TGF-beta increases glioma-initiating cell self-renewal through the induction of LIF in human glioblastoma

BET Inhibitors Suppress ALDH Activity by Targeting ALDH1A1 Super-Enhancer in Ovarian Cancer

The emergence of tumor cells with certain stem-like characteristics, such as high aldehyde dehydrogenase (ALDH) activity due to ALDH1A1 expression, contributes to chemotherapy resistance and tumor relapse. However, clinically applicable inhibitors of ALDH activity have not been reported. There is evidence to suggest that epigenetic regulation of stem-related genes contributes to chemotherapy efficacy. Here, we show that bromodomain and extraterminal (BET) inhibitors suppress ALDH activity by abrogating BRD4-mediated ALDH1A1 expression through a super-enhancer element and its associated enhancer RNA. The clinically applicable small-molecule BET inhibitor JQ1 suppressed the outgrowth of cisplatin-treated ovarian cancer cells both in vitro and in vivo Combination of JQ1 and cisplatin improved the survival of ovarian cancer-bearing mice in an orthotopic model. These phenotypes correlate with inhibition of ALDH1A1 expression through a super-enhancer element and other stem-related genes in promoter regions bound by BRD4. Thus, targeting the BET protein BRD4 using clinically applicable small-molecule inhibitors, such as JQ1, is a promising strategy for targeting ALDH activity in epithelial ovarian cancer. Cancer Res; 76(21); 6320-30. ©2016 AACR.

Glioblastoma stem cells exploit the αvβ8 integrin-TGFβ1 signaling axis to drive tumor initiation and progression

Glioblastoma (GBM) is a primary brain cancer that contains populations of stem-like cancer cells (GSCs) that home to specialized perivascular niches. GSC interactions with their niche influence self-renewal, differentiation and drug resistance, although the pathways underlying these events remain largely unknown. Here, we report that the integrin αvβ8 and its latent transforming growth factor β1 (TGFβ1) protein ligand have central roles in promoting niche co-option and GBM initiation. αvβ8 integrin is highly expressed in GSCs and is essential for self-renewal and lineage commitment in vitro. Fractionation of β8^high cells from freshly resected human GBM samples also reveals a requirement for this integrin in tumorigenesis in vivo. Whole-transcriptome sequencing reveals that αvβ8 integrin regulates tumor development, in part, by driving TGFβ1-induced DNA replication and mitotic checkpoint progression. Collectively, these data identify the αvβ8 integrin-TGFβ1 signaling axis as crucial for exploitation of the perivascular niche and identify potential therapeutic targets for inhibiting tumor growth and progression in patients with GBM.

MicroRNA-124 inhibits the proliferation of C6 glioma cells by targeting Smad4

MicroRNA-124 (miR-124) has been shown to be downregulated in glioma; however, its biological functions in glioma are not yet fully understood. The aim of this study was to examine the Smad4‑dependent effects of miR‑124 on C6 glioma cell proliferation. In this study, the level of miR‑124 was found to be enhanced in C6 cells upon transfection with miR‑124 mimics, and the mechanisms of action of miR‑124 in C6 cells were investigated by reverse transcriptase-quantitative polymerase chain reaction, MTT assay, western blot analysis and luciferase reporter assays in vitro. The results revealed that miR‑124 expression was significantly lower in the C6 cells than in either normal rat brain tissue or astrocytes. Upon the overexpression of miR‑124, the proliferation of the C6 cells decreased and Smad4 expression was significantly suppressed. Smad4 was identified as a direct target of miR‑124 through luciferase reporter assays. Furthermore, miR‑124 was found to modulate signal transducer and activator of transcription 3 (Stat3) by downregulating Smad4 expression. Using small interfering RNA targeting Smad4 mRNA, we also confirmed that miR‑124 downregulated c‑Myc by modulating Smad4 expression. In addition, caspase‑3 expression was induced by miR‑124 overexpression, but not via Smad4 downregulation. On the whole, our results demonstrate that miR‑124 upregulation inhibits the growth of C6 glioma cells by targeting Smad4 directly. These findings may be clinically useful for the development of therapeutic strategies directed toward miR‑124 function in patients with glioma.

Glioblastoma-associated microglia and macrophages: targets for therapies to improve prognosis

Glioblastoma is the most common and most malignant primary adult human brain tumour. Diagnosis of glioblastoma carries a dismal prognosis. Treatment resistance and tumour recurrence are the result of both cancer cell proliferation and their interaction with the tumour microenvironment. A large proportion of the tumour microenvironment consists of an inflammatory infiltrate predominated by microglia and macrophages, which are thought to be subverted by glioblastoma cells for tumour growth. Thus, glioblastoma-associated microglia and macrophages are logical therapeutic targets. Their emerging roles in glioblastoma progression are reflected in the burgeoning research into therapeutics directed at their modification or elimination. Here, we review the biology of glioblastoma-associated microglia and macrophages, and model systems used to study these cells in vitro and in vivo. We discuss translation of results using these model systems and review recent advances in immunotherapies targeting microglia and macrophages in glioblastoma. Significant challenges remain but medications that affect glioblastoma-associated microglia and macrophages hold considerable promise to improve the prognosis for patients with this disease.

Transforming Growth Factor-β Receptors and Smads: Regulatory Complexity and Functional Versatility

Transforming growth factor (TGF)-β family proteins control cell physiology, proliferation, and growth, and direct cell differentiation, thus playing key roles in normal development and disease. The mechanisms of how TGF-β family ligands interact with heteromeric complexes of cell surface receptors to then activate Smad signaling that directs changes in gene expression are often seen as established. Even though TGF-β-induced Smad signaling may be seen as a linear signaling pathway with predictable outcomes, this pathway provides cells with a versatile means to induce different cellular responses. Fundamental questions remain as to how, at the molecular level, TGF-β and TGF-β family proteins activate the receptor complexes and induce a context-dependent diversity of cell responses. Among the areas of progress, we summarize new insights into how cells control TGF-β responsiveness by controlling the TGF-β receptors, and into the key roles and versatility of Smads in directing cell differentiation and cell fate selection.

CUEDC2 suppresses glioma tumorigenicity by inhibiting the activation of STAT3 and NF-κB signaling pathway

CUEDC2, a CUE domain containing 2 protein, plays critical roles in many biological processes, such as cell cycle, inflammation and tumorigenesis. However, whether CUEDC2 was involved in tumorigenesis of glioma and the possible mechanism remains to be elucidated. In the present study, our results implied that the expression of CUEDC2 was lower in the glioma tissue and glioma cell lines than that of normal tissue and asctrocyte cells. Downregulation of endogenous CUEDC2 in glioma U251 cell lines by RNAi promoted the tumor cells proliferation, migration, invasion and glioma neurosphere formation, while, overexpression of CUEDC2 showed the opposite effect. Further studies showed that overexpression of CUEDC2 suppressed the activation and nuclear translocation of phosphorylated-STAT3 (p-STAT3) but the level of p-STAT3 increased after interfering with the expression of CUEDC2. Moreover, CUEDC2 expression has an inhibitory effect on the activation of NF-κB. Thus, our studies suggested that the decreased expression of CUEDC2 in glioma led to the activation of transcription factor STAT3 and NF-κB signaling pathway which may be related to the tumorigenicity in glioma.

