TERT and BRAF V600E mutations in thyroid cancer of World Trade Center Responders

The 2-fold excess thyroid cancer risk reported in multiple World Trade Center (WTC) disaster exposed cohorts cannot entirely be explained by surveillance and physician bias thus highlighting the need to investigate the potential consequences of the dust exposure, containing carcinogenic and endocrine disruptive elements, on the thyroid. This study investigated the presence of TERT promoter and BRAF V600E mutations in 20 WTC-exposed versus 23 matched non-exposed thyroid cancers as potential mechanism explaining the excess risk. Although no significant difference in BRAF V600E mutation was found, TERT promoter mutations were significantly more prevalent in WTC thyroid cancer versus non-exposed thyroid cancers (P = 0.021). The odds of a TERT promoter mutation was significantly higher in the WTC versus the non-WTC thyroid cancers after adjustment [ORadj: 7.11 (95% CI: 1.21-41.83)]. These results may indicate that exposure to the mixture of pollutants present in the WTC dust resulted in an excess thyroid cancer risk and potentially more aggressive thyroid cancer, warranting investigating WTC responders on thyroid-associated symptoms during their health checkups. Future studies should include long-term follow-up to provide important insights in whether thyroid-specific survival is negatively affected by WTC dust exposure and whether this is because of the presence of one or more driver mutations.

Mebendazole Treatment Disrupts the Transcriptional Activity of Hypoxia-Inducible Factors 1 and 2 in Breast Cancer Cells

Breast cancer is the most diagnosed cancer in women in the world. Mebendazole (MBZ) has been demonstrated to have preclinical efficacy across multiple cancers, including glioblastoma multiforme, medulloblastoma, colon, breast, pancreatic, and thyroid cancers. MBZ was also well tolerated in a recent phase I clinical trial of adults diagnosed with glioma. The mechanisms of action reported so far for MBZ include tubulin disruption, inhibiting angiogenesis, promoting apoptosis, and maintaining stemness. To elucidate additional mechanisms of action for mebendazole (MBZ), we performed RNA sequencing of three different breast cancer cell lines treated with either MBZ or vehicle control. We compared the top genes downregulated upon MBZ treatment with expression profiles of cells treated with over 15,000 perturbagens using the clue.io online analysis tool. In addition to tubulin inhibitors, the gene expression profile that correlated most with MBZ treatment matched the profile of cells treated with known hypoxia-inducible factor (HIF-1α and -2α) inhibitors. The HIF pathway is the main driver of the cellular response to hypoxia, which occurs in solid tumors. Preclinical data support using HIF inhibitors in combination with standard of care to treat solid tumors. Therefore, we tested the hypothesis that MBZ could inhibit the hypoxia response. Using RNA sequencing and HIF-reporter assays, we demonstrate that MBZ inhibits the transcriptional activity of HIFs in breast cancer cell lines and in mouse models of breast cancer by preventing the induction of HIF-1α, HIF-2α, and HIF-1β protein under hypoxia. Taken together, our results suggest that MBZ treatment has additional therapeutic efficacy in the setting of hypoxia and warrants further consideration as a cancer therapy.

Mebendazole prevents distant organ metastases in part by decreasing ITGβ4 expression and cancer stemness

Breast cancer is the most diagnosed cancer among women. Approximately 15-20% of all breast cancers are highly invasive triple-negative breast cancer (TNBC) and lack estrogen, progesterone, and ERBB2 receptors. TNBC is challenging to treat due to its aggressive nature with far fewer targeted therapies than other breast cancer subtypes. Current treatments for patients with TNBC consist of cytotoxic chemotherapies, surgery, radiation, and in some instances PARP inhibitors and immunotherapy. To advance current therapeutics, we repurposed mebendazole (MBZ), an orally available FDA-approved anthelmintic that has shown preclinical efficacy for cancers. MBZ has low toxicity in humans and efficacy in multiple cancer models including breast cancer, glioblastoma multiforme, medulloblastoma, colon cancer, pancreatic and thyroid cancer. MBZ was well-tolerated in a phase I clinical trial of adults recently diagnosed with glioma. We determined that the half-maximal inhibitory concentration (IC₅₀) of MBZ in four breast cancer cell lines is well within the range reported for other types of cancer. MBZ reduced TNBC cell proliferation, induced apoptosis, and caused G2/M cell cycle arrest. MBZ reduced the size of primary tumors and prevented lung and liver metastases. In addition, we uncovered a novel mechanism of action for MBZ. We found that MBZ reduces integrin β4 (ITGβ4) expression and cancer stem cell properties. ITGβ4 has previously been implicated in promoting "cancer stemness," which may contribute to the efficacy of MBZ. Collectively, our results contribute to a growing body of evidence suggesting that MBZ should be considered as a therapeutic to slow tumor progression and prevent metastasis.

Impact of international research fellows in neurosurgery: results from a single academic center

OBJECTIVE

International research fellows have been historically involved in academic neurosurgery in the United States (US). To date, the contribution of international research fellows has been underreported. Herein, the authors aimed to quantify the academic output of international research fellows in the Department of Neurosurgery at The Johns Hopkins University School of Medicine.

METHODS

Research fellows with Doctor of Medicine (MD), Doctor of Philosophy (PhD), or MD/PhD degrees from a non-US institution who worked in the Hopkins Department of Neurosurgery for at least 6 months over the past decade (2010-2020) were included in this study. Publications produced during fellowship, number of citations, and journal impact factors (IFs) were analyzed using ANOVA. A survey was sent to collect information on personal background, demographics, and academic activities.

RESULTS

Sixty-four international research fellows were included, with 42 (65.6%) having MD degrees, 17 (26.6%) having PhD degrees, and 5 (7.8%) having MD/PhD degrees. During an average 27.9 months of fellowship, 460 publications were produced in 136 unique journals, with 8628 citations and a cumulative journal IF of 1665.73. There was no significant difference in total number of publications, first-author publications, and total citations per person among the different degree holders. Persons holding MD/PhDs had a higher number of citations per publication per person (p = 0.027), whereas those with MDs had higher total IFs per person (p = 0.048). Among the 43 (67.2%) survey responders, 34 (79.1%) had nonimmigrant visas at the start of the fellowship, 16 (37.2%) were self-paid or funded by their country of origin, and 35 (81.4%) had mentored at least one US medical student, nonmedical graduate student, or undergraduate student.

CONCLUSIONS

International research fellows at the authors' institution have contributed significantly to academic neurosurgery. Although they have faced major challenges like maintaining nonimmigrant visas, negotiating cultural/language differences, and managing self-sustainability, their scientific productivity has been substantial. Additionally, the majority of fellows have provided reciprocal mentorship to US students.

Neutrophil depletion enhanced the Clostridium novyi-NT therapy in mouse and rabbit tumor models

BACKGROUND

Hypoxia is a prominent feature of solid tumors and can function as fertile environment for oncolytic anaerobic bacteria such as Clostridium novyi-NT (C. novyi-NT) where it can induce tumor destruction in mice and patients. However, two major obstacles have limited its use, namely the host inflammatory response and the incomplete clearance of normoxic tumor areas.

METHODS

In this study, we first used a subcutaneous tumor model of a glioblastoma (GBM) cell line in immunocompetent mice to investigate the local distribution of tumor hypoxia, kinetics of C. novyi-NT germination and spread, and the local host immune response. We subsequently applied the acquired knowledge to develop a C. novyi-NT therapy in an orthotopic rabbit brain tumor model.

RESULTS

We found that local accumulation of granular leukocytes, mainly neutrophils, could impede the spread of bacteria through the tumor and prevent complete oncolysis. Depletion of neutrophils via anti-Ly6G antibody or bone marrow suppression using hydroxyurea significantly improved tumor clearance. We then applied this approach to rabbits implanted with an aggressive intracranial brain tumor and achieved long-term survival in majority of the animals without apparent toxicity.

CONCLUSION

These results indicated that depleting neutrophils can greatly enhance the safety and efficacy of C. novyi-NT cancer therapy for brain tumors.

