Vascular gene expression patterns are conserved in primary and metastatic brain tumors

Department of Neurosurgery, University of Rochester, 601 Elmwood Avenue, Box 670, Rochester, NY 14642, USA.
Journal of Neuro-Oncology (Impact Factor: 3.07). 08/2010; 99(1):13-24. DOI: 10.1007/s11060-009-0105-0
Source: PubMed


Malignant primary glial and secondary metastatic brain tumors represent distinct pathological entities. Nevertheless, both tumor types induce profound angiogenic responses in the host brain microvasculature that promote tumor growth. We hypothesized that primary and metastatic tumors induce similar microvascular changes that could function as conserved angiogenesis based therapeutic targets. We previously isolated glioma endothelial marker genes (GEMs) that were selectively upregulated in the microvasculature of proliferating glioblastomas. We sought to determine whether these genes were similarly induced in the microvasculature of metastatic brain tumors. RT-PCR and quantitative RT-PCR were used to screen expression levels of 20 candidate GEMs in primary and metastatic clinical brain tumor specimens. Differentially regulated GEMs were further evaluated by immunohistochemistry or in situ hybridization to localize gene expression using clinical tissue microarrays. Thirteen GEMs were upregulated to a similar degree in both primary and metastatic brain tumors. Most of these genes localize to the cell surface (CXCR7, PV1) or extracellular matrix (COL1A1, COL3A1, COL4A1, COL6A2, MMP14, PXDN) and were selectively expressed by the microvasculature. The shared expression profile between primary and metastatic brain tumors suggests that the molecular pathways driving the angiogenic response are conserved, despite differences in the tumor cells themselves. Anti-angiogenic therapies currently in development for primary brain tumors may prove beneficial for brain metastases and vice versa.

