Glioblastoma Cancer Stem Cells Research Articles

BI-24 * COLLAGEN PLAYS A ROLE IN GLIOBLASTOMA TUMOR INVASION AND PATIENT SURVIVAL

BACKGROUND: Glioblastoma (GBM) is the most malignant brain cancer. Collagen is minimally expressed in normal brain parenchyma; however, previous reports show upregulated collagen gene expression in GBM. We perform the first direct GBM collagen visualization, identify clinically relevant collagen signatures in focal and invasive GBMs and link them to differential patient survival. METHODS: Customized second harmonic generation (SHG) multiphoton workstation with excitation wavelength tuned to 890nm and a 445± 25nm bandpass emission filter was used to detect collagen in a clinically-annotated human GBM tissue microarray (TMA) for 111 patients. Human GBM cancer stem cell lines that form focal or invasive xenografts were implanted into mice brains. Symptomatic mice with verified xenografts were euthanized, brains excised, and stained with picrosirius red. Quantitative characterization of collagen fibers in xenografts and TMA images was performed with custom software. RESULTS: Collagen was directly visualized in GBMs with SHG and picrosirius red. In focal GBM xenografts, collagen was observed at tumor-brain boundaries, appearing to encapsulate the tumors. For invasive GBM xenografts, collagen was intercalated with tumor cells. Quantitative collagen analysis showed significant differences for mean angle between fibers for focal (60.3856 ± 2.2113) and invasive (70.2529 ± 1.6211) GBM xenografts. GBM TMA specimens were segregated into two collagen groups: fibrillar and immature. Patients with fibrillar GBM collagen had a statistically significantly better median survival (69.6 weeks) compared to immature GBM collagen patients (30.4 weeks). The mean angle between fibers was significantly different for GBMs with fibrillar (84.37 ± 7.298) versus immature (113.2 ± 11.60) collagen. CONCLUSIONS: We demonstrate that collagen can be directly visualized in GBMs, and is different in focal vs. invasive tumors. Our data suggest collagen is a potential survival marker: patients with fibrillar collagen have improved survival. Therefore, we hypothesize that collagen may influence tumor cell invasion by acting as a barrier, and collagen disruption may promote tumor invasion.

Emerging treatment strategies for glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the deadliest form of brain tumor with a more than 90% 5-year mortality. GBM has a paltry median survival of 12.6 months attributed to the unique treatment limitations such as the high average age of onset, tumor location, and poor current understandings of the tumor pathophysiology. The resection techniques, chemotherapic strategies, and radiation therapy currently used to treat GBM have slowly evolved, but the improvements have not translated to marked increases in patient survival. Here, we will discuss the recent progress in our understanding of GBM pathophysiology, and the diagnostic techniques and treatment options. The discussion will include biomarkers, tumor imaging, novel therapies such as monoclonal antibodies and small-molecule inhibitors, and the heterogeneity resulting from the GBM cancer stem cell population.

Abstract 3795: Cabozantinib affects multiple signaling pathways in glioblastoma and is effective in a subset of xenograft tumors