Evaluation of a DNA demethylating agent in combination with all-trans retinoic acid for IDH1-mutant gliomas

BACKGROUND

Isocitrate Dehydrogenase 1/2 (IDH1/2) mutations are diagnostic for Astrocytoma or Oligodendroglioma, IDH-mutant. In these IDH-mutant gliomas, retinoic acid-related gene expression is commonly silenced by DNA hypermethylation. DNA demethylating agents can epigenetically reprogram IDH-mutant cells and reduce proliferation, likely by re-expression of silenced tumor suppressor pathways. We hypothesized that DNA demethylation might restore the retinoic acid pathway and slow tumor growth. This was the rationale for a preclinical evaluation combining the DNA demethylating agent, 5-Azacytidine (5-Aza), and retinoic acid pathway activation with all-trans retinoic acid (atRA) in IDH-mutant glioma.

METHODS

In this study, we evaluated the effect of 5-Aza and atRA combination on cell proliferation, apoptosis and gene expression in human glioma cells. In addition, the efficacy of combination was tested in patient-derived xenograft (PDX) bearing the IDH1R132H mutation, utilizing subcutaneous and orthotopic models.

RESULTS

5-Aza reduced the DNA methylation profile and increased the gene expression of retinoic acid-related genes. Combination of 5-Aza and atRA reduced cell growth, increased differentiation marker expression, and apoptosis in IDH1R132H glioma cells. Mechanistically, 5-Aza sensitized IDHIR132H glioma cells to atRA via upregulation of the retinoic acid pathway. Importantly, the drug combination reduced significantly the growth rate of subcutaneous tumors, but in an orthotopic mouse model the combination did not improve survival and 5-Aza alone provided the best survival benefit.

CONCLUSION

Use of DNA demethylating agent in combination with retinoids shows promise, but further optimization and preclinical studies are required for treatment of intracranial IDH-mutant gliomas.

Post-9/11 excess risk of thyroid cancer: Surveillance or exposure?

An excess risk of thyroid cancer has been reported in different World Trade Center (WTC)-dust exposed cohorts. Increased surveillance of these cohorts has been suggested as a potential explanation of this reported excess thyroid cancer risk leading to an increased diagnosis of earlier-stage thyroid cancers. However, the uncertainty to what extent surveillance or physician bias may be contributing to the reported incidence of thyroid cancer in WTC-dust exposed populations remains, highlighting the need to investigate a potential causal link between WTC dust exposure and thyroid cancer. Future studies are therefore indicated to investigate potential consequences of WTC dust exposure on the thyroid gland. Studies of the heavily exposed populations offer the possibility to better understand the mechanisms behind the exposure to a variety of environmental contaminants, and may provide useful insights into exposures harmful to the thyroid. These can be used in risk stratification when implementing screening in high-risk populations and may inform shared decision-making regarding the extent of thyroid cancer treatment.

Evaluation of a procaspase-3 activator with hydroxyurea or temozolomide against high-grade meningioma in cell culture and canine cancer patients

BACKGROUND

High-grade meningioma is an aggressive type of brain cancer that is often recalcitrant to surgery and radiotherapy, leading to poor overall survival. Currently, there are no FDA-approved drugs for meningioma, highlighting the need for new therapeutic options, but development is challenging due to the lack of predictive preclinical models.

METHODS

To leverage the known overexpression of procaspase-3 in meningioma, PAC-1, a blood-brain barrier penetrant procaspase-3 activator, was evaluated for its ability to induce apoptosis in meningioma cells. To enhance the effects of PAC-1, combinations with either hydroxyurea or temozolomide were explored in cell culture. Both combinations were further investigated in small groups of canine meningioma patients and assessed by MRI, and the novel apoptosis tracer, [18F]C-SNAT4, was evaluated in patients treated with PAC-1 + HU.

RESULTS

In meningioma cell lines in culture, PAC-1 + HU are synergistic while PAC-1 + TMZ show additive-to-synergistic effects. In canine meningioma patients, PAC-1 + HU led to stabilization of disease and no change in apoptosis within the tumor, whereas PAC-1 + TMZ reduced tumor burden in all three canine patients treated.

CONCLUSIONS

Our results suggest PAC-1 + TMZ as a potentially efficacious combination for the treatment of human meningioma, and also demonstrate the utility of including pet dogs with meningioma as a means to assess anticancer strategies for this common brain tumor.

Mebendazole and temozolomide in patients with newly diagnosed high-grade gliomas: results of a phase 1 clinical trial

Background

Mebendazole is an anthelmintic drug introduced for human use in 1971 that extends survival in preclinical models of glioblastoma and other brain cancers.

Methods

A single-center dose-escalation and safety study of mebendazole in 24 patients with newly diagnosed high-grade gliomas in combination with temozolomide was conducted. Patients received mebendazole in combination with adjuvant temozolomide after completing concurrent radiation plus temozolomide. Dose-escalation levels were 25, 50, 100, and 200 mg/kg/day of oral mebendazole. A total of 15 patients were enrolled at the highest dose studied of 200 mg/kg/day. Trough plasma levels of mebendazole were measured at 4, 8, and 16 weeks.

Results

Twenty-four patients (18 glioblastoma and 6 anaplastic glioma) were enrolled with a median age of 49.8 years. Four patients (at 200 mg/kg) developed elevated grade 3 alanine aminotransferase (ALT) and/or aspartate transaminase (AST) after 1 month, which reversed with lower dosing or discontinuation. Plasma levels of mebendazole were variable but generally increased with dose. Kaplan–Meier analysis showed a 21-month median overall survival with 41.7% of patients alive at 2 years and 25% at 3 and 4 years. Median progression-free survival (PFS) from the date of diagnosis for 17 patients taking more than 1 month of mebendazole was 13.1 months (95% confidence interval [CI]: 8.8–14.6 months) but for 7 patients who received less than 1 month of mebendazole PFS was 9.2 months (95% CI: 5.8–13.0 months).

Conclusion

Mebendazole at doses up to 200 mg/kg demonstrated long-term safety and acceptable toxicity. Further studies are needed to determine mebendazole’s efficacy in patients with malignant glioma.

The glutamine antagonist prodrug JHU-083 slows malignant glioma growth and disrupts mTOR signaling

Background

Metabolic reprogramming is a common feature in cancer, and it is critical to facilitate cancer cell growth. Isocitrate Dehydrogenase 1/2 (IDH1 and IDH2) mutations (IDHmut) are the most common genetic alteration in glioma grade II and III and secondary glioblastoma and these mutations increase reliance on glutamine metabolism, suggesting a potential vulnerability. In this study, we tested the hypothesis that the brain penetrant glutamine antagonist prodrug JHU-083 reduces glioma cell growth.

Material and Methods

We performed cell growth, cell cycle, and protein expression in glutamine deprived or Glutaminase (GLS) gene silenced glioma cells. We tested the effect of JHU-083 on cell proliferation, metabolism, and mTOR signaling in cancer cell lines. An orthotopic IDH1R132H glioma model was used to test the efficacy of JHU-083 in vivo.

Results

Glutamine deprivation and GLS gene silencing reduced glioma cell proliferation in vitro in glioma cells. JHU-083 reduced glioma cell growth in vitro, modulated cell metabolism, and disrupted mTOR signaling and downregulated Cyclin D1 protein expression, through a mechanism independent of TSC2 modulation and glutaminolysis. IDH1R132H isogenic cells preferentially reduced cell growth and mTOR signaling downregulation. In addition, guanine supplementation partially rescued IDHmut glioma cell growth, mTOR signaling, and Cyclin D1 protein expression in vitro. Finally, JHU-083 extended survival in an intracranial IDH1 mut glioma model and reduced intracranial pS6 protein expression.

Conclusion

Targeting glutamine metabolism with JHU-083 showed efficacy in preclinical models of IDHmut glioma and measurably decreased mTOR signaling.

Demethylation and epigenetic modification with 5-azacytidine reduces IDH1 mutant glioma growth in combination with temozolomide

BACKGROUND

Isocitrate deyhydrogenase (IDH) mutant glioma comprises the majority of grades II-III gliomas and nearly all secondary glioblastomas. These progressive gliomas arise from mutations in IDH1 or IDH2 that pathologically produce D-2-hydroxyglutarate (2HG), which interferes with cell reactions using alpha ketoglutarate, leading to a hypermethylated genome and epigenetic dysregulation of gene expression initiating tumorigenesis.

