Comprehensive genomic profiling of glioblastoma tumors, BTICs, and xenografts reveals stability and adaptation to growth environments.

Glioblastoma multiforme (GBM) is the most deadly brain tumor, and currently lacks effective treatment options. Brain tumor-initiating cells (BTICs) and orthotopic xenografts are widely used in investigating GBM biology and new therapies for this aggressive disease. However, the genomic characteristics and molecular resemblance of these models to GBM tumors remain undetermined. We used massively parallel sequencing technology to decode the genomes and transcriptomes of BTICs and xenografts and their matched tumors in order to delineate the potential impacts of the distinct growth environments. Using data generated from whole-genome sequencing of 201 samples and RNA sequencing of 118 samples, we show that BTICs and xenografts resemble their parental tumor at the genomic level but differ at the mRNA expression and epigenomic levels, likely due to the different growth environment for each sample type. These findings suggest that a comprehensive genomic understanding of in vitro and in vivo GBM model systems is crucial for interpreting data from drug screens, and can help control for biases introduced by cell-culture conditions and the microenvironment in mouse models. We also found that lack of MGMT expression in pretreated GBM is linked to hypermutation, which in turn contributes to increased genomic heterogeneity and requires new strategies for GBM treatment.

Correction: Combined poly-ADP ribose polymerase and ataxia-telangiectasia mutated/Rad3-related inhibition targets ataxia-telangiectasia mutated-deficient lung cancer cells.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. This has now been corrected in both the PDF and HTML versions of the Article.

Combined poly-ADP ribose polymerase and ataxia-telangiectasia mutated/Rad3-related inhibition targets ataxia-telangiectasia mutated-deficient lung cancer cells.

BACKGROUND: Up to 40% of lung adenocarcinoma have been reported to lack ataxia-telangiectasia mutated (ATM) protein expression. We asked whether ATM-deficient lung cancer cell lines are sensitive to poly-ADP ribose polymerase (PARP) inhibitors and determined the mechanism of action of olaparib in ATM-deficient A549 cells. METHODS: We analysed drug sensitivity data for olaparib and talazoparib in lung adenocarcinoma cell lines from the Genomics of Drug Sensitivity in Cancer (GDSC) project. We deleted ATM from A549 lung adenocarcinoma cells using CRISPR/Cas9 and determined the effects of olaparib and the ATM/Rad3-related (ATR) inhibitor VE-821 on cell viability. RESULTS: IC50 values for both olaparib and talazoparib positively correlated with ATM mRNA levels and gene amplification status in lung adenocarcinoma cell lines. ATM mutation was associated with a significant decrease in the IC50 for olaparib while a similar trend was observed for talazoparib. A549 cells with deletion of ATM were sensitive to ionising radiation and olaparib. Olaparib induced phosphorylation of DNA damage markers and reversible G2 arrest in ATM-deficient cells, while the combination of olaparib and VE-821 induced cell death. CONCLUSIONS: Patients with tumours characterised by ATM-deficiency may benefit from treatment with a PARP inhibitor in combination with an ATR inhibitor.

Fractal analysis of nuclear histology integrates tumor and stromal features into a single prognostic factor of the oral cancer microenvironment.

BACKGROUND: The lack of prognostic biomarkers in oral squamous cell carcinoma (OSCC) has hampered treatment decision making and survival in OSCC remains poor. Histopathological features are used for prognostication in OSCC and, although useful for predicting risk, manual assessment of histopathology is subjective and labour intensive. In this study, we propose a method that integrates multiple histopathological features of the tumor microenvironment into a single, digital pathology-based biomarker using nuclear fractal dimension (nFD) analysis. METHODS: One hundred and seven consecutive OSCC patients diagnosed between 1998 and 2006 in Calgary, Canada were included in the study. nFD scores were generated from DAPI-stained images of tissue microarray (TMA) cores. Ki67 protein expression was measured in the tumor using fluorescence immunohistochemistry (IHC) and automated quantitative analysis (AQUA®). Lymphocytic infiltration (LI) was measured in the stroma from haematoxylin-eosin (H&E)-stained TMA slides by a pathologist. RESULTS: Twenty-five (23.4%) and 82 (76.6%) patients were classified as high and low nFD, respectively. nFD was significantly associated with pathological tumor-stage (pT-stage; P = 0.01) and radiation treatment (RT; P = 0.01). High nFD of the total tumor microenvironment (stroma plus tumor) was significantly associated with improved disease-specific survival (DSS; P = 0.002). No association with DSS was observed when nFD of either the tumor or the stroma was measured separately. pT-stage (P = 0.01), pathological node status (pN-status; P = 0.02) and RT (P = 0.03) were also significantly associated with DSS. In multivariate analysis, nFD remained significantly associated with DSS [HR 0.12 (95% CI 0.02-0.89, P = 0.04)] in a model adjusted for pT-stage, pN-status and RT. We also found that high nFD was significantly associated with high tumor proliferation (P < 0.0001) and high LI (P < 0.0001), factors that we and others have shown to be associated with improved survival in OSCC. CONCLUSIONS: We provide evidence that nFD analysis integrates known prognostic factors from the tumor microenvironment, such as proliferation and immune infiltration, into a single digital pathology-based biomarker. Prospective validation of our results could establish nFD as a valuable tool for clinical decision making in OSCC.