Abstract Background: Glioblastoma (GBM) is the most common and aggressive form of brain tumor characterized by poor prognosis and high recurrence rate. Several new targeted agents are being considered for the adjuvant treatment of GBMs. Cabozantinib, a multi-kinase currently in clinical trials for several malignancies, including glioblastoma, targets c-Met and VEGFR2 receptors, as well as Ret, Kit, Flt-1/3/4, Tie2, and AXL. Our goal is to first evaluate sensitivity and molecular response of patient-derived GBM cancer stem cells (CSCs) to XL184 in vitro. Anti-tumor efficacy of cabozantinib as a single agent and in combination with the DNA-alkylating agent temozolomide (TMZ) in orthotopic xenografts was then evaluated. Methods: Neurospheres enriched in CSCs were cultured from resected GBM tumors. Sensitivity to cabozantinib was determined in vitro. Cells were treated (IC40) in triplicate, and cell lysates were analyzed by reverse phase protein microarrays. GBM CSCs were implanted intracranially into nude mice. Cabozantinib was administered by oral gavage at a dose of 60mg/kg for 4 weeks (5 days/week) as a single agent or in combination with 40mg/kg TMZ. Tumor growth and response to treatment were monitored by non-invasive in vivo biolumiescent imaging (BLI) using the Xenogen IVIS System (Caliper Life Sciences), and overall survival. Results: Sensitivity to cabozantinib treatment varied for the different GBM CSCs. From 70 proteins and phosphoproteins measured, 29 distributed among several signaling pathways were significantly altered after treatment in both resistant and sensitive GBM CSCs. Cabozantinib single agent treatment reduced GBM tumor growth and increased mouse survival in two xenograft lines. Cabozantinib monotherapy reduced tumor size, as measured by BLI, but had no significant effect on overall survival for another xenograft line, however, the combination treatment resulted in sensitization of these xenografts to TMZ treatment. Conclusion: The use of multi-kinase inhibitors is a promising strategy for GBMs, and given the range of responses, identifying predictive biomarkers, though challenging, will be invaluable for patient stratification. Citation Format: Ana C. deCarvalho, Kimberly Arnold, Claudius Mueller, Emanuel F. Petricoin, Laila M. Poisson, Tom Mikkelsen. Cabozantinib affects multiple signaling pathways in glioblastoma and is effective in a subset of xenograft tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3795. doi:10.1158/1538-7445.AM2014-3795

Abstract CT404: Phase I/II study of VAL-083 in patients with recurrent glioblastoma multiforme

Abstract Median survival for patients with recurrent glioblastoma multiforme (GBM) is less than 6 months. Front-line systemic therapy is temozolomide, but chemo-resistance due to O6-methylguanine-DNA-methyltransferase (MGMT) activity has been implicated in poor outcomes. VAL-083 is a structurally unique bi-functional DNA alkylating small molecule drug that crosses the blood-brain barrier and accumulates in brain tumor tissue. Previous human clinical studies by several investigators have suggested that VAL-083 has anti-tumor activity against a broad range of tumor types including GBM. In preclinical in vitro studies, VAL-083 demonstrated activity in a wide range of cancer cell lines, including pediatric and adult GBM cell lines and GBM cancer stem cells. Notably, due to crosslink formation on N7 of guanine, VAL-083 overcomes chemo-resistance to MGMT in vitro. In light of extensive safety data from several clinical trials and promising efficacy signals in CNS tumors, DelMar initiated a new clinical study to determine the safety, tolerability, pharmacokinetics, anti-tumor activity in patients with recurrent GBM. This is an open-label, single-arm Phase I/II dose-escalation study in patients with histologically-confirmed initial diagnosis of malignant GBM. The study utilizes a 3+3 dose-escalation design. Patients receive VAL-083 i.v. on days 1, 2, and 3 of a 21 day cycle. GBM patients have previously been treated with surgery and/or radiation, if appropriate, and must have failed both bevacizumab and temozolomide, unless contraindicated. In the ongoing trial, cohorts 1 through 4 (10 mg/m2) have completed the trial successfully with no drug-related serious adverse events (SAEs), and maximum tolerated dose (MTD) was not yet reached. Enrollment for Cohort 5 (20 mg/m2) has been initiated. Pharmacokinetic analyses show dose-dependent increase in exposure with a short 1-2 hour plasma half-life and a Cmax of <200 ng/ml at 10 mg/m2. Historical data suggests a long half-life in the cerebrospinal fluid (CSF) (>20 hours) with preferential accumulation to brain tumor tissue. MGMT status of patients and drug concentration in the CSF are being evaluated when possible. ClinicalTrials.gov Identifier: NCT01478178 Citation Format: Kent C. Shih, Manish R. Patel, Jeffrey Bacha, Dennis M. Brown, William J. Garner, Anne Steino, Richard S. Schwartz, Sarath Kanekal, Mike Li, Lorena M. Lopez, Howard A. Burris. Phase I/II study of VAL-083 in patients with recurrent glioblastoma multiforme. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT404. doi:10.1158/1538-7445.AM2014-CT404

Abstract 3025: HER2/Stat3 signaling mediated radioresistance in U87 glioma cancer cells through suppressed apoptosis and enhanced glycolysis