METHODS

Human IDH1 wild type (wt) and IDH1 R132H cell lines and patient-derived xenografts (PDXs) were used to evaluate the FDA-approved DNA demethylating agent 5-azacytidine (5-aza). Cell growth, protein and gene expression, chromatin immunoprecipitation, and nucleosome position assays were performed in 5-aza treated cells. To evaluate antitumor activity in vivo, 5-aza was administered alone and in combination with temozolomide (TMZ) in a PDX glioma model harboring IDH1 R132H mutation.

RESULTS

5-Aza treatment has been found to reduce cell growth and increase expression of glial fibrillary acid protein (GFAP). Chromatin immunoprecipitation and nucleosome position assay showed that the mechanism of increased GFAP expression induction is associated with histone modification and nucleosome repositioning of the GFAP promoter, respectively. In vivo, 5-aza treatment extended survival in IDH1 R132H mutant but not in an IDH1 wt glioma model. Additionally, 5-aza enhances the therapeutic effect of the DNA damaging agent TMZ in both subcutaneous and orthotopic PDX models of IDH1 R132H mutant glioma.

CONCLUSION

5-Aza provided a survival benefit as a single agent but worked best in combination with TMZ in 2 different IDH1 R132H mutant glioma models.

Mebendazole inhibits tumor growth and prevents lung metastasis in models of advanced thyroid cancer

The most common thyroid malignancy is papillary thyroid cancer. While a majority respond to therapy and have a favorable prognosis, some papillary thyroid cancers persist. This subset may dedifferentiate to anaplastic thyroid cancer, an aggressive, highly invasive and rapidly fatal cancer. Thyroid cancer patients at risk for disease progression and metastasis need earlier, safer and more effective therapies. The purpose of this translational study was to determine if mebendazole could be repurposed to effectively treat thyroid cancer, in particular before metastasis. In vitro, mebendazole potently inhibited the growth of a panel of human papillary and anaplastic thyroid cancer cells. In papillary (B-CPAP) and anaplastic (8505c) cell lines, mebendazole increased the percentage of cells in G2/M cell cycle arrest and induced late stage apoptosis by activation of the caspase-3 pathway. In aggressive 8505c cells, mebendazole significantly repressed migratory and invasive potential in a wound healing and transwell invasion assay and inhibited expression of phosphorylated Akt and Stat3 and reduced Gli1. In vivo, mebendazole treatment resulted in significant orthotopic thyroid tumor regression (B-CPAP) and growth arrest (8505c), with treated tumors displaying reduced expression of the proliferation maker KI67 and less vascular epithelium as indicated by CD31+ immunohistochemistry. Most importantly, daily oral mebendazole prevented established thyroid tumors from metastasizing to the lung. Given the low toxicity and published anticancer mechanisms of mebendazole, this novel preclinical study of mebendazole in thyroid cancer has promising therapeutic implications for patients with treatment refractory papillary or anaplastic thyroid cancer.

A role for caveola-forming proteins caveolin-1 and CAVIN1 in the pro-invasive response of glioblastoma to osmotic and hydrostatic pressure

In solid tumours, elevated interstitial fluid pressure (osmotic and hydrostatic pressure) is a barrier to drug delivery and correlates with poor prognosis. Glioblastoma (GBM) further experience compressive force when growing within a space limited by the skull. Caveolae are proposed to play mechanosensing roles, and caveola‐forming proteins are overexpressed in GBM. We asked whether caveolae mediate the GBM response to osmotic pressure. We evaluated in vitro the influence of spontaneous or experimental down‐regulation of caveola‐forming proteins (caveolin‐1, CAVIN1) on the proteolytic profile and invasiveness of GBM cells in response to osmotic pressure. In response to osmotic pressure, GBM cell lines expressing caveola‐forming proteins up‐regulated plasminogen activator (uPA) and/or matrix metalloproteinases (MMPs), some EMT markers and increased their in vitro invasion potential. Down‐regulation of caveola‐forming proteins impaired this response and prevented hyperosmolarity‐induced mRNA expression of the water channel aquaporin 1. CRISPR ablation of caveola‐forming proteins further lowered expression of matrix proteases and EMT markers in response to hydrostatic pressure, as a model of mechanical force. GBM respond to pressure by increasing matrix‐degrading enzyme production, mesenchymal phenotype and invasion. Caveola‐forming proteins mediate, at least in part, the pro‐invasive response of GBM to pressure. This may represent a novel target in GBM treatment.

Feasibility of using NF1-GRD and AAV for gene replacement therapy in NF1-associated tumors

Neurofibromatosis type 1, including the highly aggressive malignant peripheral nerve sheath tumors (MPNSTs), is featured by the loss of functional neurofibromin 1 (NF1) protein resulting from genetic alterations. A major function of NF1 is suppressing Ras activities, which is conveyed by an intrinsic GTPase-activating protein-related domain (GRD). In this study, we explored the feasibility of restoring Ras GTPase via exogenous expression of various GRD constructs, via gene delivery using a panel of adeno-associated virus (AAV) vectors in MPNST and human Schwann cells (HSCs). We demonstrated that several AAV serotypes achieved favorable transduction efficacies in those cells and a membrane-targeting GRD fused with an H-Ras C-terminal motif (C10) dramatically inhibited the Ras pathway and MPNST cells in a NF1-specific manner. Our results opened up a venue of gene replacement therapy in NF1-related tumors.

Molecular Study of Thyroid Cancer in World Trade Center Responders

Thyroid cancer incidence is higher in World Trade Center (WTC) responders compared with the general population. It is unclear whether this excess in thyroid cancer is associated with WTC-related exposures or if instead there is an over-diagnosis of malignant thyroid cancer among WTC first responders due to enhanced surveillance and physician bias. To maximize diagnostic yield and determine the false positive rate for malignancy, the histological diagnoses of thyroid cancer tumors from WTC responders and age, gender, and histology matched non-WTC thyroid cancer cases were evaluated using biomarkers of malignancy. Using a highly accurate panel of four biomarkers that are able to distinguish benign from malignant thyroid cancer, our results suggest that over-diagnosis by virtue of misdiagnosis of a benign tumor as malignant does not explain the increased incidence of thyroid cancer observed in WTC responders. Therefore, rather than over-diagnosis due to physician bias, the yearly screening visits by the World Trade Center Health Program are identifying true cases of thyroid cancer. Continuing regular screening of this cohort is thus warranted.

Correlation of the invasive potential of glioblastoma and expression of caveola-forming proteins caveolin-1 and CAVIN1

INTRODUCTION

Glioblastoma (GBM) is the most common primary brain cancer. The average survival time for the majority of patients is approximately 15 months after diagnosis. A major feature of GBM that contributes to its poor prognosis is its high invasiveness. Caveolae are plasma membrane subdomains that participate in numerous biological functions. Caveolin-1 and Caveolae Associated Protein 1 (CAVIN1), formerly termed Polymerase I and Transcript Release Factor, are both necessary for caveola formation. We hypothesized that high expression of caveola-forming proteins in GBM promotes invasiveness via modulation of the production of matrix-degrading enzymes.

METHODS

The mRNA expression of caveola-forming proteins and matrix proteases in GBM samples, and survival after stratifying patients according to caveolin-1 or CAVIN1 expression, were analyzed from TCGA and REMBRANDT databases. The proteolytic profile of cell lines expressing or devoid of caveola-forming proteins was investigated using zymography and real-time qPCR. Invasion through basement membrane-like protein was investigated in vitro.

RESULTS

Expression of both caveolin-1 and CAVIN1 was increased in GBM compared to normal samples and correlated with expression of urokinase plasminogen activator (uPA) and gelatinases. High expression of caveola-forming proteins was associated with shorter survival time. GBM cell lines capable of forming caveolae expressed more uPA and matrix metalloproteinase-2 (MMP-2) and/or -9 (MMP-9) and were more invasive than GBM cells devoid of caveola-forming proteins. Experimental manipulation of caveolin-1 or CAVIN1 expression in GBM cells recapitulated some, but not all of these features. Caveolae modulate GBM cell invasion in part via matrix protease expression.