Cutting Edge: ERK1 Mediates the Autocrine Positive Feedback Loop of TGF-β and Furin in Glioma-Initiating Cells

Glioblastoma is the most common and aggressive intrinsic brain tumor in adults. Self-renewing, highly tumorigenic glioma-initiating cells (GIC) have been linked to glioma invasive properties, immunomodulation, and increased angiogenesis, leading to resistance to therapy. TGF-β signaling has been associated with the tumorigenic activity of GIC. TGF-β is synthesized as a precursor molecule and proteolytically processed to the mature form by members of the family of the proprotein convertases subtilisin/kexin. In this study we report that furin is unique among the proprotein convertases subtilisin/kexin in being highly expressed in human GIC. Furin cleaves and promotes activation of pro-TGF-β1 and pro-TGF-β2, and TGF-β2 in turn increases furin levels. Notably, TGF-β2 controls furin activity in an ALK-5-dependent manner involving the ERK/MAPK pathway. We thus uncover a role of ERK1 in the regulation of furin activity by supporting a self-sustaining loop for high TGF-β activity in GIC.

Biomarker and Histopathology Evaluation of Patients with Recurrent Glioblastoma Treated with Galunisertib, Lomustine, or the Combination of Galunisertib and Lomustine

Galunisertib, a Transforming growth factor-βRI (TGF-βRI) kinase inhibitor, blocks TGF-β-mediated tumor growth in glioblastoma. In a three-arm study of galunisertib (300 mg/day) monotherapy (intermittent dosing; each cycle =14 days on/14 days off), lomustine monotherapy, and galunisertib plus lomustine therapy, baseline tumor tissue was evaluated to identify markers associated with tumor stage (e.g., histopathology, Ki67, glial fibrillary acidic protein) and TGF-β-related signaling (e.g., pSMAD2). Other pharmacodynamic assessments included chemokine, cytokine, and T cell subsets alterations. 158 patients were randomized to galunisertib plus lomustine (n = 79), galunisertib (n = 39) and placebo+lomustine (n = 40). In 127 of these patients, tissue was adequate for central pathology review and biomarker work. Isocitrate dehydrogenase (IDH1) negative glioblastoma patients with baseline pSMAD2⁺ in cytoplasm had median overall survival (OS) 9.5 months vs. 6.9 months for patients with no tumor pSMAD2 expression (p = 0.4574). Eight patients were IDH1 R132H⁺ and had a median OS of 10.4 months compared to 6.9 months for patients with negative IDH1 R132H (p = 0.5452). IDH1 status was associated with numerically higher plasma macrophage-derived chemokine (MDC/CCL22), higher whole blood FOXP3, and reduced tumor CD3⁺ T cell counts. Compared to the baseline, treatment with galunisertib monotherapy preserved CD4⁺ T cell counts, eosinophils, lymphocytes, and the CD4/CD8 ratio. The T-regulatory cell compartment was associated with better OS with MDC/CCL22 as a prominent prognostic marker.

Patient-Specific Screening Using High-Grade Glioma Explants to Determine Potential Radiosensitization by a TGF-β Small Molecule Inhibitor

High-grade glioma (HGG), a deadly primary brain malignancy, manifests radioresistance mediated by cell-intrinsic and microenvironmental mechanisms. High levels of the cytokine transforming growth factor-β (TGF-β) in HGG promote radioresistance by enforcing an effective DNA damage response and supporting glioma stem cell self-renewal. Our analysis of HGG TCGA data and immunohistochemical staining of phosphorylated Smad2, which is the main transducer of canonical TGF-β signaling, indicated variable levels of TGF-β pathway activation across HGG tumors. These data suggest that evaluating the putative benefit of inhibiting TGF-β during radiotherapy requires personalized screening. Thus, we used explant cultures of seven HGG specimens as a rapid, patient-specific ex vivo platform to test the hypothesis that LY364947, a small molecule inhibitor of the TGF-β type I receptor, acts as a radiosensitizer in HGG. Immunofluorescence detection and image analysis of γ-H2AX foci, a marker of cellular recognition of radiation-induced DNA damage, and Sox2, a stem cell marker that increases post-radiation, indicated that LY364947 blocked these radiation responses in five of seven specimens. Collectively, our findings suggest that TGF-β signaling increases radioresistance in most, but not all, HGGs. We propose that short-term culture of HGG explants provides a flexible and rapid platform for screening context-dependent efficacy of radiosensitizing agents in patient-specific fashion. This time- and cost-effective approach could be used to personalize treatment plans in HGG patients.

USP26 regulates TGF-β signaling by deubiquitinating and stabilizing SMAD7

The amplitude of transforming growth factor-β (TGF-β) signal is tightly regulated to ensure appropriate physiological responses. As part of negative feedback loop SMAD7, a direct transcriptional target of downstream TGF-β signaling acts as a scaffold to recruit the E3 ligase SMURF2 to target the TGF-β receptor complex for ubiquitin-mediated degradation. Here, we identify the deubiquitinating enzyme USP26 as a novel integral component of this negative feedback loop. We demonstrate that TGF-β rapidly enhances the expression of USP26 and reinforces SMAD7 stability by limiting the ubiquitin-mediated turnover of SMAD7. Conversely, knockdown of USP26 rapidly degrades SMAD7 resulting in TGF-β receptor stabilization and enhanced levels of p-SMAD2. Clinically, loss of USP26 correlates with high TGF-β activity and confers poor prognosis in glioblastoma. Our data identify USP26 as a novel negative regulator of the TGF-β pathway and suggest that loss of USP26 expression may be an important factor in glioblastoma pathogenesis.

ZEB1 regulates glioma stemness through LIF repression

The identification of a stem cell regulatory gene which is aberrantly expressed in glioma and associated with patient survival would increase the understanding of the role of glioma cancer stem cells (GCSCs) in the virulence of gliomas. Interrogating the genomes of over 4000 brain cancers we identified ZEB1 deletion in ~15% (grade II and III) and 50% of glioblastomas. Meta-analysis of ZEB1 copy number status in 2,988 cases of glioma revealed disruptive ZEB1 deletions associated with decreased survival. We identified ZEB1 binding sites within the LIF (stemness factor) promoter region, and demonstrate LIF repression by ZEB1. ZEB1 knockdown in GCSCs caused LIF induction commensurate with GCSC self-renewal and inhibition of differentiation. IFN-γ treatment to GCSCs induced ZEB1 expression, attenuating LIF activities. These findings implicate ZEB1 as a stem cell regulator in glioma which when deleted leads to increased stemness, tumorigenicity and shortened patient survival.

TRIM8 regulates stemness in glioblastoma through PIAS3-STAT3

Glioblastoma (GBM) is the most malignant form of primary brain tumor, and GBM stem-like cells (GSCs) contribute to the rapid growth, therapeutic resistance, and clinical recurrence of these fatal tumors. STAT3 signaling supports the maintenance and proliferation of GSCs, yet regulatory mechanisms are not completely understood. Here, we report that tri-partite motif-containing protein 8 (TRIM8) activates STAT3 signaling to maintain stemness and self-renewing capabilities of GSCs. TRIM8 (also known as 'glioblastoma-expressed ring finger protein') is expressed equally in GBM and normal brain tissues, despite its hemizygous deletion in the large majority of GBMs, and its expression is highly correlated with stem cell markers. Experimental knockdown of TRIM8 reduced GSC self-renewal and expression of SOX2, NESTIN, and p-STAT3, and promoted glial differentiation. Overexpression of TRIM8 led to higher expression of p-STAT3, c-MYC, SOX2, NESTIN, and CD133, and enhanced GSC self-renewal. We found that TRIM8 activates STAT3 by suppressing the expression of PIAS3, an inhibitor of STAT3, most likely through E3-mediated ubiquitination and proteasomal degradation. Interestingly, we also found that STAT3 activation upregulates TRIM8, providing a mechanism for normalized TRIM8 expression in the setting of hemizygous gene deletion. These data demonstrate that bidirectional TRIM8-STAT3 signaling regulates stemness in GSC.