Abstract GBM is the most common and aggressive malignant primary brain tumor, and the prognosis for GBM patients remains poor. Radiotherapy continues to play a central role in the management of brain tumors. Even though the advances of radiotherapy strategies and techniques, frequent failure of radiotherapy made GBM a disease difficult to be treated. GBM cancer stem cells (CSCs) are reported to be responsible for resistance to chemo- and radiotherapy, and chemotherapy and radiotherapy resistant GBM CSCs have been isolated from GBM. However, the mechanisms of radioresistance of glioma cells are still elucidative. In this study, we investigated the role of HER2-Stat3 signaling pathway in radioresistance using human glioma cell line U87. We found that long-term therapeutic dose of fragmented irradiation induces repopulation of human glioma U87 cells with increased number of CD133+/HER2+ stem-like cells. FIR-surviving CD133+/HER2+ U87 cells have coactivation of HER2 and Stat3 and increased cell proliferation and invasion abilities. More importantly, we found that U87-FIR cells have lower level of mitochondria metabolism and ROS level, and higher mitochondrial membrane potential, while 5Gy single dose radiation induces increased mitochondria function. Furthermore, U87 cell injection derived xenograph tumor also has increased mitochondrial membrane potential and decreased mitochondria function after radiation. These results suggest that the radioresistance of GBM CSCs possibly due to the suppressed apoptosis and enhanced glycolysis mediated by HER2/STAT3 pathway. Citation Format: Lili Qin, Ming Fan, Jian Jian Li. HER2/Stat3 signaling mediated radioresistance in U87 glioma cancer cells through suppressed apoptosis and enhanced glycolysis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3025. doi:10.1158/1538-7445.AM2014-3025

Abstract 1927: Tumor suppressor PTEN regulates cancer stem cells of glioblastoma multiforme: identification of signaling pathways as targets of therapy

Abstract Glioblastoma Multiforme (GBM), a WHO defined grade IV astrocytoma, is a uniformly fatal CNS malignancy. The high rate of recurrence is attributed to the presence of its untreatable cancer stem cells (CSC). Phosphatase and tensin homologue on chromosome 10 (PTEN), a tumor suppressor is a central negative regulator of PI3K/AKT signaling axis that controls multiple cellular functions, including cell growth, survival and proliferation. Recent evidence suggests that PTEN loss is associated with increased CSC in GBM. Furthermore, downstream from PTEN/PI3K/AKT is mTOR, an atypical serine threonine kinase that exists in two multiprotein complexes (mTORC1 and mTORC2), which regulates growth and dissemination of GBM. The molecular mechanism involved in regulation of CSC by PTEN and its interacting pathways remains elusive. The aim of this study is to elucidate the role of PTEN in regulation and maintenance of CSC in GBM, and define the potential downstream targets of therapy. In order to achieve our goals, we evaluated the presence of activated AKT/mTOR, and stem cell marker nestin in surgically resected GBM tumors. GBM cell line U87 (PTEN mutated) was transfected with PTEN plasmids (wild type and 3 phosphorylated mutants) to evaluate its role in CSC self-renewal. Pharmacological treatments included an inhibitor of EGFR, gefitinib (Iressa), with or without inhibitors of PI3K (LY294002; LY) or inhibitors of mTORC1 (rapamycin) or mTORC1/2 (PP242). Expression of mTOR and stem cell markers were assessed using IHC or IF analysis, and protein expression was determined via Western Blotting. Functional analysis included self-renewal, drug withdrawal, differentiation, proliferation and migration. Results demonstrated that a significant number of GBM tumors expressed stem cell markers nestin as well as pAKT and pmTOR. Wild type PTEN expressing CSC had decreased self-renewal compared to PTEN expressing mutant CSCs. PI3K inhibitor, LY, with gefitinib was most effective in suppressing neurosphere formation. Rebound following withdrawal of inhibitors showed a significant upregulation in self-renewal of CSC in cells treated with gefitinib and either LY or PP242. These combinations also significantly suppressed CSC proliferation. mTOR suppression altered the expression of stem cell markers nestin and SOX2. In conclusion, the findings of this study demonstrate that PTEN/PI3K/mTOR signaling forms a complex network that regulates and maintains GBM CSC; this also underscores the combined suppression of interacting signaling pathways, such as EGFR, in targeting GBM CSC. Note: This abstract was not presented at the meeting. Citation Format: Michael LaBagnara, Keith Lambert, Sudeepta Sridhara, Michael Tobias, Raj Murali, Meena Jhanwar-Uniyal. Tumor suppressor PTEN regulates cancer stem cells of glioblastoma multiforme: identification of signaling pathways as targets of therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1927. doi:10.1158/1538-7445.AM2014-1927

