Expression of EGFR variant vIII promotes both radiation resistance and hypoxia tolerance

Structural insights into the role and targeting of EGFRvIII

The epidermal growth factor receptor (EGFR) is a well-known oncogenic driver in lung and other cancers. In glioblastoma multiforme (GBM), the EGFR deletion variant III (EGFRvIII) is frequently found alongside EGFR amplification. Agents targeting the EGFR axis have shown limited clinical benefits in GBM and the role of EGFRvIII in GBM is poorly understood. To shed light on the role of EGFRvIII and its potential as a therapeutic target, we determined X-ray crystal structures of a monomeric EGFRvIII extracellular region (ECR). The EGFRvIII ECR resembles the unliganded conformation of EGFR, including the orientation of the C-terminal region of domain II. Domain II is mostly disordered, but the ECR structure is compact. We selected a nanobody with preferential binding to EGFRvIII relative to EGFR and structurally defined an epitope on domain IV that is occluded in the unliganded intact EGFR. These findings suggest new avenues for EGFRvIII targeting in GBM.

Emerging Therapies for Glioblastoma

Glioblastoma is most commonly a primary brain tumor and the utmost malignant one, with a survival rate of approximately 12-18 months. Glioblastoma is highly heterogeneous, demonstrating that different types of cells from the same tumor can manifest distinct gene expression patterns and biological behaviors. Conventional therapies such as temozolomide, radiation, and surgery have limitations. As of now, there is no cure for glioblastoma. Alternative treatment methods to eradicate glioblastoma are discussed in this review, including targeted therapies to PI3K, NFKβ, JAK-STAT, CK2, WNT, NOTCH, Hedgehog, and TGFβ pathways. The highly novel application of oncolytic viruses and nanomaterials in combating glioblastoma are also discussed. Despite scores of clinical trials for glioblastoma, the prognosis remains poor. Progress in breaching the blood-brain barrier with nanomaterials and novel avenues for targeted and combination treatments hold promise for the future development of efficacious glioblastoma therapies.

Value of functional in-vivo endpoints in preclinical radiation research

BACKGROUND

Cancer research faces the problem of high rates of clinical failure of new treatment approaches after positive preclinical data. We hypothesize that a major confounding factor to this problem in radiooncology is the choice of the preclinical endpoint.

METHODS

We present a comprehensive re-evaluation of large-scale preclinical in-vivo data on fractionated irradiation alone or simultaneously with Epidermal Growth Factor Receptor inhibition. Taking the permanent local tumour control assay as a gold standard, we evaluated different tumour volume dependent endpoints that are widely used for preclinical experiments.

RESULTS

The analysis showed the highest correlations between volume related and local tumour control endpoints after irradiation alone. For combined treatments, wide inter-tumoural variations were observed with reduced correlation between the endpoints. Evaluation of growth delay per Gray (GD/Gy) based on two or more dose levels showed closest correlation with local tumour control dose 50% (TCD₅₀).

CONCLUSIONS

GD/Gy with at least two dose groups correlates with TCD₅₀, but cannot replace the latter as the goldstandard.

Chloroquine combined with concurrent radiotherapy and temozolomide for newly diagnosed glioblastoma: a phase IB trial

Treatment of glioblastoma xenografts with chloroquine results in macroautophagy/autophagy inhibition, resulting in a reduction of tumor hypoxia and sensitization to radiation. Preclinical data show that EGFRvIII-expressing glioblastoma may benefit most from chloroquine because of autophagy dependency. This study is the first to explore the safety, pharmacokinetics and maximum tolerated dose of chloroquine in combination with radiotherapy and concurrent daily temozolomide in patients with a newly diagnosed glioblastoma. This study is a single-center, open-label, dose-finding phase I trial. Patients received oral chloroquine daily starting one week before the course of chemoradiation (temozolomide 75 mg/m²/d) until the end of radiotherapy (59.4 Gy/33 fractions). Thirteen patients were included in the study (n = 6: 200 mg, n = 3: 300 mg, n = 4: 400 mg chloroquine). A total of 44 adverse events, possibly related to chloroquine, were registered including electrocardiogram QTc prolongation, irreversible blurred vision and nausea/vomiting resulting in cessation of temozolomide or delay of adjuvant cycles. The maximum tolerated dose was 200 mg chloroquine. Median overall survival was 16 months (range 2–32). Median survival was 11.5 months for EGFRvIII- patients and 20 months for EGFRvIII+ patients. A daily dose of 200 mg chloroquine was determined to be the maximum tolerated dose when combined with radiotherapy and concurrent temozolomide for newly diagnosed glioblastoma. Favorable toxicity and promising overall survival support further clinical studies.

