FOXP3, a novel glioblastoma oncosuppressor, affects proliferation and migration

Inhibitory co-receptor Lag3 supports Foxp3+ regulatory T cell function by restraining Myc-dependent metabolic programming

Lymphocyte activation gene 3 (Lag3) is an inhibitory co-receptor expressed on activated T cells and has been proposed to regulate regulatory T (Treg) cell function. However, its precise modality and mechanisms remain elusive. We generated Treg cell-specific Lag3-mutant mouse models and found that Lag3 was essential for Treg cell control of autoimmunity. RNA sequencing analysis revealed that Lag3 mutation altered genes associated with metabolic processes, especially Myc target genes. Myc expression in Lag3-mutant Treg cells was increased to the level seen in conventional T helper (Th)1-type effector cells and directly correlated with their metabolic profiles and in vivo suppressive functions. The phosphatidylinositol 3-kinase (PI3K)-Akt-Rictor pathway was activated in Lag3-mutant Treg cells, and inhibiting PI3K, Rictor, or lactate dehydrogenase A (Ldha), a key Myc target enzyme converting pyruvate to lactate, was sufficient to restore normal metabolism and suppressive function in Lag3-mutant Treg cells. These findings indicate that Lag3 supports Treg cell suppression partly by tuning Myc-dependent metabolic programming.

Lymphocyte activation gene 3 (Lag3) supports Foxp3 + Treg cell function by restraining c-Myc-dependent aerobic glycolysis

Lymphocyte activation gene 3 (Lag3) has emerged as the next-generation immune checkpoint molecule due to its ability to inhibit effector T cell activity. Foxp3 + regulatory T (Treg) cells, a master regulator of immunity and tolerance, also highly express Lag3. While Lag3 is thought to be necessary for Treg cell-mediated regulation of immunity, the precise roles and underlying mechanisms remain largely elusive. In this study, we report that Lag3 is indispensable for Treg cells to control autoimmune inflammation. Utilizing a newly generated Treg cell specific Lag3 mutant mouse model, we found that these animals are highly susceptible to autoimmune diseases, suggesting defective Treg cell function. Genome wide transcriptome analysis further uncovered that Lag3 mutant Treg cells upregulated genes involved in metabolic processes. Mechanistically, we found that Lag3 limits Treg cell expression of Myc, a key regulator of aerobic glycolysis. We further found that Lag3-dependent Myc expression determines Treg cells’ metabolic programming as well as the in vivo function to suppress autoimmune inflammation. Taken together, our results uncovered a novel function of Lag3 in supporting Treg cell suppressive function by regulating Myc-dependent metabolic programming.

Age, but Not Sex, Modulates Foxp3 Expression in the Rat Brain across Development

The interconnectivity between brain development and the immune system has become an area of interest for many neuroscientists. However, to date, a limited number of known immune mediators of the peripheral nervous system (PNS) have been found to influence the development of the central nervous system (CNS). FOXP3 is a well-established mediator of regulatory T-cells in the PNS. However, the expression pattern of FOXP3 in the CNS and the PNS throughout development is unknown. To fill this void, we have characterized, in several brain regions, the developmental profile of Foxp3 for both sexes using rats. We found different patterns of Foxp3 in the CNS and PNS. In the CNS, we found Foxp3 was ubiquitously expressed, with the levels of Foxp3 varying by brain region. We also found both Foxp3 mRNA and protein levels peak during embryonic development and then steadily decrease with a peak increase during adulthood. In adulthood, the protein but not mRNA increases to the equivalent levels found at the embryonic stage of life. In the PNS, Foxp3 protein levels were low embryonically and increased steadily over the life of the animal with maximal levels reached in adulthood. Patterns observed for both the PNS and CNS were similar in males and females across all developmental timepoints. Our novel findings have implications for understanding how the neural immune system impacts neurodevelopmental disorders such as autism and schizophrenia.

