P11.32.A EGFR expression and non-methylated MGMT predict distant recurrence in glioblastoma patients treated with standard therapy

Background

Infiltrative growth within the central nervous system is hallmark of glioblastoma (GBM) at time of diagnosis. Targeting infiltrative glioma cells by adding chemotherapy to local treatment (surgical resection and radiotherapy) has led to improved tumor control and survival. Still, infiltrative growth is a major factor in therapeutic failure and tumor recurrence is almost inevitable. Herein, we hypothesize that distant recurrence represents a more migratory phenotype and that biomarkers associated with distant recurrence can be used to personalize the treatment. The aim of this study was to identify clinical and molecular factors associated with distance recurrence in glioblastoma patients treated with standard therapy.

Material and Methods

A prospective cohort of consecutive, non-selected GBM patients administered standard therapy as primary treatment between 2005-2020 at Rigshospitalet, Copenhagen, Denmark. Distant recurrence was defined as a new contrast-enhancing tumor lesion outside the radiation field (> 2 cm from the gross tumor volume). Clinical and molecular factors were screened for association with time to distant recurrence (p < 0.30) using univariate analysis. The final model was generated employing multivariate Cox regression analysis to model the association with time to distant recurrence. It was chosen to maintain known prognostic factors in the model and subsequently add significantly associated factors (p < 0.05). Competing risk adjusted analysis were performed with death as a competing risk.

Results

A total of 897 patients were included and at a median follow-up time of 73 (range: 12-198) months, 733 patients were evaluable for recurrence pattern. Out of 733 patients, 146 patients (20%) had distant recurrence. Median time to tumor progression was 7.0 months for patients with a local recurrence and 8.0 months for those with a distant recurrence (p=0.31). The following prognostic factors were not associated with distant recurrence by multivariate analysis: Corticosteroid use (p=0.84), age (p=0.20), multifocal disease (p=0.81), ECOG performance status (p=0.99) and degree of tumor resection (p=0.20). In multivariate analysis, factors independently associated with a higher likelihood of distant recurrence were: Non-methylated promoter of the MGMT gene (HR=1.93; 95% CI: 1.27-2.95; p=0.002) and positive expression of Epidermal Growth Factor Receptor (EGFR) by immunohistochemistry (HR=3.70; 95% CI: 1.61-8.33; p=0.002).

Conclusion

Non-methylated MGMT and positive expression of EGFR were independently associated with a higher likelihood of distant recurrence in GBM patients treated with standard-of-care. These factors, if validated, can be used for risk stratification and to enrich clinical treatment protocols aiming at improved local or distant tumor control.

P06.01.A Deconvolution of immunotherapy-treated glioblastoma identifies cellular heterogeneity and plasticity at the single-cell level

Background

Glioblastoma is the most aggressive cancer originating in the brain with an average survival of 15 months. One of the characteristics of glioblastoma is the high level of intra-tumour heterogeneity (ITH), but the composition and complexity at the single-cell level is poorly understood. Here, we aimed to assess the effects and consequences of immune checkpoint inhibitor (ICI) on the cellular and molecular heterogeneity of glioblastoma tumours using at the single cell level.

Material and Methods

In collaboration with the phase I trials unit at Rigshospitalet, we performed paired molecular analysis of glioma cells from primary and relapse surgery after ICI treatment. Samples were analysed using single-cell RNA sequencing (scRNA-seq) as well as bulk RNA sequencing and whole exome DNA sequencing.

Results

In an effort to trace cellular lineages we developed and refined methods to a identify copy number changes using scRNA-seq. To this end, we identified clonal and subclonal tumour cell populations in each sample. We found high levels of ITH prior to treatment, both with respect to the glioblastoma subtype enrichment and the cell type-specific gene expression. Using expression-based cell-type classification, we found defined recurrent cell-type populations present at both surgery time points. The immune checkpoint treatment had consequences on the cellular phenotypes and proportions of tumour cells, suggesting a level of plasticity in the neoplastic cells. Moreover, we identified examples of clonal dynamics and sweeps following ICI treatment, pointing to potential treatment response and resistance in these population.

Conclusion

In summary, we pursued single cell-focused analysis of ICI treated glioblastoma patients to study the cellular and molecular heterogeneity within and between glioblastoma patients, which pointed to recurrent patterns of cellular responses following ICI treatment.

P11.02.A Gliotarget: a Danish nationwide phase I/II platform trial focusing on individualized targeted treatment for newly diagnosed glioblastoma patients based on genomic profiling

INTRODUCTION

The survival in glioblastoma has been unchanged since 2005. The introduction of targeted treatments, which have improved survival in several cancers has yet to influence the treatment of glioblastoma. In Gliotarget, we will individualize the targeted treatment, and give it in the primary setting alongside standard therapy with the intention to improve the likelihood of effect.

METHODS

Gliotarget is a biomarker enriched phase I/II platform trial with initially 4 predefined biomarker selected arms and one control arm. All patients receive standard therapy with concomitant radiochemotherapy and adjuvant temozolomide. The experimental treatment is given alongside the adjuvant temozolomide. Molecular analysis, including Whole Genome Sequencing, is performed on all patients, to identify actionable biomarkers. Gliotarget includes newly diagnosed IDH-wt glioblastoma patients. In addition, to exclude the patients where the inherent poor prognosis might conceal the drug efficacy, the patients must have a 50% probability of being alive 12 months after initial surgery, according to a prognostic model developed in our institution. The sample size is calculated with Simon’s two-stage design using treatment effect at 9-months progression free survival (PFS9). We anticipate 9 patients for stage one and 24 in total, for each arm. Treatment effect is defined as 65% of the patients in an experimental arm reaching PFS9. For the survival analysis, supplementing the control arm data with leveraged external controls taken from our prospectively registered database will decrease the probability of false positive results.

CONCLUSION

Gliotarget complements the field of ongoing platform trials with its distinctive trial design. The chosen biomarkers and treatments will be presented at the 2022 EANO meeting. Enrollment is set to open in Q4 2022.

Genomic profiling of newly diagnosed glioblastoma patients and its potential for clinical utility - a prospective, translational study

Glioblastoma (GBM) is an incurable brain tumor for which new treatment strategies are urgently needed. Next-generation sequencing of GBM has most often been performed retrospectively and on archival tissue from both diagnostic and relapse surgeries with limited knowledge of clinical information, including treatment given. We sought to investigate the genomic composition prospectively in treatment-naïve patients, searched for possible targetable aberrations, and investigated for prognostic and/or predictive factors. A total of 108 newly diagnosed GBM patients were included. Clinical information, progression-free survival, and overall survival (OS) were noted. Tissues were analyzed by whole-exome sequencing, single nucleotide polymorphism (SNP) and transcriptome arrays, and RNA sequencing; assessed for mutations, fusions, tumor mutational burden (TMB), and chromosomal instability (CI); and classified into GBM subgroups. Each genomic report was discussed at a multidisciplinary tumor board meeting to evaluate for matching trials. From 111 consecutive patients, 97.3% accepted inclusion in this study. Eighty-six (77%) were treated with radiation therapy/temozolomide (TMZ) and adjuvant TMZ. One NTRK2 and three FGFR3-TACC3 fusions were identified. Copy number alterations in GRB2 and SMYD4 were significantly correlated with worse median OS together with known clinical variables like age, performance status, steroid dose, and O6-methyl-guanine-DNA-methyl-transferase status. Patients with CI-median or TMB-high had significantly worse median OS compared to CI-low/high or TMB-low/median. In conclusion, performing genomic profiling at diagnosis enables evaluation of genomic-driven therapy at the first progression. Furthermore, TMB-high or CI-median patients had worse median OS, which can support the possibility of offering experimental treatment already at the first line for this group.

VEGF-C sustains VEGFR2 activation under bevacizumab therapy and promotes glioblastoma maintenance

Background

Glioblastoma ranks among the most lethal cancers, with current therapies offering only palliation. Paracrine vascular endothelial growth factor (VEGF) signaling has been targeted using anti-angiogenic agents, whereas autocrine VEGF/VEGF receptor 2 (VEGFR2) signaling is poorly understood. Bevacizumab resistance of VEGFR2-expressing glioblastoma cells prompted interrogation of autocrine VEGF-C/VEGFR2 signaling in glioblastoma.

Methods

Autocrine VEGF-C/VEGFR2 signaling was functionally investigated using RNA interference and exogenous ligands in patient-derived xenograft lines and primary glioblastoma cell cultures in vitro and in vivo. VEGF-C expression and interaction with VEGFR2 in a matched pre- and post-bevacizumab treatment cohort were analyzed by immunohistochemistry and proximity ligation assay.

Results

VEGF-C was expressed by patient-derived xenograft glioblastoma lines, primary cells, and matched surgical specimens before and after bevacizumab treatment. VEGF-C activated autocrine VEGFR2 signaling to promote cell survival, whereas targeting VEGF-C expression reprogrammed cellular transcription to attenuate survival and cell cycle progression. Supporting potential translational significance, targeting VEGF-C impaired tumor growth in vivo, with superiority to bevacizumab treatment.

Conclusions

Our results demonstrate VEGF-C serves as both a paracrine and an autocrine pro-survival cytokine in glioblastoma, promoting tumor cell survival and tumorigenesis. VEGF-C permits sustained VEGFR2 activation and tumor growth, where its inhibition appears superior to bevacizumab therapy in improving tumor control.

Publisher Correction: Actively personalized vaccination trial for newly diagnosed glioblastoma

The additional author support information was erroneously omitted from the Supplementary Information. This has been corrected online.

