The irreversible FGFR inhibitor KIN-3248 overcomes FGFR2 kinase domain mutations

PURPOSE

FGFR2 and FGFR3 show oncogenic activation in many cancer types, often through chromosomal fusion or extracellular domain mutation. FGFR2 and FGFR3 alterations are most prevalent in intrahepatic cholangiocarcinoma (ICC) and bladder cancers, respectively, and multiple selective reversible and covalent pan-FGFR tyrosine kinase inhibitors (TKIs) have been approved in these contexts. However, resistance, often due to acquired secondary mutations in the FGFR2/3 kinase domain, limits efficacy. Resistance is typically polyclonal, involving a spectrum of different mutations that most frequently affect the molecular brake and gatekeeper residues (N550 and V565 in FGFR2).

EXPERIMENTAL DESIGN

Here we characterize the activity of the next-generation covalent FGFR inhibitor, KIN-3248, in preclinical models of FGFR2 fusion+ ICC harboring a series of secondary kinase domain mutations, in vitro and in vivo. We also test select FGFR3 alleles in bladder cancer models.

RESULTS

KIN-3248 exhibits potent selectivity for FGFR1-3 and retains activity against various FGFR2 kinase domain mutations, in addition to being effective against FGFR3 V555M and N540K mutations. Notably, KIN-3248 activity extends to the FGFR2 V565F gatekeeper mutation, which causes profound resistance to currently approved FGFR inhibitors. Combination treatment with EGFR or MEK inhibitors potentiates KIN-3248 efficacy in vivo, including in models harboring FGFR2 kinase domain mutations.

CONCLUSIONS

Thus, KIN-3248 is a novel FGFR1-4 inhibitor whose distinct activity profile against FGFR kinase domain mutations highlights its potential for the treatment of ICC and other FGFR-driven cancers.

Discovery of KIN-3248, An Irreversible, Next Generation FGFR Inhibitor for the Treatment of Advanced Tumors Harboring FGFR2 and/or FGFR3 Gene Alterations

Fibroblast growth factor receptor (FGFR) alterations are present as oncogenic drivers and bypass mechanisms in many forms of cancer. These alterations can include fusions, amplifications, rearrangements, and mutations. Acquired drug resistance to current FGFR inhibitors often results in disease progression and unfavorable outcomes for patients. Genomic profiling of tumors refractory to current FGFR inhibitors in the clinic has revealed several acquired driver alterations that could be the target of next generation therapeutics. Herein, we describe how structure-based drug design (SBDD) was used to enable the discovery of the potent and kinome selective pan-FGFR inhibitor KIN-3248, which is active against many acquired resistance mutations. KIN-3248 is currently in phase I clinical development for the treatment of advanced tumors harboring FGFR2 and/or FGFR3 gene alterations.

Pan-Cancer Pharmacogenomic Analysis of Patient-Derived Tumor Cells Using Clinically Relevant Drug Exposures

As a result of tumor heterogeneity and solid cancers harboring multiple molecular defects, precision medicine platforms in oncology are most effective when both genetic and pharmacologic determinants of a tumor are evaluated. Expandable patient-derived xenograft (PDX) mouse tumor and corresponding PDX culture (PDXC) models recapitulate many of the biological and genetic characteristics of the original patient tumor, allowing for a comprehensive pharmacogenomic analysis. Here, the somatic mutations of 23 matched patient tumor and PDX samples encompassing four cancers were first evaluated using next-generation sequencing (NGS). 19 antitumor agents were evaluated across 78 patient-derived tumor cultures using clinically relevant drug exposures. A binarization threshold sensitivity classification determined in culture (PDXC) was used to identify tumors that best respond to drug in vivo (PDX). Using this sensitivity classification, logic models of DNA mutations were developed for 19 antitumor agents to predict drug response. We determined that the concordance of somatic mutations across patient and corresponding PDX samples increased as variant allele frequency increased. Notable individual PDXC responses to specific drugs, as well as lineage-specific drug responses were identified. Robust responses identified in PDXC were recapitulated in vivo in PDX-bearing mice and logic modeling determined somatic gene mutation(s) defining response to specific antitumor agents. In conclusion, combining NGS of primary patient tumors, high-throughput drug screen using clinically relevant doses, and logic modeling, can provide a platform for understanding response to therapeutic drugs targeting cancer.

Functional genomic analysis of adult and pediatric brain tumor isolates

Background

Adult and pediatric tumors display stark differences in their mutation spectra and chromosome alterations. Here, we attempted to identify common and unique gene dependencies and their associated biomarkers among adult and pediatric tumor isolates using functional genetic lethal screens and computational modeling.

Methods

We performed CRISRP-Cas9 lethality screens in two adult glioblastoma (GBM) tumor isolates and five pediatric brain tumor isolates representing atypical teratoid rhabdoid tumors (ATRT), diffuse intrinsic pontine glioma, GBM, and medulloblastoma. We then integrated the screen results with machine learning-based gene-dependency models generated from data from >900 cancer cell lines.

Results

We found that >50% of candidate dependencies of 280 identified were shared between adult GBM tumors and individual pediatric tumor isolates. 68% of screen hits were found as nodes in our network models, along with shared and tumor-specific predictors of gene dependencies. We investigated network predictors associated with ADAR, EFR3A, FGFR1 (pediatric-specific), and SMARCC2 (ATRT-specific) gene dependency among our tumor isolates.

Conclusions

The results suggest that, despite harboring disparate genomic signatures, adult and pediatric tumor isolates share a preponderance of genetic dependences. Further, combining data from primary brain tumor lethality screens with large cancer cell line datasets produced valuable insights into biomarkers of gene dependency, even for rare cancers.

Importance of the Study

Our results demonstrate that large cancer cell lines data sets can be computationally mined to identify known and novel gene dependency relationships in adult and pediatric human brain tumor isolates. Gene dependency networks and lethality screen results represent a key resource for neuro-oncology and cancer research communities. We also highlight some of the challenges and limitations of this approach.

Cannabidiol Inhibits RAD51 and Sensitizes Glioblastoma to Temozolomide in Multiple Orthotopic Tumor Models

Background

Cannabidiol (CBD), a nonpsychoactive cannabinoid with a low toxicity profile, has been shown to produce antitumor activity across cancers in part through selective production of reactive oxygen species (ROS) in tumor cells. The alkylating agent, temozolomide (TMZ), is standard of care for treatment of glioblastoma (GBM). It can trigger increased ROS to induce DNA damage. It has also been reported that downregulating the expression of RAD51, an important DNA damage repair protein, leads to sensitization of GBM to TMZ.

Methods

We determined the extent to which CBD enhanced the antitumor activity of TMZ in multiple orthotopic models of GBM. In addition, we investigated the potential for CBD to enhance the antitumor activity of TMZ through production of ROS and modulation of DNA repair pathways.

Results

CBD enhanced the activity of TMZ in U87 MG and U251 GBM cell lines and in patient-derived primary GBM163 cells leading to stimulation of ROS, activation of the ROS sensor AMP-activated protein kinase (AMPK), and upregulation of the autophagy marker LC3A. CBD produced a sensitization of U87 and GBM163-derived intracranial (i.c.) tumors to TMZ and significantly increased survival of tumor-bearing mice. However, these effects were not observed in orthotopic models derived from GBM with intact methylguanine methyltransferase (MGMT) expression. We further demonstrate that CBD inhibited RAD51 expression in MGMT-methylated models of GBM, providing a potential mechanism for tumor sensitization to TMZ by CBD.

Conclusion

These data support the potential therapeutic benefits of using CBD to enhance the antitumor activity of TMZ in GBM patients.