TGFΒ-induced transcription in cancer

The Transforming Growth Factor-beta (TGFβ) pathway mediates a broad spectrum of cellular processes and is involved in several diseases, including cancer. TGFβ has a dual role in tumours, acting as a tumour suppressor in the early phase of tumorigenesis and as a tumour promoter in more advanced stages. In this review, we discuss the effects of TGFβ-driven transcription on all stages of tumour progression, with special focus on lung cancer. Since some TGFβ target genes are specifically involved in promoting metastasis, we speculate that these genes might be good targets to block tumour progression without compromising the tumour suppressor effects of the TGFβ pathway.

Precision Medicine with TGF-β Inhibition Using Tumor Explants: Comment on "Patient-Specific Screening Using High-Grade Glioma Explants to Determine Potential Radiosensitization by a TGF-β Small Molecule Inhibitor" by N. Sumru Bayin et al

In a new report, Bayin et al. described an ex vivo explant model to test the patient-specific response to transforming growth factor-β inhibition in high-grade gliomas.

Mutational activation of BRAF confers sensitivity to transforming growth factor beta inhibitors in human cancer cells

Recent data implicate elevated transforming growth factor-β (TGFβ) signalling in BRAF inhibitor drug-resistance mechanisms, but the potential for targeting TGFβ signalling in cases of advanced melanoma has not been investigated. We show that mutant BRAFV600E confers an intrinsic dependence on TGFβ/TGFβ receptor 1 (TGFBR1) signalling for clonogenicity of murine melanocytes. Pharmacological inhibition of the TGFBR1 blocked the clonogenicity of human mutant BRAF melanoma cells through SMAD4-independent inhibition of mitosis, and also inhibited metastasis in xenografted zebrafish. When investigating the therapeutic potential of combining inhibitors of mutant BRAF and TGFBR1, we noted that unexpectedly, low-dose PLX-4720 (a vemurafenib analogue) promoted proliferation of drug-naïve melanoma cells. Pharmacological or pharmacogenetic inhibition of TGFBR1 blocked growth promotion and phosphorylation of SRC, which is frequently associated with vemurafenib-resistance mechanisms. Importantly, vemurafenib-resistant patient derived cells retained sensitivity to TGFBR1 inhibition, suggesting that TGFBR1 could be targeted therapeutically to combat the development of vemurafenib drug-resistance.

N-myc downstream-regulated gene 2 inhibits human cholangiocarcinoma progression and is regulated by leukemia inhibitory factor/MicroRNA-181c negative feedback pathway

Increasing evidence supports a role for N-myc downstream-regulated gene 2 (NDRG2) deregulation in tumorigenesis. We investigated the roles and mechanisms of NDRG2 in human cholangiocarcinoma (CCA) progression. In the present study, expression of NDRG2, microRNA (miR)-181c and leukemia inhibitory factor (LIF) in human CCA and adjacent nontumor tissues were examined. The effects of NDRG2 on CCA tumor growth and metastasis were determined both in vivo and in vitro. The role of the NDRG2/LIF/miR-181c signaling pathway in cholangiocarcinogenesis and metastasis were investigated both in vivo and in vitro. The results showed that human CCA tissues exhibited decreased levels of NDRG2 and increased levels of miR-181c and LIF compared with nontumor tissues. NDRG2 could inhibit CCA cell proliferation, chemoresistance, and metastasis both in vitro and in vivo. We found that NDRG2 is a target gene of miR-181c, and the down-regulation of NDRG2 was attributed to miR-181c overexpression in CCA. Furthermore, miR-181c can be activated by LIF treatment, whereas NDRG2 could inhibit LIF transcription through disrupting the binding between Smad, small mothers against decapentaplegic complex and LIF promoter. Down-regulation of NDRG2 and overexpression of miR-181c or LIF are significantly associated with a poorer overall survival (OS) in CCA patients. Finally, we found that a combination of NDRG2, miR-181c, and LIF expression is a strong predictor of prognosis in CCA patients.

CONCLUSION

These results establish the counteraction between NDRG2 and LIF/miR-181c as a key mechanism that regulates cholangiocarcinogenesis and metastasis. Our results elucidated a novel pathway in NDRG2-mediated inhibition of cholangiocarcinogenesis and metastasis and suggest new therapeutic targets, including NDRG2, LIF, miR-181c, and transforming growth factor beta, in CCA prevention and treatment. (Hepatology 2016;64:1606-1622).

Tetraspanin CD9 stabilizes gp130 by preventing its ubiquitin-dependent lysosomal degradation to promote STAT3 activation in glioma stem cells

Glioblastoma (GBM) is the most malignant and lethal brain tumor harboring glioma stem cells (GSCs) that promote tumor propagation and therapeutic resistance. GSCs preferentially express several critical cell surface molecules that regulate the pro-survival signaling for maintaining the stem cell-like phenotype. Tetraspanin CD9 has recently been reported as a GSC biomarker that is relevant to the GSC maintenance. However, the underlying molecular mechanisms of CD9 in maintaining GSC property remain elusive. Herein, we report that CD9 stabilizes the IL-6 receptor glycoprotein 130 (gp130) by preventing its ubiquitin-dependent lysosomal degradation to facilitate the STAT3 activation in GSCs. CD9 is preferentially expressed in GSCs of human GBM tumors. Mass spectrometry analysis identified gp130 as an interacting protein of CD9 in GSCs, which was confirmed by immunoprecipitation and immunofluorescent analyses. Disrupting CD9 or gp130 by shRNA significantly inhibited the self-renewal and promoted the differentiation of GSCs. Moreover, CD9 disruption markedly reduced gp130 protein levels and STAT3 activating phosphorylation in GSCs. CD9 stabilized gp130 by preventing its ubiquitin-dependent lysosomal degradation to promote the BMX-STAT3 signaling in GSCs. Importantly, targeting CD9 potently inhibited GSC tumor growth in vivo, while ectopic expression of the constitutively activated STAT3 (STAT3-C) restored the tumor growth impaired by CD9 disruption. Collectively, we uncovered a critical regulatory mechanism mediated by tetraspanin CD9 to maintain the stem cell-like property and tumorigenic potential of GSCs.

Cancer stem cell signaling pathways

Tissue development and homeostasis are governed by the actions of stem cells. Multipotent cells are capable of self-renewal during the course of one's lifetime. The accurate and appropriate regulation of stem cell functions is absolutely critical for normal biological activity. Several key developmental or signaling pathways have been shown to play essential roles in this regulatory capacity. Specifically, the Janus-activated kinase/signal transducer and activator of transcription, Hedgehog, Wnt, Notch, phosphatidylinositol 3-kinase/phosphatase and tensin homolog, and nuclear factor-κB signaling pathways have all been shown experimentally to mediate various stem cell properties, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation. Unsurprisingly, many of these crucial signaling pathways are dysregulated in cancer. Growing evidence suggests that overactive or abnormal signaling within and among these pathways may contribute to the survival of cancer stem cells (CSCs). CSCs are a relatively rare population of cancer cells capable of self-renewal, differentiation, and generation of serially transplantable heterogeneous tumors of several types of cancer.

