Abstract 1561: AJAP1 is dysregulated at an early stage of gliomagenesis and suppresses invasion through cytoskeleton reorganization

Background

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults and is a leading cause of cancer-related death due to its invasive nature. Despite advances in radiation and chemotherapy following surgical resection of the tumor, the prognosis of GBM remains poor with an average survival time of less than one year. Accumulating evidence indicates the existence of tumor suppressor-like genes encoded on the 1p36 region. Recent investigations have reported Adherens Junctional Associated Protein-1 (AJAP1, also known as Shrew1) as another tumor suppressor-like gene on chromosome 1 in the 1p36 region. We and others also demonstrated that the AJAP1 promoter was highly methylated in a wide spectrum of glioma cell lines, and the loss of expression was associated with poorer survival in gliomas patients. However, the altered expression profiles of AJAP1 in gliomas as well as the underlying mechanisms of AJAP1 on glial cell migration and invasion are still poorly understood.

Methods

The gene profiles of AJAP1 in glioma patients were studied among four independent cohorts. Confocal imaging was used to analyze the AJAP1 localization. After AJAP1 over-expression in GBM cell lines, cellular polarity, cytoskeleton distribution, and anti-tumor effect were investigated in vitro and in vivo.

Results

AJAP1 expression was significantly decreased in gliomas compared with normal brain in REMBRANDT and CGCA cohorts. Additionally, low AJAP1 expression was associated with worse survival in GBMs in REMBRANDT and TCGA U133A cohorts and was significantly associated with classical and mesenchymal subtypes of GBMs among four cohorts. Confocal imaging indicated AJAP1 localized in cell membranes in low-grade gliomas and AJAP1 over-expressing GBM cells, but difficult to assess in high-grade gliomas due to its absence. AJAP1 over-expression altered the cytoskeleton and cellular morphology in vitro, and inhibited the tumor growth in vivo. Conclusion

In summary, gene profiling of gliomas showed that dysregulated AJAP1 exists in the early stage of gliomagenesis. In particular, AJAP1 expression is associated with low and high tumor grades, as well as the clinical outcome of patients with GBMs. Its over-expression predicts poor clinical outcome and may serve as a promising biomarker for intensive therapy, especially in Classical and Mesenchymal GBM patients. Few studies have investigated the function of AJAP1 and cytoskeleton regulation in gliomas. Further studies are warranted to explore the biological functions of AJAP1 that may improve our understanding of the initiation of gliomas and development of new biomarker and therapeutic target for individualized therapy of GBM.

Citation Format: Lei Han, Kai-Liang Zhang, Jun-Xia Zhang, Liang Zeng, Chun-Hui Di, Brian Fee, Miriam Rivas, Tao Jiang, Darrell Bigner, Chun-Sheng Kang, David Cory Adamson. AJAP1 is dysregulated at an early stage of gliomagenesis and suppresses invasion through cytoskeleton reorganization. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1561. doi:10.1158/1538-7445.AM2014-1561

AJAP1 is dysregulated at an early stage of gliomagenesis and suppresses invasion through cytoskeleton reorganization

AIMS

Down-regulation of AJAP1 in glioblastoma multiforme (GBM) has been reported. However, the expression profiles of AJAP1 in gliomas and the underlying mechanisms of AJAP1 function on invasion are still poorly understood.

METHODS

The gene profiles of AJAP1 in glioma patients were studied among four independent cohorts. Confocal imaging was used to analyze the AJAP1 localization. After AJAP1 overexpression in GBM cell lines, cellular polarity, cytoskeleton distribution, and antitumor effect were investigated in vitro and in vivo.

RESULTS

AJAP1 expression was significantly decreased in gliomas compared with normal brain in REMBRANDT and CGCA cohorts. Additionally, low AJAP1 expression was associated with worse survival in GBMs in REMBRANDT and TCGA U133A cohorts and was significantly associated with classical and mesenchymal subtypes of GBMs among four cohorts. Confocal imaging indicated AJAP1 localized in cell membranes in low-grade gliomas and AJAP1-overexpressing GBM cells, but difficult to assess in high-grade gliomas due to its absence. AJAP1 overexpression altered the cytoskeleton and cellular polarity in vitro and inhibited the tumor growth in vivo.

CONCLUSIONS

AJAP1 is dysregulated at an early stage of gliomagenesis and may suppress glioma cell invasion and proliferation, which suggests that AJAP1 may be a potential diagnostic and prognostic marker for gliomas.

