Expression of hypoxia-related tissue factors in astrocytic gliomas. A multivariate survival study with emphasis upon carbonic anhydrase IX

Small Structural Differences Govern the Carbonic Anhydrase II Inhibition Activity of Cytotoxic Triterpene Acetazolamide Conjugates

Acetylated triterpenoids betulin, oleanolic acid, ursolic acid, and glycyrrhetinic acid were converted into their succinyl-spacered acetazolamide conjugates. These conjugates were screened for their inhibitory activity onto carbonic anhydrase II and their cytotoxicity employing several human tumor cell lines and non-malignant fibroblasts. As a result, the best inhibitors were derived from betulin and glycyrrhetinic acid while those derived from ursolic or oleanolic acid were significantly weaker inhibitors but also of diminished cytotoxicity. A betulin-derived conjugate held a K_i = 0.129 μM and an EC₅₀ = 8.5 μM for human A375 melanoma cells.

A systematic review verified by bioinformatic analysis based on TCGA reveals week prognosis power of CAIX in renal cancer

BACKGROUND

Carbonic anhydrase IX (CAIX) protein has been correlated with progression and survival in patients with some tumors such as head and neck carcinoma. But renal cell carcinoma is an exception. The prognostic value of CAIX in RCC used to be associated with patients' survival according to published works. This study aimed to rectify the former conclusion.

METHODS

This study was registered in PROSPERO (CRD42020160181). A literature search of the PubMed, Embase, Cochrane library and Web of Science databases was performed to retrieve original studies until April of 2022. Twenty-seven studies, including a total of 5462 patients with renal cell carcinoma, were reviewed. Standard meta-analysis methods were used to evaluate the prognostic impact of CAIX expression on patient prognosis. The hazard ratio and its 95% confidence interval were recorded for the relationship between CAIX expression and survival, and the data were analyzed using Stata 11.0. Then we verify the meta-analysis resort to bioinformatics (TCGA).

RESULTS

Our initial search resulted in 908 articles in total. From PubMed, Embase, Web of Science electronic and Cochrane library databases, 493, 318 and 97 potentially relevant articles were discovered, respectively. We took the analysis between CA9 and disease-specific survival (HR = 1.18, 95% CI: 0.82-1.70, I2 = 79.3%, P<0.05), a subgroup then was performed to enhance the result (HR = 1.63, 95%CI: 1.30-2.03, I2 = 26.3%, P = 0.228); overall survival was also parallel with the former (HR = 1.13, 95%CI: 0.82-1.56, I2 = 79.8%, P<0.05), then a subgroup also be performed (HR = 0.90, 95%CI:0.75-1.07, I2 = 23.1%, P = 0.246) to verify the result; the analysis between CAIX and progression-free survival got the similar result (HR = 1.73, 95%CI:0.97-3.09, I2 = 82.4%, P<0.05), we also verify the result by subgroup analysis (HR = 1.04, 95%CI:0.79-1.36, I2 = 0.0%, P = 0.465); at last the relationship between CAIX and recurrence-free survival got the same result, too (HR = 0.99, 95%CI: 0.95-1.02, I2 = 57.8%, P = 0.050), the subgroup's result was also parallel with the former (HR = 1.01, 95%CI: 0.91-1.03, I2 = 0.00%, P = 0.704). To validate our meta-analysis, we took a bioinformatic analysis based on TCGA database, survival curve between low and high CAIX expression in four endpoints (DSS, OS, PFI, DFI) have corresponding P value (DSS:P = 0.23, OS:P = 0.77, PFI:P = 0.25, DFI:P = 0.78).

CONCLUSIONS

CAIX expression in patients with RCC is an exception to predict tumor survival. Both low CAIX expression and high expression are not associated with survivals in RCC patients.

Understanding metabolic alterations and heterogeneity in cancer progression through validated immunodetection of key molecular components: a case of carbonic anhydrase IX

Cancer metabolic heterogeneity develops in response to both intrinsic factors (mutations leading to activation of oncogenic pathways) and extrinsic factors (physiological and molecular signals from the extracellular milieu). Here we review causes and consequences of metabolic alterations in cancer cells with focus on hypoxia and acidosis, and with particular attention to carbonic anhydrase IX (CA IX). CA IX is a cancer-associated enzyme induced and activated by hypoxia in a broad range of tumor types, where it participates in pH regulation as well as in molecular mechanisms supporting cancer cells’ invasion and metastasis. CA IX catalyzes reversible conversion of carbon dioxide to bicarbonate ion plus proton and cooperates with a spectrum of molecules transporting ions or metabolites across the plasma membrane. Thereby CA IX contributes to extracellular acidosis as well as to buffering intracellular pH, which is essential for cell survival, metabolic performance, and proliferation of cancer cells. Since CA IX expression pattern reflects gradients of oxygen, pH, and other intratumoral factors, we use it as a paradigm to discuss an impact of antibody quality and research material on investigating metabolic reprogramming of tumor tissue. Based on the validation, we propose the most reliable CA IX-specific antibodies and suggest conditions for faithful immunohistochemical analysis of molecules contributing to heterogeneity in cancer progression.