G-quadruplex DNA drives genomic instability and represents a targetable molecular abnormality in ATRX-deficient malignant glioma

Mutational inactivation of ATRX (α-thalassemia mental retardation X-linked) represents a defining molecular alteration in large subsets of malignant glioma. Yet the pathogenic consequences of ATRX deficiency remain unclear, as do tractable mechanisms for its therapeutic targeting. Here we report that ATRX loss in isogenic glioma model systems induces replication stress and DNA damage by way of G-quadruplex (G4) DNA secondary structure. Moreover, these effects are associated with the acquisition of disease-relevant copy number alterations over time. We then demonstrate, both in vitro and in vivo, that ATRX deficiency selectively enhances DNA damage and cell death following chemical G4 stabilization. Finally, we show that G4 stabilization synergizes with other DNA-damaging therapies, including ionizing radiation, in the ATRX-deficient context. Our findings reveal novel pathogenic mechanisms driven by ATRX deficiency in glioma, while also pointing to tangible strategies for drug development.

ATRX deficiency is linked to genomic stability in cancer cells. Here, the authors show that ATRX inactivation induces G-quadruplex formation, leading to genome-wide DNA damage, and the use of G-quadruplex stabilisers can be exploited therapeutically in ATRX deficient gliomas.

Tunable Stability of Imidazotetrazines Leads to a Potent Compound for Glioblastoma

Even in the era of personalized medicine and immunotherapy, temozolomide (TMZ), a small molecule DNA alkylating agent, remains the standard-of-care for glioblastoma (GBM). TMZ has an unusual mode-of-action, spontaneously converting to its active component via hydrolysis in vivo. While TMZ has been FDA approved for two decades, it provides little benefit to patients whose tumors express the resistance enzyme MGMT and gives rise to systemic toxicity through myelosuppression. TMZ was first synthesized in 1984, but certain key derivatives have been inaccessible due to the chemical sensitivity of TMZ, precluding broad exploration of the link between imidazotetrazine structure and biological activity. Here, we sought to discern the relationship between the hydrolytic stability and anticancer activity of imidazotetrazines, with the objectives of identifying optimal timing for prodrug activation and developing suitable compounds with enhanced efficacy via increased blood-brain barrier penetrance. This work necessitated the development of new synthetic methods to provide access to previously unexplored functionality (such as aliphatic, ketone, halogen, and aryl groups) at the C8 position of imidazotetrazines. Through synthesis and evaluation of a suite of compounds with a range of aqueous stabilities (from 0.5 to 40 h), we derive a predictive model for imidazotetrazine hydrolytic stability based on the Hammett constant of the C8 substituent. Promising compounds were identified that possess activity against a panel of GBM cell lines, appropriate hydrolytic and metabolic stability, and brain-to-serum ratios dramatically elevated relative to TMZ, leading to lower hematological toxicity profiles and superior activity to TMZ in a mouse model of GBM. This work points a clear path forward for the development of novel and effective anticancer imidazotetrazines.

Mutation Profiles in Glioblastoma 3D Oncospheres Modulate Drug Efficacy

Glioblastoma (GBM) is a lethal brain cancer with a median survival time of approximately 15 months following treatment. Common in vitro GBM models for drug screening are adherent and do not recapitulate the features of human GBM in vivo. Here we report the genomic characterization of nine patient-derived, spheroid GBM cell lines that recapitulate human GBM characteristics in orthotopic xenograft models. Genomic sequencing revealed that the spheroid lines contain alterations in GBM driver genes such as PTEN, CDKN2A, and NF1. Two spheroid cell lines, JHH-136 and JHH-520, were utilized in a high-throughput drug screen for cell viability using a 1912-member compound library. Drug mechanisms that were cytotoxic in both cell lines were Hsp90 and proteasome inhibitors. JHH-136 was uniquely sensitive to topoisomerase 1 inhibitors, while JHH-520 was uniquely sensitive to Mek inhibitors. Drug combination screening revealed that PI3 kinase inhibitors combined with Mek or proteasome inhibitors were synergistic. However, animal studies to test these drug combinations in vivo revealed that Mek inhibition alone was superior to the combination treatments. These data show that these GBM spheroid lines are amenable to high-throughput drug screening and that this dataset may deliver promising therapeutic leads for future GBM preclinical studies.

N-Substituted Prodrugs of Mebendazole Provide Improved Aqueous Solubility and Oral Bioavailability in Mice and Dogs

Mebendazole (MBZ) was developed as a broad-spectrum anthelmintic but has recently shown efficacy as an anticancer agent. The use of MBZ for cancer, however, is challenging due to its poor solubility leading to poor bioavailability. Herein, we developed a prodrug approach with various N-linked promoieties including acyloxymethyl, aminoacyloxymethyl, and substituted phosphonooxymethyl in attempt to improve these characteristics. Compound 12, containing an (((((isopropoxycarbonyl)oxy)methoxy)phosphoryl)oxy)methyl promoiety, showed a >10 000-fold improvement in aqueous solubility. When evaluated in mice, 12 displayed a 2.2-fold higher plasma AUC_{0- t} and a 1.7-fold improvement in brain AUC_{0- t} with a calculated oral bioavailability of 52%, as compared to 24% for MBZ-polymorph C (MBZ-C), the most bioavailable polymorph. In dogs, 12 showed a 3.8-fold higher plasma AUC_{0- t} with oral bioavailability of 41% compared to 11% for MBZ-C. In summary, we have identified a prodrug of MBZ with better physicochemical properties and enhanced bioavailability in both mice and dog.

Mebendazole and a non-steroidal anti-inflammatory combine to reduce tumor initiation in a colon cancer preclinical model

Inheritance of a gene mutation leads to the initiation of 5 to 10% of most cancers, including colon cancer cases. We developed a chemoprevention strategy using a novel combination of the non-steroidal anti-inflammatory (NSAID) sulindac plus the anthelminthic benzimidazole, mebendazole. This oral drug combination was effective in the Apc^Min/+ mouse model of Familial Adenomatous Polyposis (FAP). Treatment with 35 mg/kg daily mebendazole reduced the number of intestinal adenomas by 56% (P = 0.0002), 160 ppm sulindac by 74% (P < 0.0001), and the combination by 90% (P < 0.0001). The combination significantly reduced microadenomas, polyp number and size in both the small intestines and colon when compared to untreated controls or sulindac alone. Mebendazole as a single agent decreased COX2 expression, blood vessel formation, VEGFR2 phosphorylation, and worked synergistically with sulindac to reduce overexpression of MYC, BCL2, and various pro-inflammatory cytokines. Given the low toxicity of mebendazole, these preclinical findings support the consideration of clinical trials for high risk cancer patients using mebendazole either alone or in combination. The findings have implications for populations with moderate and above risk for developing cancer.

Synergistic and targeted therapy with a procaspase-3 activator and temozolomide extends survival in glioma rodent models and is feasible for the treatment of canine malignant glioma patients

Purpose

Glioblastoma is a deadly brain cancer with a median survival time of ∼15 months. Ionizing radiation plus the DNA alkylator temozolomide (TMZ) is the current standard therapy. PAC-1, a procaspase-3 activating small molecule, is blood-brain barrier penetrant and has previously demonstrated ability to synergize with diverse pro-apoptotic chemotherapeutics. We studied if PAC-1 could enhance the activity of TMZ, and whether addition of PAC-1 to standard treatment would be feasible in spontaneous canine malignant gliomas.

Experimental Design

Using cell lines and online gene expression data, we identified procaspase-3 as a potential molecular target for most glioblastomas. We investigated PAC-1 as a single agent and in combination with TMZ against glioma cells in culture and in orthotopic rodent models of glioma. Three dogs with spontaneous gliomas were treated with an analogous human glioblastoma treatment protocol, with concurrent PAC-1.

Results

Procaspase-3 is expressed in gliomas, with higher gene expression correlating with increased tumor grade and decreased prognosis. PAC-1 is cytotoxic to glioma cells in culture and active in orthotopic rodent glioma models. PAC-1 added to TMZ treatments in cell culture increases apoptotic death, and the combination significantly increases survival in orthotopic glioma models. Addition of PAC-1 to TMZ and radiation was well-tolerated in 3 out of 3 pet dogs with spontaneous glioma, and partial to complete tumor reductions were observed.

Conclusions

Procaspase-3 is a clinically relevant target for treatment of glioblastoma. Synergistic activity of PAC-1/TMZ in rodent models and the demonstration of feasibility of the combined regime in canine patients suggest potential for PAC-1 in the treatment of glioblastoma.

