Genetic modification of mesenchymal stem cells to express a single‐chain antibody against EGFRvIII on the cell surface

Human adult mesenchymal stem cells (hMSCs) are under active investigation as cellular carriers for gene therapy. hMSCs possess natural tropism toward tumours; however, the targeting of hMSCs to specific cell populations within tumours is unexplored. In the case of glioblastoma multiforme (GBM), at least half of the tumours express EGFRvIII on the cell surface, an ideal target for antibody‐mediated gene/drug delivery. In this study, we investigated the feasibility of genetically modifying hMSCs to express a single‐chain antibody (scFv) to EGFRvIII on their surfaces. Nucleofection was used to transfect hMSCs with cDNA encoding scFv EGFRvIII fused with PDGFR or human B7‐1 transmembrane domains. The expression of scFv EGFRvIII on the cell surface was assessed by FACS. A stable population of scFv EGFRvIII‐expressing hMSCs was selected, based on antibiotic resistance, and enriched using FACS. We found that nucleofection allows the efficient expression of scFv EGFRvIII on the cell surface of hMSCs. hMSCs transfected with the construct encoding scFv EGFRvIII as a fusion with PDGFRtm showed scFv EGFRvIII expression in up to 86% of cells. Most importantly, human MSCs expressing scFv against EGFRvIII demonstrated enhanced binding to U87‐EGFRvIII cells in vitro and significantly increased retention in human U87‐EGFRvIII‐expressing tumours in vivo. In summary, we provide the first conclusive evidence of genetic modification of hMSCs with a single‐chain antibody against an antigen expressed on the surface of tumour cells, thereby opening up a new venue for enhanced delivery of gene therapy applications in the context of malignant brain cancer. Copyright © 2009 John Wiley & Sons, Ltd.     

The type III epidermal growth factor receptor mutation

Mutations in the epidermal growth factor receptor occur frequently ina number of human tumours including gliomas, non-small-cell lungcarcinomas, ovarian carcinomas and prostate carcinomas. The type IIIepidermal growth factor receptor mutation (variously named EGFRvIII,de2-7 EGFR or EGFR), which lacks a portion of the extracellularligand binding domain, is the most common. Here, we review the currentstatus with regard to the role of EGFRvIII in human cancers. A detaileddiscussion of the formation of EGFRvIII and its structure at the proteinlevel are likewise included along with a discussion of its morefunctional roles. The design and use (preclinical and clinical) of smallmolecule inhibitors, antibodies, and antisense oligonucleotides againstwild-type EGFR are considered in detail as these strategies can bedirectly adapted to target EGFRvIII. Finally, the status of EGFRvIIItargeted therapy is reviewed.     

Editor's choice: A phase II,multicenter trial of rindopepimut (CDX-110) in newly diagnosed glioblastoma: the ACT III study

Background

The epidermal growth factor receptor variant III deletion mutation, EGFRvIII, is expressed in ∼30% of primary glioblastoma and linked to poor long-term survival. Rindopepimut consists of the unique EGFRvIII peptide sequence conjugated to keyhole limpet hemocyanin. In previous phase II trials (ACTIVATE/ACT II), rindopepimut was well tolerated with robust EGFRvIII-specific immune responses and promising progression-free and overall survival. This multicenter, single-arm phase II clinical trial (ACT III) was performed to confirm these results.

Methods

Rindopepimut and standard adjuvant temozolomide chemotherapy were administered to 65 patients with newly diagnosed EGFRvIII-expressing (EGFRvIII+) glioblastoma after gross total resection and chemoradiation.

Results

Progression-free survival at 5.5 months (∼8.5 mo from diagnosis) was 66%. Relative to study entry, median overall survival was 21.8 months, and 36-month overall survival was 26%. Extended rindopepimut vaccination (up to 3.5+ years) was well tolerated. Grades 1–2 injection site reactions were frequent. Anti-EGFRvIII antibody titers increased ≥4-fold in 85% of patients, and increased with duration of treatment. EGFRvIII was eliminated in 4/6 (67%) tumor samples obtained after >3 months of therapy.

Conclusions

This study confirms, in a multicenter setting, the preliminary results seen in previous phase II trials of rindopepimut. A pivotal, double-blind, randomized, phase III trial (“ACT IV”) is under way.     

Retargeted human avidin-CAR T cells for adoptive immunotherapy of EGFRvIII expressing gliomas and their evaluation via optical imaging

There has been significant progress in the design of chimeric antigen receptors (CAR) for adoptive immunotherapy targeting tumor-associated antigens. However, the challenge of monitoring the therapy in real time has been continually ignored. To address this issue, we developed optical molecular imaging approaches to evaluate a recently reported novel CAR strategy for adoptive immunotherapy against glioma xenografts expressing EGFRvIII. We initially biotinylated a novel anti-EGFRvIII monoclonal antibody (biotin-4G1) to pre-target EGFRvIII⁺ gliomas and then redirect activated avidin-CAR expressing T cells against the pre-targeted biotin-4G1. By optical imaging study and bio-distribution analysis, we confirmed the specificity of pre-target and target and determined the optimal time for T cells adoptive transfer in vivo. The results showed this therapeutic strategy offered efficient therapy effect to EGFRvIII⁺ glioma-bearing mice and implied that optical imaging is a highly useful tool in aiding in the instruction of clinical CAR-T cells adoptive transfer in future.     