Abbreviations: AE: adverse events; CQ: chloroquine; DLT: dose-limiting toxicities; EGFR: epidermal growth factor receptor; GBM: glioblastoma; HCQ: hydroxychloroquine; IDH1/2: isocitrate dehydrogenase (NADP(+)) 1/2; MTD: maximum tolerated dose; CTC: National Cancer Institute Common Toxicity Criteria; MGMT: O-6-methylguanine-DNA methyltransferase; OS: overall survival; po qd: per os quaque die; SAE: serious adverse events; TMZ: temozolomide; WHO: World Health Organization

EGFR: An essential receptor tyrosine kinase-regulator of cancer stem cells

The Epidermal Growth Factor Receptor (EGFR) is frequently expressed at elevated levels in different forms of cancer and expression often correlates positively with cancer progression and poor prognosis. Different mutant forms of this protein also contribute to cancer heterogeneity. A constitutively active form of EGFR, EGFRvIII is one of the most important variants. EGFR is responsible for the maintenance and functions of cancer stem cells (CSCs), including stemness, metabolism, immunomodulatory-activity, dormancy and therapy-resistance. EGFR regulates these pathways through several signaling cascades, and often cooperates with other RTKs to exert further control. Inhibitors of EGFR have been extensively studied and display some anticancer efficacy. However, CSCs can also acquire resistance to EGFR inhibitors making effective therapy even more difficult. To ameliorate this limitation of EGFR inhibitors when used as single agents, it may be of value to simultaneously combine multiple EGFR inhibitors or use EGFR inhibitors with regulators of other important cancer phenotype regulating molecules, such as STAT3, or involved in important processes such as DNA repair. These combinatorial approaches require further experimental confirmation, but if successful would expand and improve therapeutic outcomes employing EGFR inhibitors as one arm of the therapy.

EGFRvIII expression triggers a metabolic dependency and therapeutic vulnerability sensitive to autophagy inhibition

Expression of EGFRvIII is frequently observed in glioblastoma and is associated with increased cellular proliferation, enhanced tolerance to metabolic stresses, accelerated tumor growth, therapy resistance and poor prognosis. We observed that expression of EGFRvIII elevates the activation of macroautophagy/autophagy during starvation and hypoxia and explored the underlying mechanism and consequence. Autophagy was inhibited (genetically or pharmacologically) and its consequence for tolerance to metabolic stress and its therapeutic potential in (EGFRvIII+) glioblastoma was assessed in cellular systems, (patient derived) tumor xenopgrafts and glioblastoma patients. Autophagy inhibition abrogated the enhanced proliferation and survival advantage of EGFRvIII+ cells during stress conditions, decreased tumor hypoxia and delayed tumor growth in EGFRvIII+ tumors. These effects can be attributed to the supporting role of autophagy in meeting the high metabolic demand of EGFRvIII+ cells. As hypoxic tumor cells greatly contribute to therapy resistance, autophagy inhibition revokes the radioresistant phenotype of EGFRvIII+ tumors in (patient derived) xenograft tumors. In line with these findings, retrospective analysis of glioblastoma patients indicated that chloroquine treatment improves survival of all glioblastoma patients, but patients with EGFRvIII+ glioblastoma benefited most. Our findings disclose the unique autophagy dependency of EGFRvIII+ glioblastoma as a therapeutic opportunity. Chloroquine treatment may therefore be considered as an additional treatment strategy for glioblastoma patients and can reverse the worse prognosis of patients with EGFRvIII+ glioblastoma.

Internalization of titanium dioxide nanoparticles by glial cells is given at short times and is mainly mediated by actin reorganization-dependent endocytosis

Many nanoparticles (NPs) have toxic effects on multiple cell lines. This toxicity is assumed to be related to their accumulation within cells. However, the process of internalization of NPs has not yet been fully characterized. In this study, the cellular uptake, accumulation, and localization of titanium dioxide nanoparticles (TiO2 NPs) in rat (C6) and human (U373) glial cells were analyzed using time-lapse microscopy (TLM) and transmission electron microscopy (TEM). Cytochalasin D (Cyt-D) was used to evaluate whether the internalization process depends of actin reorganization. To determine whether the NP uptake is mediated by phagocytosis or macropinocytosis, nitroblue tetrazolium (NBT) reduction was measured and the 5-(N-ethyl-N-isopropyl)-amiloride was used. Expression of proteins involved with endocytosis and exocytosis such as caveolin-1 (Cav-1) and cysteine string proteins (CSPs) was also determined using flow cytometry. TiO2 NPs were taken up by both cell types, were bound to cellular membranes and were internalized at very short times after exposure (C6, 30 min; U373, 2h). During the uptake process, the formation of pseudopodia and intracellular vesicles was observed, indicating that this process was mediated by endocytosis. No specific localization of TiO2 NPs into particular organelles was found: in contrast, they were primarily localized into large vesicles in the cytoplasm. Internalization of TiO2 NPs was strongly inhibited by Cyt-D in both cells and by amiloride in U373 cells; besides, the observed endocytosis was not associated with NBT reduction in either cell type, indicating that macropinocytosis is the main process of internalization in U373 cells. In addition, increases in the expression of Cav-1 protein and CSPs were observed. In conclusion, glial cells are able to internalize TiO2 NPs by a constitutive endocytic mechanism which may be associated with their strong cytotoxic effect in these cells; therefore, TiO2 NPs internalization and their accumulation in brain cells could be dangerous to human health.