Transforming growth factor β as regulator of cancer stemness and metastasis

Key elements of cancer progression towards metastasis are the biological actions of cancer stem cells and stromal cells in the tumour microenvironment. Cross-communication between tumour and stromal cells is mediated by secreted cytokines, one of which, the transforming growth factor β (TGFβ), regulates essentially every cell within the malignant tissue. In this article, we focus on the actions of TGFβ on cancer stem cells, cancer-associated fibroblasts and immune cells that assist the overall process of metastatic dissemination. We aim at illustrating intricate connections made by various cells in the tumour tissue and which depend on the action of TGFβ.

Overview of Transforming Growth Factor β Superfamily Involvement in Glioblastoma Initiation and Progression

Glioblastoma, also known as glioblastoma multiforme (GBM), is the most aggressive of human brain tumors and has a stunning progression with a mean survival of one year from the date of diagnosis. High cell proliferation, angiogenesis and/or necrosis are histopathological features of this cancer, which has no efficient curative therapy. This aggressiveness is associated with particular heterogeneity of the tumor featuring multiple genetic and epigenetic alterations, but also with implications of aberrant signaling driven by growth factors. The transforming growth factor β (TGFβ) superfamily is a large group of structurally related proteins including TGFβ subfamily members Nodal, Activin, Lefty, bone morphogenetic proteins (BMPs) and growth and differentiation factor (GDF). It is involved in important biological functions including morphogenesis, embryonic development, adult stem cell differentiation, immune regulation, wound healing and inflammation. This superfamily is also considered to impact on cancer biology including that of GBM, with various effects depending on the member. The TGFβ subfamily, in particular, is overexpressed in some GBM types which exhibit aggressive phenotypes. This subfamily impairs anti-cancer immune responses in several ways, including immune cells inhibition and major histocompatibility (MHC) class I and II abolishment. It promotes GBM angiogenesis by inducing angiogenic factors such as vascular endothelial growth factor (VEGF), plasminogen activator inhibitor (PAI-I) and insulin- like growth factor-binding protein 7 (IGFBP7), contributes to GBM progression by inducing metalloproteinases (MMPs), "pro-neoplastic" integrins (αvβ3, α5β1) and GBM initiating cells (GICs) as well as inducing a GBM mesenchymal phenotype. Equally, Nodal promotes GICs, induces cancer metabolic switch and supports GBM cell proliferation, but is negatively regulated by Lefty. Activin promotes GBM cell proliferation while GDF yields immune-escape function. On the other hand, BMPs target GICS and induce differentiation and sensitivity to chemotherapy. This multifaceted involvement of this superfamily in GBM necessitates different strategies in anti-cancer therapy. While suppressing the TGFβ subfamily yields advantageous results, enhancing BMPs production is also beneficial.

Integrins in glioblastoma: Still an attractive target?

Integrin-mediated signaling pathways have been found to promote the invasiveness and survival of glioma cells by modifying the brain microenvironment to support the formation of the tumoral niche. A variety of cells in the niche express integrin receptors, including tumor-associated macrophages, fibroblasts, endothelial cells and pericytes. In particular, RGD-binding integrins have been demonstrated to have an important role in the epithelial-mesenchymal transition process, considered the first step in the infiltration of tissue by cancer cells and molecular markers of which have been found in glioma cells. In simultaneous research, Small Molecule Integrin Antagonists (SMIA) yielded initially promising results in in vitro and in vivo studies, leading to clinical trials to test their safety and efficacy in combination with other anticancer drugs in the treatment of several tumor types. The initially high expectations, especially because of their antiangiogenic activity, which appeared to be a winning strategy against GBM, were not confirmed and this cast serious doubts on the real benefits to be gained from the use of SMIA for the treatment of cancer in humans. In this review, we provide an overview of recent findings concerning the functional roles of integrins, especially RGD-binding integrins, in the processes related to glioma cells survival and brain tissue infiltration. These findings disclose a new scenario in which recently developed SMIA might become useful tools to hinder glioblastoma cell dissemination.

A Phase II randomized study of galunisertib monotherapy or galunisertib plus lomustine compared with lomustine monotherapy in patients with recurrent glioblastoma

BACKGROUND

The combination of galunisertib, a transforming growth factor (TGF)-β receptor (R)1 kinase inhibitor, and lomustine was found to have antitumor activity in murine models of glioblastoma.

METHODS

Galunisertib (300 mg/day) was given orally 14 days on/14 days off (intermittent dosing). Lomustine was given as approved. Patients were randomized in a 2:1:1 ratio to galunisertib + lomustine, galunisertib monotherapy, or placebo + lomustine. The primary objective was overall survival (OS); secondary objectives were safety, pharmacokinetics (PKs), and antitumor activity.

RESULTS

One hundred fifty-eight patients were randomized: galunisertib + lomustine (N = 79), galunisertib (N = 39), and placebo + lomustine (N = 40). Baseline characteristics were: male (64.6%), white (75.3%), median age 58 years, ECOG performance status (PS) 1 (63.3%), and primary glioblastoma (93.7%). The PKs of galunisertib were not altered with lomustine, and galunisertib had a median half-life of ∼8 hours. Median OS in months (95% credible interval [CrI]) for galunisertib + lomustine was 6.7 (range: 5.3-8.5), 8.0 (range: 5.7-11.7) for galunisertib alone, and 7.5 (range: 5.6-10.3) for placebo + lomustine. There was no difference in OS for patients treated with galunisertib + lomustine compared with placebo + lomustine [P (HR < 1) = 26%]. Median progression-free survival of ∼2 months was observed in all 3 arms. Among 8 patients with IDH1 mutation, 7 patients were treated with galunisertib (monotherapy or with lomustine); OS ranged from 4 to 17 months. Patients treated with galunisertib alone had fewer drug-related grade 3/4 adverse events (n = 34) compared with lomustine-treated patients (10% vs 26%). Baseline PS, post-discontinuation of bevacizumab, tumor size, and baseline levels of MDC/CCL22 were correlated with OS.

CONCLUSIONS

Galunisertib + lomustine failed to demonstrate improved OS relative to placebo + lomustine. Efficacy outcomes were similar in all 3 arms.

CLINICAL TRIAL REGISTRATION

NCT01582269, ClinicalTrials.gov.

The NSL Chromatin-Modifying Complex Subunit KANSL2 Regulates Cancer Stem-like Properties in Glioblastoma That Contribute to Tumorigenesis

KANSL2 is an integral subunit of the nonspecific lethal (NSL) chromatin-modifying complex that contributes to epigenetic programs in embryonic stem cells. In this study, we report a role for KANSL2 in regulation of stemness in glioblastoma (GBM), which is characterized by heterogeneous tumor stem-like cells associated with therapy resistance and disease relapse. KANSL2 expression is upregulated in cancer cells, mainly at perivascular regions of tumors. RNAi-mediated silencing of KANSL2 in GBM cells impairs their tumorigenic capacity in mouse xenograft models. In clinical specimens, we found that expression levels of KANSL2 correlate with stemness markers in GBM stem-like cell populations. Mechanistic investigations showed that KANSL2 regulates cell self-renewal, which correlates with effects on expression of the stemness transcription factor POU5F1. RNAi-mediated silencing of POU5F1 reduced KANSL2 levels, linking these two genes to stemness control in GBM cells. Together, our findings indicate that KANSL2 acts to regulate the stem cell population in GBM, defining it as a candidate GBM biomarker for clinical use. Cancer Res; 76(18); 5383-94. ©2016 AACR.