Abstract A020: Immunomonitoring for actively personalized peptide vaccines (APVACs) during immunotherapeutic treatment of glioblastoma

Cancer immunotherapy to gliomas has so far failed to show encouraging results, as gliomas are rarely mutated and show various mechanisms of immune escape. To improve therapy to these type of cancer, the Glioma Actively Personalized Vaccine Consortium (GAPVAC) integrated a highly personalized peptide vaccine approach into glioblastoma standard of care treatment combining neoepitope and nonmutated tumor antigens to exploit the full repertoire of tumor antigens. In this phase I clinical trial fifteen patients received two different types of personalized peptide vaccines (APVAC1 and APVAC2), that were selected based on transcriptome, immunopeptidome and mutational analysis of the patient’s individual tumors. While APVAC1 vaccines were composed of nonmutated tumor antigens selected in a warehouse-based approach, APVAC2 vaccines primarily targeted neoepitopes. Both vaccines were used in combination with poly-ICLC and GM-CSF as adjuvants and demonstrated expected safety profile and outstanding Immunogenicity. Immunomonitoring of APVAC1 peptides was carried out using a combinatorial ex vivo Class I 2D multimer (2DMM) and Class II intracellular cytokine staining (ICS) assay with an outstanding sensitivity to detect even one peptide-specific cell in one million of CD4 or CD8 T-cells. Nonmutated APVAC1 class I peptides showed induction of persistent CD8 T-cell responses, mainly consisting of a highly favorable central memory phenotype (CM). Furthermore, APVAC1 class II peptides demonstrated induction of polyfunctional CD4 T-cells predominantly of a type 1 T helper cell (TH1) phenotype. Notably, an APVAC1 class II specific T-cell response was detected in tumor-infiltrating lymphocyte (TIL) fraction obtained from resection of one patient. On the other side, immune responses to APVAC2 peptides were analyzed using a pan-ICS assay including a single in vitro sensitization step to analyze a broad array of cytokines produced by CD4 T helper (TH) cells and CD8 CTLs in parallel. APVAC2 peptides showed excellent immunogenicity and induced potent and multifunctional CD4 T-cell responses, mostly of a TH1 phenotype that often concurred with CTL responses. Furthermore, the induction of APVAC1-specific CD8 memory cells, as a marker for the potency of the vaccine-induced immune responses, reversely correlated with the baseline frequencies of regulatory T-cells (Treg). Taken together, actively personalized peptide vaccines (APVACs) were highly immunogenic and induced sustained responses of a highly favorable CD4 and CD8 T-cell phenotype. The vaccination showed the expected safety profile and the approach was feasible, even in this highly individualized setting. Therefore, the APVAC vaccination approach clearly represents a step forward on the path to bring the benefit of immunotherapy to glioblastoma patients.

Citation Format: Alexander Ulges, Norbert Hilf, Wolfgang Wick, Michael Platten, Pierre-Yves Dietrich, Katrin Frenzel, Arie Admon, Sjoerd S.H. van der Burg, Andreas von Deimling, Per thor Straten, Cecile Gouttefangeas, Judith R. Kroep, Francisco Martínez-Ricarte, Hideo Okada, Christian H. Ottensmeier, Berta Ponsati, Hans S. Poulsen, Stefan Stevanovic, Ghazaleh Tabatabai, Hans-Georg Rammensee, Ugur Sahin, Dominik Maurer, Regina Mendrzyk. Immunomonitoring for actively personalized peptide vaccines (APVACs) during immunotherapeutic treatment of glioblastoma [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A020.

Actively personalized vaccination trial for newly diagnosed glioblastoma

Patients with glioblastoma currently do not sufficiently benefit from recent breakthroughs in cancer treatment that use checkpoint inhibitors1,2. For treatments using checkpoint inhibitors to be successful, a high mutational load and responses to neoepitopes are thought to be essential3. There is limited intratumoural infiltration of immune cells4 in glioblastoma and these tumours contain only 30-50 non-synonymous mutations5. Exploitation of the full repertoire of tumour antigens-that is, both unmutated antigens and neoepitopes-may offer more effective immunotherapies, especially for tumours with a low mutational load. Here, in the phase I trial GAPVAC-101 of the Glioma Actively Personalized Vaccine Consortium (GAPVAC), we integrated highly individualized vaccinations with both types of tumour antigens into standard care to optimally exploit the limited target space for patients with newly diagnosed glioblastoma. Fifteen patients with glioblastomas positive for human leukocyte antigen (HLA)-A*02:01 or HLA-A*24:02 were treated with a vaccine (APVAC1) derived from a premanufactured library of unmutated antigens followed by treatment with APVAC2, which preferentially targeted neoepitopes. Personalization was based on mutations and analyses of the transcriptomes and immunopeptidomes of the individual tumours. The GAPVAC approach was feasible and vaccines that had poly-ICLC (polyriboinosinic-polyribocytidylic acid-poly-L-lysine carboxymethylcellulose) and granulocyte-macrophage colony-stimulating factor as adjuvants displayed favourable safety and strong immunogenicity. Unmutated APVAC1 antigens elicited sustained responses of central memory CD8+ T cells. APVAC2 induced predominantly CD4+ T cell responses of T helper 1 type against predicted neoepitopes.

Feasibility of multi-parametric PET and MRI for prediction of tumour recurrence in patients with glioblastoma

BACKGROUND

Recurrence in glioblastoma patients often occur close to the original tumour and indicates that the current treatment is inadequate for local tumour control. In this study, we explored the feasibility of using multi-modality imaging at the time of radiotherapy planning. Specifically, we aimed to identify parameters from pre-treatment PET and MRI with potential to predict tumour recurrence.

MATERIALS AND METHODS

Sixteen patients were prospectively recruited and treated according to established guidelines. Multi-parametric imaging with ¹⁸F-FET PET/CT and ¹⁸F-FDG PET/MR including diffusion and dynamic contrast enhanced perfusion MRI were performed before radiotherapy. Correlations between imaging parameters were calculated. Imaging was related to the voxel-wise outcome at the time of tumour recurrence. Within the radiotherapy target, median differences of imaging parameters in recurring and non-recurring voxels were calculated for contrast-enhancing lesion (CEL), non-enhancing lesion (NEL), and normal appearing grey and white matter. Logistic regression models were created to predict the patient-specific probability of recurrence. The most important parameters were identified using standardized model coefficients.

RESULTS

Significant median differences between recurring and non-recurring voxels were observed for FDG, FET, fractional anisotropy, mean diffusivity, mean transit time, extra-vascular, extra-cellular blood volume and permeability derived from scans prior to chemo-radiotherapy. Tissue-specific patterns of voxel-wise correlations were observed. The most pronounced correlations were observed for ¹⁸F-FDG- and ¹⁸F-FET-uptake in CEL and NEL. Voxel-wise modelling of recurrence probability resulted in area under the receiver operating characteristic curve of 0.77 from scans prior to therapy. Overall, FET proved to be the most important parameter for recurrence prediction.

CONCLUSION

Multi-parametric imaging before radiotherapy is feasible and significant differences in imaging parameters between recurring and non-recurring voxels were observed. Combining parameters in a logistic regression model enabled patient-specific maps of recurrence probability, where ¹⁸F-FET proved to be most important. This strategy could enable risk-adapted radiotherapy planning.

Early treatment response evaluation using FET PET compared to MRI in glioblastoma patients at first progression treated with bevacizumab plus lomustine

BACKGROUND

The goal of this prospective study was to compare the value of both conventional MRI and O-(2-¹⁸F-fluoroethyl)-L-tyrosine (FET) PET for response evaluation in glioblastoma patients treated with bevacizumab plus lomustine (BEV/LOM) at first progression.

METHODS

After chemoradiation with concomitant and adjuvant temozolomide, 21 IDH wild-type glioblastoma patients at first progression (age range, 33-75 years; MGMT promoter unmethylated, 81%) were treated with BEV/LOM. Contrast-enhanced MRI and FET-PET scans were performed at baseline and after 8-10 weeks. We obtained FET metabolic tumor volumes (MTV) and tumor/brain ratios. Threshold values of FET-PET parameters for treatment response were established by ROC analyses using the post-progression overall survival (OS) ≤/>9 months as the reference. MRI response assessment was based on RANO criteria. The predictive ability of FET-PET thresholds and MRI changes on early response assessment was evaluated subsequently concerning OS using uni- and multivariate survival estimates.

RESULTS

Early treatment response as assessed by RANO criteria was not predictive for an OS>9 months (P = 0.203), whereas relative reductions of all FET-PET parameters significantly predicted an OS>9 months (P < 0.05). The absolute MTV at follow-up enabled the most significant OS prediction (sensitivity, 85%; specificity, 88%; P = 0.001). Patients with an absolute MTV below 5 ml at follow-up survived significantly longer (12 vs. 6 months, P < 0.001), whereas early responders defined by RANO criteria lived only insignificantly longer (9 vs. 6 months; P = 0.072). The absolute MTV at follow-up remained significant in the multivariate survival analysis (P = 0.006).

CONCLUSIONS

FET-PET appears to be useful for identifying responders to BEV/LOM early after treatment initiation.

Prognostic value of O-6-methylguanine-DNA methyltransferase (MGMT) protein expression in glioblastoma excluding nontumour cells from the analysis

AIMS

It is important to predict response to treatment with temozolomide (TMZ) in glioblastoma (GBM) patients. Both MGMT protein expression and MGMT promoter methylation status have been reported to predict the response to TMZ. We investigated the prognostic value of quantified MGMT protein levels in tumour cells and the prognostic importance of combining information of MGMT protein level and MGMT promoter methylation status.

METHODS

MGMT protein expression was quantified in tumour cells in 171 GBMs from the population-based Region of Southern Denmark (RSD)-cohort using a double immunofluorescence approach. Pyrosequencing was performed in 157 patients. For validation we used GBM-patients from a Nordic Study (NS) investigating the effect of radiotherapy and different TMZ schedules.

RESULTS

When divided at the median, patients with low expression of MGMT protein (AF-low) had the best prognosis (HR = 1.5, P = 0.01). Similar results were observed in the subgroup of patients receiving the Stupp regimen (HR = 2.0, P = 0.001). In the NS-cohort a trend towards superior survival (HR = 1.6, P = 0.08) was seen in patients with AF-low. Including MGMT promoter methylation status, we found for both cohorts that patients with methylated MGMT promoter and AF-low had the best outcome; median OS 23.1 and 20.0 months, respectively.

CONCLUSION

Our data indicate that MGMT protein expression in tumour cells has an independent prognostic significance. Exclusion of nontumour cells contributed to a more exact analysis of tumour-specific MGMT protein expression. This should be incorporated in future studies evaluating MGMT status before potential integration into clinical practice.

