Hypoxia-inducible factor 1α/vascular endothelial growth factor axis in astrocytomas. Associations with microvessel morphometry, proliferation and prognosis

HIF-1α-mediated LAMC1 overexpression is an unfavorable predictor of prognosis for glioma patients: evidence from pan-cancer analysis and validation experiments

BACKGROUND

Laminin subunit gamma-1 (LAMC1) is a major extracellular matrix molecule involved in the tumor microenvironment. Knowledge of the biological features and clinical relevance of LAMC1 in cancers remains limited.

METHODS

We conducted comprehensive bioinformatics analysis of LAMC1 gene expression and clinical relevance in pan-cancer datasets of public databases and validated LAMC1 expression in glioma tissues and cell lines. The association and regulatory mechanism between hypoxia inducible factor-1α (HIF-1α) and LAMC1 expression were explored.

RESULTS

LAMC1 expression in most cancers in The Cancer Genome Atlas (TCGA) including glioma was significantly higher than that in normal tissues, which had a poor prognosis and were related to various clinicopathological features. Data from the Chinese Glioma Genome Atlas also showed high expression of LAMC1 in glioma associated with poor prognoses. In clinical glioma tissues, LAMC1 protein was highly expressed and correlated to poor overall survival. LAMC1 knockdown in Hs683 glioma cells attenuated cell proliferation, migration, and invasion, while overexpression of LAMC1 in U251 cells leads to the opposite trend. Most TCGA solid cancers including glioma showed enhancement of HIF-1α expression. High HIF-1α expression leads to adverse prognosis in gliomas, besides, HIF-1α expression was positively related to LAMC1. Mechanistically, HIF-1α directly upregulated LAMC1 promotor activity. Hypoxia (2% O2)-treated Hs683 and U251 cells exhibited upregulated HIF-1α and LAMC1 expression, which was significantly attenuated by HIF-1α inhibitor YC-1 and accompanied by attenuated cell proliferation and invasion.

CONCLUSIONS

High expression of LAMC1 in some solid tumors including gliomas suggests a poor prognosis. The hypoxic microenvironment in gliomas activates the HIF-1α/LAMC1 signaling, thereby promoting tumor progression. Targeted intervention on the HIF-1α/LAMC1 signaling attenuates cell growth and invasion, suggesting a new strategy for glioma treatment.

RUVBL1 in Clear-Cell Renal Cell Carcinoma: Unraveling Prognostic Significance and Correlation with HIF1A

This study investigates the roles of RUVBL1 and HIF1A in ccRCC development and explores their clinical significance as prognostic biomarkers. mRNA and protein expressions were analyzed using TCGA data and an institutional tissue cohort, respectively. Correlations with clinicopathological parameters and patient outcomes were assessed. TCGA data revealed significantly elevated RUVBL1 mRNA expression in ccRCC tissues, associated with advanced histological grade, T stage, lymph node metastasis, and clinical stage. High RUVBL1 mRNA expression correlated with inferior overall survival and served as an adverse prognostic factor. Similarly, HIF1A mRNA expression was significantly higher in ccRCC tissues, correlating with worse overall survival and acting as an adverse prognostic factor for treatment outcomes. Simultaneous evaluation of RUVBL1 and HIF1A mRNA expression demonstrated enhanced prognostic capacity, surpassing the predictive power of individual markers. Immunohistochemical staining confirmed substantial upregulation of both RUVBL1 and HIF-1α proteins in ccRCC tissues. Furthermore, high expression of both RUVBL1 and HIF-1α proteins was significantly associated with shorter patient survival time. Our findings underscore the significance of RUVBL1 and HIF-1α as potential prognostic markers in ccRCC, paving the way for further research to translate these insights into clinically relevant applications.

Profiling and Bioinformatics Analyses of Differential Circular RNA Expression in Glioblastoma Multiforme Cells Under Hypoxia

The hypoxia microenvironment is highly associated with GBM's malignant phenotypes. CircRNAs were reported involved in GBM's biological characteristics and regulated by HIF-1α. However, the differential expression profile and role of circRNAs in GBM cells under hypoxia are still unclear. The expression profiles of circRNAs in LN229 and T98G under hypoxia were explored via circRNA sequencing analysis. Those circRNAs significantly dysregulated both in LN229 and T98G and could be found in circBase were selected and validated by qRT-PCR, RNase R digestion reaction, and Sanger sequencing. Normal cell line and fresh GBM tissues were also used for qRT-PCR validation. The roles of differentially expressed circRNAs were evaluated by bioinformatics analyses. There were 672 dysregulated circRNAs in LN229 and 698 dysregulated circRNAs in T98G. GO analysis indicated that the alteration of circRNA expression related to GBM cell's biogenesis and metabolism. KEGG analysis demonstrated that TGF-β signaling pathway, HIF-1 signaling pathway, and metabolism-related signaling pathway were closely associated with differentially expressed circRNAs under hypoxia. These results were confirmed by GSEA analysis. The 6 selected and dysregulated circRNAs both in LN229 and T98G including hsa_circ_0000745, hsa_circ_0020093, hsa_circ_0020094, hsa_circ_0000943, hsa_circ_0004874, and hsa_circ_0002359 were validated by qRT-PCR. Inhibition of hsa_circ_0000745 inhibited GBM cell's proliferation, migration, and invasion. HIF-1α centered circRNA-miRNA-mRNA networks analysis showed that the 6 validated circRNAs could cross-talk with 11 related miRNAs. The circRNA expressions are dysregulated in GBM cell under hypoxia. The 6 validated circRNAs could participate in GBM's development and progression when hypoxia occurs. They might be the candidates for prognostic markers and adjuvant therapeutics of GBM in the future.

Ascorbate content of clinical glioma tissues is related to tumour grade and to global levels of 5-hydroxymethyl cytosine

Gliomas are incurable brain cancers with poor prognosis, with epigenetic dysregulation being a distinctive feature. 5-hydroxymethylcytosine (5-hmC), an intermediate generated in the demethylation of 5-methylcytosine, is present at reduced levels in glioma tissue compared with normal brain, and that higher levels of 5-hmC are associated with improved patient survival. DNA demethylation is enzymatically driven by the ten–eleven translocation (TET) dioxygenases that require ascorbate as an essential cofactor. There is limited data on ascorbate in gliomas and the relationship between ascorbate and 5-hmC in gliomas has never been reported. Clinical glioma samples (11 low-grade, 26 high-grade) were analysed for ascorbate, global DNA methylation and hydroxymethylation, and methylation status of the O-6-methylguanine-DNA methyltransferase (MGMT) promoter. Low-grade gliomas contained significantly higher levels of ascorbate than high-grade gliomas (p = 0.026). Levels of 5-hmC were significantly higher in low-grade than high-grade glioma (p = 0.0013). There was a strong association between higher ascorbate and higher 5-hmC (p = 0.004). Gliomas with unmethylated and methylated MGMT promoters had similar ascorbate levels (p = 0.96). One mechanism by which epigenetic modifications could occur is through ascorbate-mediated optimisation of TET activity in gliomas. These findings open the door to clinical intervention trials in patients with glioma to provide both mechanistic information and potential avenues for adjuvant ascorbate therapy.

Increased Ascorbate Content of Glioblastoma Is Associated With a Suppressed Hypoxic Response and Improved Patient Survival

Glioblastoma multiforme is a challenging disease with limited treatment options and poor survival. Glioblastoma tumours are characterised by hypoxia that activates the hypoxia inducible factor (HIF) pathway and controls a myriad of genes that drive cancer progression. HIF transcription factors are regulated at the post-translation level via HIF-hydroxylases. These hydroxylases require oxygen and 2-oxoglutarate as substrates, and ferrous iron and ascorbate as cofactors. In this retrospective observational study, we aimed to determine whether ascorbate played a role in the hypoxic response of glioblastoma, and whether this affected patient outcome. We measured the ascorbate content and members of the HIF-pathway of clinical glioblastoma samples, and assessed their association with clinicopathological features and patient survival. In 37 samples (37 patients), median ascorbate content was 7.6 μg ascorbate/100 mg tissue, range 0.8 – 20.4 μg ascorbate/100 mg tissue. In tumours with above median ascorbate content, HIF-pathway activity as a whole was significantly suppressed (p = 0.005), and several members of the pathway showed decreased expression (carbonic anhydrase-9 and glucose transporter-1, both p < 0.01). Patients with either lower tumour HIF-pathway activity or higher tumour ascorbate content survived significantly longer than patients with higher HIF-pathway or lower ascorbate levels (p = 0.011, p = 0.043, respectively). Median survival for the low HIF-pathway score group was 362 days compared to 203 days for the high HIF-pathway score group, and median survival for the above median ascorbate group was 390 days, compared to the below median ascorbate group with 219 days. The apparent survival advantage associated with higher tumour ascorbate was more prominent for the first 8 months following surgery. These associations are promising, suggesting an important role for ascorbate-regulated HIF-pathway activity in glioblastoma that may impact on patient survival.

