Protein expression of Fas, Fas ligand, Bcl-2 and TGFbeta2 and correlation with survival in initial and recurrent human gliomas

A case of inflammatory hepatocellular adenoma displaying an unusual histological pattern

Hepatocellular adenoma (HCA) is a rare type of liver tumor. Here, we report a variant case of HCA in a 56-year-old Japanese man which displayed unusual histological features. The patient had undergone surgery for esophageal and gastric cancer 2 years prior. A computed tomography scan performed in the follow-up period detected a single lesion (diameter 1.4 cm) in the right posterior lobe of the liver, leading to a partial hepatectomy. Histologically, the lesion was composed of two different types of cells. The larger cells, which accounted for most of the cells in the tumor, exhibited granular and eosinophilic cytoplasm, large nuclei and apparent nucleoli. These cells, which were designated the common cells, were typical of the HCA. The other cells, which were designated the pyknotic cells, were smaller, possessed an eosinophilic, homogeneous cytoplasm and pyknotic small nuclei, but did not contain nucleoli. Immunohistochemically, the common cells reacted strongly positive for C-reactive protein and serum amyloid A, which is compatible with a diagnosis of inflammatory HCA; in contrast, the pyknotic cells tested negative for these molecules. Since the pyknotic cells tested positive for several markers of apoptosis, they were considered to be apoptotic. In addition, as the common cells demonstrated a higher ki-67 labeling index, the lesion was considered to display upregulated cell kinetics, i.e. increases in both cell growth and death. Although HCA is a rare type of tumor, there have been several reports on HCA variants. The case reported here is that of a new type of HCA variant that demonstrated an unusual histological pattern and upregulated cell kinetics.

TGF-β mediates homing of bone marrow-derived human mesenchymal stem cells to glioma stem cells

Although studies have suggested that bone marrow human mesenchymal stem cells (BM-hMSC) may be used as delivery vehicles for cancer therapy, it remains unclear whether BM-hMSCs are capable of targeting cancer stem cells, including glioma stem cells (GSC), which are the tumor-initiating cells responsible for treatment failures. Using standard glioma models, we identify TGF-β as a tumor factor that attracts BM-hMSCs via TGF-β receptors (TGFβR) on BM-hMSCs. Using human and rat GSCs, we then show for the first time that intravascularly administered BM-hMSCs home to GSC-xenografts that express TGF-β. In therapeutic studies, we show that BM-hMSCs carrying the oncolytic adenovirus Delta-24-RGD prolonged the survival of TGF-β-secreting GSC xenografts and that the efficacy of this strategy can be abrogated by inhibition of TGFβR on BM-hMSCs. These findings reveal the TGF-β/TGFβR axis as a mediator of the tropism of BM-hMSCs for GSCs and suggest that TGF-β predicts patients in whom BM-hMSC delivery will be effective.

VEGFR2 expression and TGF-β signaling in initial and recurrent high-grade human glioma

OBJECTIVE

Bevacizumab has promising activity against glioma, although reasons for poor efficacy and variable response rates in certain patients are unclear. Vascular endothelial growth factor receptor 2 (VEGFR2) is heterogeneously expressed within the microvasculature of various malignancies. Moreover, transforming growth factor β (TGF-β), a negative prognostic factor for glioma, is intimately involved in angiogenesis including VEGFR2 regulation. Our objective was to associate expression of VEGFR2 and TGF-β activity with clinicopathological features of human glioma.

METHODS

Expression patterns determined by immunohistochemistry for VEGFR2 and phosphorylated Smad2 in human gliomas were compared to overall survival, progression-free survival (PFS), initial versus recurrent tumors and tumor grade.

RESULTS

Endothelial VEGFR2 expression was low or undetectable in normal tissue but the proportion of VEGFR2-positive vessels increased with tumor grade. Decreased PFS was associated with tumors whose vessels had increased proportions of VEGFR2 at recurrence. Neither parenchymal nor endothelial cell p-Smad2 was associated with tumor grade; however, the former was negatively correlated with overall survival in glioblastoma multiforme.