Toxicity and efficacy of lomustine and bevacizumab in recurrent glioblastoma patients

The combination of lomustine and bevacizumab is a commonly used salvage treatment for recurrent glioblastoma (GBM). We investigated the toxicity and efficacy of lomustine plus bevacizumab (lom-bev) in a community-based patient cohort and made a comparison to another frequently used combination therapy consisting of irinotecan plus bevacizumab (iri-bev). Seventy patients with recurrent GBM were treated with lomustine 90 mg/m² every 6 weeks and bevacizumab 10 mg/kg every 2 weeks. Toxicity was registered and compared to the toxicity observed in 219 recurrent GBM patients who had previously been treated with irinotecan 125 mg/m² and bevacizumab 10 mg/kg every 2 weeks. The response rate was 37.1% for lom-bev and 30.1% for iri-bev. Median progression-free survival (PFS) was 23 weeks for lom-bev and 21 weeks for iri-bev (p = 0.9). Overall survival (OS) was 37 weeks for lom-bev and 32 weeks for iri-bev (p = 0.5). Lom-bev caused a significantly higher frequency of thrombocytopenia (11.4% grade 3-4) compared to iri-bev (3.5% grade 3-4). Iri-bev patients had more gastrointestinal toxicity with regard to nausea, vomiting, diarrhea, constipation and stomatitis. Within the limitations of the study lom-bev is a well-tolerated treatment for recurrent GBM, although hematological toxicity may be a dose limiting factor. No significant differences between lom-bev and iri-bev were observed with regard to PFS or OS. The differences in toxicity profiles between lom-bev and iri-bev could guide treatment decision in recurrent GBM therapy as efficacy is equal and no predictive factors for efficacy exist.

A comprehensive profile of recurrent glioblastoma

In spite of relentless efforts to devise new treatment strategies, primary glioblastomas invariably recur as aggressive, therapy-resistant relapses and patients rapidly succumb to these tumors. Many therapeutic agents are first tested in clinical trials involving recurrent glioblastomas. Remarkably, however, fundamental knowledge on the biology of recurrent glioblastoma is just slowly emerging. Here, we review current knowledge on recurrent glioblastoma and ask whether and how therapies change intra-tumor heterogeneity, molecular traits and growth pattern of glioblastoma, and to which extent this information can be exploited for therapeutic decision-making. We conclude that the ability to characterize and predict therapy-induced changes in recurrent glioblastoma will determine, whether, one day, glioblastoma can be contained in a state of chronic disease.

Assessment of Quantitative and Allelic MGMT Methylation Patterns as a Prognostic Marker in Glioblastoma

Methylation of the O⁶-methylguanine-DNA methyltransferase (MGMT) gene is a predictive and prognostic marker in newly diagnosed glioblastoma patients treated with temozolomide but how MGMT methylation should be assessed to ensure optimal detection accuracy is debated. We developed a novel quantitative methylation-specific PCR (qMSP) MGMT assay capable of providing allelic methylation data and analyzed 151 glioblastomas from patients receiving standard of care treatment (Stupp protocol). The samples were also analyzed by immunohistochemistry (IHC), standard bisulfite pyrosequencing, and genotyped for the rs1690252 MGMT promoter single nucleotide polymorphism. Monoallelic methylation was observed more frequently than biallelic methylation, and some cases with monoallelic methylation expressed the MGMT protein whereas others did not. The presence of MGMT methylation was associated with better overall survival (p = 0.006; qMSP and p = 0.002; standard pyrosequencing), and the presence of the protein was associated with worse overall survival (p = 0.009). Combined analyses of qMSP and standard pyrosequencing or IHC identified additional patients who benefited from temozolomide treatment. Finally, low methylation levels were also associated with better overall survival (p = 0.061; qMSP and p = 0.02; standard pyrosequencing). These data support the use of both MGMT methylation and MGMT IHC but not allelic methylation data as prognostic markers in patients with temozolomide-treated glioblastoma.

Abstract B3: Prognostic and predictive biomarkers in recurrent WHO grade 3 malignant glioma patients treated with bevacizumab and irinotecan

BACKGROUND Bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor A (VEGF-A), has demonstrated activity in the treatment of recurrent malignant glioma. High response rates have been observed, but particularly in WHO grade 3 gliomas, efforts to identify predictors of clinical response have been limited. Predictive markers and prognostic models are required in order to individualize treatment for this patient population. The primary endpoint of this study was to identify predictive biomarkers associated with response to bevacizumab therapy. The secondary endpoint was to identify prognostic factors associated with progression-free survival (PFS) and overall survival (OS).

METHODS A total of 62 consecutive, recurrent grade 3 glioma patients were retrospectively evaluated. Eligible patients from our center had a WHO performance status of 0-2 and were administered bevacizumab and irinotecan between December 2005 and November 2014 according to a previously published clinical protocol. Baseline factors screened for potential prognostic and predictive value included: Age, gender, PS, WHO grade 3 diagnosis, tumor size and location, multifocal disease, extent of resection, number of prior chemotherapy regiments, response to prior chemotherapy, first-line treatment, number of previous recurrences, neurological deficit, corticosteroid use, necrosis, vascular proliferation, neutrophil-to-lymphocyte ratio, and expression of p53, EGFR, MIB-1, MGMT, IDH1 and ATRX. Candidate factors with p-values below 5% were considered for multivariate analysis. Prognostic models were generated by logistic regression and Cox regression, modelling response and survival endpoints.

RESULTS Twenty-two patients (35.5%) demonstrated a response according to the RANO criteria. Responders had significantly prolonged OS (p = 0.007) and trended toward longer PFS (p = 0.067) as compared to non-responders (OS: 12.4 vs 4.3 months, PFS: 5.6 vs 3.2 months). Presence of necrosis (OR: 0.17, CI: 0.04-0.68, p = 0.012) and a WHO performance status (PS) of more than 1 (OR: 0.04, CI: 0.002-0.89, p = 0.042) were more common in non-responders than responders. Female gender (HR: 0.48, CI: 0.28-0.82, p = 0.008) and a PS of 0-1 (HR: 0.20, CI: 0.10-0.41, p &lt; 0.0001) were identified as positive prognostic factors for PFS. Immunohistochemical p53 negativity (HR: 0.47, CI: 0.26-0.87, p = 0.016) and low PS (HR: 0.17, CI: 0.07-0.39, p &lt; 0.0001) correlated with extended OS and these factors were included in a prognostic model.

CONCLUSIONS A favorable baseline PS and absence of necrosis were positively associated with response to bevacizumab treatment in recurrent grade 3 glioma patients. Low PS, female gender and p53 negativity are prognostic of improved outcome in this patient group.

Citation Format: Anders Toft, Thomas Urup, Ib J. Christensen, Signe R. Michaelsen, Babloo S. Lukram, Kirsten Grunnet, Michael Kosteljanetz, Vibeke A. Larsen, Ulrik Lassen, Helle Broholm, Hans S. Poulsen. Prognostic and predictive biomarkers in recurrent WHO grade 3 malignant glioma patients treated with bevacizumab and irinotecan. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B3.

Urokinase-Type Plasminogen Activator Receptor as a Potential PET Biomarker in Glioblastoma

Glioblastoma is one of the most malignant types of human cancer, and the prognosis is poor. The development and validation of novel molecular imaging biomarkers has the potential to improve tumor detection, grading, risk stratification, and treatment monitoring of gliomas. The aim of this study was to explore the potential of PET imaging of the urokinase-type plasminogen activator receptor (uPAR) in glioblastoma.

METHODS

The uPAR messenger RNA expression of tumors from 19 glioblastoma patients was analyzed, and a cell culture derived from one of these patients was used to establish an orthotopic xenograft model of glioblastoma. Tumor growth was monitored using bioluminescence imaging. Five to six weeks after inoculation, all mice were scanned with small-animal PET/CT using two new uPAR PET ligands ((64)Cu-NOTA-AE105 and (68)Ga-NOTA-AE105) and, for comparison, O-(2-(18)F-fluoroethyl)-l-tyrosine ((18)F-FET). One MRI scan was obtained for each mouse to confirm tumor location. The uPAR specificity of (64)Cu-NOTA-AE105 was confirmed by alignment of hematoxylin- and eosin-stained and uPAR immunohistochemistry-stained slides of the brain with the activity distribution as determined using autoradiography.

RESULTS

uPAR expression was found in all 19 glioblastoma patient tumors, and high expression of uPAR correlated with decreased overall survival (P = 0.04). Radiolabeling of NOTA-AE105 with (64)Cu and (68)Ga was straightforward, resulting in a specific activity of approximately 20 GBq/μmol and a radiochemical purity of more than 98% for (64)Cu-NOTA-AE105 and more than 97% for (68)Ga-NOTA-AE105. High image contrast resulting in clear tumor delineation was found for both (68)Ga-NOTA-AE105 and (64)Cu-NOTA-AE105. Absolute uptake in tumor was higher for (18)F-FET (3.5 ± 0.8 percentage injected dose [%ID]/g) than for (64)Cu-NOTA-AE105 (1.2 ± 0.4 %ID/g) or (68)Ga-NOTA-AE105 (0.4 ± 0.1 %ID/g). A similar pattern was observed in background brain tissue, where uptake was 1.9 ± 0.1 %ID/g for (18)F-fluorothymidine, compared with 0.05 ± 0.01 %ID/g for (68)Ga-NOTA-AE105 and 0.11 ± 0.02 %ID/g for (64)Cu-NOTA-AE105. The result was a significantly higher tumor-to-background ratio for both (68)Ga-NOTA-AE105 (7.6 ± 2.1, P < 0.05) and (64)Cu-NOTA-AE105 (10.6 ± 2.3, P < 0.01) than for (18)F-FET PET (1.8 ± 0.3). Autoradiography of brain slides confirmed that the accumulation of (64)Cu-NOTA-AE105 corresponded well with uPAR-positive cancer cells.

CONCLUSION

On the basis of our translational study, uPAR PET may be a highly promising imaging biomarker for glioblastoma. Further clinical exploration of uPAR PET in glioblastoma is therefore justified.

Simultaneous evaluation of brain tumour metabolism, structure and blood volume using [(18)F]-fluoroethyltyrosine (FET) PET/MRI: feasibility, agreement and initial experience

PURPOSE

Both [(18)F]-fluoroethyltyrosine (FET) PET and blood volume (BV) MRI supplement routine T1-weighted contrast-enhanced MRI in gliomas, but whether the two modalities provide identical or complementary information is unresolved. The aims of the study were to investigate the feasibility of simultaneous structural MRI, BV MRI and FET PET of gliomas using an integrated PET/MRI scanner and to assess the spatial and quantitative agreement in tumour imaging between BV MRI and FET PET.