The Acidic Brain-Glycolytic Switch in the Microenvironment of Malignant Glioma

Malignant glioma represents a fatal disease with a poor prognosis and development of resistance mechanisms against conventional therapeutic approaches. The distinct tumor zones of this heterogeneous neoplasm develop their own microenvironment, in which subpopulations of cancer cells communicate. Adaptation to hypoxia in the center of the expanding tumor mass leads to the glycolytic and angiogenic switch, accompanied by upregulation of different glycolytic enzymes, transporters, and other metabolites. These processes render the tumor microenvironment more acidic, remodel the extracellular matrix, and create energy gradients for the metabolic communication between different cancer cells in distinct tumor zones. Escape mechanisms from hypoxia-induced cell death and energy deprivation are the result. The functional consequences are more aggressive and malignant behavior with enhanced proliferation and survival, migration and invasiveness, and the induction of angiogenesis. In this review, we go from the biochemical principles of aerobic and anaerobic glycolysis over the glycolytic switch, regulated by the key transcription factor hypoxia-inducible factor (HIF)-1α, to other important metabolic players like the monocarboxylate transporters (MCTs)1 and 4. We discuss the metabolic symbiosis model via lactate shuttling in the acidic tumor microenvironment and highlight the functional consequences of the glycolytic switch on glioma malignancy. Furthermore, we illustrate regulation by micro ribonucleic acids (miRNAs) and the connection between isocitrate dehydrogenase (IDH) mutation status and glycolytic metabolism. Finally, we give an outlook about the diagnostic and therapeutic implications of the glycolytic switch and the relation to tumor immunity in malignant glioma.

The Expression of Carbonic Anhydrases II, IX and XII in Brain Tumors

Carbonic anhydrases (CAs) are zinc-containing metalloenzymes that participate in the regulation of pH homeostasis in addition to many other important physiological functions. Importantly, CAs have been associated with neoplastic processes and cancer. Brain tumors represent a heterogeneous group of diseases with a frequently dismal prognosis, and new treatment options are urgently needed. In this review article, we summarize the previously published literature about CAs in brain tumors, especially on CA II and hypoxia-inducible CA IX and CA XII. We review here their role in tumorigenesis and potential value in predicting prognosis of brain tumors, including astrocytomas, oligodendrogliomas, ependymomas, medulloblastomas, meningiomas, and craniopharyngiomas. We also introduce both already completed and ongoing studies focusing on CA inhibition as a potential anti-cancer strategy.

"Paradoxical" findings of tumor vascularity and oxygenation in recurrent glioblastomas refractory to bevacizumab

Anti-angiogenic therapy induces the apparent normalization of vascular structure, decreases microvessel density (MVD), and improves tumor oxygenation in glioblastomas (GBMs). Six initial and recurrent tumor pairs after bevacizumab (Bev) treatment were compared with GBMs from nine patients resected under neoadjuvant Bev treatment with regard to histological characteristics; MVD; MIB-1 index; and expression of vascular endothelial growth factor (VEGF) and its receptors, hypoxia markers (hypoxia-inducible factor 1 alpha, carbonic anhydrase 9), and nestin as a marker of glioma stem-like cells. In recurrent tumors post-Bev treatment, while the MVD remained low compared with the paired initial tumors (pre-Bev tumors), the expression of hypoxic markers were increased and were even higher in expression compared with the paired pre-Bev tumors in three of the six cases. MIB-1 indices were similar among the initial GBMs, neoadjuvant group, and recurrent tumors post-Bev treatment. The nestin-positive cell ratio of the post-Bev recurrent tumors was as high as that of the pre-Bev tumors. The expression of VEGF and VEGFR1 was increased in the post-Bev recurrent tumors in three and four cases, respectively, compared with the paired pre-Bev tumors. In the majority of Bev-refractory GBMs, tumor hypoxia was present with a paradoxical decrease in MVD. These findings suggest that re-activation of tumor angiogenesis is not initially involved in the acquisition of resistance to Bev.

