Antisense therapeutics for tumor treatment: the TGF-beta2 inhibitor AP 12009 in clinical development against malignant tumors

Optogenetic Control of TGF-β Signaling

Cells employ signaling pathways to make decisions in response to changes in their immediate environment. The Transforming Growth Factor β (TGF-β) signaling pathway plays pivotal roles in regulating many cellular processes, including cell proliferation, differentiation, and migrations. In order to manipulate and explore the dynamic behavior of TGF-β signaling at high spatiotemporal resolution, we developed an optogenetic system (the optoTGFBRs system), in which light is used to control TGF-β signaling precisely in time and space. Here, we describe about experimental details of how to build the optoTGFBRs system and utilize it to manipulate TGF-β signaling in a single cell or a cell population using microscope or LED array, respectively.

Progress in the Use of Antisense Oligonucleotides for Vaccine Improvement

: Antisense oligonucleotides (ASOs) are synthetically prepared short single-stranded deoxynucleotide sequences that have been validated as therapeutic agents and as a valuable tool in molecular driving biology. ASOs can block the expression of specific target genes via complementary hybridization to mRNA. Due to their high specificity and well-known mechanism of action, there has been a growing interest in using them for improving vaccine efficacy. Several studies have shown that ASOs can improve the efficacy of vaccines either by inducing antigen modification such as enhanced expression of immunogenic molecules or by targeting certain components of the host immune system to achieve the desired immune response. However, despite their extended use, some problems such as insufficient stability and low cellular delivery have not been sufficiently resolved to achieve effective and safe ASO-based vaccines. In this review, we analyze the molecular bases and the research that has been conducted to demonstrate the potential use of ASOs in vaccines.

Preclinical murine tumor models: a structural and functional perspective

The goal of this review is to pinpoint the specific features, including the weaknesses, of various tumor models, and to discuss the reasons why treatments that are efficient in murine tumor models often do not work in clinics. In a detailed comparison of transplanted and spontaneous tumor models, we focus on structure-function relationships in the tumor microenvironment. For instance, the architecture of the vascular tree, which depends on whether tumor cells have gone through epithelial-mesenchymal transition, is determinant for the extension of the spontaneous necrosis, and for the intratumoral localization of the immune infiltrate. Another key point is the model-dependent abundance of TGFβ in the tumor, which controls the variable susceptibility of different tumor models to treatments. Grounded in a historical perspective, this review provides a rationale for checking factors that will be key for the transition between preclinical murine models and clinical applications.

Recent Advances in Understanding Mechanisms of TGF Beta Signaling and Its Role in Glioma Pathogenesis

Transforming growth factor beta (TGF-β) signaling is involved in the regulation of proliferation, differentiation and survival/or apoptosis of many cells, including glioma cells. TGF-β acts via specific receptors activating multiple intracellular pathways resulting in phosphorylation of receptor-regulated Smad2/3 proteins that associate with the common mediator, Smad4. Such complex translocates to the nucleus, binds to DNA and regulates transcription of many genes. Furthermore, TGF-β-activated kinase-1 (TAK1) is a component of TGF-β signaling and activates mitogen-activated protein kinase (MAPK) cascades. Negative regulation of TGF-β/Smad signaling may occur through the inhibitory Smad6/7. While genetic alterations in genes related to TGF-β signaling are relatively rare in gliomas, the altered expression of those genes is a frequent event. The increased expression of TGF-β1-3 correlates with a degree of malignancy of human gliomas. TGF-β may contribute to tumor pathogenesis in many ways: by direct support of tumor growth, by maintaining self-renewal of glioma initiating stem cells and inhibiting anti-tumor immunity. Glioma initiating cells are dedifferentiated cells that retain many stem cell-like properties, play a role in tumor initiation and contribute to its recurrence. TGF-β1,2 stimulate expression of the vascular endothelial growth factor as well as the plasminogen activator inhibitor and some metalloproteinases that are involved in vascular remodeling, angiogenesis and degradation of the extracellular matrix. Inhibitors of TGF-β signaling reduce viability and invasion of gliomas in animal models and show a great promise as novel, potential anti-tumor therapeutics.