TGFβ-Responsive HMOX1 Expression Is Associated with Stemness and Invasion in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is the most common and lethal adult brain tumor. Resistance to standard radiation and chemotherapy is thought to involve survival of GBM cancer stem cells (CSCs). To date, no single marker for identifying GBM CSCs has been able to capture the diversity of CSC populations, justifying the needs for additional CSC markers for better characterization. Employing targeted mass spectrometry, here we present five cell-surface markers HMOX1, SLC16A1, CADM1, SCAMP3, and CLCC1 which were found to be elevated in CSCs relative to healthy neural stem cells (NSCs). Transcriptomic analyses of REMBRANDT and TCGA compendiums also indicated elevated expression of these markers in GBM relative to controls and non-GBM diseases. Two markers SLC16A1 and HMOX1 were found to be expressed among pseudopalisading cells that reside in the hypoxic region of GBM, substantiating the histopathological hallmarks of GBM. In a prospective study (N = 8) we confirmed the surface expression of HMOX1 on freshly isolated primary GBM cells (P0). Employing functional assays that are known to evaluate stemness, we demonstrate that elevated HMOX1 expression is associated with stemness in GBM and can be modulated through TGFβ. siRNA-mediated silencing of HMOX1 impaired GBM invasion-a phenomenon related to poor prognosis. In addition, surgical resection of GBM tumors caused declines (18% ± 5.1SEM) in the level of plasma HMOX1 as measured by ELISA, in 8/10 GBM patients. These findings indicate that HMOX1 is a robust predictor of GBM CSC stemness and pathogenesis. Further understanding of the role of HMOX1 in GBM may uncover novel therapeutic approaches. Stem Cells 2016;34:2276-2289.

Molecular mechanisms of the effect of TGF-β1 on U87 human glioblastoma cells

Glioblastoma multiforme (GBM) is the most widespread and aggressive type of primary brain tumor. The prognosis following diagnosis with GBM is poor, with a median survival time of 14 months. Tumor cell invasion, metastasis and proliferation are the major causes of mortality in patients with GBM. In order to develop effective GBM treatment methods it is necessary to identify novel targets involved in these processes. Recently, there has been increasing interest in investigating the signaling pathways involved in GBM development, and the transforming growth factor-β (TGF-β) signaling pathway is understood to be significant for regulating the behavior of GBM, as well as stimulating its invasion and metastatic development. Particular interest has been given to investigating the modulation of TGF-β-induced epithelial-to-mesenchymal transition (EMT); during this process, epithelial cells transdifferentiate into mobile cells with a mesenchymal phenotype. The induction of EMT increases the invasiveness of various types of carcinoma; however, the role of TGF-β in this process remains to be elucidated, particularly in the case of GBM. The current study presents a comparative proteome mapping of the U87 human glioblastoma cell line, with and without TGF-β1 treatment. Proteome analysis identified numerous proteins involved in the molecular mechanisms of GBM oncogenesis and TGF-β1 signaling in glioblastoma. The results of the present study facilitated the identification of novel potential markers of metastasis and candidates for targeted glioblastoma therapy, which may potentially be validated and used in clinical medicine to develop improved approaches for GBM diagnosis and treatment.

Cancer Stem Cell-Secreted Macrophage Migration Inhibitory Factor Stimulates Myeloid Derived Suppressor Cell Function and Facilitates Glioblastoma Immune Evasion

Shifting the balance away from tumor-mediated immune suppression toward tumor immune rejection is the conceptual foundation for a variety of immunotherapy efforts currently being tested. These efforts largely focus on activating antitumor immune responses but are confounded by multiple immune cell populations, including myeloid-derived suppressor cells (MDSCs), which serve to suppress immune system function. We have identified immune-suppressive MDSCs in the brains of GBM patients and found that they were in close proximity to self-renewing cancer stem cells (CSCs). MDSCs were selectively depleted using 5-flurouracil (5-FU) in a low-dose administration paradigm, which resulted in prolonged survival in a syngeneic mouse model of glioma. In coculture studies, patient-derived CSCs but not nonstem tumor cells selectively drove MDSC-mediated immune suppression. A cytokine screen revealed that CSCs secreted multiple factors that promoted this activity, including macrophage migration inhibitory factor (MIF), which was produced at high levels by CSCs. Addition of MIF increased production of the immune-suppressive enzyme arginase-1 in MDSCs in a CXCR2-dependent manner, whereas blocking MIF reduced arginase-1 production. Similarly to 5-FU, targeting tumor-derived MIF conferred a survival advantage to tumor-bearing animals and increased the cytotoxic T cell response within the tumor. Importantly, tumor cell proliferation, survival, and self-renewal were not impacted by MIF reduction, demonstrating that MIF is primarily an indirect promoter of GBM progression, working to suppress immune rejection by activating and protecting immune suppressive MDSCs within the GBM tumor microenvironment. Stem Cells 2016;34:2026-2039.

TGF-β and the TGF-β Family: Context-Dependent Roles in Cell and Tissue Physiology

The transforming growth factor-β (TGF-β) is the prototype of the TGF-β family of growth and differentiation factors, which is encoded by 33 genes in mammals and comprises homo- and heterodimers. This review introduces the reader to the TGF-β family with its complexity of names and biological activities. It also introduces TGF-β as the best-studied factor among the TGF-β family proteins, with its diversity of roles in the control of cell proliferation and differentiation, wound healing and immune system, and its key roles in pathology, for example, skeletal diseases, fibrosis, and cancer.

CDC20 maintains tumor initiating cells

Glioblastoma is the most prevalent and lethal primary intrinsic brain tumor. Glioblastoma displays hierarchical arrangement with a population of self-renewing and tumorigenic glioma tumor initiating cells (TICs), or cancer stem cells. While non-neoplastic neural stem cells are generally quiescent, glioblastoma TICs are often proliferative with mitotic control offering a potential point of fragility. Here, we interrogate the role of cell-division cycle protein 20 (CDC20), an essential activator of anaphase-promoting complex (APC) E3 ubiquitination ligase, in the maintenance of TICs. By chromatin analysis and immunoblotting, CDC20 was preferentially expressed in TICs relative to matched non-TICs. Targeting CDC20 expression by RNA interference attenuated TIC proliferation, self-renewal and in vivo tumor growth. CDC20 disruption mediated its effects through induction of apoptosis and inhibition of cell cycle progression. CDC20 maintains TICs through degradation of p21^CIP1/WAF1, a critical negative regulator of TICs. Inhibiting CDC20 stabilized p21^CIP1/WAF1, resulting in repression of several genes critical to tumor growth and survival, including CDC25C, c-Myc and Survivin. Transcriptional control of CDC20 is mediated by FOXM1, a central transcription factor in TICs. These results suggest CDC20 is a critical regulator of TIC proliferation and survival, linking two key TIC nodes – FOXM1 and p21^CIP1/WAF1 — elucidating a potential point for therapeutic intervention.

Ovarian cancer stem-like cells differentiate into endothelial cells and participate in tumor angiogenesis through autocrine CCL5 signaling

Cancer stem cells (CSCs) are well known for their self-regeneration and tumorigenesis potential. In addition, the multi-differentiation potential of CSCs has become a popular issue and continues to attract increased research attention. Recent studies demonstrated that CSCs are able to differentiate into functional endothelial cells and participate in tumor angiogenesis. In this study, we found that ovarian cancer stem-like cells (CSLCs) activate the NF-κB and STAT3 signal pathways through autocrine CCL5 signaling and mediate their own differentiation into endothelial cells (ECs). Our data demonstrate that CSLCs differentiate into ECs morphologically and functionally. Anti-CCL5 antibodies and CCL5-shRNA lead to markedly inhibit EC differentiation and the tube formation of CSLCs, both in vitro and in vivo. Recombinant human-CCL5 significantly promotes ovarian CSLCs that differentiate into ECs and form microtube network. The CCL5-mediated EC differentiation of CSLCs depends on binding to receptors, such as CCR1, CCR3, and CCR5. The results demonstrated that CCL5-CCR1/CCR3/CCR5 activates the NF-κB and STAT3 signal pathways, subsequently mediating the differentiation of CSLCs into ECs. Therefore, this study was conducted based on the theory that CSCs improve tumor angiogenesis and provides a novel strategy for anti-angiogenesis in ovarian cancer.

