BRAF V600E in a preclinical model of pleomorphic Xanthoastrocytoma: Analysis of the tumor microenvironment and immune cell infiltration dynamics in vivo.

Low-grade glioma (LGG) is the most common brain tumor affecting pediatric patients (pLGG) and BRAF mutations constitute the most frequent genetic alterations. Within the spectrum of pLGGs, approximately 70%-80% of pediatric patients diagnosed with transforming pleomorphic xanthoastrocytoma (PXA) harbor the BRAF V600E mutation. However, the impact of glioma BRAF V600E cell regulation of tumor-infiltrating immune cells and their contribution to tumor progression remains unclear. Moreover, the efficacy of BRAF inhibitors in treating pLGGs is limited compared with their impact on BRAF-mutated melanoma. Here we report a novel immunocompetent RCAS-BRAF V600E murine glioma model. Pathological assessment indicates this model seems to be consistent with diffuse gliomas and morphological features of PXA. Our investigations revealed distinct immune cell signatures associated with increased trafficking and activation within the tumor microenvironment (TME). Intriguingly, immune system activation within the TME also generated a pronounced inflammatory response associated with dysfunctional CD8+ T cells, increased presence of immunosuppressive myeloid cells and regulatory T cells. Further, our data suggests tumor-induced inflammatory processes, such as cytokine storm. These findings suggest a complex interplay between tumor progression and the robust inflammatory response within the TME in preclinical BRAF V600E LGGs, which may significantly influence animal survival.

Genetically modified IL2 bone-marrow-derived myeloid cells reprogram the glioma immunosuppressive tumor microenvironment.

Gliomas are one of the leading causes of cancer-related death in the adolescent and young adult (AYA) population. Two-thirds of AYA glioma patients are affected by low-grade gliomas (LGGs), but there are no specific treatments. Malignant progression is supported by the immunosuppressive stromal component of the tumor microenvironment (TME) exacerbated by M2 macrophages and a paucity of cytotoxic T cells. A single intravenous dose of engineered bone-marrow-derived myeloid cells that release interleukin-2 (GEMys-IL2) was used to treat mice with LGGs. Our results demonstrate that GEMys-IL2 crossed the blood-brain barrier, infiltrated the TME, and reprogrammed the immune cell composition and transcriptome. Moreover, GEMys-IL2 extended survival in an LGG immunocompetent mouse model. Here, we report the efficacy of an in vivo approach that demonstrates the potential for a cell-mediated innate immunotherapy designed to enhance the recruitment of activated effector T and natural killer cells within the glioma TME.

Therapeutic utility of engineered myeloid cells in the tumor microenvironment.

Despite promising results shown in hematologic tumors, immunotherapies for the treatment of solid tumors have mostly failed so far. The immunosuppressive tumor microenvironment and phenotype of tumor infiltrating macrophages are among the more prevalent reasons for this failure. Tumor associated macrophages (TAMs, M2-macrophages) are circulating myeloid cells recruited to the local tumor microenvironment, and together with regulatory T cells (T-regs), are reprogrammed to become immune suppressive. This results in the inactivation or hampered recruitment of cytotoxic CD8 + T and Natural Killer (NK) cells. Recently, attempts have been made to try to leverage specific myeloid functions and properties, including their ability to reach the TME and to mediate the phagocytosis of cancer cells. Additionally, myeloid cells have been used for drug delivery and reprogramming the tumor microenvironment in cancer patients. This approach, together with the advancements in genome editing, paved the way for the development of novel cell-mediated immunotherapies. This article focuses on the latest studies that detail the therapeutic properties of genetically engineered or pharmacologically modulated myeloid cells in cancer preclinical models, limitations, pitfalls, and evaluations of these approaches in patients with cancer.

Single-cell RNA sequencing reveals immunosuppressive myeloid cell diversity during malignant progression in a murine model of glioma.