Somatic retrotransposition is infrequent in glioblastomas

Background

Gliomas are the most common primary brain tumors in adults. We sought to understand the roles of endogenous transposable elements in these malignancies by identifying evidence of somatic retrotransposition in glioblastomas (GBM). We performed transposon insertion profiling of the active subfamily of Long INterspersed Element-1 (LINE-1) elements by deep sequencing (TIPseq) on genomic DNA of low passage oncosphere cell lines derived from 7 primary GBM biopsies, 3 secondary GBM tissue samples, and matched normal intravenous blood samples from the same individuals.

Results

We found and PCR validated one somatically acquired tumor-specific insertion in a case of secondary GBM. No LINE-1 insertions present in primary GBM oncosphere cultures were missing from corresponding blood samples. However, several copies of the element (11) were found in genomic DNA from blood and not in the oncosphere cultures. SNP 6.0 microarray analysis revealed deletions or loss of heterozygosity in the tumor genomes over the intervals corresponding to these LINE-1 insertions.

Conclusions

These findings indicate that LINE-1 retrotransposon can act as an infrequent insertional mutagen in secondary GBM, but that retrotransposition is uncommon in these central nervous system tumors as compared to other neoplasias.

Electronic supplementary material

The online version of this article (doi:10.1186/s13100-016-0077-5) contains supplementary material, which is available to authorized users.

Suppression of trophoblast cell surface antigen 2 enhances proliferation and migration in liver fluke-associated cholangiocarcinoma

BACKGROUND AND AIM

Trophoblast cell surface antigen 2 (TROP2) or tumor-associated calcium signal transducer 2 (TACSTD2) is a 36-kDa type I transmembrane glycoprotein and exerts dual functions as an oncogene and tumor suppressor in cancer cells. In this study, we investigated the expression and functions of TROP2 in liver fluke-associated cholangiocarcinoma (CCA).

MATERIAL AND METHODS

TROP2 expression in 85 CCA tissues was detected by using immunohistochemistry. The methylation status of TROP2 promoter was studied in 15 matched pairs of normal and CCA formalin fixed paraffin embedded (FFPE) tissues using the bisulfite genomic sequencing (BGS) method. The functions of TROP2 on cancer cell behavior were investigated using siRNA in CCA cell lines. Proliferation, migration and invasion assays were performed. A PCR array was used to evaluate the impact of TROP2 knockdown on the gene expression profiles.

RESULTS

TROP2 was highly expressed in all normal bile duct epithelia, but significantly down-regulated in CCA cells. Sixty percent of CCA revealed promoter hypermethylation compared to the corresponding adjacent normal tissues. TROP2 knockdown significantly enhanced the proliferation and migration in CCA cell lines, and altered the expressions of MARCK, EMP1 and FILIP1L.

CONCLUSION

We provide new evidence that TROP2 is epigenetically down-regulated and operates as a negative regulator of cell proliferation and migration in liver fluke-associated CCA.

A High-Throughput Screen Identifies 2,9-Diazaspiro[5.5]Undecanes as Inducers of the Endoplasmic Reticulum Stress Response with Cytotoxic Activity in 3D Glioma Cell Models

The endoplasmic reticulum (ER) is involved in Ca²⁺ signaling and protein folding. ER Ca²⁺ depletion and accumulation of unfolded proteins activate the molecular chaperone GRP78 (glucose-regulated protein 78) which in turn triggers the ER stress response (ERSR) pathway aimed to restore ER homeostasis. Failure to adapt to stress, however, results in apoptosis. We and others have shown that malignant cells are more susceptible to ERSR-induced apoptosis than their normal counterparts, implicating the ERSR as a potential target for cancer therapeutics. Predicated on these findings, we developed an assay that uses a GRP78 biosensor to identify small molecule activators of ERSR in glioma cells. We performed a quantitative high-throughput screen (qHTS) against a collection of ~425,000 compounds and a comprehensive panel of orthogonal secondary assays was formulated for stringent compound validation. We identified novel activators of ERSR, including a compound with a 2,9-diazaspiro[5.5]undecane core, which depletes intracellular Ca²⁺ stores and induces apoptosis-mediated cell death in several cancer cell lines, including patient-derived and 3D cultures of glioma cells. This study demonstrates that our screening platform enables the identification and profiling of ERSR inducers with cytotoxic activity and advocates for characterization of these compound in in vivo models.

Establishment and Biological Characterization of a Panel of Glioblastoma Multiforme (GBM) and GBM Variant Oncosphere Cell Lines

Objective

Human tumor cell lines form the basis of the majority of present day laboratory cancer research. These models are vital to studying the molecular biology of tumors and preclinical testing of new therapies. When compared to traditional adherent cell lines, suspension cell lines recapitulate the genetic profiles and histologic features of glioblastoma multiforme (GBM) with higher fidelity. Using a modified neural stem cell culture technique, here we report the characterization of GBM cell lines including GBM variants.

Methods

Tumor tissue samples were obtained intra-operatively and cultured in neural stem cell conditions containing growth factors. Tumor lines were characterized in vitro using differentiation assays followed by immunostaining for lineage-specific markers. In vivo tumor formation was assayed by orthotopic injection in nude mice. Genetic uniqueness was confirmed via short tandem repeat (STR) DNA profiling.

Results

Thirteen oncosphere lines derived from GBM and GBM variants, including a GBM with PNET features and a GBM with oligodendroglioma component, were established. All unique lines showed distinct genetic profiles by STR profiling. The lines assayed demonstrated a range of in vitro growth rates. Multipotency was confirmed using in vitro differentiation. Tumor formation demonstrated histologic features consistent with high grade gliomas, including invasion, necrosis, abnormal vascularization, and high mitotic rate. Xenografts derived from the GBM variants maintained histopathological features of the primary tumors.

Conclusions

We have generated and characterized GBM suspension lines derived from patients with GBMs and GBM variants. These oncosphere cell lines will expand the resources available for preclinical study.

Clostridium novyi-NT can cause regression of orthotopically implanted glioblastomas in rats

Glioblastoma (GBM) is a highly aggressive primary brain tumor that is especially difficult to treat. The tumor's ability to withstand hypoxia leads to enhanced cancer cell survival and therapy resistance, but also yields a microenvironment that is in many aspects unique within the human body, thus offering potential therapeutic opportunities. The spore-forming anaerobic bacterium Clostridium novyi-NT(C. novyi-NT) has the ability to propagate in tumor-generated hypoxia, leading to oncolysis. Here, we show that intravenously injected spores of C. novyi-NT led to dramatic tumor destructions and significant survival increases in implanted, intracranial syngeneic F98 and human xenograft 060919 rat GBM models. C. novyi-NT germination was specific and confined to the neoplasm, with sparing of the normal brain parenchyma. All animals tolerated the bacteriolytic treatment, but edema and increased intracranial pressure could quickly be lethal if not monitored and medically managed with hydration and antibiotics. These results provide pre-clinical data supporting the development of this therapeutic approach for the treatment of patients with GBM.

The anthelmintic drug mebendazole inhibits growth, migration and invasion in gastric cancer cell model

The present study aimed to investigate the effects of MBZ on a human malignant ascites cell line derived from a primary gastric cancer tumor. Our data reveal that MBZ showed high cytotoxicity in vitro, displaying an IC50 of 0.39 μM and 1.25 μM in ACP-02 and ACP-03, respectively. The association between MBZ and 5-FU increased slightly the cytotoxicity when compared to MBZ and 5-FU alone. Furthermore, MBZ disrupted the microtubule structure of AGP-01 cells and inhibited significantly the invasion and migration of these cells. Activity of active MMP-2 significantly decreased at all tested concentration of MBZ compared to negative control. These results support the indication of MBZ in combination with chemotherapeutic agents as a possible adjuvant therapy for the management/treatment of patients with advanced gastric cancer since MBZ is a drug of low cost with acceptable safety profile and reduced toxicity to normal cells. However, clinical trials must be performed in o to evaluate its efficacy in gastric cancer patients.