Prioritization schema for immunotherapy clinical trials in glioblastoma

BACKGROUND

Emerging immunotherapeutic strategies for the treatment of glioblastoma (GBM) such as dendritic cell (DC) vaccines, heat shock proteins, peptide vaccines, and adoptive T-cell therapeutics, to name a few, have transitioned from the bench to clinical trials. With upcoming strategies and developing therapeutics, it is challenging to critically evaluate the practical, clinical potential of individual approaches and to advise patients on the most promising clinical trials.

METHODS

The authors propose a system to prioritize such therapies in an organized and data-driven fashion. This schema is based on four categories of factors: antigenic target robustness, immune-activation and -effector responses, preclinical vetting, and early evidence of clinical response. Each of these categories is subdivided to focus on the most salient elements for developing a successful immunotherapeutic approach for GBM, and a numerical score is generated.

RESULTS

The Score Card reveals therapeutics that have the most robust data to support their use, provides a reference prioritization score, and can be applied in a reiterative fashion with emerging data.

CONCLUSIONS

The authors hope that this schema will give physicians an evidence-based and rational framework to make the best referral decisions to better guide and serve this patient population.

Mutual regulation and targeting of multidrug resistance and cancer stem phenotype

Targeting stemness mechanisms leads to the suppression of ABC transporter activity and elimination of CSCs.

The Microenvironment of Lung Cancer and Therapeutic Implications

The tumor microenvironment (TME) represents a milieu that enables tumor cells to acquire the hallmarks of cancer. The TME is heterogeneous in composition and consists of cellular components, growth factors, proteases, and extracellular matrix. Concerted interactions between genetically altered tumor cells and genetically stable intratumoral stromal cells result in an "activated/reprogramed" stroma that promotes carcinogenesis by contributing to inflammation, immune suppression, therapeutic resistance, and generating premetastatic niches that support the initiation and establishment of distant metastasis. The lungs present a unique milieu in which tumors progress in collusion with the TME, as evidenced by regions of aberrant angiogenesis, acidosis and hypoxia. Inflammation plays an important role in the pathogenesis of lung cancer, and pulmonary disorders in lung cancer patients such as chronic obstructive pulmonary disease (COPD) and emphysema, constitute comorbid conditions and are independent risk factors for lung cancer. The TME also contributes to immune suppression, induces epithelial-to-mesenchymal transition (EMT) and diminishes efficacy of chemotherapies. Thus, the TME has begun to emerge as the "Achilles heel" of the disease, and constitutes an attractive target for anti-cancer therapy. Drugs targeting the components of the TME are making their way into clinical trials. Here, we will focus on recent advances and emerging concepts regarding the intriguing role of the TME in lung cancer progression, and discuss future directions in the context of novel diagnostic and therapeutic opportunities.

The Impact of Hypoxia and Mesenchymal Transition on Glioblastoma Pathogenesis and Cancer Stem Cells Regulation

Glioblastoma (GBM) is an aggressive primary brain tumor with potential for wide dissemination and resistance to standard treatments. Although GBM represents a single histopathologic diagnosis under current World Health Organization criteria, data from multiplatform molecular profiling efforts, including The Cancer Genome Atlas, indicate that multiple subgroups with distinct markers and biology exist. It remains unclear whether treatment resistance differs based on subgroup. Recent evidence suggests that hypoxia, or absence of normal tissue oxygenation, is important in generating tumor resistance through a signaling cascade driven by hypoxia-inducible factors and vascular endothelial growth factor. Hypoxia can result in isolation of tumor cells from therapeutic agents and activation of downstream tumor protective mechanisms. In addition, there are links between hypoxia and the phenomenon of mesenchymal transition in gliomas. Mesenchymal transformation in gliomas resembles at many levels the epithelial-mesenchymal transition that has been described in other solid tumors in which epithelial cells lose their epithelial characteristics and take on a more mesenchymal phenotype, but the mesenchymal transition in brain tumors is also distinct, perhaps related to the unique cell types and cellular organization in the brain and brain tumors. Cancer stem cells, which are specific cell populations involved in self-renewal, differentiation, and GBM pathophysiology, are also importantly regulated by hypoxia signaling pathways. In this review, we discuss the interplay of hypoxia and mesenchymal signaling in GBM including the key pathway regulators and downstream genes, the effect of these processes in regulation of the tumor microenvironment and cancer stem cells, and their role in treatment resistance.

HIF-2α mediates hypoxia-induced LIF expression in human colorectal cancer cells

Leukemia inhibitory factor (LIF), a multi-functional cytokine, has a complex role in cancer. While LIF induces the differentiation of several myeloid leukemia cells and inhibits their growth, it also promotes tumor progression, metastasis and chemoresistance in many solid tumors. LIF is frequently overexpressed in a variety of human tumors and its overexpression is often associated with poor prognosis of patients. Currently, the mechanism for LIF overexpression in tumor cells is not well-understood. Here, we report that hypoxia, a hallmark of solid tumors, induced LIF mRNA expression in human colorectal cancer cells. Analysis of LIF promoter revealed several hypoxia-responsive elements (HREs) that can specifically interact with and be transactivated by HIF-2α but not HIF-1α. Consistently, ectopic expression of HIF-2α but not HIF-1α transcriptionally induced LIF expression levels in cells. Knockdown of endogenous HIF-2α but not HIF-1α by siRNA largely abolished the induction of LIF by hypoxia in cells. Furthermore, there is a strong association of HIF-2α overexpression with LIF overexpression in human colorectal cancer specimens. In summary, results from this study demonstrate that hypoxia induces LIF expression in human cancer cells mainly through HIF-2α, which could be an important underlying mechanism for LIF overexpression in human cancers.

The regulation of leukemia inhibitory factor

Leukemia inhibitory factor (LIF), a secreted cytokine, plays an important role in a wide array of biological processes including inducing differentiation of leukemia cell, inflammatory response, neuronal development, embryonic implantation, stem cell self-renewal and cancer progression, etc. LIF exerts its biological functions mainly through the activation and regulation of JAK/STAT3, AKT, EKR1/2 and mTOR signal pathways. The expression levels of LIF are regulated by many different factors under different conditions in different tissue/cell types. For example, estrogen and p53 are important regulators for the high LIF production in uterine tissues at the implantation stage. Hypoxia plays a critical role in LIF overexpression in solid tumors. Many cytokines, including IL-6, IL-1β, can also induce the LIF expression and production. In this review, we summarize the current understanding on the transcriptional regulation of LIF under various conditions.

Common stemness regulators of embryonic and cancer stem cells

Pluripotency of embryonic stem cells (ESCs) and induced pluripotent stem cells is regulated by a well characterized gene transcription circuitry. The circuitry is assembled by ESC specific transcription factors, signal transducing molecules and epigenetic regulators. Growing understanding of stem-like cells, albeit of more complex phenotypes, present in tumors (cancer stem cells), provides a common conceptual and research framework for basic and applied stem cell biology. In this review, we highlight current results on biomarkers, gene signatures, signaling pathways and epigenetic regulators that are common in embryonic and cancer stem cells. We discuss their role in determining the cell phenotype and finally, their potential use to design next generation biological and pharmaceutical approaches for regenerative medicine and cancer therapies.

