The immunoglobulin superfamily ligand B7H6 subjects T cell responses to NK cell surveillance.

Understanding the mechanisms that regulate T cell immunity is critical for the development of effective therapies for diseases associated with T cell dysfunction, including autoimmune diseases, chronic infections, and cancer. Co-inhibitory "checkpoint molecules," such as programmed cell death protein-1, balance excessive or prolonged immune activation by T cell-intrinsic signaling. Here, by screening for mediators of natural killer (NK) cell recognition on T cells, we identified the immunoglobulin superfamily ligand B7H6 to be highly expressed by activated T cells, including patient-infused CD19-targeting chimeric antigen receptor (CAR) T cells. Unlike other checkpoint molecules, B7H6 mediated NKp30-dependent recognition and subsequent cytolysis of activated T cells by NK cells. B7H6+ T cells were prevalent in the tissue and blood of several diseases, and their abundance in tumor tissue positively correlated with clinical response in a cohort of patients with immune checkpoint inhibitor-treated esophageal cancer. In humanized mouse models, NK cell surveillance via B7H6 limited the persistence and antitumor activity of CAR T cells, and its genetic deletion enhanced T cell proliferation and persistence. Together, we provide evidence of B7H6 protein expression by activated T cells and suggest the B7H6-NKp30 axis as a therapeutically actionable NK cell-dependent immune checkpoint that regulates human T cell function.

Autonomous rhythmic activity in glioma networks drives brain tumour growth.

Diffuse gliomas, particularly glioblastomas, are incurable brain tumours1. They are characterized by networks of interconnected brain tumour cells that communicate via Ca2+ transients2-6. However, the networks' architecture and communication strategy and how these influence tumour biology remain unknown. Here we describe how glioblastoma cell networks include a small, plastic population of highly active glioblastoma cells that display rhythmic Ca2+ oscillations and are particularly connected to others. Their autonomous periodic Ca2+ transients preceded Ca2+ transients of other network-connected cells, activating the frequency-dependent MAPK and NF-κB pathways. Mathematical network analysis revealed that glioblastoma network topology follows scale-free and small-world properties, with periodic tumour cells frequently located in network hubs. This network design enabled resistance against random damage but was vulnerable to losing its key hubs. Targeting of autonomous rhythmic activity by selective physical ablation of periodic tumour cells or by genetic or pharmacological interference with the potassium channel KCa3.1 (also known as IK1, SK4 or KCNN4) strongly compromised global network communication. This led to a marked reduction of tumour cell viability within the entire network, reduced tumour growth in mice and extended animal survival. The dependency of glioblastoma networks on periodic Ca2+ activity generates a vulnerability7 that can be exploited for the development of novel therapies, such as with KCa3.1-inhibiting drugs.

PFKFB4 interacts with FBXO28 to promote HIF-1α signaling in glioblastoma.

Glioblastoma is a highly aggressive brain tumor for which there is no cure. The metabolic enzyme 6-Phosphofructo-2-Kinase/Fructose-2,6-Biphosphatase 4 (PFKFB4) is essential for glioblastoma stem-like cell (GSC) survival but its mode of action is unclear. Understanding the role of PFKFB4 in tumor cell survival could allow it to be leveraged in a cancer therapy. Here, we show the importance of PFKFB4 for glioblastoma growth in vivo in an orthotopic patient derived mouse model. In an evaluation of patient tumor samples of different cancer entities, PFKFB4 protein was found to be overexpressed in prostate, lung, colon, mammary and squamous cell carcinoma, with expression level correlating with tumor grade. Gene expression profiling in PFKFB4-silenced GSCs revealed a downregulation of hypoxia related genes and Western blot analysis confirmed a dramatic reduction of HIF (hypoxia inducible factor) protein levels. Through mass spectrometric analysis of immunoprecipitated PFKFB4, we identified the ubiquitin E3 ligase, F-box only protein 28 (FBXO28), as a new interaction partner of PFKFB4. We show that PFKFB4 regulates the ubiquitylation and subsequent proteasomal degradation of HIF-1α, which is mediated by the ubiquitin ligase activity of FBXO28. This newly discovered function of PFKFB4, coupled with its cancer specificity, provides a new strategy for inhibiting HIF-1α in cancer cells.