Abstract 3620: An oral procaspase activating drug, PAC-1, shows preclinical promise for glioblastoma therapy

PAC-1 is an oral administered procaspase-3 activating drug developed to overcome the malignant cell's barrier to apoptosis. The promising preclinical safety and efficacy of PAC-1 has led to its consideration for a first in human phase 1 clinical trial for recurrent and advanced malignancies. We have found that because PAC-1 is able to reach intracranial brain tumors in effective concentrations, that it is particularly useful for glioblastoma (GBM), an aggressive and invasive malignancy responsible for the most deaths due to brain cancer. In glioblastoma patients a worse prognosis was correlated with high expression of procaspase-3 mRNA, indicating that procaspase-3 activation may be involved in the pathology of the tumor progression. In preclinical testing of PAC-1, it showed significant survival benefit and low systemic toxicity, in orthotopic animal models of glioblastoma. An aqueous suspension of PAC-1 delivered orally to rats with intracranial 9L glioblastoma improved survival compared to untreated controls. Additionally, when PAC-1 was administered as an oral capsule to rats with 9L glioblastoma, median survival increased over three fold. Oral PAC-1 improved survival significantly also in a human xenograft model (p = 0.04) compared to controls. PAC-1 combined effectively with standard of care, and in some animals, either alone or in combination resulted in long term survival. PAC-1 has the ability to penetrate sufficiently within intracranial tumors and its ability to overcome resistance to apoptosis and activate widespread cell death specifically in the malignant cells makes it a promising small molecule for further preclinical and clinical development.

Citation Format: Avadhut D. Joshi, Rachel C. Botham, Howard S. Roth, Timothy M. Fan, Theodore M. Tarasow, Paul J. Hergenrother, Gregory J. Riggins. An oral procaspase activating drug, PAC-1, shows preclinical promise for glioblastoma therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3620. doi:10.1158/1538-7445.AM2015-3620

Intratumoral injection of Clostridium novyi-NT spores induces antitumor responses

Species of Clostridium bacteria are notable for their ability to lyse tumor cells growing in hypoxic environments. We show that an attenuated strain of Clostridium novyi (C. novyi-NT) induces a microscopically precise, tumor-localized response in a rat orthotopic brain tumor model after intratumoral injection. It is well known, however, that experimental models often do not reliably predict the responses of human patients to therapeutic agents. We therefore used naturally occurring canine tumors as a translational bridge to human trials. Canine tumors are more like those of humans because they occur in animals with heterogeneous genetic backgrounds, are of host origin, and are due to spontaneous rather than engineered mutations. We found that intratumoral injection of C. novyi-NT spores was well tolerated in companion dogs bearing spontaneous solid tumors, with the most common toxicities being the expected symptoms associated with bacterial infections. Objective responses were observed in 6 of 16 dogs (37.5%), with three complete and three partial responses. On the basis of these encouraging results, we treated a human patient who had an advanced leiomyosarcoma with an intratumoral injection of C. novyi-NT spores. This treatment reduced the tumor within and surrounding the bone. Together, these results show that C. novyi-NT can precisely eradicate neoplastic tissues and suggest that further clinical trials of this agent in selected patients are warranted.

Brain Penetration and Efficacy of Different Mebendazole Polymorphs in a Mouse Brain Tumor Model

PURPOSE

Mebendazole (MBZ), first used as an antiparasitic drug, shows preclinical efficacy in models of glioblastoma and medulloblastoma. Three different mebendazole polymorphs (A, B, and C) exist, and a detailed assessment of the brain penetration, pharmacokinetics, and antitumor properties of each individual mebendazole polymorph is necessary to improve mebendazole-based brain cancer therapy.

EXPERIMENTAL DESIGN AND RESULTS

In this study, various marketed and custom-formulated mebendazole tablets were analyzed for their polymorph content by IR spectroscopy and subsequently tested in an orthotopic GL261 mouse glioma model for efficacy and tolerability. The pharmacokinetics and brain concentration of mebendazole polymorphs and two main metabolites were analyzed by LC/MS. We found that polymorph B and C both increased survival in a GL261 glioma model, as B exhibited greater toxicity. Polymorph A showed no benefit. Polymorph B and C both reached concentrations in the brain that exceeded the IC₅₀ in GL261 cells 29-fold. In addition, polymorph C demonstrated an AUC₀₋₂₄h brain-to-plasma (B/P) ratio of 0.82, whereas B showed higher plasma AUC and lower B/P ratio. In contrast, polymorph A presented markedly lower levels in the plasma and brain. Furthermore, the combination with elacridar was able to significantly improve the efficacy of polymorph C in GL261 glioma and D425 medulloblastoma models in mice.

CONCLUSIONS

Among mebendazole polymorphs, C reaches therapeutically effective concentrations in the brain tissue and tumor with fewer side effects, and is the better choice for brain cancer therapy. Its efficacy can be further enhanced by combination with elacridar.

Antihelminthic benzimidazoles are novel HIF activators that prevent oxidative neuronal death via binding to tubulin

AIMS

Pharmacological activation of the adaptive response to hypoxia is a therapeutic strategy of growing interest for neurological conditions, including stroke, Huntington's disease, and Parkinson's disease. We screened a drug library with known safety in humans using a hippocampal neuroblast line expressing a reporter of hypoxia-inducible factor (HIF)-dependent transcription.

RESULTS

Our screen identified more than 40 compounds with the ability to induce hypoxia response element-driven luciferase activity as well or better than deferoxamine, a canonical activator of hypoxic adaptation. Among the chemical entities identified, the antihelminthic benzimidazoles represented one pharmacophore that appeared multiple times in our screen. Secondary assays confirmed that antihelminthics stabilized the transcriptional activator HIF-1α and induced expression of a known HIF target gene, p21(cip1/waf1), in post-mitotic cortical neurons. The on-target effect of these agents in stimulating hypoxic signaling was binding to free tubulin. Moreover, antihelminthic benzimidazoles also abrogated oxidative stress-induced death in vitro, and this on-target effect also involves binding to free tubulin.

INNOVATION AND CONCLUSIONS

These studies demonstrate that tubulin-binding drugs can activate a component of the hypoxic adaptive response, specifically the stabilization of HIF-1α and its downstream targets. Tubulin-binding drugs, including antihelminthic benzimidazoles, also abrogate oxidative neuronal death in primary neurons. Given their safety in humans and known ability to penetrate into the central nervous system, antihelminthic benzimidazoles may be considered viable candidates for treating diseases associated with oxidative neuronal death, including stroke.

A model of a patient-derived IDH1 mutant anaplastic astrocytoma with alternative lengthening of telomeres

Mutations in isocitrate dehydrogenase 1 (IDH1) have been found in the vast majority of low grade and progressive infiltrating gliomas and are characterized by the production of 2-hydroxyglutarate from α-ketoglutarate. Recent investigations of malignant gliomas have identified additional genetic and chromosomal abnormalities which cluster with IDH1 mutations into two distinct subgroups. The astrocytic subgroup was found to have frequent mutations in ATRX, TP53 and displays alternative lengthening of telomeres. The second subgroup with oligodendrocytic morphology has frequent mutations in CIC or FUBP1, and is linked to co-deletion of the 1p/19q arms. These mutations reflect the development of two distinct molecular pathways representing the majority of IDH1 mutant gliomas. Unfortunately, due to the scarcity of endogenously derived IDH1 mutant models, there is a lack of accurate models to study mechanism and develop new therapy. Here we report the generation of an endogenous IDH1 anaplastic astrocytoma in vivo model with concurrent mutations in TP53, CDKN2A and ATRX. The model has a similar phenotype and histopathology as the original patient tumor, expresses the IDH1 (R132H) mutant protein and exhibits an alternative lengthening of telomeres phenotype. The JHH-273 model is characteristic of anaplastic astrocytoma and represents a valuable tool for investigating the pathogenesis of this distinct molecular subset of gliomas and for preclinical testing of compounds targeting IDH1 mutations or alternative lengthening of telomeres.

Repurposing the antihelmintic mebendazole as a hedgehog inhibitor

The hedgehog (Hh) signaling pathway is activated in many types of cancer and therefore presents an attractive target for new anticancer agents. Here, we show that mebendazole, a benzamidazole with a long history of safe use against nematode infestations and hydatid disease, potently inhibited Hh signaling and slowed the growth of Hh-driven human medulloblastoma cells at clinically attainable concentrations. As an antiparasitic, mebendazole avidly binds nematode tubulin and causes inhibition of intestinal microtubule synthesis. In human cells, mebendazole suppressed the formation of the primary cilium, a microtubule-based organelle that functions as a signaling hub for Hh pathway activation. The inhibition of Hh signaling by mebendazole was unaffected by mutants in the gene that encodes human Smoothened (SMO), which are selectively propagated in cell clones that survive treatment with the Hh inhibitor vismodegib. Combination of vismodegib and mebendazole resulted in additive Hh signaling inhibition. Because mebendazole can be safely administered to adults and children at high doses over extended time periods, we propose that mebendazole could be rapidly repurposed and clinically tested as a prospective therapeutic agent for many tumors that are dependent on Hh signaling.