Current strategies for targeted delivery of bio-active drug molecules in the treatment of brain tumor

Brain tumor is one of the most challenging diseases to treat. The major obstacle in the specific drug delivery to brain is blood-brain barrier (BBB). Mostly available anti-cancer drugs are large hydrophobic molecules which have limited permeability via BBB. Therefore, it is clear that the protective barriers confining the passage of the foreign particles into the brain are the main impediment for the brain drug delivery. Hence, the major challenge in drug development and delivery for the neurological diseases is to design non-invasive nanocarrier systems that can assist controlled and targeted drug delivery to the specific regions of the brain. In this review article, our major focus to treat brain tumor by study numerous strategies includes intracerebral implants, BBB disruption, intraventricular infusion, convection-enhanced delivery, intra-arterial drug delivery, intrathecal drug delivery, injection, catheters, pumps, microdialysis, RNA interference, antisense therapy, gene therapy, monoclonal/cationic antibodies conjugate, endogenous transporters, lipophilic analogues, prodrugs, efflux transporters, direct conjugation of antitumor drugs, direct targeting of liposomes, nanoparticles, solid-lipid nanoparticles, polymeric micelles, dendrimers and albumin-based drug carriers.

Optical imaging of targeted β-galactosidase in brain tumors to detect EGFR levels

A current limitation in molecular imaging is that it often requires genetic manipulation of cancer cells for noninvasive imaging. Other methods to detect tumor cells in vivo using exogenously delivered and functionally active reporters, such as β-gal, are required. We report the development of a platform system for linking β-gal to any number of different ligands or antibodies for in vivo targeting to tissue or cells, without the requirement for genetic engineering of the target cells prior to imaging. Our studies demonstrate significant uptake in vitro and in vivo of an EGFR-targeted β-gal complex. We were then able to image orthotopic brain tumor accumulation and localization of the targeted enzyme when a fluorophore was added to the complex, as well as validate the internalization of the intravenously administered β-gal reporter complex ex vivo. After fluorescence imaging localized the β-gal complexes to the brain tumor, we topically applied a bioluminescent β-gal substrate to serial sections of the brain to evaluate the delivery and integrity of the enzyme. Finally, robust bioluminescence of the EGFR-targeted β-gal complex was captured within the tumor during noninvasive in vivo imaging.

Tumor-derived TGF-β and prostaglandin E2 attenuate anti-tumor immune responses in head and neck squamous cell carcinoma treated with EGFR inhibitor

BACKGROUND

EGFR-targeted therapy is an attractive option for head and neck squamous cell carcinoma patients. We have recently reported the use of EGFR inhibitors as an adjunct treatment to enhance HLA-DR expression in tumor cells to improve cancer immunotherapy. Nevertheless, we observed that EGFR inhibitors resulted in decreased anti-tumor responses, regardless of upregulation of HLA-DR expression on the tumor cell. In this study, we specifically investigated the mechanisms by which EGFR inhibition modulated anti-tumor responses.

METHODS

An EGFR inhibitor erlotinib was used to assess the modulation of anti-tumor responses by tumor antigen-specific helper T cells. We then examined whether administration of the EGFR inhibitor altered tumor cytokine profiles and expression of immune-related molecules on tumor cells.

RESULTS

Despite the augmented HLA-DR expression on a gingival cancer cell line by EGFR inhibition, anti-tumor responses of EGFR reactive helper T cell clones against tumor cells were decreased. EGFR inhibition did not change the expression of CD80, CD86, or PD-L1 on the tumor cells. Conversely, production of transforming growth factor beta (TGF-β) and prostaglandin E2 was increased by EGFR inhibition, indicating that these immunosuppressive molecules were involved in diminishing tumor recognition by T cells. Significantly, attenuation of HTL responses against tumors after EGFR inhibition was reversed by the addition of anti-TGF-β antibody or COX2 inhibitors.

CONCLUSIONS

Targeting TGF-β and prostaglandin E2 may allow for improved outcomes for cancer patients treated with combination immunotherapy and EGFR inhibitors.

Tumor-derived TGF-β and prostaglandin E2 attenuate anti-tumor immune responses in head and neck squamous cell carcinoma treated with EGFR inhibitor

BACKGROUND

EGFR-targeted therapy is an attractive option for head and neck squamous cell carcinoma patients. We have recently reported the use of EGFR inhibitors as an adjunct treatment to enhance HLA-DR expression in tumor cells to improve cancer immunotherapy. Nevertheless, we observed that EGFR inhibitors resulted in decreased anti-tumor responses, regardless of upregulation of HLA-DR expression on the tumor cell. In this study, we specifically investigated the mechanisms by which EGFR inhibition modulated anti-tumor responses.

METHODS

An EGFR inhibitor erlotinib was used to assess the modulation of anti-tumor responses by tumor antigen-specific helper T cells. We then examined whether administration of the EGFR inhibitor altered tumor cytokine profiles and expression of immune-related molecules on tumor cells.

RESULTS

Despite the augmented HLA-DR expression on a gingival cancer cell line by EGFR inhibition, anti-tumor responses of EGFR reactive helper T cell clones against tumor cells were decreased. EGFR inhibition did not change the expression of CD80, CD86, or PD-L1 on the tumor cells. Conversely, production of transforming growth factor beta (TGF-β) and prostaglandin E2 was increased by EGFR inhibition, indicating that these immunosuppressive molecules were involved in diminishing tumor recognition by T cells. Significantly, attenuation of HTL responses against tumors after EGFR inhibition was reversed by the addition of anti-TGF-β antibody or COX2 inhibitors.

