Expression of insulin-like growth factors I and II and their receptor mRNAs in primary human astrocytomas and meningiomas;in vivo studies usingin situ hybridization and immunocytochemistry

Domestic Animal Models of Central Nervous System Tumors: Focus on Meningiomas

Intracranial primary tumors (IPTs) are aggressive forms of malignancies that cause high mortality in both humans and domestic animals. Meningiomas are frequent adult IPTs in humans, dogs, and cats, and both benign and malignant forms cause a decrease in life quality and survival. Surgery is the primary therapeutic approach to treat meningiomas, but, in many cases, it is not resolutive. The chemotherapy and targeted therapy used to treat meningiomas also display low efficacy and many side effects. Therefore, it is essential to find novel pharmacological approaches to increase the spectrum of therapeutic options for meningiomas. This review analyzes the similarities between human and domestic animal (dogs and cats) meningiomas by evaluating the molecular and histological characteristics, diagnosis criteria, and treatment options and highlighting possible research areas to identify novel targets and pharmacological approaches, which are useful for the diagnosis and therapy of this neoplasia to be used in human and veterinary medicine.

Insulin Receptor Isoforms and Insulin Growth Factor-like Receptors: Implications in Cell Signaling, Carcinogenesis, and Chemoresistance

This comprehensive review thoroughly explores the intricate involvement of insulin receptor (IR) isoforms and insulin-like growth factor receptors (IGFRs) in the context of the insulin and insulin-like growth factor (IGF) signaling (IIS) pathway. This elaborate system encompasses ligands, receptors, and binding proteins, giving rise to a wide array of functions, including aspects such as carcinogenesis and chemoresistance. Detailed genetic analysis of IR and IGFR structures highlights their distinct isoforms, which arise from alternative splicing and exhibit diverse affinities for ligands. Notably, the overexpression of the IR-A isoform is linked to cancer stemness, tumor development, and resistance to targeted therapies. Similarly, elevated IGFR expression accelerates tumor progression and fosters chemoresistance. The review underscores the intricate interplay between IRs and IGFRs, contributing to resistance against anti-IGFR drugs. Consequently, the dual targeting of both receptors could present a more effective strategy for surmounting chemoresistance. To conclude, this review brings to light the pivotal roles played by IRs and IGFRs in cellular signaling, carcinogenesis, and therapy resistance. By precisely modulating these receptors and their complex signaling pathways, the potential emerges for developing enhanced anti-cancer interventions, ultimately leading to improved patient outcomes.

Diabetes increases the risk of meningioma: A systematic review and meta-analysis of observational studies

BACKGROUND

Increasing epidemiological evidence suggests that diabetes may be associated with meningioma risk, but the evidence supporting this association is still inconclusive. Therefore, we performed a meta-analysis of all eligible observational studies to evaluate the potential association of diabetes with meningioma risk.

METHODS

A comprehensive literature search was performed in the PubMed, Web of Science and Cochrane Library databases up to November 30, 2020. A random-effects model was applied to calculate the pooled effect size (ES) and its 95 % confidence interval (CI).

RESULTS

Eight studies were included in this study. In a random-effects pooled analysis, the results showed that DM (diabetes mellitus) increased the risk of meningioma (ES 1.17, 95 % CI: 1.02-1.35, P = 0.027). In subgroup analyses, DM increased the risk of meningioma in women (ES: 1.19, 95 % CI: 1.02-1.40, P = 0.027) and men (ES: 1.53, 95 % CI: 1.25-1.88, P = 0.000). This effect was not observed in the postmenopausal group (ES: 1.18, 95 % CI: 0.64-2.18, P = 0.597).

CONCLUSION

Our meta-analysis showed that DM increases the risk of meningioma, but the association was only present in some subgroups. This conclusion should be further confirmed.

Increased Incidence of Intracranial Meningiomas in Patients With Acromegaly

BACKGROUND

An increased incidence of various neoplasms has been described in patients with acromegaly, and there is evidence to suggest that growth factors are risk factors for the development of meningiomas.

OBJECTIVE

To study if patients with acromegaly are more at risk for developing intracranial meningiomas.

METHODS

We conducted an observational study on 221 consecutive acromegalic patients recruited between January 1, 2000 and December 31, 2015, and 357 consecutive patients with a nonsomatotropic pituitary adenoma recruited between March 1, 2015 and December 31, 2016, in our institution. Patients underwent a gadolinium-enhanced 3D T1 brain magnetic resonance imaging to look for meningiomas. The proportion of meningiomas was compared between the 2 groups, and the standardized incidence ratio (SIR) was computed from the incidence rates of meningiomas observed in the population of acromegalic patients and compared to that of the general population given by the local registry of central nervous system tumors.

RESULTS

Patients with acromegaly had a significant risk for developing intracranial meningiomas as compared to patients without acromegaly (7.7% vs 2.2%, P = .005, OR = 3.45 [1.46; 8.15]). There was a significant increased incidence of intracranial meningiomas in patients with acromegaly (SIR = 126 [25; 367]) as compared to the general population.

CONCLUSION

Our study suggests strongly that patients with acromegaly are more at risk for developing intracranial meningiomas.

Is insulin-like growth factor-1 involved in Parkinson's disease development?

Parkinson's disease (PD) is a neurodegenerative disorder that results in the death of dopaminergic neurons within the substantia nigra pars compacta and the reduction in dopaminergic control over striatal output neurons, leading to a movement disorder most commonly characterized by akinesia or bradykinesia, rigidity and tremor. Also, PD is less frequently depicted by sensory symptoms (pain and tingling), hyposmia, sleep alterations, depression and anxiety, and abnormal executive and working memory related functions. On the other hand, insulin-like growth factor 1 (IGF-1) is an endocrine, paracrine and autocrine hormone with several functions including tissue growth and development, insulin-like activity, proliferation, pro-survival, anti-aging, antioxidant and neuroprotection, among others. Herein this review tries to summarize all experimental and clinical data to understand the pathophysiology and development of PD, as well as its clear association with IGF-1, supported by several lines of evidence: (1) IGF-1 decreases with age, while aging is the major risk for PD establishment and development; (2) numerous basic and translational data have appointed direct protective and homeostasis IGF-1 roles in all brain cells; (3) estrogens seem to confer women strong protection to PD via IGF-1; and (4) clinical correlations in PD cohorts have confirmed elevated IGF-1 levels at the onset of the disease, suggesting an ongoing compensatory or "fight-to-injury" mechanism.

IGFBP6 controls the expansion of chemoresistant glioblastoma through paracrine IGF2/IGF-1R signaling

BACKGROUND

Glioblastomas (GBMs), the most common and most lethal of the primary brain tumors, are characterized by marked intra-tumor heterogeneity. Several studies have suggested that within these tumors a restricted population of chemoresistant glioma cells is responsible for recurrence. However, the gene expression patterns underlying chemoresistance are largely unknown. Numerous efforts have been made to block IGF-1R signaling pathway in GBM. However, those therapies have been repeatedly unsuccessful. This failure may not only be due to the complexity of IGF receptor signaling, but also due to complex cell-cell interactions in the tumor mass. We hypothesized that differential expression of proteins in the insulin-like growth factor (IGF) system underlie cell-specific differences in the resistance to temozolomide (TMZ) within GBM tumors.

METHODS

Expression of IGF-1R was analyzed in cell lines, patient-derived xenograft cell lines and human biopsies by cell surface proteomics, flow cytometry, immunofluorescence and quantitative real time polymerase chain reaction (qRT-PCR). Using gain-of-function and loss-of-function strategies, we dissected the molecular mechanism responsible for IGF-binding protein 6 (IGFBP6) tumor suppressor functions both in in vitro and in vivo. Site direct mutagenesis was used to study IGFBP6-IGF2 interactions.