Targeting Oral Squamous Cell Carcinoma with Combined Polo-Like-Kinase-1 Inhibitors and γ-Radiation Therapy.

Polo-like-kinase-1 (PLK-1) is a serine/threonine kinase that regulates the cell cycle and acts as an oncogene in multiple cancers, including oral squamous cell carcinoma (OSCC). The loss of PLK-1 can inhibit growth and induce apoptosis, making it an attractive therapeutic target in OSCC. We evaluated the efficacy of PLK-1 inhibitors as novel, targeted therapeutics in OSCC. PLK-1 inhibition using BI6727 (volasertib) was found to affect cell death at low nanomolar concentrations in most tested OSCC cell lines, but not in normal oral keratinocytes. In cell lines resistant to volasertib alone, pre-treatment with radiotherapy followed by volasertib reduced cell viability and induced apoptosis. The combinatorial efficacy of volasertib and radiotherapy was replicated in xenograft mouse models. These findings highlight the potential of adding PLK-1 inhibitors to adjuvant therapy regimens in OSCC.

Head and neck cancer: from anatomy to biology.

The 20th century saw great advances in anatomy-based (surgery and radiotherapy) and chemotherapy approaches for treating head and neck squamous cell carcinoma (HNSCC) and improving quality of life (QoL). However, despite these advances, the survival rate in HNSCC remains at ∼50%. Front-line treatments often cause severe toxicity and debilitating long-term impacts on QoL. In recent decades, dramatic advances have been made in our knowledge of fundamental tumor biology and signaling pathways that contribute to oncogenesis and cancer progression. These insights are presenting unprecedented opportunities to develop more effective and less toxic treatments that are specific to particular molecular targets. This review discusses some of the major, potentially targetable, molecular pathways associated with head and neck carcinogenesis. We present the general mechanism underlying the functional components for each signaling pathway, discuss how these components are aberrantly regulated in HNSCC and describe their potential as therapeutic targets. We have restricted our discussion to "drug-able targets" such as oncogenes including those associated with HPV, tumor hypoxia and microRNAs and present these changes in the context of HNSCC patient care. The specific targeting of these pathways to achieve cancer control/remission and reduce toxicity is now challenging conventional treatment paradigms in HNSCC. This new "biologic era" is transforming our ability to target causal pathways and improve survival outcomes in HNSCC.

PDGF gene expression and p53 alterations contribute to the biology of diffuse astrocytic gliomas.

Diffuse, histologically lower grade astrocytomas of adults (LGAs) are classified based on the mutational status of the isocitrate dehydrogenase (IDH) genes. While wild-type (WT) LGAs often evolve quickly to glioblastoma (GBM), mutant tumors typically follow an indolent course. To find possible effectors of these different behaviors, we compared their respective transcriptomes. Unlike mutant LGAs, platelet-derived growth factor (PDGF) signaling was significantly enriched in WT tumors, and PDGFA was the top overexpressed gene in the pathway. Moreover, methylation of the PDGFA and PDGFD promoters emerged as a possible mechanism for their low expression in mutant tumors. Copy number gain of chromosome 7 co-occurred with high expression of PDGFA in WT cases, and high expression of PDGFA was associated with aneuploidy, extracellular matrix (ECM)-related immunosuppressive features and poor prognosis. We also noted that high PDGFA expression in WT cases occurred irrespective of tumor grade and that multiple mechanisms of p53 pathway inactivation accompanied progression to GBM in PDGFA-overexpressing tumors. Conversely, TP53 point mutations were an early and constant feature of mutant LGAs. Our results suggest that members of the PDGF gene family, in concert with different p53 pathway alterations, underlie LGA behaviors.