METHODS

A total of 32 glioma patients underwent a 20-min static simultaneous PET/MRI acquisition on a Siemens mMR system 20 min after injection of 200 MBq FET. The MRI protocol included standard structural MRI and dynamic susceptibility contrast (DSC) imaging for BV measurements. Maximal relative tumour FET uptake (TBRmax) and BV (rBVmax), and Dice coefficients were calculated to assess the quantitative and spatial congruence in the tumour volumes determined by FET PET, BV MRI and contrast-enhanced MRI.

RESULTS

FET volume and TBRmax were higher in BV-positive than in BV-negative scans, and both VOLBV and rBVmax were higher in FET-positive than in FET-negative scans. TBRmax and rBVmax were positively correlated (R (2) = 0.59, p < 0.001). FET and BV positivity were in agreement in only 26 of the 32 patients and in 42 of 63 lesions, and spatial congruence in the tumour volumes as assessed by the Dice coefficients was generally poor with median Dice coefficients exceeding 0.1 in less than half the patients positive on at least one modality for any pair of modalities. In 56 % of the patients susceptibility artefacts in DSC BV maps overlapped the tumour on MRI.

CONCLUSION

The study demonstrated that although tumour volumes determined by BV MRI and FET PET were quantitatively correlated, their spatial congruence in a mixed population of treated glioma patients was generally poor, and the modalities did not provide the same information in this population of patients. Combined imaging of brain tumour metabolism and perfusion using hybrid PET/MR systems may provide complementary information on tumour biology, but the potential clinical value remains to be determined in future trials.

Abstract 5310: Prognostic and predictive biomarkers of clinical response to Bevacizumab in recurrent WHO grade 3 malignant glioma patients

Background: Bevacizumab, a monoclonal antibody targeting vascular endothelial growth factor A (VEGF-A), has proven activity in treatment of recurrent high-grade glioma. High response rates have been demonstrated, but particularly in WHO grade 3 malignant gliomas, efforts to identify predictors of clinical response have been limited. Predictive biomarkers and prognostic models are required in order to individualize treatment for this patient population. The primary end-point of this study was identification of prognostic and potentially predictive clinical and paraclinical factors of response. The secondary end-point was to identify prognostic factors associated with progression-free survival (PFS) and overall survival (OS).

Materials and methods: A total of 64 recurrent grade 3 glioma patients treated with bevacizumab and irinotecan were retrospectively evaluated. Eligible patients from our center had a WHO performance status of 0-2 and were administered bevacizumab and irinotecan between December 2005 and November 2014 according to a previously published clinical protocol.

The possibly relevant prognostic baseline factors screened for included: Age, gender, WHO grade 3 diagnosis, tumor size and location, multifocal disease, extent of resection, number of prior chemotherapy regiments, response to prior chemotherapy, first-line treatment, number of previous recurrences, neurological deficit, corticosteroid use, performance status, necrosis, vascular proliferation, neutrophil-to-lymphocyte ratio, and expression of p53, EGFR, Mib-1, MGMT, IDH-1 and ATRX.

Candidate factors were subjected to univariate analysis and factors with P-values below 0.10 were considered for multivariate analysis. Prognostic models were generated by logistic regression and Cox regression, modeling response and survival end-points. P-values below 0.05 were considered statistically significant.

Results will be presented.

Citation Format: Anders Toft, Thomas Urup, Kirsten Grunnet, Ib J. Christensen, Signe R. Michaelsen, Helle Broholm, Vibeke A. Larsen, Michael Kosteljanetz, Ulrik Lassen, Hans S. Poulsen. Prognostic and predictive biomarkers of clinical response to Bevacizumab in recurrent WHO grade 3 malignant glioma patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5310. doi:10.1158/1538-7445.AM2015-5310

Abstract 4170: The role of VEGF-C for cell viability, tumor growth and bevacizumab resistance in glioblastoma multiforme

Although treatment with the VEGF-A targeting antibody Bevacizumab has resulted in substantial response rates in patients with the brain tumor Glioblastoma Multiforme, patients invariable progress. The VEGF-A receptor VEGFR2, has in addition to be expressed on endothelial cells, recently been shown also to be expressed by GBM tumor cells. Autocrine VEGF-A/VEGFR2 signaling has been identified in GBM cells, but contradicting results exist for the effects of inhibiting VEGF-A and VEGFR2 respectively; indicating that VEGFR2 in GBM at least partly is activated by other factors than VEGF-A. Study aim was to search for other factors responsible for VEGFR2 activation in GBM cells and to examine their role for GBM growth and response to Bevacizumab.

To study VEGFR2 regulation we examined a VEGFR2-positive and a VEGFR2-negative GBM cell culture, which both expressed VEGF-A. In line with others, we found that VEGFR2 phosphorylation could be stimulated by recombinant VEGF-A, and found that inhibition of receptor phosphorylation by SU1498 resulted in significantly reduced proliferation of the VEGFR2-positive cells, while inhibition of the VEGF-A expressed by the cells using Bevacizumab only had minimal effect on proliferation. Examinations revealed that the VEGFR2-positive cells also were positive for the VEGF variant VEGF-C. Addition of recombinant VEGF-C protein to the VEGFR2-positive cells could stimulate VEGFR2 phosphorylation, while inhibition of VEGF-C using siRNA constructs resulted in reduced in vitro growth of VEGFR2-positive cells. Further, when injected into the brains of mice, VEGF-C-siRNA transfected cells resulted in reduced tumor growth and increased survival compared to control cells. Moreover, measurement of the VEGF-C mRNA level in 19 GBM patient tumors showed that all tumors were positive for VEGF-C expression, although the level was varying. To examine if VEGF-C expression represents a possible mechanism behind insensitivity towards Bevacizumab therapy, we are currently investigating the expression of VEGF-C in paired samples from GBM patients taken before and after Bevacizumab therapy and in xenograft tumors from mice receiving this treatment.

In conclusion, our current results show that VEGF-C is of importance for GBM cell viability and tumor growth presumable due to its ability to stimulate autocrine activation of VEGFR2. VEGF-C expression therefore could respresent a possible mechanism behind Bevacizumab resistance. An update on this will be presented.

Citation Format: Signe R. Michaelsen, Mette K. Nedergaard, Thomas Urup, Mette Villingshoej, Andreas Kjaer, Lara Perryman, Janine T. Erler, Ulrik Lassen, Hans S. Poulsen. The role of VEGF-C for cell viability, tumor growth and bevacizumab resistance in glioblastoma multiforme. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4170. doi:10.1158/1538-7445.AM2015-4170

Early changes in perfusion of glioblastoma during radio- and chemotherapy evaluated by T1-dynamic contrast enhanced magnetic resonance imaging

BACKGROUND

The survival times of patients with glioblastoma differ widely and biomarkers that would enable individualized treatment are needed. The objective of this study was to measure changes in the vascular physiology of tumor using T1-dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) in patients with glioblastoma during early stages of radio- and chemotherapy (Tx) and explore possible correlations with treatment outcomes.

MATERIAL AND METHODS

An exploratory prospective study was planned. Patients underwent DCE-MRI at baseline, after approximately one and six weeks of Tx and three and six months post-Tx. DCE-MRI at three Tesla generated maps of blood flow (BF), blood volume (BV), permeability (Ki) and volume of distribution (Vd) using a combination of model-free deconvolution and Patlak plots. Regions of interest in contrast enhancing tumor and in normal appearing white matter were contoured. Progression-free survival (PFS) was the primary clinical outcome. Patients with PFS > 6 months were compared with those with PFS < 6 months. Parameters of vascular physiology and changes in these during Tx were compared for these two groups at all time points using non-parametric statistics.

RESULTS

Eleven eligible patients were included and 46 DCE-MRI examinations were carried out. BF in tumor increased for all patients early during Tx (p = 0.005) and then fell to a level below baseline at post-Tx examinations (p = 0.016). A similar but non-significant trend was seen for tumor BV. There was no detectable difference between patients with PFS > 6 months versus PFS < 6 months with regards to baseline values or changes during and after Tx.

CONCLUSIONS

Although no correlations to outcomes were found, the results of this exploratory study may be hypothesis generating and will be examined in a larger patient group.

Targeting transcriptional addictions in small cell lung cancer with a covalent CDK7 inhibitor

Small cell lung cancer (SCLC) is an aggressive disease with high mortality, and the identification of effective pharmacological strategies to target SCLC biology represents an urgent need. Using a high-throughput cellular screen of a diverse chemical library, we observe that SCLC is sensitive to transcription-targeting drugs, in particular to THZ1, a recently identified covalent inhibitor of cyclin-dependent kinase 7. We find that expression of super-enhancer-associated transcription factor genes, including MYC family proto-oncogenes and neuroendocrine lineage-specific factors, is highly vulnerability to THZ1 treatment. We propose that downregulation of these transcription factors contributes, in part, to SCLC sensitivity to transcriptional inhibitors and that THZ1 represents a prototype drug for tailored SCLC therapy.

The use of longitudinal 18F-FET MicroPET imaging to evaluate response to irinotecan in orthotopic human glioblastoma multiforme xenografts

Objectives

Brain tumor imaging is challenging. Although ¹⁸F-FET PET is widely used in the clinic, the value of ¹⁸F-FET MicroPET to evaluate brain tumors in xenograft has not been assessed to date. The aim of this study therefore was to evaluate the performance of in vivo¹⁸F-FET MicroPET in detecting a treatment response in xenografts. In addition, the correlations between the ¹⁸F-FET tumor accumulation and the gene expression of Ki67 and the amino acid transporters LAT1 and LAT2 were investigated. Furthermore, Ki67, LAT1 and LAT2 gene expression in xenograft and archival patient tumors was compared.

Methods

Human GBM cells were injected orthotopically in nude mice and ¹⁸F-FET uptake was followed by weekly MicroPET/CT. When tumor take was observed, mice were treated with CPT-11 or saline weekly. After two weeks of treatment the brain tumors were isolated and quantitative polymerase chain reaction were performed on the xenograft tumors and in parallel on archival patient tumor specimens.

Results

The relative tumor-to-brain (T/B) ratio of SUV_max was significantly lower after one week (123±6%, n = 7 vs. 147±6%, n = 7; p = 0.018) and after two weeks (142±8%, n = 5 vs. 204±27%, n = 4; p = 0.047) in the CPT-11 group compared with the control group. Strong negative correlations between SUV_max T/B ratio and LAT1 (r = −0.62, p = 0.04) and LAT2 (r = −0.67, p = 0.02) were observed. In addition, a strong positive correlation between LAT1 and Ki67 was detected in xenografts. Furthermore, a 1.6 fold higher expression of LAT1 and a 23 fold higher expression of LAT2 were observed in patient specimens compared to xenografts.