Antisense Oligonucleotides Targeting Angiogenic Factors as Potential Cancer Therapeutics

Cancer is one of the leading causes of death worldwide, and conventional cancer therapies such as surgery, chemotherapy, and radiotherapy do not address the underlying molecular pathologies, leading to inadequate treatment and tumor recurrence. Angiogenic factors, such as EGF, PDGF, bFGF, TGF-β, TGF-α, VEGF, endoglin, and angiopoietins, play important roles in regulating tumor development and metastasis, and they serve as potential targets for developing cancer therapeutics. Nucleic acid-based therapeutic strategies have received significant attention in the last two decades, and antisense oligonucleotide-mediated intervention is a prominent therapeutic approach for targeted manipulation of gene expression. Clinical benefits of antisense oligonucleotides have been recognized by the U.S. Food and Drug Administration, with full or conditional approval of Vitravene, Kynamro, Exondys51, and Spinraza. Herein we review the scope of antisense oligonucleotides that target angiogenic factors toward tackling solid cancers.

Spatiotemporal Control of TGF-β Signaling with Light

Cells employ signaling pathways to make decisions in response to changes in their immediate environment. Transforming growth factor beta (TGF-β) is an important growth factor that regulates many cellular functions in development and disease. Although the molecular mechanisms of TGF-β signaling have been well studied, our understanding of this pathway is limited by the lack of tools that allow the control of TGF-β signaling with high spatiotemporal resolution. Here, we developed an optogenetic system (optoTGFBRs) that enables the precise control of TGF-β signaling in time and space. Using the optoTGFBRs system, we show that TGF-β signaling can be selectively and sequentially activated in single cells through the modulation of the pattern of light stimulations. By simultaneously monitoring the subcellular localization of TGF-β receptor and Smad2 proteins, we characterized the dynamics of TGF-β signaling in response to different patterns of blue light stimulations. The spatial and temporal precision of light control will make the optoTGFBRs system as a powerful tool for quantitative analyses of TGF-β signaling at the single cell level.

Transforming growth factor-β in stem cells and tissue homeostasis

TGF-β 1-3 are unique multi-functional growth factors that are only expressed in mammals, and mainly secreted and stored as a latent complex in the extracellular matrix (ECM). The biological functions of TGF-β in adults can only be delivered after ligand activation, mostly in response to environmental perturbations. Although involved in multiple biological and pathological processes of the human body, the exact roles of TGF-β in maintaining stem cells and tissue homeostasis have not been well-documented until recent advances, which delineate their functions in a given context. Our recent findings, along with data reported by others, have clearly shown that temporal and spatial activation of TGF-β is involved in the recruitment of stem/progenitor cell participation in tissue regeneration/remodeling process, whereas sustained abnormalities in TGF-β ligand activation, regardless of genetic or environmental origin, will inevitably disrupt the normal physiology and lead to pathobiology of major diseases. Modulation of TGF-β signaling with different approaches has proven effective pre-clinically in the treatment of multiple pathologies such as sclerosis/fibrosis, tumor metastasis, osteoarthritis, and immune disorders. Thus, further elucidation of the mechanisms by which TGF-β is activated in different tissues/organs and how targeted cells respond in a context-dependent way can likely be translated with clinical benefits in the management of a broad range of diseases with the involvement of TGF-β.

TGF-ß isoforms in cancer: Immunohistochemical expression and Smad-pathway-activity-analysis in thirteen major tumor types with a critical appraisal of antibody specificity and immunohistochemistry assay validity