CONCLUSIONS

Targeting TGF-β and prostaglandin E2 may allow for improved outcomes for cancer patients treated with combination immunotherapy and EGFR inhibitors.

EGFR signaling and autophagy dependence for growth, survival, and therapy resistance

The epidermal growth factor receptor (EGFR) is amplified or mutated in various human epithelial tumors. Its expression and activation leads to cell proliferation, differentiation, and survival. Consistently, EGFR amplification or expression of EGFR variant 3 (EGFRvIII) is associated with resistance to conventional cancer therapy through activation of pro-survival signaling and DNA-repair mechanisms. EGFR targeting has successfully been exploited as strategy to increase treatment efficacy. Nevertheless, these targeting strategies have only been proven effective in a limited percentage of human tumors. Recent knowledge indicates that EGFR deregulated tumors display differences in autophagy and dependence on autophagy for growth and survival and the use of autophagy to increase resistance to EGFR-targeting drugs. In this review the dependency on autophagy and its role in mediating resistance to EGFR-targeting agents will be discussed. Considering the current knowledge, autophagy inhibition could provide a novel strategy to enhance therapy efficacy in treatment of EGFR deregulated tumors.

High NOTCH activity induces radiation resistance in non small cell lung cancer

BACKGROUND AND PURPOSE

Patients with advanced NSCLC have survival rates <15%. The NOTCH pathway plays an important role during lung development and physiology but is often deregulated in lung cancer, making it a potential therapeutic target. We investigated NOTCH signaling in NSCLC and hypothesized that high NOTCH activity contributes to radiation resistance.

MATERIALS AND METHODS

NOTCH signaling in NSCLC patient samples was investigated using quantitative RT-PCR. H460 NSCLC cells with either high or blocked NOTCH activity were generated and their radiation sensitivity monitored using clonogenic assays. In vivo, xenograft tumors were irradiated and response assessed using growth delay. Microenvironmental parameters were analyzed by immunohistochemistry.

RESULTS

Patients with high NOTCH activity in tumors showed significantly worse disease-free survival. In vitro, NOTCH activity did not affect the proliferation or intrinsic radiosensitivity of NSCLC cells. In contrast, xenografts with blocked NOTCH activity grew slower than wild type tumors. Tumors with high NOTCH activity grew significantly faster, were more hypoxic and showed a radioresistant phenotype.

CONCLUSIONS

We demonstrate an important role for NOTCH in tumor growth and correlate high NOTCH activity with poor prognosis and radioresistance. Blocking NOTCH activity in NSCLC might be a promising intervention to improve outcome after radiotherapy.

A minority subpopulation of CD133(+) /EGFRvIII(+) /EGFR(-) cells acquires stemness and contributes to gefitinib resistance

AIMS

To study the contribution of epidermal growth factor receptor variant III (EGFRvIII) to glioblastoma multiforme (GBM) stemness and gefitinib resistance.

METHODS

CD133(+) and CD133(-) cells were separated from EGFRvIII(+) clinical specimens of three patients with newly diagnosed GBM. Then, RT-PCR was performed to evaluate EGFRvIII and EGFR expression in CD133(+) and CD133(-) cells. The tumorigenicity and stemness of CD133(+) cells was verified by intracranial implantation of 5 × 10(3) cells into immunodeficient NOD/SCID mice. Finally, cells were evaluated for their sensitivity to EGFR tyrosine kinase inhibition by gefitinib.

RESULTS

RT-PCR results showed that the sorted CD133(+) cells expressed EGFRvIII exclusively, while the CD133(-) cells expressed both EGFRvIII and EGFR. At 6-8 weeks postimplantation, CD133(+) /EGFRvIII(+) /EGFR(-) cells formed intracranial tumors. Cell counting kit-8 results showed that the IC50 values of the three isolated EGFRvIII(+) cell lines treated with gefitinib were 14.44, 16.00, and 14.66 μM, respectively, whereas the IC50 value of an isolated EGFRvIII(-) cell line was 8.57 μM.

CONCLUSIONS

EGFRvIII contributes to the stemness of cancer stem cells through coexpression with CD133 in GBMs. Furthermore, CD133(+) /EGFRvIII(+) /EGFR(-) cells have the ability to initiate tumor formation and may contribute to gefitinib resistance.

Predictive value of hypoxia, proliferation and tyrosine kinase receptors for EGFR-inhibition and radiotherapy sensitivity in head and neck cancer models

BACKGROUND AND PURPOSE

EGFR-inhibitor Cetuximab (C225) improves the efficacy of radiotherapy in only a subgroup of HNSCC patients. Identification of predictive tumor characteristics is essential to improve patient selection.

MATERIAL AND METHODS

Response to C225 and/or radiotherapy was assessed with tumor growth delay assays in 4 HNSCC xenograft models with varying EGFR-expression levels. Hypoxia and proliferation were quantified with immunohistochemistry and the expression of proteins involved in C225-resistance with Western blot.

