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Summary: The zinc-finger transcription factor GLI2 is frequently amplified in childhood medulloblastoma of the Sonic-hedgehog type (SHH-MB), with or without amplification of NMYC or deletion of TP53. Despite the aggressive tumor behavior, tumorigenesis is not well understood, and adequate mouse models are lacking. Therefore, we generated mice with a GLI2 overexpression under control of the hGFAP-promoter. These mice died within 150 days. The majority only survived until postnatal day 40. They displayed severe cerebellar hypoplasia, cortical malformations, but no brain tumors, except for one out of 23 animals with an undifferentiated hindbrain lesion. Additional loss of p53 did not result in cerebellar tumors, but partially rescued the cerebellar phenotype induced by GLI2 overexpression. Similarly, the combination of GLI2 and NMYC was neither sufficient for the development of SHH-MB. We therefore assume that the development of childhood SHH-MB in mice is either occurring in cellular origins outside the hGFAP-positive lineage or needs additional genetic drivers.

Abstract CREB (cyclic AMP response element binding protein) binding protein (CBP, CREBBP) is a ubiquitously expressed transcription coactivator with intrinsic histone acetyltransferase (KAT) activity. Germline mutations within the CBP gene are known to cause Rubinstein-Taybi syndrome (RSTS), a developmental disorder characterized by intellectual disability, specific facial features and physical anomalies. Here, we investigate mechanisms of CBP function during brain development in order to elucidate morphological and functional mechanisms underlying the development of RSTS. Due to the embryonic lethality of conventional CBP knockout mice, we employed a tissue specific knockout mouse model (hGFAP-cre::CBP Fl/Fl , mutant mouse) to achieve a homozygous deletion of CBP in neural precursor cells of the central nervous system. Our findings suggest that CBP plays a central role in brain size regulation, correct neural cell differentiation and neural precursor cell migration. We provide evidence that CBP is both important for stem cell viability within the ventricular germinal zone during embryonic development and for unhindered establishment of adult neurogenesis. Prominent histological findings in adult animals include a significantly smaller hippocampus with fewer neural stem cells. In the subventricular zone, we observe large cell aggregations at the beginning of the rostral migratory stream due to a migration deficit caused by impaired attraction from the CBP-deficient olfactory bulb. The cerebral cortex of mutant mice is characterized by a shorter dendrite length, a diminished spine number, and a relatively decreased number of mature spines as well as a reduced number of synapses. In conclusion, we provide evidence that CBP is important for neurogenesis, shaping neuronal morphology, neural connectivity and that it is involved in neuronal cell migration. These findings may help to understand the molecular basis of intellectual disability in RSTS patients and may be employed to establish treatment options to improve patients’ quality of life.

The interaction of CNS tumors with infiltrating lymphocytes plays an important role in their initiation and progression and might be related to therapeutic responses. Gene expression-based methods have been successfully used to characterize the tumor microenvironment. However, methylation data are now increasingly used for molecular diagnostics and there are currently only few methods to infer information about the microenvironment from this data type. Using an approach based on differential methylation and principal component analysis, we developed DIMEimmune (Differential Methylation Analysis for Immune Cell Estimation) to estimate CD4+ and CD8+ T cell abundance as well as tumor-infiltrating lymphocytes (TILs) scores from bulk methylation data. Well-established approaches based on gene expression data and immunohistochemistry-based lymphocyte counts were used as benchmarks. The comparison of DIMEimmune to the previously published MethylCIBERSORT and MeTIL algorithms showed an improved correlation with both gene expression-based and immunohistological results across different brain tumor types. Further, we applied our method to large datasets of glioma, medulloblastoma, atypical teratoid/rhabdoid tumors (ATRTs) and ependymoma. High-grade gliomas showed higher scores of tumor-infiltrating lymphocytes than lower-grade gliomas. There were overall only few tumor-infiltrating lymphocytes in medulloblastoma subgroups. ATRTs were highly infiltrated by lymphocytes, most prominently in the MYC subgroup. DIMEimmune-based estimates of TILs were a significant prognostic factor in the overall cohort of gliomas and medulloblastomas, but not within methylation-based diagnostic subgroups. To conclude, DIMEimmune allows for robust estimates of TIL abundance and might contribute to establishing them as a prognostic or predictive factor in future studies of CNS tumors.