RESULTS

We determined that in human glioma tissue, glioma cell lines, and patient-derived xenograft cell lines, treatment with TMZ enhances the expression of IGF1 receptor (IGF-1R) and IGF2 and decreases the expression of IGFBP6, which sequesters IGF2. Using chemoresistant and chemosensitive wild-type and transgenic glioma cells, we further found that a paracrine mechanism driven by IGFBP6 secreted from TMZ-sensitive cells abrogates the proliferation of IGF-1R-expressing TMZ-resistant cells in vitro and in vivo. In mice bearing intracranial human glioma xenografts, overexpression of IGFBP6 in TMZ-resistant cells increased survival. Finally, elevated expression of IGF-1R and IGF2 in gliomas associated with poor patient survival and tumor expression levels of IGFBP6 directly correlated with overall survival time in patients with GBM.

CONCLUSIONS

Our findings support the view that proliferation of chemoresistant tumor cells is controlled within the tumor mass by IGFBP6-producing tumor cells; however, TMZ treatment eliminates this population and enriches the TMZ-resistant cell populationleading to accelerated growth of the entire tumor mass.

Type 1 IGF Receptor Localization in Paediatric Gliomas: Significant Association with WHO Grading and Clinical Outcome

Nuclear localization of insulin-like growth factor receptor type 1 (IGF-1R) has been described as adverse prognostic factor in some cancers. We studied the expression and localization of IGF-1R in paediatric patients with gliomas, as well as its association with World Health Organization (WHO) grading and survival. We conducted a single cohort, prospective study of paediatric patients with gliomas. Samples were taken at the time of the initial surgery; IGF-1R expression and localization were characterized by immunohistochemistry (IHC), subcellular fractionation and western blotting. Tumours (47/53) showed positive staining for IGF-1R by IHC. IGF-1R nuclear labelling was observed in 10/47 cases. IGF-1R staining was mostly non-nuclear in low-grade tumours, while IGF-1R nuclear labelling was predominant in high-grade gliomas (p = 0.0001). Survival was significantly longer in patients with gliomas having non-nuclear IGF-1R localization than in patients with nuclear IGF-1R tumours (p = 0.016). In gliomas, IGF-1R nuclear localization was significantly associated with both high-grade tumours and increased risk of death. Based on a prospective design, we provide evidence of a potential usefulness of intracellular localization of IGF-1R as prognostic factor in paediatric patients with gliomas.

IGF-IR: a new prognostic biomarker for human glioblastoma

Background:

Glioblastomas (GBMs) are the most common malignant primary brain tumours in adults and are refractory to conventional therapy, including surgical resection, radiotherapy and chemotherapy. The insulin-like growth factor (IGF) system is a complex network that includes ligands (IGFI and IGFII), receptors (IGF-IR and IGF-IIR) and high-affinity binding proteins (IGFBP-1 to IGFBP-6). Many studies have reported a role for the IGF system in the regulation of tumour cell biology. However, the role of this system remains unclear in GBMs.

Methods:

We investigate the prognostic value of both the IGF ligands' and receptors' expression in a cohort of human GBMs. Tissue microarray and image analysis were conducted to quantitatively analyse the immunohistochemical expression of these proteins in 218 human GBMs.

Results:

Both IGF-IR and IGF-IIR were overexpressed in GBMs compared with normal brain (P<10⁻⁴ and P=0.002, respectively). Moreover, with regard to standard clinical factors, IGF-IR positivity was identified as an independent prognostic factor associated with shorter survival (P=0.016) and was associated with a less favourable response to temozolomide.

Conclusions:

This study suggests that IGF-IR could be an interesting target for GBM therapy.

Inhibition of intracerebral glioblastoma growth by targeting the insulin-like growth factor 1 receptor involves different context-dependent mechanisms

BACKGROUND

Signaling by insulin-like growth factor 1 receptor (IGF-1R) can contribute to the formation and progression of many diverse tumor types, including glioblastoma. We investigated the effect of the IGF-1R blocking antibody IMC-A12 on glioblastoma growth in different in vivo models.

METHODS

U87 cells were chosen to establish rapidly growing, angiogenesis-dependent tumors in the brains of nude mice, and the GS-12 cell line was used to generate highly invasive tumors. IMC-A12 was administered using convection-enhanced local delivery. Tumor parameters were quantified histologically, and the functional relevance of IGF-1R activation was analyzed in vitro.

RESULTS

IMC-A12 treatment inhibited the growth of U87 and GS-12 tumors by 75% and 50%, respectively. In GS-12 tumors, the invasive tumor extension and proliferation rate were significantly reduced by IMC-A12 treatment, while apoptosis was increased. In IMC-A12-treated U87 tumors, intratumoral vascularization was markedly decreased, and tumor cell proliferation was moderately reduced. Flow cytometry showed that <2% of U87 cells but >85% of GS-12 cells expressed IGF-1R. Activation of IGF-1R by IGF-1 and IGF-2 in GS-12 cells was blocked by IMC-A12. Both ligands stimulated GS-12 cell proliferation, and IGF-2 also stimulated migration. IMC-A12 inhibited these stimulatory effects and increased apoptosis. In U87 cells, stimulation with either ligand had no functional effect.

CONCLUSIONS

IGF-1R blockade can inhibit glioblastoma growth by different mechanisms, including direct effects on the tumor cells as well as indirect anti-angiogenic effects. Hence, blocking IGF-1R may be useful to target both the highly proliferative, angiogenesis-dependent glioblastoma core component as well as the infiltrative periphery.

An audit of immunohistochemical marker patterns in meningioma

Meningiomas may express a number of potentially growth-promoting receptors including receptors for progesterone, growth hormone and vascular endothelial growth factor (VEGF). These and other receptors are potential targets for chemotherapy. We have prospectively studied a panel of markers as a routine in order to obtain data of individual expression of markers that may provide targets for anti-receptor treatment. One hundred and seventy-five consecutive patients operated on for meningiomas between 2005 and 2008 were prospectively analysed with antibodies against receptors for growth hormone, insulin-like growth factor 1 (IGF-1), androgen receptors, progesterone receptors (PR) and antibodies against CD34, VEGF, Ki-67 and caspase-3. Expression of IGF-1 receptor (IGF-1r), epidermal growth factor receptor (EGFR) E30 and growth hormone receptor (GHr) was conserved across histological grades and found in 88% to 94% of meningiomas. PR were detected in 87%, but expression decreased in aggressive tumours. Angio-markers such as VEGF and CD34 were detected in 69% and 17% of meningiomas, respectively. Androgen receptors and caspase-3 were uncommon. The analyses of a panel were undertaken as a clinical routine in order to assess its feasibility and to provide data that can be utilised in a clinical setting. Three putative therapeutic receptor targets, IGF-1r, GHr and EGFR E30 were expressed in a large majority of tumours and in contrast to PR maintained expression despite increasing pathological grade of meningioma. Our data also suggest that anti-progesterone therapies and anti-angiogenic therapies could be targeted to subsets of meningioma patients who express PR or have CD34-positive tumours.

A phosphatase-independent gain-of-function mutation in PTEN triggers aberrant cell growth in astrocytes through an autocrine IGF-1 loop

Loss-of-function mutations in the phosphatase PTEN (phosphatase and tensin homolog deleted on chromosome10) contribute to aberrant cell growth in part through upregulation of the mitogenic IGF-1/PI3K/Akt pathway. In turn, this pathway exerts a homeostatic feedback over PTEN. Using mutagenesis analysis to explore a possible impact of this mutual control on astrocyte growth, we found that truncation of the C-terminal region of PTEN (Δ51) associates with a marked increase in NFκB activity, a transcription factor overactivated in astrocyte tumors. Whereas mutations of PTEN are considered to lead to a loss-of-function, PTENΔ51, a truncation that comprises a region frequently mutated in human gliomas, displayed a neomorphic (gain-of-function) activity that was independent of its phosphatase activity. This gain-of-function of PTENΔ51 includes stimulation of IGF-1 synthesis through protein kinase A activation of the IGF-1 promoter. Increased IGF-1 originates an autocrine loop that activates Akt and NFκB. Constitutive activation of NFκB in PTENΔ51-expressing astrocytes leads to aberrant cell growth; astrocytes expressing this mutant PTEN generate colonies in vitro and tumors in vivo. Mutations converting a tumor suppressor such as PTEN into a tumor promoter through a gain-of-function involving IGF-1 production may further our understanding of the role played by this growth factor in glioma growth and help us define druggable targets for personalized therapy.