Development and validation of a 21-gene prognostic signature in neuroblastoma.

Survival outcomes for patients with neuroblastoma vary markedly and reliable prognostic markers and risk stratification tools are lacking. We sought to identify and validate a transcriptomic signature capable of predicting risk of mortality in patients with neuroblastoma. The TARGET NBL dataset (n = 243) was used to develop the model and two independent cohorts, E-MTAB-179 (n = 478) and GSE85047 (n = 240) were used as validation sets. EFS was the primary outcome and OS was the secondary outcome of interest for all analysis. We identified a 21-gene signature capable of stratifying neuroblastoma patients into high and low risk groups in the E-MTAB-179 (HR 5.87 [3.83-9.01], p < 0.0001, 5 year AUC 0.827) and GSE85047 (HR 3.74 [2.36-5.92], p < 0.0001, 5 year AUC 0.815) validation cohorts. Moreover, the signature remained independent of known clinicopathological variables, and remained prognostic within clinically important subgroups. Further, the signature was effectively incorporated into a risk model with clinicopathological variables to improve prognostic performance across validation cohorts (Pooled Validation HR 6.93 [4.89-9.83], p < 0.0001, 5 year AUC 0.839). Similar prognostic utility was also demonstrated with OS. The identified signature is a robust independent predictor of EFS and OS outcomes in neuroblastoma patients and can be combined with clinically utilized clinicopathological variables to improve prognostic performance.

Modulation of Reoviral Cytolysis (II): Cellular Stemness.

Oncolytic viruses (OVs) are an emerging cancer therapeutic that are intended to act by selectively targeting and lysing cancerous cells and by stimulating anti-tumour immune responses, while leaving normal cells mainly unaffected. Reovirus is a well-studied OV that is undergoing advanced clinical trials and has received FDA approval in selected circumstances. However, the mechanisms governing reoviral selectivity are not well characterised despite many years of effort, including those in our accompanying paper where we characterize pathways that do not consistently modulate reoviral cytolysis. We have earlier shown that reovirus is capable of infecting and lysing both certain types of cancer cells and also cancer stem cells, and here we demonstrate its ability to also infect and kill healthy pluripotent stem cells (PSCs). This led us to hypothesize that pathways responsible for stemness may constitute a novel route for the modulation of reoviral tropism. We find that reovirus is capable of killing both murine and human embryonic and induced pluripotent stem cells. Differentiation of PSCs alters the cells' reoviral-permissive state to a resistant one. In a breast cancer cell line that was resistant to reoviral oncolysis, induction of pluripotency programming rendered the cells permissive to cytolysis. Bioinformatic analysis indicates that expression of the Yamanaka pluripotency factors may be associated with regulating reoviral selectivity. Mechanistic insights from these studies will be useful for the advancement of reoviral oncolytic therapy.

Single-Cell Spatial Analysis Identifies Regulators of Brain Tumor-Initiating Cells.

Glioblastomas (GBM) are aggressive brain tumors with extensive intratumoral heterogeneity that contributes to treatment resistance. Spatial characterization of GBMs could provide insights into the role of the brain tumor microenvironment in regulating intratumoral heterogeneity. Here, we performed spatial transcriptomic and single-cell analyses of the mouse and human GBM microenvironment to dissect the impact of distinct anatomical regions of brains on GBM. In a syngeneic GBM mouse model, spatial transcriptomics revealed that numerous extracellular matrix (ECM) molecules, including biglycan, were elevated in areas infiltrated with brain tumor-initiating cells (BTIC). Single-cell RNA sequencing and single-cell assay for transposase-accessible chromatin using sequencing showed that ECM molecules were differentially expressed by GBM cells based on their differentiation and cellular programming phenotypes. Exogeneous biglycan or overexpression of biglycan resulted in a higher proliferation rate of BTICs, which was associated mechanistically with low-density lipoprotein receptor-related protein 6 (LRP6) binding and activation of the Wnt/ß-catenin pathway. Biglycan-overexpressing BTICs developed into larger tumors and displayed mesenchymal phenotypes when implanted intracranially in mice. This study points to the spatial heterogeneity of ECM molecules in GBM and suggests that the biglycan-LRP6 axis could be a therapeutic target to curb tumor growth. SIGNIFICANCE: Characterization of the spatial heterogeneity of glioblastoma identifies regulators of brain tumor-initiating cells and tumor growth that could serve as candidates for therapeutic interventions to improve the prognosis of patients.