Recent studies have shown the importance of the dynamic tumor microenvironment (TME) in high-grade gliomas (HGGs). In particular, myeloid cells are known to mediate immunosuppression in glioma; however, it is still unclear if myeloid cells play a role in low-grade glioma (LGG) malignant progression. Here, we investigate the cellular heterogeneity of the TME using single-cell RNA sequencing in a murine glioma model that recapitulates the malignant progression of LGG to HGG. LGGs show increased infiltrating CD4+ and CD8+ T cells and natural killer (NK) cells in the TME, whereas HGGs abrogate this infiltration. Our study identifies distinct macrophage clusters in the TME that show an immune-activated phenotype in LGG but then evolve to an immunosuppressive state in HGG. We identify CD74 and macrophage migration inhibition factor (MIF) as potential targets for these distinct macrophage populations. Targeting these intra-tumoral macrophages in the LGG stage may attenuate their immunosuppressive properties and impair malignant progression.

Myeloid cell heterogeneity in the tumor microenvironment and therapeutic implications for childhood central nervous system (CNS) tumors.

Central nervous system (CNS) tumors are the most common type of solid tumors in children and the leading cause of cancer deaths in ages 0-14. Recent advances in the field of tumor biology and immunology have underscored the disparate nature of these distinct CNS tumor types. In this review, we briefly introduce pediatric CNS tumors and discuss various components of the TME, with a particular focus on myeloid cells. Although most studies regarding myeloid cells have been done on adult CNS tumors and animal models, we discuss the role of myeloid cell heterogeneity in pediatric CNS tumors and describe how these cells may contribute to tumorigenesis and treatment response. In addition, we present studies within the last 5 years that highlight human CNS tumors, the utility of various murine CNS tumor models, and the latest multi-dimensional tools that can be leveraged to investigate myeloid cell infiltration in young adults and children diagnosed with select CNS tumors.

Disruption of DNA Repair and Survival Pathways through Heat Shock Protein Inhibition by Onalespib to Sensitize Malignant Gliomas to Chemoradiation Therapy.

PURPOSE: Proficient DNA repair by homologous recombination (HR) facilitates resistance to chemoradiation in glioma stem cells (GSC). We evaluated whether compromising HR by targeting HSP90, a molecular chaperone required for the function of key HR proteins, using onalespib, a long-acting, brain-penetrant HSP90 inhibitor, would sensitize high-grade gliomas to chemoradiation in vitro and in vivo. EXPERIMENTAL DESIGN: The ability of onalespib to deplete HR client proteins, impair HR repair capacity, and sensitize glioblastoma (GBM) to chemoradiation was evaluated in vitro in GSCs, and in vivo using zebrafish and mouse intracranial glioma xenograft models. The effects of HSP90 inhibition on the transcriptome and cytoplasmic proteins was assessed in GSCs and in ex vivo organotypic human glioma slice cultures. RESULTS: Treatment with onalespib depleted CHK1 and RAD51, two key proteins of the HR pathway, and attenuated HR repair, sensitizing GSCs to the combination of radiation and temozolomide (TMZ). HSP90 inhibition reprogrammed the transcriptome of GSCs and broadly altered expression of cytoplasmic proteins including known and novel client proteins relevant to GSCs. The combination of onalespib with radiation and TMZ extended survival in a zebrafish and a mouse xenograft model of GBM compared with the standard of care (radiation and TMZ) or onalespib with radiation. CONCLUSIONS: The results of this study demonstrate that targeting HR by HSP90 inhibition sensitizes GSCs to radiation and chemotherapy and extends survival in zebrafish and mouse intracranial models of GBM. These results provide a preclinical rationale for assessment of HSP90 inhibitors in combination with chemoradiation in patients with GBM.

LEDGF/p75-mediated chemoresistance of mixed-lineage leukemia involves cell survival pathways and super enhancer activators.

MLL is an aggressive subtype of leukemia with a poor prognosis that mostly affects pediatric patients. MLL-rearranged fusion proteins (MLLr) induce aberrant target gene expression resulting in leukemogenesis. MLL and its fusions are tethered to chromatin by LEDGF/p75, a transcriptional co-activator that specifically recognizes H3K36me2/3. LEDGF/p75 is ubiquitously expressed and associated with regulation of gene expression, autoimmune responses, and HIV replication. LEDGF/p75 was proven to be essential for leukemogenesis in MLL. Apart from MLL, LEDGF/p75 has been linked to lung, breast, and prostate cancer. Intriguingly, LEDGF/p75 interacts with Med-1, which co-localizes with BRD4. Both are known as co-activators of super-enhancers. Here, we describe LEDGF/p75-dependent chemoresistance of MLLr cell lines. Investigation of the underlying mechanism revealed a role of LEDGF/p75 in the cell cycle and in survival pathways and showed that LEDGF/p75 protects against apoptosis during chemotherapy. Remarkably, LEDGF/p75 levels also affected expression of BRD4 and Med1. Altogether, our data suggest a role of LEDGF/p75 in cancer survival, stem cell renewal, and activation of nuclear super enhancers.