Blood signatures for second stage human African trypanosomiasis: a transcriptomic approach

BACKGROUND

Rhodesiense sleeping sickness is caused by infection with T. b rhodesiense parasites resulting in an acute disease that is fatal if not treated in time. The aim of this study was to understand the global impact of active T. b rhodesiense infection on the patient's immune response in the early and late stages of the disease.

METHODS

RNASeq was carried out on blood and cerebral spinal fluid (CSF) samples obtained from T. b. rhodesiense infected patients. The control samples used were from healthy individuals in the same foci. The Illumina sequenced reads were analysed using the Tuxedo suite pipeline (Tophat, Cufflinks, Cuffmerge, Cuffdiff) and differential expression analysis carried out using the R package DESeq2. The gene enrichment and function annotation analysis were done using the ToppCluster, DAVID and InnateDB algorithms.

RESULTS

We previously described the transcriptomes of T. b rhodesiense from infected early stage blood (n = 3) and late stage CSF (n = 3) samples from Eastern Uganda. We here identify human transcripts that were differentially expressed (padj < 0.05) in the early stage blood versus healthy controls (n = 3) and early stage blood versus late stage CSF. Differential expression in infected blood showed an enrichment of innate immune response genes whereas that of the CSF showed enrichment for anti-inflammatory and neuro-degeneration signalling pathways. We also identified genes (C1QC, MARCO, IGHD3-10) that were up-regulated (log₂ FC > 2.5) in both the blood and CSF.

CONCLUSION

The data yields insights into the host's response to T. b rhodesiense parasites in the blood and central nervous system. We identified key pathways and signalling molecules for the predominant innate immune response in the early stage infection; and anti-inflammatory and neuro-degeneration pathways associated with sleep disorders in second stage infection. We further identified potential blood biomarkers that can be used for diagnosis of late stage disease without the need for lumbar puncture.

Humanized mice are precious tools for evaluation of hematopoietic gene therapies and preclinical modeling to move towards a clinical trial

Over the last decade, incrementally improved xenograft mouse models, which support the engraftment and development of a human hemato-lymphoid system, have been developed and represent an important fundamental and preclinical research tool. Immunodeficient mice can be transplanted with human hematopoietic stem cells (HSCs) and this process is accompanied by HSC homing to the murine bone marrow. This is followed by stem cell expansion, multilineage hematopoiesis, long-term engraftment, and functional human antibody and cellular immune responses. The most significant contributions made by these humanized mice are the identification of normal and leukemic hematopoietic stem cells, the characterization of the human hematopoietic hierarchy, screening of anti-cancer therapies and their use as preclinical models for gene therapy applications. This review article focuses on several gene therapy applications that have benefited from evaluation in humanized mice such as chimeric antigen receptor (CAR) T cell therapies for cancer, anti-viral therapies and gene therapies for multiple monogenetic diseases. Humanized mouse models have been and still are of great value for the gene therapy field since they provide a more reliable understanding of sometimes complicated therapeutic approaches such as recently developed therapeutic gene editing strategies, which seek to correct a gene at its endogenous genomic locus. Additionally, humanized mouse models, which are of great importance with regard to testing new vector technologies in vivo for assessing safety and efficacy prior toclinical trials, help to expedite the critical translation from basic findings to clinical applications. In this review, innovative gene therapies and preclinical studies to evaluate T- and B-cell and HSC-based therapies in humanized mice are discussed and illustrated by multiple examples.

Genetic association study of promoter variation rs3761549 in the FOXP3 gene of Iranian patients diagnosed with brain tumour