RESULTS

EGFR-expression did not predict response to C225 and/or radiotherapy. Reduction of hypoxia by C225 was only observed in SCCNij202, which was highly sensitive to C225. Proliferation changes correlated with response to C225 and C225 combined with radiotherapy, as proliferation decreased after C225 treatment in C225-sensitive SCCNij202 and after combined treatment in SCCNij185, which showed a synergistic effect to combined C225-radiotherapy. Furthermore, C225-resistant SCCNij153 tumors expressed high levels of (activated) HER3 and MET.

CONCLUSIONS

EGFR-expression is needed for C225-response, but is not sufficient to predict response to C225 with or without radiotherapy. However, basal expression of additional growth factor receptors and effects on proliferation, but not hypoxia, correlated with response to combined C225-radiotherapy treatment and are potential clinically relevant predictive biomarkers.

Differences in molecular genetics between pediatric and adult malignant astrocytomas: age matters

The microscope - the classical tool for the investigation of cells and tissues - remains the basis for the classification of tumors throughout the body. Nowhere has this been more true than in the grading of astrocytomas. In spite of the fact that our parents warned us not to judge a book by its cover, we have continued to assume that adult and pediatric malignant gliomas that look the same, will have the same mutations, and thus respond to the same therapy. Rapid advances in molecular biology have permitted us the opportunity to go inside the cell and characterize the genetic events that underlie the true molecular heterogeneity of adult and pediatric brain tumors. In this paper, we will discuss some of the important clinical differences between pediatric and adult gliomas, with a focus on the molecular analysis of these different age groups.

[EGFR-dependent impact of indol-3-carbinol on radiosensitivity of lung cancer cells]

背景与目的

吲哚-3-甲醇（indole-3-carbinol, I3C）是十字花科蔬菜中一种主要的有效植物化学物质，且具有防癌和抗癌作用。本研究旨在观察I3C是否影响表皮生长因子受体（epidermal growth factor receptor, EGFR）表达水平不同的肺癌细胞放射敏感性。

方法

采用MTT和克隆形成实验方法分别检测肺癌细胞的生长和存活率；siRNA转染方法降低细胞中EGFR蛋白表达水平；Western blot和RT-PCR法分别测定EGFR蛋白和mRNA的表达。

结果

采用无明显毒副作用的5 μmol/L剂量的I3C预处理明显降低了EGFR表达阳性的人肺腺癌H1975和人肺鳞癌H226细胞对γ-射线照射的放射敏感性，而I3C对EGFR表达阴性的人肺鳞癌NIH-H520细胞的放射敏感性则影响非常小。Western blot结果显示I3C可以增加H1975和H226细胞中EGFR蛋白的表达水平和Y845位点磷酸化水平。EGFR siRNA降低了NIH-H1975细胞中EGFR蛋白的表达，增加了细胞的放射敏感性，并有效地降低和抑制了I3C导致的细胞耐辐射效应。

结论

我们的研究结果首次证实I3C可以通过调节EGFR表达和磷酸化水平从而影响肺癌细胞的放射治疗敏感性，提示EGFR可能是I3C影响肺癌放射治疗敏感性的重要靶蛋白。

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.

Glioblastoma stem-like cell lines with either maintenance or loss of high-level EGFR amplification, generated via modulation of ligand concentration

PURPOSE

Despite the high incidence of epidermal growth factor receptor (EGFR) gene amplification and rearrangement in glioblastomas, no suitable cell line exists that preserves these alterations in vitro and is tumorigenic in immunocompromised mice. On the basis of previous observations that glioblastoma cells cultured with serum lose the EGFR amplification rapidly and that EGF can inhibit the growth of EGFR-amplified tumor cells, we hypothesized that serum-free and EGF-free culture conditions could promote maintenance of the EGFR amplification.

EXPERIMENTAL DESIGN

Cells from EGFR-amplified glioblastomas were taken into culture using neural stem cell conditions with modifications, including varying oxygen concentrations and omission of routine EGF supplementation.

RESULTS

High-level EGFR amplification was rapidly lost in 5 glioblastoma cultures supplemented with EGF, whereas it was preserved in cultures from the same tumors established without EGF. Cultures from 2 glioblastomas developed into pairs of cell lines, with either stable maintenance or irreversible loss of high-level EGFR amplification in the majority of cells. One EGFR-amplified cell line preserved expression of the receptor variant EGFRvIII. Cell lines with high-level EGFR amplification/EGFRvIII expression formed highly aggressive tumors in nude mice, whereas nonamplified cell lines were either nontumorigenic or grew significantly more slowly. In contrast, nonamplified cell lines proliferated faster in vitro. All cell lines responded to erlotinib, with inhibition of receptor activation and proliferation but partly different effects on downstream signaling and migration.

CONCLUSIONS

Isogenic glioblastoma cell lines maintaining stable differences in EGFR/EGFRvIII status can be derived by varying exposure to EGF ligand and reflect the intratumoral genetic heterogeneity.