EFFECT OF THE ANTIPARASITIC DRUG MEBENDAZOLE ON CHOLANGIOCARCINOMA GROWTH

Mebendazole (MBZ) is an anthelmintic drug which inhibits tubulin polymerization and eventually causes apoptosis in target organisms. Antitumor activity of MBZ has been reported in various cancers. The aim of this study was to investigate the effect of MBZ on cholangiocarcinoma (CCA) cells in vitro and in vivo. MBZ reduced cell proliferation in the KKU-M213 cell line associated with a remarkable enhancement of caspase-3 gene expression and enzyme activity. Oral administration of MBZ slightly reduced the growth rate of subcutaneously xeno-grafted KKU-M213 in nude mice. The TUNEL assay showed an increase of apoptotic cell numbers in the xenograft tumor tissue of MBZ-treated mice. The data obtained in this study suggested that MBZ can suppress CCA cell proliferation via caspase-3 activated apoptosis. Further investigation of the antitumor effects of MBZ might support the use of MBZ as an alternative drug for CCA treatment.

Detection of circulating tumor DNA in early- and late-stage human malignancies

The development of noninvasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital polymerase chain reaction-based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We found that ctDNA was detectable in >75% of patients with advanced pancreatic, ovarian, colorectal, bladder, gastroesophageal, breast, melanoma, hepatocellular, and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73, 57, 48, and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. ctDNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor blockade in 24 patients who objectively responded to therapy but subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase pathway. Together, these data suggest that ctDNA is a broadly applicable, sensitive, and specific biomarker that can be used for a variety of clinical and research purposes in patients with multiple different types of cancer.

Effective treatment of diverse medulloblastoma models with mebendazole and its impact on tumor angiogenesis

BACKGROUND

Medulloblastoma is the most common malignant brain tumor in children. Current standard treatments cure 40%-60% of patients, while the majority of survivors suffer long-term neurological sequelae. The identification of 4 molecular groups of medulloblastoma improved the clinical management with the development of targeted therapies; however, the tumor acquires resistance quickly. Mebendazole (MBZ) has a long safety record as antiparasitic in children and has been recently implicated in inhibition of various tyrosine kinases in vitro. Here, we investigated the efficacy of MBZ in various medulloblastoma subtypes and MBZ's impact on vascular endothelial growth factor receptor 2 (VEGFR2) and tumor angiogenesis.

METHODS

The inhibition of MBZ on VEGFR2 kinase was investigated in an autophosphorylation assay and a cell-free kinase assay. Mice bearing orthotopic PTCH1-mutant medulloblastoma allografts, a group 3 medulloblastoma xenograft, and a PTCH1-mutant medulloblastoma with acquired resistance to the smoothened inhibitor vismodegib were treated with MBZ. The survival benefit and the impact on tumor angiogenesis and VEGFR2 kinase function were analyzed.

RESULTS

We determined that MBZ interferes with VEGFR2 kinase by competing with ATP. MBZ selectively inhibited tumor angiogenesis but not the normal brain vasculatures in orthotopic medulloblastoma models and suppressed VEGFR2 kinase in vivo. MBZ significantly extended the survival of medulloblastoma models derived from different molecular backgrounds.

CONCLUSION

Our findings support testing of MBZ as a possible low-toxicity therapy for medulloblastomas of various molecular subtypes, including tumors with acquired vismodegib resistance. Its antitumor mechanism may be partially explained by inhibition of tumor angiogenesis.

5-azacytidine reduces methylation, promotes differentiation and induces tumor regression in a patient-derived IDH1 mutant glioma xenograft

Somatic mutations in Isocitrate Dehydrogenase 1 (IDH1) are frequent in low grade and progressive gliomas and are characterized by the production of 2-hydroxyglutarate (2-HG) from α-ketoglutarate by the mutant enzyme. 2-HG is an “oncometabolite” that competitively inhibits α-KG dependent dioxygenases resulting in various widespread cellular changes including abnormal hypermethylation of genomic DNA and suppression of cellular differentiation. Despite the growing understanding of IDH mutant gliomas, the development of effective therapies has proved challenging in part due to the scarcity of endogenous mutant in vivo models. Here we report the generation of an endogenous IDH1 anaplastic astrocytoma model which rapidly grows in vivo, produces 2-HG and exhibits DNA hypermethylation. Using this model, we have demonstrated the preclinical efficacy and mechanism of action of the FDA approved demethylating drug 5-azacytidine in vivo. Long term administration of 5-azacytidine resulted in reduction of DNA methylation of promoter loci, induction of glial differentiation, reduction of cell proliferation and a significant reduction in tumor growth. Tumor regression was observed at 14 weeks and subsequently showed no signs of re-growth at 7 weeks despite discontinuation of therapy. These results have implications for clinical trials of demethylating agents for patients with IDH mutated gliomas.

Tumor subtype-specific cancer-testis antigens as potential biomarkers and immunotherapeutic targets for cancers

Cancer-testis (CT) antigens are potential targets for cancer immunotherapy because of their restricted expression in immune-privileged germ cells and various malignancies. Current application of CT-based immunotherapy has been focused on CT expression-rich tumors such as melanoma and lung cancers. In this study, we surveyed CT expression using The Cancer Genome Atlas (TCGA) datasets for ten common cancer types. We show that CT expression is specific and enriched within certain cancer molecular subtypes. For example, HORMAD1, CXorf61, ACTL8, and PRAME are highly enriched in the basal subtype of breast cancer; MAGE and CSAG are most frequently activated in the magnoid subtype of lung adenocarcinoma; and PRAME is highly upregulated in the ccB subtype of clear cell renal cell carcinoma. Analysis of CT gene expression and DNA methylation indicates that some CTs are regulated epigenetically, whereas others are controlled primarily by tissue- and subtype-specific transcription factors. Our results suggest that although for some CT expression is associated with patient outcome, not many are independent prognostic markers. Thus, CTs with shared expression pattern are heterogeneous molecules with distinct activation modes and functional properties in different cancers and cancer subtypes. These data suggest a cancer subtype-orientated application of CT antigen as biomarkers and immunotherapeutic targets.

Preclinical evaluation of the combination of mTOR and proteasome inhibitors with radiotherapy in malignant peripheral nerve sheath tumors

About one half of malignant peripheral nerve sheath tumors (MPNST) have Neurofibromin 1 (NF1) mutations. NF1 is a tumor suppressor gene essential for negative regulation of RAS signaling. Survival for MPNST patients is poor and we sought to identify an effective combination therapy. Starting with the mTOR inhibitors rapamycin and everolimus, we screened for synergy in 542 FDA approved compounds using MPNST cells with a native NF1 loss in both alleles. We further analyzed the cell cycle and signal transduction. In vivo growth effects of the drug combination with local radiation therapy (RT) were assessed in MPNST xenografts. The synergistic combination of mTOR inhibitors with bortezomib yielded a reduction in MPNST cell proliferation. The combination of mTOR inhibitors and bortezomib also enhanced the anti-proliferative effect of radiation in vitro. In vivo, the combination of mTOR inhibitor (everolimus) and bortezomib with RT decreased tumor growth and proliferation, and augmented apoptosis. The combination of approved mTOR and proteasome inhibitors with radiation showed a significant reduction of tumor growth in an animal model and should be investigated and optimized further for MPNST therapy.