EXTH-62. COMBINATORIAL THERAPY TARGETING TRANSCIPTION AND IMMUNO-METABOLISM IN RECURRENT GLIOBLASTOMA

Recurrent glioblastomas (GBM) are notoriously difficult to treat, and in spite of aggressive chemo- and radiation therapy they inevitably recur in almost all GBM patients within 14 months following initial diagnosis. To interrogate pathways driving therapeutic resistance, we compared matched primary and recurrent IDH wild type glioblastoma samples from a cohort of patients, using RNA-Seq. Our analyses showed that pathways involved with tumor immune and metabolic reprogramming were up-regulated in recurrent GBMs compared to untreated, primary samples. Based on these findings, we tested the anti-tumor efficacy of over 20 rationally selected targeted therapeutic agents alone and in combination in a high-throughput drug screen assay designed to measure long term cell viability of primary tumorspheres from patients who underwent surgery for recurrent GBM. Top performing drug combinations from these screens were validated in vivo using patient-derived intracranial mouse models of glioma. Our data demonstrated that the combination of the transcriptional/metabolic inhibitor TG02 and the dual PI3K/mTOR inhibitor GDC-0084 significantly prolonged in vivo survival of tumor bearing mice, performing better than either drug alone. Notably, both inhibitors are undergoing human clinical trials as single agents with positive initial safety profiles and superior blood brain barrier penetrance. RNA Seq and functional assays of tumor samples from treated mice showed that only the combination treatment (TG02 + GDC-0084) significantly inhibited expression of immunomodulatory cytokines driving tumor progression, including those identified by us to be overexpressed in recurrent human GBM samples. Overall, these data suggest that combining TG02 and GDC-0084 is an effective treatment for recurrent GBMs. Furthermore, our results support the use of a translational research platform consisting of a personalized pharmaco-genomics testing, using patient-derived tumor samples towards designing more effective treatment for recurrent GBM patients.

Niraparib Suppresses Cholangiocarcinoma Tumor Growth by Inducing Oxidative and Replication Stress

Simple Summary

Cholangiocarcinoma (CCA) is a rare and highly aggressive tumor with limited therapeutic options, thus underscoring the need to develop novel therapeutic approaches. We analyzed a publicly available CCA patient database to identify mutations in DNA damage response (DDR) genes. Mutations in DDR genes were prevalent, thus rendering these tumors potentially susceptible to poly-ADP-ribose polymerase (PARP) inhibition. PARP genes are critical to DNA repair and genomic stability. The role of PARP inhibitors in CCA was investigated by employing a series of in vitro functional assays and in vivo patient-derived xenograft models. This study highlights the therapeutic potential of PARP inhibitors alone or in combination with the chemotherapeutic agent gemcitabine for the treatment of CCA.

Abstract

Cholangiocarcinoma (CCA) is the second most common hepatobiliary cancer, an aggressive malignancy with limited therapeutic options. PARP (poly (ADP-ribose) polymerase) 1 and 2 are important for deoxyribonucleotide acid (DNA) repair and maintenance of genomic stability. PARP inhibitors (PARPi) such as niraparib have been approved for different malignancies with genomic alteration in germline BRCA and DNA damage response (DDR) pathway genes. Genomic alterations were analyzed in DDR genes in CCA samples employing The Cancer Genome Atlas (TCGA) database. Mutations were observed in various DDR genes, and 35.8% cases had alterations in at least one of three genes (ARID1A, BAP1 and ATM), suggesting their susceptibility to PARPi. Niraparib treatment suppressed cancer cell viability and survival, and also caused G2/M cell cycle arrest in patient-derived xenograft cells lines (PDXC) and established CCA cells harboring DDR gene mutations. PARPi treatment also induced apoptosis and caspase3/7 activity in PDXC and CCA cell lines, and substantially reduced expression of BCL2, BCL-XL and MCL1 proteins. Niraparib caused a significant increase in oxidative stress, and induced activation of DNA damage markers, phosphorylation of CHK2 and replication fork stalling. Importantly, niraparib, in combination with gemcitabine, produced sustained and robust inhibition of tumor growth in vivo in a patient-derived xenograft (PDX) model more effectively than either treatment alone. Furthermore, tissue samples from mice treated with niraparib and gemcitabine display significantly lower expression levels of pHH3 and Ki-67, which are a mitotic and proliferative marker, respectively. Taken together, our results indicate niraparib as a novel therapeutic agent alone or in combination with gemcitabine for CCA.

Cannabidiol Treatment Results in a Common Gene Expression Response Across Aggressive Cancer Cells from Various Origins

Background: We previously reported that cannabidiol (CBD), a cannabinoid with a low toxicity profile, downregulated the expression of the prometastatic gene inhibitor of DNA binding 1 (ID1) in cancer cells, leading to inhibition of tumor progression in vivo. While CBD is broadly used, including in the self-medication of cancer patients, and CBD-based therapies are undergoing clinical evaluation for cancer treatment, its mechanisms of action are still poorly understood. Methods: In this study, using microarray analysis and Western blot analysis for validation, we attempted to identify the full spectrum of genes regulated by CBD across various aggressive cancer cell lines, including the breast, brain, head and neck, and prostate. Results: We confirmed that ID1 was a major target downregulated by CBD and also discovered that CBD inhibited FOXM1 (Forkhead box M1), a transcriptional activator involved in cell proliferation, while simultaneously upregulating GDF15 (growth differentiation factor 15), a cytokine associated with tissue differentiation. Conclusion: Our results suggest that, by modulating expression of shared key cancer-driving genes, CBD could represent a promising nontoxic therapeutic for treating tumors of various origins.

Nuclear Receptor Coactivator NCOA3 Regulates UV Radiation-Induced DNA Damage and Melanoma Susceptibility

Melanoma occurs as a consequence of inherited susceptibility to the disease and exposure to UV radiation (UVR) and is characterized by uncontrolled cellular proliferation and a high mutational load. The precise mechanisms by which UVR contributes to the development of melanoma remain poorly understood. Here we show that activation of nuclear receptor coactivator 3 (NCOA3) promotes melanomagenesis through regulation of UVR sensitivity, cell-cycle progression, and circumvention of the DNA damage response (DDR). Downregulation of NCOA3 expression, either by genetic silencing or small-molecule inhibition, significantly suppressed melanoma proliferation in melanoma cell lines and patient-derived xenografts. NCOA3 silencing suppressed expression of xeroderma pigmentosum C and increased melanoma cell sensitivity to UVR. Suppression of NCOA3 expression led to activation of DDR effectors and reduced expression of cyclin B1, resulting in G₂-M arrest and mitotic catastrophe. A SNP in NCOA3 (T960T) reduced NCOA3 protein expression and was associated with decreased melanoma risk, given a significantly lower prevalence in a familial melanoma cohort than in a control cohort without cancer. Overexpression of wild-type NCOA3 promoted melanocyte survival following UVR and was accompanied by increased levels of UVR-induced DNA damage, both of which were attenuated by overexpression of NCOA3 (T960T). These results describe NCOA3-regulated pathways by which melanoma can develop, with germline NCOA3 polymorphisms enabling enhanced melanocyte survival in the setting of UVR exposure, despite an increased mutational burden. They also identify NCOA3 as a novel therapeutic target for melanoma. SIGNIFICANCE: This study explores NCOA3 as a regulator of the DDR and a therapeutic target in melanoma, where activation of NCOA3 contributes to melanoma development following exposure to ultraviolet light.

Drug responses are conserved across patient-derived xenograft models of melanoma leading to identification of novel drug combination therapies

BACKGROUND

Patient-derived xenograft (PDX) mouse tumour models can predict response to therapy in patients. Predictions made from PDX cultures (PDXC) would allow for more rapid and comprehensive evaluation of potential treatment options for patients, including drug combinations.

METHODS

We developed a PDX library of BRAF-mutant metastatic melanoma, and a high-throughput drug-screening (HTDS) platform utilising clinically relevant drug exposures. We then evaluated 34 antitumor agents across eight melanoma PDXCs, compared drug response to BRAF and MEK inhibitors alone or in combination with PDXC and the corresponding PDX, and investigated novel drug combinations targeting BRAF inhibitor-resistant melanoma.

RESULTS

The concordance of cancer-driving mutations across patient, matched PDX and subsequent PDX generations increases as variant allele frequency (VAF) increases. There was a high correlation in the magnitude of response to BRAF and MEK inhibitors between PDXCs and corresponding PDXs. PDXCs and corresponding PDXs from metastatic melanoma patients that progressed on standard-of-care therapy demonstrated similar resistance patterns to BRAF and MEK inhibitor therapy. Importantly, HTDS identified novel drug combinations to target BRAF-resistant melanoma.

