EGFR overexpression and radiation response in glioblastoma multiforme

Acquired resistance to cetuximab is associated with the overexpression of Ras family members and the loss of radiosensitization in head and neck cancer cells

PURPOSE

Cetuximab in combination with radiation therapy is used to treat patients with head and neck squamous cell carcinoma (HNSCC). In the present study, the mechanism of acquired resistance to cetuximab in HNSCC cells was investigated in vitro.

MATERIAL AND METHODS

The HNSCC cell lines UT5 and SAS and UT5 cells with acquired resistance to cetuximab (UT5R9) were used. The radiotoxicity potentials of cetuximab and inhibitors of PI3K, MAPK and farnesylation were tested using a clonogenic survival assay. Western blotting was used to evaluate protein expression. The levels of EGFR ligands were detected by ELISA.

RESULTS

Cetuximab inhibited proliferation and induced radiosensitization in UT5 cells but not in SAS cells. In comparison with UT5 cells, cetuximab-resistant SAS cells markedly overexpressed the K-Ras, H-Ras and N-Ras proteins, as detected by Western blotting. Resistance in UT5R9 cells was associated with the overexpression of the K-Ras, H-Ras and N-Ras proteins as well as an increase in the autocrine production of the EGFR ligands amphiregulin and transforming growth factor α (TGFα). UT5R9 cells were significantly more radioresistant than UT5 cells. Radioresistant UT5R9 cells were not radiosensitized by cetuximab, but knocking down H-RAS and N-RAS with siRNA and targeting Ras farnesylation using the farnesyltransferase inhibitor lonafarnib induced radiosensitization in these cells. Targeting PI3K and MEK revealed that the activation of the PI3K/Akt pathway but not the MAPK/ERK pathway is associated with radioresistance in UT5R9 cells.

CONCLUSION

Targeting Ras and PI3K activity improves the outcome of irradiation in cetuximab-resistant HNSCC cell lines in vitro.

LRIG1 dictates the chemo-sensitivity of temozolomide (TMZ) in U251 glioblastoma cells via down-regulation of EGFR/topoisomerase-2/Bcl-2

In the current study, we aimed to understand the potential role of leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) in TMZ-resistance of U251 glioma cells. We established TMZ-resistant U251 clones (U251/TMZ cells), which expressed low level of LRIG1, but high levels of epidermal growth factor receptor (EGFR), topoisomerase-2 (Topo-2) and Bcl-2. Depletion of LRIG1 by the targeted RNA interference (RNAi) upregulated EGFR/Topo-2/Bcl-2 in U251 cells, and the cells were resistant to TMZ. Reversely, over-expression of LRIG1 in U251 cells downregulated EGFR/Topo-2/Bcl-2 expressions, and cells were hyper-sensitive to TMZ. Our data suggested EGFR-dependent mammalian target of rapamycin (mTOR) activation was important for Topo-2 and Bcl-2 expressions in U251/TMZ cells. The EGFR inhibitor and the mTOR inhibitor downregulated Topo-2/Bcl-2 expressions, both inhibitors also restored TMZ sensitivity in U251/TMZ cells. Finally, inhibition of Topo-2 or Bcl-2 by targeted RNAi(s) knockdown or by the corresponding inhibitor re-sensitized U251/TMZ cells to TMZ, indicating that both Topo-2 and Bcl-2 were important for TMZ resistance in the resistant U251 cells. Based on these results, we concluded that LRIG1 inhibits EGFR expression and the downstream signaling activation, interferes with Bcl-2/Topo-2 expressions and eventually sensitizes glioma cells to TMZ.

Glycogen synthase kinase-3β (GSK-3β) and its dysregulation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most frequently occurring and devastating human brain malignancy, retaining almost universal mortality and a median survival of only 14 months, even with recent advances in multimodal treatments. Gliomas are characterised as being both highly resistant to chemo- and radiotherapy and highly invasive, rendering conventional interventions palliative. The continual dismal prognosis for GBM patients identifies an urgent need for the evolutionary development of new treatment modalities. This includes molecular targeted therapies as many signaling molecules and associated pathways have been implicated in the development and survival of malignant gliomas including the protein kinase, glycogen synthase kinase 3 beta (GSK-3β). Here we review the activity and function of GSK-3β in a number of signaling pathways and its role in gliomagenesis.

Receptor tyrosine kinases: principles and functions in glioma invasion

Protein tyrosine kinases are enzymes that are capable of adding a phosphate group to specific tyrosines on target proteins. A receptor tyrosine kinase (RTK) is a tyrosine kinase located at the cellular membrane and is activated by binding of a ligand via its extracellular domain. Protein phosphorylation by kinases is an important mechanism for communicating signals within a cell and regulating cellular activity; furthermore, this mechanism functions as an "on" or "off" switch in many cellular functions. Ninety unique tyrosine kinase genes, including 58 RTKs, were identified in the human genome; the products of these genes regulate cellular proliferation, survival, differentiation, function, and motility. Tyrosine kinases play a critical role in the development and progression of many types of cancer, in addition to their roles as key regulators of normal cellular processes. Recent studies have revealed that RTKs such as epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), c-Met, Tie, Axl, discoidin domain receptor 1 (DDR1), and erythropoietin-producing human hepatocellular carcinoma (Eph) play a major role in glioma invasion. Herein, we summarize recent advances in understanding the role of RTKs in glioma pathobiology, especially the invasive phenotype, and present the perspective that RTKs are a potential target of glioma therapy.

A new prognostic scoring scale for patients with primary WHO grade III gliomas based on molecular predictors

This study was designed to select molecular markers associated with prognosis, and to propose a prognostic scoring scale for patients with primary WHO grade III gliomas based on these molecular predictors. A series of 83 grade III glioma patients surgically treated and pathologically confirmed in Beijing Tiantan Hospital between May 2009 and December 2010 were retrospectively reviewed in the study. Log-rank analysis was used to identify molecular markers associated with progression-free survival (PFS) and overall survival (OS), which were further assessed using Cox regression analysis. Based on the prognostic molecular markers, a scoring scale was proposed and Kaplan-Meier plots were compared between different scoring levels by Log-rank method. Age <50, 1p/19q co-deletion, IDH1/2 mutation, negative MGMT and EGFR expression were correlated with longer PFS and OS. Cox regression confirmed age <50 and 1p/19q co-deletion as independent prognostic markers. This scoring scale mainly based on prognostic molecular markers stratified patients into four levels with different prognoses. Longer PFS and OS were correlated with higher scores (P < 0.05). This scoring scale based on prognostic molecular markers identified four levels with significantly different prognoses, and could be used to predict the prognosis of patients with primary WHO grade III gliomas.