CONCLUSIONS

The molecular phenotype of the vasculature based on the status of VEGFR2 but not p-Smad2 is related to aspects of glioma progression and patient response. Changes in VEGFR2-positive vessels may account for variable therapeutic efficacy of anti-angiogenic agents.

Targeting apoptosis pathways in glioblastoma

The treatment of glioblastoma remains a major challenge for clinicians since these highly aggressive brain tumors are relatively resistant towards radio- and chemotherapy. The pathways that control apoptosis are altered in glioblastoma cells leading to resistance towards apoptotic stimuli in general. In this review we describe the alterations affecting the p53 pathway, the BCL-2 protein family, the inhibitor of apoptosis proteins and several growth factor pathways involved in the regulation of programmed cell death and define possible targets for new therapies within these apoptotic pathways in glioblastomas. Moreover, we review strategies to target death receptor pathways, most notably to render the glioblastoma cells more susceptible towards this approach without enhancing toxicity in general. Most of the strategies targeting apoptosis in glioblastomas presented here are in a pre-clinical stage of development, however, they all share the ultimative goal to improve the outcome for glioblastoma patients.

FasL and FADD delivery by a glioma-specific and cell cycle-dependent HSV-1 amplicon virus enhanced apoptosis in primary human brain tumors

BACKGROUND

Glioblastoma multiforme is the most malignant cancer of the brain and is notoriously difficult to treat due to the highly proliferative and infiltrative nature of the cells. Herein, we explored the combination treatment of pre-established human glioma xenograft using multiple therapeutic genes whereby the gene expression is regulated by both cell-type and cell cycle-dependent transcriptional regulatory mechanism conferred by recombinant HSV-1 amplicon vectors.

RESULTS

We demonstrated for the first time that Ki67-positive proliferating primary human glioma cells cultured from biopsy samples were effectively induced into cell death by the dual-specific function of the pG8-FasL amplicon vectors. These vectors were relatively stable and exhibited minimal cytotoxicity in vivo. Intracranial implantation of pre-transduced glioma cells resulted in better survival outcome when compared with viral vectors inoculated one week post-implantation of tumor cells, indicating that therapeutic efficacy is dependent on the viral spread and mode of viral vectors administration. We further showed that pG8-FasL amplicon vectors are functional in the presence of commonly used treatment regimens for human brain cancer. In fact, the combined therapies of pG8-FasL and pG8-FADD in the presence of temozolomide significantly improved the survival of mice bearing intracranial high-grade gliomas.

CONCLUSION

Taken together, our results showed that the glioma-specific and cell cycle-dependent HSV-1 amplicon vector is potentially useful as an adjuvant therapy to complement the current gene therapy strategy for gliomas.

Distinct effects of human glioblastoma immunoregulatory molecules programmed cell death ligand-1 (PDL-1) and indoleamine 2,3-dioxygenase (IDO) on tumour-specific T cell functions

Immunotherapy is a promising new treatment for patients suffering from glioma, in particular glioblastoma multiforme (GBM). However, tumour cells use different mechanisms to escape the immune responses induced by the treatment. As many other tumours, gliomas express or secrete several immunosuppressive molecules that regulate immune cell functions. In this study, we first analysed FasL, HLA-G, IDO, PDL-1 and TGF-beta1, -beta2 and -beta3 expression by transcriptomic microarray analysis in a series of 20 GBM samples and found respectively 15%, 60%, 85%, 30%, 70%, 80% and 35% of positive specimens. mRNA expression was then confirmed in 10 GBM primary cell lines and 2 immortalised cell lines U251 and U87MG. Furthermore, the protein expression of PDL-1, IDO activity and TGF-beta2 secretion were found on most of the untreated GBM primary cell lines. Remarkably, treatment with IFN-gamma increased the PDL-1 cell surface expression and the IDO activity, but reduced the TGF-beta2 secretion of GBM cell lines. We finally analysed the immunosuppressive effects of IDO, PDL-1 and TGF-beta1-3 by measuring IFN-gamma production and cell cytotoxicity activity of tumour antigen-specific T cells. PDL-1 partially affected the IFN-gamma production of antigen-specific T cells in response to GBM primary cell lines, and IDO inhibited lymphocyte proliferation induced by lectins. None of these molecules directly affected the T cell cytotoxicity function. Due to the functional role of PDL-1 and IDO molecules expressed by GBM cells, one could expect that blocking these molecules in the immunotherapy strategies would reinforce the efficiency of these treatments of GBM patients.