DNA methylation profiling is a method of choice for molecular verification of pediatric WNT-activated medulloblastomas.

BACKGROUND: Wingless-activated medulloblastoma (WNT MB) represents a well-characterized molecular variant accounting for 10-15% of all MB and is associated with a favorable clinical outcome. Patients with localized WNT MBs could benefit from de-intensification of combined treatment, which would require an accurate diagnosis of these tumors. However, despite the presence of molecular features related with a WNT MB signature (nuclear ß-catenin immunoexpression, CTNNB1 mutation, and monosomy 6), a prompt and reliable diagnostic verification of these tumors is not yet feasible. METHODS: In the current study, we analyzed 78 samples of WNT MB treated in a single institute through genome-wide DNA methylation and targeted next generation sequencing to elaborate an optimal method for WNT MB molecular verification. RESULTS: We found that DNA methylation profiling discloses significant advantages for molecular diagnostic of WNT MB. All other "routine" methods applied, such as ß-catenin immunohistochemistry, CTNNB1 mutation analysis, and detection of monosomy 6, failed to identify all WNT MB cases. Survival analysis revealed that application of a reduced radiotherapy protocol for WNT MB treatment had no influence on patients' survival. Only one patient died due to local relapse but recurrent tumor was pathologically and molecularly diagnosed as a secondary glioblastoma. CONCLUSIONS: DNA methylation analysis should be considered as a method of choice for further clinically relevant stratification of WNT MB and for correct diagnosis of the recurrent tumors. WNT MB patients with localized disease could benefit from treatment de-intensification.

Suppression of antitumor T cell immunity by the oncometabolite (R)-2-hydroxyglutarate.

The oncometabolite (R)-2-hydroxyglutarate (R-2-HG) produced by isocitrate dehydrogenase (IDH) mutations promotes gliomagenesis via DNA and histone methylation. Here, we identify an additional activity of R-2-HG: tumor cell-derived R-2-HG is taken up by T cells where it induces a perturbation of nuclear factor of activated T cells transcriptional activity and polyamine biosynthesis, resulting in suppression of T cell activity. IDH1-mutant gliomas display reduced T cell abundance and altered calcium signaling. Antitumor immunity to experimental syngeneic IDH1-mutant tumors induced by IDH1-specific vaccine or checkpoint inhibition is improved by inhibition of the neomorphic enzymatic function of mutant IDH1. These data attribute a novel, non-tumor cell-autonomous role to an oncometabolite in shaping the tumor immune microenvironment.

Epithelioid glioblastomas stratify into established diagnostic subsets upon integrated molecular analysis.

Epithelioid glioblastoma (eGBM) is a newly defined and rare GBM variant in the current WHO 2016 classification. BRAF V600E mutation is overrepresented in these tumors and there is known some morphological overlap with anaplastic epithelioid PXA (ePXA). In order to further elucidate this diagnostic category, we molecularly characterized 64 pediatric and adult examples initially diagnosed as "eGBM." Tumors were analyzed using array based methylation and direct sequencing of the BRAF and TERT genes. Our results demonstrated considerable molecular and clinical heterogeneity among eGBM cohort. Methylation patterns, copy number alterations, and mutational analysis data, in combination with clinical findings disclosed three different, well established tumor subtypes: (i) PXA-like tumors with favorable prognosis, predominantly in children and young adults (38), (ii) IDHwt GBM-like tumors with poor prognosis, mainly occurring in older adults, albeit with more frequent BRAF mutations (17), and (iii) RTK1 pediatric GBM-like neoplasms of intermediate prognosis in children and young adults, associated with chromothripsis and frequent PDGFRA amplifications (9). We conclude that the histopathologically defined eGBM do not represent a single diagnostic entity, but rather at least three molecularly and biologically distinct categories. Therefore, additional molecular testing through genome-wide molecular profiling is recommended to further stratify these rare cases.