RTOG 0211: a phase 1/2 study of radiation therapy with concurrent gefitinib for newly diagnosed glioblastoma patients

PURPOSE

To determine the safety and efficacy of gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, in combination with radiation for newly diagnosed glioblastoma (GBM) patients.

METHODS AND MATERIALS

Between March 21, 2002, and May 3, 2004, Radiation Therapy Oncology Group (RTOG) 0211 enrolled 31 and 147 GBM patients in the phase 1 and 2 arms, respectively. Treatment consisted of daily oral gefinitnib started at the time of conventional cranial radiation therapy (RT) and continued post RT for 18 months or until progression. Tissue microarrays from 68 cases were analyzed for EGFR expression.

RESULTS

The maximum tolerated dose (MTD) of gefitinib was determined to be 500 mg in patients on non-enzyme-inducing anticonvulsant drugs (non-EIAEDs). All patients in the phase 2 component were treated at a gefitinib dose of 500 mg; patients receiving EIADSs could be escalated to 750 mg. The most common side effects of gefitinib in combination with radiation were dermatologic and gastrointestinal. Median survival was 11.5 months for patients treated per protocol. There was no overall survival benefit for patients treated with gefitinib + RT when compared with a historical cohort of patients treated with RT alone, matched by RTOG recursive partitioning analysis (RPA) class distribution. Younger age was significantly associated with better outcome. Per protocol stratification, EGFR expression was not found to be of prognostic value for gefitinib + RT-treated patients.

CONCLUSIONS

The addition of gefitinib to RT is well tolerated. Median survival of RTOG 0211 patients treated with RT with concurrent and adjuvant gefitinib was similar to that in a historical control cohort treated with radiation alone.

Neural development and the ontogeny of central nervous system tumors

Recent evidence argues that the oncogenesis and growth of CNS tumors occurs through dysregulated molecular and cellular mechanisms of neural development. New insights have emerged that have had a significant impact on both research and treatment of these cancers.

Pediatric high grade glioma: a review and update on tumor clinical characteristics and biology

High grade gliomas (HGG) are one of the most common central nervous system (CNS) tumors encountered in adults, but they only represent approximately 8–12% of all pediatric CNS tumors. Historically, pediatric HGG were thought to be similar to adult HGG since they appear histologically identical; however, molecular, genetic, and biologic data reveal that they are distinct. Similar to adults, pediatric HGG are very aggressive and malignant lesions with few patients achieving long-term survival despite a variety of therapies. Initial treatment strategies typically consist of a gross total resection (GTR) when feasible followed by focal radiotherapy combined with chemotherapy. Over the last few decades, a wealth of data has emerged from basic science and pre-clinical animal models helping to better define the common biologic, genetic, and molecular make-up of these tumors. These data have not only provided a better understanding of tumor biology, but they have also provided new areas of research targeting molecular and genetic pathways with the potential for novel treatment strategies and improved patient outcomes. Here we provide a review of pediatric non-brainstem HGG, including epidemiology, presentation, histology, imaging characteristics, treatments, survival outcomes, and an overview of both basic and translational research. An understanding of all relevant pre-clinical tumor models, including their strengths and pitfalls is essential in realizing improved patient outcomes in this population.

Review: molecular pathology in adult high-grade gliomas: from molecular diagnostics to target therapies

The classification of malignant gliomas is moving from a morphology-based guide to a system built on molecular criteria. The development of a genomic landscape for gliomas and a better understanding of its functional consequences have led to the development of internally consistent molecular classifiers. However, development of a biologically insightful classification to guide therapy is still a work in progress. Response to targeted treatments is based not only on the presence of drugable targets, but rather on the molecular circuitry of the cells. Further, tumours are heterogeneous and change and adapt in response to drugs. Therefore, the challenge of developing molecular classifiers that provide meaningful ways to stratify patients for therapy remains a major challenge for the field. In this review, we examine the potential role of MGMT methylation, IDH1/2 mutations, 1p/19q deletions, aberrant epidermal growth factor receptor and PI3K pathways, abnormal p53/Rb pathways, cancer stem-cell markers and microRNAs as prognostic and predictive molecular markers in the setting of adult high-grade gliomas and we outline the clinically relevant subtypes of glioblastoma with genomic, transcriptomic and proteomic integrated analyses. Furthermore, we describe how these advances, especially in epidermal growth factor receptor/PI3K/mTOR signalling pathway, affect our approaches towards targeted therapy, raising new challenges and identifying new leads.

Towards tailored therapy of glioblastoma multiforme

Gliobastoma multiform (GBM) is the most common and aggressive brain tumor, which is characterized by its infiltrative nature. Current standard therapy for GBMs consists of surgery followed by radiotherapy combined with the alkylating agent temozolomide (TMZ). Recent clinical trials have demonstrated that this chemo-irradiation approach results in a significant increase in survival compared to radiotherapy alone. Nevertheless, due to tumor recurrence, the median survival time is still limited to approximately 15 months. Recently, several studies have focused on aberrant signal transduction in GBM, resistance mechanisms of GBM to TMZ and to radiotherapy. Attention has been focused on molecular targets including phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, protein kinase C (pKC) pathway, Ras/mitogen-activated protein kinase pathway (MAPK), Wnt pathway and intrinsic or extrinsic apoptosis pathways. In addition, research has been directed to radiotherapy and radiosensitizing agents, and cancer gene therapy as well. This article will address several resistance mechanisms of GBM to chemotherapy and radiotherapy and the recent preclinical and clinical studies on targeted therapy.