In vitro and ex vivo development of novel therapeutic agents requires reliable and accurate analyses of the cell conditions they were preclinical tested for, such as apoptosis. The detection of apoptotic cells by annexin V (AV) coupled to fluorophores has often shown limitations in the choice of the dye due to interference with other fluorescent-labeled cell markers. The SNAP-tag technology is an easy, rapid and versatile method for functionalization of proteins and was therefore used for labeling AV with various fluorophores. We generated the fusion protein AV-SNAP and analyzed its capacity for the specific display of apoptotic cells in various assays with therapeutic agents. AV-SNAP showed an efficient coupling reaction with five different fluorescent dyes. Two selected fluorophores were tested with suspension, adherent and peripheral blood cells, treated by heat-shock or apoptosis-inducing therapeutic agents. Flow cytometry analysis of apoptotic cells revealed a strong visualization using AV-SNAP coupled to these two fluorophores exemplary, which was comparable to a commercial AV-Assay-kit. The combination of the apoptosis-specific binding protein AV with the SNAP-tag provides a novel solid method to facilitate protein labeling using several, easy to change, fluorescent dyes at once. It avoids high costs and allows an ordinary exchange of dyes and easier use of other fluorescent-labeled cell markers, which is of high interest for the preclinical testing of therapeutic agents in e.g. cancer research.

The antigen-specific targeting of autoreactive B cells via their unique B cell receptors (BCRs) is a novel and promising alternative to the systemic suppression of humoral immunity. We generated and characterized cytolytic fusion proteins based on an existing immunotoxin comprising tetanus toxoid fragment C (TTC) as the targeting component and the modified Pseudomonas aeruginosa exotoxin A (ETA') as the cytotoxic component. The immunotoxin was reconfigured to replace ETA' with either the granzyme B mutant R201K or MAPTau as human effector domains. The novel cytolytic fusion proteins were characterized with a recombinant human lymphocytic cell line developed using Transpo-mAb™ technology. Genes encoding a chimeric TTC-reactive immunoglobulin G were successfully integrated into the genome of the precursor B cell line REH so that the cells could present TTC-reactive BCRs on their surface. These cells were used to investigate the specific cytotoxicity of GrB(R201K)-TTC and TTC-MAPTau, revealing that the serpin proteinase inhibitor 9-resistant granzyme B R201K mutant induced apoptosis specifically in the lymphocytic cell line. Our data confirm that antigen-based fusion proteins containing granzyme B (R201K) are suitable candidates for the depletion of autoreactive B cells.

In vitro and ex vivo development of novel therapeutic agents requires reliable and accurate analyses of the cell conditions they were preclinical tested for, such as apoptosis. The detection of apoptotic cells by annexin V (AV) coupled to fluorophores has often shown limitations in the choice of the dye due to interference with other fluorescent-labeled cell markers. The SNAP-tag technology is an easy, rapid and versatile method for functionalization of proteins and was therefore used for labeling AV with various fluorophores. We generated the fusion protein AV-SNAP and analyzed its capacity for the specific display of apoptotic cells in various assays with therapeutic agents. AV-SNAP showed an efficient coupling reaction with five different fluorescent dyes. Two selected fluorophores were tested with suspension, adherent and peripheral blood cells, treated by heat-shock or apoptosis-inducing therapeutic agents. Flow cytometry analysis of apoptotic cells revealed a strong visualization using AV-SNAP coupled to these two fluorophores exemplary, which was comparable to a commercial AV-Assay-kit. The combination of the apoptosis-specific binding protein AV with the SNAP-tag provides a novel solid method to facilitate protein labeling using several, easy to change, fluorescent dyes at once. It avoids high costs and allows an ordinary exchange of dyes and easier use of other fluorescent-labeled cell markers, which is of high interest for the preclinical testing of therapeutic agents in e.g. cancer research. [ABSTRACT FROM AUTHOR]