Fenofibrate inhibits hypoxia-inducible factor-1 alpha and carbonic anhydrase expression through activation of AMP-activated protein kinase/HO-1/Sirt1 pathway in glioblastoma cells

Cancer and its associated conditions have significant impacts on public health at many levels worldwide, and cancer is the leading cause of death among adults. Peroxisome proliferator-activated receptor α (PPARα)-specific agonists, fibrates, have been approved by the Food and Drug Administration for managing hyperlipidemia. PPARα-specific agonists exert anti-cancer effects in many human cancer types, including glioblastoma (GBM). Recently, we have reported that the hypoxic state in GBM stabilizes hypoxia-inducible factor-1 alpha (HIF-1α), thus contributing to tumor escape from immune surveillance by activating the expression of the pH-regulating protein carbonic anhydrase IX (CA9). In this study, we aimed to study the regulatory effects of the PPARα agonist fibrate on the regulation of HIF-1α expression and its downstream target protein in GBM. Our findings showed that fenofibrate is the high potency compound among the various fibrates that inhibit hypoxia-induced HIF-1α and CA9 expression in GBM. Moreover, fenofibrate-inhibited HIF-1α expression is mediated by HO-1 activation in GBM cells through the AMP-activated protein kinase (AMPK) pathway. In addition, fenofibrate-enhanced HO-1 upregulation activates SIRT1 and leads to subsequent accumulation of SIRT1 in the nucleus, which further promotes HIF-1α deacetylation and inhibits CA9 expression. Using a protein synthesis inhibitor, cycloheximide, we also observed that fenofibrate inhibited HIF-1α protein synthesis. In addition, the administration of the proteasome inhibitor MG132 showed that fenofibrate promoted HIF-1α protein degradation in GBM. Hence, our results indicate that fenofibrate is a useful anti-GBM agent that modulates hypoxia-induced HIF-1α expression through multiple cellular pathways.

Parenteral high‑dose ascorbate - A possible approach for the treatment of glioblastoma (Review)

For glioblastoma, the treatment with standard of care therapy comprising resection, radiation, and temozolomide results in overall survival of approximately 14-18 months after initial diagnosis. Even though several new therapy approaches are under investigation, it is difficult to achieve life prolongation and/or improvement of patient's quality of life. The aggressiveness and progression of glioblastoma is initially orchestrated by the biological complexity of its genetic phenotype and ability to respond to cancer therapy via changing its molecular patterns, thereby developing resistance. Recent clinical studies of pharmacological ascorbate have demonstrated its safety and potential efficacy in different cancer entities regarding patient's quality of life and prolongation of survival. In this review article, the actual glioblastoma treatment possibilities are summarized, the evidence for pharmacological ascorbate in glioblastoma treatment is examined and questions are posed to identify current gaps of knowledge regarding accessibility of ascorbate to the tumor area. Experiments with glioblastoma cell lines and tumor xenografts have demonstrated that high-dose ascorbate induces cytotoxicity and oxidative stress largely selectively in malignant cells compared to normal cells suggesting ascorbate as a potential therapeutic agent. Further investigations in larger cohorts and randomized placebo-controlled trials should be performed to confirm these findings as well as to improve delivery strategies to the brain, through the inherent barriers and ultimately to the malignant cells.

Member Domain 3 (LRIG3) Activates Hypoxia-Inducible Factor-1 α/Vascular Endothelial Growth Factor (HIF-1α/VEGF) Pathway to Inhibit the Growth of Bone Marrow Mesenchymal Stem Cells in Glioma

Member domain 3 (LRIG3) of the LRIG gene family is down-regulated in several cancers. However, its role in bone marrow mesenchymal stem cells (BMSCs) in gliomas and the related mechanisms is unknown. The qRT-PCR assessed LRIG3 mRNA level. Rat BMSCs were randomly assigned into glioma group (BMSCs cultured in glioma microenvironment); LRIG3 overexpression group; and si-LRIG3 inhibitor group followed by analysis of LRIG3 expression, cell proliferation, PCNA and Ki-67 apoptosis, TNF-α; and HIF-1α/VEGF mRNA level. LRIG3 mRNA expression was decreased in gliomas patients (P < 0.05). BMSCs cultured in glioma microenvironment showed decreased LRIG3, increased cell proliferation, decreased PCNA, Ki-67 and TNF-α secretion as well as elevated HIF-1α and VEGF level (P < 0.05). Transfection of LRIG3 siRNA further promoted the above changes. Conversely, LRIG3 plasmid transfection significantly promoted its expression in glioma BMSCs (P < 0.05), inhibited cell proliferation, promoted PCNA, Ki-67, and TNF-α secretion, and increased HIF-1α and VEGF level (P < 0.05). LRIG3 in rat BMSCs cultured in the glioma microenvironment is decreased. Down-regulation of LRIG3 inhibits TNF-α secretion by activating HIF-1α/VEGF pathway regulating BMSCs proliferation and apoptosis.

The Role of 2-Oxoglutarate Dependent Dioxygenases in Gliomas and Glioblastomas: A Review of Epigenetic Reprogramming and Hypoxic Response

Gliomas are a heterogeneous group of cancers that predominantly arise from glial cells in the brain, but may also arise from neural stem cells, encompassing low-grade glioma and high-grade glioblastoma. Whereas better diagnosis and new treatments have improved patient survival for many cancers, glioblastomas remain challenging with a highly unfavorable prognosis. This review discusses a super-family of enzymes, the 2-oxoglutarate dependent dioxygenase enzymes (2-OGDD) that control numerous processes including epigenetic modifications and oxygen sensing, and considers their many roles in the pathology of gliomas. We specifically describe in more detail the DNA and histone demethylases, and the hypoxia-inducible factor hydroxylases in the context of glioma, and discuss the substrate and cofactor requirements of the 2-OGDD enzymes. Better understanding of how these enzymes contribute to gliomas could lead to the development of new treatment strategies.

Ascorbate and Tumor Cell Iron Metabolism: The Evolving Story and Its Link to Pathology

Significance: Vitamin C or ascorbate (Asc) is a water-soluble vitamin and an antioxidant that is involved in many crucial biological functions. Asc's ability to reduce metals makes it an essential enzyme cofactor. Recent Advances: The ability of Asc to act as a reductant also plays an important part in its overall role in iron metabolism, where Asc induces both nontransferrin-bound iron and transferrin-bound iron uptake at physiological concentrations (∼50 μM). Moreover, Asc has emerged to play an important role in multiple diseases and its effects at pharmacological doses could be important for their treatment. Critical Issues: Asc's role as a regulator of cellular iron metabolism, along with its cytotoxic effects and different roles at pharmacological concentrations, makes it a candidate as an anticancer agent. Ever since the controversy regarding the studies from the Mayo Clinic was finally explained, there has been a renewed interest in using Asc as a therapeutic approach toward cancer due to its minimal side effects. Numerous studies have been able to demonstrate the anticancer activity of Asc through selective oxidative stress toward cancer cells via H₂O₂ generation at pharmacological concentrations. Studies have demonstrated that Asc's cytotoxic mechanism at concentrations (>1 mM) has been associated with decreased cellular iron uptake. Future Directions: Recent studies have also suggested other mechanisms, such as Asc's effects on autophagy, polyamine metabolism, and the cell cycle. Clearly, more has yet to be discovered about Asc's mechanism of action to facilitate safe and effective treatment options for cancer and other diseases.

The relationship between vascular endothelial growth factor and histological grade in intracranial meningioma

Background

Meningioma is the most common benign intracranial neoplasm, accounting for 30% of all primary brain tumors. In 90% of cases, meningiomas are benign. Several aspects of molecular biology, including potential biomarkers, have been studied in attempts to better understand the natural history of meningiomas. Vascular endothelial growth factor (VEGF) is a biomarker responsible for inducing physiological and pathological angiogenesis. VEGF expression has been investigated as a potential predictor of several tumor aspects, including growth rate, recurrence rate, brain tissue invasion, peritumoral edema and surgical prognosis, and also as a marker of histological grade. However, there is no consensus in the literature with respect to the association between this biological factor and meningioma. We digitally analyzed immunohistochemical images using ImageJ software with the aim of correlating VEGF expression with tumor histology.

Methods

Tissue samples from patients presenting with meningioma who had undergone surgical removal between 2007 and 2016 at the Hospital de Clínicas de Porto Alegre (HCPA), in Southern Brazil, were analyzed to identify possible immunohistochemical associations between VEGF and histological grade and subtype.

Results

Seventy-six patients were included; 82% were female, mean age was 59.9 years (range: 18-91). No statistically significant associations were found between VEGF expression and histological grade or subtype (P = 0.310).

Conclusion

Our findings suggest that VEGF is frequently present in meningiomas regardless of histological grade and should not be used as a marker of severity or histological grade.