Role of molecular markers in the management of head and neck cancers

PURPOSE OF REVIEW

Head and neck squamous cell carcinoma (HNSCC) is the fifth most common cancer worldwide. Despite advances in treatment, the prognosis remains poor. HNSCC comprise a wide spectrum of neoplasms with different tumor biologies, prognosis and response to therapies. Current tumor classification is based on morphology and anatomic distribution, which leads to a homogeneous treatment for different diseases. Moreover, traditional diagnostic methods such as clinical assessment, histopathological examination, and imaging techniques are limited in their capacity to provide information on prognosis and decision making.

RECENT FINDINGS

Molecular markers have increased the understanding of the pathogenesis of head and neck cancer because they give increasing insight into tumor biology, prognosis, and response to therapy. The practical application of these discoveries is beginning to assist greatly in the evaluation and treatment of HNSCC to achieve a more personalized and effective approach.

SUMMARY

This article focuses on the molecular markers that have already been extensively studied such as epidermal growth factor receptor and human papillomavirus as well as those that offer potential for personalized therapy such as HIF-1 and ERCC-1. The ideal biomarker should be assayed accurately and easily, highly specific, and cost effective. Thus, a validation is required before their implementation into clinical guidelines.

Pathway profiling and rational trial design for studies in advanced stage cervical carcinoma: a review and a perspective

Multiple genetic abnormalities will have occurred in advanced cervical cancer and multiple targeting is likely to be needed to control tumor growth. To date, dominant therapeutic targets under scrutiny for cervical cancer treatment have been EGFR pathway and angiogenesis inhibition as well as anti-HPV vaccines. The potentially most effective targets to be blocked may be downstream from the membrane receptor or at the level of the nucleus. Alterations of the pathways involved in DNA repair and in checkpoint activations, as well as the specific site of HPV genome integration, appear worth assessing. For genetic mutational analysis, complete exon sequencing may become the norm in the future but at this stage frequent mutations (that matter) can be verified by PCR analysis. A precise documentation of relevant alterations of a large spectrum of protein biomarkers can be carried out by reverse phase protein array (RPPA) or by multiplex analysis. Clinical decision-making on the drug(s) of choice as a function of the biological alteration will need input from bio-informatics platforms as well as novel statistical designs. Endpoints are yet to be defined such as the loss (or reappearance) of a predictive biomarker. Single or dual targeting needs to be explored first in relevant preclinical animal and in xenograft models prior to clinical deployment.

E-Cadherin loss associated with EMT promotes radioresistance in human tumor cells

BACKGROUND AND PURPOSE

Hypoxia is a hallmark of solid cancers and associated with metastases and treatment failure. During tumor progression epithelial cells often acquire mesenchymal features, a phenomenon known as epithelial-to-mesenchymal transition (EMT). Intratumoral hypoxia has been linked to EMT induction. We hypothesized that signals from the tumor microenvironment such as growth factors and tumor oxygenation collaborate to promote EMT and thereby contribute to radioresistance.

MATERIALS AND METHODS

Gene expression changes under hypoxia were analyzed using microarray and validated by qRT-PCR. Conversion of epithelial phenotype upon hypoxic exposure, TGFβ addition or oncogene activation was investigated by Western blot and immunofluorescence. Cell survival following ionizing radiation was assayed using clonogenic survival.

RESULTS

Upon hypoxia, TGFβ addition or EGFRvIII expression, MCF7, A549 and NMuMG epithelial cells acquired a spindle shape and lost cell-cell contacts. Expression of epithelial markers such as E-cadherin decreased, whereas mesenchymal markers such as vimentin and N-cadherin increased. Combining hypoxia with TGFβ or EGFRvIII expression, lead to more rapid and pronounced EMT-like phenotype. Interestingly, E-cadherin expression and the mesenchymal appearance were reversible upon reoxygenation. Mesenchymal conversion and E-cadherin loss were associated with radioresistance.

CONCLUSIONS

Our findings describe a mechanism by which the tumor microenvironment may contribute to tumor radioresistance via E-cadherin loss and EMT.

Expression of amphiregulin and EGFRvIII affect outcome of patients with squamous cell carcinoma of the head and neck receiving cetuximab-docetaxel treatment

PURPOSE

Constitutive activation of epidermal growth factor receptor (EGFR) as a result of gene amplification, mutation, or overexpression of its ligands has been associated with response to EGFR targeting strategies. The role of these molecular mechanisms for the responsiveness of squamous cell carcinoma of the head and neck (SCCHN) to cetuximab-containing regimens remains unknown.

EXPERIMENTAL DESIGN

Tumor biopsies from 47 patients, enrolled in a single-arm phase II multicenter study for second-line treatment of recurrent or metastatic SCCHN with cetuximab and docetaxel, were analyzed by immunohistochemistry for expression of EGFR, its deletion variant III (EGFRvIII) and its ligand amphiregulin (AREG). The relation between expression levels and disease control rate (DCR) was evaluated by logistic regression. Association between expression levels, progression-free survival (PFS), and overall survival (OS) was determined by Kaplan-Meier analysis, log-rank test, and uni- and multivariate Cox regression analysis.