Gene therapy for high-grade glioma

High-grade glioma is the most frequently occurring primary brain tumor and is associated with a poor prognosis. Current treatment regimens have had only a modest effect on the progressive course despite recent advances in surgery, radiotherapy, and chemotherapy. Gene therapy for brain tumors represents a novel and promising therapeutic approach and has been investigated clinically for the last two decades. The strategies of gene therapy include suicide gene therapy, immune gene therapy, oncolytic viral therapy, tumor suppressor gene therapy, and antisense therapy. Here, we review gene therapy approaches considering the clinical results, limitations, and future directions.

Immunobiology of malignant gliomas

The immune system of patients with malignant gliomas is profoundly suppressed. The suppression involves both the cellular and humoral immunity and it is mainly attributable to selective depletion and malfunction of helper T cells. Malignant glioma cells express potent immunosuppressive factors such as transforming growth factor-beta(2), inteleukin-10 and prostaglandin E(2). Malignant glioma cells also produce chemoattractants and immunostimulatory cytokines which may activate the immune cells. However, the production of these stimulatory cytokines is not self-destructive to glioma cells because of the immunosuppression. Rather, the tumour cells use them to gain a growth advantage. Indeed the cytokines may act as a growth stimulator of the tumour cells themselves (autocrine mechanism), they may act as angiogenic factors to endothelial cells (paracrine mechanism) or induce the attracted immune cells to secrete angiogenic factors. Some cytokines produced by malignant glioma cells are known to be growth inhibitory to normal astrocytes. Recent studies on tumour suppressor genes suggest a close link between the aberrant genes and the immunobiologic features of malignant glioma cells.

Potent inhibition of angiogenesis by the IGF-1 receptor-targeting antibody SCH717454 is reversed by IGF-2

Previously, we reported that a predominant action of a type-1 insulin-like growth factor receptor (IGF-1R)-targeted antibody was through inhibiting tumor-derived VEGF, and indirectly, angiogenesis. Here, we examined the direct antiangiogenic activity of the IGF-1R-targeted antibody SCH717454 that inhibits ligand-receptor binding and the mechanism by which tumors circumvent its antiangiogenic activity. Inhibition of ligand-stimulated activation of IGF-1R, insulin receptor (IN-R), or downstream signaling [phosphorylation of Akt (Ser473)] was determined by receptor-specific immunoprecipitation and immunoblotting. Inhibition of angiogenesis was determined by proliferation and tube formation using human umbilical vein endothelial cells (HUVEC) in vitro and in Matrigel plugs implanted in mice. SCH717454 blocked IGF-1-stimulated but not IGF-2-stimulated phosphorylation of Akt in sarcoma cells. Immunoprecipitation using anti-IGF-1R and anti-IN-R antibodies revealed that SCH717454 equally blocked IGF-1-stimulated and IGF-2-stimulated IGF-1R phosphorylation, but not IGF-2-stimulated phosphorylation of IN-R. SCH717454 completely blocked VEGF-stimulated proliferation and tube formation of HUVECs, but exogenous IGF-2 and insulin circumvented these inhibitory effects. Coculture of HUVECs with IGF-2-secreting tumor cells completely abrogated SCH717454 inhibition of VEGF-stimulated HUVEC tube formation. In mice, SCH717454 inhibited angiogenesis in VEGF-infused Matrigel plugs, but had no inhibitory activity when plugs contained both VEGF + IGF-2. These results reveal for the first time, a role for IGF-1R signaling in VEGF-mediated angiogenesis in vitro and indicate direct antiangiogenic activity of SCH717454. Both in vitro and in vivo IGF-2 circumvented these effects through IN-R signaling. Many childhood cancers secrete IGF-2, suggesting that tumor-derived IGF-2 in the microenvironment maintains angiogenesis in the presence of IGF-1R-targeted antibodies allowing tumor progression.

Initial testing (stage 1) of the IGF-1 receptor inhibitor BMS-754807 by the pediatric preclinical testing program

BACKGROUND

BMS-754807 is a small molecule ATP-competitive inhibitor of the type-1 insulin-like growth factor receptor currently in phase 1 clinical trials.

PROCEDURES

BMS-754807 was tested against the Pediatric Preclinical Testing Program (PPTP) in vitro panel at concentrations ranging from 1.0 nM to 10 µM and was tested against the PPTP in vivo panels at a dose of 25 mg/kg administered orally BID for 6 days, repeated for 6 weeks.

RESULTS

In vitro BMS-754807 showed a median EC(50) value of 0.62 µM against the PPTP cell lines. The median EC(50) for the four Ewing sarcoma cell lines was less than that for the remaining PPTP cell lines (0.19 µM vs. 0.78 µM, P = 0.0470). In vivo BMS-754807 induced significant differences in EFS distribution compared to controls in 18 of 32 evaluable solid tumor xenografts (56%) tested, but in none of the ALL xenografts studied. Criteria for intermediate activity for the time to event activity measure (EFS T/C > 2) were met in 7 of 27 solid tumor xenografts evaluable for this measure. The best response was PD2 (progressive disease with growth delay), which was observed in 18 of 32 solid tumor xenografts. PD2 responses were most commonly observed in the rhabdomyosarcoma, neuroblastoma, osteosarcoma, Ewing sarcoma, and Wilms tumor panels.

CONCLUSIONS

BMS-754807 activity in vitro is consistent with a specific IGF-1R effect that has half-maximal response in the 0.1 µM range and that is observed in a minority of the PPTP cell lines. In vivo intermediate activity was most commonly observed in the neuroblastoma and rhabdomyosarcoma panels.

Helianthin induces antiproliferative effect on human glioblastoma cells in vitro

A major focus of brain cancer research today is to translate understanding of glioma biology into advances in treatment, by exploring the potential of target therapy. Here we investigated the ability of three compounds belonging to the chemical class of azo dyes (methyl red, methyl yellow, and helianthin) to inhibit glioblastoma (GB) cell growth in vitro. Our results showed that helianthin induced cytotoxicity in two GB cell cultures, cell lines 18 and 38, whereas methyl red and methyl yellow were not cytotoxic. The effect of helianthin on EGFR, IGF-1R, and their common intracellular signaling via PI3-K and ERK1/2 was also analyzed. Treatment with helianthin down-regulated EGFR and IGF-1R activity in both cell lines. Helianthin treatment blocked ERK1/2 phosphorylation without affecting PI3K activity in cell line 18 and reduced both PI3K and ERK1/2 in GB 38 cell line. The cell death was accompanied by degradation of PARP without affecting BCL2 expression in both GB cell cultures. Because of the genetic heterogeneity of malignant gliomas, we tested the effect of helianthin on other two primary GB lines (11 and 15) and two early-passage GB cultures (BT1GB and BT2GB), to assess the general nature of the anti-tumor effect of the drug in GB cells. We found that helianthin treatment induced cell death in all the GB cell cultures analyzed. To our knowledge, this is the first report indicating that helianthin can reduce GB cell growth.

Co-graft of allogeneic immune regulatory neural stem cells (NPC) and pancreatic islets mediates tolerance, while inducing NPC-derived tumors in mice

BACKGROUND

Data available on the immunomodulatory properties of neural stem/precursor cells (NPC) support their possible use as modulators for immune-mediated process. The aim of this study was to define whether NPC administered in combination with pancreatic islets prevents rejection in a fully mismatched allograft model.

METHODOLOGY/PRINCIPAL FINDING

Diabetic Balb/c mice were co-transplanted under the kidney capsule with pancreatic islets and GFP(+) NPC from fully mismatched C57BL/6 mice. The following 4 groups of recipients were used: mice receiving islets alone; mice receiving islets alone and treated with standard immunosuppression (IL-2Ralpha chain mAbs + FK506 + Rapamycin); mice receiving a mixed islet/NPC graft under the same kidney capsule (Co-NPC-Tx); mice receiving the islet graft under the left kidney capsule and the NPC graft under the right kidney capsule (NPC-Tx). Our results demonstrate that only the co-transplantation and co-localization of NPC and islets (Co-NPC-Tx) induce stable long-term graft function in the absence of immunosuppression. This condition is associated with an expansion of CD4(+)CD25(+)FoxP3(+) T regulatory cells in the spleen. Unfortunately, stable graft function was accompanied by constant and reproducible development of NPC-derived cancer mainly sustained by insulin secretion.