NCBP2 and TFRC are novel prognostic biomarkers in oral squamous cell carcinoma.

There are few prognostic biomarkers and targeted therapeutics currently in use for the clinical management of oral squamous cell carcinoma (OSCC) and patient outcomes remain poor in this disease. A majority of mutations in OSCC are loss-of-function events in tumour suppressor genes that are refractory to conventional modes of targeting. Interestingly, the chromosomal segment 3q22-3q29 is amplified in many epithelial cancers, including OSCC. We hypothesized that some of the 468 genes located on 3q22-3q29 might be drivers of oral carcinogenesis and could be exploited as potential prognostic biomarkers and therapeutic targets. Our integrative analysis of copy number variation (CNV), gene expression and clinical data from The Cancer Genome Atlas (TCGA), identified two candidate genes: NCBP2, TFRC, whose expression positively correlates with worse overall survival (OS) in HPV-negative OSCC patients. Expression of NCBP2 and TFRC is significantly higher in tumour cells compared to most normal human tissues. High NCBP2 and TFRC protein abundance is associated with worse overall, disease-specific survival, and progression-free interval in an in-house cohort of HPV-negative OSCC patients. Finally, due to a lack of evidence for the role of NCBP2 in carcinogenesis, we tested if modulating NCBP2 levels in human OSCC cell lines affected their carcinogenic behaviour. We found that NCBP2 depletion reduced OSCC cell proliferation, migration, and invasion. Differential expression analysis revealed the upregulation of several tumour-promoting genes in patients with high NCBP2 expression. We thus propose both NCBP2 and TFRC as novel prognostic and potentially therapeutic biomarkers for HPV-negative OSCC.

Spatial transcriptomics reveals distinct and conserved tumor core and edge architectures that predict survival and targeted therapy response.

The spatial organization of the tumor microenvironment has a profound impact on biology and therapy response. Here, we perform an integrative single-cell and spatial transcriptomic analysis on HPV-negative oral squamous cell carcinoma (OSCC) to comprehensively characterize malignant cells in tumor core (TC) and leading edge (LE) transcriptional architectures. We show that the TC and LE are characterized by unique transcriptional profiles, neighboring cellular compositions, and ligand-receptor interactions. We demonstrate that the gene expression profile associated with the LE is conserved across different cancers while the TC is tissue specific, highlighting common mechanisms underlying tumor progression and invasion. Additionally, we find our LE gene signature is associated with worse clinical outcomes while TC gene signature is associated with improved prognosis across multiple cancer types. Finally, using an in silico modeling approach, we describe spatially-regulated patterns of cell development in OSCC that are predictably associated with drug response. Our work provides pan-cancer insights into TC and LE biology and interactive spatial atlases ( http://www.pboselab.ca/spatial_OSCC/ ; http://www.pboselab.ca/dynamo_OSCC/ ) that can be foundational for developing novel targeted therapies.

Bax expression measured by AQUAnalysis is an independent prognostic marker in oral squamous cell carcinoma.