CONCLUSIONS

The biological consistency observed between PDXCs and PDXs suggests that PDXCs may allow for a rapid and comprehensive identification of treatments for aggressive cancers, including combination therapies.

Durable multitransgene expression in vivo using systemic, nonviral DNA delivery

Recombinant adeno-associated virus (AAV) vectors are transforming therapies for rare human monogenic deficiency diseases. However, adaptive immune responses to AAV and its limited DNA insert capacity, restrict their therapeutic potential. HEDGES (high-level extended duration gene expression system), a nonviral DNA- and liposome-based gene delivery platform, overcomes these limitations in immunocompetent mice. Specifically, one systemic HEDGES injection durably produces therapeutic levels of transgene-encoded human proteins, including FDA-approved cytokines and monoclonal antibodies, without detectable integration into genomic DNA. HEDGES also controls protein production duration from <3 weeks to >1.5 years, does not induce anti-vector immune responses, is reexpressed for prolonged periods following reinjection, and produces only transient minimal toxicity. HEDGES can produce extended therapeutic levels of multiple transgene-encoded therapeutic human proteins from DNA inserts >1.5-fold larger than AAV-based therapeutics, thus creating combinatorial interventions to effectively treat common polygenic diseases driven by multigenic abnormalities.

Tissues Harvested Using an Automated Surgical Approach Confirm Molecular Heterogeneity of Glioblastoma and Enhance Specimen's Translational Research Value

Glioblastoma (GBM) is the most aggressive primary brain tumor in adults. Designing effective individualized therapies for GBM requires quality fresh tissue specimens, and a comprehensive molecular profile of this highly heterogenous neoplasm. Novel neuro-surgical approaches, such as the automated resection NICO Myriad™ system, are increasingly used by neurosurgeons to better reach the invasive front of tumors. However, no information exists on how harvesting GBM tissue using this approach may impact the translational research value of the sample. Here, we set out to characterize matched specimens from 15 patients, where one tissue sample was obtained using traditional tumor de-bulking (herein referred to as “en bloc” sample), and the other sample was obtained using the Myriad^TM System (herein referred to as “Myriad” sample). We investigated the fidelity of patient derived xenografts (PDXs) for each sample type to the corresponding human tissues and evaluated the added value of sequencing both samples for each patient. Matched en bloc and Myriad samples processed in parallel, were subjected to the following assays: cell viability, self-renewal, in vivo tumorigenicity using an orthotopic model of glioma, genomic sequencing, and pharmacological testing using PI3K-MTOR pathway inhibitors. Our results demonstrate that primary GBM cultures derived from matched specimens grew at similar rates (correlation coefficient R = 0.72), generated equivalent number of neurospheres, and had equivalent tumorigenic potential in vivo (mouse survival correlation coefficient R = 0.93). DNA Sequencing using the Illumina tumor panel amplicons revealed over 70% concordance in non-synonymous mutations between matched human GBM specimens. PDX genomic profiles were also highly concordant with the corresponding patient tissues (>70%). RNA sequencing of paired GBM samples revealed unique genomic variants and differential gene expression between the en bloc and Myriad specimens, with the former molecularly resembling the “tumor core” and the latter resembling the “invasive tumor front” signature. Functionally, we show that primary-derived GBM cells—obtained after fresh specimen's dissociation—are more effectively growth-inhibited by co-targeting non-overlapping mutations enriched in each sample type, suggesting that profiling both specimens more adequately capture the molecular heterogeneity of GBM and may enhance the design accuracy and efficacy of individualized therapies.

Novel tumor suppressor role of miRNA-876 in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a rare, highly invasive malignancy, and its incidence is increasing globally. MicroRNAs (miRNAs) mediate a wide array of cellular and biological processes and are dysregulated in various tumors. The functional and biological roles of miRNAs in CCA have not been fully elucidated. In this study, we show that miR-876 expression levels and copy number are significantly attenuated in the TCGA cohort of CCA tissue samples. TCGA expression data was consistent with the observed substantial decrease in miR-876 expression in patient samples and CCA cell lines. In-silico algorithm databases revealed BCL-XL as a potential target of miR-876. We observed miR-876 expression to be downregulated, whereas, BCL-XL upregulated in CCA cell lines. BCL-XL was identified as a direct functional target of miR-876 in CCA. miR-876-mediated reduction of BCL-XL regulated cell survival, induced apoptosis and caspase 3/7 expression in CCA. BCL-XL overexpression reversed the miR-876 mediated effect on CCA cell growth and apoptosis. Stable overexpression of miR-876 produced potent tumor suppressor activity and in vivo tumor cell growth reduction. Overexpression of miR-876 in a patient-derived xenograft (PDX) cell line significantly suppressed BCL-XL expression and spheroid formation with a concomitant induction of caspase 3/7 activity and apoptosis. This study demonstrates a novel tumor suppressor role for miR-876 in CCA, identifies BCL-XL as an actionable target, and suggests a potential therapeutic role for miR-876 in CCA.

Toxoplasma Modulates Signature Pathways of Human Epilepsy, Neurodegeneration & Cancer

One third of humans are infected lifelong with the brain-dwelling, protozoan parasite, Toxoplasma gondii. Approximately fifteen million of these have congenital toxoplasmosis. Although neurobehavioral disease is associated with seropositivity, causality is unproven. To better understand what this parasite does to human brains, we performed a comprehensive systems analysis of the infected brain: We identified susceptibility genes for congenital toxoplasmosis in our cohort of infected humans and found these genes are expressed in human brain. Transcriptomic and quantitative proteomic analyses of infected human, primary, neuronal stem and monocytic cells revealed effects on neurodevelopment and plasticity in neural, immune, and endocrine networks. These findings were supported by identification of protein and miRNA biomarkers in sera of ill children reflecting brain damage and T. gondii infection. These data were deconvoluted using three systems biology approaches: "Orbital-deconvolution" elucidated upstream, regulatory pathways interconnecting human susceptibility genes, biomarkers, proteomes, and transcriptomes. "Cluster-deconvolution" revealed visual protein-protein interaction clusters involved in processes affecting brain functions and circuitry, including lipid metabolism, leukocyte migration and olfaction. Finally, "disease-deconvolution" identified associations between the parasite-brain interactions and epilepsy, movement disorders, Alzheimer's disease, and cancer. This "reconstruction-deconvolution" logic provides templates of progenitor cells' potentiating effects, and components affecting human brain parasitism and diseases.

A Cell-Surface Membrane Protein Signature for Glioblastoma

We present a systems strategy that facilitated the development of a molecular signature for glioblastoma (GBM), composed of 33 cell-surface transmembrane proteins. This molecular signature, GBMSig, was developed through the integration of cell-surface proteomics and transcriptomics from patient tumors in the REMBRANDT (n = 228) and TCGA datasets (n = 547) and can separate GBM patients from control individuals with a Matthew's correlation coefficient value of 0.87 in a lock-down test. Functionally, 17/33 GBMSig proteins are associated with transforming growth factor β signaling pathways, including CD47, SLC16A1, HMOX1, and MRC2. Knockdown of these genes impaired GBM invasion, reflecting their role in disease-perturbed changes in GBM. ELISA assays for a subset of GBMSig (CD44, VCAM1, HMOX1, and BIGH3) on 84 plasma specimens from multiple clinical sites revealed a high degree of separation of GBM patients from healthy control individuals (area under the curve is 0.98 in receiver operating characteristic). In addition, a classifier based on these four proteins differentiated the blood of pre- and post-tumor resections, demonstrating potential clinical value as biomarkers.

Selective Toxicity of a Highly Potent Camptothecin Analogue: A Pilot Study with Glioblastoma Multiforme Cells

BACKGROUND/AIM

We developed a novel camptothecin analogue, CPT417, that yields reduced toxicity compared to other analogues used in chemotherapeutic regimens. In this pilot study, we assessed the activity of CPT417 against glioblastoma multiforme (GBM) cells and glioma stem cells.