KLF4K409Q-mutated meningiomas show enhanced hypoxia signaling and respond to mTORC1 inhibitor treatment

Meningioma represents the most common primary brain tumor in adults. Recently several non-NF2 mutations in meningioma have been identified and correlated with certain pathological subtypes, locations and clinical observations. Alterations of cellular pathways due to these mutations, however, have largely remained elusive. Here we report that the Krueppel like factor 4 (KLF4)-K409Q mutation in skull base meningiomas triggers a distinct tumor phenotype. Transcriptomic analysis of 17 meningioma samples revealed that KLF4^K409Q mutated tumors harbor an upregulation of hypoxia dependent pathways. Detailed in vitro investigation further showed that the KLF4^K409Q mutation induces HIF-1α through the reduction of prolyl hydroxylase activity and causes an upregulation of downstream HIF-1α targets. Finally, we demonstrate that KLF4^K409Q mutated tumors are susceptible to mTOR inhibition by Temsirolimus. Taken together, our data link the KLF4^K409Q mediated upregulation of HIF pathways to the clinical and biological characteristics of these skull base meningiomas possibly opening new therapeutic avenues for this distinct meningioma subtype.

Speed Switch in Glioblastoma Growth Rate due to Enhanced Hypoxia-Induced Migration

We analyze the wave speed of the Proliferation Invasion Hypoxia Necrosis Angiogenesis (PIHNA) model that was previously created and applied to simulate the growth and spread of glioblastoma (GBM), a particularly aggressive primary brain tumor. We extend the PIHNA model by allowing for different hypoxic and normoxic cell migration rates and study the impact of these differences on the wave-speed dynamics. Through this analysis, we find key variables that drive the outward growth of the simulated GBM. We find a minimum tumor wave-speed for the model; this depends on the migration and proliferation rates of the normoxic cells and is achieved under certain conditions on the migration rates of the normoxic and hypoxic cells. If the hypoxic cell migration rate is greater than the normoxic cell migration rate above a threshold, the wave speed increases above the predicted minimum. This increase in wave speed is explored through an eigenvalue and eigenvector analysis of the linearized PIHNA model, which yields an expression for this threshold. The PIHNA model suggests that an inherently faster-diffusing hypoxic cell population can drive the outward growth of a GBM as a whole, and that this effect is more prominent for faster-proliferating tumors that recover relatively slowly from a hypoxic phenotype. The findings presented here act as a first step in enabling patient-specific calibration of the PIHNA model.

EZH2, HIF-1, and Their Inhibitors: An Overview on Pediatric Cancers

During the past decades, several discoveries have established the role of epigenetic modifications and cellular microenvironment in tumor growth and progression. One of the main representatives concerning epigenetic modification is the polycomb group (PcG). It is composed of different highly conserved epigenetic effector proteins preserving, through several post-translational modifications of histones, the silenced state of the genes implicated in a wide range of central biological events such as development, stem cell formation, and tumor progression. Proteins of the PcG can be divided in polycomb repressive complexes (PRCs): PRC1 and PRC2. In particular, enhancer of zeste homolog 2 (EZH2), the catalytic core subunit of PRC2, acts as an epigenetic silencer of many tumor suppressor genes through the trimethylation of lysine 27 on histone H3, an essential binding site for DNA methyl transferases and histone deacetylases. A growing number of data suggests that overexpression of EZH2 associates with progression and poor outcome in a large number of cancer cases. Hypoxia inducible factor (HIF) is an important transcription factor involved in modulating cellular response to the microenvironment by promoting and regulating tumor development such as angiogenesis, inflammation, metabolic reprogramming, invasion, and metastatic fate. The HIF complex is represented by different subunits (α and β) acting together and promoting the expression of vascular endothelial growth factor (VEGF), hexokinase II (HKII), receptor for advanced glycation end products (RAGE), carbonic anhydrase (CA), etc., after binding to the hypoxia-response element (HRE) binding site on the DNA. In this review, we will try to connect these two players by detailing the following: (i) the activity and influence of these two important regulators of cancer progression in particular for what concerns pediatric tumors, (ii) the possible correlation between them, and (iii) the feasibility and efficiency to contrast them using several inhibitors.

Divergent changes of p53 in pulmonary arterial endothelial and smooth muscle cells involved in the development of pulmonary hypertension

The tumor-suppressive role of p53, a transcription factor that regulates the expression of many genes, has been linked to cell cycle arrest, apoptosis, and senescence. The noncanonical function or the pathogenic role of p53 has more recently been implicated in pulmonary vascular disease. We previously reported that rapid nuclear accumulation of hypoxia-inducible factor (HIF)-1α in pulmonary arterial smooth muscle cells (PASMCs) upregulates transient receptor potential channels and enhances Ca²⁺ entry to increase cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt). Also, we observed differences in HIF-1α/2α expression in PASMCs and pulmonary arterial endothelial cells (PAECs). Here we report that p53 is increased in PAECs, but decreased in PASMCs, isolated from mice with hypoxia-induced pulmonary hypertension (PH) and rats with monocrotaline (MCT)-induced PH (MCT-PH). The increased p53 in PAECs from rats with MCT-PH is associated with an increased ratio of Bax/Bcl-2, while the decreased p53 in PASMCs is associated with an increased HIF-1α. Furthermore, p53 is downregulated in PASMCs isolated from patients with idiopathic pulmonary arterial hypertension compared with PASMCs from normal subjects. Overexpression of p53 in normal PASMCs inhibits store-operated Ca²⁺ entry (SOCE) induced by passive depletion of intracellularly stored Ca²⁺ in the sarcoplasmic reticulum, while downregulation of p53 enhances SOCE. These data indicate that differentially regulated expression of p53 and HIF-1α/2α in PASMCs and PAECs and the cross talk between p53 and HIF-1α/2α in PASMCs and PAECs may play an important role in the development of PH via, at least in part, induction of PAEC apoptosis and PASMC proliferation.

Clinical imaging of hypoxia: Current status and future directions

Tissue hypoxia is a key feature of many important causes of morbidity and mortality. In pathologies such as stroke, peripheral vascular disease and ischaemic heart disease, hypoxia is largely a consequence of low blood flow induced ischaemia, hence perfusion imaging is often used as a surrogate for hypoxia to guide clinical diagnosis and treatment. Importantly, ischaemia and hypoxia are not synonymous conditions as it is not universally true that well perfused tissues are normoxic or that poorly perfused tissues are hypoxic. In pathologies such as cancer, for instance, perfusion imaging and oxygen concentration are less well correlated, and oxygen concentration is independently correlated to radiotherapy response and overall treatment outcomes. In addition, the progression of many diseases is intricately related to maladaptive responses to the hypoxia itself. Thus there is potentially great clinical and scientific utility in direct measurements of tissue oxygenation. Despite this, imaging assessment of hypoxia in patients is rarely performed in clinical settings. This review summarises some of the current methods used to clinically evaluate hypoxia, the barriers to the routine use of these methods and the newer agents and techniques being explored for the assessment of hypoxia in pathological processes.

Can dynamic contrast-enhanced MRI evaluate VEGF expression in brain glioma? An MRI-guided stereotactic biopsy study

PURPOSE

To investigate whether pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) can be used to evaluate vascular endothelial growth factor (VEGF) expression in brain glioma based on a point-to-point basis.

MATERIALS AND METHODS

Forty-seven patients with treatment-naïve glioma received preoperative DCE-MRI before stereotactic biopsy. We histologically quantified VEGF from section of stereotactic biopsies, and co-registered biopsy locations with localized measurements of DCE-MRI parameters including volume transfer coefficient (K^trans), reverse reflux rate constant (Kep), extracellular extravascular volume fraction (Ve) and blood plasma volume (Vp). The correlations between DCE-MRI parameters (K^trans, Kep, Ve and Vp) and VEGF were determined using Spearman correlation coefficient. P≤.05 was considered statistically significant.

RESULTS

Seventy-nine biopsy samples were obtained and graded into 45 high-grade gliomas (HGGs) and 34 low-grade gliomas (LGGs). K^trans showed a significant positive correlation with VEGF expression in HGGs group (ρ=0.505, P<0.001) and in combined group (LGGs+HGGs) (ρ=0.549, P<0.001), but not in LGGs group (P>0.05). Kep, Ve or Vp was not correlated with VEGF even though a positive trend showed (P>0.05).

CONCLUSIONS

DCE-MRI is a useful, non-invasive imaging technique for quantitative evaluation of VEGF, and its parameter K^trans other than Kep, Ve or Vp may be used as a surrogate for VEGF expression in brain gliomas.