RESULTS

High expression of EGFR, EGFRvIII, and AREG was detected in 73%, 17%, and 45% of SCCHN cases, respectively. Expression levels of EGFR had no impact on PFS or OS. High expression levels of EGFRvIII were significantly associated with reduced DCR and shortened PFS (HR: 3.3, P = 0.005) but not with OS. Patients with high AREG expression in tumor cells had significantly shortened OS (HR: 2.2, P = 0.002) and PFS (HR 2.2, P = 0.019) compared with patients with low expression score. Multivariate Cox analysis revealed an independent association of AREG and EGFRvIII with PFS but only AREG was an independent prognosticator of OS.

CONCLUSIONS

High EGFRvIII and AREG expression levels identify SCCHN patients who are less likely to benefit from combination treatment with cetuximab and docetaxel.

CXCR4 suppression attenuates EGFRvIII-mediated invasion and induces p38 MAPK-dependent protein trafficking and degradation of EGFRvIII in breast cancer cells

Our previous report has shown that the constitutively activated EGFR variant, EGFRvIII, up-regulates the pro-metastatic chemokine receptor CXCR4 in breast cancer cells. Here we evaluated the biological effect and cell signaling effects of silencing CXCR4 expression in EGFRvIII-expressing breast cancer cells. Short hairpin RNA (shRNA)-mediated suppression of CXCR4 expression significantly reduced the invasive potential and proliferation of EGFRvIII-expressing breast cancer cells. These cells exhibited a reduction of EGFRvIII activity and protein expression due to increased protein degradation and altered protein trafficking. In conclusion, suppression of CXCR4 inhibits EGFRvIII-mediated breast cancer cell invasion and proliferation.

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.

MAb 806 enhances the efficacy of ionizing radiation in glioma xenografts expressing the de2-7 epidermal growth factor receptor

PURPOSE

Mutations of the epidermal growth factor receptor (EGFR) are common in glioma. The most frequent mutation, de2-7 EGFR/EGFRvIII, occurs in approximately 40% of high-grade gliomas and confers resistance to ionizing radiation (IR). We have previously shown that mAb 806, a novel EGFR-specific antibody, is able to inhibit the growth of U87MG.Δ2-7 glioma xenografts expressing the de2-7 EGFR and may have potential as a therapeutic.

METHODS AND MATERIALS

Nude mice bearing U87MG.Δ2-7 xenografts were treated with mAb 806 and/or IR. Comparison of tumor volumes, the effect of treatment on angiogenesis as determined by mean vessel density, and expression changes in prosurvival protein pAkt between treatment groups were undertaken.

RESULTS

Treatment of mice bearing U87MG.Δ2-7 xenografts with mAb 806 and IR resulted in schedule-dependent radiosensitization. Maximal benefit was obtained when antibody treatment was given before irradiation, with the greatest inhibition of both tumor angiogenesis and tumor growth. Combination treatment mediated radiosensitization by selectively blocking the phosphorylation of the prosurvival protein Akt at serine 473, a process that is independent of DNA-dependent protein kinase catalytic subunit.

CONCLUSIONS

Our results provide a rationale for the use of mAb 806 in combination with IR for the treatment of glioma and potentially other solid tumors bearing the de2-7 EGFR.

Epidermal growth factor receptor variant III mediates head and neck cancer cell invasion via STAT3 activation

Epidermal Growth Factor Receptor (EGFR) is frequently over-expressed in head and neck squamous cell carcinoma (HNSCC) where aberrant signaling downstream of this receptor contributes to tumor growth. EGFR variant III (EGFRvIII) is the most commonly altered form of EGFR and contains a truncated ligand-binding domain. We previously reported that EGFRvIII is expressed in up to 40% of HNSCC tumors where it is associated with increased proliferation, tumor growth and chemoresistance to anti-tumor drugs including the EGFR targeting monoclonal antibody cetuximab. Cetuximab was FDA-approved in 2006 for HNSCC but has not been shown to prevent invasion or metastasis. The present study was undertaken to evaluate the mechanisms of EGFRvIII-mediated cell motility and invasion in HNSCC. We found that EGFRvIII induced HNSCC cell migration and invasion in conjunction with increased STAT3 activation, which was not abrogated by cetuximab treatment. Further investigation demonstrated that EGF-induced expression of the STAT3 target gene HIF1-α, was abolished by cetuximab in HNSCC cells expressing wild-type EGFR under hypoxic conditions, but not in EGFRvIII-expressing HNSCC cells. These results suggest that EGFRvIII mediates HNSCC cell migration and invasion via increased STAT3 activation and induction of HIF1-α, which contribute to cetuximab resistance in EGFRvIII-expressing HNSCC tumors.

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.

Binding of cetuximab to the EGFRvIII deletion mutant and its biological consequences in malignant glioma cells

BACKGROUND AND PURPOSE

Despite the clinical use of cetuximab, a chimeric antibody against EGFR, little is known regarding its interaction with EGFRvIII, a frequently expressed deletion mutant of EGFR. Therefore, we investigated the interaction and the functional consequences of cetuximab treatment on glioma cells stably expressing EGFRvIII.