Abstract 2267: Sulforaphane depresses proliferation and induces cell death in glioblastoma multiforme (GBM) cells, GBM stem cell-like spheroids, and tumor xenografts through modulation of multiple cell signaling pathways

Abstract Glioblastoma multiforme (GBM) comprises the largest group of brain tumors which are drug resistant and respond very poorly to the current therapies. In this study, we used sulforaphane (SFN), a multi-targeting agent with cancer preventive and anti-cancer activities and showed that it targets GBM established cell lines, early primary cultures, and CD133+ GBM stem cells as well as in GBM stem-like spheroids. SFN at 5-50 μM triggered significant inhibition of cell survival and induced apoptotic cell death in GBM cells and CD133+ stem cells isolated from four GBM cell lines. SFN induced apoptosis in U87MG cells was associated with caspase-7 activation. Moreover, SFN triggered formation of intracellular reactive oxygen species (ROS) and when the cells were pre-treated with 10 mM N-acetyl cysteine (NAC), ROS production and cell survival in cells treated with 5-10 μM were similar to the control untreated U87MG cells, revealing that SFN-triggered cell death is ROS-dependent. Moreover, SFN-generated ROS in U87MG cells were formed at the Mitochondrial Respiratory Chain (MRC) level. SFN also increased expression of the TRAIL receptor DR5 in GBM cells, U87MG and SF767 cells by 24 h post-exposure. Moreover, as revealed by comet assay, SFN increased single- and double-strand DNA breaks in GBM. Compared to untreated control cells, a significantly higher amount of γ-H2AX foci and as consequence higher number of DNA double-strand breaks (DSBs) breaks were observed in the SFN-treated sample. In vivo studies, using NOD/SCID mice revealed that SFN administration via oral gavage at 100 mg/kg for 3 cycles significantly decreases the growth of ectopic xenografts established from the early passage primary cultures of GBM10. Our results show that SFN robustly inhibits growth of GBM cells in vitro and in vivo and induces cell death in established cell cultures, early passage primary cultures, as well as it is effective in eliminating GBM cancer stem cells, which play a major role in drug resistance and disease recurrence. These results suggest that use of SFN alone or in combination with other agents, may potentially improve survival of brain tumor patients. Citation Format: Khadijeh Bijangi-Vishehsaraei, Mohammad R. Saadatzadeh, Haiyan Wang, Malgorzata M. Kamocka, Wenjing Cai, Aaron A. Cohen-Gadol, Stacey L. Halum, Karen E. Pollok, Jann N. Sarkaria, Ahmad R. Safa. Sulforaphane depresses proliferation and induces cell death in glioblastoma multiforme (GBM) cells, GBM stem cell-like spheroids, and tumor xenografts through modulation of multiple cell signaling pathways. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2267. doi:10.1158/1538-7445.AM2014-2267

Erratum to: Phenotypic and functional characterization of Glioblastoma cancer stem cells identified through 5-aminolevulinic acid-assisted surgery

Erratum to: Phenotypic and functional characterization of Glioblastoma cancer stem cells identified through 5-aminolevulinic acid-assisted surgery

Abrogation of radioresistance in glioblastoma stem-like cells by inhibition of ATM kinase

Resistance to radiotherapy in glioblastoma (GBM) is an important clinical problem and several authors have attributed this to a subpopulation of GBM cancer stem cells (CSCs) which may be responsible for tumour recurrence following treatment. It is hypothesised that GBM CSCs exhibit upregulated DNA damage responses and are resistant to radiation but the current literature is conflicting. We investigated radioresistance of primary GBM cells grown in stem cell conditions (CSC) compared to paired differentiated tumour cell populations and explored the radiosensitising effects of the ATM inhibitor KU-55933.We report that GBM CSCs are radioresistant compared to paired differentiated tumour cells as measured by clonogenic assay. GBM CSC's display upregulated phosphorylated DNA damage response proteins and enhanced activation of the G2/M checkpoint following irradiation and repair DNA double strand breaks (DSBs) more efficiently than their differentiated tumour cell counterparts following radiation.Inhibition of ATM kinase by KU-55933 produced potent radiosensitisation of GBM CSCs (sensitiser enhancement ratios 2.6–3.5) and effectively abrogated the enhanced DSB repair proficiency observed in GBM CSCs at 24 h post irradiation. G2/M checkpoint activation was reduced but not abolished by KU-55933 in GBM CSCs.ATM kinase inhibition overcomes radioresistance of GBM CSCs and, in combination with conventional therapy, has potential to improve outcomes for patients with GBM.

