glioblastoma tumorigenesis. The aim of this study was to investigate the clinicpathological value and biological role of KDELR2 in glioma.MethodsWe studied the expression of KEDLR2 and its association with the prognosis through the TCGA, CGGA, and GSE16011 database. To explore the role of KDELR2 in glioma, KDELR2 siRNA was constructed and transfected into U87 glioma cells. CCK-8, colony formation and Transwell assays were used to investigate the roles of KDELR2 on GBM cell proliferation. We further studied the effect of KDELR2 on tumorigenesis in animal model. Additionally, flow cytometry was used to monitor the changes in the cell cycle and apoptosis following transfection with KDELR2 siRNA. We applied GeneChip primeview expression array to analysis the differential gene expression profiling. Ingenuity Pathway Analysis to show that KDELR2 has a significant impact in canonical pathway in cell cycle regulation and participate in multiple pathways. And we detected the cell cycle proteins CCND1 expression by Western blot analysis.ResultsOur results showed that KDELR2 was up-regulated in glioma tissue and cell lines. Knockdown KDELR2 was able to reduce cell viability, promote cell cycle arrest at the G1 phase, and induce apoptotic cell death. Moreover, our results suggested that KDELR2 regulated the cellular functions of U87 cells by targeting CCND1. Therefore, we demonstrated that KDELR2 is a novel biomarker in glioma.ConclusionsKDELR2 is highly expressed in human glioma tissues and cell lines, a higher expression of KDELR2 is associated with a poor prognosis of glioma patients. Moreover, KDELR2 regulated the cellular functions of U87 cells by targeting CCND1. The KDELR2/CCND1 axis may provide a new therapeutic target for the treatment of glioma and deepen our understanding of glioma mechanisms.     

胶质瘤miR-218与细胞周期蛋白依赖性激酶6表达的相互关系及其对肿瘤细胞增殖和凋亡的影响

目的 探讨胶质瘤细胞中miR-218及细胞周期蛋白依赖性激酶6(CDK6)表达变化的相互关系及其对肿瘤细胞增殖及凋亡的影响.方法 采用组织微阵列、锁定寡核苷酸探针原位杂交及免疫组织化学(ABC法)方法,检测60例不同级别胶质瘤组织标本及10例对照脑组织中miR-218、CDK6及Ki-67抗原的表达状况,并分析三者之间的相互关系;胶质母细胞瘤细胞系(U87MG)分别被转染阴性对照序列(对照组)及miR-218 mimics(mimics组),采用即时定量聚合酶链反应(qRT-PCR)及免疫细胞化学方法 分别检测两组细胞中的miR-218水平及CDK6和Ki-67表达变化,用单细胞凝胶电泳检测凋亡细胞.结果 对照组、Ⅰ～Ⅱ级、Ⅲ级和Ⅳ级胶质瘤组miR-218阳性标记指数(LI,%)分别为22.45±0.59、4.00±1.07、1.87±1.06、0.94±0.78,四组间差异均有统计学意义(P<0.05);各组CDK6 LI分别为7.25±1.20、16.71±0.80、24.43±0.62、32.05±0.43,对照组与各胶质瘤组间及Ⅳ级组与Ⅰ～Ⅱ级组间差异有统计学意义(P<0.01);各组Ki-67阳性细胞密度分别为0.00±0.00、9.30±3.48、31.15±9.44、60.15±13.60[(±s)/0.05 mm2],各组间差异均有统计学意义(P<0.01);miR-218 LI与CDK6 LI及Ki-67阳性细胞密度间均呈显著性负相关(r=-0.480,-0.534,P<0.01),后两者间呈显著性正相关(r=0.530,P<0.01).mimics组的miR-218水平明显高于对照组,其CDK6及Ki-67 LI(14.74±1.19、30.88±3.31)均明显低于对照组(79.06±2.07、64.94±3.96,P<0.01),而凋亡指数(68.44±7.05)明显高于对照组(13.04±0.97),以上各指标两组间差异均有统计学意义(P<0.01).结论 miR-218表达水平是评价胶质瘤良恶性程度的重要参考指标;其表达异常减少可导致胶质瘤细胞CDK6表达及增殖活性增强;补充外源性miR-218可有效下调恶性胶质瘤细胞CDK6表达、抑制其增殖和促进其凋亡,故在恶性胶质瘤基因治疗中具有重要的潜在应用价值.