The literature on TGF-Δ in cancer including data on the expression or activation of TGF-Δ pathway components in specific tumors types is steadily growing. However, no systematic and uniform analysis exists reporting expression levels of the main TGF-Δ pathway components across the most frequent tumor types. We used a standardized immunohistochemical assay investigating TGF-Δ isoform expression and pathway activation across 13 different tumor types and corresponding non-neoplastic tissues. The study was performed on tissue microarrays allowing for the parallel analysis of a total of 1638 human tumor samples. TGF-Δ1, TGF-Δ2 and p-Smad2/3 were substantially expressed in multiple cancers widening the options for TGF-Δ isoform directed therapies. Of note, TGF-Δ antigens appear to be expressed in an individual manner pointing towards a need for patient preselection for TGF-β isoform specific treatment. Yet, a thorough investigation of antibody specificity and assay validity revealed that immunohistochemistry did not correlate with other detection methods on mRNA or protein level in all instances. As such, with the currently available means (i.e. antibodies tested) a stratification of patients within clinical trials for TGF-Δ directed antisense therapies based upon TGF-β immunohistochemistry alone has to be interpreted with caution and should be carefully evaluated in combination with other parameters.

What's Next for Gastrointestinal Disorders: No Needles?

A myriad of pathologies affect the gastrointestinal tract, citing this affected area as a significant target for therapeutic intervention. One group of therapeutic agents, antisense and oligonucleotides and small interfering RNAs, offer a promising platform for treating a wide variety of diseases ranging from cancer to auto-immune diseases. Current delivery methods are carried out either systemically or locally into diseased areas, both of which involve needles. The challenge in orally administering this type of treatment lies in the complications that arise due to the vast environmental extremes found within the gastrointestinal tract, owing to the fact that, as the drug travels down the gastrointestinal tract, it is subjected to pH changes and interactions with bacteria and a variety of digestive and protective enzymes including proteases, DNAses, and RNAses. Overcoming these challenges to allow the practical application of these drugs is a priority that has invoked a multitude of research in the chemical, biological, and material sciences. In this review, we will address common gastrointestinal pathologies, the barriers to oral-based therapies and antisense-interfering technologies, the approaches that have already been applied for their delivery, and the current status of antisense drug therapy clinical trials for gastrointestinal-related disorders.

Regulatory T lymphocytes and transforming growth factor beta in epithelial ovarian tumors-prognostic significance

BACKGROUND

Regulatory T lymphocytes (Treg) are characterized by the presence of CD4+ surface antigen. Today the transcription factor FOXP3 is considered to be the most specific marker of Treg cells. The aim of the study was to estimate the percentage of Treg in peripheral blood and the tissue of the epithelial ovarian tumor and blood serum TGF-beta concentrations and relationships between them. Moreover, the aim of the study was to answer the question whether the percentage of Treg lymphocytes affects the time of survival in patients with ovarian cancer.

METHODS

The patients were divided into four groups, depending on the histopathological examination result: I--a group without any pathology within the ovaries (C; n = 20), II--a group with benign tumors (B; n = 25), III - with borderline tumors (BR; n = 11), IV--a group with cancer of the ovary (M; n = 24). The percentage of Treg lymphocytes in peripheral blood and the tissue was assessed using the flow cytometry method. TGF-beta cytokine concentration was estimated with the ELISA immunoenzymatic test. Statistical analysis of the results was conducted using the computer program Statistica 10.0PL (StatSoft, Inc).

RESULTS

No significant differences were found in percentages of Treg lymphocytes in peripheral blood between individual groups of patients (p = 0.11). However, we observed marked differences in the tissue of malignant and non-malignant tumors between individual groups of patients (p = 0.003). The analysis with the post hoc test revealed significantly higher TGF-beta concentration in the group of women with malignant tumors. Moreover, no relationship was found between TGF-beta concentration and the percentage of Treg cells in peripheral blood and tumors of the ovary. No correlation was found between the percentage of Treg lymphocytes in peripheral blood (p = 0.4) and the tissue of ovarian tumors (p = 0.3) and the time of survival of patients with ovarian cancer.

CONCLUSIONS

The recruitment of Treg lymphocytes toward the tumor is one of the mechanisms of escape of neoplasm from the response of the immune system. The percentage of Treg lymphocytes in peripheral blood and the neoplastic tissue does not influence the time of survival of patients with ovarian cancer.