Regulatory T cells and the PD-L1/PD-1 pathway mediate immune suppression in malignant human brain tumors

The brain is a specialized immune site representing a unique tumor microenvironment. The availability of fresh brain tumor material for ex vivo analysis is often limited because large parts of many brain tumors are resected using ultrasonic aspiration. We analyzed ultrasonic tumor aspirates as a biosource to study immune suppressive mechanisms in 83 human brain tumors. Lymphocyte infiltrates in brain tumor tissues and ultrasonic aspirates were comparable with respect to lymphocyte content and viability. Applying ultrasonic aspirates, we detected massive infiltration of CD4+FoxP3+CD25(high) CD127(low) regulatory T cells (Tregs) in glioblastomas (n = 29) and metastatic brain tumors (n = 20). No Treg accumulation was observed in benign tumors such as meningiomas (n = 10) and pituitary adenomas (n = 5). A significant Treg increase in blood was seen only in patients with metastatic brain tumors. Tregs in high-grade tumors exhibited an activated phenotype as indicated by decreased proliferation and elevated CTLA-4 and FoxP3 expression relative to blood Tregs. Functional analysis showed that the tumor-derived Tregs efficiently suppressed cytokine secretion and proliferation of autologous intratumoral lymphocytes. Most tumor-infiltrating Tregs were localized in close proximity to effector T cells, as visualized by immunohistochemistry. Furthermore, 61% of the malignant brain tumors expressed programmed death ligand-1 (PD-L1), while the inhibitory PD-1 receptor was expressed on CD4+ effector cells present in 26% of tumors. In conclusion, using ultrasonic tumor aspirates as a biosource we identified Tregs and the PD-L1/PD-1 pathway as immune suppressive mechanisms in malignant but not benign human brain tumors.

Prognostic markers of astrocytoma: how to predict the unpredictable?

Astrocytomas are the most frequent tumors originating in the human nervous system. They carry a dismal prognosis as high-grade astroctyoma patients (World Health Organization [WHO] grade III and IV) rarely live beyond 5 years. At present, these tumors are mainly diagnosed through the difficult task of histologic examination of tissue obtained through stereotactic biopsy or tumor resection. In addition to determining the malignancy grade through histologic studies, the only other prognostic factors used in clinical setting are patient age and performance status. To overcome current limitations, research is underway to develop molecular approaches for glioma classification. These include identification, characterization and expansion of clinical (patient characteristics and imaging variables), histologic (WHO classification criteria) and molecular (genetic and proteomic) factors with prognostic potential. In this review the established classification characteristics, along with recent advances that may lead to the addition of new parameters and thus improve patient management and survival, are discussed.

Fas/Fas ligand gene polymorphism in patients with papillary thyroid cancer in the Turkish population

OBJECTIVE

Fas ligand (FasL) is an apoptotic agent and a member of tumor necrosis factor (TNF) family. FasL exists in cytotoxic T lymphocyte (CTL) and natural killer (NK) cells, and it is increased in tumor cell membrane. On the contrary, CTL and NK are bound to Fas on the surfaces of cell membrane; this triggers apoptosis in cytotoxic cells and leads to their death. This system plays an important role in eliminating viral infections and cancer cells. Malfunction of this system results in the development and spread of the malignancy. This study aims at evaluating the influence of Fas and FasL gene polymorphism in papillary thyroid cancer (PTC) in the Turkish population.