MATERIALS AND METHODS

The human U251 GBM cell line and normal human astrocytes were cultured in parallel for clonogenic survival analysis following exposure to increasing concentrations of CPT417. Cell viability of a glioma stem cell line was assessed 5 days after exposure to a range of CPT417 concentrations.

RESULTS

CPT417 completely inhibited clonogenic survival of GBM cells at 10 nM, whereas this concentration only inhibited astrocytes by approximately 50%. Cell viability analysis of glioma stem cell cultures yielded a half-maximal response at 15 nM.

CONCLUSION

CPT417 acts selectively against GBM cells at concentrations that are at least an order of magnitude below reported values for related alkylating agents in clinical use.

Cytomegalovirus Immediate-Early Proteins Promote Stemness Properties in Glioblastoma

Glioblastoma (GBM) is the most common and aggressive human brain tumor. Human cytomegalovirus (HCMV) immediate-early (IE) proteins that are endogenously expressed in GBM cells are strong viral transactivators with oncogenic properties. Here, we show how HCMV IEs are preferentially expressed in glioma stem-like cells (GSC), where they colocalize with the other GBM stemness markers, CD133, Nestin, and Sox2. In patient-derived GSCs that are endogenously infected with HCMV, attenuating IE expression by an RNAi-based strategy was sufficient to inhibit tumorsphere formation, Sox2 expression, cell-cycle progression, and cell survival. Conversely, HCMV infection of HMCV-negative GSCs elicited robust self-renewal and proliferation of cells that could be partially reversed by IE attenuation. In HCMV-positive GSCs, IE attenuation induced a molecular program characterized by enhanced expression of mesenchymal markers and proinflammatory cytokines, resembling the therapeutically resistant GBM phenotype. Mechanistically, HCMV/IE regulation of Sox2 occurred via inhibition of miR-145, a negative regulator of Sox2 protein expression. In a spontaneous mouse model of glioma, ectopic expression of the IE1 gene (UL123) specifically increased Sox2 and Nestin levels in the IE1-positive tumors, upregulating stemness and proliferation markers in vivo. Similarly, human GSCs infected with the HCMV strain Towne but not the IE1-deficient strain CR208 showed enhanced growth as tumorspheres and intracranial tumor xenografts, compared with mock-infected human GSCs. Overall, our findings offer new mechanistic insights into how HCMV/IE control stemness properties in GBM cells.

The Antitumor Activity of Plant-Derived Non-Psychoactive Cannabinoids

As a therapeutic agent, most people are familiar with the palliative effects of the primary psychoactive constituent of Cannabis sativa (CS), Δ(9)-tetrahydrocannabinol (THC), a molecule active at both the cannabinoid 1 (CB1) and cannabinoid 2 (CB2) receptor subtypes. Through the activation primarily of CB1 receptors in the central nervous system, THC can reduce nausea, emesis and pain in cancer patients undergoing chemotherapy. During the last decade, however, several studies have now shown that CB1 and CB2 receptor agonists can act as direct antitumor agents in a variety of aggressive cancers. In addition to THC, there are many other cannabinoids found in CS, and a majority produces little to no psychoactivity due to the inability to activate cannabinoid receptors. For example, the second most abundant cannabinoid in CS is the non-psychoactive cannabidiol (CBD). Using animal models, CBD has been shown to inhibit the progression of many types of cancer including glioblastoma (GBM), breast, lung, prostate and colon cancer. This review will center on mechanisms by which CBD, and other plant-derived cannabinoids inefficient at activating cannabinoid receptors, inhibit tumor cell viability, invasion, metastasis, angiogenesis, and the stem-like potential of cancer cells. We will also discuss the ability of non-psychoactive cannabinoids to induce autophagy and apoptotic-mediated cancer cell death, and enhance the activity of first-line agents commonly used in cancer treatment.

The role of BPTF in melanoma progression and in response to BRAF-targeted therapy

Background:

Bromodomain PHD finger transcription factor (BPTF) plays an important role in chromatin remodeling, but its functional role in tumor progression is incompletely understood. Here we explore the oncogenic effects of BPTF in melanoma.

Methods:

The consequences of differential expression of BPTF were explored using shRNA-mediated knockdown in several melanoma cell lines. Immunoblotting was used to assess the expression of various proteins regulated by BPTF. The functional role of BPTF in melanoma progression was investigated using assays of colony formation, invasion, cell cycle, sensitivity to selective BRAF inhibitors, and in xenograft models of melanoma progression (n = 12 mice per group). The biomarker role of BPTF in melanoma progression was assessed using fluorescence in situ hybridization and immunohistochemical analyses. All statistical tests were two-sided.

Results:

shRNA-mediated BPTF silencing suppressed the proliferative capacity (by 65.5%) and metastatic potential (by 66.4%) of melanoma cells. Elevated BPTF copy number (mean ≥ 3) was observed in 28 of 77 (36.4%) melanomas. BPTF overexpression predicted poor survival in a cohort of 311 melanoma patients (distant metastasis-free survival P = .03, and disease-specific survival P = .008), and promoted resistance to BRAF inhibitors in melanoma cell lines. Metastatic melanoma tumors progressing on BRAF inhibitors contained low BPTF-expressing, apoptotic tumor cell subclones, indicating the continued presence of drug-responsive subclones within tumors demonstrating overall resistance to anti-BRAF agents.

Conclusions:

These studies demonstrate multiple protumorigenic functions for BPTF and identify it as a novel target for anticancer therapy. They also suggest the combination of BPTF targeting with BRAF inhibitors as a novel therapeutic strategy for melanomas with mutant BRAF.

HCMV glycoprotein B is expressed in primary glioblastomas and enhances growth and invasiveness via PDGFR-alpha activation

Our laboratory first demonstrated that human cytomegalovirus (HCMV) is associated with the most deadly form of primary brain tumor, glioblastoma (GBM). We showed that HCMV glycoprotein B (gB) mediates viral cellular entry via the receptor tyrosine kinase PDGFR-alpha (PDGFRα), resulting in activation of the PI3K/Akt pathway, a critical signaling axis gliomagenesis. Here, we investigated the effects of gB overexpression on glioma progression. We demonstrate that gB is endogenously expressed in primary GBM samples and show that ectopic gB expression in glioma cells induced sustained phosphorylation of PDGFRα, Akt, and Src. Recombinant gB protein and the whole virus enhanced invasion of primary glioblastoma cells into Matrigel and rat brain slices, and this effect was specifically inhibited by neutralizing antibodies to either gB or PDGFRα. Importantly, neutralizing antibodies to gB significantly inhibited the invasiveness of patient-derived HCMV-positive glioblastoma cells, suggesting that functional inhibition of this viral protein could hinder glioblastoma progression. gB overexpression promoted in vivo glioma growth and enhanced phosphor-Akt levels and tumor cell dispersal relative to controls. Taken together, our results demonstrate that HCMV gB promotes key hallmarks of glioblastoma and suggest that targeting gB may have therapeutic benefits for patients with HCMV -positive gliomas.

Human cytomegalovirus gene expression in long-term infected glioma stem cells

The most common adult primary brain tumor, glioblastoma (GBM), is characterized by fifteen months median patient survival and has no clear etiology. We and others have identified the presence of human cytomegalovirus (HCMV) gene products endogenously expressed in GBM tissue and primary cells, with a subset of viral genes being consistently expressed in most samples. Among these viral genes, several have important oncomodulatory properties, regulating tumor stemness, proliferation, immune evasion, invasion and angiogenesis. These findings lead us to hypothesize that a specific HCMV gene signature may be associated with GBM pathogenesis. To investigate this hypothesis, we used glioma cell lines and primary glioma stem-like cells (GSC) infected with clinical and laboratory HCMV strains and measured relative viral gene expression levels along several time points up to 15 weeks post-infection. While HCMV gene expression was detected in several infected glioma lines through week 5 post-infection, only HCMV-infected GSC expressed viral gene products 15 weeks post-infection. Efficiency of infection across time was higher in GSC compared to cell lines. Importantly, HCMV-infected GSC outlived their uninfected counterparts, and this extended survival was paralleled by increased tumorsphere frequency and upregulation of stemness regulators, such as SOX2, p-STAT3, and BMX (a novel HCMV target identified in this study). Interleukin 6 (IL-6) treatment significantly upregulated HCMV gene expression in long-term infected glioma cultures, suggesting that pro-inflammatory signaling in the tumor milieu may further augment HCMV gene expression and subsequent tumor progression driven by viral-induced cellular signaling. Together, our data support a critical role for long-term, low-level HCMV infection in promoting survival, stemness, and proliferation of GSC that could significantly contribute to GBM pathogenesis.