Germline mutations in the basic helix‐loop‐helix transcription factor 4 (TCF4) cause the Pitt–Hopkins syndrome (PTHS), a developmental disorder with severe intellectual disability. Here, we report findings from a new mouse model with a central nervous system‐specific truncation of Tcf4 leading to severe phenotypic abnormalities. Furthermore, it allows the study of a complete TCF4 knockout in adult mice, circumventing early postnatal lethality of previously published mouse models. Our data suggest that a TCF4 truncation results in an impaired hippocampal architecture affecting both the dentate gyrus as well as the cornu ammonis. In the cerebral cortex, loss of TCF4 generates a severe differentiation delay of neural precursors. Furthermore, neuronal morphology was critically affected with shortened apical dendrites and significantly increased branching of dendrites. Our data provide novel information about the role of Tcf4 in brain development and may help to understand the mechanisms leading to intellectual deficits observed in patients suffering from PTHS. [ABSTRACT FROM AUTHOR]

The TCF4 gene encodes for the basic helix-loop-helix transcription factor 4 (TCF4), which plays an important role in the development of the central nervous system (CNS). Haploinsufficiency of TCF4 was found to cause Pitt-Hopkins syndrome (PTHS), a severe neurodevelopmental disorder. Recently, the screening of a large cohort of medulloblastoma (MB), a highly aggressive embryonal brain tumor, revealed almost 20% of adult patients with MB of the Sonic hedgehog (SHH) subtype carrying somatic TCF4 mutations. Interestingly, many of these mutations have previously been detected as germline mutations in patients with PTHS. We show here that overexpression of wild-type TCF4 in vitro significantly suppresses cell proliferation in MB cells, whereas mutant TCF4 proteins do not to the same extent. Furthermore, RNA sequencing revealed significant upregulation of multiple well-known tumor suppressors upon expression of wild-type TCF4. In vivo, a prenatal knockout of Tcf4 in mice caused a significant increase in apoptosis accompanied by a decreased proliferation and failed migration of cerebellar granule neuron precursor cells (CGNP), which are thought to be the cells of origin for SHH MB. In contrast, postnatal in vitro and in vivo knockouts of Tcf4 with and without an additional constitutive activation of the SHH pathway led to significantly increased proliferation of CGNP or MB cells. Finally, publicly available data from human MB show that relatively low expression levels of TCF4 significantly correlate with a worse clinical outcome. These results not only point to time-specific roles of Tcf4 during cerebellar development but also suggest a functional linkage between TCF4 mutations and the formation of SHH MB, proposing that TCF4 acts as a tumor suppressor during postnatal stages of cerebellar development. [ABSTRACT FROM AUTHOR]

In the original publication, the second name of the twentieth author was incorrect. It should read as ‘Miguel Sáinz-Jaspeado’. The original publication of the article has been updated to reflect the change. This correction was authored by Ulrich Schüller on behalf of all authors of the original publication. [ABSTRACT FROM AUTHOR]

The article discusses a study focusing on the elimination of several leukaemia subtypes using CD89-specific human cytolytic fusion proteins (hCFPs). Topics discussed include the promise shown by antibody-based cancer therapy; the immunotoxins, which have the ability to eliminate tumour cells; and the hCFPs expressed in the study.