Abstract：

Objectives To investigate the relationship between the expression of miR-218 and CDK6 in glioma cells, and their biological impacts on the tumor cell proliferation and apoptosis. MethodsExpression levels of miR-218 as well as CDK6 and Ki-67 proteins were analyzed in 60 cases of gliomas with various grades and 10 control brain tissue samples by tissue microarray, locked oligonucleotide probe in situ hybridization and immunohistochemistry. Glioblastoma multiform cell line (U87MG) was transfected with miR-218 mimics (mimics group) and a control sequence (control group), followed by qRT-PCR detection of miR-218 and immunocytochemical stain of CDK6 and Ki-67, respectively. Single cell gel electrophoresis was used to detect the presence of apoptotic cell. Results The miR-218 labeling indexes (LI) were statistically different (P<0.05) among all groups including control (22.45±0.59) and various glioma groups (grades Ⅰ-Ⅱ 4.00±1.07, grade Ⅲ 1.87±1.06 and grade Ⅳ 0.94±0.78, respectively). The CDK6 LI of the four groups was 7.25±1.20, 16.71±0.80, 24.43±0.62 and 32.05±0.43, respectively. Significant differences existed between the control group and the glioma groups, and between grade Ⅳ and grades Ⅰ-Ⅱ glioma groups (P<0.01). Ki-67 positive cell densities of the above four groups (0.00±0.00, 9.30±3.48, 31.15±9.44 and 60.15±13.60) were significantly different from one and another (P<0.01). The expression of miR-218 negatively correlated with CDK-6 LI (r=-0.480, P<0.01) and Ki-67 positive cell density (r=-0.534, P<0.01), while the latter two positively correlated with each other (r=0.530, P<0.01). U87MG transfection experiment showed that the miR-218 level of the mimics group was significantly higher than that of the control group (P<0.01). CDK6 and Ki-67 LI of the mimics group (14.74±1.19 and 30.88±3.31) were significantly lower than those of the control group (79.06±2.07 and 64.94±3.96, P<0.01), whilst its apoptotic index (AI) (68.44±7.05) was significantly higher than that of the control group (13.04±0.97, P<0.01). Conclusions The expression level of miR-218 is an important reference indicator for the assessment of the grade of gliomas. An aberrant decrease of its expression may lead to an increase of the CDK6 expression and proliferative activity of giloma cells. Introducing exogenous miR-218 may effectively down-regulate the CDK6 expression, inhibit cell proliferation and induce apoptosis of malignant giloma cells. These findings imply that miR-218 may serve as a therapeutic agent against malignant glioma.     

Participation of host cells: resistance or collaboration

Matrix metalloproteinases play an important regulatory role in tissue morphogenesis, cell differentiation and motility, and tumor cell invasiveness. We have recently demonstrated elevated activity of the 92 kDa type IV collagenase (MMP-9) in human glioblastoma and in the present study examine the relative amounts of MMP-9 protein and mRNA in human gliomas and as well as the distribution of MMP-9 in human glioma tumors in vivo. Using an enzyme-linked immunosorbent assay for the quantitative determination of MMP-9 protein, we found that levels were significantly higher in malignant astrocytomas, especially in glioblastoma multiforme, than in normal brain tissues and low-grade gliomas. In addition, the amount of MMP-9 mRNA, as determined by northern blot analysis was higher in anaplastic astrocytomas and glioblastoma multiforme than in normal brain tissue and low-grade gliomas. Immunocytochemical staining for MMP-9 showed strong cytoplasmic immunoreactivity in the tumor cells and the proliferating endothelial cells of glioblastoma multiforme and anaplastic astrocytomas. The staining intensity was lower in low-grade astrocytomas, and was undetectable or very low in normal brain astrocytes. The results indicate that expression of MMP-9 is dramatically upregulated in highly malignant gliomas and correlates with the highly malignant progression of human gliomas in vivo, and support a role for the MMP-9 in facilitating the invasiveness seen in malignant gliomas in vivo.     