BACKGROUND: Resistance to apoptosis is a hallmark of cancer and proteins regulating apoptosis have been proposed as prognostic markers in several malignancies. However, the prognostic impact of apoptotic markers has not been consistently demonstrated in oral squamous cell carcinoma (OSCC). This inconsistency in reported associations between apoptotic proteins and prognosis can be partly attributed to the intrinsic low resolution and misclassification associated with manual, semi-quantitative methods of biomarker expression measurement. The aim of this study was to examine the association between apoptosis-regulating proteins and clinical outcomes in oral squamous cell carcinoma (OSCC) using the quantitative fluorescence immunohistochemistry (IHC) based AQUAnalysis technique. METHODS: Sixty-nine OSCC patients diagnosed between 1998-2005 in Calgary, Alberta, Canada were included in the study. Clinical data were obtained from the Alberta Cancer Registry and chart review. Tissue microarrays (TMAs) were assembled from triplicate cores of formalin-fixed paraffin embedded pre-treatment tumour tissue. Bax, Bcl-2 and Bcl-XL protein expression was quantified using fluorescent IHC and AQUA technology in normal oral cavity squamous epithelium (OCSE) and OSCC tumour samples. Survival was analyzed using Kaplan-Meier plots and the Cox proportional hazard model. RESULTS: Bax expression was predominantly nuclear in OCSE and almost exclusively cytoplasmic in OSCC. No similar differences in localization were observed for Bcl-2 or Bcl-XL. Only Bax expression associated with disease-specific survival (DSS), with 5-year survival estimates of 85.7% for high Bax versus 50.3% for low Bax (p = 0.006), in univariate analysis. High Bax expression was also significantly associated with elevated Ki67 expression, indicating that increased proliferation might lead to an improved response to radiotherapy in patients with elevated Bax expression. In multivariate analyses, Bax protein expression remained an independent predictor of DSS in OSCC [HR 0.241 (0.078-0.745), p = 0.013]. CONCLUSIONS: The AQUA technique used in our study eliminates observer bias and provides reliable and reproducible estimates for biomarker expression. AQUA also provides essential measures of quality control that cannot be achieved with manual biomarker scoring techniques. Our results support the use of Bax protein expression as a prognostic marker in conjunction with other clinico-pathological variables when designing personalized treatment strategies for OSCC patients.

Identification of Altered Primary Immunodeficiency-Associated Genes and Their Implications in Pediatric Cancers.

BACKGROUND: Cancer is the leading cause of disease-related mortality in children and malignancies are more frequently observed in individuals with primary immunodeficiencies (PIDs). This study aimed to identify and highlight the molecular mechanisms, such as oncogenesis and immune evasion, by which PID-related genes may lead to the development of pediatric cancers. METHOD: We implemented a novel bioinformatics framework using patient data from the TARGET database and performed a comparative transcriptome analysis of PID-related genes in pediatric cancers between normal and cancer tissues, gene ontology enrichment, and protein-protein interaction analyses, and determined the prognostic impacts of commonly mutated and differentially expressed PID-related genes. RESULTS: From the Fulgent Genetics Comprehensive Primary Immunodeficiency panel of 472 PID-related genes, 89 genes were significantly differentially expressed between normal and cancer tissues, and 20 genes were mutated in two or more patients. Enrichment analysis highlighted many immune system processes as well as additional pathways in the mutated PID-related genes related to oncogenesis. Survival outcomes for patients with altered PID-related genes were significantly different for 75 of the 89 DEGs, often resulting in a poorer prognosis. CONCLUSIONS: Overall, multiple PID-related genes demonstrated the connection between PIDs and cancer development and should be studied further, with hopes of identifying new therapeutic targets.

Immune-based classification of HPV-associated oropharyngeal cancer with implications for biomarker-driven treatment de-intensification.

BACKGROUND: There is significant interest in treatment de-escalation for human papillomavirus-associated (HPV+) oropharyngeal squamous cell carcinoma (OPSCC) patients given the generally favourable prognosis. However, 15-30% of patients recur after primary treatment, reflecting a need for improved risk-stratification tools. We sought to develop a molecular test to risk stratify HPV+ OPSCC patients. METHODS: We created an immune score (UWO3) associated with survival outcomes in six independent cohorts comprising 906 patients, including blinded retrospective and prospective external validations. Two aggressive radiation de-escalation cohorts were used to assess the ability of UWO3 to identify patients who recur. Multivariate Cox models were used to assess the associations between the UWO3 immune class and outcomes. FINDINGS: A three-gene immune score classified patients into three immune classes (immune rich, mixed, or immune desert) and was strongly associated with disease-free survival in six datasets, including large retrospective and prospective datasets. Pooled analysis demonstrated that the immune rich group had superior disease-free survival compared to the immune desert (HR = 9.0, 95% CI: 3.2-25.5, P = 3.6 × 10-5) and mixed (HR = 6.4, 95% CI: 2.2-18.7, P = 0.006) groups after adjusting for age, sex, smoking status, and AJCC8 clinical stage. Finally, UWO3 was able to identify patients from two small treatment de-escalation cohorts who remain disease-free after aggressive de-escalation to 30 Gy radiation. INTERPRETATION: With additional prospective validation, the UWO3 score could enable biomarker-driven clinical decision-making for patients with HPV+ OPSCC based on robust outcome prediction across six independent cohorts. Prospective de-escalation and intensification clinical trials are currently being planned. FUNDING: CIHR, European Union, and the NIH.