Targetable "driver" mutations in non small cell lung cancer

Lung cancer remains the leading cause of cancer-related mortality in the world despite advances in the field of cancer therapeutics. Traditional treatment with empirically chosen cytotoxic chemotherapeutic agents, have given small, but real survival benefits. Recent advances and insights into molecular pathogenesis of lung cancers have provided some novel molecular targets, offering newer strategies and agents that are tumor specific. Studies have identified mutations in specific genes that are involved in driving the development of lung cancer and so it is important to subsequently target them with specific drugs thus changing paradigms of management of this type of cancer. Recently, Lung Cancer Mutation Consortium (LCMC) has identified at least one of the many recognized "driver mutations" in nearly two thirds of the patients with advanced cancer. This study suggests that identification of driver mutations can help in molecular targeted therapeutics and in addition supplant tumor histology in guiding treatment decisions, identifying subset of patients who may benefit therapy. This review focuses on these mutations identified in specific genes serving as "drivers" of lung tumorigenesis and suggests that clear promise for the future of lung cancer treatment is indeed personalized therapy with drugs chosen according to the patient mutation profile. Most clinically relevant translational advances made in genes involved in lung tumorigenesis namely EML4-ALK fusions, HER2, PIK3CA, AKT, BRAF, MAP2K1, MET mutations and amplifications along with the well established EGFR and KRAS mutations are discussed in the context of NSCLCs. These studies emphasize the need for treatment management based on mutation profile along with routine histology based classification of these tumors in future for a directed therapy and thus a better therapeutic outcome.

Aberrant signaling pathways in glioma

Glioblastoma multiforme (GBM), a WHO grade IV malignant glioma, is the most common and lethal primary brain tumor in adults; few treatments are available. Median survival rates range from 12–15 months. The biological characteristics of this tumor are exemplified by prominent proliferation, active invasiveness, and rich angiogenesis. This is mainly due to highly deregulated signaling pathways in the tumor. Studies of these signaling pathways have greatly increased our understanding of the biology and clinical behavior of GBM. An integrated view of signal transduction will provide a more useful approach in designing novel therapies for this devastating disease. In this review, we summarize the current understanding of GBM signaling pathways with a focus on potential molecular targets for anti-signaling molecular therapies.

Age-dependent prognostic effects of EGFR/p53 alterations in glioblastoma: study on a prospective cohort of 140 uniformly treated adult patients

AIMS

To assess the prognostic influence of EGFR amplification/overexpression, p53 immunoreactivity and their age-dependent prognostic effects in a large prospective cohort of uniformly treated adult patients with newly diagnosed glioblastoma.

METHODS

Tumours from a uniformly treated prospective cohort of adult patients with newly diagnosed glioblastoma (n=140) were examined for EGFR amplification by fluorescence in situ hybridisation and EGFR/p53 expression by immunohistochemistry. Statistical methods were employed to assess the degree of association between EGFR amplification/overexpression and p53 immunopositivity. Survival analyses were performed by employing Cox proportional hazard models to assess the independent prognostic value of EGFR/p53 alterations and test the propensity for risk with age by assessing their interaction with patient age.

RESULTS

A strong positive correlation between EGFR amplification and EGFR overexpression (rho=0.5157; p<0.0001; CI 0.3783 to 0.6309) and a negative association of EGFR amplification (rho=-0.3417; p<0.0001; CI -0.4842 to -0.1816) and EGFR overexpression (rho=-0.3095; p<0.001; CI -0.4561 to -0.1465) with p53 immunopositivity was observed. Only patient age (HR: 1.029; p=0.004; CI 1.009 to 1.049) was associated with shorter survival by univariate Cox regression analysis. Multivariable Cox proportional hazards models revealed a statistically significant interaction between EGFR overexpression and age to be associated with shorter survival (HR: 1.001; p<0.0001; CI 1.000 to 1.002), thus predicting a higher hazard with increasing age. No age interaction of EGFR amplification status (HR: 1.001; p=0.642; CI 0.995 to 1.008) and p53 immunopositivity (HR: 1.000; p=0.841; CI 0.999 to 1.001) was noted in this cohort.

CONCLUSIONS

The prognostic value of EGFR overexpression is age-dependent, and there is a propensity for a higher hazard with increasing patient age. Identifying such groups of patients with more aggressive disease becomes mandatory, since they would benefit from intense therapeutic protocols targeting EGFR.

Molecular diagnostics of gliomas: state of the art

Modern neuropathology serves a key function in the multidisciplinary management of brain tumor patients. Owing to the recent advancements in molecular neurooncology, the neuropathological assessment of brain tumors is no longer restricted to provide information on a tumor's histological type and malignancy grade, but may be complemented by a growing number of molecular tests for clinically relevant tissue-based biomarkers. This article provides an overview and critical appraisal of the types of genetic and epigenetic aberrations that have gained significance in the molecular diagnostics of gliomas, namely deletions of chromosome arms 1p and 19q, promoter hypermethylation of the O6-methylguanine-methyl-transferase (MGMT) gene, and the mutation status of the IDH1 and IDH2 genes. In addition, the frequent oncogenic aberration of BRAF in pilocytic astrocytomas may serve as a novel diagnostic marker and therapeutic target. Finally, this review will summarize recent mechanistic insights into the molecular alterations underlying treatment resistance in malignant gliomas and outline the potential of genome-wide profiling approaches for increasing our repertoire of clinically useful glioma markers.

A stereological study of MRI and the Cavalieri principle combined for diagnosis and monitoring of brain tumor volume

In this study, we aimed to describe the application of the Cavalieri principle for the assessment of tumor volume using MRI without an over-projection/estimation effect. For this purpose, the volume of a patient's brain and the brain tumor volume, or the volume of the former tumor region, were estimated preoperatively and postoperatively using a combination of the Cavalieri principle and MRI. The previously described formula was modified for MRI measurements to eliminate the over-estimation effects of imaging. The total brain and tumor volumes estimated using the MRI of a representative patient with glioblastoma multiforme were: preoperative, 1562.46 cm³ and 81.59 cm³, respectively; and postoperative, 1571.72 cm³ and 86.92 cm³, respectively. The mean time to count points for an estimation of brain and tumor volume (or the volume of the former tumor region) were 14 minutes and 3 minutes, respectively. The coefficients of the errors of the estimates for brain and tumor volume (former tumor volume, postoperative) measurements were: preoperative 0.01 and 0.02; and postoperative 0.01 and 0.03, respectively. Our results show that the combination of MRI and the Cavalieri principle can provide an unbiased, direct and assumption-free estimate of the regions of interest. Therefore, the presented method could be applied efficiently without any need for special software, additional equipment or personnel other than that required for routine MRI in daily use.