High expression of immunity-related GTPase family M protein in glioma promotes cell proliferation and autophagy protein expression

Glioma is the commonest malignant tumor in the central nervous system (CNS), characterized by rapid growth. However, the molecular mechanism underlying the growth remains unclear. Immunity-related GTPase family M protein (IRGM) participates in immune response to pathogen and tumorigenesis. Proliferation and autophagy are two crucial functions contributing to aggressive growth. Therefore, our aims were to probe whether IRGM regulates glioma proliferation and autophagy. In this study, we found that 47 glioma specimens had more IRGM expression than 11 non-cancerous brain tissues with immunohistochemistry. IRGM was also up-regulated in human glioma cell lines U87, U251 and A172 and so on compared with immortalized astrocytes. Importantly, overexpression of IRGM significantly increased the cell colonies formation, cell proliferation and Akt activation (Thr308 and Ser473 sites) than matched control. On another hand, all of IRGM, autophagy marker LC3II and autophagy adaptor p62 gradually increased after starvation 2 and 4?h. Furthermore, western blot and immunofluorescence results showed that knockdown of IRGM inhibited the formation of LC3-II and the expression of p62. Our data uncovered that IRGM acted in glioma proliferation and autophagy, providing a new target with dual roles for the future translation research.     

Receptor-targeted quantum dots: fluorescent probes for brain tumor diagnosis

The intraoperative diagnosis of brain tumors and the timely evaluation of biomarkers that can guide therapy are hindered by the paucity of rapid adjunctive studies. This study evaluates the feasibility and specificity of using quantum dot-labeled antibodies for rapid visualization of epidermal growth factor receptor (EGFR) expression in human brain tumor cells and in surgical frozen section slides of glioma tissue. Streptavidin-coated quantum dots (QDs) were conjugated to anti-EGFR antibodies and incubated with target cultured tumor cells and tissues. The experiments were conducted first in human glioma tumor cell lines with elevated levels of EGFR expression (SKMG-3, U87) and then in frozen tissue sections of glioblastoma multiforme and of oligodendroglioma. The bioconjugated QDs used in the study were found to bind selectively to brain tumor cells expressing EGFR. QD complexed quickly to the cell membrane (less than 15 min), and binding was highly specific and depended on the expression level of EGFR on the cell membrane. Tissue experiments showed that only tumor specimens expressing EGFR were labeled in less than 30 min by QD complexes. These findings demonstrate that QD-labeled antibodies can provide a quick and accurate method for characterizing the presence or absence of a specific predictive biomarker.     

Knockdown of microRNA-127 reverses adriamycin resistance via cell cycle arrest and apoptosis sensitization in adriamycin-resistant human glioma cells

The aim of this study was to investigate signaling pathways for reversal of microRNA-127-mediated multi-drug resistance (MDR) in gliomas cells. Adriamycin-resistant glioma cell lines U251/adr and U87-MG/adr were established and we found that anti-microRNA-127 markedly reduced microRNA-127 expression levels in a time-dependent manner, leading to distinct inhibition of cell proliferation and increased apoptosis and the content of intracellular Rh123. Silencing of microRNA-127 significantly increased the sensitivity of U251/ADR and U87-MG/adr cells to adriamycin, compared to cells transfected with negative control siRNA. Silencing of microRNA-127 also significantly reduced the mRNA and protein expression levels of MDR1 and MRP1, which are major ATP-binding cassette (ABC) transporter linked to multi-drug resistance in cancer cells. And Runx2, p53, bcl-2 and survivin, which are important role in cell apoptosis, also markedly changed after microRNA-127 silencing. In addition, down-regulating microRNA-127 decreased the level of phosphorylated-Akt. Our data indicate that down-regulation of micorRNA-127 can trigger apoptosis and overcome drug resistance of gliomas cells. Therefore, this resistance of adriamycin in gliomas can be cancelled by silencing expression of microRNA-127.     

Expression of complement membrane regulators membrane cofactor protein (CD46), decay accelerating factor (CD55), and protectin (CD59) in human malignant gliomas.