Cidofovir: a novel antitumor agent for glioblastoma

PURPOSE

Cidofovir (CDV) is an U.S. Food and Drug Administration (FDA)-approved nucleoside antiviral agent used to treat severe human cytomegalovirus (HCMV) infection. Until now, no clear therapeutic effects of CDV have been reported outside of the setting of viral infection, including a potential role for CDV as an antineoplastic agent for the treatment of brain tumors.

EXPERIMENTAL DESIGN

We investigated the cytotoxicity of CDV against the glioblastoma cells, U87MG and primary SF7796, both in vitro and in vivo, using an intracranial xenograft model. Standard techniques for cell culturing, immunohistochemistry, Western blotting, and real-time PCR were employed. The survival of athymic mice (n = 8-10 per group) bearing glioblastoma tumors, treated with CDV alone or in combination with radiation, was analyzed by the Kaplan-Meier method and evaluated with a two-sided log-rank test.

RESULTS

CDV possesses potent antineoplastic activity against HCMV-infected glioblastoma cells. This activity is associated with the inhibition of HCMV gene expression and with activation of cellular apoptosis. Surprisingly, we also determined that CDV induces glioblastoma cell death in the absence of HCMV infection. CDV is incorporated into tumor cell DNA, which promotes double-stranded DNA breaks and induces apoptosis. In the setting of ionizing radiotherapy, the standard of care for glioblastoma in humans, CDV augments radiation-induced DNA damage and, further, promotes tumor cell death. Combination therapy with CDV and radiotherapy significantly extended the survival of mice bearing intracranial glioblastoma tumors.

CONCLUSION

We have identified a novel antiglioma property of the FDA-approved drug CDV, which heightens the cytotoxic effect of radiotherapy, the standard of care therapy for glioblastoma.

Cytomegalovirus pp71 protein is expressed in human glioblastoma and promotes pro-angiogenic signaling by activation of stem cell factor

Glioblastoma multiforme (GBM) is a highly malignant primary central nervous system neoplasm characterized by tumor cell invasion, robust angiogenesis, and a mean survival of 15 months. Human cytomegalovirus (HCMV) infection is present in >90% of GBMs, although the role the virus plays in GBM pathogenesis is unclear. We report here that HCMV pp71, a viral protein previously shown to promote cell cycle progression, is present in a majority of human GBMs and is preferentially expressed in the CD133+, cancer stem-like cell population. Overexpression of pp71 in adult neural precursor cells resulted in potent induction of stem cell factor (SCF), an important pro-angiogenic factor in GBM. Using double immunofluorescence, we demonstrate in situ co-localization of pp71 and SCF in clinical GBM specimens. pp71 overexpression in both normal and transformed glial cells increased SCF secretion and this effect was specific, since siRNA mediated knockdown of pp71 or treatment with the antiviral drug cidofovir resulted in decreased expression and secretion of SCF by HCMV-infected cells. pp71- induced upregulation of SCF resulted in downstream activation of its putative endothelial cell receptor, c-kit, and angiogenesis as measured by increased capillary tube formation in vitro. We demonstrate that pp71 induces a pro-inflammatory response via activation of NFΚB signaling which drives SCF expression. Furthermore, we show that pp71 levels and NFKB activation are selectively augmented in the mesenchymal subtype of human GBMs, characterized by worst patient outcome, suggesting that HCMV pp71-induced paracrine signaling may contribute to the aggressive phenotype of this human malignancy.

Id-1 is a key transcriptional regulator of glioblastoma aggressiveness and a novel therapeutic target

Glioblastoma is the most common form of primary adult brain tumors. A majority of glioblastomas grow invasively into distant brain tissue, leading to tumor recurrence, which is ultimately incurable. It is, therefore, essential to discover master regulators that control glioblastoma invasiveness and target them therapeutically. We show here that the transcriptional regulator Id-1 plays a critical role in modulating the invasiveness of glioblastoma cell lines and primary glioblastoma cells. Id-1 expression levels positively correlate with glioma cell invasiveness in culture and with histopathologic grades in patient biopsies. Id-1 knockdown dramatically reduces glioblastoma cell invasion that is accompanied by profound morphologic changes and robust reduction in expression levels of "mesenchymal" markers, as well as inhibition of self-renewal potential and downregulation of glioma stem cell markers. Importantly, genetic knockdown of Id-1 leads to a significant increase in survival in an orthotopic model of human glioblastoma. Furthermore, we show that a nontoxic compound, cannabidiol, significantly downregulates Id-1 gene expression and associated glioma cell invasiveness and self-renewal. In addition, cannabidiol significantly inhibits the invasion of glioblastoma cells through an organotypic brain slice and glioma progression in vivo. Our results suggest that Id-1 regulates multiple tumor-promoting pathways in glioblastoma and that drugs targeting Id-1 represent a novel and promising strategy for improving the therapy and outcome of patients with glioblastoma.

Loss of cell-surface laminin anchoring promotes tumor growth and is associated with poor clinical outcomes

Perturbations in the composition and assembly of extracellular matrices (ECM) contribute to progression of numerous diseases, including cancers. Anchoring of laminins at the cell surface enables assembly and signaling of many ECMs, but the possible contributions of altered laminin anchoring to cancer progression remain undetermined. In this study, we investigated the prominence and origins of defective laminin anchoring in cancer cells and its association with cancer subtypes and clinical outcomes. We found loss of laminin anchoring to be widespread in cancer cells. Perturbation of laminin anchoring originated from several distinct defects, which all led to dysfunctional glycosylation of the ECM receptor dystroglycan. In aggressive breast and brain cancers, defective laminin anchoring was often due to suppressed expression of the glycosyltransferase LARGE. Reduced expression of LARGE characterized a broad array of human tumors in which it was associated with aggressive cancer subtypes and poor clinical outcomes. Notably, this defect robustly predicted poor survival in patients with brain cancers. Restoring LARGE expression repaired anchoring of exogenous and endogenous laminin and modulated cell proliferation and tumor growth. Together, our findings suggest that defects in laminin anchoring occur commonly in cancer cells, are characteristic of aggressive cancer subtypes, and are important drivers of disease progression.

Abstract 5308: Id-1 gene and protein as novel therapeutic targets for metastatic cancer

During normal development and embryogenesis, helix-loop-helix Id proteins regulate the differentiation programs of many tissues. Moreover, recent studies have shown that dysregulated Id expression contributes to cancer progression and metastasis. Specifically, we found high levels of one of the Id family members, Id-1, in breast, prostate, brain and head and neck tumor cells which were highly aggressive, and low levels of Id-1 in non-invasive tumor cells. Ectopic expression of Id-1 in non-aggressive human cancer cells rendered them highly proliferative and invasive, and induced high levels of matrix metalloproteinase (MMP) expression. Conversely, human metastatic cancer cells became significantly less proliferative and invasive in culture when Id-1 protein expression was decreased by antisense RNA or shRNA directed against the Id-1 gene. Next, we asked whether Id-1 could be exploited as a therapeutic target to treat metastatic cancers. Using tumor-bearing animals and systemic gene targeting technique, we showed that reduction of Id-1 levels, and consequently MMP expression, could significantly decrease the metastatic spread of cancer cells. Further, several molecular pathways underlying Id-1 effects on epithelial to mesenchymal transition (EMT) and neoangiogenesis were also identified in certain types of cancer. These results suggested that Id-1 gene and/or protein could be a promising target for development of therapeutic strategies to reduce cancer metastasis. Since Id-1 expression is scarce in most mature adult tissues, a majority of normal cells would not be affected by systemic therapy targeting this gene. We determined that a cannabinoid compound, CBD, could specifically inhibit the expression of the Id-1 gene and, as a result, cancer cell proliferation and invasion in culture and tumor metastasis in vivo. In tumor-bearing mice, we observed significant anti-metastatic effects after daily treatment with CBD. Id-1 expression in tumor cells from lung foci was significantly down-regulated as well as Ki67, a marker of cell proliferation. Finally, CBD prolonged the survival of tumor-bearing mice even though the treatment was initiated after the establishment of metastases. Overall, our data suggest that Id proteins act as key regulators of tumor metastasis and suggest the use of Id genes as novel therapeutic targets.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5308. doi:1538-7445.AM2012-5308