Biomarkers in radiation oncology

The discovery of biomarkers in patients receiving radiation therapy for cancer is occurring at an exceptional pace. There are a number of ways to conduct biomarker investigations, although the majority of clinically relevant biomarker studies have used immunohistochemistry (IHC) on tissue specimens. Using IHC, expression of several pre-radiation biomarkers, such as VEGF, EGFR, YKL-40, murine double minute 2 and Rad51, has been associated with a poor outcome. Because tumor tissue may be difficult to obtain and IHC studies can be difficult to reproduce and standardize, investigators have attempted to find similar results when studying biomarkers of nontumor biospecimens, such as serum and urine. This has led to the discovery of a number of soluble biomarkers predictive of outcome (e.g., YKL-40, VEGF and matrix metallopeptidase-2). As we transition from the use of biopsy-based markers to surrogate soluble biomarkers in the hope of bringing these biomarkers into clinical use, we must ensure methods of standardization in sample collection, processing, storage and analysis to allow widespread reproducibility and accuracy of results.

Polymorphisms in EGFR and VEGF contribute to non-small-cell lung cancer survival in a Chinese population

Over the last decades, combined chemotherapies that inhibit different signalling pathways together have been demonstrated to be more effective to treat the non-small-cell lung cancer (NSCLC). The epidermal growth factor receptor (EGFR) and the vascular endothelium growth factor (VEGF) are two key targets. Polymorphisms in EGFR and VEGF genes have been identified to be associated with therapy-response and cancer survival. In this study, we hypothesized that single-nucleotide polymorphisms (SNPs) of EGFR and VEGF genes are associated with NSCLC patients' survival in Chinese. Therefore, we screened and genotyped 54 potentially functional SNPs as well as tagging SNPs in these two genes using Illumina Golden Gate platform in 568 NSCLC patients. We found that subjects carrying EGFR rs3735061AA and rs6958497AG/GG genotypes survived significantly shorter time [median survival time (MST): 22.2 and 19.4 months, respectively] than those carrying rs3735061AG/GG (MST: 25.1 months) and rs6958497AA (MST: 25.9 months) (log-rank P = 0.015 for rs3735061 and log-rank P = 0.028 for rs6958497). However, subjects carrying EGFR rs759165AG/AA genotypes survived significantly longer (MST: 38.7 months) than those carrying rs759165GG genotype (MST: 24.7 months) (log-rank P = 0.024). Multivariate Cox regression analyses showed that the genotypes of rs3735061AA and rs6958497AG/GG were associated with a significantly increased risk of death for NSCLC [hazard ratio (HR) = 2.82, 95% confidence interval (CI) = 1.66-4.78 for rs3735061AA and HR = 1.69, 95% CI = 1.26-2.28 for rs6958497AG/GG], whereas the rs759165AG/AA were associated with a 44% significantly decreased risk of death of NSCLC (HR = 0.56, 95% CI = 0.39-0.83). Stepwise COX regression analyses suggested that EGFR rs373506, rs759165 and rs6958497 may be independent candidate biomarkers to predict NSCLC survival in this population.

Overexpression of c-erbB2 is a negative prognostic factor in anaplastic astrocytomas

The epidermal growth factor receptor (EGFR) family, consisting of four tyrosine kinase receptors, c-erbB1-4, seems to be influential in gliomagenesis. The aim of this study was to investigate EGFR gene amplification and expression of c-erbB1-4 receptor proteins in human anaplastic astrocytomas. Formalin-fixed and paraffin-embedded sections from 31 cases were investigated by standard immunohistochemical procedures for expression of c-erbB1-4 receptor proteins using commercial antibodies. EGFR gene amplification was studied by fluorescence in situ hybridization using paraffin-embedded tissues. Two monoclonal antibodies, NCL-EGFR-384 and NCL-EGFR, were used for EGFR detection and they displayed positive immunoreactivity in 97% and 71%, respectively. For c-erbB2 detection three monoclonal antibodies, CB11, 3B5, and 5A2, were applied and they displayed positive immunoreactivity in 45%, 100%, and 52%, respectively. Positive immunostaining for c-erbB3 and c-erbB4 was encountered in 97% and 74%, respectively. The EGFR gene was amplified in 9 out of 31 tumors (29%). After adjusting for age, Karnofsky performance status, and extent of surgical resection, Cox multiple regression analysis with overall survival as the dependent variable revealed that c-erbB2 overexpression detected by the monoclonal antibody clone CB11 was a statistically significant poor prognostic factor (P = 0.004). This study shows the convenience and feasibility of immunohistochemistry when determining the expression of receptor proteins in tissue sections of human astrocytomas. The synchronous overexpression of c-erbB1-4 proteins in anaplastic astrocytomas supports their role in the pathogenesis of these tumors. Further, c-erbB2 overexpression seems to predict aggressive behaviour.

Epidermal growth factor receptor expression in feline oral squamous cell carcinomas

Feline oral squamous cell carcinomas (SCC) have a poor prognosis despite aggressive treatment with surgery, radiation and anticancer drugs. Overexpression of the epidermal growth factor receptor (EGFR), a membrane-bound tyrosine kinase receptor, has been found in many human epithelial neoplasms, including oral SCC. EGFR overexpression has been associated with advanced disease and a poor prognosis. The purpose of this study was to determine whether feline oral SCC express EGFR. Thirteen formalin-fixed paraffin wax-embedded biopsy samples from feline oral SCC were analysed for EGFR expression using immunohistochemistry. Nine of 13 tumours (69%) were positive for EGFR expression, suggesting that altered EGFR expression plays a role in feline oral SCC and provides a rationale for a potential clinical benefit using EGFR inhibitors in combination with conventional treatments.