Gliomas are malignant brain tumors, which, despite recent progress in surgical and radiological treatment, still have a poor prognosis. Since gliomas apparently resist immunological clearance mechanisms, we became interested in examining bow gliomas resist killing by the human complement system. The resistance of human cells to complement-mediated damage is, in large part, mediated by specific inhibitors of complement:membrane cofactor protein (CD46), decay-accelerating factor (CD55), and protectin (CD59). In the present study we examined the expression of complement regulators in 14 human glioma tumors and in 7 glioma cell lines (U251, U87, HS683, U373, U138, U118, and H2). Protectin was found to be strongly expressed by all glioma tumors and cell lines. Northern blotting analysis demonstrated the typical pattern of four to five protectin mRNAs in the glioma cells. Except for blood vessels, the expression of decay-accelerating factor was weak or absent in the tumors in situ, whereas in the cell lines its expression varied, ranging from negative to intermediate. Membrane cofactor protein was moderately expressed by all the cell lines but only weakly in the tumors. Cell-killing experiments demonstrated that the glioma cell lines were exceptionally resistant to C-mediated lysis. Five of the seven cell lines (U373, HS683, U118, U138, and H2) resisted complement lysis under conditions where most other cell lines were sensitive to killing. Neutralization experiments using specific monoclonal antibodies indicated that protectin was functionally the most important complement regulator in the glioma cells. The killing of the U87 and U251 cells could be significantly increased by a blocking anti-protectin monoclonal antibody, whereas for the other cell lines only moderate or no response was observed. The H2 cell line resisted killing by all antibodies and by complement. These results show that protectin is the most important complement regulator on human glioma cells. The exceptional complement resistance of some glioma cell lines suggests that they may utilize other, hitherto less well characterized, mechanisms to resist complement killing.     

EphB2/R-Ras signaling regulates glioma cell adhesion, growth, and invasion

Eph receptor tyrosine kinases mediate neurodevelopmental processes such as boundary formation, vasculogenesis, and cell migration. Recently, we found that overexpression of EphB2 in glioma cells results in reduced cell adhesion and increased cell invasion. Since R-Ras has been shown to play a critical role in EphB2 regulation of integrin activity, we explored whether the biological role of EphB2 in glioma invasion is mediated by downstream R-Ras activation. On EphB2 activation, R-Ras associated with the receptor and became highly phosphorylated. Depletion of endogenous R-Ras expression by siRNA abrogated EphB2 effects on glioma cell adhesion, proliferation, and invasion in ex vivo rat brain slices. Anti-proliferative responses to EphB2 activation were consistent with suppressed mitogen-activated protein kinase activity. Moreover, R-Ras was highly phosphorylated in the invading glioma cells. In human brain tumor specimens, R-Ras expression and phosphorylation correlated with increasing grade of gliomas. Laser capture microdissection of invading glioblastoma cells revealed elevated R-Ras mRNA (1.5- to 26-fold) in 100% (eight of eight) of biopsy specimens, and immunohistochemistry revealed high R-Ras localization primarily in glioblastoma cells. The phosphorylation ratio of R-Ras positively correlated with the phosphorylation ratio of EphB2 in glioblastoma tissues. These results demonstrate that R-Ras plays an important role in glioma pathology, further suggesting the EphB2/R-Ras signaling pathway as a potential therapeutic target.     

CBX8过表达或沉默对人神经胶质瘤细胞增殖和凋亡的影响

目的:探究染色质结构域蛋白8(chromodomain protein 8,CBX8)对人神经胶质瘤细胞增殖与凋亡的作用。方法:Western blot和RT-qPCR检测组织及细胞系中CBX8的表达。构建过表达CBX8和沉默CBX8载体,转染神经胶质瘤细胞T98G和U87MG,分别用MTT法和BrdU实验检测细胞增殖,流式细胞术检测细胞凋亡。结果:与正常脑组织和星形胶质细胞相比,神经胶质瘤组织及细胞中的CBX8蛋白和mRNA水平明显上升。在T98G和U87MG细胞中,过表达CBX8均促进细胞增殖,抑制细胞凋亡,并上调Rb/E2F1的表达水平,而沉默CBX8则作用相反。sh-E2F1转染细胞之后,cyclin D1的表达以及Bcl-2/Bax的比值降低。结论:CBX8可能通过Rb/E2F1通路调节胶质瘤细胞的增殖和凋亡。     

