Enhancer hijacking activates GFI1 family oncogenes in medulloblastoma.

Medulloblastoma is a highly malignant paediatric brain tumour currently treated with a combination of surgery, radiation and chemotherapy, posing a considerable burden of toxicity to the developing child. Genomics has illuminated the extensive intertumoral heterogeneity of medulloblastoma, identifying four distinct molecular subgroups. Group 3 and group 4 subgroup medulloblastomas account for most paediatric cases; yet, oncogenic drivers for these subtypes remain largely unidentified. Here we describe a series of prevalent, highly disparate genomic structural variants, restricted to groups 3 and 4, resulting in specific and mutually exclusive activation of the growth factor independent 1 family proto-oncogenes, GFI1 and GFI1B. Somatic structural variants juxtapose GFI1 or GFI1B coding sequences proximal to active enhancer elements, including super-enhancers, instigating oncogenic activity. Our results, supported by evidence from mouse models, identify GFI1 and GFI1B as prominent medulloblastoma oncogenes and implicate 'enhancer hijacking' as an efficient mechanism driving oncogene activation in a childhood cancer.

Preoperative systemic levels of VEGFA, IL-7, IL-17A, and TNF-ß delineate two distinct groups of children with brain tumors.

BACKGROUND: Primary brain tumors are the most common solid tumors in children. Increasing evidence demonstrates diverse intratumoral immune signatures, which are tentatively reflected in peripheral blood. PROCEDURE: Twenty cytokines were analyzed in preoperative plasma samples from five healthy children and 45 children with brain tumors, using a multiplex platform (MesoScale Discovery V-PLEX® ). Tumor types included medulloblastoma (MB), ependymoma, sarcoma, high-grade glioma, pilocytic astrocytoma, and other low-grade gliomas. RESULTS: A panel of four cytokines [VEGFA, interleukin (IL)-7, IL-17A, and tumor necrosis factor (TNF)-ß] delineated two distinct patient groups, identified as VEGFAhigh IL-7high IL-17Alow TNF-ßlow (Group A) and VEGFAlow IL-7low IL-17Ahigh TNF-ßhigh (Group B). Healthy controls and the vast majority of patients with MB were found within Group A, whereas patients with other tumor types were equally distributed between the two groups. Unrelated to A/B affiliation, we detected trends toward increased IL-10 and decreased IL-12/23 and TNF-α in several tumor types. Finally, a small number of patients displayed evidence of enhanced systemic immune activation, including elevated levels of interferon-γ, granulocyte monocyte colony-stimulating factor, IL-6, IL-12/23, and TNF-α. Following tumor resection, cytokine levels in a MB patient approached the levels of healthy controls. CONCLUSIONS: We identify common features and individual differences in the systemic immune profiles of children with brain tumors. Overall, patients with MB displayed a uniform cytokine profile, whereas other tumor diagnoses did not predict systemic immunological status in single patients. Future characterization and monitoring of systemic immune responses in children with brain tumors will have important implications for the development and implementation of immunotherapy.

Aberrant immunostaining pattern of the CD24 glycoprotein in clinical samples and experimental models of pediatric medulloblastomas.

The CD24 glycoprotein is a mediator of neuronal proliferation, differentiation and immune suppression in the normal CNS, and a proposed cancer biomarker in multiple peripheral tumor types. We performed a comparative analysis of CD24 gene expression in a large cohort of pediatric and adult brain tumors (n = 813), and further characterized protein expression in tissue sections (n = 39), primary brain tumor cultures (n = 12) and a novel orthotopic group 3 medulloblastoma xenograft model. Increased CD24 gene expression was demonstrated in ependymomas, medulloblastomas, anaplastic astrocytomas and glioblastomas, although medulloblastomas displayed higher expression than all other tumor entities. Preferential expression of CD24 in medulloblastomas was confirmed at protein level by immunostaining and computerized image analysis of cryosections. Morphologies and immunophenotyping of CD24(+) cells in tissue sections tentatively suggested disparate functions in different tumor subsets. Notably, protein staining of medulloblastoma cells was associated with prominent cytoplasmic and membranous granules, enabling rapid and robust identification of medulloblastoma cells in clinical tissue samples, as well as in experimental model systems. In conclusion, our results implicate CD24 as a clinically and experimentally useful medulloblastoma immunomarker. Although our results encourage further functional studies of CD24 as a potential molecular target in subsets of brain tumors, the promiscuous expression of CD24 in vivo highlights the importance of specificity in the future design of such targeted treatment.