Engineering TGF-β superfamily ligands for clinical applications

TGF-β superfamily ligands govern normal tissue development and homeostasis, and their dysfunction is a hallmark of many diseases. These ligands are also well defined both structurally and functionally. This review focuses on TGF-β superfamily ligand engineering for therapeutic purposes, in particular for regenerative medicine and musculoskeletal disorders. We describe the key discovery that structure-guided mutation of receptor-binding epitopes, especially swapping of these epitopes between ligands, results in new ligands with unique functional properties that can be harnessed clinically. Given the promising results with prototypical engineered TGF-β superfamily ligands, and the vast number of such molecules that remain to be produced and tested, this strategy is likely to hold great promise for the development of new biologics.

Therapeutic modulation of prostate cancer metastasis

Targeting prostate cancer metastasis has very high therapeutic potential. Prostate cancer is the second most common cause of cancer death among men in the USA, and death results from the development of metastatic disease. In order to metastasize, cancer cells must complete a series of steps that together constitute the metastatic cascade. Each step therefore offers the opportunity for therapeutic targeting. However, practical limitations have served as limiting roadblocks to successfully targeting the metastatic cascade. They include our still-emerging understanding of the underlying biology, as well as the fact that many of the dysregulated processes have critical functionality in otherwise normal cells. We provide a discussion of the underlying biology, as it relates to therapeutic targeting. Therapeutic inroads are rapidly being made, and we present a series of case studies to highlight key points. Finally, future perspectives related to drug discovery for antimetastatic agents are discussed.

EW-7197, a novel ALK-5 kinase inhibitor, potently inhibits breast to lung metastasis

Advanced tumors produce an excessive amount of transforming growth factor β (TGFβ), which promotes tumor progression at late stages of malignancy. The purpose of this study was to develop anti-TGFβ therapeutics for cancer. We synthesized a novel small-molecule TGFβ receptor I kinase (activin receptor-like kinase 5) inhibitor termed N-[[4-([1,2,4]triazolo[1,5-a]pyridin-6-yl)-5-(6-methylpyridin-2-yl)-1H-imidazol-2-yl]methyl]-2-fluoroaniline (EW-7197), and we investigated its potential antimetastatic efficacy in mouse mammary tumor virus (MMTV)/c-Neu mice and 4T1 orthotopic-grafted mice. EW-7197 inhibited Smad/TGFβ signaling, cell migration, invasion, and lung metastasis in MMTV/c-Neu mice and 4T1 orthotopic-grafted mice. EW-7197 also inhibited the epithelial-to-mesenchymal transition (EMT) in both TGFβ-treated breast cancer cells and 4T1 orthotopic-grafted mice. Furthermore, EW-7197 enhanced cytotoxic T lymphocyte activity in 4T1 orthotopic-grafted mice and increased the survival time of 4T1-Luc and 4T1 breast tumor-bearing mice. In summary, EW-7197 showed potent in vivo antimetastatic activity, indicating its potential for use as an anticancer therapy.

Chemotherapeutic Targeting of the Transforming Growth Factor-β Pathway in Breast Cancers

Transforming growth factor (TGF-β) is a multifunctional cytokine that plays essential roles in regulating mammary gland development, morphogenesis, differentiation, and involution. TGF-β also regulates mammary gland homeostasis and prevents its transformation by prohibiting dysregulated cell cycle progression, and by inducing apoptosis; it also creates cell microenvironments that readily inhibit cell migration, invasion, and metastasis. Interestingly, while early-stage mammary tumors remain sensitive to the tumor suppressing activities of TGF-β, late-stage breast cancers become insensitive to the anticancer functions of this cytokine and instead rely upon TGF-β to drive disease and metastatic progression. This switch in TGF-β function is known as the "TGF-β Paradox" and represents the rationale for developing chemotherapies to inactivate the TGF-β pathway and its oncogenic functions in late-stage breast cancers. Here we outline the molecular mechanisms that manifest the "TGF-β Paradox" and discuss the challenges associated with the development and use of anti-TGF-β agents to treat breast cancer patients.