The human Fn14 receptor gene is up-regulated in migrating glioma cells in vitro and overexpressed in advanced glial tumors

Glioblastoma multiforme comprises the majority of human brain tumors. Patients with glioblastoma multiforme have poor survival rates, with an average life expectancy of <1 year. To assess possible mechanisms and to potentially target invasive glioma cells, we previously measured the gene expression profiles of glioma cells under migration-activated or passive states. One of the genes identified was Fn14, which encodes a cell surface receptor for the tumor necrosis factor superfamily member named TWEAK. In this study, we show that Fn14 gene expression is induced in migration-activated glioma cells in vitro and significantly increases according to tumor grade in vivo (P < 0.01), with highest levels in glioblastoma tissue specimens. The in situ expression pattern of Fn14 mRNA and protein was confined to primary glioma cells and the vascular endothelium, with no detection in adjacent normal brain. Conversely, TWEAK mRNA levels are low in glioblastoma samples relative to normal brain tissue. In addition, activation of the Fn14 receptor by addition of recombinant TWEAK resulted in increased glioma cell migration in vitro. These results suggest a positive role for TWEAK and Fn14 in glioma progression and indicate that Fn14 gene expression may serve as a marker for invasive glioma cells.     

CBX3在脑胶质瘤中的表达分析及其对胶质瘤细胞凋亡的抑制作用

目的 通过对胶质瘤公共数据库中CBX3表达量的分析,明确其与胶质瘤预后的相关性。流式细胞术以及对凋亡指标的检测分析其对胶质瘤细胞系凋亡水平的影响。 方法 通过对TCGA以及CGGA中胶质瘤患者基因芯片的数据进行分析,比较CBX3在不同级别胶质瘤中的表达量以及分析CBX3表达量与胶质瘤患者预后之间的关系。GO和Pathway分析对CBX3基因进行功能注释。最后在细胞系中探索CBX3基因对胶质瘤细胞系凋亡水平的影响。 结果 高级别胶质瘤中CBX3表达量明显高于低级别的胶质瘤中CBX3的表达量(P<0.01) 。高表达CBX3的患者预后比低表达CBX3的患者更差( P<0.05)。同时流式细胞术实验发现过表达CBX3可以显著降低胶质母细胞瘤细胞系U87MG和T98G的凋亡水平。 结论 CBX3的表达水平与胶质瘤的生存期呈负相关关系,高表达 CBX3可以降低胶质母细胞瘤细胞系的凋亡水平,故而CBX3或许可作为判断胶质母细胞瘤预后的有效指标。     

Platelet-derived growth factor-B enhances glioma angiogenesis by stimulating vascular endothelial growth factor expression in tumor endothelia and by promoting pericyte recruitment

Platelet-derived growth factor (PDGF)-B and its receptor (PDGF-R) beta are overexpressed in human gliomas and responsible for recruiting peri-endothelial cells to vessels. To establish the role of PDGF-B in glioma angiogenesis, we overexpressed PDGF-B in U87MG glioma cells. Although PDGF-B stimulated tyrosine phosphorylation of PDGF-Rbeta in U87MG cells, treatment with recombinant PDGF-B or overexpression of PDGF-B in U87MG cells had no effect on their proliferation. However, an increase of secreted PDGF-B in conditioned media of U87MG/PDGF-B cells promoted migration of endothelial cells expressing PDGF-R beta, whereas conditioned media from U87MG cells did not increase the cell migration. In mice, overexpression of PDGF-B in U87MG cells enhanced intracranial glioma formation by stimulating vascular endothelial growth factor (VEGF) expression in neovessels and by attracting vessel-associated pericytes. When PDGF-B and VEGF were overexpressed simultaneously by U87MG tumors, there was a marked increase of capillary-associated pericytes as seen in U87MG/VEGF(165)/PDGF-B gliomas. As a result of pericyte recruitment, vessels induced by VEGF in tumor vicinity migrated into the central regions of these tumors. These data suggest that PDGF-B is a paracrine factor in U87MG gliomas, and that PDGF-B enhances glioma angiogenesis, at least in part, by stimulating VEGF expression in tumor endothelia and by recruiting pericytes to neovessels.