Multi-tyrosine kinase inhibitors in preclinical studies for pediatric CNS AT/RT: Evidence for synergy with Topoisomerase-I inhibition.

BACKGROUND: Currently, Atypical Teratoid Rhabdoid Tumor (AT/RT) constitutes one of the most difficult to treat malignancies in pediatrics. Hence, new knowledge of potential targets for therapeutics and the development of novel treatment approaches are urgently needed. We have evaluated the presence of cytokine pathways and the effects of two clinically available multi-tyrosine kinase inhibitors for cytotoxicity, target modulation and drug combinability against AT/RT cell lines. RESULTS: AT/RT cell lines expressed measurable quantities of VEGF, FGF, PDGF and SDF-1, although the absolute amounts varied between the cell lines. The targeted receptor tyrosine kinase inhibitor sorafenib inhibited the key signaling molecule Erk, which was activated following the addition of own conditioned media, suggesting the existence of autocrine/paracrine growth stimulatory pathways. The multi-tyrosine kinase inhibitors sorafenib and sunitinib also showed significant growth inhibition of AT/RT cells and their activity was enhanced by combination with the topoisomerase inhibitor, irinotecan. The loss of cytoplasmic NF-kappa-B in response to irinotecan was diminished by sorafenib, providing evidence for a possible benefit for this drug combination. CONCLUSIONS: In addition to previously described involvement of insulin like growth factor (IGF) family of cytokines, a multitude of other growth factors may contribute to the growth and survival of AT/RT cells. However, consistent with the heterogeneous nature of this tumor, quantitative and qualitative differences may exist among different tumor samples. Multi-tyrosine kinase inhibitors appear to have effective antitumor activity against all cell lines studied. In addition, the target modulation studies and drug combinability data provide the groundwork for additional studies and support the evaluation of these agents in future treatment protocols.

Fibrinogen in the glioblastoma microenvironment contributes to the invasiveness of brain tumor-initiating cells.

Glioblastomas (GBMs) are highly aggressive, recurrent, and lethal brain tumors that are maintained via brain tumor-initiating cells (BTICs). The aggressiveness of BTICs may be dependent on the extracellular matrix (ECM) molecules that are highly enriched within the GBM microenvironment. Here, we investigated the expression of ECM molecules in GBM patients by mining the transcriptomic databases and also staining human GBM specimens. RNA levels for fibronectin, brevican, versican, heparan sulfate proteoglycan 2 (HSPG2), and several laminins were high in GBMs compared to normal brain, and this was corroborated by immunohistochemistry. While fibrinogen transcript was at normal level in GBM, its protein immunoreactivity was prominent within GBM tissues. These ECM molecules in tumor specimens were in proximity to, and surrounding BTICs. In culture, fibronectin and pan-laminin induced the adhesion of BTICs onto the plastic substratum. However, fibrinogen increased the size of the BTIC spheres by facilitating the adhesive property, motility, and invasiveness of BTICs. These features of elevated invasiveness were corroborated in resected GBM specimens by the close proximity of fibrinogen with matrix metalloproteinase (MMP)-2 and-9, which are proteases implicated in metastasis. Moreover, the effect of fibrinogen-induced invasiveness was attenuated in BTICs where MMP-2 and -9 have been inhibited with siRNAs or pharmacological inhibitors. Our results implicate fibrinogen in GBM as a mediator of the invasive properties of BTICs, and as a target for therapy to reduce BTIC tumorigenecity.

PD-1 independent of PD-L1 ligation promotes glioblastoma growth through the NFκB pathway.

Brain tumor­initiating cells (BTICs) drive glioblastoma growth through not fully understood mechanisms. Here, we found that about 8% of cells within the human glioblastoma microenvironment coexpress programmed cell death 1 (PD-1) and BTIC marker. Gain- or loss-of-function studies revealed that tumor-intrinsic PD-1 promoted proliferation and self-renewal of BTICs. Phosphorylation of tyrosines within the cytoplasmic tail of PD-1 recruited Src homology 2­containing phosphatase 2 and activated the nuclear factor kB in BTICs. Notably, the tumor-intrinsic promoting effects of PD-1 did not require programmed cell death ligand 1(PD-L1) ligation; thus, the therapeutic antibodies inhibiting PD-1/PD-L1 interaction could not overcome the growth advantage of PD-1 in BTICs. Last, BTIC-intrinsic PD-1 accelerated intracranial tumor growth, and this occurred in mice lacking T and B cells. These findings point to a critical role for PD-1 in BTICs and uncover a nonimmune resistance mechanism of patients with glioblastoma to PD-1­ or PD-L1­blocking therapies.