An Eighteen Serum Cytokine Signature for Discriminating Glioma from Normal Healthy Individuals

Glioblastomas (GBM) are largely incurable as they diffusely infiltrate adjacent brain tissues and are difficult to diagnose at early stages. Biomarkers derived from serum, which can be obtained by minimally invasive procedures, may help in early diagnosis, prognosis and treatment monitoring. To develop a serum cytokine signature, we profiled 48 cytokines in sera derived from normal healthy individuals (n = 26) and different grades of glioma patients (n = 194). We divided the normal and grade IV glioma/GBM serum samples randomly into equal sized training and test sets. In the training set, the Prediction Analysis for Microarrays (PAM) identified a panel of 18 cytokines that could discriminate GBM sera from normal sera with maximum accuracy (95.40%) and minimum error (4.60%). The 18-cytokine signature obtained in the training set discriminated GBM sera from normal sera in the test set as well (accuracy 96.55%; error 3.45%). Interestingly, the 18-cytokine signature also differentiated grade II/Diffuse Astrocytoma (DA) and grade III/Anaplastic Astrocytoma (AA) sera from normal sera very efficiently (DA vs. normal–accuracy 96.00%, error 4.00%; AA vs. normal–accuracy 95.83%, error 4.17%). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using 18 cytokines resulted in the enrichment of two pathways, cytokine-cytokine receptor interaction and JAK-STAT pathways with high significance. Thus our study identified an 18-cytokine signature for distinguishing glioma sera from normal healthy individual sera and also demonstrated the importance of their differential abundance in glioma biology.

Antitumorigenic effect of interferon-β by inhibition of undifferentiated glioblastoma cells

Glioma stem-like cells (GSCs) are undifferentiated cells that are considered to be an origin of glioblastomas. Furthermore, they may contribute to treatment resistance and recurrence in glioblastomas. GSCs differentiate into differentiated glioma cells (non-glioma stem-like cells: non-GSCs), and interconversion might occur between GSCs and non-GSCs. We investigated whether interferon-beta (IFN-β) could exert any efficacy towards GSCs or such interconversion processes. The neural stem cell marker CD133 and pluripotency marker Nanog in GSCs were analyzed to evaluate their differentiation levels. GSCs were considered to undergo differentiation into non-GSCs upon serum exposure, since the expression of CD133 and Nanog in the GSCs was negatively affected. Furthermore, the cells regained their undifferentiated features upon removal of the serum. However, we verified that IFN-β reduced cell proliferation and tumor sphere formation in GSCs, and induced suppression of the restoration of such undifferentiated features. In addition, we also confirmed that IFN-β suppressed the acquisition process of undifferentiated features in human malignant glioma cell lines. Our data thus suggest that IFN-β could be an effective agent not only through its cell growth inhibitory effect on GSCs but also as a means of targeting the interconversion between GSCs and non-GSCs, indicating the possibility of IFN-β being used to prevent treatment resistance and recurrence in glioblastomas, via the inhibition of undifferentiated features.

Radiation-induced glioblastoma signaling cascade regulates viability, apoptosis and differentiation of neural stem cells (NSC)

Ionizing radiation alone or in combination with chemotherapy is the main treatment modality for brain tumors including glioblastoma. Adult neurons and astrocytes demonstrate substantial radioresistance; in contrast, human neural stem cells (NSC) are highly sensitive to radiation via induction of apoptosis. Irradiation of tumor cells has the potential risk of affecting the viability and function of NSC. In this study, we have evaluated the effects of irradiated glioblastoma cells on viability, proliferation and differentiation potential of non-irradiated (bystander) NSC through radiation-induced signaling cascades. Using media transfer experiments, we demonstrated significant effects of the U87MG glioblastoma secretome after gamma-irradiation on apoptosis in non-irradiated NSC. Addition of anti-TRAIL antibody to the transferred media partially suppressed apoptosis in NSC. Furthermore, we observed a dramatic increase in the production and secretion of IL8, TGFβ1 and IL6 by irradiated glioblastoma cells, which could promote glioblastoma cell survival and modify the effects of death factors in bystander NSC. While differentiation of NSC into neurons and astrocytes occurred efficiently with the corresponding differentiation media, pretreatment of NSC for 8 h with medium from irradiated glioblastoma cells selectively suppressed the differentiation of NSC into neurons, but not into astrocytes. Exogenous IL8 and TGFβ1 increased NSC/NPC survival, but also suppressed neuronal differentiation. On the other hand, IL6 was known to positively affect survival and differentiation of astrocyte progenitors. We established a U87MG neurosphere culture that was substantially enriched by SOX2(+) and CD133(+) glioma stem-like cells (GSC). Gamma-irradiation up-regulated apoptotic death in GSC via the FasL/Fas pathway. Media transfer experiments from irradiated GSC to non-targeted NSC again demonstrated induction of apoptosis and suppression of neuronal differentiation of NSC. In summary, intercellular communication between glioblastoma cells and bystander NSC/NPC could be involved in the amplification of cancer pathology in the brain.

Gamma tocotrienol targets tyrosine phosphatase SHP2 in mammospheres resulting in cell death through RAS/ERK pathway

Background

There is increasing evidence supporting the concept of cancer stem cells (CSCs), which are responsible for the initiation, growth and metastasis of tumors. CSCs are thus considered the target for future cancer therapies. To achieve this goal, identifying potential therapeutic targets for CSCs is essential.

Methods

We used a natural product of vitamin E, gamma tocotrienol (gamma-T3), to treat mammospheres and spheres from colon and cervical cancers. Western blotting and real-time RT-PCR were employed to identify the gene and protein targets of gamma-T3 in mammospheres.

Results

We found that mammosphere growth was inhibited in a dose dependent manner, with total inhibition at high doses. Gamma-T3 also inhibited sphere growth in two other human epithelial cancers, colon and cervix. Our results suggested that both Src homology 2 domain-containing phosphatase 1 (SHP1) and 2 (SHP2) were affected by gamma-T3 which was accompanied by a decrease in K- and H-Ras gene expression and phosphorylated ERK protein levels in a dose dependent way. In contrast, expression of self-renewal genes TGF-beta and LIF, as well as ESR signal pathways were not affected by the treatment. These results suggest that gamma-T3 specifically targets SHP2 and the RAS/ERK signaling pathway.

Conclusions

SHP1 and SHP2 are potential therapeutic targets for breast CSCs and gamma-T3 is a promising natural drug for future breast cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1614-1) contains supplementary material, which is available to authorized users.

Mesenchymal stem cells from human fat engineered to secrete BMP4 are nononcogenic, suppress brain cancer, and prolong survival

PURPOSE

Glioblastoma is the most common adult primary malignant intracranial cancer. It is associated with poor outcomes because of its invasiveness and resistance to multimodal therapies. Human adipose-derived mesenchymal stem cells (hAMSC) are a potential treatment because of their tumor tropism, ease of isolation, and ability to be engineered. In addition, bone morphogenetic protein 4 (BMP4) has tumor-suppressive effects on glioblastoma and glioblastoma brain tumor-initiating cells (BTIC), but is difficult to deliver to brain tumors. We sought to engineer BMP4-secreting hAMSCs (hAMSCs-BMP4) and evaluate their therapeutic potential on glioblastoma.