TGF-β2: A Novel Target of CD44-Promoted Breast Cancer Invasion

We have developed a tetracycline (tet)-off regulated expression of CD44s gene in the breast cancer (BC) cell line MCF-7 (B5 clone) and identified TGF-β2 (Transforming Growth Factor beta-2; 3 fold induction) as a potential CD44-downstream transcriptional target by microarray analysis. To further validate this finding, the same RNA samples, used for microarray analysis and their corresponding protein lysates, collected from the BC cell line MCF-7-B5, were examined for CD44 expression in the presence of HA. Our results showed that TGF-β2 mRNA levels were significantly elevated following the removal of tetracycline at 18, 24, and 48 h post-HA stimulation compared to the parental cells. Furthermore, the TGF-β2 precursor protein increased in a time-dependent pattern upon HA-stimulation and in the absence of tetracycline. More interestingly, inhibition of CD44 gene by RNAi method decreased TGF-β2 expression upon HA-stimulation, and subsequently inhibited BC cell invasion in vitro. In addition to identifying TGF-β2 as a target for HA/CD44 signaling, this data suggests that ATF/CREB might be a potential transcription factor linking HA/CD44 activation to TGF-β2 transcription and additional experiments are required for a better understanding of the molecular mechanisms underpinning the novel function of the CD44/ TGF-β2 signaling pathway in breast cancer metastasis.

Gene therapy for high-grade glioma

High-grade glioma is the most frequently occurring primary brain tumor and is associated with a poor prognosis. Current treatment regimens have had only a modest effect on the progressive course despite recent advances in surgery, radiotherapy, and chemotherapy. Gene therapy for brain tumors represents a novel and promising therapeutic approach and has been investigated clinically for the last two decades. The strategies of gene therapy include suicide gene therapy, immune gene therapy, oncolytic viral therapy, tumor suppressor gene therapy, and antisense therapy. Here, we review gene therapy approaches considering the clinical results, limitations, and future directions.

Current status of local therapy in malignant gliomas--a clinical review of three selected approaches

Malignant gliomas are the most frequently occurring, devastating primary brain tumors, and are coupled with a poor survival rate. Despite the fact that complete neurosurgical resection of these tumors is impossible in consideration of their infiltrating nature, surgical resection followed by adjuvant therapeutics, including radiation therapy and chemotherapy, is still the current standard therapy. Systemic chemotherapy is restricted by the blood-brain barrier, while methods of local delivery, such as with drug-impregnated wafers, convection-enhanced drug delivery, or direct perilesional injections, present attractive ways to circumvent these barriers. These methods are promising ways for direct delivery of either standard chemotherapeutic or new anti-cancer agents. Several clinical trials showed controversial results relating to the influence of a local delivery of chemotherapy on the survival of patients with both recurrent and newly diagnosed malignant gliomas. Our article will review the development of the drug-impregnated release, as well as convection-enhanced delivery and the direct injection into brain tissue, which has been used predominantly in gene-therapy trials. Further, it will focus on the use of convection-enhanced delivery in the treatment of patients with malignant gliomas, placing special emphasis on potential shortcomings in past clinical trials. Although there is a strong need for new or additional therapeutic strategies in the treatment of malignant gliomas, and although local delivery of chemotherapy in those tumors might be a powerful tool, local therapy is used only sporadically nowadays. Thus, we have to learn from our mistakes in the past and we strongly encourage future developments in this field.

Targeting the TGFβ signalling pathway in disease

Many drugs that target transforming growth factor-β (TGFβ) signalling have been developed, some of which have reached Phase III clinical trials for a number of disease applications. Preclinical and clinical studies indicate the utility of these agents in fibrosis and oncology, particularly in augmentation of existing cancer therapies, such as radiation and chemotherapy, as well as in tumour vaccines. There are also reports of specialized applications, such as the reduction of vascular symptoms of Marfan syndrome. Here, we consider why the TGFβ signalling pathway is a drug target, the potential clinical applications of TGFβ inhibition, the issues arising with anti-TGFβ therapy and how these might be tackled using personalized approaches to dosing, monitoring of biomarkers as well as brief and/or localized drug-dosing regimens.