Prognostic Significance of Carbonic Anhydrase IX Expression in Cancer Patients: A Meta-Analysis

Hypoxia is a characteristic of many solid tumors and an adverse prognostic factor for treatment outcome. Hypoxia increases the expression of carbonic anhydrase IX (CAIX), an enzyme that is predominantly found on tumor cells and is involved in maintaining the cellular pH balance. Many clinical studies investigated the prognostic value of CAIX expression, but most have been inconclusive, partly due to small numbers of patients included. The present meta-analysis was therefore performed utilizing the results of all clinical studies to determine the prognostic value of CAIX expression in solid tumors. Renal cell carcinoma was excluded from this meta-analysis due to an alternative mechanism of upregulation. 958 papers were identified from a literature search performed in PubMed and Embase. These papers were independently evaluated by two reviewers and 147 studies were included in the analysis. The meta-analysis revealed strong significant associations between CAIX expression and all endpoints: overall survival [hazard ratio (HR) = 1.76, 95% confidence interval (95%CI) 1.58–1.98], disease-free survival (HR = 1.87, 95%CI 1.62–2.16), locoregional control (HR = 1.54, 95%CI 1.22–1.93), disease-specific survival (HR = 1.78, 95%CI 1.41–2.25), metastasis-free survival (HR = 1.82, 95%CI 1.33–2.50), and progression-free survival (HR = 1.58, 95%CI 1.27–1.96). Subgroup analyses revealed similar associations in the majority of tumor sites and types. In conclusion, these results show that patients having tumors with high CAIX expression have higher risk of locoregional failure, disease progression, and higher risk to develop metastases, independent of tumor type or site. The results of this meta-analysis further support the development of a clinical test to determine patient prognosis based on CAIX expression and may have important implications for the development of new treatment strategies.

FGF2 as a potential prognostic biomarker for proneural glioma patients

BACKGROUND

The survival of high-grade glioma patients is poor and the treatment of these patients can cause severe side effects. This fosters the necessity to identify prognostic biomarkers, in order to optimize treatment and diminish unnecessary suffering of patients. The aim of this study was to identify prognostic biomarkers for high-grade glioma patients.

METHODS

Eleven proteins were selected for analysis due to their suggested importance for survival of patients with other types of cancers and due to a high variation in protein levels between glioma patients (according to the Human Protein Atlas, www.proteinatlas.org). Protein expression patterns of these 11 proteins were analyzed by immunohistochemistry in tumor samples from 97 high-grade glioma patients. The prognostic values of the proteins were analyzed with univariate and multivariate Cox regression analyses for the high-grade glioma patients, including subgroup analyses of histological subtypes and immunohistochemically defined molecular subtypes.

RESULTS

The proteins with the most significant (univariate and multivariate p<0.05) correlations were analyzed further with cross-validated Kaplan-Meier analyses for the possibility of predicting survival based on the protein expression pattern of the corresponding candidate. Random Forest classification with variable subset selection was used to analyze if a protein signature consisting of any combination of the 11 proteins could predict survival for the high-grade glioma patients and the subgroup with glioblastoma patients. The proteins which correlated most significantly (univariate and multivariate p<0.05) to survival in the Cox regression analyses were Myc for all high-grade gliomas and FGF2, CA9 and CD44 for the subgroup of proneural gliomas, with FGF2 having a strong negative predictive value for survival. No prognostic signature of the proteins could be found.

CONCLUSION

FGF2 is a potential prognostic biomarker for proneural glioma patients, and warrants further investigation.

Membrane carbonic anhydrase IX expression and relapse risk in resected stage I-II non-small-cell lung cancer

BACKGROUND

Adjuvant chemotherapy reduces recurrences of non-small-cell lung cancer (NSCLC). To determine which patients need adjuvant chemotherapy, we assessed factors associated with time to relapse (TTR).

METHODS

In 230 resected stage I-II NSCLCs, we correlated immunohistochemistry scores for factors associated with cell growth rate, growth regulation, hypoxia, cell survival, and cell death with TTR.

RESULTS

With a median follow-up of 82 months (1-158) for those alive and relapse free at last follow-up, median time to recurrence was not reached. The 2- and 5-year probabilities of maintaining freedom from recurrence were 80.7% (95% confidence interval, 75.3%, 86.4%) and 74.6% (95% confidence interval, 68.6%, 81.2%), respectively. TTR curves flattened at an apparent cure rate of 70%. In multicovariate Cox models, factors correlating with shorter TTR were membranous carbonic anhydrase IX (mCAIX) staining (any versus none, hazard ratio = 2.083, p = 0.023) and node stage (N1 versus N0, hazard ratio = 2.591, p = 0.002). mCAIX scores correlated positively with tumor size, grade, squamous histology, necrosis, mitoses, Ki67, p53, nuclear DNA methyltransferase 1, and cytoplasmic enhancer-of-split-and-hairy-related protein, and they correlated inversely with papillary histology, epidermal growth factor receptor mutation (trend), copper transporter-1, and cytoplasmic hypoxia-inducible factor-1α, vascular endothelial growth factor, DNA methyltransferase 1, and excision repair cross-complementing rodent repair deficiency, complementation group 1.