Abstract 1177: The mutational status of the p53 tumor suppressor gene is a determinant of GSTP1 expression and mediates GSTP1-dependent drug resistance in human glioblastoma

Mutations in the p53 tumor suppressor gene, a transcription factor activated by a variety of cellular stresses, including, those inflicted by anti-cancer agents, is a common genetic abnormality in GBMs. Although, p53 is involved in critical cellular processes, such as, cell cycle arrest, DNA repair and apoptosis, studies of p53 in tumor drug resistance and/or patient response to therapy have yielded mixed results. Thus, in gliomas and other cancers, such as, breast, bladder, and ovarian carcinomas, some studies have associated wild-type p53 with higher tumor drug resistance, while other studies indicate that mutant or functionally inactive p53, rather than wt p53, confers drug resistance. These observations indicate the significant complexity of the role of p53 in tumor response to therapy and suggest that other factors, including, downstream p53 pathways and/or regulation, may be important determinants of the p53 effects on the tumor drug resistance phenotype. We previously reported that the human GSTP1 gene, that encodes a major drug metabolizing protein, cell signaling regulator and a mediator of tumor drug resistance, is transcriptionally activated by p53 via a canonical p53 binding motif located in intron 4 of the GSTP1 gene. Our goal, in this study, is to gain further insight into the relationship between p53-dependent transcriptional control of GSTP1 in GBM and the extent to which it contributes to GSTP1 expression in primary patient tumor and, ultimately, to their response to therapy. For this, we sequenced the p53 gene across exons 2-11 in 42 primary GBM specimens quantified the level of GSTP1 gene expression by RNA-PCR and genotyped the allelic variants in them. The results showed, approx. half of the tumors to harbor wild-type p53. In those with mutant p53, the mutations spanned the entire p53 target region, the majority in the core DNA binding domain with the hot spots in codons 55, 72, 175, 245, 248, and 273. GSTP1 expression was significantly heterogeneous between the tumors, and with a few exceptions, correlated directly with the presence of wild-type p53. In representative tumors, the high GSTP1 gene expression was associated with resistance to cisplatin and temozolomide. These result suggest that, in GBM, transcriptional activation of GSTP1 by wild-type, and some mutant forms of p53, contributes to their resistance to therapy. Supported by NIH grants RO1 CA 153050, RO1CA127872, RO1 CA 112519, P50CA108786 and P30-CA14236.

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 1177. doi:1538-7445.AM2012-1177

Phase I trial of vendetanib and oral etoposide for recurrent malignant gliomas

e13016

Background: Recurrent malignant gliomas have a poor prognosis, with a median survival of 6–15 months, with grade 4 glioblastomas more aggressive than grade 3 anaplastic astrocytomas or oligodendrogliomas. Vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) are critically important in glioma biology. Vandetanib is a multi-kinase inhibitor, predominantly of VEGF and EGF. We report a phase I trial of vandetanib in combination with oral etoposide for recurrent malignant glioma. Methods: Patients with histologically documented recurrent grade 3 or grade 4 malignant glioma were eligible. Patients were treated with daily oral vandetanib and oral etoposide. The trial design was a modified 3 + 3 Phase I design, with the dose levels outlined below. Results: Eighteen patients have been accrued. There was more hematologic toxicity than expected, with 3/6 of the patients enrolled at dose level 1 developing grade 4 neutropenia. There were no DLT's at the -1 dose level. The protocol was amended to decrease the dose of etoposide to 50 mg daily for 21 days, then 7 days off and dose escalation of vandetanib started again at 100 mg daily. Six patients had no dose limiting toxicity at the new dose level 1 of vandetanib 100 mg daily and etoposide 50 mg daily. Dose escalation continues. There has been clinical activity, with patients remaining stable on study for multiple cycles. Conclusions: Vandetanib and oral etoposide appear to interact to produce more marrow toxicity than expected. A phase II trial is planned when the MTD of vandetanib with reduced dose etoposide is determined.

[Table: see text]

No significant financial relationships to disclose.