CONCLUSION

These data demonstrate that the use of NPC in combination with islets prevents graft rejection in a fully mismatched model. However, the development of NPC-derived cancer raises serious doubts about the safety of using adult stem cells in combination with insulin-producing cells outside the original microenvironment.

The insulin-like growth factor-1 receptor-targeting antibody, CP-751,871, suppresses tumor-derived VEGF and synergizes with rapamycin in models of childhood sarcoma

Signaling through the type 1 insulin-like growth factor receptor (IGF-1R) occurs in many human cancers, including childhood sarcomas. As a consequence, targeting the IGF-1R has become a focus for cancer drug development. We examined the antitumor activity of CP-751,871, a human antibody that blocks IGF-1R ligand binding, alone and in combination with rapamycin against sarcoma cell lines in vitro and xenograft models in vivo. In Ewing sarcoma (EWS) cell lines, CP751,871 inhibited growth poorly (<50%), but prevented rapamycin-induced hyperphosphorylation of AKT(Ser473) and induced greater than additive apoptosis. Rapamycin treatment also increased secretion of IGF-1 resulting in phosphorylation of IGF-1R (Tyr1131) that was blocked by CP751,871. In vivo CP-751,871, rapamycin, or the combination were evaluated against EWS, osteosarcoma, and rhabdomyosarcoma xenografts. CP751871 induced significant growth inhibition [EFS(T/C) >2] in four models. Rapamycin induced significant growth inhibition [EFS(T/C) >2] in nine models. Although neither agent given alone caused tumor regressions, in combination, these agents had greater than additive activity against 5 of 13 xenografts and induced complete remissions in one model each of rhabdomyosarcoma and EWS, and in three of four osteosarcoma models. CP751,871 caused complete IGF-1R down-regulation, suppression of AKT phosphorylation, and dramatically suppressed tumor-derived vascular endothelial growth factor (VEGF) in some sarcoma xenografts. Rapamycin treatment did not markedly suppress VEGF in tumors and synergized only in tumor lines where VEGF was dramatically inhibited by CP751,871. These data suggest a model in which blockade of IGF-1R suppresses tumor-derived VEGF to a level where rapamycin can effectively suppress the response in vascular endothelial cells.

YY1 Over-expression in human brain gliomas and meningiomas correlates with TGF-beta1, IGF-1 and FGF-2 mRNA levels

In this study we examined by QRT-PCR the mRNA expression of TGF-beta 1, IGF-1, EGF, FGF-2 and YY1 in human brain tumors. Our findings introduce YY1, for the first time, as a novel gene implicated in brain gliomatogenesis and meningioma establishment. We present a positive correlation between the autocrine expression of YY1 and TGF-beta 1, IGF-1 and FGF-2, known to be involved in the progression of gliomas and meningiomas. We suggest that mRNA profiling of the above genes in the early stages of disease development could be useful for prognostic purposes, and these genes can be considered as potential targets for therapeutic approaches against brain tumors.

Matrix metalloproteinase-9 interplays with the IGFBP2-IGFII complex to promote cell growth and motility in astrocytomas

Insulin-like growth factor II (IGFII) acts as a potent mitogen for several tumor types and has been reported to positively influence astrocytoma cell growth and motility. In the central nervous system, IGFII bioavailability is mainly modulated by insulin-like growth factor binding protein 2 (IGFBP2), which sequestrates IGFII and therefore prevents its interaction with the type-1 IGF receptor (IGF-IR). Proteolysis of IGFBP2 is the predominant mechanism recognized to reduce the binding affinity of IGFBP2 for IGFII, thus favoring dissociation of IGFII from the IGFBP2-IGFII complex. It is known that certain proteases involved in astrocytoma malignancy, such as matrix metalloproteinase-7 (MMP-7), plasmin, and cathepsin D, are able to proteolyze IGFBP2 in vitro. The present study aims to investigate whether other proteases expressed by astrocytomas, specifically MMP-2, MMP-9, and membrane-type 1 matrix metalloprotease (MT1-MMP), are able to proteolyze the IGFBP2-IGFII complex. Our results show the following: (i) MMP-9 proteolyzes the IGFBP2-IGFII complex in vitro, while MMP-2 and MT1-MMP do not; (ii) this MMP-9-induced IGFBP2-IGFII complex proteolysis releases free IGFII, which contributes to enhance the motility and the growth of LN229 astrocytoma cells. Furthermore, this study also highlights that the formation of the IGFBP2-IGFII complex inhibits IGFBP2's cell motility promoting effect by reducing the pool of free IGFBP2. In conclusion, MMP-9-induced IGFBP2 proteolysis may be regarded as an important post-translational event involved in astrocytoma aggressiveness. These new findings support drug targeting of MMP-9 as an interesting approach in the treatment of astrocytoma.

Growth factor receptors signaling in glioblastoma cells: therapeutic implications

In this study, we investigated the protein expression of platelet-derived growth factor receptor (PDGFR), insulin like growth factor-1 receptor (IGF-1R), phosphatidylinositol 3-kinase (PI3-K) and extracellular signal-regulated kinase (ERK1/2) in five primary glioblastoma (GB), with a view to their possible use as therapeutic targets. Our results demonstrated that appreciable levels of these proteins could be detected in the analysed GB cell lines, except for a low level of PDGFR and ERK1/2 expression in one GB cell line. The small molecule inhibitors towards IGF-1R, PDGFR, PI3-K and ERK1/2 respectively, have only modest or no anti-tumour activity on GB cells and therefore their combination with other therapy modalities was analysed. The interaction between small inhibitors and radiation was mostly additive or sub-additive; synergistic interaction was found in five of forty analysed combinations. Our results showed that GB cells are in general resistant to treatment and illustrate the difficulties in predicting the treatment response in malignant gliomas.

Crystal structures of the FAK kinase in complex with TAE226 and related bis-anilino pyrimidine inhibitors reveal a helical DFG conformation

Focal Adhesion Kinase (FAK) is a non-receptor tyrosine kinase required for cell migration, proliferation and survival. FAK overexpression has been documented in diverse human cancers and is associated with a poor clinical outcome. Recently, a novel bis-anilino pyrimidine inhibitor, TAE226, was reported to efficiently inhibit FAK signaling, arrest tumor growth and invasion and prolong the life of mice with glioma or ovarian tumor implants. Here we describe the crystal structures of the FAK kinase bound to TAE226 and three related bis-anilino pyrimidine compounds. TAE226 induces a conformation of the N-terminal portion of the kinase activation loop that is only observed in FAK, but is distinct from the conformation in both the active and inactive states of the kinase. This conformation appears to require a glycine immediately N-terminal to the “DFG motif”, which adopts a helical conformation stabilized by interactions with TAE226. The presence of a glycine residue in this position contributes to the specificity of TAE226 and related compounds for FAK. Our work highlights the fact that kinases can access conformational space that is not necessarily utilized for their native catalytic regulation, and that such conformations can explain and be exploited for inhibitor specificity.

IGFBP2 is overexpressed by pediatric malignant astrocytomas and induces the repair enzyme DNA-PK

To identify targets critical to malignant childhood astrocytoma, we compared the expression of receptor tyrosine kinase- associated genes between low-grade and high-grade pediatric astrocytomas. The highest differentially overexpressed gene in high-grade astrocytoma is insulin-like growth factor- binding protein-2 (P = .0006). Immunohistochemistry confirmed overexpression of insulin-like growth factor-binding protein-2 protein (P = .027). Insulin-like growth factor- binding protein-2 stimulation had no effect on astrocytoma cell growth and migration, and minimally inhibited insulin-like growth factor-1-mediated migration, but not insulin-like growth factor-2-mediated migration. However, insulin-like growth factor-binding protein-2 stimulation significantly upregulated the major DNA repair enzyme gene, DNA-PKcs, and induced DNA-dependent protein kinase catalytic subunit protein expression in a time-dependent and dose-dependent manner, whereas insulin-like growth factor-1 had no effect. DNA-PKcs is also highly overexpressed by high-grade astrocytomas. These findings suggest insulin-like growth factor-binding protein-2 plays a role in astrocytoma progression by promoting DNA-damage repair and therapeutic resistance.