Intratumoral COX-2 inhibition enhances GM-CSF immunotherapy against established mouse GL261 brain tumors.

Immunotherapy has shown effectiveness against experimental malignant brain tumors, but the clinical results have been less convincing most likely due to immunosuppression. Prostaglandin E2 (PGE2 ) is the key immunosuppressive product of cyclooxygenase-2 (COX-2) and increased levels of PGE2 and COX-2 have been shown in several tumor types, including brain tumors. In the current study, we report enhanced cure rate of mice with established mouse GL261 brain tumors when immunized with granulocyte macrophage-colony stimulating factor (GM-CSF) secreting tumor cells and simultaneously treated with the selective COX-2 inhibitors parecoxib systemically (5 mg/kg/day; 69% cure rate) or valdecoxib intratumorally (5.3 µg/kg/day; 63% cure rate). Both combined therapies induced a systemic antitumor response of proliferating CD4(+) and CD8(+) T cells, and further analysis revealed T helper 1 (Th 1) cell supremacy. The GL261 tumor cell line produced low levels of PGE2 in vitro, and co-staining at the tumor site demonstrated that a large fraction of the COX-2(+) cells were derived from CD45(+) immune cells and more specifically macrophages (F4/80(+)), indicating that tumor-infiltrating immune cells constitute the primary source of COX-2 and PGE2 in this model. We conclude that intratumoral COX-2 inhibition potentiates GM-CSF immunotherapy against established brain tumors at substantially lower doses than systemic administration. These findings underscore the central role of targeting COX-2 during immunotherapy and implicate intratumoral COX-2 as the primary target.

Intratumoral temozolomide synergizes with immunotherapy in a T cell-dependent fashion.

Despite temozolomide (TMZ) treatment, the prognosis for patients with glioblastoma multiforme is still dismal. As dose escalation of TMZ is limited by systemic toxicity, intratumoral delivery emerges as an attractive treatment modality, which may sustain cytotoxic drug concentrations intratumorally and induce immunogenic cell death. Both clinical and experimental gliomas have responded to immunotherapy, but the benefit of simultaneous chemo- and immunotherapy is inadequately studied. Here, we monitored survival of GL261-bearing C57BL/6 mice following a 3-day treatment with either intratumoral TMZ (micro-osmotic pump, 4.2 mg/kg/day) or systemic TMZ (i.p. injections, 50 mg/kg/day) alone, or combined with immunization using GM-CSF secreting GL261 cells. Peripheral and intratumoral leukocytes were analyzed by flow cytometry and immunohistochemistry. Intratumoral TMZ induced higher survival rate than systemic TMZ (45 vs. 8%). When T cells were depleted following intratumoral TMZ, the therapeutic effect was completely abrogated (0 % survival). Intratumoral TMZ synergistically increased survival rate of immunized mice (from 25 to 83%), while systemic TMZ failed (0%). While systemic TMZ induced a transient leukopenia, intratumoral TMZ and immunotherapy sustained the proliferation of CD8+ T cells and decreased the number of intratumoral immunosuppressive cells. In conclusion, intratumoral TMZ alone or in combination with immunotherapy could cure glioma-bearing mice, due to attenuation of local immunosuppression and increase in potential effector immune cells.

Absence of Epstein-Barr and cytomegalovirus infection in neuroblastoma cells by standard detection methodologies.