Forkhead box P3 (FOXP3) gene (Gene ID: 50943, Xp11.23) is an X-linked gene that encodes FOXP3 protein, an essential transcription factor in CD4+ CD25+ FOXP3 regulatory T (Treg) cells. FOXP3 mutation has been linked with the pathogenesis of several tumours; however, little is known about the role of single-nucleotide polymorphism (SNP) in its promoter region and its correlation with brain tumour. In the present study, we have investigated the association between SNPs in the promoter region of FOXP3 gene, a promoter SNP, -2383 C/T (rs3761549) with susceptibility to brain cancer in a population of Iran. The distribution of case, control, age and sex was balanced and with rs3761549 C/T allele frequencies distribution also falling in Hardy-Weinberg equilibrium (P = 0.053 and 0.062). The allele C of rs3761549 is lower in the brain tumour cases when compared with the controls (364 vs 392, P = 0.005). The frequency of combined T variant genotype (TT + CT) was significantly higher in the brain cancer cases compared with the controls (28 vs 8, P = 0.001), which was consistent with the T allele distribution. When we used the CC genotype as a reference, we found that both CT and TT genotypes were associated with a higher risk of developing brain tumour (odds ratio [OR], 0.3583; 95% confidence interval [CI], 0.164-0.8197 and OR, 0; 95% CI, 0-0.4118, respectively).

Ectopic FOXP3 Expression Preserves Primitive Features Of Human Hematopoietic Stem Cells While Impairing Functional T Cell Differentiation

FOXP3 is the transcription factor ruling regulatory T cell function and maintenance of peripheral immune tolerance, and mutations in its coding gene causes IPEX autoimmune syndrome. FOXP3 is also a cell-cycle inhibitor and onco-suppressor in different cell types. In this work, we investigate the effect of ectopic FOXP3 expression on HSC differentiation and we challenged this approach as a possible HSC-based gene therapy for IPEX. FOXP3-expressing HSC showed reduced proliferation ability and increased maintenance of primitive markers in vitro in both liquid and OP9-ΔL1 co-cultures. When transplanted into immunodeficient mice, FOXP3-expressing HSC showed significantly enhanced engraftment ability. This was due to a pronounced increase in the frequency of repopulating cells, as assessed by extreme limiting dilution assay. Likely underlying the increased repopulating ability, FOXP3 expressing HSC showed significantly enhanced expression of genes controlling stemness features. However, peripheral T cells developed in the FOXP3-humanized mice were quantitatively reduced and hyporesponsive to cytokine and polyclonal stimulation. Our findings reveal unpredicted effects of FOXP3 in the biology of HSC and may provide new tools to manipulate primitive features in HSC for clinical applications. Moreover, they formally prove the need of preserving endogenous FOXP3 regulation for an HSC-based gene therapy approach for IPEX syndrome.

Downregulation of FOXP3 inhibits cell proliferation and enhances chemosensitivity to cisplatin in human lung adenocarcinoma

Our study aimed to investigate the biological role of FOXP3 expression in human lung adenocarcinoma (LAD) tissues and evaluate its involvement in cell proliferation and chemosensitivity to cisplatin in LAD cells. Paraffin-embedded tissues from 50 LAD patients were collected to detect FOXP3 and Ki-67 expression using immunohistochemistry (IHC). Downregulation of FOXP3 in A549 cells was performed using siRNA transfection. Real-time PCR or western blot assay was performed to analyze FOXP3 expression in A549 cells. Cell proliferation and cisplatin cytotoxicity test were assessed by CCK-8 assay. The expression of FOXP3 was significantly associated with lymph node metastasis and TNM stage of LAD patients. The FOXP3 expression was positively correlated with Ki-67 labelling index(LI)in LAD tissues. The downregulated expression of FOXP3 by siRNA transfection significantly inhibited cell proliferation and enhanced chemosensitivity to cisplatin in A549 cells. The expression of FOXP3 was significantly upregulated following cisplatin treatment in A549 cells. Our study indicates that FOXP3 may potentially be a novel molecular target in combating drug resistance in the chemotherapy of LAD.