H3-/IDH-wild type pediatric glioblastoma is comprised of molecularly and prognostically distinct subtypes with associated oncogenic drivers.

Pediatric glioblastoma (pedGBM) is an extremely aggressive pediatric brain tumor, accounting for ~6% of all central nervous system neoplasms in children. Approximately half of pedGBM harbor recurrent somatic mutations in histone 3 variants or, infrequently, IDH1/2. The remaining subset of pedGBM is highly heterogeneous, and displays a variety of genomic and epigenetic features. In the current study, we aimed to further stratify an H3-/IDH-wild type (wt) pedGBM cohort assessed through genome-wide molecular profiling. As a result, we identified three molecular subtypes of these tumors, differing in their genomic and epigenetic signatures as well as in their clinical behavior. We designated these subtypes 'pedGBM_MYCN' (enriched for MYCN amplification), 'pedGBM_RTK1' (enriched for PDGFRA amplification) and 'pedGBM_RTK2' (enriched for EGFR amplification). These molecular subtypes were associated with significantly different outcomes, i.e. pedGBM_RTK2 tumors show a significantly longer survival time (median OS 44 months), pedGBM_MYCN display extremely poor outcomes (median OS 14 months), and pedGBM_RTK1 tumors harbor an intermediate prognosis. In addition, the various molecular subtypes of H3-/IDH-wt pedGBM were clearly distinguishable from their adult counterparts, underlining their biological distinctiveness. In conclusion, our study demonstrates significant molecular heterogeneity of H3-/IDH-wt pedGBM in terms of DNA methylation and cytogenetic alterations. The recognition of three molecular subtypes of H3-/IDH-wt pedGBM further revealed close correlations with biological parameters and clinical outcomes and may therefore, be predictive of response to standard treatment protocols, but could also be useful for stratification for novel, molecularly based therapies.

Neurofibromin specific antibody differentiates malignant peripheral nerve sheath tumors (MPNST) from other spindle cell neoplasms.

Malignant peripheral nerve sheath tumors (MPNST) derive from the Schwann cell or perineurial cell lineage and occur either sporadically or in association with the tumor syndrome neurofibromatosis type 1 (NF1). MPNST often pose a diagnostic challenge due to their frequent lack of pathognomonic morphological or immunohistochemical features. Mutations in the NF1 tumor suppressor gene are found in all NF1-associated and many sporadic MPNST. The presence of NF1 mutation may have the potential to differentiate MPNST from several morphologically similar neoplasms; however, mutation detection is hampered by the size of the gene and the lack of mutational hot spots. Here we describe a newly developed monoclonal antibody binding to the C-terminus of neurofibromin (clone NFC) which was selected for optimal performance in routinely processed formalin-fixed and paraffin-embedded tissue. NFC immunohistochemistry revealed loss of neurofibromin in 22/25 (88 %) of NF1-associated and 26/61 (43 %) of sporadic MPNST. There was a strong association of neurofibromin loss with deletions affecting the NF1 gene (P < 0.01). In a series of 256 soft tissue tumors of different histotypes NFC staining showed loss of neurofibromin in 2/8 myxofibrosarcomas, 2/12 (16 %) pleomorphic liposarcomas, 1/16 (6 %) leiomyosarcomas, and 4/28 (14 %) unclassified undifferentiated pleomorphic sarcomas. However, loss of neurofibromin was not observed in 22 synovial sarcomas, 27 schwannomas, 23 solitary fibrous tumors, 14 low-grade fibromyxoid sarcomas, 50 dedifferentiated liposarcomas, 27 myxoid liposarcomas, 13 angiosarcomas, 9 extraskeletal myxoid chondrosarcomas, and 7 epitheloid sarcomas. Immunohistochemistry using antibody NFC may substantially facilitate sarcoma research and diagnostics.

AKT1E17K mutations cluster with meningothelial and transitional meningiomas and can be detected by SFRP1 immunohistochemistry.