Olfactory neuroblastoma/esthesioneuroblastoma (ONB) is an uncommon neuroectodermal neoplasm thought to arise from the olfactory epithelium. Little is known about its molecular pathogenesis. For this study, a retrospective cohort of n = 66 tumor samples with the institutional diagnosis of ONB was analyzed by immunohistochemistry, genome-wide DNA methylation profiling, copy number analysis, and in a subset, next-generation panel sequencing of 560 tumor-associated genes. DNA methylation profiles were compared to those of relevant differential diagnoses of ONB. Unsupervised hierarchical clustering analysis of DNA methylation data revealed four subgroups among institutionally diagnosed ONB. The largest group (n = 42, 64%, Core ONB) presented with classical ONB histology and no overlap with other classes upon methylation profiling-based t-distributed stochastic neighbor embedding (t-SNE) analysis. A second DNA methylation group (n = 7, 11%) with CpG island methylator phenotype (CIMP) consisted of cases with strong expression of cytokeratin, no or scarce chromogranin A expression and IDH2 hotspot mutation in all cases. T-SNE analysis clustered these cases together with sinonasal carcinoma with IDH2 mutation. Four cases (6%) formed a small group characterized by an overall high level of DNA methylation, but without CIMP. The fourth group consisted of 13 cases that had heterogeneous DNA methylation profiles and strong cytokeratin expression in most cases. In t-SNE analysis, these cases mostly grouped among sinonasal adenocarcinoma, squamous cell carcinoma, and undifferentiated carcinoma. Copy number analysis indicated highly recurrent chromosomal changes among Core ONB with a high frequency of combined loss of chromosome 1-4, 8-10, and 12. NGS sequencing did not reveal highly recurrent mutations in ONB, with the only recurrently mutated genes being TP53 and DNMT3A. In conclusion, we demonstrate that institutionally diagnosed ONB are a heterogeneous group of tumors. Expression of cytokeratin, chromogranin A, the mutational status of IDH2 as well as DNA methylation patterns may greatly aid in the precise classification of ONB. [ABSTRACT FROM AUTHOR]

The antigen-specific targeting of autoreactive B cells via their unique B cell receptors (BCRs) is a novel and promising alternative to the systemic suppression of humoral immunity. We generated and characterized cytolytic fusion proteins based on an existing immunotoxin comprising tetanus toxoid fragment C (TTC) as the targeting component and the modified Pseudomonas aeruginosa exotoxin A (ETA') as the cytotoxic component. The immunotoxin was reconfigured to replace ETA' with either the granzyme B mutant R201K or MAPTau as human effector domains. The novel cytolytic fusion proteins were characterized with a recombinant human lymphocytic cell line developed using Transpo-mAb™ technology. Genes encoding a chimeric TTC-reactive immunoglobulin G were successfully integrated into the genome of the precursor B cell line REH so that the cells could present TTC-reactive BCRs on their surface. These cells were used to investigate the specific cytotoxicity of GrB(R201K)-TTC and TTC-MAPTau, revealing that the serpin proteinase inhibitor 9-resistant granzyme B R201K mutant induced apoptosis specifically in the lymphocytic cell line. Our data confirm that antigen-based fusion proteins containing granzyme B (R201K) are suitable candidates for the depletion of autoreactive B cells. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs) can deliver toxins to specific targets such as tumor cells. They have shown promise in preclinical/clinical development but feature stoichiometrically undefined chemical linkages, and those based on full-size antibodies achieve only limited tumor penetration. SNAP-tag technology can overcome these challenges by conjugating benzylguanine-modified toxins to single-chain fragment variables (scFvs) with 1:1 stoichiometry while preserving antigen binding. Two (human and mouse) scFv-SNAP fusion proteins recognizing the epidermal growth factor receptor (EGFR) were expressed in HEK 293T cells. The purified fusion proteins were conjugated to auristatin F (AURIF). Binding activity was confirmed by flow cytometry/immunohistochemistry, and cytotoxic activity was confirmed by cell viability/apoptosis and cell cycle arrest assays, and a novel microtubule dynamics disassembly assay was performed. Both ADCs bound specifically to their target cells in vitro and ex vivo, indicating that the binding activity of the scFv-SNAP fusions was unaffected by conjugation to AURIF. Cytotoxic assays confirmed that the ADCs induced apoptosis and cell cycle arrest at nanomolar concentrations and microtubule disassembly. The SNAP-tag technology provides a platform for the development of novel ADCs with defined conjugation sites and stoichiometry. We achieved the stable and efficient linkage of AURIF to human or murine scFvs using the SNAP-tag technology, offering a strategy to improve the development of personalized medicines. [ABSTRACT FROM AUTHOR]