Foxp3 Reprograms T Cell Metabolism to Function in Low-Glucose, High-Lactate Environments

Immune cells function in diverse metabolic environments. Tissues with low glucose and high lactate concentrations, such as the intestinal tract or ischemic tissues, frequently require immune responses to be more pro-tolerant, avoiding unwanted reactions against self-antigens or commensal bacteria. T-regulatory cells (Tregs) maintain peripheral tolerance, but how Tregs function in low-glucose, lactate-rich environments is unknown. We report that the Treg transcription factor Foxp3 reprograms T cell metabolism by suppressing Myc and glycolysis, enhancing oxidative phosphorylation, and increasing nicotinamide adenine dinucleotide oxidation. These adaptations allow Tregs a metabolic advantage in low-glucose, lactate-rich environments; they resist lactate-mediated suppression of T cell function and proliferation. This metabolic phenotype may explain how Tregs promote peripheral immune tolerance during tissue injury but also how cancer cells evade immune destruction in the tumor microenvironment. Understanding Treg metabolism may therefore lead to novel approaches for selective immune modulation in cancer and autoimmune diseases.

Hydroquinone-induced FOXP3-ADAM17-Lyn-Akt-p21 signaling axis promotes malignant progression of human leukemia U937 cells

Hydroquinone (1,4-benzenediol; HQ), a major marrow metabolite of the leukemogen benzene, has been proven to evoke benzene-related hematological disorders and myelotoxicity in vitro and in vivo. The goal of the present study was to explore the role of FOXP3 in HQ-induced malignant progression of U937 human leukemia cells. U937 cells were treated with 5 μM HQ for 24 h, and the cells were re-suspended in serum-containing medium without HQ for 2 days. The same procedure was repeated three times, and the resulting U937/HQ cells were maintained in cultured medium containing 5 μM HQ. Proliferation and colony formation of U937/HQ cells were notably higher than those of U937 cells. Ten-eleven translocation methylcytosine dioxygenase-mediated demethylation of the Treg-specific demethylated region in FOXP3 gene resulted in higher FOXP3 expression in U937/HQ cells than in U937 cells. FOXP3-induced miR-183 expression reduced β-TrCP mRNA stability and suppressed β-TrCP-mediated Sp1 degradation, leading to up-regulation of Sp1 expression in U937/HQ cells. Sp1 up-regulation further increased ADAM17 and Lyn expression, and ADAM17 up-regulation stimulated Lyn activation in U937/HQ cells. Moreover, U937/HQ cells showed higher Lyn-mediated Akt activation and cytoplasmic p21 expression than U937 cells did. Abolishment of Akt activation decreased cytoplasmic p21 expression in U937/HQ cells. Suppression of FOXP3, ADAM17, and Lyn expression, as well as Akt inactivation, repressed proliferation and clonogenicity of U937/HQ cells. Together with the finding that cytoplasmic p21 shows anti-apoptotic and oncogenic activities in cancer cells, the present data suggest a role of FOXP3/ADAM17/Lyn/Akt/p21 signaling axis in HQ-induced hematological disorders.

Forkhead box P3 regulates ARHGAP15 expression and affects migration of glioma cells through the Rac1 signaling pathway

Forkhead box P3 (FOXP3) plays a crucial role in the development and function of regulatory T cells and was recently identified as a tumor suppressor in different cancer types. Forkhead box P3 is expressed in normal brain tissues, but is strongly downregulated or absent in glioblastomas. In order to understand the FOXP3 adjustment mechanisms in glioma cells, we performed a DNA microarray in U87 cells overexpressing FOXP3 and validated the differences using quantitative real‐time PCR, Western blot analysis, and immunohistochemistry in vitro and in vivo. We found that FOXP3 can regulate the expression of ARHGAP15. Expression of FOXP3 was also correlated with ARHGAP15 in glioma samples. Overexpression of FOXP3 inhibited glioma cell migration through ARHGAP15 upregulation and Rac1 inactivation. Silencing of FOXP3 promoted migration through ARHGAP15 downregulation and Rac1 activation. ARHGAP15, a GTPase‐activating protein for Rac1, inhibits small GTPase signaling in a dual negative manner. We found that there is a correlation between expression of ARHGAP15 and glioma level. The small GTPase Rac1 plays an important role in cell migration. In addition, we found that FOXP3 regulates expression of epithelial–mesenchymal transition markers E‐cadherin and N‐cadherin, which is important given that epithelial–mesenchymal transition is critically involved in tumor spreading and dissemination. Thus, FOXP3 or ARHGAP15 may serve as a new molecular target for antimetastatic therapies in treating glioma.