CONCLUSION

Nodal stage and mCAIX immunohistochemistry were the strongest independent predictors of shorter TTR in resected NSCLCs. mCAIX correlated with tumor size, markers of tumor proliferation and necrosis, and tumor genetic characteristics, and it paradoxically correlated inversely with the hypoxia markers, hypoxia-inducible factor-1α and vascular endothelial growth factor. Presence of mCAIX could help determine patients with high risk of recurrence who might require adjuvant chemotherapy.

Hypoxia-induced carbonic anhydrase IX as a target for cancer therapy: from biology to clinical use

The tumor microenvironment includes a complicated network of physiological gradients contributing to plasticity of tumor cells and heterogeneity of tumor tissue. Hypoxia is a key component generating intratumoral oxygen gradients, which affect the cellular expression program and lead to therapy resistance and increased metastatic propensity of weakly oxygenated cell subpopulations. One of the adaptive responses of tumor cells to hypoxia involves the increased expression and functional activation of carbonic anhydrase IX (CA IX), a cancer-related cell surface enzyme catalyzing the reversible conversion of carbon dioxide to bicarbonate ion and proton. Via its catalytic activity, CA IX participates in regulation of intracellular and extracellular pH perturbations that result from hypoxia-induced changes in cellular metabolism producing excess of acid. Through the ability to regulate pH, CA IX also facilitates cell migration and invasion. In addition, CA IX has non-catalytic function in cell adhesion and spreading. Thus, CA IX endows tumor cells with survival advantages in hypoxia/acidosis and confers an increased ability to migrate, invade and metastasize. Accordingly, CA IX is expressed in a broad range of tumors, where it is associated with prognosis and therapy outcome. Its expression pattern and functional implications in tumor biology make CA IX a promising therapeutic target, which can be hit either by immunotherapy with monoclonal antibodies or with compounds inhibiting its enzyme activity. The first strategy has already reached the clinical trials, whereas the second one is still in preclinical testing. Both strategies indicate that CA IX can become a clinically useful anticancer target, but urge further efforts toward better selection of patients for immunotherapy and deeper understanding of tumor types, clinical situations and synthetic lethality interactions with other treatment approaches.

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.

Function of carbonic anhydrase IX in glioblastoma multiforme

Carbonic anhydrase (CA) IX is over-expressed in glioblastoma; however, its functions in this context are unknown. Metabolically, glioblastomas are highly glycolytic, leading to a significant lactic acid load. Paradoxically, the intracellular pH is alkaline. We hypothesized that CAIX contributes to the extrusion of hydrogen ions into the extracellular space, thereby moderating intra- and extracellular pH and creating an environment conductive to enhanced invasion. We investigated the role of CAIX as a prognostic marker in patients with glioblastoma and its biological function in vitro. CAIX expression was analyzed in 59 patients with glioblastoma by immunohistochemistry. The expression levels were correlated to overall survival. In vitro, U251 and Ln 18 glioblastoma cells were incubated under hypoxia to induce CAIX expression, and RNA interference (RNAi) was used to examine the function of CAIX on cell attachment, invasion, intracellular energy transfer, and susceptibility to adjuvant treatment. High CAIX expression was identified as an independent factor for poor survival in patients with glioblastoma. In vitro, cell attachment and invasion were strongly reduced after knockdown of CAIX. Finally, the effects of radiation and chemotherapy were strongly augmented after CAIX interference and were accompanied by a higher rate of apoptotic cell death. CAIX is an independent prognostic factor for poor outcome in patients with glioblastoma. Cell attachment, invasion, and survival during adjuvant treatment are significantly influenced by high CAIX expression. These results indicate that inhibition of CAIX is a potential metabolic target for the treatment of patients with glioblastoma.

Expression of interleukin-8 receptor CXCR2 and suppressor of cytokine signaling-3 in astrocytic tumors