Consensus on the role of human cytomegalovirus in glioblastoma

The human cytomegalovirus (HCMV) and glioma symposium was convened on April 17, 2011 in Washington, DC, and was attended by oncologists and virologists involved in studying the relationship between HCMV and gliomas. The purpose of the meeting was to reach a consensus on the role of HCMV in the pathology of gliomas and to clarify directions for future research. First, the group summarized data that describe how HCMV biology overlaps with the key pathways of cancer. Then, on the basis of published data and ongoing research, a consensus was reached that there is sufficient evidence to conclude that HCMV sequences and viral gene expression exist in most, if not all, malignant gliomas, that HCMV could modulate the malignant phenotype in glioblastomas by interacting with key signaling pathways; and that HCMV could serve as a novel target for a variety of therapeutic strategies. In summary, existing evidence supports an oncomodulatory role for HCMV in malignant gliomas, but future studies need to focus on determining the role of HCMV as a glioma-initiating event.

Human cytomegalovirus US28 found in glioblastoma promotes an invasive and angiogenic phenotype

Human cytomegalovirus (HCMV) infections are seen often in glioblastoma multiforme (GBM) tumors, but whether the virus contributes to GBM pathogenesis is unclear. In this study, we explored an oncogenic role for the G-protein-coupled receptor-like protein US28 encoded by HCMV that we found to be expressed widely in human GBMs. Immunohistochemical and reverse transcriptase PCR approaches established that US28 was expressed in approximately 60% of human GBM tissues and primary cultures examined. In either uninfected GBM cells or neural progenitor cells, thought to be the GBM precursor cells, HCMV infection or US28 overexpression was sufficient to promote secretion of biologically active VEGF and to activate multiple cellular kinases that promote glioma growth and invasion, including phosphorylated STAT3 (p-STAT3) and endothelial nitric oxide synthase (e-NOS). Consistent with these findings, US28 overexpression increased primary GBM cell invasion in Matrigel. Notably, this invasive phenotype was further enhanced by exposure to CCL5/RANTES, a US28 ligand, associated with poor patient outcome in GBM. Conversely, RNA interference-mediated knockdown of US28 in human glioma cells persistently infected with HCMV led to an inhibition in VEGF expression and glioma cell invasion in response to CCL5 stimulation. Analysis of clinical GBM specimens further revealed that US28 colocalized in situ with several markers of angiogenesis and inflammation, including VEGF, p-STAT3, COX2, and e-NOS. Taken together, our results indicate that US28 expression from HCMV contributes to GBM pathogenesis by inducing an invasive, angiogenic phenotype. In addition, these findings argue that US28-CCL5 paracrine signaling may contribute to glioma progression and suggest that targeting US28 may provide therapeutic benefits in GBM treatment.

Detection of human cytomegalovirus in normal and neoplastic breast epithelium

Introduction

Human cytomegalovirus (HCMV) establishes a persistent life-long infection, and can cause severe pathology in the fetus and the immunocompromised host[1]. Breast milk is the primary route of transmission in humans worldwide, and breast epithelium is thus a likely site of persistent infection and/or reactivation, though this phenomenon has not previously been demonstrated. Increasing evidence indicates HCMV infection can modulate signaling pathways associated with oncogenesis. We hypothesized that persistent HCMV infection occurs in normal adult breast epithelium and that persistent viral expression might be associated with normal and neoplastic ductal epithelium.

Methods

Surgical biopsy specimens of normal breast (n = 38) breast carcinoma (n = 39) and paired normal breast from breast cancer patients (n = 21) were obtained. Specimens were evaluated by immunohistochemistry, in situ hybridization, PCR and DNA sequencing for evidence of HCMV antigens and nucleic acids.

Results

We detected HCMV expression specifically in glandular epithelium in 17/27 (63%) of normal adult breast cases evaluated. In contrast, HCMV expression was evident in the neoplastic epithelium of 31/32 (97%) patients with ductal carcinoma in situ (DCIS) and infiltrating ductal carcinoma (IDC) cases evaluated (p = 0.0009).

Conclusions

These findings are the first to demonstrate that persistent HCMV infection occurs in breast epithelium in a significant percentage of normal adult females. HCMV expression was also evident in neoplastic breast epithelium in a high percentage of normal and neoplastic breast tissues obtained from breast cancer patients, raising the possibility that viral infection may be involved in the neoplastic process.

Is HCMV a tumor promoter?

Human cytomegalovirus (HCMV) is a beta-herpesvirus that causes persistent infection in humans and can cause severe disease in fetuses and immunocompromised individuals. Although HCMV is not currently causally implicated in human cancer, emerging evidence suggests that HCMV infection and expression may be specifically associated with human malignancies including malignant glioma, colon, and prostate cancer. In addition, multiple investigators have demonstrated that HCMV can dysregulate signaling pathways involved in initiation and promotion of malignancy, including tumor suppressor, mitogenic signaling, inflammatory, immune regulation, angiogenesis and invasion, and epigenetic mechanisms. This review highlights some of the recent evidence that HCMV might play a role in modulating the tumor microenvironment as well as in the initiation and promotion of tumor cells themselves.

Modulation of oncogenic phenotype in human glioma cells by cytomegalovirus IE1-mediated mitogenicity

Recent evidence indicates that human cytomegalovirus (HCMV) infection occurs in a high percentage of human malignant gliomas in vivo, as the HCMV immediate early-1 (IE1) protein is detected in >90% of these tumors. The HCMV IE1 protein is essential for viral infection and has potent trans-activating and oncomodulatory properties. To investigate a potential role of HCMV in glioma biology, we stably expressed the HCMV IE1 gene product in immortalized and malignant human glial cells. Here we show that stable IE1 expression can differentially affect the growth of human glioblastoma cells, resulting in either growth proliferation or arrest. IE1 expression led to dysregulation of phosphatidylinositol 3-kinase/AKT activity, Rb phosphorylation, and expression of the p53 family of proteins. In U87 and U118 glioblastoma cells, IE1 induced cellular proliferation paralleled by reduction in steady-state expression level of Rb and p53 family proteins (including p53, p63, or p73) and simultaneous induction of the phosphatidylinositol 3-kinase/AKT signaling pathway. In contrast, IE1 expression in LN229 and U251 glioblastoma cells and immortalized human astrocytes was associated with increased expression of p53 family proteins, accompanied by growth arrest or lack of enhanced proliferation. Moreover, IE1 promoted cell cycle entry and DNA synthesis of human glioma cells on both stable expression in tumor-derived cell lines as well as transient expression in primary glioblastoma cells. These findings indicate that HCMV IE1 can significantly affect important oncogenic signaling pathways in glioblastoma cells.

Human cytomegalovirus induces cellular tyrosine kinase signaling and promotes glioma cell invasiveness

Given our previous findings that human cytomegalovirus (HCMV) nucleic acids and proteins are expressed in human malignant glioma in vivo, we investigated cellular signaling events associated with HCMV infection of human glioma and astroglial cells. HCMV infection caused rapid activation of the phosphatidylinositol-3 kinase (PI-3K) effector AKT kinase in human astro-glial and fibroblast cells, and induced tyrosine phosphorylation of phospholipase Cgamma (PLCgamma). Co-immunoprecipitation experiments revealed association of the p85 regulatory subunit of PI-3K with a high-molecular weight protein phosphorylated on tyrosine, following short-term exposure to HCMV. In contrast to a previous report, we were unable to confirm the identity of this high-molecular weight protein as being the epidermal growth factor receptor (EGFR). Stimulation of glioma and fibroblast cell lines over-expressing EGFR with HCMV (whole virus) or soluble glycoprotein B did not induce tyrosine phosphorylation of the receptor, as did the genuine ligand, EGF. Furthermore, we found that expression levels of the human ErbB1-4 receptors were not rate-limiting for HCMV infection. Dispensability of EGFR function during early HCMV infection was substantiated by demonstration of viral immediate early gene expression in cells lacking the EGFR gene, indicating that HCMV may promote oncogenic signaling pathways independently of EGFR activation. Among non-receptor cellular kinases, HCMV infection induced phosphorylation of focal adhesion kinase (FAK) Tyr397, which is indispensable for integrin-mediated cell migration and invasion. HCMV-induced FAK activation was paralleled by increased extracellular matrix-dependent migration of human malignant glioma but not normal astro-glial cells, suggesting that HCMV can selectively augment glioma cell invasiveness.