Isolation of cancer stem cells from three human glioblastoma cell lines: characterization of two selected clones.

Cancer stem cells (CSC) were isolated via a non-adherent neurosphere assay from three glioma cell lines: LI, U87, and U373. Using a clonal assay, two clones (D2 and F11) were selected from spheres derived from LI cells and were characterized for the: expression of stem cell markers (CD133, Nestin, Musashi-1 and Sox2); proliferation; differentiation capability (determined by the expression of GalC, βIII-Tubulin and GFAP); Ca2+ signaling and tumorigenicity in nude mice. Both D2 and F11 clones expressed higher levels of all stem cell markers with respect to the parental cell line. Clones grew more slowly than LI cells with a two-fold increase in duplication time. Markers of differentiation (βIII-Tubulin and GFAP) were expressed at high levels in both LI cells and in neurospheres. The expression of Nestin, Sox2, and βIII-Tubulin was down-regulated in D2 and F11 when cultured in serum-containing medium, whereas Musashi-1 was increased. In this condition, duplication time of D2 and F11 increased without reaching that of LI cells. D2, F11 and parental cells did not express voltage-dependent Ca2+-channels but they exhibited increased intracellular Ca2+ levels in response to ATP. These Ca2+ signals were larger in LI cells and in spheres cultured in serum-containing medium, while they were smaller in serum-free medium. The ATP treatment did not affect cell proliferation. Both D2 and F11 induced the appearance of tumors when ortotopically injected in athymic nude mice at a density 50-fold lower than that of LI cells. All these data indicate that both clones have characteristics of CSC and share the same stemness properties. The findings regarding the expression of differentiation markers and Ca2+-channels show that both clones are unable to reach the terminal differentiation. Both D2 and F11 might represent a good model to improve the knowledge on CSC in glioblastoma and to identify new therapeutic approaches.

Proliferation and enrichment of CD133+ glioblastoma cancer stem cells on 3D chitosan-alginate scaffolds

Emerging evidence implicates cancer stem cells (CSCs) as primary determinants of the clinical behavior of human cancers, representing an ideal target for next-generation anti-cancer therapies. However CSCs are difficult to propagate in vitro, severely limiting the study of CSC biology and drug development. Here we report that growing cells from glioblastoma (GBM) cell lines on three dimensional (3D) porous chitosan-alginate (CA) scaffolds dramatically promotes the proliferation and enrichment of cells possessing the hallmarks of CSCs. CA scaffold-grown cells were found more tumorigenic in nude mouse xenografts than cells grown from monolayers. Growing in CA scaffolds rapidly promoted expression of genes involved in the epithelial-to-mesenchymal transition that has been implicated in the genesis of CSCs. Our results indicate that CA scaffolds have utility as a simple and inexpensive means to cultivate CSCs in vitro in support of studies to understand CSC biology and develop more effective anti-cancer therapies.

Systemic approaches identify a garlic-derived chemical, Z-ajoene, as a glioblastoma multiforme cancer stem cell-specific targeting agent.