The aim was to expand recently published information regarding the significance of the interleukin (IL)-8/p-STAT-3 (signal transducer and activator of transcription) pathway in astrocytomas, focusing on the IL-8 receptor, chemokine (C-X-C motif) receptor 2 (CXCR2), and the STAT-3 inhibitor SOCS-3 (suppressors of cytokine signaling). A total of 91 paraffin-embedded human astrocytoma tissues (grades II-IV) were investigated for the association of SOCS-3 and CXCR2 expression with clinicopathologic and morphometric microvascular characteristics, vascular endothelial growth factor (VEGF), IL-8 and p-STAT-3 expression and patient survival. Peripheral IL-8 secretion levels were assessed by enzyme-linked immunosorbent spot (ELISPOT). SOCS-3, p-STAT-3 and CXCR2 protein levels were also quantified by Western immunoblotting in six cases, and the protein levels of SOCS-3 and CXCR2 were correlated with the immunohistochemical expression of the respective proteins. All CXCR2-positive cases by Western immunoblotting displayed increased peripheral IL-8 secretion levels. Treatment of primary glioblastoma cell cultures with exogenous IL-8 enhanced proliferation, and this effect was inhibited by treatment with a neutralizing anti-CXCR2 antibody. SOCS-3 and CXCR2 were expressed by neoplastic astrocytes in 92.4% and 48.78% of cases, respectively, with their levels increasing with histological grade and extent of necrosis. VEGF expression and microvessel density, CXCR2 and IL-8 levels were interrelated. SOCS-3 and p-STAT-3 were co-expressed in 85.7% of cases, although they were not interrelated. In univariate survival analysis, increased SOCS-3 expression and the presence of CXCR2 adversely affected survival, whereas in multivariate analysis, only CXCR2 remained significant. The prognostic significance of CXCR2 was validated in an independent set of 63 patients. Our data implicate IL-8/CXCR2 signaling pathway in the progression and regulation of angiogenesis in astrocytomas and provide a rationale for CXCR2 therapeutic exploitation in these tumors.

Expression of carbonic anhydrase IX in craniopharyngiomas

Object

In craniopharyngiomas, cystic growth causes pressure on vital structures of the adjacent brain, leading to significant morbidity. However, the molecular pathogenesis of this cyst formation remains unknown. Carbonic anhydrase IX (CA IX) is a tumor-associated, hypoxia-inducible enzyme, which can cause fluid production and development of cysts. The authors investigated CA IX expression in craniopharyngiomas and its correlation with the extent of cyst formation. In addition, the major pathways of CA IX regulation, hypoxia and p53 mutation, were analyzed.

Methods

Expression of CA IX was analyzed in 20 craniopharyngioma patients by means of in situ hybridization and immunohistochemistry. Preoperative imaging was used to quantify cyst volume. To analyze putative hypoxic induction of CA IX, immunohistochemical staining for HIF-1α and VEGF was performed. Since p53 negatively regulates CA IX expression, we also analyzed the tumors for p53 mutation by direct sequencing.

Results

Significant CA IX was found in 85% of the 20 cases. The extent of CA IX expression was significantly correlated with cyst volume. HIF-1α expression was largely absent in all tissue samples, whereas moderate VEGF expression was present in a subset of cases but without correlation to cyst volume. No p53 mutation was found in any of the analyzed tumors.

Conclusions

Carbonic anhydrase IX, which is virtually absent in normal brain, is significantly upregulated in craniopharyngiomas and shows a significant association with cyst size. The mechanisms of regulation remain unknown, since neither hypoxia nor p53 appears to play a role. These results indicate that inhibition of CA IX may be a potential target for the adjuvant treatment in patients with cystic craniopharyngiomas.

Myeloid biomarkers associated with glioblastoma response to anti-VEGF therapy with aflibercept

PURPOSE

VEGF and infiltrating myeloid cells are known regulators of tumor angiogenesis and vascular permeability in glioblastoma. We investigated potential blood-based markers associated with radiographic changes to aflibercept, which binds VEGF and placental growth factor (PlGF) in patients with recurrent glioblastoma.

EXPERIMENTAL DESIGN

In this single-arm phase II trial, aflibercept was given intravenously every two weeks until disease progression. Plasma and peripheral blood mononuclear cells were collected at baseline and 24 hours, 14 days, and 28 days posttreatment. Plasma cytokines and angiogenic factors were quantified by using ELISA and multiplex bead assays, and myeloid cells were assessed by flow cytometry in a subset of patients.

RESULTS

Circulating levels of VEGF significantly decreased 24 hours after treatment with aflibercept, coincident with radiographic response observed by MRI. PlGF initially decreased 24 hours posttreatment but increased significantly by days 14 and 28. Lower baseline levels of PlGF, elevated baseline levels of CTACK/CCL27, MCP3/CCL7, MIF, and IP-10/CXCL10, and a decrease in VEGFR1(+) monocytes from baseline to 24 hours were all associated with improved response. Tumor progression was associated with increases in circulating matrix metalloproteinase 9.

CONCLUSIONS

These data suggest that decreases in VEGF posttreatment are associated with radiographic response to aflibercept. Elevated baseline chemokines of monocyte lineage in responding patients supports a role for myeloid cells and chemokines as potential biomarkers and regulators of glioma angiogenesis.