Phase II trial of erlotinib with temozolomide and radiation in patients with newly diagnosed glioblastoma multiforme

Approximately 40-50% of glioblastomas (GBM) overexpress epidermal growth factor receptor (EGFR). Erlotinib is a specific and potent EGFR tyrosine kinase inhibitor active against refractory GBM. Patients with non-small cell lung cancer and > or =grade 2 erlotinib-induced rash have improved survival. This phase 2 study assessed the efficacy and safety of concurrent radiation therapy (RT) and temozolomide with pharmacodynamic dose escalation of erlotinib in patients with newly diagnosed GBM. Patients received RT 60 Gy in 30 fractions with concurrent temozolomide 75 mg/m(2)/day x 42 days, followed in four weeks by temozolomide 150-200 mg/m(2)/day x 5, every 28 days for 12 cycles. Patients received erlotinib, 50 mg/day and increased by 50 mg/day every 2 weeks until the occurrence of grade 2 rash or to a maximum dose of 150 mg/day, from day 1 until disease progression. Twenty-seven patients were treated in this study. Twenty-two (81%) patients came off study for progressive disease (18 [67%]) or adverse events (4 [15%]). Eighteen patients (67%) have died. Median progression-free survival was 2.8 months, and the median overall survival was 8.6 months. Five patients remain on study with a median follow-up of 16 months. Grade 3/4 toxicities included thrombocytopenia, anemia, lymphopenia, fatigue, and febrile neutropenia. There were four deaths on study, three definitely treatment-related; therefore, the trial was terminated after accrual of 27 of 30 planned patients. Erlotinib co administered with RT and temozolomide was not efficacious and had an unacceptable toxicity.

Robust detection of EGFR copy number changes and EGFR variant III: technical aspects and relevance for glioma diagnostics

Epidermal growth factor receptor (EGFR) is commonly affected in cancer, generally in the form of an increase in DNA copy number and/or as mutation variants [e.g., EGFR variant III (EGFRvIII), an in-frame deletion of exons 2-7]. While detection of EGFR aberrations can be expected to be relevant for glioma patients, such analysis has not yet been implemented in a routine setting, also because feasible and robust assays were lacking. We evaluated multiplex ligation-dependent probe amplification (MLPA) for detection of EGFR amplification and EGFRvIII in DNA of a spectrum of 216 diffuse gliomas. EGFRvIII detection was verified at the protein level by immunohistochemistry and at the RNA level using the conventionally used endpoint RT-PCR as well as a newly developed quantitative RT-PCR. Compared to these techniques, the DNA-based MLPA assay for EGFR/EGFRvIII analysis tested showed 100% sensitivity and specificity. We conclude that MLPA is a robust assay for detection of EGFR/EGFRvIII aberrations. While the exact diagnostic, prognostic and predictive value of such EGFR testing remains to be seen, MLPA has great potential as it can reliably and relatively easily be performed on routinely processed (formalin-fixed, paraffin-embedded) tumor tissue in combination with testing for other relevant glioma markers.

Interaction of ionizing radiation and ZRBA1, a mixed EGFR/DNA-targeting molecule

ZRBA1 is a molecule termed 'combi-molecule' designed to induce DNA-alkylating lesions and to block epidermal growth factor receptor (EGFR) tyrosine kinase. Owing to its ability to downregulate the EGFR tyrosine kinase-mediated antiapoptotic signaling and DNA repair proteins, we inferred that it could significantly sensitize cells to ionizing radiation. Using the MDA-MB-468 human breast cancer cell line in which ZRBA1 has already been reported to induce significant EGFR/DNA-targeting potency, the results showed that: (i) concurrent administration of ZRBA1 and 4 Gy radiation led to a significant decrease in cell viability, (ii) the greater efficacy of the combination was sequential, being limited to conditions wherein the drug was administered concurrently with radiation or before radiation, and (iii) the efficacy enhancement of the combination was further confirmed by clonogenic assays from which a dose enhancement factor of 1.34 could be observed at survival fraction of 0.01. Flow cytometric analysis showed significant enhancement of cell cycle arrest in G2/M (P<0.046, irradiated cells vs. cells treated with ZRBA1 and radiation) and increased apoptosis when ZRBA1 was combined with radiation. Likewise, significant levels of double-strand breaks were observed for the combination, as determined by neutral comet assay (P<0.045, irradiated cells vs. cells treated with ZRBA1 and radiation). These results in toto suggest that the superior efficacy of the ZRBA1 plus radiation combination may be secondary to the ability of ZRBA1 to arrest the cells in G2/M, a cell cycle phase in which tumor cells are sensitive to radiation. Furthermore, the increased levels of DNA damage, combined with the concomitant downregulation of EGFR-mediated signaling by ZRBA1, may account for the significant levels of cell killing induced by the combination.

Therapeutic inhibition of the epidermal growth factor receptor in high-grade gliomas: where do we stand?

High-grade gliomas account for the majority of intra-axial brain tumors. Despite abundant therapeutic efforts, clinical outcome is still poor. Thus, new therapeutic approaches are intensely being investigated. Overexpression of the epidermal growth factor receptor (HER1/EGFR) is found in various epithelial tumors and represents one of the most common molecular abnormalities seen in high-grade gliomas. Dysregulated HER1/EGFR is found in 40% to 50% of glioblastoma, the most malignant subtype of glioma. Several agents such as tyrosine kinase (TK) inhibitors, antibodies, radio-immuno conjugates, ligand-toxin conjugates, or RNA-based agents have been developed to target HER1/EGFR or its mutant form, EGFRvIII. To date, most agents are in various stages of clinical development. Clinical data are sparse but most advanced for TK inhibitors. Although data from experimental studies seem promising, proof of a significant clinical benefit is still missing. Among the problems that have to be further addressed is the prediction of the individual patient's response to HER1/EGFR-targeted therapeutics based on molecular determinants. It is quite possible that blocking HER1/EGFR alone will not sufficiently translate into a clinical benefit. Therefore, a multiple target approach concomitantly aimed at different molecular sites might be a favorable concept. This review focuses on current HER1/EGFR-targeted therapeutics and their development for high-grade gliomas.

Repeated molecular testing in gliomas: a retrospective study of 53 cases

The value of repeated molecular testing in patients with multiple resections of gliomas is unclear. The purpose of this study was to assess for evidence of molecular changes for chromosome 1p/19q deletions and epidermal growth factor receptor (EGFR) amplification by fluorescence in situ hybridization in 53 glioma cases in which repeated testing was done. Paired results for 1p evaluation demonstrated a change in the profile from intact to loss in 1 (2%) of 50 cases; 19q evaluation demonstrated a change in profile in 4 (10%) of 41 cases. There was no change in the EGFR expression in any of the cases tested. There was no change in the clinical management based on the repeated molecular tests in patients with discrepant repeated results. Hence, there seems to be no indication for reflex repeated 1p/19q or EGFR testing in gliomas at the time of repeated biopsy or resection.