The role of Myc and let-7a in glioblastoma, glucose metabolism and response to therapy

Glioblastoma multiforme (GBM) is thought to result from an imbalance between glucose metabolism and tumor growth. The Myc oncogene and lethal-7a microRNA (let-7a miRNA) have been suggested to cooperatively regulate multiple downstream targets leading to changes in chromosome stability, gene mutations, and/or modulation of tumor growth. Here, we review the roles of Myc and let-7a in glucose metabolism and tumor growth and addresses their future potential as prognostic markers and therapeutic tools in GBM. We focus on the functions of Myc and let-7a in glucose uptake, tumor survival, proliferation, and mobility of glioma cells. In addition, we discuss how regulation of different pathways by Myc or let-7a may be useful for future GBM therapies. A large body of evidence suggests that targeting Myc and let-7a may provide a selective mechanism for the deregulation of glucose metabolic pathways in glioma cells. Indeed, Myc and let-7a are aberrantly expressed in GBM and have been linked to the regulation of cell growth and glucose metabolism in GBM. This article is part of a Special Issue entitled "Targeting alternative glucose metabolism and regulate pathways in GBM cells for future glioblastoma therapies".

FOXP3-miR-146-NF-κB Axis and Therapy for Precancerous Lesions in Prostate

The tumor-suppressive activity of FOXP3 has been observed in tumor initiation, but the underlying mechanism still remains largely unknown. Here, we identified a FOXP3-microRNA-146 (miR-146)-NF-κB axis in vitro and in vivo in prostate cancer cells. We observed that FOXP3 dramatically induced the expression of miR-146a/b, which contributed to transcriptional inhibition of IRAK1 and TRAF6, in prostate cancer cell lines. Tissue-specific deletion of Foxp3 in mouse prostate caused a significant reduction of miR-146a and upregulation of NF-κB activation. In addition, prostatic intraepithelial neoplasia lesions were observed in miR-146a-mutant mice as well as in Foxp3-mutant mice. Notably, the NF-κB inhibitor bortezomib inhibited cell proliferation and induced apoptosis in prostate epithelial cells, attenuating prostatic intraepithelial neoplasia formation in Foxp3-mutant mice. Our data suggest that the FOXP3-miR-146-NF-κB axis has a functional role during tumor initiation in prostate cancer. Targeting the miR-146-NF-κB axis may provide a new therapeutic approach for prostate cancers with FOXP3 defects.

Endogenous FOXP3 inhibits cell proliferation, migration and invasion in glioma cells

The transcription factor forkhead box P3 (FOXP3) has been demonstrated to play important roles in the development and function of regulatory T cells (Tregs). In addition, studies had recently demonstrated that FOXP3 also expressed in some tumor cells. However, the exact role and molecular mechanism of FOXP3 function in glioma's cells are still unclear. This study aims to elucidate the functions of FOXP3 in glioma's cells. Expression of FOXP3 in glioma cell U87 and LN229 was up-regulated and down-regulated by pCMV6-FOXP3-GFP and pRFP-C-RS shFOXP3 respectively. Then, CCK-8 assay, flow cytometry, migration and invasion assay, and western blot were used to detect cell proliferation, cell cycle, cell migration and invasion and related protein expression. All detection methods demonstrated that over-expression of FOXP3 in glioma cell U87 and LN229 inhibited cell proliferation, reduced cell migration, decreased cell invasion compared with control. Moreover, up-regulation of FOXP3 increased the protein levels of pro-apoptotic molecules caspases-3 and caspases-7, resulting in the promotion of cell apoptosis. Conversely down-regulation of the FOXP3 promoted cell growth and inhibited cell apoptosis and reduced the expression of caspases-3 and caspases-7. Our findings suggest that FOXP3 maybe act as a suppressor in glioma cells proliferation, migration and invasion and endogenous FOXP3 transfusion could be a novel approach for inhibiting glioma progression.

