adrenomedullin and Glioma

Gliomas, defined as tumors of glial origin, represent between 2-5 percent of all adult cancer and comprise the majority of primary brain tumors. Infiltrating gliomas, with an incidence of more than 40 percent of brain tumors, are the most common and destructive primary brain tumors for which conventional therapies have not significantly improved patient outcome. In fact, patients suffering from malignant gliomas have poor prognoses and the majority have local tumor recurrence after treatment. Tumor growth and spread of tumor cells depend basically upon angiogenesis and on functional abnormalities of tumor cells in the control of apoptosis, as they are paradigmatic for their intrinsic resistance to multiple pro-apoptotic stimuli. Therefore, promising strategies for treatment of brain cancer would be directed to appropriate neutralization of angiogenesis and sensibilization of cancer cells to undergo apoptosis. However, despite advances in this field, high-grade gliomas remain incurable with survival often measured in months. Therefore there is a need to discover new and more potent cocktails of drugs to target the key molecular pathways involved in glioma angiogenesis and apoptosis. This review deals with the effects of two groups of molecules closely linked to neural tissue, which have been implicated in brain cancer: nitric oxide and peptides of the adrenomedullin family. These molecules exert vasodilatory and proangiogenic actions. Adrenomedullin also has antiapoptotic functions at appropriate concentrations. The inhibition of these functions, in the case of cancer, may provide new pharmacological strategies in the treatment of this disease.

Topics: Adrenomedullin; Animals; Antineoplastic Agents; Brain Neoplasms; Enzyme Inhibitors; Glioma; Humans; Nitric Oxide; Nitric Oxide Donors; Treatment Outcome

Gliomas account for about 80% of all malignant brain and other central nervous system (CNS) tumors. Temozolomide (TMZ) resistance represents a major treatment hurdle. Adrenomedullin (ADM) has been reported to induce glioblastoma cell growth.. Cell viability was measured using the CCK-8 assay. The apoptosis analysis was performed using the Annexin V-FITC Apoptosis Detection Kit. The mitochondrial membrane potential was determined by JC-1 staining. A nude mouse tumor assay was used to detect tumor formation. Hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining were performed in tissue sections. Activation of Akt and Erk and expression of apoptosis-related proteins were determined by immunoblotting.. ADM expression has been found upregulated in TMZ -resistant glioma samples based on bioinformatics and experimental analyses. Knocking down ADM in glioma cells enhanced the suppressive effects of TMZ on glioma cell viability, promotive effects on cell apoptosis, and inhibitory effects on mitochondrial membrane potential. Moreover, ADM knockdown also enhanced TMZ effects on Bax/Bcl-2, Akt phosphorylation, and Erk1/2 phosphorylation. Bioinformatics and experimental investigation indicated that miR-1297 directly targeted ADM and inhibited ADM expression. miR-1297 overexpression exerted similar effects to ADM knockdown on TMZ-treated glioma cells. More importantly, under TMZ treatment, inhibition of miR-1297 attenuated TMZ treatment on glioma cells; ADM knockdown partially attenuated the effects of miR-1297 inhibition on TMZ-treated glioma cells.. miR-1297 sensitizes glioma cells to TMZ treatment through targeting ADM. The Bax/Bcl-2, Akt, and Erk1/2 signaling pathways, as well as mitochondrial functions might be involved.

Topics: Adrenomedullin; Animals; Antineoplastic Agents, Alkylating; Apoptosis; bcl-2-Associated X Protein; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Eosine Yellowish-(YS); Glioma; Hematoxylin; Mice; MicroRNAs; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Temozolomide

Vascular endothelial growth factor (VEGF) is a potent mediator of vascular permeability. VEGF inhibition reduces edema and tumor burden in some patients with malignant glioma, whereas others show no response. The role of VEGF expression in edema production and the relationship to survival is not well understood.. Using DNA microarray analysis, we examined VEGF and related gene expression in 71 newly diagnosed malignant gliomas and analyzed the relationship to edema and survival.. VEGF expression was predictive of survival in tumors with little or no edema [Cox proportional hazard model, 6.88; 95% confidence interval (95% CI), 2.61-18.1; P<0.0001], but not in tumors with extensive edema. The expression of several proangiogenic genes, including adrenomedullin (correlation coefficient, 0.80), hypoxia-inducible factor-1A (0.51), and angiopoietin-2 (0.44), was correlated with VEGF expression (all with P<0.0001), whereas that of several antiangiogenic genes was inversely correlated. The expression of six genes was increased greater than 3-fold in edematous versus nonedematous tumors in the absence of increased VEGF expression. The most increased, neuronal pentraxin 2 (NPTX2, 7-fold change), was predictive of survival in tumors with the highest levels of edema, in contrast to VEGF (hazard ratio, 2.73; 95% CI, 1.49-5.02; P=0.049). NPTX2 was tightly correlated with expression of the water channel aquaporin-3 (0.74, P<0.0001). These results suggest that there are both VEGF-dependent and VEGF-independent pathways of edema production in gliomas and may explain why edema is not reduced in some patients following anti-VEGF treatment.