Molecular mechanisms underlying effects of epidermal growth factor receptor inhibition on invasion, proliferation, and angiogenesis in experimental glioma

PURPOSE

Epidermal growth factor receptor (EGFR) signal transduction pathways are implicated in malignant glioma aggressiveness and promote tumor cell invasion, proliferation, and angiogenesis. Nevertheless, response to EGFR tyrosine kinase inhibitor gefitinib (Iressa, ZD1839) has been disappointing in clinical trials. One potential explanation may come from the diversity of molecular alterations seen in gliomas. To validate that hypothesis, we have investigated responses to gefitinib on various tumor parameters in human malignant gliomas that exhibited different molecular alterations.

EXPERIMENTAL DESIGN

We used a panel of six human malignant gliomas from established xenografts characterized for their genetic (EGFR, PTEN, TP53, and CDKN2A) and molecular (EGFR, PTEN, ERK, and Akt) alterations. Tumors were treated with gefitinib (1 or 10 micromol/L) for prolonged periods (8 or 16 days) in an organotypic brain slice model that allowed quantification of invasion, proliferation, and angiogenesis.

RESULTS

In nontreated tumors, EGFR amplification was associated with profuse tumor cell invasion. After treatment, invasion was inhibited in tumors with EGFR amplification in a dose-dependent manner. Treatment had only antiproliferative effect in two of three tumors with EGFR amplification. Tumors with PTEN loss were resistant to treatment. We did not observe shrinkage of the tumors after treatment. None of the tumors had mutations of the EGFR kinase domain. Gefitinib had similar antiangiogenic effect in all of the tumors.

CONCLUSIONS

Gefitinib reduces cell invasion in EGFR amplified tumors. PTEN loss of expression seems to be a determinant of resistance. Interestingly, inhibition of angiogenesis by gefitinib seems independent on the EGFR genetic status of the tumors.

Radiosensitisation of U87MG brain tumours by anti-epidermal growth factor receptor monoclonal antibodies

As epidermal growth factor receptor (EGFR) has been reported to be a radiation response modulator, HER inhibitors are regarded to act as potential radiosensitisers. Our study examined the role of nimotuzumab and cetuximab both, the two monoclonal antibodies (mAbs) to EGFR, as radiosensitisers in a murine glioma model in vivo. Co-administration of both the antibodies with radiation increased the radiosensitivity of U87MG, resulting in a significant delay of subcutaneous (s.c.) tumour growth. Furthermore, the addition of antibodies to the radiation decreased brain tumour sizes and is inhibited by 40–80% the increased tumour cell invasion provoked by radiotherapy, although promoted tumour cell apoptosis. Whereas nimotuzumab led to a reduction in the size of tumour blood vessels and proliferating cells in s.c. tumours, cetuximab had no significant antiangiogenic nor antiproliferative activity. In contrast, cetuximab induced a more marked inhibition of EGFR downstream signalling compared with nimotuzumab. Moreover, both antibodies reduced the total number of radioresistant CD133+ cancer stem cells (CSCs). These results were encouraging, and showed the superiority of combined treatment of mAbs to EGFR and radiation over each single therapy against glioblastoma multiforme (GBM), confirming the role of these drugs as radiosensitisers in human GBM. In addition, we first showed the ability of mAb specifics against EGFR to target radioresistant glioma CSC, supporting the potential use in patients.

Tyrosine phosphorylation of the human glutathione S-transferase P1 by epidermal growth factor receptor

Epidermal growth factor receptor (EGFR) gene amplification, mutations, and/or aberrant activation are frequent abnormalities in malignant gliomas and other human cancers and have been associated with an aggressive clinical course and a poor therapeutic outcome. Elevated glutathione S-transferase P1 (GSTP1), a major drug-metabolizing and stress response signaling protein, is also associated with drug resistance and poor clinical outcome in gliomas and other cancers. Here, we provide evidence that GSTP1 is a downstream EGFR target and that EGFR binds to and phosphorylates tyrosine residues in the GSTP1 protein in vitro and in vivo. Mass spectrometry and mutagenesis analyses in a cell-free system and in gliomas cells identified Tyr-7 and Tyr-198 as major EGFR-specific phospho-acceptor residues in the GSTP1 protein. The phosphorylation increased GSTP1 enzymatic activity significantly, and computer-based modeling showed a corresponding increase in electronegativity of the GSTP1 active site. In human glioma and breast cancer cells, epidermal growth factor stimulation rapidly increased GSTP1 tyrosine phosphorylation and decreased cisplatin sensitivity. Lapatinib, a clinically active EGFR inhibitor, significantly reversed the epidermal growth factor-induced cisplatin resistance. These data define phosphorylation and activation of GSTP1 by EGFR as a novel, heretofore unrecognized component of the EGFR signaling network and a novel mechanism of tumor drug resistance, particularly in tumors with elevated GSTP1 and/or activated EGFR.

Biologically conformal treatment: biomarkers and functional imaging in radiation oncology

'Conformal radiation therapy' is the standard of care in radiation oncology, referring to the process of shaping the radiation beam to precisely match a tumor's physical dimensions. We describe 'biologically conformal radiotherapy', in which the radiation oncologist matches the prescribed treatment to a tumor's biological characteristics and the host's predicted tolerance of radiation. This paradigm emphasizes that not all tumors are equally sensitive to radiation; conversely, some patients are especially susceptible to radiation's side effects. Patients bearing radioresistant tumors or those prone to toxicity may be best treated with the incorporation of targeted radiation modulators or, in extreme cases, by a different modality. The biological characteristics of tumors can be assessed by a wide range of techniques: functional imaging (positron emission tomography and advanced magnetic resonance imaging), single gene/protein molecular techniques and 'omic' technologies. This paper reviews the latest advances in the use of biomarkers and functional imaging in guiding patients to receive the most appropriate treatment.

Phase I/II trial of erlotinib and temozolomide with radiation therapy in the treatment of newly diagnosed glioblastoma multiforme: North Central Cancer Treatment Group Study N0177

PURPOSE

Epidermal growth factor receptor (EGFR) amplification in glioblastoma multiforme (GBM) is a common occurrence and is associated with treatment resistance. Erlotinib, a selective EGFR inhibitor, was combined with temozolomide (TMZ) and radiotherapy (RT) in a phase I/II trial.