The spatial organization of proton and lactate transport in a rat brain tumor

Tumors create a heterogeneous acidic microenvironment which assists their growth and which must be taken into account in the design of drugs and their delivery. In addition, the acidic extracellular pH (pHe) is itself exploited in several experimental techniques for drug delivery. The way the acidity is created is not clear. We report here the spatial organization of key proton-handling proteins in C6 gliomas in rat brain. The mean profiles across the tumor rim of the Na⁺/H⁺ exchanger NHE1, and the lactate-H⁺ cotransporter MCT1, both showed peaks. NHE1, which is important for extension and migration of cells in vitro, showed a peak 1.55 times higher than in extratumoural tissue at 0.33 mm from the edge. MCT1 had a broader peak, further into the tumor (maximum 1.76 fold at 1.0 mm from the edge). In contrast, MCT4 and the carbonic anhydrase CAIX, which are associated with hypoxia, were not significantly upregulated in the rim. The spatial distribution of MCT4 was highly correlated with that of CAIX, suggesting that their expression is regulated by the same factors. Since protons extruded by NHE1 diffuse away through extracellular clefts, NHE1 requires a continuous source of intracellular protons. From the stoichiometries of metabolic pathways that produce or consume H⁺, and the greater availability of glucose compared to oxygen in most parts of a tumor, we support the classic view that most of the net proton efflux from C6 gliomas originates in glycolytic formation of lactate and H⁺ inside the tumor, but add that some lactate is taken up into cells in the rim on MCT1, and some lactate diffuses away, leaving its associated protons available to re-enter cells for extrusion on NHE1. Therapeutic inhibition of NHE1, MCT1 or CAIX is predicted to affect different parts of a tumor.

Dual inhibition of sodium-mediated proton and calcium efflux triggers non-apoptotic cell death in malignant gliomas

Malignant glioma cells maintain an elevated intracellular pH (pH(i)) within hypoxic-ischemic tumor microenvironments through persistent activation of sodium-proton transport (McLean et al., 2000). Amiloride has been reported to selectively kill human malignant glioma cell lines but not primary astrocytes (Hegde et al., 2004). While amiloride reduces pH(i) of malignant gliomas by inhibiting isoform 1 of sodium-proton exchange (NHE1), direct acidification was shown to be cytostatic rather than cytotoxic. At cytotoxic concentrations, amiloride has multiple drug targets including inhibition of NHE1 and sodium-calcium exchange. Amiloride's glioma cytotoxicity can be explained, at least in part, by dual inhibition of NHE1 and of Na(+)-dependent calcium efflux by isoform 1.1 of the sodium-calcium exchanger (NCX1.1), which increases [Ca(2+)](i) and initiates glioma cell demise. As a result of persistent NHE1 activity, cytosolic free levels of sodium ([Na(+)](i)) in U87 and C6 glioma cells are elevated 3-fold, as compared with normal astrocytes. Basal cytosolic free calcium levels ([Ca(2+)](i)) also are increased 5-fold. 2', 4'-dichlorobenzamil (DCB) inhibits the sodium-dependent calcium transporter (NCX1.1) much more potently than NHE1. DCB was employed in a concentration-dependent fashion in glioma cells to selectively inhibit the forward mode of NCX1.1 at ≤1μM, while dually inhibiting both NHE1 and NCX1.1 at ≥20μM. DCB (1μM) was not cytotoxic to glioma cells, while DCB (20μM) further increased basal elevated levels of [Ca(2+)](i) in glioma cells that was followed by cell demise. Cariporide and SEA0400 are more selective inhibitors of NHE1 and NCX1.1 than amiloride or DCB, respectively. Individually, Cariporide and SEA0400 are not cytotoxic, but in combination induced glioma cell death. Like amiloride, the combination of Cariporide and SEA0400 produced glioma cell death in the absence of demonstrable caspase activation.

Prospective evaluation of angiogenic, hypoxic and EGFR-related biomarkers in recurrent glioblastoma multiforme treated with cetuximab, bevacizumab and irinotecan

Several recent studies have demonstrated a beneficial effect of anti-angiogenic treatment with the vascular endothelial growth factor-neutralizing antibody bevacizumab in recurrent high-grade glioma. In the current study, immunohistochemical evaluation of biomarkers involved in angiogenesis, hypoxia and mediators of the epidermal growth factor receptor (EGFR) pathway were investigated. Tumor tissue was obtained from a previous phase II study, treating recurrent primary glioblastoma multiforme (GBM) patients with the EGFR inhibitor cetuximab in combination with bevacizumab and irinotecan. Of the 37 patients with available tumor tissue, 29 were evaluable for response. We concurrently performed immunohistochemical stainings on tumor tissue from 21 GBM patients treated with bevacizumab and irinotecan. We found a tendency of correlation between the hypoxia-related markers, indicating that they share the same regulatory mechanisms. None of the EGFR-related biomarkers showed any significant correlations with each other. None of the biomarkers tested alone or in combination could identify a patient population likely to benefit from bevacizumab and irinotecan, with or without the addition of cetuximab. There is still an urgent need for one or more reliable and reproducible biomarkers able to predict the efficacy of anti-angiogenic therapy.