Tumor-specific peptide vaccination in newly-diagnosed patients with GBM

2529

Background: Despite multimodality approaches, survival with GBM is dismal. Induction of immune responses to suppress the infiltrative, residual component with an easily manufactured and administered immunotherapy has been a theoretical ideal. The epidermal growth factor receptor variant III (EGFRvIII) is a tumor-specific cell surface protein expressed on approximately 40% of GBMs. Methods: Newly-diagnosed GBM patients with a gross-total resection, a KPS ≥70, and EGFRvIII+, after undergoing radiation with concurrent temozolomide without tumor progression, were eligible to receive EGFRvIII peptide vaccination i.d. with GM-CSF. Primary endpoint was safety. Results: Accrual began in 06/14/2004 and is now complete. 19 patients were enrolled. Median follow-up is 18 months. Toxicity was minimal and without evidence of autoimmunity. Humoral and cellular immune responses were generated. Median TTP from surgery in vaccine-treated patients is 12 months (n = 12), comparing favorably with a historical matched unvaccinated cohort (gross total resection without progression during radiation, KPS≥70, EGFRvIII+) that had a median TTP of 7.1 months (n = 39) (p = 0.0058). These results also compared favorably with those reported for concurrent temozolomide and radiation followed by adjuvant temozolomide, with a median TTP of 6.9 months. Median survival in this trial has exceeded 18 months which compares favorably to all published analyses accounting for all known prognostic indicators. Among recurrent tumors evaluated by immunohistochemistry, 100% no longer expressed the EGFRvIII, suggesting immunological activation that eliminated EGFRvIII-expressing cells, as well as one potential mechanism of treatment failure. Conclusions: EGFRvIII peptide vaccination warrants further investigation in a larger randomized clinical trial in patients with EGFRvIII-expressing tumors.

No significant financial relationships to disclose.

High-level production of alpha-particle-emitting (211)At and preparation of (211)At-labeled antibodies for clinical use

In vitro and in vivo studies in human glioma models suggest that the antitenascin monoclonal antibody 81C6 labeled with the 7.2-h-half-life alpha-particle emitter (211)At might be a valuable endoradiotherapeutic agent for the treatment of brain tumors. The purpose of this study was to develop methods for the production of high levels of (211)At and the radiosynthesis of clinically useful amounts of (211)At-labeled human/mouse chimeric 81C6 antibody.

METHODS

(211)At was produced through the (209)Bi(alpha, 2n)(211)At reaction using an internal target system and purified by a dry distillation process. Antibody labeling was accomplished by first synthesizing N-succinimidyl 3-[(211)At]astatobenzoate from the corresponding tri-n-butyl tin precursor and reacting it with the antibody in pH 8.5 borate buffer. Quality control procedures consisted of methanol precipitation, size-exclusion high-performance liquid chromatography (HPLC), and pyrogen and sterility assays, as well as determination of the immunoreactive fraction by a rapid procedure using a recombinant tenascin fragment coupled to magnetic beads.

RESULTS

A total of 16 antibody labeling runs were performed. Using beam currents of 50-60 microA alpha-particles and irradiation times of 1.5-4.5 h, the mean (211)At production yield was 27.75 +/- 2.59 MBq/microA.h, and the maximum level of (211)At produced was 6.59 GBq after a 4-h irradiation at 55 microA. The decay-corrected distillation yield was 67% +/- 16%. The yield for the coupling of the (211)At-labeled active ester to the antibody was 76% +/- 8%. The fraction of (211)At activity that eluted with a retention time corresponding to intact IgG on HPLC was 96.0% +/- 2.5%. All preparations had a pyrogen level of <0.125 EU/mL and were determined to be sterile. The mean immunoreactive fraction for these 16 preparations was 83.3% +/- 5.3%. Radiolysis did not interfere with labeling chemistry or the quality of the labeled antibody product.

CONCLUSION

These results show that it is feasible to produce clinically relevant activities of (211)At-labeled antibodies and have permitted the initiation of a phase I trial of (211)At-labeled chimeric 81C6 administered directly into the tumor resection cavities of brain tumor patients.

Immunotoxins with increased activity against epidermal growth factor receptor vIII-expressing cells produced by antibody phage display

Recombinant immunotoxins are fusion proteins composed of Fv regions of antibodies and bacterial or plant toxins that are being developed for the targeted therapy of cancer. MR1(Fv)-PE38 is a single-chain recombinant immunotoxin that targets a mutant form of the epidermal growth factor receptor (EGFR), EGFRvIII, that is frequently overexpressed in malignant glioblastomas. We have used random complementarity determining region (CDR) mutagenesis to obtain mutants of MR1(Fv) with an increased affinity for EGFRvIII and an increased activity when converted to a recombinant immunotoxin. Initially, nine residues of heavy chain CDR3 were randomly mutagenized, and several mutants with increased binding affinity were isolated. All mutations were located at amino acids 98 and 99, which correspond to a DNA hot spot, a DNA sequence that mutates at high frequency during natural antibody maturation. A specific region of variable region of antibody light chain CDR3 was mutagenized that corresponded to a hot spot and a mutant (MR1-1) with an additional increase in affinity, and cytotoxic activity was isolated. These studies show that targeting hot spots in the CDRs of Fvs is an effective approach to obtaining Fvs with increased affinity. The increased affinity of MR1-1(Fv) makes it an attractive candidate for the targeted therapy of glioblastomas.