PATIENTS AND METHODS

Adults not taking enzyme-inducing anticonvulsants after resection or biopsy of GBM were treated with erlotinib (150 mg daily) until progression. Erlotinib was delivered alone for 1 week, then concurrently with TMZ (75 mg mg/m(2) daily) and RT (60 Gy), and finally, concurrently with up to six cycles of adjuvant TMZ (200 mg/m(2) daily for 5 days every 28 days). The primary end point was survival at 1 year.

RESULTS

Ninety-seven eligible patients were accrued with a median follow-up time of 22.2 months. By definition, the primary end point was successfully met with a median survival time of 15.3 months. However, there was no sign of benefit in overall survival when comparing N0177 with the RT/TMZ arm of the European Organisation for Research and Treatment of Cancer/National Cancer Institute of Canada trial 26981/22981 (recursive partitioning analysis [RPA] class III, 19 v 21 months; RPA class IV, 16 v 16 months; RPA class V, 8 v 10 months, respectively). Presence of diarrhea, rash, and EGFRvIII, p53, phosphatase and tensin homolog (PTEN), combination EGFR and PTEN, and EGFR amplification status were not predictive (P > .05) of survival.

CONCLUSION

Although the primary end point was successfully met using nitrosourea-based (pre-TMZ) chemotherapy era historic controls, there was no sign of benefit compared with TMZ era controls. Analyses of molecular subsets did not reveal cohorts of patients sensitive to erlotinib. TMZ chemotherapy combined with RT resulted in improved outcomes compared with historical controls who received nitrosourea-based chemotherapies.

Brain tumor epidemiology: consensus from the Brain Tumor Epidemiology Consortium

Epidemiologists in the Brain Tumor Epidemiology Consortium (BTEC) have prioritized areas for further research. Although many risk factors have been examined over the past several decades, there are few consistent findings, possibly because of small sample sizes in individual studies and differences between studies in patients, tumor types, and methods of classification. Individual studies generally have lacked samples of sufficient size to examine interactions. A major priority based on available evidence and technologies includes expanding research in genetics and molecular epidemiology of brain tumors. BTEC has taken an active role in promoting understudied groups, such as pediatric brain tumors; the etiology of rare glioma subtypes, such as oligodendroglioma; and meningioma, which, although it is not uncommon, has only recently been registered systematically in the United States. There also is a pressing need for more researchers, especially junior investigators, to study brain tumor epidemiology. However, relatively poor funding for brain tumor research has made it difficult to encourage careers in this area. In this report, BTEC epidemiologists reviewed the group's consensus on the current state of scientific findings, and they present a consensus on research priorities to identify which important areas the science should move to address.

Radiation-induced EGFR-signaling and control of DNA-damage repair

PURPOSE

Over the last decade evidence has accumulated indicating that cell membrane-bound growth factor receptor of the erbB family and especially the epidermal growth factor receptor EGFR (erbB1) mediates resistance of tumor cells to both chemo- and radiotherapy when mutated or overexpressed. More recently a novel link between EGFR signaling pathways and DNA repair mechanisms, especially non-homologous end joining (NHEJ) repair could be demonstrated. The following review summarizes the current knowledge on the role of EGFR and its downstream signaling pathways in the regulation of cellular radiation response and DNA repair.

CONCLUSION

The novel findings on radiation-induced EGFR-signaling and its involvement in regulating DNA-double strand break repair need further investigations of the detailed mechanisms involved. The results to be obtained may not only improve our knowledge on basic mechanisms of radiation sensitivity/resistance but also will promote translational approaches to test new strategies for clinically applicable molecular targeting.

Incorporating molecular tools into early-stage clinical trials

The author discusses the implications of a new phase I trial investigating the role of rapamycin in patients with glioblastoma.

Wilms tumor 1 expression in malignant gliomas and correlation of +KTS isoforms with p53 status

Object

The WT1 gene is overexpressed in many types of human cancer. It has been demonstrated that Wilms tumor 1 (WT1) promotes tumor cell proliferation and survival in some cell lines by inhibiting p53-mediated apoptosis; however, this relationship has not been investigated in gliomas. The goal in this study was to characterize the expression pattern of WT1 in human gliomas and to determine if a correlation exists between WT1 expression and p53 status.

Methods

The authors screened nine malignant glioma cell lines, 50 glioblastoma multiforme (GBM) samples, and 16 lower-grade glial tumors for WT1 expression.

Results

Five of nine cell lines, 44 of 50 GBM samples, and 13 of 16 lower-grade gliomas expressed WT1 mRNA on reverse transcriptase polymerase chain reaction (PCR) analysis. Expression of WT1 was not detected in normal astrocytes. Two WT1 isoforms, +/+ and −/+, were expressed in the majority of these samples. Real-time PCR analysis of the GBM cell lines revealed that the level of WT1 mRNA ranged from 6.33 to 214.70 ng per ng 18S ribosomal RNA. The authors screened the GBM samples for p53 mutation by using PCR and single-stranded conformational polymorphism analysis, and they demonstrated an association between WT1 expression and p53 status. Tumors that contained wild-type p53 were significantly more likely to express WT1 than tumors that contained mutant p53.

Conclusions

The presence of WT1 in glioma cell lines and the majority of primary tumor samples and its absence in normal astrocytes support the suggestion that WT1 expression is important in glioma biology.

Phase I Trial of Tipifarnib (R115777) Concurrent With Radiotherapy in Patients with Glioblastoma Multiforme

PURPOSE

To conduct a Phase I trial to determine the maximally tolerated dose (MTD) of tipifarnib in combination with conventional three-dimensional conformal radiotherapy (RT) for patients with glioblastoma multiforme.

METHODS AND MATERIALS

After resection or biopsy, tipifarnib was given 1 week before and then continuously during RT (60 Gy), followed by adjuvant administration until progression. The tipifarnib dose during RT was escalated in cohorts of 3 starting at 200 mg/day.