Glioblastoma multiforme (GBM) is one of the most common brain malignancies and has a very poor prognosis. Recent evidence suggests that the presence of cancer stem cells (CSC) in GBM and the rare CSC subpopulation that is resistant to chemotherapy may be responsible for the treatment failure and unfavorable prognosis of GBM. A garlic-derived compound, Z-ajoene, has shown a range of biological activities, including anti-proliferative effects on several cancers. Here, we demonstrated for the first time that Z-ajoene specifically inhibits the growth of the GBM CSC population. CSC sphere-forming inhibition was achieved at a concentration that did not exhibit a cytotoxic effect in regular cell culture conditions. The specificity of this inhibitory effect on the CSC population was confirmed by detecting CSC cell surface marker CD133 expression and biochemical marker ALDH activity. In addition, stem cell-related mRNA profiling and real-time PCR revealed the differential expression of CSC-specific genes, including Notch, Wnt, and Hedgehog, upon treatment with Z-ajoene. A proteomic approach, i.e., reverse-phase protein array (RPPA) and Western blot analysis, showed decreased SMAD4, p-AKT, 14.3.3 and FOXO3A expression. The protein interaction map (http://string-db.org/) of the identified molecules suggested that the AKT, ERK/p38 and TGFβ signaling pathways are key mediators of Z-ajoene's action, which affects the transcriptional network that includes FOXO3A. These biological and bioinformatic analyses collectively demonstrate that Z-ajoene is a potential candidate for the treatment of GBM by specifically targeting GBM CSCs. We also show how this systemic approach strengthens the identification of new therapeutic agents that target CSCs.

352: Modulation of canonical WNT signaling in combination with temozolomide inhibits growth of glioblastoma cancer stem cells in vitro

352: Modulation of canonical WNT signaling in combination with temozolomide inhibits growth of glioblastoma cancer stem cells in vitro

Preclinical Characterization of Signal Transducer and Activator of Transcription 3 Small Molecule Inhibitors for Primary and Metastatic Brain Cancer Therapy

Signal transducer and activator of transcription 3 (STAT3) has been implicated as a hub for multiple oncogenic pathways. The constitutive activation of STAT3 is present in several cancers, including gliomas (GBMs), and is associated with poor therapeutic responses. Phosphorylation of STAT3 triggers its dimerization and nuclear transport, where it promotes the transcription of genes that stimulate tumor growth. In light of this role, inhibitors of the STAT3 pathway are attractive therapeutic targets for cancer. To this end, we evaluated the STAT3-inhibitory activities of three compounds (CPA-7 [trichloronitritodiammineplatinum(IV)], WP1066 [(S,E)-3-(6-bromopyridin-2-yl)-2-cyano-N-(1-phenylethyl)acrylamide, C17H14BrN3O], and ML116 [4-benzyl-1-{thieno[2,3-d]pyrimidin-4-yl}piperidine, C18H19N3S]) in cultured rodent and human glioma cells, including GBM cancer stem cells. Our results demonstrate a potent induction of growth arrest in GBM cells after drug treatment with a concomitant induction of cell death. Although these compounds were effective at inhibiting STAT3 phosphorylation, they also displayed variable dose-dependent inhibition of STAT1, STAT5, and nuclear factor κ light-chain enhancer of activated B cells. The therapeutic efficacy of these compounds was further evaluated in peripheral and intracranial mouse tumor models. Whereas CPA-7 elicited regression of peripheral tumors, both melanoma and GBM, its efficacy was not evident when the tumors were implanted within the brain. Our data suggest poor permeability of this compound to tumors located within the central nervous system. WP1066 and ML116 exhibited poor in vivo efficacy. In summary, CPA-7 constitutes a powerful anticancer agent in models of peripheral solid cancers. Our data strongly support further development of CPA-7-derived compounds with increased permeability to enhance their efficacy in primary and metastatic brain tumors.

Expression of the transcription factor Hes3 in the mouse and human ocular surface, and in pterygium

Purpose: In this work we examined the presence of the neural stem cell biomarker Hairy and Enhancer of Split 3 (Hes3) in the anterior eye segment and in the aberrant growth condition of the conjunctiva pterygium. Further, we studied the response of Hes3 to irradiation.Materials and methods: Adult mouse and human corneoscleral junction and conjunctiva, as well as human pterygium were prepared for immunohistochemical detection of Hes3 and other markers. Total body irradiation was used to study the changes in the pattern of Hes3 expression.Results: The adult rodent and human eye as well as pterygium, contain a population of cells expressing Hes3. In the human eye, Hes3-expressing (Hes3+) cells are found predominantly in the subconjunctival space spanning over the limbus where they physically associate with blood vessels. The cytoarchitecture of Hes3 + cells is similar to those previously observed in the adult central nervous system. Furthermore, irradiation reduces the number of Hes3 + cells in the subconjunctival space. In contrast, irradiation strongly promotes the nuclear localization of Hes3 in the ciliary body epithelium.Conclusions: Our results suggest that a recently identified signal transduction pathway that regulates neural stem cells and glioblastoma cancer stem cells also operates in the ocular surface, ciliary body, and in pterygium.