Topics: Adrenomedullin; Angiopoietin-2; Aquaporin 3; Brain Edema; Brain Neoplasms; C-Reactive Protein; Gene Expression; Glioma; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Nerve Tissue Proteins; Oligonucleotide Array Sequence Analysis; Prognosis; Survival; Vascular Endothelial Growth Factor A

Adrenomedullin is a vasoactive peptide that is upregulated in higher-grade gliomas and promotes tumor cell proliferation. Since reduced activity of the anti-oncogene PTEN seems to also correlate with higher tumor grade, this suggests an inverse association between PTEN activity and adrenomedullin expression. PC12 pheochromocytoma and human U251 glioma cell lines were stably transfected with human PTEN or control plasmid. Adrenomedullin expression was analyzed using quantitative PCR and Western blotting. A cell proliferation assay was used to assess adrenomedullin effects on U251 cells overexpressing PTEN. PC12 and U251 cells overexpressing PTEN had 17- and 8-fold decreases in adrenomedullin mRNA levels, respectively, compared to control cells. Cellular and secreted adrenomedullin peptide was similarly reduced. Addition of adrenomedullin to medium of controlled cells induced proliferation, as described previously, but U251 cells overexpressing PTEN did not respond to exogenous adrenomedullin. Further exploration revealed that PTEN also inhibits expression of the gliomas receptor for adrenomedullin, which accounts for this effect. These data were all replicated with an inducible PTEN construct confirming that these effects are not exclusively secondary to chronic overexpression. Given the profound effects of adrenomedullin on tumor cells, this is a novel and previously unidentified mechanism by which alterations in PTEN levels or function may influence tumor growth.

Topics: Adrenomedullin; Animals; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Down-Regulation; Glioma; Humans; PC12 Cells; Peptides; PTEN Phosphohydrolase; Rats; Receptors, Adrenomedullin; Receptors, Peptide; Transfection

Presently, there is no effective treatment for glioblastoma, the most malignant and common brain tumor. Growth factors are potential targets for therapeutic strategies because they are essential for tumor growth and progression. Peptidylglycine alpha-amidating monooxygenase is the enzyme producing alpha-amidated bioactive peptides from their inactive glycine-extended precursors. The high expression of peptidylglycine alpha-amidating monooxygenase mRNA in glioblastoma and glioma cell lines points to the involvement of alpha-amidated peptides in tumorigenic growth processes in the brain. After screening of amidated peptides, it was found that human glioblastoma cell lines express high levels of adrenomedullin (AM) mRNA, and that immunoreactive AM is released into the culture medium. AM is a multifunctional regulatory peptide with mitogenic and angiogenic capabilities among others. Real-time quantitative reverse transcriptase-polymerase chain reaction analysis showed that AM mRNA was correlated to the tumor type and grade, with high expression in all glioblastomas analyzed, whereas a low expression was found in anaplastic astrocytomas and barely detectable levels in low-grade astrocytomas and oligodendrogliomas. In the present study we also demonstrate the presence of mRNA encoding the putative AM receptors, calcitonin receptor-like receptor/receptor activity-modifying protein-2 and -3 (CRLR/RAMP2; CRLR/RAMP3) in both glioma tissues and glioblastoma cell lines and further show that exogenously added AM can stimulate the growth of these glioblastoma cells in vitro. These findings suggest that AM may function as an autocrine growth factor for glioblastoma cells. One way to test the autocrine hypothesis is to interrupt the function of the endogenously produced AM. Herein, we demonstrate that a polyclonal antibody specific to AM, blocks the binding of the hormone to its cellular receptors and decreases by 33% (P < 0.001) the growth of U87 glioblastoma cells in vitro. Intratumoral administration of the anti-AM antibody resulted in a 70% (P < 0.001) reduction in subcutaneous U87 xenograft weight 21 days after treatment. Furthermore, the density of vessels was decreased in the antibody-treated tumors. These findings support that AM may function as a potent autocrine/paracrine growth factor for human glioblastomas and demonstrate that inhibition of the action of AM (produced by tumor cells) may suppress tumor growth in vivo.

Topics: Adrenomedullin; Animals; Antibodies; Cell Division; Glioblastoma; Glioma; Humans; Immunohistochemistry; Male; Mice; Mice, Inbred Strains; Mixed Function Oxygenases; Multienzyme Complexes; Neoplasm Transplantation; Peptide Fragments; Peptides; RNA, Messenger; Transplantation, Heterologous; Tumor Cells, Cultured