Trans-sodium crocetinate enhancing survival and glioma response on magnetic resonance imaging to radiation and temozolomide

Object

Glioblastoma (GB) tumors typically exhibit regions of hypoxia. Hypoxic areas within the tumor can make tumor cells less sensitive to chemotherapy and radiation therapy. Trans-sodium crocetinate (TSC) has been shown to transiently increase oxygen to hypoxic brain tumors. The authors examined whether this improvement in intratumor oxygenation translates to a therapeutic advantage when delivering standard adjuvant treatment to GBs.

Methods

The authors used C6 glioma cells to create a hypoxic GB model. The C6 glioma cells were stereotactically injected into the rat brain to create a tumor. Fifteen days later, MR imaging was used to confirm the presence of a glioma. The animals were randomly assigned to 1 of 3 groups: 1) temozolomide alone (350 mg/m2/day for 5 days); 2) temozolomide and radiation therapy (8 Gy); or 3) TSC (100 μg/kg for 5 days), temozolomide, and radiation therapy. Animals were followed through survival studies, and tumor response was assessed on serial MR images obtained at 15-day intervals during a 2-month period.

Results

Mean survival (± SEM) of the temozolomide-alone and the temozolomide/radiotherapy groups was 23.2 ± 0.9 and 29.4 ± 4.4 days, respectively. Mean survival in the TSC/temozolomide/radiotherapy group was 39.8 ± 6 days, a statistically significant improvement compared with either of the other groups (p < 0.05).

Although tumor size was statistically equivalent in all groups at the time of treatment initiation, the addition of TSC to temozolomide and radiotherapy resulted in a statistically significant reduction in the MR imaging–documented mean tumor size at 30 days after tumor implantation. The mean tumor size in the TSC/temozolomide/radiotherapy group was 18.9 ± 6.6 mm2 compared with 42.1 ± 2.7 mm2 in the temozolomide-alone group (p = 0.047) and 35.8 ± 5.1 mm2 in the temozolomide/radiation group (p = 0.004).

Conclusions

In a hypoxic GB model, TSC improves the radiological and clinical effectiveness of temozolomide and radiation therapy. Further investigation of this oxygen diffusion enhancer as a radiosensitizer for hypoxic brain tumors seems warranted.

Patterns of relapse and prognosis after bevacizumab failure in recurrent glioblastoma

BACKGROUND

Bevacizumab has recently been approved by the US Food and Drug Administration for recurrent glioblastoma (GBM). However, patterns of relapse, prognosis, and outcome of further therapy after bevacizumab failure have not been studied systematically.

METHODS

We identified patients at Memorial Sloan-Kettering Cancer Center with recurrent GBM who discontinued bevacizumab because of progressive disease.

RESULTS

There were 37 patients (26 men with a median age of 54 years). The most common therapies administered concurrently with bevacizumab were irinotecan (43%) and hypofractionated reirradiation (38%). The median overall survival (OS) after progressive disease on bevacizumab was 4.5 months; 34 patients died. At the time bevacizumab was discontinued for tumor progression, 17 patients (46%) had an increase in the size of enhancement at the initial site of disease (local recurrence), 6 (16%) had a new enhancing lesion outside of the initial site of disease (multifocal), and 13 (35%) had progression of predominantly nonenhancing tumor. Factors associated with shorter OS after discontinuing bevacizumab were lower performance status and nonenhancing pattern of recurrence. Additional salvage chemotherapy after bevacizumab failure was given to 19 patients. The median progression-free survival (PFS) among these 19 patients was 2 months, the median OS was 5.2 months, and the 6-month PFS rate was 0%.

CONCLUSIONS

Contrast enhanced MRI does not adequately assess disease status during bevacizumab therapy for recurrent glioblastoma (GBM). A nonenhancing tumor pattern of progression is common after treatment with bevacizumab for GBM and is correlated with worse survival. Treatments after bevacizumab failure provide only transient tumor control.

Hypoxia-regulated protein expression, patient characteristics, and preoperative imaging as predictors of survival in adults with glioblastoma multiforme

BACKGROUND

Regions of hypoxia within glioblastoma multiforme (GBM) are common and may influence a tumor's aggressiveness, response to treatment, and the patient's overall survival. In this study, the authors examined 4 markers of hypoxia (hypoxia-inducible factor 1 [HIF-1alpha], glucose transporter 1 [GLUT-1], vascular endothelial growth factor [VEGF], and carbonic anhydrase 9 [CA IX]), cellular proliferation and microvascular density (MVD) indices, extent of surgical resection, and preoperative imaging characteristics and compared them with the overall survival rates of adults with GBM.