Phenotypic and functional characterization of Glioblastoma cancer stem cells identified trough 5-aminolevulinic acid-assisted surgery

5-aminolevulinic acid (5-ALA) introduction in the surgical management of Glioblastoma (GBM) enables the intra-operatively identification of cancer cells in the mass by means of fluorescence. Here, we analyzed the phenotype of GBM cells isolated from distinct tumour areas determined by 5-ALA (tumour core, 5-ALA intense and vague layers) and the potency of 5-ALA labelling in identifying GBM cells and cancer stem cells (CSCs) in the mass. 5-ALA identified distinct layers in the mass, with less differentiated cells residing in the core of the tumour. 5-ALA was able to stain up to 68.5% of CD133(+) cells in the 5-ALA intense layer and, although 5-ALA(+) cells retrieved from different tumour areas contained a similar proportion of CD133(+) cells (range 27.5-35.6%), those from the vague layer displayed the lowest ability to self-renew. In conclusion, our data demonstrate that a substantial amount of GBM cells and CSCs in the mass are able to avoid 5-ALA labelling and support the presence of heterogenic CSC populations in the GBM mass.

PDGF receptor alpha inhibition induces apoptosis in glioblastoma cancer stem cells refractory to anti-Notch and anti-EGFR treatment.

BackgroundCancer stem cells (CSC) represent a rare fraction of cancer cells characterized by resistance to chemotherapy and radiation, therefore nowadays there is great need to develop new targeted therapies for brain tumors and our study aim to target pivotal transmembrane receptors such as Notch, EGFR and PDGFR, which are already under investigation in clinical trials setting for the treatment of Glioblastoma Multiforme (GBM).MethodsMTS assay was performed to evaluate cells response to pharmacological treatments. Quantitative RT-PCR and Western blots were performed to state the expression of Notch1, EGFR and PDGFRα/β and the biological effects exerted by either single or combined targeted therapy in GBM CSC. GBM CSC invasive ability was tested in vitro in absence or presence of Notch and/or EGFR signaling inhibitors.ResultsIn this study, we investigated gene expression and function of Notch1, EGFR and PDGFR to determine their role among GBM tumor core- (c-CSC) vs. peritumor tissue-derived cancer stem cells (p-CSC) of six cases of GBM. Notch inhibition significantly impaired cell growth of c-CSC compared to p-CSC pools, with no effects observed in cell cycle distribution, apoptosis and cell invasion assays. Instead, anti-EGFR therapy induced cell cycle arrest, sometimes associated with apoptosis and reduction of cell invasiveness in GBM CSC. In two cases, c-CSC pools were more sensitive to simultaneous anti-Notch and anti-EGFR treatment than either therapy alone compared to p-CSC, which were mostly resistant to treatment. We reported the overexpression of PDGFRα and its up-regulation following anti-EGFR therapy in GBM p-CSC compared to c-CSC. RNA interference of PDGFRα significantly reduced cell proliferation rate of p-CSC, while its pharmacological inhibition with Crenolanib impaired survival of both CSC pools, whose effects in combination with EGFR inhibition were maximized.ConclusionsWe have used different drugs combination to identify the more effective therapeutic targets for GBM CSC, particularly against GBM peritumor tissue-derived CSC, which are mostly resistant to treatments. Overall, our results provide the rationale for simultaneous targeting of EGFR and PDGFR, which would be beneficial in the treatment of GBM.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-247) contains supplementary material, which is available to authorized users.

Multiple chimeric antigen receptors successfully target chondroitin sulfate proteoglycan 4 in several different cancer histologies and cancer stem cells.