Download full-text


Available from: Mahlon Johnson, Sep 05, 2014
  • Source
    • "Recently, a number of studies have attempted to characterize the genes involved in pathological processes of adult vasculature (24–26). The Cre conditional system combined with the inducible tTA system used in the present study enables the deletion of a gene or expression of a mutated gene at any time point during the lifespan of the mice. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the present study, the tetracycline-off and Cre/loxP systems were combined to gain temporal and spatial control of transgene expression. Mice were generated that carried three transgenes: Tie2-tTA, tet-O-Cre and either the ZEG or ZAP reporter. Tie2-tTA directs expression of tetracycline-controlled transactivator (tTA) in endothelial and hematopoietic cells under the control of the Tie2 promoter. Tet-O-Cre produces Cre recombinase from a minimal promoter containing the tet-operator (tetO). ZEG or ZAP contains a strong promoter and a loxP-flanked stop sequence, followed by an enhanced green fluorescence protein (EGFP) or human placental alkaline phosphatase (hPLAP) reporter. In the presence of tetracycline, the tTA transactivator produced by Tie-2-tTA is disabled and Cre is not expressed. In the absence of tetracycline, the tTA binds tet-O-Cre to drive the expression of Cre, which recombines the loxP sites of the ZEG or ZAP transgene and results in reporter gene expression. In the present study, the expression of the ZEG or ZAP reporter genes in embryos and adult animals with and without tetracycline treatment was examined. In the presence of tetracycline, no reporter gene expression was observed. When tetracycline was withdrawn, Cre excision was activated and the reporter genes were detected in endothelial and hematopoietic cells. These results demonstrate that this system may be used to bypass embryonic lethality and access adult phenotypes.
    Full-text · Article · Nov 2014 · Experimental and therapeutic medicine
  • Source
    • "CXCR7−/− mice die in the first week after birth due to abnormal cardiovascular development, suggesting a critical role for CXCR7 in endothelial biology and cardiac development [16], [17]. We originally identified CXCR7 (then called RDC1) as a selective marker of glioblastoma (GBM) derived microvascular endothelial cells and confirmed that it was induced in the tumor endothelium of both primary and metastatic malignant brain tumors [18], [19]. CXCR7 expression increased with brain tumor grade [20], [21] and elevated CXCR7 mRNA levels correlate with poor survival in glioma patients (Liu Y, unpublished data). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The chemokine CXCL12 regulates multiple cell functions through its receptor, CXCR4. However, recent studies have shown that CXCL12 also binds a second receptor, CXCR7, to potentiate signal transduction and cell activity. In contrast to CXCL12/CXCR4, few studies have focused on the role of CXCR7 in vascular biology and its role in human brain microvascular endothelial cells (HBMECs) remains unclear. In this report, we used complementary methods, including immunocytofluorescence, Western blot, and flow cytometry analyses, to demonstrate that CXCR7 was expressed on HBMECs. We then employed short hairpin RNA (shRNA) technology to knockdown CXCR7 in HBMECs. Knockdown of CXCR7 in HBMECs resulted in significantly reduced HBMEC proliferation, tube formation, and migration, as well as adhesion to matrigel and tumor cells. Blocking CXCR7 with a specific antibody or small molecule antagonist similarly disrupted HBMEC binding to matrigel or tumor cells. We found that tumor necrosis factor (TNF)-α induced CXCR7 in a time and dose-response manner and that this increase preceded an increase in vascular cell adhesion molecule-1 (VCAM-1). Knockdown of CXCR7 resulted in suppression of VCAM-1, suggesting that the reduced binding of CXCR7-knockdown HBMECs may result from suppression of VCAM-1. Collectively, CXCR7 acted as a functional receptor for CXCL12 in brain endothelial cells. Targeting CXCR7 in tumor vasculature may provide novel opportunities for improving brain tumor therapy.
    Full-text · Article · Aug 2014 · PLoS ONE
  • Source
    • "The transcriptomic analysis strongly suggests that the persistent upregulation of several genes involved in matrix degradation and inflammation is mainly responsible for the delayed angiogenesis in the infarcted area of aged rats. In response to prolonged hypoxia, fibroblasts degrade type I collagen, one of the major extracellular proteins of the vasculature, and the available evidence suggests that type I collagenolysis is mediated by secreted as well as membrane-anchored members of the matrix metalloproteinase (MMP) gene family, including Mmp8, Mmp12, and Mmp14 (Sabeh et al., 2009; Liu et al., 2010). In young animals, the MMPs are strongly upregulated early after stroke, but then decrease or remain at the same level by day 14 post-stroke. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Despite the obvious clinical significance of post-stroke angiogenesis in aged subjects, a detailed transcriptomic analysis of post-stroke angiogenesis has not yet been undertaken in an aged experimental model. In this study, by combining stroke transcriptomics with immunohistochemistry in aged rats and post-stroke patients, we sought to identify an age-specific gene expression pattern that may characterize the angiogenic process after stroke. We found that both young and old infarcted rats initiated vigorous angiogenesis. However, the young rats had a higher vascular density by day 14 post-stroke. "New-for-stroke" genes that were linked to the increased vasculature density in young animals included Angpt2, Angptl2, Angptl4, Cib1, Ccr2, Col4a2, Cxcl1, Lef1, Hhex, Lamc1, Nid2, Pcam1, Plod2, Runx3, Scpep1, S100a4, Tgfbi, and Wnt4, which are required for sprouting angiogenesis, reconstruction of the basal lamina (BL), and the resolution phase. The vast majority of genes involved in sprouting angiogenesis (Angpt2, Angptl4, Cib1, Col8a1, Nrp1, Pcam1, Pttg1ip, Rac2, Runx1, Tnp4, Wnt4); reconstruction of a new BL (Col4a2, Lamc1, Plod2); or tube formation and maturation (Angpt1, Gpc3, Igfbp7, Sparc, Tie2, Tnfsf10), had however, a delayed upregulation in the aged rats. The angiogenic response in aged rats was further diminished by the persistent upregulation of "inflammatory" genes (Cxcl12, Mmp8, Mmp12, Mmp14, Mpeg1, Tnfrsf1a, Tnfrsf1b) and vigorous expression of genes required for the buildup of the fibrotic scar (Cthrc1, Il6ra, Il13ar1, Il18, Mmp2, Rassf4, Tgfb1, Tgfbr2, Timp1). Beyond this barrier, angiogenesis in the aged brains was similar to that in young brains. We also found that the aged human brain is capable of mounting a vigorous angiogenic response after stroke, which most likely reflects the remaining brain plasticity of the aged brain.
    Full-text · Article · Mar 2014 · Frontiers in Aging Neuroscience
Show more