Conclusions

¹⁸F-FET MicroPET can be used to detect a treatment response to CPT-11 in GBM xenografts. The strong negative correlation between SUV_max T/B ratio and LAT1/LAT2 indicates an export transport function. We suggest that ¹⁸F-FET PET may be used for detection of early treatment response in patients.

Abstract 3126: Insulinoma-associated 1 is a key transcriptional regulator of growth and survival-promoting pathways in small cell lung cancer

Insulinoma-associated 1 (INSM1) is neuroendocrine (NE) transcription factor which temporal and spatial expression pattern is restricted to regions undergoing NE differentiation during embryogenesis. INSM1 is however re-expressed at high levels in small-cell lung cancer (SCLC) together with an array of other NE markers. The NE signature of SCLC is a central diagnostic tool for the disease but recent data pinpoints that this distinct signature might play a role in SCLC pathogenesis.

The functional role of INSM1 in SCLC was here investigated by shRNA-mediated silencing of INSM1 in a panel of SCLC cell lines. Upon silencing of INSM1, significant reduction in cell viability was observed as measured by MTT assay. This reduction in cell viability was concomitant with decreased cell proliferation and increased apoptosis as measured by BrdU incorporation and cleaved caspase 3/7 levels, respectively. Accordingly with phenotypic growth changes it was demonstrated that INSM1 silencing caused reduced phosphorylation of members of the growth- and survival-promoting PI3K/Akt, MAPK and JAK-STAT signaling pathways and reduced levels of the inhibitors of apoptosis proteins (IAPs) members c-IAP1, XIAP and survivin. Importantly, it was shown that INSM1 is an upstream regulator of signatures previously shown to play a role in SCLC tumorigenesis, including achate-scute homolog 1 (ASCL1) and Sonic Hedgehog (SHh) pathway. Upon silencing of INSM1, a decrease in mRNA and protein levels of ASCL1 and downstream targets aldehyde dehydrogenase 1 (ALDH1) and delta-like ligand 3 (DLL3) was observed. Furthermore, mRNA levels of the SHh positive mediators Gli2, Gli3 and Smoothened was downregulated while the SHh inhibitor Patched was upregulated upon INSM1 silencing. Futhermore, overexpression of the Notch1 intracellular domain in SCLC cells resulted in a significant reduction in INSM1 expression and cell viability. This suggest that a master inhibitor of the NE signature, Notch1 signaling, could be an inhibitor of INSM1-driven tumorigenesis.

In conclusion, INSM1 is a potential key driver of growth- and survival-promoting pathways in SCLC and warrants further investigation of INSM1 as a therapeutic target.

Citation Format: Camilla L. Christensen, Takeshi Shimamura, Esra A. Akbay, Signe R. Michaelsen, Hans S. Poulsen, Kwok-kin Wong. Insulinoma-associated 1 is a key transcriptional regulator of growth and survival-promoting pathways in small cell lung cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3126. doi:10.1158/1538-7445.AM2013-3126

Single agent- and combination treatment with two targeted suicide gene therapy systems is effective in chemoresistant small cell lung cancer cells

BACKGROUND

Transcriptional targeted suicide gene (SG) therapy driven by the insulinoma-associated 1 (INSM1) promoter makes it possible to target suicide toxin production and cytotoxicity exclusively to small cell lung cancer (SCLC) cells and tumors. It remains to be determined whether acquired chemoresistance, as observed in the majority of SCLC patients, desensitizes SCLC cells to INSM1 promoter-driven SG therapy.

METHODS

A panel of SCLC cell lines resistant to clinically relevant chemotherapeutics was characterized regarding the expression of proteins involved in response to chemotherapy and regarding INSM1 promoter activity. Sensitivity towards INSM1 promoter-driven SG therapy was tested using different systems: Yeast cytosine deaminase-uracil phosphoribosyl transferase (YCD-YUPRT) in combination with the prodrug 5-fluorocytosine (5-FC) or Escherichia coli nitroreductase (NTR) together with the bromomustard prodrug SN27686.

RESULTS

The chemoresistant cell lines displayed heterogeneous expression profiles of molecules involved in multidrug resistance, apoptosis and survival pathways. Despite this, the INSM1 promoter activity was found to be unchanged or increased in SCLC chemoresistant cells and xenografts compared to chemosensitive variants. INSM1 promoter-driven SG therapy with YCD-YUPRT/5-FC or NTR/SN27686, was found to induce high levels of cytotoxicity in both chemosensitive and chemoresistant SCLC cells. Moreover, the combination of INSM1 promoter-driven YCD-YUPRT/5-FC therapy and chemotherapy, as well as the combination of INSM1 promoter-driven YCD-YUPRT/5-FC and NTR/SN27686 therapy, was observed to be superior to single agent therapy in chemoresistant SCLC cells.

CONCLUSIONS

Collectively, the present study demonstrates that targeted SG therapy is a potent therapeutic approach for chemoresistant SCLC patients, with the highest efficacy achieved when applied as combination SG therapy or in combination with standard chemotherapy.

Insertion of a nuclear factor kappa B DNA nuclear-targeting sequence potentiates suicide gene therapy efficacy in lung cancer cell lines

Lung cancer currently causes the majority of cancer-related deaths worldwide and new treatments are in high demand. Gene therapy could be a promising treatment but currently lacks sufficient efficiency for clinical use, primarily due to limited cellular and nuclear DNA delivery. In the present study, we investigated whether it was possible to exploit the endogenous nuclear-shuttling activity by the nuclear factor kappa B (NFκB) system, which is highly prominent in many cancers as well as lung cancer. We observed that insertion of a DNA nuclear-targeting sequence (DTS) recognized by NFκB could improve plasmid nuclear delivery and enhance the therapeutic effect of a validated transcriptionally cancer-targeted suicide gene therapy system. A clear correlation between the number of inserted NFκB-binding sites and the therapeutic effect of the suicide system was observed in both small cell lung cancer (SCLC) and non-SCLC cell lines. The effect was observed to be due to elevated nuclear translocation of the suicide gene-encoding plasmids. The results show that a significant improvement of gene therapeutic efficiency can be obtained by increasing the intracellular trafficking of therapeutic DNA. This is to our knowledge the first time a DTS strategy has been implemented for suicide gene therapy.

A phase II trial with bevacizumab and irinotecan for patients with primary brain tumors and progression after standard therapy

The combination of irinotecan and bevacizumab has shown efficacy in the treatment of recurrent glioblastoma multiforme (GBM). A prospective, phase II study of 85 patients with various recurrent brain tumors was carried out. Primary endpoints were progression free survival (PFS) and response rate.

MATERIAL AND METHODS

Patients with recurrent primary brain tumors with performance status 0-2 were eligible. Intravenous bevacizumab 10 mg/kg and irinotecan 125/340 mg/m(2) were administered every 14 days. Evaluation was carried out every eight weeks using MRI and Macdonald response criteria. Treatment was continued until progression.

RESULTS

In total 85 patients were included with the following histologies: GBM (n = 32), glioma WHO gr. III (n = 33), glioma WHO gr. II (n = 12) and others (n = 8). Patients received a median of four cycles. ORR (overall response rate) for glioblastoma was 25% and 59% achieved stable disease (SD). Median PFS was 5.2 months. For grade III gliomas ORR was 21% and 45% had SD. Median PFS was 3.7 months. No objective responses occurred in grade II gliomas. In the non-glioma population, one PR as well as several long PFS times were observed.

DISCUSSION AND CONCLUSION

The combination of bevacizumab and irinotecan is well tolerated and moderately efficacious in glioblastoma and glioma WHO gr. III. A majority of patients achieve at least disease stabilization. Prolonged progression-free survival in non-glioma patients warrants further research.

Targeting the epidermal growth factor receptor in solid tumor malignancies

The epidermal growth factor receptor (EGFR) is over-expressed, as well as mutated, in many types of cancers. In particular, the EGFR variant type III mutant (EGFRvIII) has attracted much attention as it is frequently and exclusively found on many tumor cells, and hence both EGFR and EGFRvIII have been proposed as valid targets in many cancer therapy settings. Different strategies have been developed in order to either inhibit EGFR/EGFRvIII activity or to ablate EGFR/EGFRvIII-positive tumor cells. Drugs that inhibit these receptors include monoclonal antibodies (mAbs) that bind to the extracellular part of EGFR, blocking the binding sites for the EGFR ligands, and intracellular tyrosine kinase inhibitors (TKIs) that block the ATP binding site of the tyrosine kinase domain. Besides an EGFRvIII-targeted vaccine, conjugated anti-EGFR mAbs have been used in different settings to deliver lethal agents to the EGFR/EGFRvIII-positive cells; among these are radio-labelled mAbs and immunotoxins. This article reviews the current status and efficacy of EGFR/EGFRvIII-targeted therapies.