Astrocyte-derived CCL20 reinforces HIF-1-mediated hypoxic responses in glioblastoma by stimulating the CCR6-NF-κB signaling pathway

During tumor development, stromal cells are co-opted to the tumor milieu and provide favorable conditions for the tumor. Hypoxia stimulates cancer cells to acquire a more malignant phenotype via activation of hypoxia-inducible factor 1 (HIF-1). Given that cancer cells and astrocytes in glioblastomas coexist in a hypoxic microenvironment, we examined whether astrocytes affect the adaptation of glioblastoma cells to hypoxia. Immunoblotting, reporter assays, quantitative RT-PCR, and chromatin immunoprecipitation were performed to evaluate HIF-1 signaling in glioblastoma cells. Astrocyte-derived chemokine C-C motif ligand 20 (CCL20) was identified using cytokine arrays, and its role in glioblastoma development was evaluated in orthotopic xenografts. Astrocytes augmented HIF-1α expression in glioblastoma cells under hypoxia. The expression of HIF-1 downstream genes, cancer colony formation, and Matrigel invasion of glioblastoma cells were stimulated by conditioned medium from astrocytes pre-exposed to hypoxia. CCL20 was secreted in a hypoxia-dependent manner from astrocytes and busted the hypoxic induction of HIF-1α in glioblastoma cells. Mechanistically, the CCL20/CCR6 signaling pathway upregulates HIF-1α by stimulating nuclear factor kappa B-driven transactivation of the HIF1A gene. Compared with the control tumors, CCR6-deficient glioblastoma xenografts grew more slowly, with poor vascularization, and expressed lower levels of HIF-1α and its downstream proteins. Furthermore, CCR6 expression was correlated with HIF-1α expression in GEO and TCGA datasets from human glioblastoma tissues. These results suggest that glioblastoma cells adapt well to hypoxic stress by virtue of CCL20 derived from neighboring astrocytes.

Increased risk of brain cancer incidence in stroke patients: a clinical case series, population-based and longitudinal follow-up study

Stroke and brain cancer are two distinct diseases. However, the relationship between both diseases has rarely been examined. This study investigated the longitudinal risk for developing brain cancer in stroke patients. To study this, we first reviewed the malignant gliomas previously with or without stroke using brain magnetic resonance imaging (MRI) images and the past histories. Two ischemic stroke patients before the malignant glioma were identified and belonged to the glioblastoma mutiforme (GBM). Particularly, both GBM specimens displayed strong hypoxia-inducible factor 1α (HIF-1α) expression in immunohistochemical (IHC) staining. To elucidate the significance of this relationship, we then used a nationwide population-based cohort in Taiwan to investigate the risk for the incidence of brain cancer in patients previously with or without stroke. The incidence of all tumors in the stroke group was lower than that in the control group with an adjusted hazard ratio (HR) of 0.79 (95% confidence interval [CI]: 0.74-0.84) in both gender and age older than 60 years. But the stroke patients had higher risk of developing only brain cancer with an adjusted HR of 3.09 (95% CI: 1.80-5.30), and otherwise had lower risk of developing head and neck, digestive, respiratory, bone and skin, as well as other tumors, all with p<0.05. After stratification by gender and age, the female and aged 40-60 year old stroke patients had higher risk of developing brain cancer with an adjusted HR of 7.41 (95% CI: 3.30-16.64) and 16.34 (95% CI: 4.45-62.13), respectively, both with p<0.05. Patients with stroke, in particular female and age 40-60 years old, have an increased risk for developing brain cancer.

3D Pseudocontinuous Arterial Spin-Labeling MR Imaging in the Preoperative Evaluation of Gliomas

BACKGROUND AND PURPOSE

Previous studies showed conflicting results concerning the value of CBF maps obtained from arterial spin-labeling MR imaging in grading gliomas. This study was performed to investigate the effectiveness of CBF maps derived from 3D pseudocontinuous arterial spin-labeling in preoperatively assessing the grade, cellular proliferation, and prognosis of gliomas.

MATERIALS AND METHODS

Fifty-eight patients with pathologically confirmed gliomas underwent preoperative 3D pseudocontinuous arterial spin-labeling. The receiver operating characteristic curves for parameters to distinguish high-grade gliomas from low-grade gliomas were generated. Pearson correlation analysis was used to assess the correlation among parameters. Survival analysis was conducted with Cox regression.

RESULTS

Both maximum CBF and maximum relative CBF were significantly higher in high-grade gliomas than in low-grade gliomas (P < .001). The areas under the curve for maximum CBF and maximum relative CBF in distinguishing high-grade gliomas from low-grade gliomas were 0.828 and 0.863, respectively. Both maximum CBF and maximum relative CBF had no correlation with the Ki-67 index in all subjects and had a moderate negative correlation with the Ki-67 index in glioblastomas (r = -0.475, -0.534, respectively). After adjustment for age, a higher maximum CBF (P = .008) and higher maximum relative CBF (P = .005) were associated with worse progression-free survival in gliomas, while a higher maximum relative CBF (P = .033) was associated with better overall survival in glioblastomas.

CONCLUSIONS

3D pseudocontinuous arterial spin-labeling-derived CBF maps are effective in preoperative evaluation of gliomas. Although gliomas with a higher blood flow are more malignant, glioblastomas with a lower blood flow are likely to be more aggressive.

Evaluation of Hypoxia Inducible Factor-1α and Glucose Transporter-1 Expression in Non Melanoma Skin Cancer: An Immunohistochemical Study

INTRODUCTION

Hypoxia Inducible Factor-1 (HIF-1) is a mediator enabling cell adaptation to hypoxia. It plays its role mainly through transcription of many target genes including Glucose Transporter-1 (GLUT-1) gene.

AIM

The present work aimed at evaluating the pattern and distribution of HIF-1α and GLUT-1 in each case and control.

MATERIALS AND METHODS

A case-control and retrospective study was conducted on archival blocks diagnosed from pathology department as, Basal Cell Carcinoma (BCC, 20 cases), cutaneous Squamous Cell Carcinoma (SCC, 20 cases) and 20 normal site-matched skin biopsies from age and gender-matched healthy subjects as a control. Evaluation of both HIF-1α and GLUT1 expression using standard immunohistochemical techniques was performed on cut sections from selected paraffin embedded blocks.

RESULTS

HIF-1α was expressed in 90%, 35% and 100% of normal skin, BCC and SCC tumour islands respectively. It was up regulated in both BCC and SCC compared with normal skin (p= 0.001, p<0.001 respectively). GLUT-1 was expressed in 100%, 70% and 100% of normal skin, BCC and SCC tumour islands respectively. It was down regulated in Non Melanoma Skin Cancer (NMSC) cases compared with normal skin (p=0.004). HIF-1α and GLUT-1 localization in tumour nests was central, peripheral or central and peripheral. Both HIF-1α and GLUT-1 showed variable expression in stroma, adnexa and inflammatory cells. No significant correlation was found between Histo (H) score or expression percentage values of HIF-1α and those of GLUT-1 in tumour islands or in overlying epidermis either in BCC or SCC.

CONCLUSION

HIF-1α may have a role in NMSC pathogenesis through adaptation to hypoxia which results from excessive proliferation. GLUT-1 down regulation in NMSC may be explained by its consumption by proliferating tumour cells. The expression of HIF-1α and GLUT-1 in normal epidermis, stromal and adnexal structures needs further research.

Comparison of the Effect of Vessel Size Imaging and Cerebral Blood Volume Derived from Perfusion MR Imaging on Glioma Grading

BACKGROUND AND PURPOSE

Vascular proliferation is a major criterion for grading gliomas on the basis of histology. Relative cerebral blood volume can provide pathophysiologic information about glioma grading. Vessel size imaging, in some animals, can be used to estimate the microvascular caliber of a glioma, but its clinical use remains unclear. Herein, we aimed to compare the predictive power of relative cerebral blood volume and vessel size imaging in glioma grading, with grading based on histology.

MATERIALS AND METHODS

Seventy patients with glioma participated in the study; 30 patients underwent MR perfusion imaging with a spin-echo sequence and vessel size imaging with a gradient-echo and spin-echo sequence successively at 24-hour intervals before surgery. We analyzed the vessel size imaging values and relative cerebral blood volume of differently graded gliomas. The microvessel parameters were histologically evaluated and compared with those on MR imaging. The cutoff values of vessel size imaging and relative cerebral blood volume obtained from receiver operating characteristic curve analyses were used to predict glioma grading in another 40 patients.

RESULTS

Vessel size imaging values and relative cerebral blood volume were both increased in high-grade gliomas compared with low-grade gliomas (P < .01). Moreover, vessel size imaging values had higher specificity and sensitivity in differentiating high-grade from low-grade gliomas compared with relative cerebral blood volume. In addition, a significant correlation was observed between vessel size imaging values and microvessel diameters (r > 0.8, P < .05) and between relative cerebral blood volume and microvessel area (r = 0.6579, P < .05). Most important, the use of vessel size imaging cutoff values to predict glioma grading was more accurate (100%) than use of relative cerebral blood volume (85%) values.

CONCLUSIONS

Vessel size imaging can provide more accurate information on glioma grading and may serve as an effective biomarker for the prognosis of patients with gliomas.