RESULTS

Thirteen patients were enrolled, and 12 were evaluable for MTD. Of these patients, 7 had undergone biopsy, 4 had partial resection, and 1 had gross total resection. No dose-limiting toxicity (DLT) was observed during the concomitant treatment at 200 mg. All 3 patients at 300 mg experienced DLT during the concomitant treatment: 1 with sudden death and 2 with acute pneumonitis. The MTD was reached at 300 mg. The adjuvant treatment was suppressed from the protocol after a case of pneumonitis during this treatment. Six additional patients were included at 200 mg/day of the new protocol, confirming the safety of this treatment. Of the 9 evaluable patients, 1 had partial response, 4 had stable disease, and 3 had rapid progression; the patient with gross total resection was relapse-free after 21 months. Median survival of the evaluable patients was 12 months (range, 5.2-21 months).

CONCLUSION

Tipifarnib (200 mg/day) concurrent with standard radiotherapy is well tolerated in patients with glioblastoma. Preliminary efficacy results are encouraging.

Novel recombinant adenoviral vector that targets the interleukin-13 receptor alpha2 chain permits effective gene transfer to malignant glioma

Transduction of malignant glioma with adenovirus serotype 5 (Ad5) vectors is limited by the low levels of coxsackievirus and adenovirus receptor (CAR) on tumor cells. However, malignant brain tumors have been found to overexpress a glioma-associated receptor, interleukin-13 receptor alpha2 chain (IL-13Ralpha2), a marker of both glial transformation and tumor grade. To selectively target Ad5 to IL-13Ralpha2, we constructed a replication-deficient adenoviral vector that possesses an IL-13 ligand presented by a T4 phage fibritin shaft, and designated the new virus LU-13. Western blot and sequence analyses confirmed proper trimerization and ligand presentation by the T4 fibritin shaft. Confocal microscopy analysis of primary glioma suspensions incubated with viral recombinants showed that LU-13 colocalized with IL-13Ralpha2. Luciferase transduction assays conducted in both primary and passaged glioma cell cultures exhibited at least 10-fold enhanced gene transduction. Moreover, the virus preferentially bound to glioma cells, as documented by increased adenoviral E4 DNA copy number. In vitro competition assays performed with anti-human IL-13 monoclonal antibody confirmed significant attenuation of LU-13 transduction. These results were further confirmed in vivo, where LU-13 showed a 300-fold increase in transgene expression. In summary, we describe here the development of a novel and targeted adenoviral vector that binds IL-13Ralpha2. Our findings confirm the ability of LU-13 to bind IL-13Ralpha2 and increase transgene expression, making it an attractive gene therapy vector for the treatment of malignant glioma in a clinical setting.

Genetic polymorphisms of the epidermal growth factor and related receptor in non-small cell lung cancer--a review of the literature

Worldwide, approximately 1.3 billion individuals are current smokers, and smoking is the second major cause of death. Currently, lung cancer is the most common type of cancer in Europe, and the third in the U.S. Until now, cytotoxic chemotherapy has had a limited impact on survival in metastatic non-small cell lung cancer (NSCLC). The central role of epidermal growth factor (EGF) and its receptor (EGFR) in lung carcinogenesis is well recognized. Genetic polymorphisms are variants in individual genomes that may be responsible for different functional molecular roles and contribute to variability in drug pharmacokinetic and pharmacodynamic processes. Herein, we review the literature on EGF and EGFR functions and activities, particularly the current role of their functional polymorphisms as related to NSCLC.

Predictive and prognostic markers in human glioblastomas

Glioblastomas (GBMs) are among the most aggressive of all known human tumors. The median survival times remain in the 12- to 15-month range despite aggressive surgery, radiation, and chemotherapy. Through molecular and genetic profiling efforts, underlying mechanisms of resistance to these therapies are becoming better understood. The present standard of care has been shaped by the recently reported phase III study by the European Organisation for Research and Treatment of Cancer and the National Cancer Institute of Canada, which found that the addition of temozolomide (TMZ) to radiation therapy significantly improved outcome compared with radiation alone. However, careful examination of these data reveals that not all GBM patients benefited from the addition of TMZ to radiation therapy. A companion correlative study found that GBM patients with tumors with MGMT promoter methylation appeared to derive the greatest benefit from the addition of TMZ to radiation therapy. Although this finding is provocative, it should be kept in mind that this study was performed retrospectively and that prospective validation is required before MGMT methylation can be used for clinical stratification purposes. However, this study does show promise for the tailoring of future treatments according to the molecular and genetic profiles of an individual's tumor rather than using the "one-glove-fits-all" approach that is currently being followed. As more effective "smart drugs" are developed, molecular and genetic profiling will assume even greater importance in this regard.

Down-regulation of Wilms’ tumor 1 expression in glioblastoma cells increases radiosensitivity independently of p53

The Wilms' tumor 1 (WT1) gene is overexpressed in human glioblastoma and correlates with wild-type p53 status. In other cell types, WT1 inhibits p53-mediated apoptosis in response to DNA damaging agents. However, neither this interaction nor the relationship between WT1 and radiosensitivity has been studied in glioblastoma. To study this interaction, we generated LN-229 glioma cell lines (p53 mutant) stably expressing WT1 isoforms and induced apoptosis by transfecting with different doses of wild-type p53 plasmid expression vector. Constitutive expression of WT1 did not protect against exogenous p53-mediated apoptosis. Likewise, WT1 expression did not protect against endogenous p53-mediated cell death induced by radiotherapy in U87MG cells, which contain functional wild-type p53. We then tested the efficacy of WT1 siRNA in inhibiting WT1 expression and its effect on radiosensitivity. In T98G and LN-18 glioma cells, which possess p53 mutations, WT1 siRNA decreased WT1 protein to almost undetectable levels by 96-h post-transfection. Furthermore, WT1 siRNA transfection caused a significantly larger decrease in viability following irradiation than was seen in untransfected cells in both cell lines after treatment with ED50 of ionizing radiation. In conclusion, WT1 overexpression did not protect against p53-mediated apoptosis or ionizing radiation induced cell death. WT1 siRNA increased the radiosensitivity of two human glioma cell lines independently of p53. Anti-WT1 strategies may, therefore, prove useful in improving the response of glioblastoma to radiotherapy, thus potentially improving patient survival.

Impact of molecular profiling on clinical trial design for glioblastoma

This review highlights the ways in which molecular and genetic profiling of malignant gliomas has led to intelligent clinical trial design. The review also highlights known resistance mechanisms to conventional therapies in malignant gliomas and potential strategies to overcome these mechanisms with the use of targeted therapy.