The activating E17K mutation in the AKT1 gene has been detected in several tumor entities. Currently several clinical studies with specific AKT1 inhibitors are under way. To determine whether AKT1 mutations are involved in human tumors of the nervous system, we examined a series of 1,437 tumors including 391 primary intracranial brain tumors and 1,046 tumors of the coverings of the central and peripheral nervous system. AKT1E17K mutations were exclusively seen in meningiomas and occurred in 65 of 958 of these tumors. A strong preponderance was seen in the variant of meningothelial meningioma WHO grade I of basal and spinal localization. In contrast, AKT1E17K mutations were rare in WHO grade II and absent in WHO grade III meningiomas. In order to more effectively detect this mutation, we tested for immunohistochemical markers associated with this alteration. We observed strong up-regulation of SFRP1 expression in all meningiomas with AKT1E17K mutation and in HEK293 cells after transfection with mutant AKT1E17K, but not in meningiomas and HEK293 cells lacking this mutation.

Meningeal hemangiopericytoma and solitary fibrous tumors carry the NAB2-STAT6 fusion and can be diagnosed by nuclear expression of STAT6 protein.

Non-central nervous system hemangiopericytoma (HPC) and solitary fibrous tumor (SFT) are considered by pathologists as two variants of a single tumor entity now subsumed under the entity SFT. Recent detection of frequent NAB2-STAT6 fusions in both, HPC and SFT, provided additional support for this view. On the other hand, current neuropathological practice still distinguishes between HPC and SFT. The present study set out to identify genes involved in the formation of meningeal HPC. We performed exome sequencing and detected the NAB2-STAT6 fusion in DNA of 8/10 meningeal HPC thereby providing evidence of close relationship of these tumors with peripheral SFT. Due to the considerable effort required for exome sequencing, we sought to explore surrogate markers for the NAB2-STAT6 fusion protein. We adopted the Duolink proximity ligation assay and demonstrated the presence of NAB2-STAT6 fusion protein in 17/17 HPC and the absence in 15/15 meningiomas. More practical, presence of the NAB2-STAT6 fusion protein resulted in a strong nuclear signal in STAT6 immunohistochemistry. The nuclear reallocation of STAT6 was detected in 35/37 meningeal HPC and 25/25 meningeal SFT but not in 87 meningiomas representing the most important differential diagnosis. Tissues not harboring the NAB2-STAT6 fusion protein presented with nuclear expression of NAB2 and cytoplasmic expression of STAT6 proteins. In conclusion, we provide strong evidence for meningeal HPC and SFT to constitute variants of a single entity which is defined by NAB2-STAT6 fusion. In addition, we demonstrate that this fusion can be rapidly detected by STAT6 immunohistochemistry which shows a consistent nuclear reallocation. This immunohistochemical assay may prove valuable for the differentiation of HPC and SFT from other mesenchymal neoplasms.

BRAFV600E mutant protein is expressed in cells of variable maturation in Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a clinically and histologically heterogeneous disorder. Its classification as either reactive inflammatory or neoplastic has been a matter of debate. However, the recent finding of frequent BRAFV600E mutations in LCH argues for the latter. The exact cell type that harbors the mutation and is responsible for proliferation remains to be identified. We here apply a BRAFV600E mutation-specific antibody to detect the BRAF mutant cells in lesions from 89 patients with LCH. We found BRAFV600E mutations in 34 of 89 (38%) lesions. In lesions with the BRAFV600E mutation, the majority of cells coexpressing S-100 and CD1a harbored mutant BRAFV600E protein. These cells also expressed CD14 and CD36, whereas various fractions exhibited CD207. On the other hand, CD80 and CD86 expression was also present on BRAFV600E-positive cells. Thus, cells of variable maturation, exhibiting an immunohistochemical profile compatible either with myeloid cell or with dedifferentiated Langerhans cell antigens, carry the BRAFV600E mutation. In conclusion, we identify and characterize the neoplastic cells in LCH with BRAFV600E mutations by applying a mutation-specific marker and demonstrate feasibility for routine screening.