Immunotoxins are fusion proteins that combine a targeting component such as an antibody fragment or ligand with a cytotoxic effector component that induces apoptosis in specific cell populations displaying the corresponding antigen or receptor. Human cytolytic fusion proteins (hCFPs) are less immunogenic than conventional immunotoxins because they contain human pro-apoptotic enzymes as effectors. However, one drawback of hCFPs is that target cells can protect themselves by expressing endogenous inhibitor proteins. Inhibitor-resistant enzyme mutants that maintain their cytotoxic activity are therefore promising effector domain candidates. We recently developed potent variants of the human ribonuclease angiogenin (Ang) that were either more active than the wild-type enzyme or less susceptible to inhibition because of their lower affinity for the ribonuclease inhibitor RNH1. However, combining the mutations was unsuccessful because although the enzyme retained its higher activity, its susceptibility to RNH1 reverted to wild-type levels. We therefore used molecular dynamic simulations to determine, at the atomic level, why the affinity for RNH1 reverted, and we developed strategies based on the introduction of further mutations to once again reduce the affinity of Ang for RNH1 while retaining its enhanced activity. We were able to generate a novel Ang variant with remarkable in vitro cytotoxicity against HL-60 cells and pro-inflammatory macrophages. We also demonstrated the pro-apoptotic potential of Ang-based hCFPs on cells freshly isolated from leukemia patients. [ABSTRACT FROM AUTHOR]

Antibody-based immunotherapy of leukemia requires the targeting of specific antigens on the surface of blasts. The Fc gamma receptor (CD64) has been investigated in detail, and CD64-targeting immunotherapy has shown promising efficacy in the targeted ablation of acute myeloid leukemia (AML), acute myelomonocytic leukemia (AMML) and chronic myeloid leukemia cells (CML). Here we investigate for the first time the potential of FcαRI (CD89) as a new target antigen expressed by different myeloid leukemic cell populations. For specific targeting and killing, we generated a recombinant fusion protein comprising an anti-human CD89 single-chain Fragment variable and the well-characterized truncated version of the potent Pseudomonas aeruginosa exotoxin A (ETA'). Our novel therapeutic approach achieved in vitro EC50 values in range 0.2-3 nM depending on the applied stimuli, that is, interferon gamma or tumor necrosis factor alpha. We also observed a dose-dependent apoptosis-mediated cytotoxicity, which resulted in the elimination of up to 90% of the target cells within 72 hr. These findings were also confirmed ex vivo using leukemic primary cells from peripheral blood samples of three previously untreated patients. We conclude that CD89-specific targeting of leukemia cell lines can be achieved in vitro and that the efficient elimination of leukemic primary cells supports the potential of CD89-ETA' as a potent, novel immunotherapeutic agent. [ABSTRACT FROM AUTHOR]

Purpose: The epidermal growth factor receptor (EGFR) is overexpressed in many solid tumors. EGFR-specific monoclonal antibodies (mAbs), such as cetuximab and panitumumab, have been approved for the treatment of colorectal and head and neck cancer. To increase tissue penetration, we constructed single-chain fragment variable (scFv) antibodies derived from these mAbs and evaluated their potential for targeted cancer therapy. The resulting scFv-based EGFR-specific immunotoxins (ITs) combine target specificity of the full-size mAb with the cell-killing activity of a toxic effector domain, a truncated version of Pseudomonas exotoxin A (ETA′). Methods: The ITs and corresponding imaging probes were tested in vitro against four solid tumor entities (rhabdomyosarcoma, breast, prostate and pancreatic cancer). Specific binding and internalization of the ITs scFv2112-ETA′ (from cetuximab) and scFv1711-ETA′ (from panitumumab) were demonstrated by flow cytometry and for the scFv-SNAP-tag imaging probes by live cell imaging. Cytotoxic potential of the ITs was analyzed in cell viability and apoptosis assays. Binding of the ITs was proofed ex vivo on rhabdomyosarcoma, prostate and breast cancer formalin-fixed paraffin-embedded biopsies. Results: Both novel ITs showed significant pro-apoptotic and anti-proliferative effects toward the target cells, achieving IC values of 4 pM (high EGFR expression) to 460 pM (moderate EGFR expression). Additionally, rapid internalization and specific in vitro and ex vivo binding on patient tissue were confirmed. Conclusions: These data demonstrate the potent therapeutic activity of two novel EGFR-specific ETA′-based ITs. Both molecules are promising candidates for further development toward clinical use in the treatment of various solid tumors to supplement the existing therapeutic regimes. [ABSTRACT FROM AUTHOR]