The actions and the presence of adrenomedullin (AM) were investigated in cultured human oligodendroglial cell line KG1C. AM and AM mRNA were detected in KG1C cells by immunohistochemistry and RT-PCR. mRNAs for calcitonin receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMPs) 1, 2 and 3 but not for calcitonin receptors were detected in the cells, while mRNAs for CRLR, calcitonin receptors and all RAMPs were detected in the human cerebellum. Application of AM resulted in time- and concentration-dependent increases in the cAMP level of KG1C cells. Calcitonin gene-related peptide (CGRP) and amylin, peptides structurally related to AM, also increased cAMP. The potencies for the cAMP production of the three peptides were CGRP > or =AM >> amylin with EC(50) of 8, 18, 90 nM, respectively. The responses induced by AM were strongly inhibited by the CGRP(1) receptor antagonist human CGRP(8-37), and inhibited also by the AM receptor antagonist human AM(22-52). In contrast, the responses induced by CGRP or amylin were inhibited only by CGRP(8-37) and not by AM(22-52). The responses induced by all three peptides were unaffected by the amylin receptor antagonist human amylin(8-37). The CGRP(2) receptor agonist human [Cys(Acm)(2,7)]CGRP significantly increased the cAMP level but the increase was smaller than that caused by CGRP. This increase in cAMP was unaffected by CGRP(8-37), AM(22-52) or by amylin(8-37). These results suggest that in KG1C cells, AM increases cAMP through AM and CGRP(1) receptors, whereas CGRP does so through CGRP(1) and CGRP(2) receptors, and amylin exerts its effects through CGRP(1) receptors. Collectively, these findings imply that AM released from oligodendroglial cells may play a role in the regulation of oligodendrocytes via autocrine/paracrine through AM receptors and CGRP(1) receptors.

Topics: Adrenal Medulla; Adrenomedullin; Amyloid; Animals; Autocrine Communication; Brain Neoplasms; Calcitonin Gene-Related Peptide; Calcitonin Receptor-Like Protein; Cattle; Cells, Cultured; Cyclic AMP; Gene Expression Regulation; Glioma; Humans; Intracellular Signaling Peptides and Proteins; Islet Amyloid Polypeptide; Membrane Proteins; Nerve Tissue Proteins; Oligodendroglia; Paracrine Communication; Peptide Fragments; Peptides; Receptor Activity-Modifying Proteins; Receptors, Calcitonin; Receptors, Calcitonin Gene-Related Peptide; Receptors, Islet Amyloid Polypeptide; Receptors, Peptide; Reverse Transcriptase Polymerase Chain Reaction; Second Messenger Systems; Tumor Cells, Cultured

Characterization of immunoreactive adrenomedullin (AM) secreted from cultured human vascular smooth muscle cells and 7 other cells indicates that AM is synthesized and secreted from all cultured cells we surveyed. The secretion rate of AM measured ranges from 0.001-6.83 fmol/10(5) cells/h, and endothelial cells, vascular smooth muscle cells and fibroblasts generally secrete AM at high rates. Based on the results of regulation of AM secretion from vascular wall cells, fibroblasts, macrophages and other cells measured in this and previous studies, AM secretion is found to be generally stimulated by inflammatory cytokines, lipopolysaccharide (LPS) and hormones. Especially, vascular smooth muscle cells and fibroblasts elicited uniform and strong stimulatory responses of AM secretion to tumor necrosis factor (TNF), interleukin-1 (IL-1), LPS and glucocorticoid, but endothelial cells did not elicit such prominent responses. AM secretion of monocyte-macrophage was mainly regulated by the degree of differentiation into macrophage and activation by LPS and inflammatory cytokines including interferon-gamma. The other examined cells showed weaker responses to LPS and IL-1. Although cultured cells may have been transformed as compared with those in the tissue, these data indicate that AM is widely synthesized and secreted from most of the cells in the body and functions as a local factor regulating inflammation and related reactions in addition to as a potent vasodilator. The responses of AM secretion to LPS and inflammatory cytokines suggest that fibroblasts, vascular smooth muscle cells and macrophage are the major sources of AM in the septic shock.

Topics: Adrenomedullin; Analysis of Variance; Animals; Cattle; Cells, Cultured; Endothelium, Vascular; Fibroblasts; Glioblastoma; Glioma; Humans; Macrophages; Mice; Monocytes; Muscle, Smooth, Vascular; PC12 Cells; Peptides; Rats; Receptors, Calcitonin Gene-Related Peptide

The effects of adrenomedullin (ADM) on C6 glioma cells were investigated. [125I]ADM bound with high affinity (Kd = 24 nM) to a single class of sites (Bmax = 36,000/cell) in C6 cells. Specific [125I]ADM binding was inhibited with high affinity by ADM (IC50 value of 10 nM) but not ADM(22-52) or pro-adrenomedullin N-terminal 20 peptide (PAMP). By RT-PCR, ADM receptors were detected in C6 cells. ADM elevated cAMP (ED50 value of 10 nM) whereas PAMP and ADM(22-52) did not. ADM stimulated transiently c-fos mRNA in a concentration-dependent manner. Monoclonal antibody G6, which neutralizes ADM, significantly inhibited C6 proliferation and decreased the ability of ADM to elevate c-fos mRNA. These data suggest that ADM is a regulatory peptide of C6 cells.

Topics: Adrenomedullin; Animals; Antibodies, Monoclonal; Cell Division; Cyclic AMP; Glioma; Membrane Proteins; Peptides; Polymerase Chain Reaction; Protein Binding; Proto-Oncogene Proteins c-fos; Rats; Receptors, Adrenomedullin; Receptors, Peptide; RNA, Messenger; RNA, Neoplasm; Tumor Cells, Cultured