Abstract 832: Suicide gene therapy is effective for treating chemo-resistant small cell lung cancer cells

Background: Resistance arises in patients with small cell lung cancer (SCLC) following treatment with chemotherapeutic agents. Suicide gene (SG) therapy is a novel treatment strategy for cancer in which the introduced therapeutic gene encodes an enzyme capable of transforming a non-toxic prodrug into a cell poison. By coupling the SCLC specific promoter Insulinoma-associated 1 (INSM1) to the SG, it is possible to target SG expression and resulting cytotoxicity exclusive to SCLC cells. The aim of this project was to investigate the influence of chemo-resistance on transcriptional targeted SG therapy. Results: As an in vitro model of chemo-resistance we used a number of SCLC cell lines resistant to different chemotherapeutic agents used in first-line treatment of SCLC patients. Protein expression analysis showed the cells lines to vary in expression of a several proteins correlated to development of resistance. Despite of this the INSM1 promoter activity was found to be equally or increased in chemo-resistant compared to chemo-sensitive cells as measured by luciferase reporter assays and determination of INSM1 mRNA levels by RT-PCR. Additionally, in tumor xenografts stably expressing EGFP from the INSM1 promoter it was apparent that the INSM1 promoter activity is very strong and stable in vivo. Cytotoxic effects of two different SG systems driven by the INSM1 promoter were tested in the chemo-resistant cell lines by MTT assays. One consisted of the fusion SG of yeast-cytosine-deaminase (YCD) and yeast-uracil-phosphoribosyl-transferase (YUPRT) and the prodrug 5-fluorocytosin (5-FC). The other system consisted of the Nitroreductase (NTR) gene and SN27686 prodrug. While equal sensitivity was found in chemo-sensitive and -resistant cells towards YCD-YUPRT/5-FC therapy, the NTR/SN276868 system showed reduced cytotoxicity in cells resistant to alkylating agents. Importantly, equal cytotoxicity could be obtained in these chemo-resistant cells upon NTR/SN27686 therapy by exposing cells to higher prodrug doses, still not inducing off-target toxicity in NTR-negative cells. Finally, the combination of YCD-YUPRT/5-FC SG therapy with standard chemotherapy and with NTR/SN27686 SG therapy, respectively, were tested and evaluated by MTT assay. In contrast to chemo-sensitive cells, where the combination therapy had no additive effect, significantly additive cytotoxicity was achieved in chemo-resistant SCLC cells exposed to combination therapy compared to single agent therapy. Conclusion: The results demonstrate that targeted SG therapy is equally effective in chemo-resistant and -sensitive SCLC cells and that additional effect can be achieved in chemo-resistant SCLC cells when SG therapy is given in combination with chemotherapy or another SG therapy system. INSM1-driven SG therapy therefore seems potent to be effective in the treatment of SCLC patients with chemo-resistant tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 832. doi:1538-7445.AM2012-832

Abstract 2732: Internalization of the dual-specific immunotoxin D2C7-(scdsFv)-PE38KDEL in malignant glioma cell lines

Aim: The aim of this study is firstly to examine if the D2C7-immunotoxin (D2C7-IT) specifically binds to the epidermal growth factor receptor (EGFRwt) and the EGFR-mutant EGFRvIII subsequently inducing cell death. Secondly, to study the internalization of D2C7-IT after binding to EGFRwt/EGFRvIII. Background: Glioblastoma multiforme (GBM) is a malignant primary brain tumor and from diagnose median survival remains around 15 months. Tumor burden can be decreased by operation but eventually the tumor recurs. Thus, novel treatment-strategies for GBM patients are in great demand that would result prolonged median survival and increased quality of life. While EGFRwt and EGFRvIII are not found in normal brain tissue, expression of these are observed in malignant tissue of GBM, and consequently the D2C7-IT has been designed to target both EGFRwt and EGFRvIII. D2C7-IT comprises single chain disulphide stabilized fragment variables (scdsFv) of the bivalent anti-EGFR/EGFRvIII antibody D2C7, a 38 kDa fragment of the pseudomonas exotoxin A (PE38), and finally a C-terminal ‘endoplasmatic reticulum (ER) retention motif’: KDEL. In theory, the D2C7-IT is internalized after binding to EGFR/EGFRvIII and the PE38 moiety is proteolytically cleaved in the endosomal compartment, which releases the C-terminal toxic part of the PE38 into the cytosol. In the cytosol, binding of the KDEL-receptor assures transport to the ER where the toxic moiety inhibits protein synthesis and causes cell death. Methods: Western blotting was applied for examining D2C7-IT-binding to EGFRwt and EGFRvIII in different human malignant cell lines expressing varying levels of EGFRwt or EGFRvIII. MTT assays were used for assessing the impact of D2C7-IT on cell viability in these cell lines. Results: We observed that D2C7-IT binds to cells expressing EGFRwt or EGFRvIII. In addition, the binding on these cells could be inhibited by co-incubating with either EGF or the D2C7 antibody in surplus. Furthermore, D2C7-IT induced a moderate Tyr1173 phosphorylation (marker for internalization) on EGFRwt expressing cells. Concordantly, EGF induced a high level of EGFR-Tyr1173 phosphorylation on EGFRwt expressing cells, which was reduced to a moderate level when co-incubating with D2C7-IT in surplus. D2C7-IT reduced viability in cell cultures expressing EGFR or EGFRvIII while D2C7-IT had no effect on EGFRwt/EGFRvIII negative cells. We are currently trying to visualize the subcellular localizations of D2C7-IT after internalization by fluorescent microscopy. Conclusion: These preliminary results show that D2C7-IT specifically binds to EGFR and EGFRvIII, and reduces viability of EGFRwt/EGFRvIII expressing cells in vitro.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2732. doi:1538-7445.AM2012-2732

Abstract 3339: The role of active Notch signaling in glioblastoma neurosphere cultures

Background: Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in adults, with a median survival of 15 months for newly diagnosed GBM patients. Brain cancer stem-like cells (bCSC) are cancer cells with neural stem cell (NSC)-like properties found in GBM and they are proposed a central role in tumor initiation, progression, treatment resistance and relapse. The Notch receptor is expressed in the normal NSC population and is important for NSC maintenance and cell fate decision. The Notch signaling pathway is often deregulated in GBM and recent results suggest that this pathway plays a significant role in bCSC as well. The aim of the present project was therefore to further elucidate the significance of Notch expression and activation in GBM derived bCSC. Materials and methods: Human derived GBM xenograft cells were cultured in serum-free media in order to establish NSC-like neurosphere cultures. Notch modulation in the established GBM neurosphere cultures was accomplished either by blocking the Notch pathway using the γ-secretase inhibitor DAPT or by transfecting the cells with the intracellular constitutive active Notch-1 domain. Results: The established GBM neurosphere cultures expressed different levels of the Notch-1 receptor and the Notch downstream target Hes-1, which implies that the cultures have different Notch activation level. Cultures with high Notch activation showed sensitivity towards DAPT treatment. This was demonstrated by hampered cell viability, increase in the G0/G1 population, suggesting cell cycle arrest, and reduced ability to form colonies in soft-agar, together proposing that Notch inhibition targets the in vitro tumorigenic potential of these GBM neurosphere culture cells. When examining the effect of Notch inhibition on a variety of stem cell-like characteristics, only the primary sphere forming potential was affected. As such, the number of spheres formed in primary culture was reduced upon DAPT treatment while no effect was observed on the self-renewing capacity or the level of differentiation. In opposite, when the GBM neurosphere cells were transfected with the active part of the Notch-1 receptor a decrease in the G0/G1 population and an enhanced capability of soft-agar colony formation was observed as well as an increase in the self-renewing potential and de-differentiation. All cultures showed sensitivity towards artificial Notch-1 activation. These data implies that constitutive active Notch signaling increases the in vitro tumorigenic potential and affects the stem cell-like population in the GBM neurosphere cultures. Conclusion: Based on the observed results we propose that active Notch signaling is pivotal for the tumorigenic potential but not for the bCSC characteristics in GBM neurosphere cultures with elevated endogenous Notch activity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3339. doi:1538-7445.AM2012-3339

The effect of adenovirus-mediated gene expression of FHIT in small cell lung cancer cells

The candidate tumor suppressor fragile histidine traid (FHIT) is frequently inactivated in small cell lung cancer (SCLC). Mutations in the p53 gene also occur in the majority of SCLC leading to the accumulation of the mutant protein. Here we evaluated the effect of FHIT gene therapy alone or in combination with the mutant p53-reactivating molecule, PRIMA-1(Met)/APR-246, in SCLC. Overexpression of FHIT by recombinant adenoviral vector (Ad-FHIT)-mediated gene transfer in SCLC cells inhibited their growth by inducing apoptosis and when combined with PRIMA-1(Met)/APR-246, a synergistic cell growth inhibition was achieved.

Cetuximab insufficiently inhibits glioma cell growth due to persistent EGFR downstream signaling

Overexpression and/or amplification of the epidermal growth factor receptor (EGFR) is present in 35-45% of primary glioblastoma multiforme tumors and has been correlated with a poor prognosis. In this study, we investigated the effect of cetuximab and intracellular signaling pathways downstream of EGFR, important for cell survival and proliferation. We show insufficient EGFR downregulation and competition with endogenous EGFR ligands upon cetuximab treatment. Dose-response experiments showed inhibition of EGFR phosphorylation without affecting two of the prominent downstream signaling pathways. Our results indicate that amplification and/or overexpression of EGFR is an unsatisfactory predictor for response to cetuximab.

Replication stress and oxidative damage contribute to aberrant constitutive activation of DNA damage signalling in human gliomas

Malignant gliomas, the deadliest of brain neoplasms, show rampant genetic instability and resistance to genotoxic therapies, implicating potentially aberrant DNA damage response (DDR) in glioma pathogenesis and treatment failure. Here, we report on gross, aberrant constitutive activation of DNA damage signalling in low- and high-grade human gliomas, and analyze the sources of such endogenous genotoxic stress. Based on analyses of human glioblastoma multiforme (GBM) cell lines, normal astrocytes and clinical specimens from grade II astrocytomas (n=41) and grade IV GBM (n=60), we conclude that the DDR machinery is constitutively activated in gliomas, as documented by phosphorylated histone H2AX (gammaH2AX), activation of the ATM-Chk2-p53 pathway, 53BP1 foci and other markers. Oxidative DNA damage (8-oxoguanine) was high in some GBM cell lines and many GBM tumors, while it was low in normal brain and grade II astrocytomas, despite the degree of DDR activation was higher in grade II tumors. Markers indicative of ongoing DNA replication stress (Chk1 activation, Rad17 phosphorylation, replication protein A foci and single-stranded DNA) were present in GBM cells under high- or low-oxygen culture conditions and in clinical specimens of both low- and high-grade tumors. The observed global checkpoint signaling, in contrast to only focal areas of overabundant p53 (indicative of p53 mutation) in grade II astrocytomas, are consistent with DDR activation being an early event in gliomagenesis, initially limiting cell proliferation (low Ki-67 index) and selecting for mutations of p53 and likely other genes that allow escape (higher Ki-67 index) from the checkpoint and facilitate tumor progression. Overall, these results support the potential role of the DDR machinery as a barrier to gliomagenesis and indicate that replication stress, rather than oxidative stress, fuels the DNA damage signalling in early stages of astrocytoma development.