Targeting Hypoxia-Inducible Factor 1α in a New Orthotopic Model of Glioblastoma Recapitulating the Hypoxic Tumor Microenvironment

Tissue hypoxia and necrosis represent pathophysiologic and histologic hallmarks of glioblastoma (GBM). Although hypoxia inducible factor 1α (HIF-1α) plays crucial roles in the malignant phenotypes of GBM, developing HIF-1α-targeted agents has been hampered by the lack of a suitable preclinical model that recapitulates the complex biology of clinical GBM. We present a new GBM model, MGG123, which was established from a recurrent human GBM. Orthotopic xenografting of stem-like MGG123 cells reproducibly generated lethal tumors that were characterized by foci of palisading necrosis, hypervascularity, and robust stem cell marker expression. Perinecrotic neoplastic cells distinctively express HIF-1α and are proliferative in both xenografts and the patient tissue. The xenografts contain scattered hypoxic foci that were consistently greater than 50 μm distant from blood vessels, indicating intratumoral heterogeneity of oxygenation. Hypoxia enhanced HIF-1α expression in cultured MGG123 cells, which was abrogated by the HIF-1α inhibitors digoxin or ouabain. In vivo, treatment of orthotopic MGG123 xenografts with digoxin decreased HIF-1α expression, vascular endothelial growth factor mRNA levels, and CD34-positive vasculature within the tumors, and extended survival of mice bearing the aggressive MGG123 GBM. This preclinical tumor model faithfully recapitulates the GBM-relevant hypoxic microenvironment and stemness and is a suitable platform for studying disease biology and developing hypoxia-targeted agents.

A Proposed Paradigm Shift in Initializing Cancer Predictive Models with DCE-MRI Based PK Parameters: A Feasibility Study

Glioblastoma multiforme is the most aggressive type of glioma and the most common malignant primary intra-axial brain tumor. In an effort to predict the evolution of the disease and optimize therapeutical decisions, several models have been proposed for simulating the growth pattern of glioma. One of the latest models incorporates cell proliferation and invasion, angiogenic net rates, oxygen consumption, and vasculature. These factors, particularly oxygenation levels, are considered fundamental factors of tumor heterogeneity and compartmentalization. This paper focuses on the initialization of the cancer cell populations and vasculature based on imaging examinations of the patient and presents a feasibility study on vasculature prediction over time. To this end, pharmacokinetic parameters derived from dynamic contrast-enhanced magnetic resonance imaging using Toft’s model are used in order to feed the model. K^trans is used as a metric of the density of endothelial cells (vasculature); at the same time, it also helps to discriminate distinct image areas of interest, under a set of assumptions. Feasibility results of applying the model to a real clinical case are presented, including a study on the effect of certain parameters on the pattern of the simulated tumor.

mRNA expression levels of hypoxia-induced and stem cell-associated genes in human glioblastoma

The roles of hypoxia-induced and stem cell-associated genes in the development of malignancy and tumour progression are well known. However, there are a limited number of studies analysing the impact of mRNA expression levels of hypoxia-induced and stem cell-associated genes in the tissues of brain tumours and glioblastoma patients. In this study, tumour tissues from patients with glioblastoma multiforme and tumour adjacent tissues were analysed. We investigated mRNA expression levels of hypoxia-inducible factor-1α (HIF-1α), hypoxia-inducible factor-2α (HIF-2α), carbonic anhydrase 9 (CA9), vascular endothelial growth factor (VEGF), glucose transporter-1 (GLUT-1) and osteopontin (OPN), and stem cell-associated genes survivin, epidermal growth factor receptor (EGFR), human telomerase reverse transcriptase (hTERT), Nanog and octamer binding transcription factor 4 (OCT4) using quantitative real-time polymerase chain reaction (qRT-PCR). Our data revealed higher mRNA expression levels of hypoxia-induced and stem cell-associated genes in tumour tissue than levels in the tumour adjacent tissues in patients with glioblastoma multiforme. A strong positive correlation between the mRNA expression levels of HIF-2α, CA9, VEGF, GLUT-1 and OPN suggests a specific hypoxia-associated profile of mRNA expression in glioblastoma multiforme. Additionally, the results indicate the role of stem-cell-related genes in tumour hypoxia. Kaplan-Maier analysis revealed that high mRNA expression levels of hypoxia-induced markers showed a trend towards shorter overall survival in glioblastoma patients (P=0.061). Our data suggest that mRNA expression levels of hypoxia-induced genes are important tumour markers in patients with glioblastoma multiforme.

Correlation between ¹⁸F-fluoromisonidazole PET and expression of HIF-1α and VEGF in newly diagnosed and recurrent malignant gliomas

PURPOSE

Hypoxia and its consequences at the molecular level promote tumour progression and affect patient prognosis. One of the main early cellular events evoked by hypoxia is induction of hypoxia-inducible factor 1 (HIF-1) and subsequent upregulation of vascular endothelial growth factor (VEGF). In this study we sought to determine whether hypoxia detected by (18)F-fluoromisonidazole (FMISO) PET accurately reflects the expression of HIF-1α and VEGF in the tumour and can be used as a biomarker of antiangiogenic treatment and as a prognostic factor in newly diagnosed and recurrent malignant gliomas.

METHODS

Enrolled in this study were 32 patients with newly diagnosed glioma and 16 with recurrent glioma of grade III or grade IV. All the patients had undergone FMISO PET preoperatively. The maximum tumour-to-blood FMISO activity ratio (T/Bmax) was used to evaluate the degree of tumour hypoxia and the hypoxic volume (HV) was calculated using a tumour-to-blood FMISO uptake ratio of ≥1.2. Immunohistochemical expressions of HIF-1α and VEGF were evaluated semiquantitatively using the immunoreactivity score (IRS, scores 0 to 12) and the correlation was examined between IRS of HIF-1α or VEGF and FMISO uptake of the tumour (SUVtumour) using navigation-based sampling. Survival was estimated using the Kaplan-Meier method in relation to the T/Bmax and the HV.

RESULTS

The T/Bmax and the HV in grade IV gliomas were significantly higher than in grade III gliomas (P < 0.01 and P < 0.01, respectively). Moderate to strong HIF-1α and VEGF expression was observed in the majority of malignant gliomas. The IRS of HIF-1α and VEGF in the tumour were not significantly different between grade III and grade IV gliomas. The IRS of HIF-1α in the tumour did not correlate with the SUVtumour of FMISO in either newly diagnosed or recurrent glioma. There was a significant but weak correlation between the IRS of VEGF and the SUVtumour of FMISO in newly diagnosed glioma, but not in recurrent glioma. The overall survival time in patients with a small HV and a low FMISO T/Bmax was significantly longer than in those with a large HV and a high FMISO T/Bmax (P < 0.01 and P < 0.05, respectively).

CONCLUSION

Preoperative FMISO uptake is significantly correlated with the expression of VEGF in the tumour and might be used as a biomarker of antiangiogenic treatment in newly diagnosed malignant gliomas. However, caution is required because the correlation was weak and there was a large overlap of FMISO uptake between glioma with high and low VEGF expression. In addition, hypoxia determined by FMISO PET appears to be a suitable biomarker for predicting a highly malignant tumour and a poor prognosis in patients with malignant glioma.

The role of CXC-chemokine receptor CXCR2 and suppressor of cytokine signaling-3 (SOCS-3) in renal cell carcinoma

BACKGROUND

Chemokine receptor signaling pathways are implicated in the pathobiology of renal cell carcinoma (RCC). However, the clinical relevance of CXCR2 receptor, mediating the effects of all angiogenic chemokines, remains unclear. SOCS (suppressor of cytokine signaling)-3 is a negative regulator of cytokine-driven responses, contributing to interferon-α resistance commonly used to treat advanced RCC with limited information regarding its expression in RCC.

METHODS

In this study, CXCR2 and SOCS-3 were immunohistochemically investigated in 118 RCC cases in relation to interleukin (IL)-6 and (IL)-8, their downstream transducer phosphorylated (p-)STAT-3, and VEGF expression, being further correlated with microvascular characteristics, clinicopathological features and survival. In 30 cases relationships with hypoxia-inducible factors, i.e. HIF-1a, p53 and NF-κΒ (p65/RelA) were also examined. Validation of immunohistochemistry and further investigation of downstream transducers, p-JAK2 and p-c-Jun were evaluated by Western immunoblotting in 5 cases.

RESULTS

Both CXCR2 and IL-8 were expressed by the neoplastic cells their levels being interrelated. CXCR2 strongly correlated with the levels of HIF-1a, p53 and p65/RelA in the neoplastic cells. Although SOCS-3 was simultaneously expressed with p-STAT-3, its levels tended to show an inverse relationship with p-JAK-2 and p-c-Jun in Western blots and were positively correlated with HIF-1a, p53 and p65/p65/RelA expression. Neither CXCR2 nor SOCS-3 correlated with the extent of microvascular network. IL-8 and CXCR2 expression was associated with high grade, advanced stage and the presence/number of metastases but only CXCR2 adversely affected survival in univariate analysis. Elevated SOCS-3 expression was associated with progression, the presence/number of metastasis and shortened survival in both univariate and multivariate analysis.