EXPERIMENTAL DESIGN

The reciprocal effects of hAMSCs on primary human BTIC proliferation, differentiation, and migration were evaluated in vitro. The safety of hAMSC use was evaluated in vivo by intracranial coinjections of hAMSCs and BTICs in nude mice. The therapeutic effects of hAMSCs and hAMSCs-BMP4 on the proliferation and migration of glioblastoma cells as well as the differentiation of BTICs, and survival of glioblastoma-bearing mice were evaluated by intracardiac injection of these cells into an in vivo intracranial glioblastoma murine model.

RESULTS

hAMSCs-BMP4 targeted both the glioblastoma tumor bulk and migratory glioblastoma cells, as well as induced differentiation of BTICs, decreased proliferation, and reduced the migratory capacity of glioblastomas in vitro and in vivo. In addition, hAMSCs-BMP4 significantly prolonged survival in a murine model of glioblastoma. We also demonstrate that the use of hAMSCs in vivo is safe.

CONCLUSIONS

Both unmodified and engineered hAMSCs are nononcogenic and effective against glioblastoma, and hAMSCs-BMP4 are a promising cell-based treatment option for glioblastoma.

Chloroquine inhibits the malignant phenotype of glioblastoma partially by suppressing TGF-beta

BACKGROUND

Glioblastoma (GBM), the most common and aggressive primary brain tumor, is characterized by excessive brain infiltration which prevents the complete surgical resection. These tumors also display treatment non-compliance and responses to standard therapy are invariably transient; consequently, the prognosis barely exceeds 14 months and recurrence is inevitable. Accordingly, several new treatment strategies have been studied. One such option is the use of chloroquine (CQ), a lysosomotropic weak base and renowned antimalarial drug, that has shown promising results in several pre-clinical studies. In this paper, we investigate the efficiency of CQ to hinder the malignant phenotype of GBM, namely extensive proliferation, invasion and radio-resistance.

RESULTS

In cell cycle analysis, proliferation assays and immunofluorescence, CQ treatments halved proliferation of primary cultures from GBM specimens and GBM cell lines (U-373 MG et U-87 MG). Gelatin zymography and Matrigel(TM)-coated transwell invasion assays also revealed a 50 % CQ induced inhibition of MMP-2 activity and GBM invasion. Concomitant treatment with CQ and radiation also radiosensitized GBM cells as shown by an accumulation in the G2/M phase, increased cell death and reduced clonogenic formation. Moreover, radiation-induced invasion was considerably restrained by CQ. We also observe that these effects are owed to CQ-induced inhibition of TGF-β secretion and signaling pathway, a predominant growth factor in GBM progression.

CONCLUSION

These results suggest that CQ, alone or as an adjuvant therapeutic, could be used to inhibit the GBM malignant phenotype and could benefit GBM afflicted patients.

Clinical development of galunisertib (LY2157299 monohydrate), a small molecule inhibitor of transforming growth factor-beta signaling pathway

Transforming growth factor-beta (TGF-β) signaling regulates a wide range of biological processes. TGF-β plays an important role in tumorigenesis and contributes to the hallmarks of cancer, including tumor proliferation, invasion and metastasis, inflammation, angiogenesis, and escape of immune surveillance. There are several pharmacological approaches to block TGF-β signaling, such as monoclonal antibodies, vaccines, antisense oligonucleotides, and small molecule inhibitors. Galunisertib (LY2157299 monohydrate) is an oral small molecule inhibitor of the TGF-β receptor I kinase that specifically downregulates the phosphorylation of SMAD2, abrogating activation of the canonical pathway. Furthermore, galunisertib has antitumor activity in tumor-bearing animal models such as breast, colon, lung cancers, and hepatocellular carcinoma. Continuous long-term exposure to galunisertib caused cardiac toxicities in animals requiring adoption of a pharmacokinetic/pharmacodynamic-based dosing strategy to allow further development. The use of such a pharmacokinetic/pharmacodynamic model defined a therapeutic window with an appropriate safety profile that enabled the clinical investigation of galunisertib. These efforts resulted in an intermittent dosing regimen (14 days on/14 days off, on a 28-day cycle) of galunisertib for all ongoing trials. Galunisertib is being investigated either as monotherapy or in combination with standard antitumor regimens (including nivolumab) in patients with cancer with high unmet medical needs such as glioblastoma, pancreatic cancer, and hepatocellular carcinoma. The present review summarizes the past and current experiences with different pharmacological treatments that enabled galunisertib to be investigated in patients.

The Transcription Factor ZNF395 Is Required for the Maximal Hypoxic Induction of Proinflammatory Cytokines in U87-MG Cells

Hypoxia activates the expression of proangiogenic and survival promoting factors as well as proinflammatory cytokines that support tissue inflammation. Hypoxia and inflammation are associated with tumor progression. The identification of the factors participating in the hypoxia associated inflammation is essential to develop strategies to control tumor hypoxia. The transcription factor ZNF395 was found to be overexpressed in various tumors including glioblastomas particularly in the network of a hypoxic response pointing to a functional role of ZNF395. On the other hand, ZNF395 was suggested to have tumor suppressor activities which may rely on its repression of proinflammatory factors. To address these conflictive observations, we investigated the role of ZNF395 in the expression of proinflammatory cytokines in the astrocytoma cell line U87-MG under hypoxia. We show that ZNF395 is a target gene of the hypoxia inducible factor HIF-1α. By gene expression analysis, RT-PCR and ELISA, we demonstrated that the siRNA-mediated suppression of ZNF395 impairs the hypoxic induction of IL-1β, IL-6, IL-8, and LIF in U87-MG cells. At ambient oxygen concentrations, ZNF395 had no enhancing effect, indicating that this transcriptional activation by ZNF395 is restricted to hypoxic conditions. Our results suggest that ZNF395 contributes to hypoxia associated inflammation by superactivating proinflammatory cytokines.

Aspirin blocks growth of breast tumor cells and tumor-initiating cells and induces reprogramming factors of mesenchymal to epithelial transition

Acetylsalicylic acid (ASA), also known as aspirin, a classic, nonsteroidal, anti-inflammatory drug (NSAID), is widely used to relieve minor aches and pains and to reduce fever. Epidemiological studies and other experimental studies suggest that ASA use reduces the risk of different cancers including breast cancer (BC) and may be used as a chemopreventive agent against BC and other cancers. These studies have raised the tempting possibility that ASA could serve as a preventive medicine for BC. However, lack of in-depth knowledge of the mechanism of action of ASA reshapes the debate of risk and benefit of using ASA in prevention of BC. Our studies, using in vitro and in vivo tumor xenograft models, show a strong beneficial effect of ASA in the prevention of breast carcinogenesis. We find that ASA not only prevents breast tumor cell growth in vitro and tumor growth in nude mice xenograft model through the induction of apoptosis, but also significantly reduces the self-renewal capacity and growth of breast tumor-initiating cells (BTICs)/breast cancer stem cells (BCSCs) and delays the formation of a palpable tumor. Moreover, ASA regulates other pathophysiological events in breast carcinogenesis, such as reprogramming the mesenchymal to epithelial transition (MET) and delaying in vitro migration in BC cells. The tumor growth-inhibitory and reprogramming roles of ASA could be mediated through inhibition of TGF-β/SMAD4 signaling pathway that is associated with growth, motility, invasion, and metastasis in advanced BCs. Collectively, ASA has a therapeutic or preventive potential by attacking possible target such as TGF-β in breast carcinogenesis.

Escaping out of the brain

SUMMARY

Technological development in the field of circulating biomarkers has allowed the identification of circulating tumor cells in the peripheral blood of patients with glioblastoma. This opens a new avenue of research with implications for the understanding and clinical managing of this fatal disease.