Fetal growth and the risk of childhood non-CNS solid tumours in Western Australia

Using population-based linked health data, we investigated whether the risk of certain childhood non-CNS solid tumours (n=186) was associated with intra-uterine growth. The risk of retinoblastoma and rhabdomyosarcoma, but not other tumour types, was positively associated with increased growth, suggesting a possible role of fetal growth factors. Larger studies are needed.

Fetal growth and the risk of childhood CNS tumors and lymphomas in Western Australia

The etiology of childhood cancers is largely unknown, although the early age at diagnosis has led to particular interest in in utero and perinatal factors. Birth weight is the most frequently studied perinatal factor in relation to risk of childhood cancers, and results have been inconsistent. We investigated whether the risk of CNS tumors and lymphomas in children was associated with three measures of the appropriateness of intra-uterine growth: proportion of optimal birth weight (POBW), birth length (POBL) and weight for length (POWFL). A cohort of 576,633 infants born in Western Australia in 1980-2004 were followed from birth to diagnosis of a CNS tumor (n = 183) or lymphoma (n = 84) before age 15, death, or December 31, 2005, and analyzed with Cox regression. Overall, there was little evidence of any association between fetal growth and risk of CNS tumors, although risk of ependymoma/choroid plexus tumors was positively associated with POBL and negatively associated with POWFL. The risk of Hodgkin and Burkitt lymphoma increased with increasing fetal growth among boys only, whereas the increased risk observed with non-Hodgkin lymphoma was only in girls. These associations between fetal growth and disease risk were also observed among children not classified as high birth weight, suggesting that accelerated growth is more important than birth weight per se. Results were similar when cases were compared with their unaffected siblings, suggesting that the increased growth associated with cancer risk was not general to the family. The associations we observed are consistent with causal pathways involving fetal growth factors.

Initial testing (stage 1) of a monoclonal antibody (SCH 717454) against the IGF-1 receptor by the pediatric preclinical testing program

BACKGROUND

SCH 717454 (19D12) is a fully human antibody directed against the insulin-like growth factor 1 receptor (IGF-1R), which is implicated in the growth and metastatic phenotype of a broad range of malignancies. The activity of SCH 717454 was evaluated against the in vitro and in vivo panels of the Pediatric Preclinical Testing Program (PPTP).

PROCEDURES

SCH 717454 was tested against the PPTP in vitro panel at concentrations ranging from 0.01 to 100 nM and was tested against the PPTP in vivo panel at a dose of 0.5 mg per mouse administered twice weekly for 4 weeks via intraperitoneal injection.

RESULTS

SCH 717454 was ineffective at retarding growth of cell lines in the in vitro panel. In vivo, SCH 717454 significantly increased event-free survival in 20 of 35 (57%) solid tumor xenograft models with tumor regressions in one Ewing sarcoma model (complete response) and 2 osteosarcoma models (maintained complete responses). Using the time to event activity measure, SCH 717454 had intermediate (n = 9) or high (n = 1) activity against 31 evaluable solid tumor xenografts, including xenografts from the rhabdoid tumor, Ewing, rhabdomyosarcoma, glioblastoma, neuroblastoma, and osteosarcoma panels. SCH 717454 showed little activity against the 8 xenografts of the acute lymphoblastic leukemia panel.

CONCLUSIONS

SCH 717454 demonstrated broad antitumor activity against the PPTP's in vivo solid tumor panels. Further characterization of the molecular predictors of response and of the activity of combinations of SCH 717454 with other anticancer agents are anticipated.

Inhibition of both focal adhesion kinase and insulin-like growth factor-I receptor kinase suppresses glioma proliferation in vitro and in vivo

Multiple genetic aberrations in human gliomas contribute to their highly infiltrative and rapid growth characteristics. Focal adhesion kinase (FAK) regulates tumor migration and invasion. Insulin-like growth factor-I receptor (IGF-IR), whose expression correlates with tumor grade, is involved in proliferation and survival. We hypothesized that inhibiting the phosphorylation of FAK and IGF-IR by NVP-TAE226 (hereafter called TAE226), a novel dual tyrosine kinase inhibitor of FAK and IGF-IR, would suppress the growth and invasion of glioma cells. In culture, TAE226 inhibited extracellular matrix-induced autophosphorylation of FAK (Tyr(397)). TAE226 also inhibited IGF-I-induced phosphorylation of IGF-IR and activity of its downstream target genes such as MAPK and Akt. TAE226 retarded tumor cell growth as assessed by a cell viability assay and attenuated G(2)-M cell cycle progression associated with a decrease in cyclin B1 and phosphorylated cdc2 (Tyr(15)) protein expression. TAE226 treatment inhibited tumor cell invasion by at least 50% compared with the control in an in vitro Matrigel invasion assay. Interestingly, TAE226 treatment of tumor cells containing wild-type p53 mainly exhibited G(2)-M arrest, whereas tumor cells bearing mutant p53 underwent apoptosis. Induction of apoptosis by TAE226 was substantiated by detection of caspase-3/7 activation and poly(ADP-ribose) polymerase cleavage and by an Annexin V apoptosis assay. More importantly, TAE226 treatment significantly increased the survival rate of animals in an intracranial glioma xenograft model. Collectively, these data show that blocking the signaling pathways of FAK and IGF-IR with TAE226 has the potential to be an efficacious treatment for human gliomas.

Antisense treatment of IGF-IR induces apoptosis and enhances chemosensitivity in central nervous system atypical teratoid/rhabdoid tumours cells

Central nervous system (CNS) atypical teratoid/rhabdoid tumours (AT/RT) are among the paediatric malignant tumours with the worst prognosis and fatal outcome. Insulin-like growth factor I receptor (IGF-IR) protects cancer cells from apoptosis induced by a variety of anticancer drugs and radiation. In the present study, IGF-IR was expressed in 8/8 primary AT/RT as detected by immunohistochemistry. Moreover, we found IGF-I and IGF-II mRNA in BT-16 CNS AT/RT cells and IGF-II mRNA in BT-12 CNS AT/RT cells, and autophosphorylated IGF-IR in both cell lines, indicating the potential presence of an autocrine/paracrine IGF-I/II/IGF-IR loop in CNS AT/RT. IGF-IR antisense oligonucleotide treatment of human CNS AT/RT cells resulted in significant down-regulation of IGF-IR mRNA and protein expression, induction of apoptosis, and chemosensitisation to doxorubicin and cisplatin. These studies provide evidence for the influence of IGF-IR on cellular responses to chemotherapy and raise the possibility that curability of selected CNS AT/RT may be improved by pharmaceutical strategies directed towards the IGF-IR.

Emerging roles of insulin-like growth factor-I in the adult brain

All tissues in the body are under the influence of insulin-like growth factor-I (IGF-I). Together with insulin, IGF-I is a key regulator of cell metabolism and growth. IGF-I also acts in the central nervous system, where it affects many different cell populations. In this brief review, we discuss the many roles of IGF-I in the adult brain, and present the idea that diseases affecting the brain will perturb IGF-I activity, although more refined studies at the molecular and cellular level are needed before we can firmly established this possibility. We also suggest that under normal physiological conditions IGF-I may play a significant role in higher brain functions underlying cognition, and may serve a homeostatic role during brain aging. Among newly emerging issues, the effects of IGF-I on non-neuronal cells within the nervous system and their impact in brain physiology and pathology are becoming very important in understanding the biology of this peptide in the brain.