Immunohistochemical testing of BRAF V600E status in 1,120 tumor tissue samples of patients with brain metastases.

Brain metastases (BM) are frequent and carry a dismal prognosis. BRAF V600E mutations are found in a broad range of tumor types and specific inhibitors targeting BRAF V600E protein exist. We analyzed tumoral BRAF V600E-mutant protein expression using the novel mutation-specific antibody VE1 in a series of 1,120 tumor specimens (885 BM, 157 primary tumors, 78 extra-cranial metastases) of 874 BM patients. In 85 cases, we performed validation of immunohistochemical results by BRAF exon 15 gene sequencing. BRAF V600E protein was expressed in BM of 42/76 (55.3%) melanomas, 1/15 (6.7%) ovarian cancers, 4/72 (5.5%) colorectal cancers, 1/355 (0.3%) lung cancers, 2/6 thyroid cancers and 1/2 choriocarcinomas. BRAF V600E expression showed high intra-tumoral homogeneity and was similar in different tumor manifestations of individual patients. VE1 immunohistochemistry and BRAF exon 15 sequencing were congruent in 68/70 (97.1%) cases, but VE1 immunostaining identified small BRAF V600E expressing tumor cell aggregates in 10 cases with inconclusive genetic results. Melanoma patients with BRAF V600E mutant protein expressing tumors were significantly younger at diagnosis of the primary tumor and at operation of BM than patients with non-mutated tumors. In conclusion, expression of BRAF V600E mutant protein occurs in approximately 6% of BM and is consistent in different tumor manifestations of the same patient. Thus, BRAF V600E inhibiting therapies seem feasible in selected BM patients. Immunohistochemical visualization of V600E-mutant BRAF protein is a promising tool for patient stratification. An integrated approach combining both, VE1 immunohistochemistry and genetic analysis may increase the diagnostic accuracy of BRAF mutation analysis.

Addressing diffuse glioma as a systemic brain disease with single-cell analysis.

OBJECTIVE: To analyze infiltration patterns of IDH1 mutant diffuse gliomas into the brain by identification of single tumor cells applying an antibody specific to mutant IDH1 R132H protein. DESIGN: Immunohistochemical analysis. SETTING: University hospital. PATIENTS: Whole-brain and hemisphere sections of 4 patients diagnosed with diffuse glioma. RESULTS: Tumor cells were identified in areas that appeared inconspicuous macroscopically and at histological analysis with respect to cellularity, cellular pleomorphism, or mitotic activity in all cases. CONCLUSION: Detection of single tumor cells throughout the brain demonstrates diffuse glioma to represent systemic brain disease.

Assessment of BRAF V600E mutation status by immunohistochemistry with a mutation-specific monoclonal antibody.

Activating mutations of the serine threonine kinase v-RAF murine sarcoma viral oncogene homolog B1 (BRAF) are frequent in benign and malignant human tumors and are emerging as an important biomarker. Over 95% of BRAF mutations are of the V600E type and specific small molecular inhibitors are currently under pre-clinical or clinical investigation. BRAF mutation status is determined by DNA-based methods, most commonly by sequencing. Here we describe the development of a monoclonal BRAF V600E mutation-specific antibody that can differentiate BRAF V600E and wild type protein in routinely processed formalin-fixed and paraffin-embedded tissue. A total of 47 intracerebral melanoma metastases and 21 primary papillary thyroid carcinomas were evaluated by direct sequencing of BRAF and by immunohistochemistry using the BRAF V600E mutation-specific antibody clone VE1. Correlation of VE1 immunohistochemistry and BRAF sequencing revealed a perfect match for both papillary thyroid carcinomas and melanoma metastases. The staining intensity in BRAF V600E mutated tumor samples ranged from weak to strong. The generally homogenous VE1 staining patterns argue against a clonal heterogeneity of the tumors investigated. Caution is essential when only poorly preserved tissue is available for VE1 immunohistochemical analysis or when tissues with only little total BRAF protein are analyzed. Immunohistochemistry using antibody VE1 may substantially facilitate molecular analysis of BRAF V600E status for diagnostic, prognostic, and predictive purposes.