The KrasG12D;Trp53fl/fl murine model of undifferentiated pleomorphic sarcoma is macrophage dense, lymphocyte poor, and resistant to immune checkpoint blockade.

Sarcomas are rare, difficult to treat, mesenchymal lineage tumours that affect children and adults. Immunologically-based therapies have improved outcomes for numerous adult cancers, however, these therapeutic strategies have been minimally effective in sarcoma so far. Clinically relevant, immunologically-competent, and transplantable pre-clinical sarcoma models are essential to advance sarcoma immunology research. Herein we show that Cre-mediated activation of KrasG12D, and deletion of Trp53, in the hindlimb muscles of C57Bl/6 mice results in the highly penetrant, rapid onset undifferentiated pleomorphic sarcomas (UPS), one of the most common human sarcoma subtypes. Cell lines derived from spontaneous UPS tumours can be reproducibly transplanted into the hindlimbs or lungs of naïve, immune competent syngeneic mice. Immunological characterization of both spontaneous and transplanted UPS tumours demonstrates an immunologically-'quiescent' microenvironment, characterized by a paucity of lymphocytes, limited spontaneous adaptive immune pathways, and dense macrophage infiltrates. Macrophages are the dominant immune population in both spontaneous and transplanted UPS tumours, although compared to spontaneous tumours, transplanted tumours demonstrate increased spontaneous lymphocytic infiltrates. The growth of transplanted UPS tumours is unaffected by host lymphocyte deficiency, and despite strong expression of PD-1 on tumour infiltrating lymphocytes, tumours are resistant to immunological checkpoint blockade. This spontaneous and transplantable immune competent UPS model will be an important experimental tool in the pre-clinical development and evaluation of novel immunotherapeutic approaches for immunologically cold soft tissue sarcomas.

The inhibitor of growth 1 (ING1) is involved in trichostatin A-induced apoptosis and caspase 3 signaling in p53-deficient glioblastoma cells.

Prognosis for patients with glioblastoma multiforme (GBM) is poor. Inhibitors of histone deacetylases (HDACi) like trichostatin A (TSA) are promising alternatives to conventional treatment. Deficient tumor suppressor functions, such as TP53 mutations and p14(ARF)/p16(INK4a) deletions, are characteristic for GBM and can cause resistance to DNA damaging agents such as cisplatin and to HDACi like TSA. The type II tumor suppressor Inhibitor of growth 1 (ING1) is involved in DNA damage response and histone modification. We have previously shown that ING1 is downregulated in GBM and involved in glioma-induced angiogenesis and in cisplatin-induced apoptosis in malignant glioma cells. Hence, the goal of our present study was to investigate whether TSA affects ING1 protein expression and also whether modulating ING1 levels affects TSA-induced apoptosis in malignant glioma cells that contain deficient p53 function and inactive pl4(ARF)/p16(INK4a) signaling. If so, we asked, which apoptotic pathway might be the major mediator beyond this interaction. To test whether ING1 proteins function in TSA-induced apoptosis in GBM, we analyzed TSA effects in LN229 GBM cells, which harbor TP53 mutations and INK4a deletion, following ING1 knockdown by siRNA. Expression of ING1, acetylated core histones H3 and H4, and the proapoptotic proteins caspase 3 and Fas-associated death domain (FADD) was determined by Western blotting. Percentages of apoptotic cells were obtained by flow cytometry. TSA induced the major ING1 isoform p33(ING1b) and increased levels of both histone acetylation and apoptosis in LN229 cells. ING1 knockdown cells revealed marked resistance to TSA-induced apoptosis, impairment of caspase 3 activation, and suppression of FADD. The data suggest that ING1 contributes to TSA-induced apoptosis in GBM cells with deficient p53 and p14(ARF)/p16(INK4a) functions, possibly by regulating FADD/caspase 3 signaling.