FOXP3 over-expression inhibits melanoma tumorigenesis via effects on proliferation and apoptosis

The Forkhead box P3 (FOXP3) transcription factor is the key driver of regulatory T cell (Treg cells) differentiation and immunosuppressive function. In addition, FOXP3 has been reported to be expressed in many tumors, including melanoma. However, its role in tumorigenesis is conflicting, with both tumor suppressive and tumor promoting functions described. The aim of the current study was to characterize the expression and function of FOXP3 in melanoma. FOXP3 expression was detected by immunohistochemistry (IHC) in 12% (18/146) of stage III and IV melanomas. However expression was confined to fewer than 1% of cells in these tumors. Stable over-expression of FOXP3 in the SK-MEL-28 melanoma cell line reduced cell proliferation and clonogenicity in vitro, and reduced xenograft growth in vivo. FOXP3 over-expression also increased pigmentation and the rate of apoptosis of SK-MEL-28 cells. Based on its infrequent expression in human melanoma, and its growth inhibitory and pro-apoptotic effect in over-expressing melanoma cells, we conclude that FOXP3 is not likely to be a key tumor suppressor or promoter in melanoma.

Breast cancer metastasis: demonstration that FOXP3 regulates CXCR4 expression and the response to CXCL12

The X-linked transcription factor FOXP3 is expressed by epithelial cells of organs including the breast, where it is considered a tumour suppressor. The chemokine receptor CXCR4 also regulates the development of breast cancer by stimulating cell migration towards CXCL12-expressing sites of metastatic spread. During activation, human T cells show reciprocal regulation of FOXP3 and CXCR4. This study was designed to examine the role FOXP3 plays in metastatic breast cancer, with a particular focus on its potential to regulate CXCR4. Human breast cancer samples showed significantly decreased FOXP3 protein expression but an increased number of CXCR4 transcripts. In comparison with normal primary breast epithelial cells, FOXP3 was down-regulated at both transcript and protein levels in the breast cancer cell lines MCF-7 and MDA-MB-231. In the invasive MDA-MB-231 cells, the remaining FOXP3 was located predominately within the cytoplasm. Following stable FOXP3 overexpression in MDA-MB-231 cells, significant decreases were observed in the expression of ErbB2/HER2, SKP2, c-MYC, and CXCR4. In contrast, an increase in p21 expression led to inhibition of cell proliferation, with a greater proportion in the G1 phase of the cell cycle suggesting the induction of senescence. Specific knockdown of FOXP3 in normal human breast epithelial cells with siRNA significantly increased ErbB2/HER2, SKP2, c-MYC, and CXCR4, and decreased p21 expression. These cells also showed a significantly increased chemotactic response towards CXCL12, consistent with a role for FOXP3 in the regulation of cell migration. Results from this study are consistent with FOXP3 functioning as an important tumour suppressor in breast cancer. Indeed, the potential functions of FOXP3 in breast epithelium can now be extended to include regulation of CXCR4 expression and response to the pro-metastatic chemokine CXCL12.

Higher FOXP3-TSDR demethylation rates in adjacent normal tissues in patients with colon cancer were associated with worse survival

BACKGROUND

The influence of natural regulatory T cells (nTregs) on the patients with colon cancer is unclear. Demethylated status of the Treg-specific demethylated region (TSDR) of the FOXP3 gene was reported to be a potential biomarker for the identification of nTregs.

METHODS

The demethylation rate of the TSDR (TSDR-DMR) was calculated by using methylation-specific quantitative polymerase chain reaction (MS-qPCR) assay. The expression of TSDR-DMR and FOXP3 mRNA was investigated in various colorectal cancer cell lines. A total of 130 colon carcinoma samples were utilized to study the DMR at tumor sites (DMRT) and adjacent normal tissue (DMRN). The correlations between DMRs and clinicopathological variables of patients with colon cancer were studied.