稳定表达EGFRvIII的U87MG细胞株的建立与鉴定

目的:构建稳定表达表皮生长因子受体Ⅲ型突变体(EGFRvⅢ)的U87MG细胞株。方法:采用电转染方法将pcD-NA4/TO-EGFRvⅢ质粒导入U87MG细胞,加入zeocin筛选,进一步将细胞有限稀释并克隆化培养以建立稳定的转染细胞株。应用RT-PCR、Western blot及细胞免疫荧光染色方法鉴定稳定表达EGFRvⅢ基因的细胞株。结果:经RT-PCR鉴定发现V6号和V24号单克隆细胞株EGFRvⅢ基因mRNA水平高表达,进一步Western blot及细胞免疫荧光染色方法鉴定发现V6号细胞株EGFRvⅢ蛋白水平高表达。结论:成功建立了稳定表达EGFRvⅢ的U87MG细胞株,为进一步的抗肿瘤治疗及其机制研究提供基础。     

Fluorine‐18 labelling of a series of potential EGFRvIII targeting peptides with a parallel labelling approach using [18F]FPyME

There is growing interest in the use of radiolabelled peptides as receptor targeting agents for diagnostic imaging of various cancer types using positron emission tomography. In this work, 1‐[3‐(2‐[¹⁸F]fluoropyridin‐3‐yloxy)propyl]pyrrole‐2,5‐dione ([¹⁸F]FPyME) has been used for parallel fluorine‐18 labelling of PEPHC1, a peptide selective towards the cancer‐specific mutation of the epidermal growth factor receptor (EGFRvIII), and a number of truncated and mutated analogues. Conjugation of the peptides with [¹⁸F]FPyME was achieved within 10 min in non‐decay‐corrected radiochemical yields of 30–50%. The high yield of the conjugation reaction combined with its short synthesis time allows the labelling of several peptides from a single batch of [¹⁸F]FPyME. Copyright © 2010 John Wiley & Sons, Ltd.     

JAK2/STAT3 targeted therapy suppresses tumor invasion via disruption of the EGFRvIII/JAK2/STAT3 axis and associated focal adhesion in EGFRvIII-expressing glioblastoma

Background

As a commonly mutated form of the epidermal growth factor receptor, EGFRvIII strongly promotes glioblastoma (GBM) tumor invasion and progression, but the mechanisms underlying this promotion are not fully understood.

Methods

Through gene manipulation, we established EGFRvIII-, wild-type EGFR-, and vector-expressing GBM cells. We used cDNA microarrays, bioinformatics analysis, target-blocking migration and invasion assays, Western blotting, and an orthotopic U87MG GBM model to examine the phenotypic shifts and treatment effects of EGFRvIII expression in vitro and in vivo. Confocal imaging, co-immunoprecipitation, and siRNA assays detected the focal adhesion-associated complex and their relationships to the EGFRvIII/JAK2/STAT3 axis in GBM cells.

Results

The activation of JAK2/STAT3 signaling is vital for promoting migration and invasion in EGFRvIII-GBM cells. AG490 or WP1066, the JAK2/STAT3 inhibitors, specifically destroyed EGFRvIII/JAK2/STAT3-related focal adhesions and depleted the activation of EGFR/Akt/FAK and JAK2/STAT3 signaling, thereby abolishing the ability of EGFRvIII-expressing GBM cells to migrate and invade. Furthermore, the RNAi silencing of JAK2 in EGFRvIII-expressing GBM cells significantly attenuated their ability to migrate and invade; however, as a result of a potential EGFRvIII-JAK2-STAT3 activation loop, neither EGFR nor STAT3 knockdown yielded the same effects. Moreover, AG490 or JAK2 gene knockdown greatly suppressed tumor invasion and progression in the U87MG-EGFRvIII orthotopic models.

Conclusion

Taken together, our data demonstrate that JAK2/STAT3 signaling is essential for EGFRvIII-driven migration and invasion by promoting focal adhesion and stabilizing the EGFRvIII/JAK2/STAT3 axis. Targeting JAK2/STAT3 therapy, such as AG490, may have potential clinical implications for the tailored treatment of GBM patients bearing EGFRvIII-positive tumors.     

Construction and Periplasmic Expression of the Anti-EGFRvIII ScFv Antibody Gene in Escherichia coli

In the previous study, we constructed an expression vector carrying the anti-EGFRvIII scFv antibody gene with V_H-linker-V_L orientation. The proteins were successfully produced in the periplasmic space of Escherichia coli. In this study, we substituted the inserted DNA with V_L-linker-V_H orientation of the anti-EGFRvIII scFv gene and analyzed its expression in E. coli. The DNA fragment was amplified from its cloning vector (pTz-rscFv), subsequently cloned into a previous expression vector containing the pelB signal sequence and his-tag, and then transformed into E. coli TOP10. The recombinant plasmids were characterized by restriction, PCR, and DNA sequencing analyses. The new anti-EGFRvIII scFv antibody proteins have been successfully expressed in the periplasmic compartment of E. coli Nico21(DE3) using 0.1 mM final concentration of IPTG induction. Total proteins, soluble periplasmic and cytoplasmic proteins, solubilized inclusion bodies, and extracellular proteins were analyzed by SDS-PAGE and Western Blot analyses. The results showed that soluble scFv proteins were found in all fractions except from the cytoplasmic space.