The role of the IGF system in cancer growth and metastasis: overview and recent insights

IGF-I receptor (IGF-IR) signaling and functions are mediated through the activities of a complex molecular network of positive (e.g., type I IGF) and negative (e.g., the type II IGF receptor, IGF-IIR) effectors. Under normal physiological conditions, the balance between the expression and activities of these molecules is tightly controlled. Changes in this delicate balance (e.g., overexpression of one effector) may trigger a cascade of molecular events that can ultimately lead to malignancy. In recent years, evidence has been mounting that the IGF axis may be involved in human cancer progression and can be targeted for therapeutic intervention. Here we review old and more recent evidence on the role the IGF system in malignancy and highlight experimental and clinical studies that provide novel insights into the complex mechanisms that contribute to its oncogenic potential. Controversies arising from conflicting evidence on the relevance of IGF-IR and its ligands to human cancer are discussed. Our review highlights the importance of viewing the IGF axis as a complex multifactorial system and shows that changes in the expression levels of any one component of the axis, in a given malignancy, should be interpreted with caution and viewed in a wider context that takes into account the expression levels, state of activation, accessibility, and functionality of other interacting components. Because IGF targeting for anticancer therapy is rapidly becoming a clinical reality, an understanding of this complexity is timely because it is likely to have an impact on the design, mode of action, and clinical outcomes of newly developed drugs.

Expression of endothelin 1 and its angiogenic role in meningiomas

Meningiomas are one of the most frequent central nervous system tumours. Although slow-growing at times, they continue to be a cause of morbidity and mortality. The endothelin (ET) family consists of three isoforms: ET-1 is the most abundant one. ET-1 may be involved in meningioma tumourigenesis in concert with other growth factors, in particular with angiogenic agents. We analysed ET-1 expression by immunohistochemistry and its activating system by reverse-transcription-polymerase chain reaction in 56 cases of meningioma. We found an association between high-grade meningiomas and high ET-1 expression levels (p=0.002). Moreover, we evaluated the potential angiogenic role of ET-1, finding an elevated microvessel count in tumours with high ET expression levels (p=0.004). ET-1 may contribute to meningioma growth by inducing formation of new blood vessels. The finding that ET-1 expression positively correlates with vascular endothelial growth factor (VEGF) expression in meningiomas (p=0.03) also supports the hypothesized modulating effect of ET-1 on angiogenesis. Thus, the influence of the ET system on the progression of meningiomas may occur through stimulation of VEGF. The association of ET-1 and meningioma represents a potential area for therapeutic intervention with selective ET inhibitors. Additional clinical studies will be needed before inhibitors can be incorporated in clinical practice.

The effects of antisense AKT2 RNA on the inhibition of malignant glioma cell growth in vitro and in vivo

The oncogenic role of AKT2 in the development of malignant gliomas was examined by using antisense approach. AKT2 expression was significantly inhibited in rat C6 glioma cells transfected with antisense AKT2 cDNA construct (LXSN-AS-AKT2). In addition, the transfected cells proliferated at a lowered level and apoptosis was induced. For in vivo studies, parental C6 cells and C6 cells transfected with LXSN-AS-AKT2 were implanted stereotactically into the right caudate nucleus of SD rats (control C6 group and transfected group). The rats bearing well-established C6 gliomas were treated with LXSN-AS-AKT2 DNA or LXSN (empty vector)-lipofectamine complexes intratumorally (treated group and control treated group). The mean survival of the rats of control C6 group and treated control group was 17.8+/-0.92 days and 17.5+/-1.10 days, respectively. The mean survival of the rats of transfected and treated group was significantly prolonged. MR images revealed distinct cerebral tumor foci in all of the control rats, whereas four rats in transfected group did not develop tumors and the tumor foci in five rats of treated group were regressed and disappeared. The expression of AKT2, PCNA, MMP2/9, and cyclin D were inhibited in the tumors of rats in transfected and treated groups while GFAP expression was increased. These results suggest that AKT pathway may play an important role in the development and progression of gliomas. Anti-AKT approach will open a new perspective for a targeted molecular therapy of malignant gliomas.

Insulin-like growth factor-I decreased etoposide-induced apoptosis in glioma cells by increasing bcl-2 expression and decreasing CPP32 activity

AIMS

In a variety of tumors, the susceptibility of the tumor cells to apoptotic cell death following chemotherapy is a major determinant of therapeutic outcome. Gliomas are resistant to most chemotherapeutic agents, and its mechanism is not known in detail. In an attempt to understand the mechanism of chemo-resistance, we investigated the roles of insulin-like growth factor-I (IGF-I), IGF-I receptors (IGF-IR), and their relationship with the apoptotic response of two glioma cell lines to etoposide, a chemotherapeutic agent for malignant gliomas.

METHODS

Two human glioma cell lines, U-87MG and KNS-42, were used. Etoposide-induced cell growth inhibition was quantified using a modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide), colorimetric assay. Hoechst 33258 staining, DNA fragmentation assay, and western blot were used for the evaluation of apoptosis. ApoAlert caspase assay was used for measuring the activity of caspase-3 (CPP32) and interleukin-1 beta -converting enzyme (ICE) protease. In addition, the effect of IGF-IR antisense was tested in U-87MG and KNS-42 glioma cell lines.

RESULTS

Etoposide inhibited the growth of U-87MG and KNS-42 cells in a concentration-dependent manner. Etoposide increased the expression of wild-type p53, activated CPP32 (but not ICE) activity, and induced apoptosis in these cells. IGF-I prevented etoposide-induced apoptosis by increasing the expression of bcl-2 and decreasing the activity of CPP32. IGF-IR antisense enhanced the apoptotic effect of etoposide.

CONCLUSIONS

IGF-I decreased etoposide-induced apoptosis in glioma cells by increasing the expression of bcl-2 and decreasing the activity of CPP32. The antisense of IGF-IR increased etoposide-induced apoptosis. The anti-apoptotic effect of IGF-I and IGF-IR might be related to the chemo-resistance of glioma to chemotherapeutic agents.

Induction of apoptosis in primary meningioma cultures by fenretinide

Fenretinide, a synthetic retinoid that induces apoptosis in tumor cells in vitro, is being evaluated in clinical trials as a chemotherapeutic agent against several malignancies. Due to its ease of administration, long-term tolerability, and low incidence of long-term side effects, we explored its potential as a therapeutic agent against meningiomas by examining its efficacy in vitro against such cells in primary culture. Cells, cultured from freshly resected benign, atypical, or malignant meningiomas, were exposed to fenretinide (10 mumol/L). Treatment effects were assessed using flow cytometry, Western blot analysis, semiquantitative reverse transcription-PCR for retinoid receptor expression, and changes in insulin-like growth factor-I (IGF-I)-induced proliferation. Fenretinide induced apoptosis in the three grades of meningioma primary cells tested, as shown by the appearance of a sub-G(1) fraction in flow cytometric analysis and by the detection of poly-adenosyl ribonucleotidyl phosphorylase cleavage indicating caspase activation. Fenretinide treatment also increased levels of the death receptor DR5 and caused mitochondrial membrane depolarization. The levels of the retinoid receptors, retinoic acid receptor alpha and retinoid X receptor gamma, were up-regulated in response to fenretinide, suggestive of ligand-induced receptor up-regulation. IGF-I-induced proliferation in the meningioma cells was abolished by fenretinide. We conclude that fenretinide induces apoptosis in all three histologic subtypes of meningioma and exerts diverse cellular effects, including DR5 up-regulation, modulation of retinoid receptor levels, and inhibition of IGF-I-induced proliferation. These results provide preliminary evidence that fenretinide has activity against meningiomas and suggest that further studies are warranted to explore its potential as a therapeutic agent against meningiomas.

Role of HER-2/neu Overexpression and Clinical Features at Presentation as Predictive Factors in Meningiomas

Prediction of outcome in patients with meningiomas remains a significant problem to date. We have evaluated the role of symptoms at presentation and overexpression of her-2/neu overexpression as independent prognostic factors in meningiomas. In a retrospective study on patients with biopsy-proven diagnosis of meningioma, her-2/neu overexpression was evaluated using immunohistochemistry (IHC) performed on paraffin-embedded specimens. An IHC score of > or =2+ was considered positive for overexpression. Two hundred thirty-seven patients thus identified between January 1986 and December 1999 included 149 females and 88 males, with a mean age of 63.44 years. Survival was estimated using the Kaplan-Meier method. Incidence of meningiomas in females (62.8%) was significantly greater than in males. Focal neurodeficits, headache, and seizures (39.66%) were the most common presenting complaints and were not related to tumor behavior/outcome. Syncope at presentation was associated with a decreased survival, but this symptom constituted only 2.53% of the total, so reliable conclusions could not be drawn. Only 6 (2.53%) specimens revealed HER-2/neu overexpression by IHC. HER-2/neu overexpression is not a predictor of tumor behavior and has no role as a prognostic factor in meningiomas. Syncope as the clinical presentation at diagnosis may predict a poor outcome, but needs further investigation.