RESULTS

The TSDR-DMRs varied dramatically among nTregs (97.920 ± 0.466%) and iTregs (3.917 ± 0.750%). Significantly, DMRT (3.296 ± 0.213%) was higher than DMRN (1.605 ± 0.146%) (n = 130, p = 0.000). Higher DMRN levels were found in female patients (p = 0.001) and those with distant metastases (p = 0.017), and were also associated with worse recurrence-free survival in non-stage IV patients (low vs. high, p = 0.022). However, further Cox multivariate analysis revealed that the FOXP3-TSDR status does not have prognostic value.

CONCLUSION

MS-qPCR assays of FOXP3-TSDR can efficiently distinguish nTregs from non-nTregs. Abnormal recruitment of nTregs occurs in the local tumor microenvironment. Infiltration of tissue-resident nTregs may have a negative role in anti-tumor effects in patients with colon cancer; however, this role is limited and complicated.

SELDI-TOF analysis of glioblastoma cyst fluid is an approach for assessing cellular protein expression

OBJECTIVES

In about 10% of glioblastoma patients, preoperative MRI discloses the presence of tumor cysts. Whereas the impact of cystic appearance on prognosis has been discussed extensively, only little is known about the tumor cyst fluid. In this study, we tested the feasibility of the surface enhanced laser desorption ionization time of flight (SELDI-TOF) technique to detect cyst fluid proteins.

METHODS

Cyst fluid was collected from 21 glioblastoma patients for SELDI-TOF analysis and compared to control cerebrospinal fluids from 15 patients with spinal stenosis. Resulting protein peaks with significant differences between groups were further described, using the molecular weight in an internet search of protein databases and publications. Two potential cyst fluid proteins, basigin and ferritin light chain, were selected for immunohistological detection in the histologic slides of the patients, metallothionein (MT) served as negative control.

RESULTS

As supposed from the results of the SELDI-TOF analysis, basigin and ferritin were detected immunohistochemically in the cyst wall, whereas MT was more equally distributed between the cyst wall and the surrounding tumor tissue. Median survival time of the patients was 20 months (range 2 to 102 months) and correlated with age, but not with expression of the three proteins.

DISCUSSION

The SELDI-TOF approach reveals a number of proteins, potentially present in glioblastoma cyst fluid. Identification of these proteins in tumor cells may help understand the pathogenetic pathways and the prognostic value of cystic changes.

The transcription factor Forkhead box P3 (FoxP3) is expressed in glioma cells and associated with increased apoptosis

The forkhead transcription factor FoxP3 is critically involved in the development and function of regulatory T cells (Tregs) that populate tumors and are considered as powerful parts of their immune evasion. However, also tumor cells are reported to express FoxP3. Since gliomas are particularly immunosuppressive tumors, we investigated the occurrence and possible functions of FoxP3 in these malignant cells. By quantitative RT-PCR, immunohistochemistry and FACS analysis, we detected FoxP3 in glioma cells in situ and in vitro. After exposure of glioma cell lines to chemotherapeutics, expression of FoxP3 was significantly enhanced, and it was dislocated from more nuclear to perinuclear localization. Overexpression of FoxP3 in glioma cell lines considerably favored apoptotic damage of nuclei, DNA fragmentation, increased cleavage of the pro-apoptotic enzyme poly(ADP-ribose) polymerase (PARP) and basal activities of effector caspases-3/7. In FoxP3-transfected cells, apoptotic stimuli like Camptothecin, Temozolomide or tumor necrosis factor-α synergistically enhanced caspases-3/7-activities over controls. Taking together, FoxP3 occurs in glioma cells, is induced by chemotherapeutics, and its expression is correlated with increased apoptosis of glioma cells, especially when propagated by apoptotic stimuli. Thus, FoxP3 is a novel pro-apoptotic transcription factor in gliomas that is critically involved in the action of apoptotic agents.