Protein acetylation in cardiac aging.

Biological aging is attributed to progressive dysfunction in systems governing genetic and metabolic integrity. At the cellular level, aging is evident by accumulated DNA damage and mutation, reactive oxygen species, alternate lipid and protein modifications, alternate gene expression programs, and mitochondrial dysfunction. These effects sum to drive altered tissue morphology and organ dysfunction. Protein-acylation has emerged as a critical mediator of age-dependent changes in these processes. Despite decades of research focus from academia and industry, heart failure remains a leading cause of death in the United States while the 5 year mortality rate for heart failure remains over 40%. Over 90% of heart failure deaths occur in patients over the age of 65 and heart failure is the leading cause of hospitalization in Medicare beneficiaries. In 1931, Cole and Koch discovered age-dependent accumulation of phosphates in skeletal muscle. These and similar findings provided supporting evidence for, now well accepted, theories linking metabolism and aging. Nearly two decades later, age-associated alterations in biochemical molecules were described in the heart. From these small beginnings, the field has grown substantially in recent years. This growing research focus on cardiac aging has, in part, been driven by advances on multiple public health fronts that allow population level clinical presentation of aging related disorders. It is estimated that by 2030, 25% of the worldwide population will be over the age of 65. This review provides an overview of acetylation-dependent regulation of biological processes related to cardiac aging and introduces emerging non-acetyl, acyl-lysine modifications in cardiac function and aging.

Unlike Its Paralog LEDGF/p75, HRP-2 Is Dispensable for MLL-R Leukemogenesis but Important for Leukemic Cell Survival.

HDGF-related protein 2 (HRP-2) is a member of the Hepatoma-Derived Growth Factor-related protein family that harbors the structured PWWP and Integrase Binding Domain, known to associate with methylated histone tails or cellular and viral proteins, respectively. Interestingly, HRP-2 is a paralog of Lens Epithelium Derived Growth Factor p75 (LEDGF/p75), which is essential for MLL-rearranged (MLL-r) leukemia but dispensable for hematopoiesis. Sequel to these findings, we investigated the role of HRP-2 in hematopoiesis and MLL-r leukemia. Protein interactions were investigated by co-immunoprecipitation and validated using recombinant proteins in NMR. A systemic knockout mouse model was used to study normal hematopoiesis and MLL-ENL transformation upon the different HRP-2 genotypes. The role of HRP-2 in MLL-r and other leukemic, human cell lines was evaluated by lentiviral-mediated miRNA targeting HRP-2. We demonstrate that MLL and HRP-2 interact through a conserved interface, although this interaction proved less dependent on menin than the MLL-LEDGF/p75 interaction. The systemic HRP-2 knockout mice only revealed an increase in neutrophils in the peripheral blood, whereas the depletion of HRP-2 in leukemic cell lines and transformed primary murine cells resulted in reduced colony formation independently of MLL-rearrangements. In contrast, primary murine HRP-2 knockout cells were efficiently transformed by the MLL-ENL fusion, indicating that HRP-2, unlike LEDGF/p75, is dispensable for the transformation of MLL-ENL leukemogenesis but important for leukemic cell survival.