Indications exist in the scientific literature that infection with human herpes family viruses may contribute to the pathogenesis of neuroblastoma (NB). However, systematic investigations regarding viral presence in NB cells have been scarcely reported. Here, the presence of DNA from Epstein-Barr virus (EBV) and human cytomegalovirus (HCMV) was assessed by PCR in 12 NBs, supplemented with RNA in situ hybridization, immunohistochemical detection, and high-throughput DNA sequencing. These standard methods did not detect infection by EBV or HCMV in NB cells in any tumor, while occasional immune cells were positive for EBV RNA or HCMV protein in four cases.

The Prognostic Impact of Intratumoral Aryl Hydrocarbon Receptor in Primary Breast Cancer Depends on the Type of Endocrine Therapy: A Population-Based Cohort Study.

The aryl hydrocarbon receptor (AhR) is a master regulator of multiple pathways involved in breast cancer, and influences the estrogen receptor alpha (ER) and aromatase/CYP19A1. The purpose of this study was to elucidate the interplay between intratumoral levels of AhR and aromatase, patient characteristics (including AhR and CYP19A1 genotypes), clinicopathological features, and prognosis in breast cancer patients receiving adjuvant treatments. A prospective cohort of 1116 patients with primary breast cancer in Sweden, included 2002-2012, was followed until June 30th 2019 (median 8.7 years). Tumor-specific AhR (n=920) and aromatase levels (n=816) were evaluated on tissue microarrays using immunohistochemistry. Associations between cytoplasmatic (AhRcyt) and nuclear (AhRnuc) AhR levels, intratumoral aromatase, clinicopathological features, and prognosis in different treatment groups were analyzed. Low AhRcyt levels (n=183) and positive intratumoral aromatase (n=69) were associated with estrogen receptor (ER)- status and more aggressive tumors. Genotypes were not associated with their respective protein levels. The functional AhR Arg554Lys GG genotype was associated with recurrence-free survival in switch-therapy (sequential tamoxifen/aromatase inhibitors (AI) or AI/tamoxifen) treated patients (HRadj 0.42; 95% CI 0.22-0.83). High AhRcyt levels were associated with longer recurrence-free survival during the first 10 years of follow-up among tamoxifen-only treated patients (HRadj 0.40; 95% CI 0.23-0.71) compared to low AhRcyt levels, whereas an almost inverse association was seen in patients with switch-therapy (P interaction=0.023). Intratumoral aromatase had little prognostic impact. These findings warrant confirmation in an independent cohort, preferably in a randomized clinical trial comparing different endocrine regimens. They might also guide the selection of breast cancer patients for clinical trials with selective AhR modulators.

Re-evaluation of HER2 status in 606 breast cancers-gene protein assay on tissue microarrays versus routine pathological assessment.

Human epidermal growth factor receptor 2 (HER2) status in breast cancer is routinely determined through immunohistochemistry (IHC) and/or in situ hybridisation (ISH) performed on whole tissue sections (WS). The purpose was to evaluate whether a gene protein assay (GPA) combining IHC with ISH, performed on breast cancer tissue microarray (TMA), is suitable for large-scale retrospective HER2 status evaluation. TMAs from 606 tumours from a Swedish population-based cohort (2005-2012) were stained with GPA. GPA IHC on TMA yielded weaker staining than IHC on WS during routine pathological assessment (86.0% agreement). However, final HER2 status agreement between GPA on TMA and WS based on both IHC and ISH was 97.7%. Only 14 tumours were discordant and one tumour with IHC score 1+ on both TMA and WS was HER2 amplified on TMA. In conclusion, GPA on TMA is suitable for large-scale retrospective evaluation of HER2 status.

Patient Characteristics Influence Activated Signal Transducer and Activator of Transcription 3 (STAT3) Levels in Primary Breast Cancer-Impact on Prognosis.