RESEARCH DESIGN AND METHODS

Forty-five patients with PTC and 100 healthy controls were included in this study. The diagnosis of PTC was confirmed by histopathologic examination after surgery. The evaluation of genotype for Fas 670 A/G and FasL 843 C/T gene polymorphism was performed using the PCR-restriction fragment length polymorphism (RFLP) method.

RESULTS

The evaluation of Fas/FasL genotype and gene allele frequency did not show statistically significant differences between the patient and control group (p>0.05). In addition, the univariate analysis did not reveal a statistically significant relationship between the size of the nodule and the Fas/FasL gene polymorphism in patients with PTC.

CONCLUSIONS

As in other types of malignancy, genetic factors in the pathogenesis of PTC may also show changes in different populations. Fas/FasL gene polymorphysms are possible that different mechanisms function in apoptosis balance in PTC development.

TGF-beta1, TNF-alpha and cytochrome c in human astrocytic tumors: a short-term follow up and correlation with survival

OBJECTIVES

To evaluate the association of signals of apoptosis namely, TGF-beta1, TNF-alpha and cytochrome c release in cytoplasm with survival rate to determine the potential use of such parameters as predictive markers for patients with astrocytomas.

DESIGN AND METHODS

We measured TGF-beta1, TNF-alpha and cytoplasmic cytochrome c in 30 astrocytic tumors Grade II, III and IV.

RESULTS

We found that TNF-alpha and cytochrome c release in Grade IV tends to be significantly lower than those in Grade II, whereas TGF-beta1 did not significantly change in the different grades. Patients with astrocytic tumors having elevated cytochrome c showed a better survival rate compared to those with less release. There is neither a correlation shown between TNF-alpha and cytochrome c release nor between TNF-alpha and patient survival. TGF-beta1 was positively correlated with cytochrome c release. Patients showing such correlation had increased survival rate over 18 months follow up period.

CONCLUSION

These data suggest that TGF-beta1 and cytochrome c may be useful prognostic markers that help patients' stratification and in adjusting the disciplines of therapy.

Molecular neuro-oncology and the development of targeted therapeutic strategies for brain tumors. Part 5: apoptosis and cell cycle

Brain tumors are a diverse group of malignancies that remain refractory to conventional treatment approaches. Molecular neuro-oncology has now begun to clarify the transformed phenotype of brain tumors and identify oncogenic pathways that might be amenable to targeted therapy. Abnormalities of the apoptotic and cell cycle signaling pathways are key molecular features of many brain tumors and are currently under evaluation for potential therapeutic intervention. The apoptosis pathway has numerous targets for molecular therapeutic development, including p53, Bax, Bcl-2, cFLIP, effector caspases, growth factor receptors, phosphatidylinositol-3-kinase, Akt and apoptosis inhibitors. Current molecular treatment approaches include antisense techniques, gene therapy and small-molecule modulators and inhibitors. Potential targets of the cell cycle pathway include the cyclins, cyclin-dependent kinases, p53, retinoblastoma, E2F and the cyclin-dependent kinase inhibitors. Developmental molecular therapeutics for this pathway include adenoviral and gene therapy, small-peptide cyclin-dependent kinase modulators, proteasomal inhibitors and small-molecule cyclin-dependent kinase inhibitors. Several of these recently identified agents have begun evaluation in clinical trials. Further development of targeted therapies designed to modulate apoptosis and the cell cycle, and evaluation of these new agents in clinical trials, will be needed to improve survival and quality of life for patients with brain tumors.

Molecular mechanisms in gliomagenesis

Glioma, and in particular high-grade astrocytoma termed glioblastoma multiforme (GBM), is the most common primary tumor of the brain. Primarily because of its diffuse nature, there is no effective treatment for GBM, and relatively little is known about the processes by which it develops. Therefore, in order to design novel therapies and treatments for GBM, research has recently intensified to identify the cellular and molecular mechanisms leading to GBM formation. Modeling of astrocytomas by genetic manipulation of mice suggests that deregulation of the pathways that control gliogenesis during normal brain development, such as the differentiation of neural stem cells (NSCs) into astrocytes, might contribute to GBM formation. These pathways include growth factor-induced signal transduction routes and processes that control cell cycle progression, such as the p16-CDK4-RB and the ARF-MDM2-p53 pathways. The expression of several of the components of these signaling cascades has been found altered in GBM, and recent data indicate that combinations of mutations in these pathways may contribute to GBM formation, although the exact mechanisms are still to be uncovered. Use of novel techniques including large-scale genomics and proteomics in combination with relevant mouse models will most likely provide novel insights into the molecular mechanisms underlying glioma formation and will hopefully lead to development of treatment modalities for GBM.