CONCLUSIONS

Our findings implicate SOCS-3 overexpression in RCC metastasis and biologic aggressiveness advocating its therapeutic targeting. IL-8/CXCR2 signaling also contributes to the metastatic phenotype of RCC cells but appears of lesser prognostic utility. Both CXCR2 and SOCS-3 appear to be related to transcription factors induced under hypoxia.

Levels of vascular endothelial growth factor and matrix metalloproteinase-9 proteins in patients with glioma

OBJECTIVE

To investigate the levels of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) proteins in patients with glioma, in order to determine if either protein has prognostic value.

METHOD

The presence of VEGF and MMP-9 proteins in paraffin-embedded tumour specimens from patients with glioma was detected using immunohistochemistry. The correlation between the levels of VEGF and MMP-9 proteins and tumour grade was analysed.

RESULTS

A total of 32 patients with low-grade gliomas (World Health Organization [WHO] grade II) and 48 patients with high-grade gliomas (WHO grades III-IV) participated in the study. Positive immunohistochemical staining of VEGF and MMP-9 proteins was detected in 58/80 (72.5%) and 60/80 (75.0%) of patients, respectively. The level of VEGF immunostaining was significantly positively correlated with the level of MMP-9 immunostaining (r = 0.78). Significantly more high-grade gliomas (grades III-IV) demonstrated positive VEGF and MMP-9 immunostaining compared with the low grade gliomas (grades I-II).

CONCLUSIONS

These data suggest that VEGF and MMP-9 play an important role in the malignant behaviour of gliomas.

Victory and defeat in the induction of a therapeutic response through vaccine therapy for human and canine brain tumors: a review of the state of the art

Anti-tumor immunotherapy using tumor lysate-based vaccines has made great advances over recent decades. Cancer vaccines aim to elicit adaptive immune responses through various pathways by providing tumor and tumor-associated antigens with an immune stimulant or adjuvant. These anti-tumor vaccines are therefore developed as personalized treatments. Utilizing tumors as a source of vaccine antigens in immunotherapy has demonstrated promising results with minimal toxicity. However, to date, researchers have failed to overcome the overpowering immune suppressive effects within the tumor microenvironment. Immune suppression occurs naturally via multiple mechanisms. These mechanisms serve an important homeostatic role restoring a normal tissue microenvironment following an inflammatory response. Due to these suppressive mechanisms and the inherent heterogeneity of tumors, it is imperative to then elicit and maintain a specific tumoricidal response if vaccine therapy or some other combination of reagents is chosen. In this review, we focus on the historical use of tumors as a source of antigens to elicit a tumoricidal response and the limitations encountered that prevent greater success in immunotherapy. We describe the advantages and disadvantages of various vaccines and their ineffectiveness due to tumor-induced immune suppression.

Oxygen sensing, hypoxia-inducible factors, and disease pathophysiology

Hypoxia-inducible factors (HIFs) are transcriptional activators that function as master regulators of oxygen homeostasis, which is disrupted in disorders affecting the circulatory system and in cancer. The role of HIFs in these diseases has been elucidated by clinical studies and by analyses of mouse models. HIFs play a protective role in the pathophysiology of myocardial ischemia due to coronary artery disease, limb ischemia due to peripheral arterial disease, pressure-overload heart failure, wound healing, and chronic rejection of organ transplants. In contrast, HIFs contribute to the pathogenesis of pulmonary arterial hypertension, systemic hypertension associated with sleep apnea, ocular neovascularization, hereditary erythrocytosis, and cancer.

Application of 62Cu-diacetyl-bis (N4-methylthiosemicarbazone) PET imaging to predict highly malignant tumor grades and hypoxia-inducible factor-1α expression in patients with glioma

BACKGROUND AND PURPOSE

Hypoxic tissue evaluation in glioma is important for predicting treatment response and establishing antihypoxia therapy. In this preliminary study, (62)Cu-ATSM PET was used to determine its validity as a biomarker for distinguishing tumor grade and tissue hypoxia.

MATERIALS AND METHODS

(62)Cu-ATSM PET was performed in 22 patients with glioma, and the (62)Cu-ATSM SUV(max) and T/B ratio were semiquantitatively evaluated. (62)Cu-ATSM uptake distribution was qualitatively evaluated and compared with MR imaging findings. HIF-1α expression, a hypoxia marker, was compared with (62)Cu-ATSM uptake values.

RESULTS

The (62)Cu-ATSM SUV(max) and T/B ratio were significantly higher in grade IV than in grade III gliomas (P = .014 and .018, respectively), whereas no significant differences were found between grade III and grade II gliomas. At a T/B ratio cutoff threshold of 1.8, (62)Cu-ATSM uptake was predictive of HIF-1α expression, with 92.3% sensitivity and 88.9% specificity. The mean T/B ratio was also significantly higher in HIF-1α-positive glioma tissue than in HIF-1α-negative tissue (P = .001). Using this optimal threshold of T/B ratio, (62)Cu-ATSM PET showed regional uptake in 61.9% (13/21) of tumors within the contrast-enhanced region on MR imaging, which was significantly correlated with presence of a necrotic component (P = .002).

CONCLUSIONS

Our results demonstrated that (62)Cu-ATSM uptake is relatively high in grade IV gliomas and correlates with the MR imaging findings of necrosis. Moreover, the (62)Cu-ATSM T/B ratio showed significant correlation with HIF-1α expression. Thus, (62)Cu-ATSM appears to be a suitable biomarker for predicting highly malignant grades and tissue hypoxia in patients with glioma.

Predicting outcomes of patients with intracranial meningiomas using molecular markers of hypoxia, vascularity, and proliferation

BACKGROUND

The natural history of surgically treated intracranial meningiomas can be quite variable. Recurrence and patient outcome cannot currently be predicted with accuracy.

OBJECTIVE

To explore the potential roles of tumor hypoxia-regulated biological markers, preoperative imaging, measures of proliferation, and angiogenesis in predicting patient outcome.

METHODS

Tissue from 263 patients (average follow-up, 75 months) was examined for molecular markers hypoxia-inducible factor-1α (HIF-1α), carbonic anhydrase-IX (CA-IX), and glucose transporter-1 (Glut-1); vascular endothelial growth factor (VEGF); proliferation (MIB-1); and microvascular density (MVD) (Factor VIII). Preoperative magnetic resonance images were also examined for tumor size and peritumoral brain edema (PTBE).

RESULTS

VEGF, HIF-1α, CA-IX, and Glut-1 are positively correlated (P < .001-.005). PTBE was associated with higher grade (P = .03), larger tumors (P = .02), and log of MVD (P = .004). Progression-free survival (PFS) was associated with higher grade (P < .001), subtotal resection (P = .004), VEGF expression (P = .004), and log of MIB-labeling index (P < .001) on pairwise comparisons. Using multivariate analysis, PFS was associated with subtotal resection (HR 2.71, P = .027), higher grade (HR 6.29, P < .001), higher VEGF expression (HR 1.52, P = .038), and log of MIB-labeling index (HR 1.68, P = .005). Shorter overall survival was associated with subtotal resection (HR 3.23, P = .002), higher grade (HR 4.47, P < .001), higher expression of HIF-1α (HR 1.56, P < .001) and Glut-1 (HR 1.39, P = .02), and log of MIB-labeling index (HR 1.87, P < .001) when controlled for age.

CONCLUSION

HIF, VEGF, and MIB-1 are significantly correlated with tumor recurrence. With further study, these molecular markers may be used to predict outcome for patients with intracranial meningiomas.

Vascular endothelial growth factor participates in modulating the C6 glioma-induced migration of rat bone marrow-derived mesenchymal stem cells and upregulates their vascular cell adhesion molecule-1 expression

Bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to be able to migrate towards glioma, but the molecular mechanisms responsible for this migratory behavior still require further elucidation. This study aimed to test the role of vascular endothelial growth factor (VEGF) in the C6 glioma-induced migration of BMSCs, evaluate the effect of VEGF on the migratory capacity and vascular cell adhesion molecule-1 (VCAM-1) expression of BMSCs and explore the role of VCAM-1 in the VEGF-induced migration of BMSCs. The results showed that C6 glioma cells significantly increased the migration of BMSCs in vitro, which was partially blocked by a VEGF neutralizing antibody, and 20 ng/ml recombinant rat VEGF(164) incubation enhanced the migration of BMSCs. Moreover, 12 h of 20 ng/ml VEGF(164) incubation upregulated the VCAM-1 expression of BMSCs and the blocking of VCAM-1 reduced the VEGF(164)-induced migration of BMSCs. The data also revealed that LY294002, an inhibitor of phosphoinositide-3-kinase (PI3K), decreased the VEGF-induced migration and VCAM-1 expression of BMSCs. These findings indicate that VEGF participates in mediating the C6 glioma-induced migration of BMSCs by upregulating their VCAM-1 expression, and that PI3K is involved in the signal transduction of VEGF(164)-induced migration and VCAM-1 expression of BMSCs.