Targeted cytosine deaminase-uracil phosphoribosyl transferase suicide gene therapy induces small cell lung cancer-specific cytotoxicity and tumor growth delay

PURPOSE

Small cell lung cancer (SCLC) is a highly malignant cancer for which there is no curable treatment. Novel therapies are therefore in great demand. In the present study we investigated the therapeutic effect of transcriptionally targeted suicide gene therapy for SCLC based on the yeast cytosine deaminase (YCD) gene alone or fused with the yeast uracil phosphoribosyl transferase (YUPRT) gene followed by administration of 5-fluorocytosine (5-FC) prodrug.

EXPERIMENTAL DESIGN

The YCD gene or the YCD-YUPRT gene was placed under regulation of the SCLC-specific promoter insulinoma-associated 1 (INSM1). Therapeutic effect was evaluated in vitro in SCLC cell lines and in vivo in SCLC xenografted nude mice using the nonviral nanoparticle DOTAP/cholesterol for transgene delivery.

RESULTS

INSM1-YCD/5-FC and INSM1-YCD-YUPRT/5-FC therapy induced high cytotoxicity in a range of SCLC cell lines. The highest therapeutic effect was obtained from the YCD-YUPRT fusion gene strategy. No cytotoxicity was induced after treatment of cell lines of other origin than SCLC. In addition the INSM1-YCD-YUPRT/5-FC therapy was superior to an established suicide gene system consisting of the herpes simplex virus thymidine kinase (HSVTK) gene and the prodrug ganciclovir. The superior effect was in part due to massive bystander cytotoxicity of YCD-YUPRT-produced toxins. Finally, INSM1-YCD-YUPRT/5-FC therapy induced significant tumor growth delay in SCLC xenografts compared with control-treated xenografts.

CONCLUSIONS

The current study is the first to test cytosine deaminase-based suicide gene therapy for SCLC and the first to show an antitumor effect from the delivery of suicide gene therapeutics for SCLC in vivo.

Acute damage by naphthalene triggers expression of the neuroendocrine marker PGP9.5 in airway epithelial cells

Protein Gene Product 9.5 (PGP9.5) is highly expressed in nervous tissue. Recently PGP9.5 expression has been found to be upregulated in the pulmonary epithelium of smokers and in non-small cell lung cancer, suggesting that it also plays a role in carcinogen-inflicted lung epithelial injury and carcinogenesis. We investigated the expression of PGP9.5 in mice in response to two prominent carcinogens found in tobacco smoke: Naphthalene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). By immunostaining, we found that PGP9.5 protein was highly expressed throughout the airway epithelium in the days immediately following a single injection of naphthalene. In contrast, PGP9.5 was exclusively confined to neurons and neuroendocrine cells in the control and NNK-exposed lungs. Furthermore, we investigated the expression of PGP9.5 mRNA in the lungs by quantitative RT-PCR (qPCR). PGP9.5 mRNA expression was highly upregulated in the days immediately following naphthalene injection and gradually returning to that of control mice 5 days after naphthalene injection. In contrast, exposure to NNK did not result in a significant increase in PGP9.5 mRNA 10 weeks after exposure. No increased expression of two other neuroendocrine markers was found in the non-neuroendocrine epithelial cells after naphthalene exposure. In contrast, immunostaining for the cell cycle regulator p27(Kip1), which has previously been associated with PGP9.5 in lung cancer cells, revealed transient downregulation of p27(Kip1) in naphthalene exposed airways compared to controls, indicating that the rise in PGP9.5 in the airway epithelium is related to downregulation of p27(Kip1). This study is the first to specifically identify the carcinogen naphthalene as an inducer of PGP9.5 expression in non-neuroendocrine epithelium after acute lung injury and further strengthens the accumulating evidence of PGP9.5 as a central player in lung epithelial damage and early carcinogenesis.

EGFRvIII escapes down-regulation due to impaired internalization and sorting to lysosomes

EGFRvIII is a mutant variant of the epidermal growth factor receptor (EGFR) found exclusively in various cancer types. EGFRvIII lacks a large part of the extracellular domain and is unable to bind ligands; however, the receptor is constitutively phosphorylated and able to activate downstream signaling pathways. Failure to attenuate signaling by receptor down-regulation could be one of the major mechanisms by which EGFRvIII becomes oncogenic. Using a cell system expressing either EGFR or EGFRvIII with no expression of other EGFR family members and with endogenous levels of key degradation proteins, we have investigated the down-regulation of EGFRvIII and compared it to that of EGFR. We show that, in contrast to EGFR, EGFRvIII is inefficiently degraded. EGFRvIII is internalized, but the internalization rate of the mutated receptor is significantly less than that of unstimulated EGFR. Moreover, internalized EGFRvIII is recycled rather than delivered to lysosomes. EGFRvIII binds the ubiquitin ligase c-Cbl via Grb2, whereas binding via phosphorylated tyrosine residue 1045 seems to be limited. Despite c-Cbl binding, the receptor fails to become effectively ubiquitinylated. Thus, our results suggest that the long lifetime of EGFRvIII is caused by inefficient internalization and impaired sorting to lysosomes due to lack of effective ubiquitinylation.

A prospective PET study of patients with glioblastoma multiforme

OBJECTIVE

To study the post-surgical metabolic and structural cerebral changes in patients with glioblastoma multiforme (GBM).

MATERIALS AND METHODS

We examined ten patients prospectively with newly diagnosed GBM. All patients were primarily treated with surgery, followed by chemotherapy (carmustine, cisplatine and etoposide) and radiotherapy. Positron emission tomography (PET) was used to measure tumor- and cerebral metabolism. CT or MRI was used to estimate tumor volume by measurements of tumor area.

RESULTS

Tumor metabolism was not increased during chemotherapy (P = 0.71), but increased during radiotherapy (P = 0.01). CT/MRI showed similar results with no increase in tumor area during chemotherapy (P = 0.33) but increase during radiotherapy (P = 0.002). During the entire study, tumor metabolism and area increased evenly (P = 0.01).

CONCLUSIONS

Our study did not show a gain of PET compared with structural imaging in the prospective evaluation of GBM. We found a difference in metabolic increase and tumor growth between the two treatment regimens, although this finding has limited relevance due to the design of the study.

Analysis of the epidermal growth factor receptor specific transcriptome: effect of receptor expression level and an activating mutation

Overexpression or expression of activating mutations of the epidermal growth factor receptor (EGFR) is common in cancer and correlates with neoplastic progression. The present study employed Affymetrix oligonucleotide arrays to profile genes induced by ligand-activated EGFR with the receptor either moderately expressed or overexpressed at an in-itself transforming level. These changes were compared to those induced by the naturally occurring constitutively active variant EGFRvIII. This study provides novel insight on the activities and mechanisms of EGFRvIII and EGFR mediated transformation, as genes encoding proteins with functions in promoting cell proliferation, invasion, antiapoptosis, and angiogenesis featured prominently in the EGFRvIII- and EGFR-expressing cells. Surprisingly, it was found that ligand-activated EGFR induced the expression of a large group of genes known to be inducible by interferons. Expression of this module was absent in the EGFRvIII-expressing cell line and the parental cell line. Treatment with the specific EGFR inhibitor AG1478 indicated that the regulations were primary, receptor-mediated events. Furthermore, activation of this module correlated with activation of STAT1 and STAT3. The results thus demonstrate that ligand-activated EGFR at different expression levels results in different kinetics of signaling and induction of gene expression. In addition, the constitutively active variant EGFRvIII seems to activate only a subset of signal pathways and induce a subset of genes as compared to the ligand-activated EGFR.

Differential response to gefitinib of cells expressing normal EGFR and the mutant EGFRvIII

Epidermal growth factor receptor (EGFR) is frequently amplified and/or mutated in a number of human tumours and abnormal signalling from this receptor is believed to contribute to the malignant phenotype seen in these tumours. Gefitinib is a small molecule inhibitor that specifically binds and inhibits the EGFR tyrosine kinase and has been shown to inhibit the growth, proliferation, survival and invasion of a range of tumour cells overexpressing EGFR. However, clinical response to gefitinib has failed to correlate with EGFR levels and activity, indicating that other molecular mechanisms such as downstream signalling and mutations could be of importance in predicting clinical response. We therefore investigated the effect of the specific EGFR inhibitor gefitinib on the phosphorylation level, signalling and growth of cells expressing the naturally occurring constitutively active EGFR variant EGFRvIII, a low nontransforming level of EGFR and a high transforming level of EGFR. Results show that levels of gefitinib sufficient to suppress EGFR phosphorylations, EGFR-mediated proliferation and EGFR-mediated anchorage-independent growth are not sufficient to inhibit these features in cells expressing EGFRvIII. Furthermore, the data indicate that long-term exposure of EGFRvIII-expressing cells to low concentrations of gefitinib (0.01–0.1 μM) result in increased phosphotyrosine load of the receptor, increased signalling to ERK and stimulation of proliferation and anchorage-independent growth, presumably by inducing EGFRvIII dimerisation. Higher concentrations of gefitinib (1–2 μM), on the other hand, significantly decreased EGFRvIII phosphotyrosine load, EGFRvIII-mediated proliferation and anchorage-independent growth. Further studies are needed to investigate the implications of these important findings in the clinical setting.

Solid lipid nanoparticles can effectively bind DNA, streptavidin and biotinylated ligands

Cationic solid lipid nanoparticles (SLN) have recently been suggested for non-viral gene delivery, as these particles consist of well tolerated substances, can bind DNA directly via electrostatic interactions and mediate gene transfer in vitro. We here report the development of SLN complexes, which can be targeted to specific surface receptors. A formulation of SLN was prepared by the microemulsion technique comprising of stearylamine and the matrix lipid Compritol ATO 888 with a size of approximately 100 nm and a zeta-potential of +15. These SLN are able to condense DNA in complexes, which are very stable under physiological conditions, and they display low cytotoxicity in cell culture. In addition to binding of DNA, the SLN can simultaneously bind substantial amounts of streptavidin directly via electrostatic interactions. The SLN:DNA: streptavidin complexes are stable and are capable of binding biotinylated ligands, which can interact with surface receptors. This method allows for development of a fast and simple method of preparing a targeted non-viral gene therapy vector.