Meningiomas: Updating Basic Science, Management, and Outcome

BACKGROUND

Meningiomas are biologically complex and clinically and surgically challenging. These features, combined with the rewarding potential for cure, make them of great interest to neurologists, neurosurgeons, and neuroscientists alike.

REVIEW SUMMARY

Initially, we review the clinical context of meningiomas, particularly recent changes in histopathological classification, diagnosis, and neuroimaging. Secondly, the underlying basic science as it has evolved over the last decades is summarized. The status of areas recently of intense interest, such as steroid hormone receptors and oncogenic viruses is described. Additionally, emerging areas of great promise, such as cytogenetics and molecular biology are presented. Lastly, we describe recent advances in management. In particular, skull-base surgery, image-guided surgery, and advances in radiotherapy are emphasized. The possible impact of basic research on management and outcome is also outlined.

CONCLUSIONS

Although usually benign and amenable to cure, meningiomas still present significant diagnostic and treatment challenges. Advances in basic science, surgery, and adjuvant therapy are widening the potential for safe, effective, evidence-based management leading to even better outcomes

Changes in expression of transferrin, insulin-like growth factor 1, and interleukin 4 receptors after irradiation of cells of primary malignant brain tumor cell lines

Various immunotoxins have been developed for the treatment of cancer. The toxin is internalized by target cells through cell-surface receptors, and it is essential for these receptors to be expressed for the immunotoxin to have specific anti-tumor activity. Radiation therapy is one of the main treatment modalities for primary malignant brain tumors. The purpose of this study was to determine whether radiation influences the expression of cell-surface receptors. Cells of one human medulloblastoma (Daoy) and two glioblastoma (U373-MG and T98-G) cell lines were tested by exposing the cells to a single dose of 5 Gy gamma rays. Expression of transferrin receptors, type-1 insulin-like growth factor receptors (IGF1R), and interleukin 4 receptors (IL4R) was measured by flow cytometry analysis on unirradiated cells and on cells 3 to 120 h after irradiation. In Daoy cells, the absolute expression index of transferrin receptors increased during the 24 h after irradiation with the greatest change of 26% above control at 9 h. The absolute expression index of IGF1R increased 26.5% above control at 12 h. The absolute expression index of IL4R decreased 9 h after irradiation. In U373-MG cells the absolute expression index of transferrin receptors increased during the 24 h after irradiation, and the greatest increase was 45% above control at 9 h. The absolute expression index of IGF1R increased during the 12 h after irradiation with a maximum increase of 33% above control at 6 h. The absolute expression index of IL4R decreased with time after irradiation. In T98-G cells, the absolute expression index of both transferrin receptors and IL4R decreased after irradiation. The results suggest that the expression of growth factor receptors on brain tumor cells may be influenced by radiation. The effect of ionizing radiation on receptor expression should be considered when administration of targeted toxin is combined with radiation. Similar studies with other growth factor receptors used in targeted toxin therapy are recommended.

Comparison of gene expression profiles between frozen original meningiomas and primary cultures of the meningiomas by GeneChip

OBJECTIVE

In vitro experiments are performed on a daily basis to study the molecular biology of tumors. For some benign tumors, however, established cell lines are not always available, or it may not be feasible to establish new ones. In such cases, primary cultures are used to perform in vitro experiments. Gene expression profiles in vitro differ from those in vivo, but information as to which genes have significantly altered levels is limited. In this study, gene expression profiles of meningiomas in primary cultures and frozen tumors were compared.

METHODS

Affymetrix U95A chips were applied to three sets of meningiomas. For each tumor, the gene expression profiles in frozen specimens (Fr) and primary cultures from the same tumor at Pass 5 (P5) and Pass 10 (P10) were compared. A paired t test (P < 0.025) was applied between Fr and P5, and then between Fr and P10. Genes that demonstrated significantly different expression levels in both comparisons were then identified. The expression levels for a subset of these genes were confirmed by quantitative real-time reverse transcription-polymerase chain reaction.

RESULTS

Among 12,000 genes examined, up-regulation of 51 genes by fivefold or more and down-regulation of 19 genes by twofold or more was found in primary cultures (P5 and P10) compared with the corresponding Fr. Up-regulation of genes encoding for extracellular matrix, cytoskeleton, and cell surface receptors was particularly notable.

CONCLUSION

Gene expression of tissue-cultured meningiomas and in situ meningiomas is significantly different for a large number of genes. Therefore, gene expression and therapeutic studies on cultured meningiomas need to be interpreted with caution.

Development of a meningioma in a patient with acromegaly during octreotide treatment: are there any causal relationships?

Somatostatin receptors are highly expressed in almost all meningiomas but in this setting their functional role is not clear. A 59-yr-old woman had been treated with octreotide after an unsuccessful operation for a GH-secreting pituitary adenoma. After 8 yr of treatment, a nuclear magnetic resonance (NMR) scan disclosed a 3 cm meningioma of the tentorium. Mean GH was 2.2 ng/ml and IGF-I 325 ng/ml. Meningioma was resected and tissue was digested to obtain tumor cell suspension. Aim of the study was to measure epidermal growth factor (EGF)-induced proliferation of cultured meningioma cells in the presence of either somatostatin or octreotide. Cells were grown to semiconfluency in Dolbecco's modified eagle medium (D-MEM) supplemented with 10% fetal calf serum (FCS). After 48 h in D-MEM without serum, the medium was replaced by fresh medium plus recombinant EGF (10 ng/ml) and somatostatin or octreotide were added in the final concentrations of 1, 10 and 100 nM. 20 h later 1 microcgCi of 3H-thymidine was added to each well. After 4 h, incorporated radioactivity was measured. While octreotide did not influence significantly cell growth at the three dose tested, somatostatin increased thymidine incorporation dose-dependently (peak 100 nM: 150% +/- 27% vs medium plus EGF, p<0.05). Octreotide effectively suppressed GH secretion in our acromegalic patient but is unlikely that its long-term use could have stimulated the growth of meningioma since it did not significantly influence the in vitro proliferation of the meningioma cells. These results suggest that somatostatin-mediated proliferative effect on meningioma cells is not mediated by the subtype 2 of the somatostatin receptor.

Retroviral expression of a kinase-defective IGF-I receptor suppresses growth and causes apoptosis of CHO and U87 cells in-vivo

BACKGROUND

Phosphatidylinositol-3,4,5-triphosphate (PtdInsP3) signaling is elevated in many tumors due to loss of the tumor suppressor PTEN, and leads to constitutive activation of Akt, a kinase involved in cell survival. Reintroduction of PTEN in cells suppresses transformation and tumorigenicity. While this approach works in-vitro, it may prove difficult to achieve in-vivo. In this study, we investigated whether inhibition of growth factor signaling would have the same effect as re-expression of PTEN.

METHODS

Dominant negative IGF-I receptors were expressed in CHO and U87 cells by retroviral infection. Cell proliferation, transformation and tumor formation in athymic nude mice were assessed.

RESULTS

Inhibition of IGF-IR signaling in a CHO cell model system by expression of a kinase-defective IGF-IR impairs proliferation, transformation and tumor growth. Reduction in tumor growth is associated with an increase in apoptosis in-vivo. The dominant-negative IGF-IRs also prevented growth of U87 PTEN-negative glioblastoma cells when injected into nude mice. Injection of an IGF-IR blocking antibody alphaIR3 into mice harboring parental U87 tumors inhibits tumor growth and increases apoptosis.

CONCLUSION

Inhibition of an upstream growth factor signal prevents tumor growth of the U87 PTEN-deficient glioma to the same extent as re-introduction of PTEN. This result suggests that growth factor receptor inhibition may be an effective alternative therapy for PTEN-deficient tumors.