METHODS

In this retrospective cohort study, patients who had lower grade astrocytomas were compared with patients who had GBM to verify that the methods used could establish differences between tumor grades. By using preoperative imaging, the amount of necrosis was established versus the overall tumor area. The authors also compared preoperative images with postoperative images to define the amount of tumor resected; and they compared molecular markers, proliferation, MVD, and imaging studies with survival among patients who had GBM.

RESULTS

The hypoxia-regulated molecules (HRMs) and indices for MVD and cellular proliferation were associated significantly with tumor grade. Survival was improved when >or=95% of the tumor was resected. Although the total tumor area was associated with overall survival, no differences were observed when the amount of necrosis or a tumor necrosis index (area of necrosis/area of tumor) was compared with survival. The findings indicated that GLUT-1 and VEGF were correlated with survival after controlling for age.

CONCLUSIONS

Tumor grade was differentiated with HRMs, MVD, and proliferation, but only GLUT-1 predicted survival in this group of patients with GBM. The results suggested that GLUT-1 may be an important independent prognostic indicator.

Expression of nuclear factor-kappaB in human astrocytomas: relation to pI kappa Ba, vascular endothelial growth factor, Cox-2, microvascular characteristics, and survival

Although NF-kappaB has been reported to be constitutively activated in various neoplasms, little information is available about its clinical significance in astrocytomas. In this study, we investigated the association of NF kappa B1/p50 and pI kappa Ba immunohistochemical expression with clinicopathologic features, vascular endothelial growth factor, Cox-2, and microvascular parameters in paraffin-embedded tissue from 82 patients with astrocytomas. pI kappa Ba expression was positively correlated with nuclear (P = .0010) and negatively with cytoplasmic (P = .0008) NF kappa B1/p50 expression. Nuclear NF kappa B1/p50 and pI kappa Ba expression increased with tumor grade (P = .0001 and P < .0001). Nuclear NF kappa B1/p50 was associated with vascular endothelial growth factor (P = .0079), Cox-2 (P = .0500), and total vascular surface area (P = .0430), although the latter was significant only in grades II and III. pI kappa Ba was also positively correlated with microvessel caliber (pI kappa Ba/area; P = .0087). Multivariate analysis selected NF kappa B/p50 expression as an independent prognosticator not only for the entire cohort (P = .0220), but also for grades II and III (P = .0029) and grade IV cases (P = .0310). Our results suggest that nuclear NF kappa B1/p50 expression is dictated by its interaction with I kappa Ba in astrocytomas and is associated with tumor grade and angiogenic factors, denoting the importance of nuclear NF kappa B/p50 expression in patients' prognosis.

Tumor angiogenic and hypoxic profiles predict radiographic response and survival in malignant astrocytoma patients treated with bevacizumab and irinotecan

PURPOSE

The combination of a vascular endothelial growth factor (VEGF) -neutralizing antibody, bevacizumab, and irinotecan is associated with high radiographic response rates and improved survival outcomes in patients with recurrent malignant gliomas. The aim of these retrospective studies was to evaluate tumor vascularity and expression of components of the VEGF pathway and hypoxic responses as predictive markers for radiographic response and survival benefit from the bevacizumab and irinotecan therapy.

PATIENTS AND METHODS

In a phase II trial, 60 patients with recurrent malignant astrocytomas were treated with bevacizumab and irinotecan. Tumor specimens collected at the time of diagnosis were available for further pathologic studies in 45 patients (75%). VEGF, VEGF receptor-2, CD31, hypoxia-inducible carbonic anhydrase 9 (CA9), and hypoxia-inducible factor-2alpha were semiquantitatively assessed by immunohistochemistry. Radiographic response and survival outcomes were correlated with these angiogenic and hypoxic markers.

RESULTS

Of 45 patients, 27 patients had glioblastoma multiforme, and 18 patients had anaplastic astrocytoma. Twenty-six patients (58%) had at least partial radiographic response. High VEGF expression was associated with increased likelihood of radiographic response (P = .024) but not survival benefit. Survival analysis revealed that high CA9 expression was associated with poor survival outcome (P = .016).

CONCLUSION

In this patient cohort, tumor expression levels of VEGF, the molecular target of bevacizumab, were associated with radiographic response, and the upstream promoter of angiogenesis, hypoxia, determined survival outcome, as measured from treatment initiation. Validation in a larger clinical trial is warranted.