Background: Activated signal transducer and activator of transcription 3 (pSTAT3) is often present in breast cancer, but its prognostic impact is still unclear. We investigated how breast tumor-specific pSTAT3Y705 levels are associated with patient and tumor characteristics and risk of recurrence. Materials and Methods: Primary breast cancer patients without preoperative treatment were included preoperatively. The patients were treated in Lund, Sweden, in 2002-2012 and followed until 2016. Levels of pSTAT3Y705 were evaluated in 867 tumors using tissue microarrays with immunohistochemistry and categorized according to the H-score as negative (0-9; 24.2%), intermediate (10-150; 69.9%), and high (160-300; 5.9%). Results: Patients were followed for up to 13 years, and 137 recurrences (88 distant) were recorded. Higher pSTAT3Y705 levels were associated with patient characteristics including younger age, any alcohol consumption, higher age at first child birth, and smaller body size, as well as tumor characteristics including smaller tumor size, lower histological grade, lymph node negativity, progesterone receptor positivity, and HER2 negativity (all P trends ≤ 0.04). Higher pSTAT3Y705 levels were associated with lower risk of early recurrences (LogRank P trend = 0.10; 5-year LogRank P trend = 0.004) and distant metastases (LogRank P trend = 0.045; 5-year LogRank P trend = 0.0007), but this was not significant in the multivariable models. There was significant effect modification between tamoxifen treatment and pSTAT3Y705 negativity on the recurrence risk in chemonaïve patients with estrogen receptor positive tumors [adjusted hazard ratio (HR) 0.38; P interaction = 0.046]. Conclusion: Higher pSTAT3Y705 levels were associated with several patient and tumor characteristics that are mainly associated with good prognosis and a tendency toward lower risk for early recurrences. In the future, these results may help guide the selection of patients for trials with drugs targeting the STAT3 pathway.

Establishment and characterization of an orthotopic patient-derived Group 3 medulloblastoma model for preclinical drug evaluation.

Medulloblastomas comprise a heterogeneous group of tumours and can be subdivided into four molecular subgroups (WNT, SHH, Group 3 and Group 4) with distinct prognosis, biological behaviour and implications for targeted therapies. Few experimental models exist of the aggressive and poorly characterized Group 3 tumours. In order to establish a reproducible transplantable Group 3 medulloblastoma model for preclinical therapeutic studies, we acquired a patient-derived tumour sphere culture and inoculated low-passage spheres into the cerebellums of NOD-scid mice. Mice developed symptoms of brain tumours with a latency of 17-18 weeks. Neurosphere cultures were re-established and serially transplanted for 3 generations, with a negative correlation between tumour latency and numbers of injected cells. Xenografts replicated the phenotype of the primary tumour, including high degree of clustering in DNA methylation analysis, high proliferation, expression of tumour markers, MYC amplification and elevated MYC expression, and sensitivity to the MYC inhibitor JQ1. Xenografts maintained maintained expression of tumour-derived VEGFA and stromal-derived COX-2. VEGFA, COX-2 and c-Myc are highly expressed in Group 3 compared to other medulloblastoma subgroups, suggesting that these molecules are relevant therapeutic targets in Group 3 medulloblastoma.

A standardized and reproducible protocol for serum-free monolayer culturing of primary paediatric brain tumours to be utilized for therapeutic assays.

In vitro cultured brain tumour cells are indispensable tools for drug screening and therapeutic development. Serum-free culture conditions tentatively preserve the features of the original tumour, but commonly comprise neurosphere propagation, which is a technically challenging procedure. Here, we define a simple, non-expensive and reproducible serum-free cell culture protocol for establishment and propagation of primary paediatric brain tumour cultures as adherent monolayers. The success rates for establishment of primary cultures (including medulloblastomas, atypical rhabdoid tumour, ependymomas and astrocytomas) were 65% (11/17) and 78% (14/18) for sphere cultures and monolayers respectively. Monolayer culturing was particularly feasible for less aggressive tumour subsets, where neurosphere cultures could not be generated. We show by immunofluorescent labelling that monolayers display phenotypic similarities with corresponding sphere cultures and primary tumours, and secrete clinically relevant inflammatory factors, including PGE2, VEGF, IL-6, IL-8 and IL-15. Moreover, secretion of PGE2 was considerably reduced by treatment with the COX-2 inhibitor Valdecoxib, demonstrating the functional utility of our newly established monolayer for preclinical therapeutic assays. Our findings suggest that this culture method could increase the availability and comparability of clinically representative in vitro models of paediatric brain tumours, and encourages further molecular evaluation of serum-free monolayer cultures.