Specific sensitivity of small cell lung cancer cell lines to the snake venom toxin taipoxin

Small cell lung cancer (SCLC) is a malignant disease, for which no satisfactory treatment is presently available and consequently, new specific therapeutic targets are in high demand. A global gene expression analysis previously performed, identified the neuronal pentraxin receptor (NPR) as highly and relatively specifically expressed in SCLC, consistent with the neuroendocrine features of this cancer. Normally, NPR is exclusively expressed in neurons, where it associates with the homologous proteins neuronal pentraxins 1 and 2 (NP1 and NP2) in complexes capable of binding the snake venom neurotoxin taipoxin. The purpose of the present study was to assess the toxic effect of taipoxin in SCLC-cell lines and to determine if toxicity correlates to NPR and NP1 and NP2 expression levels. NPR was detected by Western blot analysis in all the tested SCLC and in control cell lines of different origin. The receptor co-purified with cell membrane in SCLC, indicating that NPR is surface associated. Microarray signals for NP1 and NP2mRNA was detected in a subset of SCLC-cell lines and validated by Northern blot analysis. Furthermore, NP1 protein was detected by Western blot analysis in a few SCLC-cell lines, but not in the control cell lines. A number of SCLC-cell lines showed marked sensitivity to taipoxin (IC50: 3-130 nM) at toxin concentrations leaving the control cell lines unaffected. The sensitivity to taipoxin did not correlate with the expression levels of NP1 protein and NP2-mRNA, suggesting that expression of these proteins may not be required for taipoxin induced toxicity in SCLC. The demonstrated toxic effect of taipoxin in SCLC may prove to be of importance for designing novel specific treatment modalities for this disease.

The insulinoma-associated 1: a novel promoter for targeted cancer gene therapy for small-cell lung cancer

The insulinoma-associated 1 (INSM1) gene is expressed exclusively during early embryonal development, but has been found re-expressed at high levels in neuroendocrine tumors. The regulatory region of the INSM1 gene is therefore a potential candidate for regulating expression of a therapeutic gene in transcriptionally targeted cancer gene therapy against neuroendocrine tumors. We analyzed expression of a reporter gene from a 1.7 kb region of the INSM1 promoter in a large number of small-cell lung cancer (SCLC) cell lines. This INSM1 promoter region showed very high levels of expression in most of the SCLC cell lines and expression was absent in cell lines of non-neuroendocrine origin. Inclusion of the general transcriptional enhancer from SV40 compromised the specificity of the promoter and did not enhance transcription in most of the SCLC cell lines. For comparison, the region of the gastrin releasing peptide (GRP) previously suggested for SCLC gene therapy was analyzed in a similar manner. High expression was observed for a number of cell lines, but unlike for the INSM1 promoter, reporter gene expression from the GRP promoter did not correlate to the relative GRP mRNA levels, demonstrating that this region may not contain all necessary regulatory elements. Expression of the suicide gene herpes simplex virus thymidine kinase (HSV-TK) from the INSM1 promoter in combination with treatment with the prodrug ganciclovir (GCV) caused a significant increase in GCV sensitivity specifically in INSM1-expressing cell lines. The INSM1 promoter is therefore a potential novel tool for transcriptionally targeted gene therapy for neuroendocrine tumors.

Replacement and Suicide Gene Therapy for Targeted Treatment of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the developed world; consequently, novel therapeutic strategies are in high demand. A major problem with the present treatment modalities is the lack of tumor specificity giving rise to dose-limiting toxicity and side effects. Gene therapy constitutes an experimental approach gaining increased attention as a putative future cancer therapeutic strategy. Using this strategy, cancer cytotoxicity can be obtained by replacing mutated genes with functional analogues or introducing a suicide gene into the malignant cells. Insight into the molecular biology of cancer cells has identified a number of regulatory gene sequences, which can be used to selectively activate the therapeutic gene specifically in cancer cells, thereby reducing nonspecific toxicity. Although further improvements are necessary, recent encouraging results have shown promise for future clinical application of gene therapy. This article presents an update on the experimental and clinical results obtained within the field of lung cancer gene therapy, concentrating on strategies to specifically activate expression of the therapeutic gene in cancer cells. Furthermore, status of the development of delivery vector constructs for lung cancer gene therapy will be presented.

Expression of a naturally occurring constitutively active variant of the epidermal growth factor receptor in mouse fibroblasts increases motility

Tumor cell motility is one of the rate-limiting steps of invasion, which defines progression toward a more malignant phenotype. Elevated expression of epidermal growth factor receptor (EGFR) in many cancers is associated with progression of superficial to invasive forms of the disease. The naturally occuring type III mutant epidermal growth factor receptor (EGFRvIII) is a tumor-specific, ligand-independent, constitutively active variant of the epidermal growth factor receptor. EGFRvIII is expressed frequently by a number of human solid tumours including those of the lung, breast, prostate, brain and ovary. Our study was designed to investigate the effect of EGFRvIII expression on cell motility and compare it to that of ligand-activated EGFR using transfected fibroblasts. We show here using time-lapse video recording that expression of EGFRvIII greatly enhances the motility of fibroblasts independently of ligand stimulation. In addition, expression of EGFRvIII caused a marked increase in the number of cellular protrusions (lamellipodia) and a reduction in the number of stress fibers and focal adhesions. The EGFR tyrosine kinase inhibitor, AG1478, and the MEK inhibitor, U0126, blocked these cellular effects of EGFRvIII. Two cell lines expressing different levels of EGFR were used for comparison. The low-expressing cell line responded to EGF treatment by increasing motility in a manner very similar to the motility induced by EGFRvIII. In contrast, the high-expressing cell line responded to EGF by detachment from the extracellular matrix and decreased motility. Cellular detachment was correlated to a high phosphorylation of PLC-gamma, whereas increased motility was correlated to a high level of ERK phosphorylation. Overall these results indicate that tumor-associated EGFR mutations might be critical for tumor cell motility, invasion and thus progression of disease.

Biglycan deficiency interferes with ovariectomy-induced bone loss

Biglycan is a matrix proteoglycan with a possible role in bone turnover. In a 4-week study with sham-operated or OVX biglycan-deficient or wildtype mice, we show that biglycan-deficient mice are resistant to OVX-induced trabecular bone loss and that there is a gender difference in the response to biglycan deficiency.

INTRODUCTION

Biglycan (bgn) is a small extracellular matrix proteoglycan enriched in skeletal tissues, and biglycan-deficient male mice have decreased trabecular bone mass and bone strength. The purpose of this study was to investigate the bone phenotype of the biglycan-deficient female mice and to investigate the effect of estrogen depletion by ovariectomy (OVX).

MATERIALS AND METHODS

OVX or sham operations were performed on 21-week-old mice that were divided into four groups: wt sham (n = 7), wt OVX (n = 9), bgn-deficient sham (n = 10) and bgn-deficient OVX (n = 10). The mice were killed 4 weeks after surgery. Bone mass and bone turnover were analyzed by peripheral quantitative computed tomography (pQCT), biochemical markers, and histomorphometry.

RESULTS AND CONCLUSIONS

In contrast to the male mice, there were only few effects of bgn deficiency on bone metabolism in female mice, showing a clear gender difference. However, when stressed by OVX, the female bgn knockout (KO) mice were resistant to the OVX-induced trabecular bone loss. The wt mice showed a decrease in trabecular bone mineral density by pQCT measurements, a decrease in trabecular bone volume (BV/TV), and an increase in mineral apposition rate. In contrast, no significant changes were detected in bgn KO mice after OVX. In addition, analysis of the bone resorption marker deoxypyridinoline showed no significant increase in the bgn KO OVX mice compared with bgn KO sham mice. Measurements of serum osteoprotegerin (OPG) and RANKL revealed increased levels of OPG and decreased levels of RANKL in the bgn KO mice compared with wt mice. In conclusion, the bgn deficiency protects against increased trabecular bone turnover and bone loss in response to estrogen depletion, supporting the concept that bgn has dual roles in bone, where it may modulate both formation and resorption ultimately influencing the bone turnover process.

Assessment of the hypothalamo-pituitary-adrenal axis in patients treated with radiotherapy and chemotherapy for childhood brain tumor

The impact of cranial irradiation (CIR) and chemotherapy on the hypothalamo-pituitary (HP)-adrenal (HPA) axis was assessed in a population-based follow-up study of patients treated for childhood brain tumor not directly involving the HP axis. HPA function was evaluated and compared with that in healthy controls (n = 17), measuring basal cortisol and the peak cortisol response to an insulin tolerance test (ITT) and an ACTH test(.) The cortisol cut-off level was 500 nmol/liter. The biological effective dose (BED) of radiotherapy was determined for the HP region and spine and was expressed in Gray units, as BED gives a means of expressing the biological effects of different dosage schedules in a uniform way. Seventy-three children (46 males and 27 females), less than 15 yr of age when diagnosed during 1970-1997 in the Eastern part of Denmark, were included. The median age at time of radiotherapy was 8.4 yr (range, 0.8-14.9). The median length of follow-up was 15 yr (range, 2-29). Fourteen patients (19%) had basal cortisol levels below 500 nmol/liter and did not respond with a peak cortisol above the cut-off level to either an ACTH test (30 or 60 min) or an ITT, and thus, they had insufficiency of the HPA axis. Even though a peak cortisol above 500 nmol/liter was reached in the rest of the cohort (n = 59) after either an ACTH test (30 or 60 min) or an ITT, they had significantly lower peak cortisol levels compared with controls (P = 0.0099). Thirteen patients failed the ACTH test (30 min), but passed the ACTH test (60 min), implying a risk of misinterpreting the cortisol capacity of the patient if only the ACTH test (30 min) is obtained. The basal cortisol levels and the cortisol levels in the ACTH test (30 min) and the ACTH test (60 min) were significantly lower in the patient group compared with controls. There was a significant correlation between the peak cortisol after the ITT compared with the peak cortisol after the ACTH test (30 or 60 min; r(s) = 0.56; P = 0.0006), but 48% failed the ITT, and there was discordance in 10 of 33 (30%) patients who passed the ACTH but failed the ITT, indicating the recommendation of continuous use of the ITT as the gold standard for evaluation of the HPA axis. Stepwise backward multiple linear regression analysis showed that the best-fit model to predict the peak cortisol level after an ITT included BED (P = 0.04) and length of follow-up (P = 0.06). In contrast, age at RT, chemotherapy, BED to the spine, and gender were not included in the model. In conclusion, these data suggest that CIR for a childhood brain tumor may affect the HPA axis, resulting in secondary adrenal insufficiency, whereas adjuvant chemotherapy does not seem to add to the deleterious effect of CIR. We recommend life-long surveillance of the HPA axis and performing regular ITTs.