Transducin ß-like protein 1 controls multiple oncogenic networks in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common Non-Hodgkin's lymphoma and is characterized by a remarkable heterogeneity with diverse variants that can be identified histologically and molecularly. Large-scale gene expression profiling studies have identified the germinal center B-cell (GCB-) and activated B-cell (ABC-) subtypes. Standard chemo-immunotherapy remains standard front line therapy, curing approximately two thirds of patients. Patients with refractory disease or those who relapse after salvage treatment have an overall poor prognosis highlighting the need for novel therapeutic strategies. Transducin ß-like protein 1 (TBL1) is an exchange adaptor protein encoded by the TBL1X gene and known to function as a master regulator of the Wnt signalling pathway by binding to ß-CATENIN and promoting its downstream transcriptional program. Here, we show that, unlike normal B-cells, DLBCL cells express abundant levels of TBL1 and its overexpression correlates with poor clinical outcome regardless of DLBCL molecular subtype. Genetic deletion of TBL1 and pharmacological approach using tegavivint, a first-in-class small molecule targeting TBL1 (Iterion Therapeutics), promotes DLBCL cell death in vitro and in vivo. Through an integrated genomic, biochemical, and pharmacologic analyses, we characterized a novel, ß-CATENIN independent, post-transcriptional oncogenic function of TBL1 in DLBCL where TBL1 modulates the stability of key oncogenic proteins such as PLK1, MYC, and the autophagy regulatory protein BECLIN-1 through its interaction with a SKP1-CUL1-F-box (SCF) protein supercomplex. Collectively, our data provide the rationale for targeting TBL1 as a novel therapeutic strategy in DLBCL.

Efficacy of Onalespib, a Long-Acting Second-Generation HSP90 Inhibitor, as a Single Agent and in Combination with Temozolomide against Malignant Gliomas.

Purpose: HSP90, a highly conserved molecular chaperone that regulates the function of several oncogenic client proteins, is altered in glioblastoma. However, HSP90 inhibitors currently in clinical trials are short-acting, have unacceptable toxicities, or are unable to cross the blood-brain barrier (BBB). We examined the efficacy of onalespib, a potent, long-acting novel HSP90 inhibitor as a single agent and in combination with temozolomide (TMZ) against gliomas in vitro and in vivoExperimental Design: The effect of onalespib on HSP90, its client proteins, and on the biology of glioma cell lines and patient-derived glioma-initiating cells (GSC) was determined. Brain and plasma pharmacokinetics of onalespib and its ability to inhibit HSP90 in vivo were assessed in non-tumor-bearing mice. Its efficacy as a single agent or in combination with TMZ was assessed in vitro and in vivo using zebrafish and patient-derived GSC xenograft mouse glioma models.Results: Onalespib-mediated HSP90 inhibition depleted several survival-promoting client proteins such as EGFR, EGFRvIII, and AKT, disrupted their downstream signaling, and decreased the proliferation, migration, angiogenesis, and survival of glioma cell lines and GSCs. Onalespib effectively crossed the BBB to inhibit HSP90 in vivo and extended survival as a single agent in zebrafish xenografts and in combination with TMZ in both zebrafish and GSC mouse xenografts.Conclusions: Our results demonstrate the long-acting effects of onalespib against gliomas in vitro and in vivo, which combined with its ability to cross the BBB support its development as a potential therapeutic agent in combination with TMZ against gliomas. Clin Cancer Res; 23(20); 6215-26. ©2017 AACR.

A phase 1 trial of the HDAC inhibitor AR-42 in patients with multiple myeloma and T- and B-cell lymphomas.

Histone deacetylase inhibitors (HDACi) have proven activity in hematologic malignancies, and their FDA approval in multiple myeloma (MM) and T-cell lymphoma highlights the need for further development of this drug class. We investigated AR-42, an oral pan-HDACi, in a first-in-man phase 1 dose escalation clinical trial. Overall, treatment was well tolerated, no DLTs were evident, and the MTD was defined as 40 mg dosed three times weekly for three weeks of a 28-day cycle. One patient each with MM and mantle cell lymphoma demonstrated disease control for 19 and 27 months (ongoing), respectively. Treatment was associated with reduction of serum CD44, a transmembrane glycoprotein associated with steroid and immunomodulatory drug resistance in MM. Our findings indicate that AR-42 is safe and that further investigation of AR-42 in combination regimens for the treatment of patients with lymphoma and MM is warranted. TRIAL REGISTRATION: http://clinicaltrials.gov/ct2/show/NCT01129193.

Histone Deacetylase Inhibitors Enhance the Therapeutic Potential of Reovirus in Multiple Myeloma.