Identification of IGF2 signaling through phosphoinositide-3-kinase regulatory subunit 3 as a growth-promoting axis in glioblastoma

Amplification or overexpression of growth factor receptors is a frequent occurrence in malignant gliomas. Using both expression profiling and in situ hybridization, we identified insulin-like growth factor 2 (IGF2) as a marker for a subset of glioblastomas (GBMs) that lack amplification or overexpression of EGF receptor. Among 165 primary high-grade astrocytomas, 13% of grade IV tumors and 2% of grade III tumors expressed IGF2 mRNA levels >50-fold the sample population median. IGF2-overexpressing tumors frequently displayed PTEN loss, were highly proliferative, exhibited strong staining for phospho-Akt, and belonged to a subclass of GBMs characterized by poor survival. Using a serum-free culture system, we discovered that IGF2 can substitute for EGF to support the growth of GBM-derived neurospheres. The growth-promoting effects of IGF2 were mediated by the insulin-like growth factor receptor 1 and phosphoinositide-3-kinase regulatory subunit 3 (PIK3R3), a regulatory subunit of phosphoinositide 3-kinase that shows genomic gains in some highly proliferative GBM cases. PIK3R3 knockdown inhibited IGF2-induced growth of GBM-derived neurospheres. The current results provide evidence that the IGF2-PIK3R3 signaling axis is involved in promoting the growth of a subclass of highly aggressive human GBMs that lack EGF receptor amplification. Our data underscore the importance of the phosphoinositide 3-kinase/Akt pathway for growth of high-grade gliomas and suggest that multiple molecular alterations that activate this signaling cascade may promote tumorigenesis. Further, these findings highlight the parallels between growth factors or receptors that are overexpressed in GBMs and those that support in vitro growth of tumor-derived stem-like cells.

Molecular subclasses of high-grade glioma predict prognosis, delineate a pattern of disease progression, and resemble stages in neurogenesis

Previously undescribed prognostic subclasses of high-grade astrocytoma are identified and discovered to resemble stages in neurogenesis. One tumor class displaying neuronal lineage markers shows longer survival, while two tumor classes enriched for neural stem cell markers display equally short survival. Poor prognosis subclasses exhibit markers either of proliferation or of angiogenesis and mesenchyme. Upon recurrence, tumors frequently shift toward the mesenchymal subclass. Chromosomal locations of genes distinguishing tumor subclass parallel DNA copy number differences between subclasses. Functional relevance of tumor subtype molecular signatures is suggested by the ability of cell line signatures to predict neurosphere growth. A robust two-gene prognostic model utilizing PTEN and DLL3 expression suggests that Akt and Notch signaling are hallmarks of poor prognosis versus better prognosis gliomas, respectively.

Up-regulation of vascular endothelial growth factor by membrane-type 1 matrix metalloproteinase stimulates human glioma xenograft growth and angiogenesis

Membrane-type (MT) 1 matrix metalloproteinase (MMP) is up-regulated in many tumor types and has been implicated in tumor progression and metastasis. MT1-MMP is critical for pericellular degradation of the extracellular matrix, thereby promoting tumor cell invasion and dissemination. To grow efficiently in vivo, tumor cells induce angiogenesis in both primary solid tumors and metastatic foci. The present study describes a functional link between the expression of MT1-MMP and vascular endothelial growth factor (VEGF) production in human glioma U251 xenografts in athymic mice. To investigate the effects of MT1-MMP on VEGF expression, U251 cells were stably transfected with MT1-MMP to generate the U-MT cell line overexpressing the enzyme. In vitro, the U-MT cells had an increased rate of proliferation and migration as well as the ability to activate the MMP-2 proenzyme and directionally remodel a three-dimensional collagen matrix. These findings suggested higher tumorigenicity of U-MT cells relative to the vector-control U-neo cells. In agreement with the in vitro data, U-MT xenografts in BALB/c nu/nu mice displayed markedly increased growth rates and elevated levels of angiogenesis. In contrast, U-neo cells formed small, minimally vascularized tumors. The elevated angiogenesis in U-MT xenografts was associated with an up-regulation of VEGF expression in tumor cells. In addition, U-MT cells in vitro secreted twice as much VEGF as the control cells. GM6001, a hydroxamate inhibitor of MMP activity, down-regulated the production of VEGF in U-MT cells to the levels observed in the U-neo control. Our results demonstrate that the enhanced tumorigenicity of glioma cells overexpressing MT1-MMP involves stimulation of angiogenesis through the up-regulation of VEGF production.

Reduced expression of connexin-43 and functional gap junction coupling in human gliomas

Gap junctions are an important means for intercellular communication during development, processes of tissue differentiation, and in maintenance of adult tissue homeostasis. We investigated the expression levels and distribution of connexin-43 (Cx-43), the most abundant astrocytic gap junction protein, in acutely isolated astrocytes and glioma cells from biopsy tissue obtained from patients diagnosed with glioblastoma multiforme (GBM), low-grade astrocytomas (LGAs), or mesial temporal lobe epilepsy. Western blot and immunohistochemical analyses indicated an inverse correlation between the amount of Cx-43 protein and tumor malignancy grade, as assessed by calculating tissue mitotic indexes (MI) obtained using anti-Ki-67 nuclear antigen staining. Samples from epilepsy patients had a low MI and were intensely positive for Cx-43 staining, while LGA tissue samples exhibited moderate staining for Cx-43 and average MI, and GBM biopsies showed significantly lower levels of Cx-43 and high MI. Functional coupling was assayed using fluorescence recovery after photobleach (FRAP). We found that cells from glioma cell lines and primary cultures of human astrocytes from GBM tissues displayed significantly lower degrees of gap junction intercellular communication (GJIC) as indicated by longer and less complete recovery from photobleaching. Mean recovery values were GBM 23.8% +/- 11.4%, LGA 49.4% +/- 47%, and nontumor astrocytes 67.2% +/- 8.4%. Western blot analysis of several human glioma cell lines and tissue biopsies showed variable expression levels of Cx-43, which correlated negatively with the extent of recovery in the same samples. Taken together, our findings suggest that high-grade brain tumors show reduced intercellular communication and a decrease in connexin-43 protein levels.

Modulation of glioma cell migration and invasion using Cl(-) and K(+) ion channel blockers

Human malignant gliomas are highly invasive tumors. Mechanisms that allow glioma cells to disseminate, migrating through the narrow extracellular brain spaces are poorly understood. We recently demonstrated expression of large voltage-dependent chloride (Cl(-)) currents, selectively expressed by human glioma cells in vitro and in situ (Ullrich et al., 1998). Currents are sensitive to several Cl(-) channel blockers, including chlorotoxin (Ctx), (Ullrich and Sontheimer; 1996; Ullrich et al; 1996), tetraethylammonium chloride (TEA), and tamoxifen (Ransom and Sontheimer, 1998). Using Transwell migration assays, we show that blockade of glioma Cl(-) channels specifically inhibits tumor cell migration in a dose-dependent manner. Ctx (5 microM), tamoxifen (10 microM), and TEA (1 mM) also prevented invasion of human glioma cells into fetal rat brain aggregates, used as an in vitro model to assess tumor invasiveness. Anion replacement studies suggest that permeation of chloride ions through glioma chloride channel is obligatory for cell migration. Osmotically induced cell swelling and subsequent regulatory volume decrease (RVD) in cultured glioma cells were reversibly prevented by 1 mM TEA, 10 microM tamoxifen, and irreversibly blocked by 5 microM Ctx added to the hypotonic media. Cl(-) fluxes associated with adaptive shape changes elicited by cell swelling and RVD in glioma cells were inhibited by 5 microM Ctx, 10 microM tamoxifen, and 1 mM TEA, as determined using the Cl(-)-sensitive fluorescent dye 6-methoxy-N-ethylquinolinium iodide. Collectively, these data suggest that chloride channels in glioma cells may enable tumor invasiveness, presumably by facilitating cell shape and cell volume changes that are more conducive to migration and invasion.