BackgroundThe development of immunotherapy has led to significant progress in the treatment of metastatic cancer, including the development of genetic engineering technologies that redirect lymphocytes to recognize and target a wide variety of tumor antigens. Chimeric antigen receptors (CARs) are hybrid proteins combining antibody recognition domains linked to T cell signaling elements. Clinical trials of CAR-transduced peripheral blood lymphocytes (PBL) have induced remission of both solid organ and hematologic malignancies. Chondroitin sulfate proteoglycan 4 (CSPG4) is a promising target antigen that is overexpressed in multiple cancer histologies including melanoma, triple-negative breast cancer, glioblastoma, mesothelioma and sarcoma.MethodsCSPG4 expression in cancer cell lines was assayed using flow cytometry (FACS) and reverse-transcription PCR (RT-PCR). Immunohistochemistry was utilized to assay resected melanomas and normal human tissues (n = 30) for CSPG4 expression and a reverse-phase protein array comprising 94 normal tissue samples was also interrogated for CSPG4 expression. CARs were successfully constructed from multiple murine antibodies (225.28S, TP41.2, 149.53) using second generation (CD28.CD3ζ) signaling domains. CAR sequences were cloned into a gamma-retroviral vector with subsequent successful production of retroviral supernatant and PBL transduction. CAR efficacy was assayed by cytokine release and cytolysis following coculture with target cell lines. Additionally, glioblastoma stem cells were generated from resected human tumors, and CSPG4 expression was determined by RT-PCR and FACS.ResultsImmunohistochemistry demonstrated prominent CSPG4 expression in melanoma tumors, but failed to demonstrate expression in any of the 30 normal human tissues studied. Two of 94 normal tissue protein lysates were positive by protein array. CAR constructs demonstrated cytokine secretion and cytolytic function after co-culture with tumor cell lines from multiple different histologies, including melanoma, breast cancer, mesothelioma, glioblastoma and osteosarcoma. Furthermore, we report for the first time that CSPG4 is expressed on glioblastoma cancer stem cells (GSC) and demonstrate that anti-CSPG4 CAR-transduced T cells recognize and kill these GSC.ConclusionsThe functionality of multiple different CARs, with the widespread expression of CSPG4 on multiple malignancies, suggests that CSPG4 may be an attractive candidate tumor antigen for CAR-based immunotherapies using appropriate technology to limit possible off-tumor toxicity.

Casein Kinase 2: a novel player in glioblastoma therapy and cancer stem cells.

Casein kinase 2 (CK2) is an oncogenic protein kinase which contributes to tumor development, proliferation, and suppression of apoptosis in multiple cancer types. The mechanism by which CK2 expression and activity leads to tumorigenesis in glioblastoma (GBM), a stage IV primary brain tumor, is being studied. Recent studies demonstrate that CK2 plays an important role in GBM formation and growth through the inhibition of tumor suppressors and activation of oncogenes. In addition, intriguing new reports indicate that CK2 may regulate GBM formation in a novel manner; CK2 may play a critical role in cancer stem cell (CSC) maintenance. Since glial CSCs have the ability to self-renew and initiate tumor growth, new treatments which target these CSCs are needed to treat this fatal disease. Inhibition of CK2 is potentially a novel method to inhibit GBM growth and reoccurrence by targeting the glial CSCs. A new, orally available, selective CK2 inhibitor, CX-4945 has had promising results when tested in cancer cell lines, in vivo xenograft models, and human clinical trials. The development of CK2 targeted inhibitors, starting with CX-4945, may lead to a new class of more effective cancer therapies.

New Molecules and Old Drugs as Emerging Approaches to Selectively Target Human Glioblastoma Cancer Stem Cells

Despite relevant progress obtained by multimodal treatment, glioblastoma (GBM), the most aggressive primary brain tumor, is still incurable. The most encouraging advancement of GBM drug research derives from the identification of cancer stem cells (CSCs), since these cells appear to represent the determinants of resistance to current standard therapies. The goal of most ongoing studies is to identify drugs able to affect CSCs biology, either inducing selective toxicity or differentiating this tumor cell population into nontumorigenic cells. Moreover, the therapeutic approach for GBM could be improved interfering with chemo- or radioresistance mechanisms, microenvironment signals, and the neoangiogenic process. During the last years, molecular targeted compounds such as sorafenib and old drugs, like metformin, displayed interesting efficacy in preclinical studies towards several tumors, including GBM, preferentially affecting CSC viability. In this review, the latest experimental results, controversies, and prospective application concerning these promising anticancer drugs will be discussed.