Characterization of R132H mutation-specific IDH1 antibody binding in brain tumors.

Heterozygous point mutations of isocitrate dehydrogenase (IDH)1 codon 132 are frequent in grade II and III gliomas. Recently, we reported an antibody specific for the IDH1R132H mutation. Here we investigate the capability of this antibody to differentiate wild type and mutated IDH1 protein in central nervous system (CNS) tumors by Western blot and immunohistochemistry. Results of protein analysis are correlated to sequencing data. In Western blot, anti-IDH1R132H mouse monoclonal antibody mIDH1R132H detected a specific band only in mutated tumors. Immunohistochemistry of 345 primary brain tumors demonstrated a strong cytoplasmic and weaker nuclear staining in 122 cases. Correlation with direct sequencing of 186 cases resulted in consensus of 177 cases. Genetic retesting of cases with conflicting findings resulted in a match of 186/186 cases, with all discrepancies resolving in favor of immunohistochemistry. Intriguing is the ability of mIDH1R132H to detect single infiltrating tumor cells. The very high frequency and the distribution of this mutation among specific brain tumor entities allow the highly sensitive and specific discrimination of various tumors by immunohistochemistry, such as anaplastic astrocytoma from primary glioblastoma or diffuse astrocytoma World Health Organization (WHO) grade II from pilocytic astrocytoma or ependymoma. Noteworthy is the discrimination of the infiltrating edge of tumors with IDH1 mutation from reactive gliosis.

p53-mediated inhibition of angiogenesis in diffuse low-grade astrocytomas.

The p53 tumour suppressor protein has long been recognized as the central factor protecting humans from cancer. In this study we evaluated the associations of p53 status and vessel density (angiogenesis) in a set of diffuse low-grade astrocytomas. Immunohistochemistry was performed on 23 diffuse low-grade astrocytomas for CD31 and p53. Mutations in the TP53 gene were identified by PCR amplification of genomic DNA extracted from the indicated tumour tissues. Microvessel counts were done by computer analyses. Intratumoural or peritumoural microvascular hot spots were assessed and analysed from an image taken with a 200x fold magnification. Statistical analysis was performed with Pearson correlation coefficient and Student's t-test. We found that 9/23 (39%) of the astrocytomas stained positive for p53 in the immunohistochemistry. We identified TP53 mutations in 11/23 (47%) of the astrocytomas. No association between micro vessel density (MVD) and p53 immunohistochemical status was found. However, the MVD was significantly increased in p53 mutated low-grade astrocytomas. Furthermore, the absolute vessel number was significantly higher in p53 mutated than in p53 wild-type low-grade astrocytomas. To analyse the molecular background for that epiphenomenon LN229 glioma cells which harbour a TP53 mutation were transfected with a plasmid encoding p53 wild-type and an angiogenesis protein array was performed. We detected a significant increase for thrombospondin-1, coagulation factor III and serpin E1 and a significant decrease of MMP-9 in wild-type p53 transfected LN229 cells. The higher microvessel density and the increased absolute vessel number in p53 mutated tumours supports the importance of p53 for tumour angiogenesis in diffuse low-grade astrocytomas. Our results support the hypothesis that p53 regulates angiogenesis in low-grade astrocytomas.

Daidzein overcomes TRAIL-resistance in malignant glioma cells by modulating the expression of the intrinsic apoptotic inhibitor, bcl-2.

The soy isoflavone Daidzein has been reported to exhibit therapeutic activity in cancer. In this study glioblastoma cells and human astrocytes were treated with Daidzein, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of both. Treatment with subtoxic doses of Daidzein in combination with TRAIL induces rapid apoptosis in glioma cells. Notably, human astrocytes were not affected by the combined treatment consisting of Daidzein and TRAIL. Combined treatment with Daidzein and TRAIL augmented the activation of caspase-9, suggesting that Daidzein modulated the intrinsic apoptotic pathway. Daidzein did not modulate the expression of death receptors, c-FLIP, XIAP and survivin. However, Daidzein down-regulated bcl-2 and over-expression of bcl-2 attenuated apoptosis induced by the combination of Daidzein and TRAIL. In summary, bcl-2 is a key regulator in TRAIL-Daidzein mediated cell death in malignant glioma.