A prospective phase II single-institution trial of sunitinib for recurrent malignant glioma

Single-agent sunitinib, an oral small molecule inhibitor of multiple tyrosine kinase receptors, was evaluated for treatment of patients with recurrent glioblastoma (GB) and anaplastic astrocytoma (AA). Fourteen AA and 16 GB patients, all previously treated with surgery, radiotherapy, and temozolomide, were enrolled in a prospective phase II study at either first or second relapse. Patients were treated with daily sunitinib for 4 consecutive weeks, followed by a 2-week break. For AA patients, the most common side effects were fatigue (86 %), diarrhea (43 %), hand-foot syndrome (36 %), neutropenia (36 %), thrombocytopenia (36 %), and nausea (29 %). In the GB cohort, the most common side effects were fatigue (56 %), diarrhea (44 %), neutropenia (31 %), and thrombocytopenia (25 %). Six of 14 (43 %) AA and 5 of 16 (31 %) GB patients experienced grade 3 or greater toxicities. Five patients discontinued study due to drug toxicities. There were no partial or complete responses in either cohort; 8/14 (57 %) AA and 5/16 (31 %) GB patients had stable disease at the first planned assessment. Progression-free survival at 6 months was 21.5 % (AA) and 16.7 % (GB). Median overall survival was 12.1 months (AA) and 12.6 months (GB). These results are comparable to those reported in the literature in patients treated with standard cytotoxic therapies. This is the largest reported trial of sunitinib in recurrent malignant astrocytic gliomas to date, as well as contains the largest AA cohort. Nonetheless, sunitinib did not demonstrate significant anti-glioma activity in patients with recurrent malignant astrocytic gliomas.

Differential expression of HIF-1 in glioblastoma multiforme and anaplastic astrocytoma

Hypoxia is an important factor mediating tumor progression and therapeutic resistance, in part through proteome changes mediated by the transcription factor hypoxia-inducible factor (HIF)-1. Since glioblastoma multiforme is the epitome of a highly aggressive tumor entity, while lower-grade astrocytomas often show a prolonged clinical course, a profound difference in the extent of hypoxic tissue areas and corresponding magnitude of HIF-1 activity may exist between these entities. In this study, to address this question, serial sections of 11 glioblastomas and 10 anaplastic astrocytomas were immunostained for HIF-1α, glucose transporter (GLUT)-1, carbonic anhydrase (CA) IX (i.e., hypoxia-related markers), Ki67 (proliferation), phosphorylated ribosomal protein S6 [p-rpS6; mammalian target of rapamycin (mTOR) activity] and CD34 (microvascular endothelium). Digital scans of whole tumor sections were registered to achieve geometric correspondence for subsequent morphometric operations. HIF-1α-, GLUT-1- and CA IX-positive staining was found in all 11 glioblastomas, showing a preferential expression in tissue areas adjacent to necroses. A considerable spatial overlap between GLUT-1 and CA IX, and a colocalization of these proteins with areas of enlarged mean diffusion distances were observed. Conversely, 8 of the 10 anaplastic astrocytomas were completely negative for hypoxia-related markers. The glioblastomas also showed significantly greater heterogeneity of intercapillary distances, larger diffusion-limited tissue fractions, significantly higher mTOR activity and a trend for higher proliferation rates. Microregionally, mTOR and proliferation showed a significant spatial overlap with areas of shorter mean diffusion distances. In conclusion, diffusion-limited hypoxia, leading to the expression of hypoxia-related markers is a pivotal element of the glioblastoma phenotype and may be driven by dysregulated growth and proliferation in normoxic subregions.

Phosphorylated 4E-binding protein 1 (p-4E-BP1): a novel prognostic marker in human astrocytomas

AIMS

To investigate the significance of the mammalian target of rapamycin (mTOR) pathway in astrocytic tumours, published information in this context being limited, especially regarding phosphorylated 4E-binding protein (p-4E-BP) 1.

METHODS AND RESULTS

Paraffin-embedded tissue from 111 patients with astroglial tumours (grades II-IV) was investigated for the association of phosphorylated mTOR (p-mTOR) signalling components with phosphorylated extracellular signal-related kinase 1/2 (p-ERK1/2) and phosphorylated AKT (p-AKT) expression, clinicopathological features, angiogenesis, isocitrate dehydrogenase 1 (IDH1)-R132H, and survival. Expression was also quantified by western blot analysis in 12 cases and in three primary glioma cell cultures following rapamycin treatment. p-mTOR expression correlated with p-4E-BP1 expression and marginally with p-p70S6K expression. p-4E-BP1 expression increased with tumour grade. Rapamycin induced a decline in phosphorylation levels of all three proteins. Nuclear p-AKT and cytoplasmic p-ERK1/2 immunoexpression correlated with p-4E-BP1 expression, whereas cytoplasmic p-AKT expression correlated with p-p70S6K expression. All three proteins were associated with increased angiogenesis but not with IDH1-R132H expression status. p-mTOR adversely affected overall and disease-free survival in univariate analysis. In multivariate survival analysis, the presence of p-4E-BP1 predicted shortened overall survival in the entire cohort and glioblastomas.

CONCLUSIONS

mTOR signalling components are differentially involved in the acquisition of a more aggressive and angiogenic phenotype in astrocytic tumours. Moreover, p-4E-BP1 emerges as a novel prognostic marker, which might aid in the selection of patients who are more likely to benefit from therapy with mTOR inhibitors.

Morphometric study of microvessels in primary CNS tumors and its correlation with tumor types and grade

INTRODUCTION

Alterations of microvasculature are integral to CNS neoplasia, and a diagnostic feature of high-grade gliomas. The objectives of this study were two fold: First, to correlate morphometrically measured microvessel density (MVD), microvessel caliber (VC), and percentage of total microvessel area (%TVA) with WHO histologic grade in various types of primary CNS tumors. Second, to evaluate if such a correlation could be further refined by using mathematical derivatives of measured parameters namely coefficient of variation of VC (COofVC), microvessel cross-sectional area (VCSA), and percentage of total VCSA (%TVCSA).

MATERIALS AND METHODS

Various microvessel parameters were assessed in a variety of 30 primary CNS tumors as consecutively encountered in routine surgical pathology practice including gliomas, meningiomas and others by image morphometry using CD34-immunostained sections. We introduced a novel method of effectively determining VC. Results were correlated with tumor type and grade. Appropriate statistical analysis was performed.

RESULTS

Microvessel characteristics, especially VC (p<0.0022), VCSA (p<0.0164), CVofVC (p<0.0001), %TVCSA (p<0.0002) and %TVA (p<0.0003) of tumors were significantly greater than normal tissue. MVD increased in all tumors, excepting meningiomas, and was significantly higher in gliomas (p<0.0062). MVD showed negative correlation with VC (r=-0.808) and VCSA (r=-0.848) in the normal brain but was less significant in tumors. Unlike tumors, caliber distribution of microvessels in normal brain was noted to follow a Gaussian pattern. Histological grades of tumors showed positive correlation with MVD (r=0.547), VC (r=0.606), CVofVC (r=0.623), VCSA (r=0.485), %TVCSA (r=0.783) and %TVA (r=0.603). Calculated scores, estimated from multiple regressions of vessel parameters, correlated well with histological grade, with S2 (calculated using all measured as well as mathematically derived microvessel parameters) being better than S1 (calculated using measured parameters: MVD and VC).

CONCLUSION

Tumor grades positively correlated with all microvessel parameters, with %TVCSA displaying the best. The correlation of %TVA with tumor grade was weaker than %TVCSA mainly due to the impact of MVD. These findings emphasize the value of VC as effectively measured using our novel method and best illustrated by its derivative %TVCSA (an indicator of blood flow), in addition to the well-recognized value of MVD in tumor prognostication. Multiple regressions of microvessel parameters provided the best correlation with grade. Morphometric analysis of microvessels in CNS tumor facilitates a better understanding of the tumor grade, tumor progression and overall prognosis.

Protein phosphatase 2A mediates dormancy of glioblastoma multiforme-derived tumor stem-like cells during hypoxia

PURPOSE

The hypoxic microenvironment of glioblastoma multiforme (GBM) is thought to increase resistance to cancer therapies. Recent evidence suggests that hypoxia induces protein phosphatase 2A (PP2A), a regulator of cell cycle and cell death. The effects of PP2A on GBM tumor cell proliferation and survival during hypoxic conditions have not been studied.

EXPERIMENTAL DESIGN

Expression of PP2A subunits and HIF-α proteins was measured in 65 high-grade astrocytoma and 18 non-neoplastic surgical brain specimens by western blotting. PP2A activity was measured by an immunoprecipitation assay. For in vitro experiments, GBM-derived tumor stem cell-like cells (TSCs) were exposed to severe hypoxia produced by either CoCl₂ or 1% O₂. PP2A activity was inhibited either by okadaic acid or by shRNA depletion of the PP2A C subunit. Effects of PP2A activity on cell cycle progression and cell survival during hypoxic conditions were assessed using flow cytometry.