Wnt/ß-catenin pathway regulates MGMT gene expression in cancer and inhibition of Wnt signalling prevents chemoresistance.

The DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT) is commonly overexpressed in cancers and is implicated in the development of chemoresistance. The use of drugs inhibiting MGMT has been hindered by their haematologic toxicity and inefficiency. As a different strategy to inhibit MGMT we investigated cellular regulators of MGMT expression in multiple cancers. Here we show a significant correlation between Wnt signalling and MGMT expression in cancers with different origin and confirm the findings by bioinformatic analysis and immunofluorescence. We demonstrate Wnt-dependent MGMT gene expression and cellular co-localization between active ß-catenin and MGMT. Pharmacological or genetic inhibition of Wnt activity downregulates MGMT expression and restores chemosensitivity of DNA-alkylating drugs in mouse models. These findings have potential therapeutic implications for chemoresistant cancers, especially of brain tumours where the use of temozolomide is frequently used in treatment.

Immunizations with unmodified tumor cells and simultaneous COX-2 inhibition eradicate malignant rat brain tumors and induce a long-lasting CD8(+) T cell memory.

Malignant brain tumors induce pronounced immunosuppression, which diminishes immune responses generated by immunotherapy. Here we report that peripheral immunotherapy, using irradiated unmodified whole tumor cells, and systemic cyclooxygenase-2 inhibition induce cure in glioma-bearing rats (60% cure rate), whereas neither monotherapy was sufficient to cure any animal. Moreover, the combined therapy protected against secondary tumor challenges (89% cure rate) and the secondary immune response was correlated with increased plasma interferon-gamma levels and CD8(+) T cells systemically and intratumorally. In conclusion, we demonstrate that cyclooxygenase-2 inhibition is sufficient to render unmodified tumor cells immunogenic in immunotherapy of experimental brain tumors.

IFNγ in combination with IL-7 enhances immunotherapy in two rat glioma models.

Peripheral immunization, using a combination of interferon-gamma (IFNγ)- and interleukin-7 (IL-7)-producing tumor cells, eradicated 75% of pre-established intracerebral N32 rat glioma tumors, and prolonged survival in the more aggressive RG2 model. Rats immunized with IFNγ- and IL7-transduced N32 cells displayed increases in IFNγ plasma levels and proliferating circulating T cells when compared with rats immunized with N32-wild type cells. Following irradiation, the expression of MHC I and II was high on N32-IFNγ cells, but low on RG2-IFNγ cells. In conclusion, IFNγ and IL-7 immunizations prolong survival in two rat glioma models.

Aluminium based adjuvants and their effects on mitochondria and lysosomes of phagocytosing cells.

Aluminium oxyhydroxide, Al(OH)3 is one of few compounds approved as an adjuvant in human vaccines. However, the mechanism behind its immune stimulating properties is still poorly understood. In vitro co-culture of an aluminium adjuvant and the human monocytic cell line THP-1 resulted in reduced cell proliferation. Inhibition occurred at concentrations of adjuvant several times lower than would be found at the injection site using a vaccine formulation containing an aluminium adjuvant. Based on evaluation of the mitochondrial membrane potential, THP-1 cells showed no mitochondrial rupture after co-culture with the aluminium adjuvant, instead an increase in mitochondrial activity was seen. The THP-1 cells are phagocytosing cells and after co-culture with the aluminium adjuvant the phagosomal pathway was obstructed. Primary or early phagosomes mature into phagolysosomes with an internal pH of 4.5 - 5 and carry a wide variety of hydrolysing enzymes. Co-culture with the aluminium adjuvant yielded a reduced level of acidic vesicles and cathepsin L activity, a proteolytic enzyme of the phagolysosomes, was almost completely inhibited. THP-1 cells are an appropriate in vitro model in order to investigate the mechanism behind the induction of a phagocytosing antigen presenting cell into an inflammatory cell by aluminium adjuvants. Much information will be gained by investigating the phagosomal pathway and what occurs inside the phagosomes and to elucidate the ultimate fate of phagocytosed aluminium particles.