Genistein enhances proteasomal degradation of the short isoform of FLIP in malignant glioma cells and thereby augments TRAIL-mediated apoptosis.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer drug. One obstacle in TRAIL-based therapies is that many cancer cells, including gliomas, are resistant towards TRAIL. In this study one glioblastoma cell line, one human short-term glioblastoma culture and human astrocytes were treated with genistein, tumour necrosis factor-related apoptosis-inducing ligand or the combination of both. Single treatment with genistein or TRAIL does not induce cytotoxicity in malignant glioma cells. However, treatment with genistein in combination with TRAIL induces rapid apoptosis in TRAIL-resistant glioma cells. Notably, normal human astrocytes were not affected by the combination treatment consisting of genistein and TRAIL. Genistein enhanced proteasomal degradation of the short isoform of c-FLIP. Importantly, over-expression of only the short isoform of c-FLIP attenuated genistein TRAIL-mediated cytotoxicity. Taken together, we gave evidence that genistein facilitated TRAIL-mediated apoptosis at the level of the extrinsic apoptotic pathways in malignant glioma cells.

Myricetin sensitizes malignant glioma cells to TRAIL-mediated apoptosis by down-regulation of the short isoform of FLIP and bcl-2.

The flavonoid Myricetin has been reported to exhibit therapeutic activity in cancer. In this study glioblastoma cells and human astrocytes were treated with Myricetin, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of both. Treatment with subtoxic doses of Myricetin in combination with TRAIL induces rapid apoptosis in glioma cells. Notably, human astrocytes were not affected by the combined treatment consisting of Myricetin and TRAIL. Combined treatment with Myricetin and TRAIL augmented the activation of initiator caspases-8/-9 and effector caspases-3/-7. Furthermore, Myricetin down regulated the expression of the long and short isoform of c-FLIP and bcl-2 and over-expression of the short isoform of c-FLIP (S) and bcl-2 attenuated apoptosis induced by the combination of Myricetin and TRAIL. Furthermore, Myricetin did not modulate the mRNA levels of c-FLIP, suggesting that Myricetin modulates the expression of c-FLIP in a posttranscriptional manner. In summary, the short isoform of c-FLIP and bcl-2 are key regulators in TRAIL-Myricetin mediated cell death in malignant glioma.

KAAD-cyclopamine augmented TRAIL-mediated apoptosis in malignant glioma cells by modulating the intrinsic and extrinsic apoptotic pathway.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising cancer therapeutic. The main obstacle in TRAIL-based therapy is that many glioma cells are resistant. In this study glioblastoma cell lines, human glioblastoma short-term cultures and human astrocytes were treated with 3-keto-N-aminoethylaminoethylcaproyldihydrocinnamoyl cyclopamine (KAAD-cyclopamine), tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) or the combination of both. Single treatment with KAAD-cyclopamine or TRAIL does not induce cytotoxicity in malignant glioma cells. However, treatment with KAAD-cyclopamine in combination with TRAIL induces rapid apoptosis in TRAIL-resistant glioma cells. Notably, normal human astrocytes were not affected by the combination treatment consisting of KAAD-cyclopamine and TRAIL. KAAD-cyclopamine led to an upregulation of death receptor 4 and 5 and down-regulation of bcl-2 and c-FLIP. Furthermore, overexpression of both bcl-2 and c-FLIP attenuated KAAD-cyclopamine facilitated TRAIL-mediated apoptosis. Taken together,we provided evidence that KAAD-cyclopamine facilitated TRAIL-mediated apoptosis at the level of the intrinsic and extrinsic apoptotic pathways in malignant glioma cells.