Purpose: Rhabdomyosarcoma (RMS) is a rare and aggressive soft tissue sarcoma with limited treatment options and a high failure rate during standard therapy. New therapeutic strategies based on targeted immunotherapy are therefore much in demand. The epidermal growth factor receptor (EGFR) has all the characteristics of an ideal target. It is overexpressed in up to 80 % of embryonal RMS and up to 50 % of alveolar RMS tumors. We therefore tested the activity of the EGFR-specific recombinant immunotoxin (IT) 425(scFv)-ETA′ against EGFR RMS cells in vitro and ex vivo. Methods: We tested the specific binding and internalization behavior of 425(scFv)-ETA′ in RMS cell lines in vitro by flow cytometry, compared to the corresponding imaging probe 425(scFv)-SNAP monitored by live cell imaging. The cytotoxic activity of 425(scFv)-ETA′ was tested using cell viability and apoptosis assays. Specific binding of the IT was confirmed on formalin-fixed paraffin-embedded tissue samples from two RMS patients. Results: We confirmed the specific binding of 425(scFv)-ETA′ to RMS cells in vitro and ex vivo. Both the IT and the corresponding imaging probe were rapidly internalized. The IT killed EGFR RMS cells in a dose-dependent manner, while showing no effect against control cells. It showed specific apoptotic activity against one selected RMS cell line. Conclusions: This is the first study showing the promising therapeutic potential of a recombinant, EGFR-targeting, ETA′-based IT on RMS cells. We confirmed the selective killing with IC values of up to 50 pM, and immunohistochemical staining confirmed the specific ex vivo binding to primary RMS material. [ABSTRACT FROM AUTHOR]

Purpose: The epidermal growth factor receptor (EGFR) is overexpressed in several types of cancer and its inhibition can effectively inhibit tumour progression. The purpose of this study was to design an EGFR-specific imaging probe that combines efficient tumour targeting with rapid systemic clearance to facilitate non-invasive assessment of EGFR expression. Methods: Genetic fusion of a single-chain antibody fragment with the SNAP-tag produced a 48-kDa antibody derivative that can be covalently and site-specifically labelled with substrates containing 0-benzylguanine. The EGFR-specific single-chain variable fragment (scFv) fusion protein 425(scFv)SNAP was labelled with the near infrared (NIR) dye BG-747, and its accumulation, specificity and kinetics were monitored using NIR fluorescence imaging in a subcutaneous pancreatic carcinoma xenograft model. Results: The 425(scFv)SNAP fusion protein accumulates rapidly and specifically at the tumour site. Its small size allows efficient renal clearance and a high tumour to background ratio (TBR) of 33.2 ± 6.3 ( n = 4) 10 h after injection. Binding of the labelled antibody was efficiently competed with a 20-fold excess of unlabelled probe, resulting in an average TBR of 6 ± 1.35 ( n = 4), which is similar to that obtained with a non-tumour-specific probe (5.44 ± 1.92, n = 4). When compared with a full-length antibody against EGFR (cetuximab), 425(scFv)SNAP-747 showed significantly higher TBRs and complete clearance 72 h post-injection. Conclusion: The 425(scFv)SNAP fusion protein combines rapid and specific targeting of EGFR-positive tumours with a versatile and robust labelling technique that facilitates the attachment of fluorophores for use in optical imaging. The same approach could be used to couple a chelating agent for use in nuclear imaging. [ABSTRACT FROM AUTHOR]