MATERIALS AND METHODS

The human glioma cell line U373 genetically modified to express EGFRvIII was used to measure the binding of cetuximab and its internalization using flow cytometry and confocal microscopy. Proliferation and cell survival were analyzed by cell growth and clonogenic survival assays.

RESULTS

Cetuximab is able to bind to EGFRvIII and causes an internalization of the receptor and decreases its expression levels. Furthermore, in contrast to EGF, cetuximab was able to activate EGFRvIII which was evidenced by multiple phosphorylation sites and its downstream signaling targets. Despite this activation, the growth rate and the radiosensitivity of the EGFRvIII-expressing glioma cells were not modulated.

CONCLUSIONS

Cetuximab binds to EGFRvIII and leads to the initial activation, internalization and subsequent downregulation of EGFRvIII, but it does not seem to modulate the proliferation or radiosensitivity of EGFRvIII-expressing glioma cells. Thus, approaches to treat EGFRvIII-expressing glioma cells should be evaluated more carefully.

The deletion mutant EGFRvIII significantly contributes to stress resistance typical for the tumour microenvironment

BACKGROUND AND PURPOSE

The epidermal growth factor receptor (EGFR) is overexpressed or mutated in many tumour types. The truncated, constitutively active EGFRvIII variant has not been detected in normal tissues but is found in many malignancies. In the current study, we have investigated the hypothesis that EGFRvIII contributes to a growth and survival advantage under tumour microenvironment-related stress conditions.

MATERIALS AND METHODS

U373MG doxycycline-regulated isogenic cells expressing EGFRwt or EGFRvIII were created and validated using Western blot, FACS and qRT-PCR. In vitro proliferation was evaluated with standard growth assays. Cell survival was assayed using clonogenic survival. Animal experiments were performed using NMRI-nu-xenografted mice.

RESULTS

Inducible isogenic cell lines were created and showed high induction of EGFRwt and EGFRvIII upon doxycycline addition. Overexpression of EGFRvIII but not of EGFRwt in this model resulted in a growth and survival advantage upon different tumour microenvironment-related stress conditions in vitro. Induction of EGFRvIII increased tumour growth in vivo, which was reversible upon loss of expression.

CONCLUSIONS

Under conditions where nutrients are limited and stress is apparent, as in the tumour microenvironment, expression of EGFRvIII leads to a growth and survival advantage. These data indicate a potential selection of EGFRvIII-expressing tumour cells under such stress conditions.

2-Methoxyestradiol-induced radiosensitization is independent of SOD but depends on inhibition of Akt and DNA-PKcs activities

BACKGROUND AND PURPOSE

2-Methoxyestradiol (2-ME) is described as an inhibitor of the superoxide dismutase (SOD) enzyme activity. However, it attenuates PI3K/Akt pathway and induces radiosensitization in human tumor cells as well. Since the activation of catalytic subunit of DNA-protein kinase (DNA-PKcs) is partially regulated by Akt activity, in the present study we investigated whether 2-ME-induced radiosensitization is dependent on inhibition of Akt and DNA-PKcs activities or on SOD targeting.

MATERIALS AND METHODS

This study was performed using the lung carcinoma cell line A549. Ionizing radiation-induced SOD activity was analyzed by superoxide dismutase activity assay. Applying Western blotting, the pattern of radiation-induced SOD expression and activation of Akt as well as DNA-PKcs was analyzed. Colony formation assay and gammaH2AX foci assay were performed to measure radiosensitization and DNA-double strand break (DNA-DSB) repair. To downregulate SOD expression small interfering RNA (siRNA) was used.

RESULTS

Irradiation with 4Gy stimulated SOD enzyme activity as early as 1min after radiation exposure. Expression of Cu/Zn-SOD (SOD1) as well as Mn-SOD (SOD2) was increased by single doses of 1-4Gy within 24-36h. 2-ME blocked radiation-induced SOD enzyme activity but not protein expression and enhanced radiation sensitivity. Pretreatment with 2-ME blocked IR-induced Akt as well as DNA-PKcs phosphorylation and impaired the repair of DNA-DSB. SiRNA targeting of SOD1 and SOD2 affected neither DNA-PKcs phosphorylation nor post-irradiation survival while inhibition of Akt by specific inhibitor abrogated 2-ME-induced radiosensitization.

CONCLUSION

These results may indicate that 2-ME-induced radiosensitization is independent of SOD inhibition but mainly depends on inhibition of Akt and DNA-PKcs activities.

Epidermal growth factor receptor-targeted therapy

High epidermal growth factor receptor (EGFR) expression is a feature of human tumours and is an adverse prognostic factor for radiotherapy outcome. High expression is associated with benefit from accelerated radiotherapy in patients with head and neck squamous cell carcinoma. Anti-EGFR strategies potentiate the effects of radiotherapy and the inhibition of deoxyribonucleic acid repair appears to be important amongst a wide range of mechanisms, which include effects on angiogenesis, differentiation and the immunological response. There is considerable interest in exploring combined modality therapies involving radiation and EGFR antagonists for the curative treatment of cancer patients. Important issues in designing new trials are to investigate optimal scheduling and to establish biobanks to develop biomarkers for future patient selection.