RESULTS

In our patient cohort, PP2A activity was positively correlated with HIF-1∝ protein expression (P = 0.002). Patients with PP2A activity levels above 160 pMP had significantly worse survival compared to patients with levels below this threshold (P = 0.002). PP2A activity was an independent predictor of survival on multivariable analysis (P = 0.009). In our in vitro experiments, we confirmed that severe hypoxia induces PP2A activity in TSCs 6 hours after onset of exposure. PP2A activity mediated G1/S phase growth inhibition and reduced cellular ATP consumption in hypoxic TSCs. Conversely, inhibition of PP2A activity led to increased cell proliferation, exhaustion of intracellular ATP, and accelerated P53-independent cell death of hypoxic TSCs.

CONCLUSIONS

Our results suggest that PP2A activity predicts poor survival in GBM. PP2A appears to reduce the metabolic demand of hypoxic TSCs and enhances tumor cell survival. Modulation of PP2A may be a potential target for cancer therapy.

Correlations between perfusion MR imaging cerebral blood volume, microvessel quantification, and clinical outcome using stereotactic analysis in recurrent high-grade glioma

BACKGROUND AND PURPOSE

Quantifying MVA rather than MVD provides better correlation with survival in HGG. This is attributed to a specific "glomeruloid" vascular pattern, which is better characterized by vessel area than number. Despite its prognostic value, MVA quantification is laborious and clinically impractical. The DSC-MR imaging measure of rCBV offers the advantages of speed and convenience to overcome these limitations; however, clinical use of this technique depends on establishing accurate correlations between rCBV, MVA, and MVD, particularly in the setting of heterogeneous vascular size inherent to human HGG.

MATERIALS AND METHODS

We obtained preoperative 3T DSC-MR imaging in patients with HGG before stereotactic surgery. We histologically quantified MVA, MVD, and vascular size heterogeneity from CD34-stained 10-μm sections of stereotactic biopsies, and we coregistered biopsy locations with localized rCBV measurements. We statistically correlated rCBV, MVA, and MVD under conditions of high and low vascular-size heterogeneity and among tumor grades. We correlated all parameters with OS by using Cox regression.

RESULTS

We analyzed 38 biopsies from 24 subjects. rCBV correlated strongly with MVA (r = 0.83, P < .0001) but weakly with MVD (r = 0.32, P = .05), due to microvessel size heterogeneity. Among samples with more homogeneous vessel size, rCBV correlation with MVD improved (r = 0.56, P = .01). OS correlated with both rCBV (P = .02) and MVA (P = .01) but not with MVD (P = .17).

CONCLUSIONS

rCBV provides a reliable estimation of tumor MVA as a biomarker of glioma outcome. rCBV poorly estimates MVD in the presence of vessel size heterogeneity inherent to human HGG.

HIF1α and HIF2α: sibling rivalry in hypoxic tumour growth and progression

Hypoxia-inducible factors (HIFs) are broadly expressed in human cancers, and HIF1α and HIF2α were previously suspected to promote tumour progression through largely overlapping functions. However, this relatively simple model has now been challenged in light of recent data from various approaches that reveal unique and sometimes opposing activities of these HIFα isoforms in both normal physiology and disease. These effects are mediated in part through the regulation of unique target genes, as well as through direct and indirect interactions with important oncoproteins and tumour suppressors, including MYC and p53. As HIF inhibitors are currently undergoing clinical evaluation as cancer therapeutics, a more thorough understanding of the unique roles performed by HIF1α and HIF2α in human neoplasia is warranted.

Quantifying the role of angiogenesis in malignant progression of gliomas: in silico modeling integrates imaging and histology

Gliomas are uniformly fatal forms of primary brain neoplasms that vary from low- to high-grade (glioblastoma). Whereas low-grade gliomas are weakly angiogenic, glioblastomas are among the most angiogenic tumors. Thus, interactions between glioma cells and their tissue microenvironment may play an important role in aggressive tumor formation and progression. To quantitatively explore how tumor cells interact with their tissue microenvironment, we incorporated the interactions of normoxic glioma cells, hypoxic glioma cells, vascular endothelial cells, diffusible angiogenic factors, and necrosis formation into a first-generation, biologically based mathematical model for glioma growth and invasion. Model simulations quantitatively described the spectrum of in vivo dynamics of gliomas visualized with medical imaging. Furthermore, we investigated how proliferation and dispersal of glioma cells combine to induce increasing degrees of cellularity, mitoses, hypoxia-induced neoangiogenesis and necrosis, features that characterize increasing degrees of "malignancy," and we found that changes in the net rates of proliferation (ρ) and invasion (D) are not always necessary for malignant progression. Thus, although other factors, including the accumulation of genetic mutations, can change cellular phenotype (e.g., proliferation and invasion rates), this study suggests that these are not required for malignant progression. Simulated results are placed in the context of the current clinical World Health Organization grading scheme for studying specific patient examples. This study suggests that through the application of the proposed model for tumor-microenvironment interactions, predictable patterns of dynamic changes in glioma histology distinct from changes in cellular phenotype (e.g., proliferation and invasion rates) may be identified, thus providing a powerful clinical tool.

Molecular Imaging of Hypoxia: Strategies for Probe Design and Application

Tumor hypoxia is a negative prognostic factor and its precise imaging is of great relevance to therapy planning. The present review summarizes various strategies of probe design for imaging hypoxia with a variety of techniques such as PET, SPECT and fluorescence imaging. Synthesis of some important probes that are used for preclinical and clinical imaging and their mechanism of binding in hypoxia are also discussed.

Carbonic anhydrase IX overexpression is associated with diminished prognosis in esophageal cancer and correlates with Her-2 expression

BACKGROUND

Carbonic anhydrase IX (CAIX), a transmembrane glycoprotein, seems to play a key role in the adaption of tumor cells to hypoxia. This study was designed to investigate the clinical role of CAIX and its association with Her-2 in a large cohort of adeno- (AC) and squamous cell carcinomas (SCC) of the esophagus and their metastases.

METHODS

Expression of CAIX and Her-2 was investigated immunohistochemically in formalin fixed, paraffin-embedded tissue from 330 esophageal cancers (182 ACS, 148 SCCs). Corresponding lymph node metastases in 137 cases, distant metastases in 34 cases, and local recurrences in 14 cases were analyzed for CAIX expression.

RESULTS

A total of 147 cases (44.5%) showed strong CAIX expression (AC: 46.7%; ACC: 41.9%). CAIX status of the primary tumor influenced CAIX expression in corresponding lymph node metastases (P<0.001, linear regression). High CAIX-expression was an independent prognostic factor for shorter overall and disease-free survival (P≤0.05, Cox regression). Twenty-nine ACs (15.9%) and 6 SCCs (4.1%) showed Her-2 overexpression. In AC, a significant positive correlation between the Her-2 status and CAIX expression was found (P=0.009, chi-square test).

CONCLUSIONS

High CAIX expression is associated with shorter survival in esophageal cancer, and the hypoxic phenotype seems to be preserved at least during formation of lymph node metastases. Inhibition of CAIX might reduce the ability of tumor cells to establish disseminated disease. In Her-2 overexpressing ACs, blocking of this tyrosine kinase, e.g., by monoclonal antibodies, might induce this effect.

Inhibition of Nodal suppresses angiogenesis and growth of human gliomas

Angiogenesis is the hallmark of malignant gliomas positively correlated with the vascular endothelial growth factor (VEGF) expression. We previously reported that expression levels of Nodal, a member of transforming growth factor-β super family, correlate with the malignant invasive behavior of human glioma cells. In this study, we show that knockdown of Nodal suppresses glioma angiogenesis by inhibition of VEGF. In human primary glioma specimens, expression of Nodal positively correlates with WHO glioma tumor grades and expression of VEGF in the corresponding glioma specimens. In human U87MG glioma cells, knockdown of endogenous Nodal by RNA interference (RNAi) significantly decreases colony formation and secretion of VEGF. In vivo, cellular depletion of Nodal in U87MG inhibited brain glioma growth and prolonged the survival of mice with U87MG/shNodal glioma compared with controls. Inhibition of Nodal suppressed tumor vessel growth in U87MG gliomas. Using Nodal inhibitor (SB431542), silencing Nodal, or overexpressing Nodal in the U87MG, GBM8401, and GBM glioma cells, our further experiments revealed that Nodal-induced VEGF expression might, at least in part, mediate through the ERK1/2-HIF-1α-mediated signaling pathway. Taken together, our data revealed that alteration of Nodal expression in glioma cells resulted in changes to VEGF secretion, and subsequent colony formation, in vivo tumor growth, and angiogenesis, all of which are consistent with the regulation of VEGF through the ERK1/2-HIF-1α-mediated signaling, suggesting that Nodal may serve as a potential therapeutic target for the treatment of human gliomas.