Expression of insulin-like growth factor-I (IGF-I) in aneurysmal bone cyst

The effects of insulin-like growth factor-I on bone tissue and its role in bone development have been extensively investigated, but there is little information on its role in the pathogenesis of aneurysmal bone cyst. Therefore, using the techniques of immunohistochemistry and in situ hybridization, the authors studied the expression of insulin-like growth factor-I in 19 specimens of aneurysmal bone cyst. Insulin-like growth factor-I or specific mRNA sequences encoding for insulin-like growth factor-I were detectable in all specimens tested and were mainly localized in multinucleate giant cells. In contrast, only insignificant levels of insulin-like growth factor-I expression were detectable in normal human bone tissue. Taken together with the previously reported role of insulin-like growth factor-I in the pathogenesis of giant cell tumor, the findings of this study suggest that insulin-like growth factor-I may play a role in the pathogenesis of aneurysmal bone cyst.

The IGF/IGFBP system in CNS malignancy

The insulin-like growth factor (IGF) system includes IGF-I and IGF-II, the type I and type II IGF receptors, and specific IGF binding proteins (IGFBP-1 to IGFBP-6). These factors regulate both normal and malignant brain growth. Enhanced expression of IGF-I and IGF-II mRNA transcripts has been demonstrated in gliomas, meniningiomas, and other tumours. Abnormal imprinting of IGF-II occurs in gliomas, medulloblastomas, and meningiomas. Both types of IGF receptor are expressed in gliomas and, in particular, the type I IGF receptor appears to be upregulated in malignant brain tissue. Antisense IGF-I receptor mRNA induces an antitumour response, resulting in complete brain tumour regression. Clinical trials for the treatment of brain tumours in humans based on a gene transfer protocol using IGF-I receptor antisense are under way. All six IGFBPs are expressed to a variable extent in brain tumours. High concentrations of IGFBP-2 are found in cerebrospinal fluid from patients with malignant central nervous system tumours; therefore, IGFBP-2 might be a useful marker for these tumours. IGFBP-4 appears to be a negative regulator of tumour proliferation. Both in vitro and in vivo experiments suggest that the IGF system represents an important target for the treatment of malignant central nervous system tumours and the ongoing trials should provide valuable information for future therapeutic approaches.

Human glioma cells transformed by IGF-I triple helix technology show immune and apoptotic characteristics determining cell selection for gene therapy of glioblastoma

AIMS

Insulin-like growth factor type I (IGF-I) antisense cellular gene therapy of tumours is based on the following data: rat glioma or hepatoma cells transfected with the vector encoding IGF-I antisense cDNA lose their tumorigenicity and induce a tumour specific immune response involving CD8(+) T cells. Recently, using the IGF-I triple helix approach in studies of tumorigenicity, major histocompatibility complex class I (MHC-I) antigens were demonstrated in rat glioma transfected cells. This study used comparative IGF-I antisense and triple helix technologies in human primary glioma cells to determine the triple helix strategy that would be most appropriate for the treatment of glioblastoma.

METHODS

The cells were transfected using the IGF-I triple helix expression vector, pMT-AG, derived from the pMT-EP vector. pMT-AG contains a cassette comprising a 23 bp DNA fragment transcribing a third RNA strand, which forms a triple helix structure within a target region of the human IGF-I gene. Using pMT-EP, vectors encoding MHC-I or B7 antisense cDNA were also constructed.

RESULTS

IGF-I triple helix transfected glioma cells are characterised by immune and apoptotic phenomena that appear to be related. The expression of MHC-I and B7 in transfected cells (analysed by flow cytometry) was accompanied by programmed cell death (detected by dUTP fluorescein terminal transferase labelling of nicked DNA and electron microscopic techniques). Cotransfection of these cells with MHC-I and B7 antisense vectors suppressed the expression of MHC-I and B7, and was associated with a pronounced decrease in apoptosis.

CONCLUSION

When designing an IGF-I triple helix strategy for the treatment of human glioblastoma, the transfected tumour cells should have the following characteristics: the absence of IGF-I, the presence of both MHC-I and B7 molecules, and signs of apoptosis.

Activation of the IGF-IR system contributes to malignant growth of human and mouse medulloblastomas

Insulin-like growth factor I receptor (IGF-IR) has been implicated in the normal and malignant growth of many cell types including cells from the central nervous system. In the cerebellar cortex IGF-IR mRNA is found in granular cells and IGF-I stimulation is mitogenic and protects cells from low-potassium-induced apoptosis. Since primitive neuroectodermal tumors/medulloblastomas (PNETs/medulloblastomas) are suspected to originate from the external cerebellar granular layer, it is reasonable to postulate that IGF-IR and/or its signaling molecules may contribute to the transformation of these poorly differentiated cells. To study activation of the IGF-IR system in medulloblastomas, we have utilized an antibody (anti-pY1316) that specifically recognizes the phosphorylated (active) form of the IGF-IR. Medulloblastoma biopsy specimens were positive when examined immunohistochemically with anti-Y1316 antibody. Further analysis of the IGF-IR system was performed in three human (Daoy, TE-671, D283 Med) and four mouse (BsB8, BsB13, Bs-1b, Bs-1c) medulloblastoma cell lines. All the murine cell lines examined express IGF-IR and PI3-kinase at relatively normal levels, and grossly overexpress IRS-1, when compared with normal mouse cerebellum. Within 15 min following IGF-I stimulation both mouse and human cell lines phosphorylate the beta subunit of the IGF-IR, IRS-1, Akt, and MAP kinases. They respond with cell proliferation when stimulated solely with IGF-I and are strongly inhibited when challenged with a dominant negative mutant of the IGF-IR (486/STOP), or with antisense oligonucleotides against the IGF-IR mRNA.

Antitumor activity of the growth hormone receptor antagonist pegvisomant against human meningiomas in nude mice

OBJECT

The authors have previously demonstrated that modulation of the growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis can significantly affect meningioma growth in vitro. These studies were performed to evaluate the efficacy of GH receptor blockade in vivo.

METHODS

Primary cultures from 15 meningioma tumors obtained in humans were xenografted into athymic mice. Approximately 1.5 million cells from each of the 15 tumors were implanted into the flanks of two female mice, one pair for each tumor. One animal from each of the 15 pairs was then treated with the GH receptor antagonist pegvisomant and the other with vehicle alone for 8 weeks. The tumor volume was measured using digital calipers three times per week. The mean tumor volume at the initiation of injections was 284 +/- 18.8 mm3 in the vehicle group and 291.1 +/- 20 mm3 in the pegvisomant group. After 8 weeks of treatment, the mean volume of tumors in the pegvisomant group was 198.3 +/- 18.9 mm3 compared with 350.1 +/- 23.5 mm3 for the vehicle group (p < 0.001). The serum IGF-I concentration in the vehicle group was 319 +/- 12.9 microg/L compared with 257 +/- 9.7 in the pegvisomant group (p < 0.02). A small but significant decrease was observed in circulating IGF binding protein (IGFBP)-3 levels, whereas slight increases occurred with respect to serum IGFBP-1 and IGFBP-4 levels. In the placebo group the tumor weight was 0.092 +/- 0.01 g compared with 0.057 +/- 0.01 g in the pegvisomant group (p < 0.02). The IGF-I and IGF-II concentrations were measured in the tumors by using a tissue extraction method. These human-specific immunoassays demonstrated that there was no autocrine production of IGF-I in any of the tumors, either in the pegvisomant or vehicle group. The IGF-I levels were highly variable (0-38.2 ng/g tissue) and did not differ significantly between treatment groups.

CONCLUSIONS

In an in vivo tumor model, downregulation of the GH/IGF-I axis significantly reduces meningioma growth and, in some instances, causes tumor regression. Because the concentrations of IGF-II in tumor did not vary with pegvisomant treatment and there was no autocrine IGF-I production by the tumors, the mechanism of the antitumor effect is most likely a decrease of IGF-I in the circulation and/or surrounding host tissues. Because the authors have previously demonstrated that the GH receptor is ubiquitously expressed in meningiomas, direct blockade of the GH receptor on the tumors may also be contributing to inhibitory actions.