Activated macrophages promote Wnt/β-catenin signaling in cholangiocarcinoma cells

The Wnt/β-catenin signaling pathway is pathologically activated in cholangiocarcinoma (CCA). Here, we determined the expression profile as well as biological role of activated Wnt/β-catenin signaling in CCA. The quantitative reverse transcription polymerase chain reaction demonstrated that Wnt3a, Wnt5a, and Wnt7b mRNA were significantly higher in CCA tissues than adjacent non-tumor tissues and normal liver tissues. Immunohistochemical staining revealed that Wnt3a, Wnt5a, and Wnt7b were positive in 92.1, 76.3, and 100 % of 38 CCA tissues studied. It was noted that Wnt3 had a low expression in tumor cells, whereas a high expression was mainly found in inflammatory cells. Interestingly, a high expression level of Wnt5a was significantly correlated to poor survival of CCA patients (P=0.009). Membrane localization of β-catenin was reduced in the tumors compared to normal bile duct epithelia, and we also found that 73.7 % of CCA cases showed the cytoplasmic localization. Inflammation is known to be a risk factor for CCA development, and we tested whether this might induce Wnt/β-catenin signaling. We found that lipopolysaccharides (LPS) elevated the expression of Wnt3 both mRNA and protein levels in the macrophage cell line. Additionally, the conditioned media taken from LPS-induced activated macrophage culture promoted β-catenin accumulation in CCA cells. Furthermore, transient suppression of β-catenin by siRNA significantly induced growth inhibition of CCA cells, concurrently with decreasing cyclin D1 protein level. In conclusion, the present study reports the abundant expression of Wnt protein family and β-catenin in CCA as well as the effect of inflammatory condition on Wnt/β-catenin activation in CCA cells. Importantly, abrogation of β-catenin expression caused significant CCA cell growth inhibition. Thus, the Wnt/β-catenin signaling pathway may contribute to CCA cell proliferation and hence may serve as a prognostic marker for CCA progression and provide a potential target for CCA therapy.

Cancer biomarker discovery for cholangiocarcinoma: the high-throughput approaches

Cholangiocarcinoma (CCA) is difficult to diagnose at an early stage and most tumors are detected at late stage where surgery or other therapy is ineffective. Many advanced techniques are applied to diagnose CCA; however, most are expensive and have varying degrees of accuracy. A less invasive and simpler procedure such as serum markers would be of substantial clinical benefit for diagnosis, monitoring, and predicting outcome for CCA patients. Recent advances in "Omics" technologies offer remarkable opportunities for establishment of biomarker-related to diseases. In this review, the potential biomarkers obtained from proteomics and glycomic studies are evaluated. Several protein markers were discovered from patient specimen, using two dimensional-differential gel electrophoresis couple with liquid chromatography tandem mass spectrometry (2D-DIGE/LC-MS-MS), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), surface enhanced laser desorption/ionization (SELDI)-TOF-MS and capillary electrophoresis (CE)-MS, etc. Newly reported CCA-associated glyco-biomarkers were identified using lectin-assisted, monoclonal antibody-assisted or specific-target strategies. The combination between carbohydrate binding-lectin and core protein-binding mAb significantly increased the values for detection of the glyco-biomarkers for CCA. Searching for specific and sensitive molecular markers to be used for population screening is worth being evaluated. This could lead to earlier diagnosis and improve outcome. Further investigation of those biomarker functions is also of value in order to better understand the tumor biology and use them as targets for future therapeutic agents.

Exomic sequencing of four rare central nervous system tumor types

A heterogeneous population of uncommon neoplasms of the central nervous system (CNS) cause significant morbidity and mortality. To explore their genetic origins, we sequenced the exomes of 12 pleomorphic xanthoastrocytomas (PXA), 17 non-brainstem pediatric glioblastomas (PGBM), 8 intracranial ependymomas (IEP) and 8 spinal cord ependymomas (SCEP). Analysis of the mutational spectra revealed that the predominant single base pair substitution was a C:G>T:A transition in each of the four tumor types. Our data confirm the critical roles of several known driver genes within CNS neoplasms, including TP53 and ATRX in PGBM, and NF2 in SCEPs. Additionally, we show that activating BRAF mutations play a central role in both low and high grade glial tumors. Furthermore, alterations in genes coding for members of the mammalian target of rapamycin (mTOR) pathway were observed in 33% of PXA. Our study supports the hypothesis that pathologically similar tumors arising in different age groups and from different compartments may represent distinct disease processes with varied genetic composition.

NY-ESO-1 expression in meningioma suggests a rationale for new immunotherapeutic approaches

Meningiomas are the most common primary intracranial tumors. Surgical resection remains the treatment of choice for these tumors. However, a significant number of tumors are not surgically accessible, recur, or become malignant, necessitating the repetition of surgery and sometimes radiation. Chemotherapy is rarely used and is generally not recognized as an effective treatment. Cancer/testis (CT) genes represent a unique class of genes, which are expressed by germ cells, normally silenced in somatic cells, but activated in various cancers. CT proteins can elicit spontaneous immune responses in patients with cancer and this feature makes them attractive targets for immunotherapy-based approaches. We analyzed mRNA expression of 37 testis-restricted CT genes in a discovery set of 18 meningiomas by reverse transcription PCR. The overall frequency of expression of CT genes ranged from 5.6% to 27.8%. The most frequently expressed was NY-ESO-1, in 5 patients (27.8%). We subsequently analyzed NY-ESO-1 protein expression in a larger set of meningiomas by immunohistochemistry and found expression in 108 of 110 cases. In some cases, NY-ESO-1 expression was diffused and homogenous, but in most instances it was heterogeneous. Importantly, NY-ESO-1 expression was positively correlated with higher grade and patients presenting with higher levels of NY-ESO-1 staining had significantly worse disease-free and overall survival. We have also shown that NY-ESO-1 expression may lead to humoral immune response in patients with meningioma. Considering the limited treatment options for patients with meningioma, the potential of NY-ESO-1-based immunotherapy should be explored.

Podocalyxin-like protein is expressed in glioblastoma multiforme stem-like cells and is associated with poor outcome

Glioblastoma multiforme (GBM) is the most common primary malignant adult brain tumor and is associated with poor survival. Recently, stem-like cell populations have been identified in numerous malignancies including GBM. To identify genes whose expression is changed with differentiation, we compared transcript profiles from a GBM oncosphere line before and after differentiation. Bioinformatic analysis of the gene expression profiles identified podocalyxin-like protein (PODXL), a protein highly expressed in human embryonic stem cells, as a potential marker of undifferentiated GBM stem-like cells. The loss of PODXL expression upon differentiation of GBM stem-like cell lines was confirmed by quantitative real-time PCR and flow cytometry. Analytical flow cytometry of numerous GBM oncosphere lines demonstrated PODXL expression in all lines examined. Knockdown studies and flow cytometric cell sorting experiments demonstrated that PODXL is involved in GBM stem-like cell proliferation and oncosphere formation. Compared to PODXL-negative cells, PODXL-positive cells had increased expression of the progenitor/stem cell markers Musashi1, SOX2, and BMI1. Finally, PODXL expression directly correlated with increasing glioma grade and was a marker for poor outcome in patients with GBM. In summary, we have demonstrated that PODXL is expressed in GBM stem-like cells and is involved in cell proliferation and oncosphere formation. Moreover, high PODXL expression correlates with increasing glioma grade and decreased overall survival in patients with GBM.

Noninvasive imaging of infection after treatment with tumor-homing bacteria using Chemical Exchange Saturation Transfer (CEST) MRI

PURPOSE

To develop a noninvasive MRI method for determining the germination and infection of tumor-homing bacteria in bacteriolytic cancer therapy using endogenous CEST contrast.

METHODS

The CEST parameters of the anaerobic gram-positive bacterium Clostridium novyi-NT (C. novyi-NT) were first characterized in vitro, then used to detect C. novyi-NT germination and infection in subcutaneous CT26 colorectal tumor-bearing mice (n = 6) after injection of 300 million bacterial spores. Lipopolysacharide (LPS) injected mice were used to exclude that the changes of CEST MRI were due to inflammation.

RESULTS

CEST contrast was observed over a broad frequency range for bacterial suspensions in vitro, with the maximum contrast around 2.6 ppm from the water resonance. No signal could be detected for bacterial spores, demonstrating the specificity for germination. In vivo, a significant elevation of CEST contrast was identified in C. novyi-NT infected tumors as compared to those before bacterial germination and infection (P < 0.05; n = 6). No significant change was observed in tumors with LPS-induced sterile inflammation (P > 0.05; n = 4).

CONCLUSION

Endogenous bacterial CEST contrast (bacCEST) can be used to monitor the germination and proliferation of the therapeutic bacterium C. novyi-NT without a need for exogenous cell labeling probes.