CREB (cyclic AMP response element binding protein) binding protein (CBP, CREBBP) is a ubiquitously expressed transcription coactivator with intrinsic histone acetyltransferase (KAT) activity. Germline mutations within the CBP gene are known to cause Rubinstein-Taybi syndrome (RSTS), a developmental disorder characterized by intellectual disability, specific facial features and physical anomalies. Here, we investigate mechanisms of CBP function during brain development in order to elucidate morphological and functional mechanisms underlying the development of RSTS. Due to the embryonic lethality of conventional CBP knockout mice, we employed a tissue specific knockout mouse model (hGFAP-cre::CBPFl/Fl, mutant mouse) to achieve a homozygous deletion of CBP in neural precursor cells of the central nervous system. Our findings suggest that CBP plays a central role in brain size regulation, correct neural cell differentiation and neural precursor cell migration. We provide evidence that CBP is both important for stem cell viability within the ventricular germinal zone during embryonic development and for unhindered establishment of adult neurogenesis. Prominent histological findings in adult animals include a significantly smaller hippocampus with fewer neural stem cells. In the subventricular zone, we observe large cell aggregations at the beginning of the rostral migratory stream due to a migration deficit caused by impaired attraction from the CBP-deficient olfactory bulb. The cerebral cortex of mutant mice is characterized by a shorter dendrite length, a diminished spine number, and a relatively decreased number of mature spines as well as a reduced number of synapses. In conclusion, we provide evidence that CBP is important for neurogenesis, shaping neuronal morphology, neural connectivity and that it is involved in neuronal cell migration. These findings may help to understand the molecular basis of intellectual disability in RSTS patients and may be employed to establish treatment options to improve patients' quality of life. [ABSTRACT FROM AUTHOR]

Background: Single chain antibody (scFv) has shown interesting results in cancer immunotargeting approaches, due to its advantages over monoclonal antibodies. Regeneration and tolerance factor (RTF) is one of the most important regulators of extracellular and intracellular pH in eukaryotic cells. In this study, the inhibitory effects of a specific anti-RTF scFv were investigated and compared between three types of prostate cancer and two types of glioblastoma cells. Methods: A phage antibody display library of scFv was used to select specific scFvs against RTF using panning process. The reactivity of a selected scFv was assessed by phage ELISA. The anti-proliferative and apoptotic effects of the antibody on prostate cancer (PC-3, Du-145 and LNCaP) and glioblastoma (U-87 MG and A-172) cell lines were investigated by MTT and Annexin V/PI assays. Results: A specific scFv with frequency 35% was selected against RTF epitope. This significantly inhibited the proliferation of the prostate cells after 24 h. The percentages of cell viability (using 1000 scFv/cell) were 52, 61 and 73% for PC-3, Du-145 and LNCaP cells, respectively, compared to untreated cells. The antibody (1000 scFv/cell) induced apoptosis at 50, 40 and 25% in PC-3, Du-145 and LNCaP cells, respectively. No growth inhibition and apoptotic induction was detected for U-87 and A172 glioblastoma cells. Conclusions: Anti-RTFscFv significantly reduced the proliferation of the prostate cancer cells. The inhibition of cell growth and apoptotic induction effects in PC-3 cells were greater than Du-145 and LNCaP cells. This might be due to higher expression of RTF antigen in PC-3 cells and/or better accessibility of RTF to scFv antibody. The resistance of glioblastoma cells to anti-RTF scFv offers the existence of mechanism(s) that abrogate the inhibitory effect(s) of the antibody to RTF. The results suggest that the selected anti-RTF scFv antibody could be an effective new alternative for prostate cancer immunotherapy.