Characterization of the binding epitope of the monoclonal antibody DMAb-1 to ganglioside GM2

Several derivatives of ganglioside GM2 were synthesized for mapping of the binding epitope of a monoclonal antibody raised against this ganglioside. The GM2 ganglioside was modified in both the hydrophobic and the hydrophobilic part of the molecule. The synthesized derivatives were characterized with fast atom bombardment mass spectrometry (FAB-MS). Affinity of the monoclonal antibody for the GM2 derivatives was determined by enzyme-linked immunosorbent assay (ELISA) on microtitre plates or by TLC immunostaining. Modifying the GM2 sialic acid by deacetylation or blocking of the carboxyl moiety abolished the binding to the monoclonal antibody while the cleaving of the glycol group on the sialic acid tail led to a 70% reduced binding affinity. Removal of the fatty acid (lyso-GM2) eliminated the binding to the antibody. GM2 derivatives with fatty acid moieties of 8 carbon atoms or less showed almost no reactivity. GM2 with saturated fatty acids 16:0, 18:0 and 20:0 had binding affinity similar to natural GM2, while the 24:0 fatty acid had only half the binding affinity. The results demonstrate the importance of ganglioside fatty acid composition with regard to ligand binding between the monoclonal antibody and its specific ganglioside antigen. Thus, caution must be shown in the application of immunaffinity methods with monoclonal antibodies for the quantitative determination of glycosphingolipids from different tissues.

Regional blood-to-tissue transport in avian sarcoma virus (ASV)-induced brain tumors

Regional blood-to-tissue transport of 14C-alpha-aminoisobutyric acid (AIB) was measured in avian sarcoma virus (ASV)-induced rat brain tumors and expressed as a unidirectional transfer rate constant (K). The magnitude of K was variable and did not correlate with histologic classification or specific features of the tumors, with the possible exception of sarcomas. Averaged mean K was highest for anaplastic astrocytomas and lowest for gemistocytic astrocytomas (GA); however, the range of measurement within the individual tumor classifications (except GA) was broad. K was not consistently related to tumor size or tumor location; choroid plexus and subependymal tumors were exceptions and had higher K values. The averaged mean K of tumor-free brain in the contralateral hemisphere (CBA) was comparable to that of control animals. The averaged mean K in brain adjacent to tumor was greater than in CBA and generally one-third to one-half of the value in tumor periphery, indicating that these tumors affect the permeability characteristics of adjacent brain capillaries. Estimates of the fractional extraction (E) of AIB by the tumors ranged between 0.009 and 0.2; E's in this range indicate that tumor capillaries are not freely permeable to this solute.

Regional blood flow in avian sarcoma virus (ASV)-induced brain tumors

Regional blood flow (F) was measured in avian sarcoma virus (ASV)-induced brain tumors in rats. Blood flow was variable in individual as well as different tumors; tumor F did not correlate with histologic classification, tumor size, central versus peripheral tumor regions, intraparenchymal location, cell density, or specific cytologic characteristics. Low values of F did correlate with tumor necrosis and hydrocephalus; high values of F correlated with tumorous invasion or association with choroid plexus. Mean tumor F was not significantly different from that of the same anatomic, tumor-free brain region of the contralateral hemisphere, but F in brain tissue adjacent to the tumor was depressed significantly. Depression of F was observed in tumor-free cortex and corpus callosum, especially in the hemisphere ipsilateral to the main tumor mass and in those animals with hydrocephalus.

Prevention of glioma induction in rats by simultaneous intracerebral inoculation of avian sarcoma virus plus bacillus Calmette-Guerin cell-wall preparation

Bacillus Calmette-Guerin cell-wall preparation was injected along with avian sarcoma virus in the brains of newborn Fischer 344 rats, and subsequent glioma induction was compared with rats injected with avian sarcoma virus alone. The percentage of glioma induction and survival were found to be directly related to avian sarcoma virus concentration (10(0), 10(-1), 10(-2), and 10(-3)). A significant reduction in glioma induction occurred when BCG cell-wall preparation was injected with 10(-2) ASV concentration. Above that concentration of ASV, the tumor induction was not significantly affected by bacillus Calmette-Guerin cell-wall preparation; below that concentration, the tumor induction was too low with avian sarcoma virus alone to evaluate an effect.