Multiple myeloma remains incurable and the majority of patients die within 5 years of diagnosis. Reolysin, the infusible form of human reovirus (RV), is a novel viral oncolytic therapy associated with antitumor activity likely resulting from direct oncolysis and a virus-mediated antitumor immune response. Results from our phase I clinical trial investigating single agent Reolysin in patients with relapsed multiple myeloma confirmed tolerability, but no objective responses were evident, likely because the virus selectively entered the multiple myeloma cells but did not actively replicate. To date, the precise mechanisms underlying the RV infectious life cycle and its ability to induce oncolysis in patients with multiple myeloma remain unknown. Here, we report that junctional adhesion molecule 1 (JAM-1), the cellular receptor for RV, is epigenetically regulated in multiple myeloma cells. Treatment of multiple myeloma cells with clinically relevant histone deacetylase inhibitors (HDACi) results in increased JAM-1 expression as well as increased histone acetylation and RNA polymerase II recruitment to its promoter. Furthermore, our data indicate that the combination of Reolysin with HDACi, potentiates RV killing activity of multiple myeloma cells in vitro and in vivo This study provides the molecular basis to use these agents as therapeutic tools to increase the efficacy of RV therapy in multiple myeloma. Mol Cancer Ther; 15(5); 830-41. ©2016 AACR.

Proteomic characterization of circulating extracellular vesicles identifies novel serum myeloma associated markers.

Multiple myeloma (MM) is a hematological malignancy of clonal plasma cells in the bone marrow (BM). The microenvironment plays a key role in MM cell survival and drug resistance through release of soluble factors, expression of adhesion molecules and release of extracellular vesicles (EVs). The aim of this manuscript is to use proteomic profiling of EVs as a tool to identify circulating tumor associated markers in MM patients. First, we characterized the EV protein content obtained from different MM cell lines. Then, we established differences in protein abundance among EVs isolated from MM patient serum and BM and the serum of healthy donors. These data show that the Major Histocompatibility Complex Class I is highly enriched in EVs of MM cell lines and MM patient's serum. Next, we show that CD44 is highly expressed in the EVs isolated from the corticosteroid resistant MM cell line, MM.1R. Furthermore, CD44 was found to be differentially expressed in EVs isolated from newly diagnosed MM patients. Finally through ELISA analysis, we establish the potential of serum CD44 as a predictive biomarker of overall survival. These results support the analysis of EVs as an easily accessible source for MM biomarkers. BIOLOGICAL SIGNIFICANCE: Extracellular vesicles are becoming a research focus due to their roles in cancer cell biology such as immune evasion, therapeutic resistance, proliferation and metastases. While numerous studies of vesicle characterization and biology have been conducted in many cancer models, the role of EV in MM remains relatively unstudied. Here we found that EVs isolated from MM cells are enriched in MHC-1 antigen presenting complex and its binding protein ß2-MG, this observation is compatible with the enhanced proteasome activity of MM cells compared to other cancers and the ability of functional MHC-1 to bind and present peptides, generated from protein degradation by the proteasome. Additionally, our experiments show that CD44 is particularly enriched in the EV fraction of corticosteroid resistant MM.1R cells and is differentially expressed in the EV fraction of MM patients. This is of high significance due to the established role of CD44 in adhesion of MM cells to BMSC and induction of IL-6, the primary cytokine for MM cell survival, secretion by the BMSC. Furthermore, ELISA assays for CD44 content from the serum of 254 newly diagnosed MM patients enrolled in a Phase 3 randomized trial show highly variable CD44 levels and those patients with >280 ng/mL serum CD44 showing a reduced overall survival time. These results suggest the potential use of CD44 as a prognostic biomarker in MM.

The potential diagnostic power of extracellular vesicle analysis for multiple myeloma.

Multiple myeloma (MM) is a hematologic malignancy of plasma cells (PCs). In the United States, MM accounts for approximately 1% of all diagnoses and 2% of all cancer-related deaths. Although MM is a treatable disease, most patients eventually relapse, and despite the development of numerous treatment options it is still considered incurable. Mechanisms of communication between MM-PCs and bone marrow microenvironment, including cell-cell contacts and release of pro-survival factors, promote cancer cell survival and drug resistance. Recently, the importance of extracellular vesicles (EVs) as mechanisms of communication between MM cells and other cells in the microenvironment has been reported. In this review, the authors provide the update on the biology and clinical aspects of EVs in MM.

HDAC inhibitor AR-42 decreases CD44 expression and sensitizes myeloma cells to lenalidomide.