Enhanced expression and shedding of the transmembrane chemokine CXCL16 by reactive astrocytes and glioma cells

The transmembrane chemokine CXCL16 is expressed by dendritic and vascular cells and mediates chemotaxis and adhesion of activated T cells via the chemokine receptor CXCR6/Bonzo. Here we describe the expression and shedding of this chemokine by glioma cells in situ and in vitro. By quantitative RT-PCR and immunohistochemistry, we show that CXCL16 is highly expressed in human gliomas, while expression in normal brain is low and mainly restricted to brain vascular endothelial cells. In cultivated human glioma cells as well as in activated mouse astroglial cells, CXCL16 mRNA and protein is constitutively expressed and further up-regulated by tumour necrosis factor alpha (TNFalpha) and interferon-gamma (IFNgamma). CXCL16 is continuously released from glial cells by proteolytic cleavage which is rapidly enhanced by stimulation with phorbol-12-myristate-13-acetate (PMA). As shown by inhibitor studies, two distinct members of the disintegrin-like metalloproteinase family ADAM10 and 17 are involved in the constitutive and PMA-induced shedding of glial CXCL16. In addition to the chemokine, its receptor CXCR6 could be detected by quantitative RT-PCR in human glioma tissue, cultivated murine astrocytes and at a lower level in microglial cells. Functionally, recombinant soluble CXCL16 enhanced proliferation of CXCR6-positive murine astroglial and microglial cells. Thus, the transmembrane chemokine CXCL16 is expressed in the brain by malignant and inflamed astroglial cells, shed to a soluble form and targets not only activated T cells but also glial cells themselves.

Sensitization of Glioma Cells to Fas-Dependent Apoptosis by Chemotherapy-Induced Oxidative Stress

A prominent feature of glioblastoma is its resistance to death from Fas pathway activation. In this study, we explored the modulation of Fas-induced glioblastoma death with chemotherapeutic agents. Camptothecin significantly increased the glioblastoma cell death response to Fas receptor activation regardless of p53 status. Sublethal concentrations of camptothecin reduced the IC50 of agonistic anti-Fas antibody (CH-11) 10-fold, from 500 to 50 ng/mL, in human U87 glioblastoma cells (p53 wild-type). Cell viability in response to camptothecin, CH-11 alone, and the combination of camptothecin + CH-11 was found to be 84%, 85%, and 47% (P < 0.001), respectively. A similar pattern of relative cytotoxicity was found in U373 cells (p53 mutant). We further examined the pathways and mechanisms involved in this apparent synergistic cytotoxic response. Cell death was found to be predominantly apoptotic involving both extrinsic and intrinsic pathways as evidenced by annexin V staining, cleavage of caspases (3, 8, and 9), increased caspase activities, Smac release, and cytoprotection by caspase inhibitors. Expression of Fas-associated death domain, and not Fas, Fas ligand, or caspase proteins, increased following cell treatment with camptothecin + CH-11. Camptothecin treatment enhanced c-jun-NH2-kinase activation in response to CH-11, but inhibition of c-jun-NH2-kinase did not prevent cell death induced by the combination treatment. Reactive oxygen species, especially H2O2, were elevated following camptothecin treatment; and H2O2 enhanced cell death induced by CH-11. The antioxidants glutathione and N-acetyl-cysteine prevented cell death induced by camptothecin + CH-11. These findings show that camptothecin synergizes with Fas activation to induce glioblastoma apoptosis via a mechanism involving reactive oxygen species and oxidative stress pathways.