Glioma migration can be blocked by nontoxic inhibitors of myosin II

Anaplastic gliomas are infiltrative tumors, and their ability to migrate through normal brain contributes to their highly malignant behavior. Invasion of brain requires cell motility, which in turn depends on the activity of the cytoskeleton. A cytoskeletal component central to this process is myosin II, the cytoplasmic analogue of smooth and skeletal muscle myosin. Myosin II activity is regulated by the enzyme myosin light chain kinase, which activates myosin II by phosphorylating it on its regulatory light chain. We have investigated the role of myosin II in glioma motility and invasiveness by examining the effects of two inhibitors of myosin light chain kinase, ML7 and KT5926. Both drugs are potent inhibitors of both glioma motility, as measured by a scrape motility assay, and an in vitro haptotaxis assay. The inhibition of in vitro haptotaxis follows the dose-response relationship expected for competitive inhibition of myosin light chain kinase by these drugs and is seen at drug concentrations that are nontoxic. These results highlight the important role that myosin II contributes to glioma invasiveness and suggest that it may serve as a target in future strategies at blocking invasion by these tumors.

Use of chlorotoxin for targeting of primary brain tumors

Gliomas are primary brain tumors that arise from differentiated glial cells through a poorly understood malignant transformation. Although glioma cells retain some genetic and antigenic features common to glial cells, they show a remarkable degree of antigenic heterogeneity and variable mutations in their genome. Glioma cells have recently been shown to express a glioma-specific chloride ion channel (GCC) that is sensitive to chlorotoxin (CTX), a small peptide purified from Leiurus quinquestriatus scorpion venom [N. Ullrich et al, Neuroreport, 7: 1020-1024, 1996; and N. Ullrich and H. Sontheimer, Am. J. Physiol. (Cell Physiol.), 270: C1511-C1521, 1996]. Using native and recombinant 125I-labeled CTX, we show that toxin binding to glioma cells is specific and involves high affinity [dissociation constant (Kd)=4.2 nM] and low affinity (Kd=660 nml) binding sites. In radioreceptor assays, 125I-labeled CTX binds to a protein with Mr=72,000, presumably GCC or a receptor that modulates GCC activity. In vivo targeting and biodistribution experiments were obtained using 125I- and (131)I-labeled CTX injected into severe combined immunodeficient mice bearing xenografted gliomas. CTX selectively accumulated in the brain of tumor-bearing mice with calculated brain: muscle ratios of 36.4% of injected dose/g (ID/g), as compared to 12.4% ID/g in control animals. In the tumor-bearing severe combined immunodeficient mice, the vast majority of the brain-associated radioactivity was localized within the tumor (tumor:muscle ratio, 39.13% ID/g; contralateral brain:muscle ratio, 6.68%ID/g). Moreover, (131)I-labeled CTX distribution, visualized through in vivo imaging by gamma ray camera scans, demonstrates specific and persistent intratumoral localization of the radioactive ligand. Immunohistochemical studies using biotinylated and fluorescently tagged CTX show highly selective staining of glioma cells in vitro, in situ, and in sections of patient biopsies. Comparison tissues including normal human brain, kidney, and colon were consistently negative for CTX immunostaining. These data suggest that CTX and CTX-conjugated molecules may serve as glioma-specific markers with diagnostic and therapeutic potential.

Paracrine expression of a native soluble vascular endothelial growth factor receptor inhibits tumor growth, metastasis, and mortality rate

Vascular endothelial growth factor (VEGF) is a potent and selective vascular endothelial cell mitogen and angiogenic factor. VEGF expression is elevated in a wide variety of solid tumors and is thought to support their growth by enhancing tumor neovascularization. To block VEGF-dependent angiogenesis, tumor cells were transfected with cDNA encoding the native soluble FLT-1 (sFLT-1) truncated VEGF receptor which can function both by sequestering VEGF and, in a dominant negative fashion, by forming inactive heterodimers with membrane-spanning VEGF receptors. Transient transfection of HT-1080 human fibrosarcoma cells with a gene encoding sFLT-1 significantly inhibited their implantation and growth in the lungs of nude mice following i.v. injection and their growth as nodules from cells injected s.c. High sFLT-1 expressing stably transfected HT-1080 clones grew even slower as s.c. tumors. Finally, survival was significantly prolonged in mice injected intracranially with human glioblastoma cells stably transfected with the sflt-1 gene. The ability of sFLT-1 protein to inhibit tumor growth is presumably attributable to its paracrine inhibition of tumor angiogenesis in vivo, since it did not affect tumor cell mitogenesis in vitro. These results not only support VEGF receptors as antiangiogenic targets but also demonstrate that sflt-1 gene therapy might be a feasible approach for inhibiting tumor angiogenesis and growth.

In vitro and in vivo gene delivery mediated by a synthetic polycationic amino polymer

A synthetic polyamino polymer with a glucose backbone was used for gene transfer in vitro and in vivo. Gene transfer in vitro to various human carcinoma cell lines was achieved with an efficiency superior to a commercially available cationic liposome preparation. The polymer was resistant to inhibition by serum, which allowed for efficient gene transfer in vivo. Direct Intracranial tumor injection using this reagent resulted in reporter gene expression levels comparable to those achieved by a recombinant adenoviral vector. Thus, this compound represents a new class of agent that may have broad utility for gene transfer and gene therapy applications.

Evaluation of genetically engineered herpes simplex viruses as oncolytic agents for human malignant brain tumors

Earlier studies have shown that genetically engineered herpes simplex viruses (e.g., HSV-1) are effective in killing malignant tumor cells both in vitro and in various murine tumor models. This report focuses on a panel of five genetically engineered viral mutants of the gamma(1)34.5 gene, which was shown previously to cause reduction in viral replication and associated neurovirulence of HSV. These include R3616, which has both copies of gamma(1)34.5 deleted, R4009, which has a stop codon inserted after codon 28 in both copies of the gamma(1)34.5 gene, R849, which contains a lacZ gene inserted in place of the gamma(1)34.5, R908, which lacks 41 codons in frame after codon 72 of the gamma(1)34.5, and R939, which carries a stop codon precluding the translation of the COOH-terminal domain of the gamma(1)34.5 gene. We report the following: (a) all five mutant HSVs were avirulent in experimental animals but were cytotoxic for human tumor cells in vitro and in vivo; (b) the gamma(1)34.5- HSV replicated in human glioma cells almost as efficiently as wild-type HSV-1(F) based on replication assays, in situ hybridization for viral DNA, and expression of infected cell protein 27; (c) capacity of mutant HSVs to kill human cells derived from glioblastoma multiforme (CH-235MG, D-37MG, D-54MG, D-65MG, U-251MG, U-373MG, and SK-MG-1), anaplastic astrocytoma (Hs-683), anaplastic glioma (U-87MG and U-138MG), gliosarcoma (D-32GS), or normal human astrocytes demonstrated that glioma cells varied in their susceptibility to HSV-mediated cytotoxicity and that cultured astrocytes were two to three orders of magnitude less susceptible to killing than were malignant glia; and (d) scid mice, which received 0.5 or 5 x 10(6) plaque-forming units of R4009, either were coinoculated at the time of intracranial transplantation with 106 U251MG or D-54MG human glioma cells or received the cells intratumorally 5 days after tumor induction and experienced significant increases in median survivals, with no histopathological indication of an infectious encephalitic process. Genetically engineered gamma(1)34.5- HSV mutants appear to be a potentially safe biotherapeutic agent for experimental treatment of uniformly fatal malignant brain tumors.