Multiple myeloma (MM) is a hematological malignancy of plasma cells in the bone marrow. Despite multiple treatment options, MM is inevitably associated with drug resistance and poor outcomes. Histone deacetylase inhibitors (HDACi's) are promising novel chemotherapeutics undergoing evaluation in clinical trials for the potential treatment of patients with MM. Although in preclinical studies HDACi's have proven anti-myeloma activity, but in the clinic single-agent HDACi treatments have been limited due to low tolerability. Improved clinical outcomes were reported only when HDACi's were combined with other drugs. Here, we show that a novel pan-HDACi AR-42 downregulates CD44, a glycoprotein that has been associated with lenalidomide and dexamethasone resistance in myeloma both in vitro and in vivo. We also show that this CD44 downregulation is in part mediated by miR-9-5p, targeting insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3), which directly binds to CD44 mRNA and increases its stability. Importantly, we also demonstrate that AR-42 enhances anti-myeloma activity of lenalidomide in primary MM cells isolated from lenalidomide resistant patients and in in vivo MM mouse model. Thus, our findings shed light on potential novel combinatorial therapeutic approaches modulating CD44 expression, which may help overcome lenalidomide resistance in myeloma patients.

Causes of failure in periprosthetic fractures of the hip at 1- to 14-year follow-up.

INTRODUCTION: The results and causes of failure for 61 patients undergoing surgery for femoral hip periprosthetic fracture are reported. MATERIALS AND METHODS: Fractures were classified according to the Vancouver System. Osteosynthesis was performed in 88% of cases and prosthetic revision in 12% of cases. Clinical and functional outcomes were assessed according to the Harris Hip Score and radiological results were evaluated using Beals and Tower's criteria. RESULTS: At a mean follow-up of 32 months, the Harris Hip Score was 73.1 and the radiological results were excellent-to-good in 72.2% of patients after the first surgery. At the end of treatment, complete healing of the fracture and stability of the prosthesis was found in 87.3% of patients. The most relevant result was the recovery of walking in 73.8% of patients. Mortality after surgery was 1.6% at 3 months and 3.3% at 12 months. A higher mortality rate occurred when surgery was delayed more than 5 days after trauma. CONCLUSIONS: The analysis of our cases shows that in Vancouver type B1 fractures treated with plating osteosynthesis, there were worse outcomes in total hip arthroplasty with cemented stems compared with uncemented stems. In Vancouver type B2 fractures with cementless straight stems, osteosynthesis with a plate can be a valid option. In Vancouver type C fractures, the stability of the stem must be carefully assessed.

Microvesicles containing miRNAs promote muscle cell death in cancer cachexia via TLR7.

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression and, in cancers, are often packaged within secreted microvesicles. The cachexia syndrome is a debilitating state of cancer that predominantly results from the loss of skeletal muscle mass, which is in part associated with apoptosis. How tumors promote apoptosis in distally located skeletal muscles has not been explored. Using both tumor cell lines and patient samples, we show that tumor-derived microvesicles induce apoptosis of skeletal muscle cells. This proapoptotic activity is mediated by a microRNA cargo, miR-21, which signals through the Toll-like 7 receptor (TLR7) on murine myoblasts to promote cell death. Furthermore, tumor microvesicles and miR-21 require c-Jun N-terminal kinase activity to regulate this apoptotic response. Together, these results describe a unique pathway by which tumor cells promote muscle loss, which might provide a great insight into elucidating the causes and treatment options of cancer cachexia.

Characterization of multiple myeloma vesicles by label-free relative quantitation.

Multiple myeloma (MM) is a hematological malignancy caused by a microenviromentally aided persistence of plasma cells in the bone marrow. The role that extracellular vesicles (EVs), microvesicles and exosomes, released by MM cells have in cell-to-cell communication and signaling in the bone marrow is currently unknown. This paper describes the proteomic content of EVs derived from MM.1S and U266 MM cell lines. First, we compared the protein identifications between the vesicles and cellular lysates of each cell line finding a large overlap in protein identifications. Next, we applied label-free spectral count quantitation to determine proteins with differential abundance between the groups. Finally, we used bioinformatics to categorize proteins with significantly different abundances into functional groups. The results illustrate the first use of label-free spectral counting applied to determine relative protein abundances in EVs.