New therapeutic approaches for malignant glioma: in search of the Rosetta stone

Malignant gliomas are heterogeneous, diffuse and highly infiltrating by nature. Despite wide surgical resection and improvements in radio- and chemotherapies, the prognosis of patients with glioblastoma multiforme remains extremely poor, with a median survival time of only 14.5 months from diagnosis to death. Particular challenges for glioblastoma multiforme therapy are posed by limitations in the extent of feasible surgical resections, distinct tumor heterogeneity, difficulties in drug delivery across the blood-brain barrier and low drug distribution within the tumor. Therefore, new paradigms permitting tumor-specific targeting and extensive intratumoral distribution must be developed to allow an efficient therapeutic delivery. This review highlights the latest advances in the treatment of glioblastoma multiforme and the recent developments that have resulted from the interchange between preclinical and clinical efforts. We also summarize and discuss novel therapies for malignant glioma, focusing on advances in the following main topics of glioblastoma multiforme therapy: immunotherapy, gene therapy, stem cell-based therapies and nanotechnology. We discuss strategies and outcomes of emerging therapeutic approaches in these fields, and the main challenges associated with the integration of discoveries that occur in the laboratory into clinical practice.

Silencing of the TGF-β1 gene increases the immunogenicity of cells from human ovarian carcinoma

Cells from many tumors produce transforming growth factor (TGF)-β which facilitates their escape from control by the immune system. We previously reported that nonimmunogenic cells from either of 2 transplantable mouse tumors became effective as therapeutic tumor vaccines after lentivirus-mediated shRNA interference to "silence" the TGF-β1 gene. We now show that cells from in vitro cultured human ovarian carcinomas (OvC) make large amounts of TGF-β1 and that this can be prevented by "silencing" the TGF-β1 gene. We further show that in vitro sensitization of peripheral blood mononuclear cells in the presence of either mitomycin-treated OvC cells whose TGF-β1 gene was silenced or in vitro matured dendritic cells that had been pulsed with homogenates from OvC cells with silenced TGF-β1 generated a stronger Th1/Tc1 immune response to the respective wild-type OvC and also to the OvC antigens mesothelin and HE4 as measured by ELIspot assays. The percentage of interferon-γ and tumor necrosis factor-α-producing CD4+ and CD8+ T cells increased while there were fewer cells expressing markers characteristic for regulatory T cells or myeloid-derived suppressor cells. Similar results were obtained when peripheral blood mononuclear cells from a patient with OvC were sensitized to dendritic cells pulsed with homogenate from autologous TGF-β1-silenced tumor cells, and a cytolytic lymphocyte response was generated to autologous OvC cells. Our results support clinical evaluation of TGF-β1-silenced tumor vaccines for immunotherapy of OvC.

Crosstalk between TGF-β signaling and the microRNA machinery

The activin/transforming growth factor-β (TGF-β) pathway plays an important role in tumorigenesis either by its tumor suppressor or tumor promoting effect. Loss of members of the TGF-β signaling by somatic mutations or epigenetic events, such as DNA methylation or regulation by microRNA (miRNA), may affect the signaling process. Most members of the TGF-β pathway are known to be targeted by one or more miRNAs. In addition, the biogenesis of miRNAs is also regulated by TGF-β both directly and through SMADs. Based on these interactions, it appears that autoregulatory feedback loops between TGF-β and miRNAs influence the fate of tumor cells. Our aim is to review the crosstalk between TGF-β signaling and the miRNA machinery to highlight potential novel therapeutic targets.

Immunoassay-based proteome profiling of 24 pancreatic cancer cell lines

Pancreatic ductal adenocarcinoma is one of the most deadly forms of cancers, with a mortality that is almost identical to incidence. The inability to predict, detect or diagnose the disease early and its resistance to all current treatment modalities but surgery are the prime challenges to changing the devastating prognosis. Also, relatively little is known about pancreatic carcinogenesis. In order to better understand relevant aspects of pathophysiology, differentiation, and transformation, we analysed the cellular proteomes of 24 pancreatic cancer cell lines and two controls using an antibody microarray that targets 741 cancer-related proteins. In this analysis, 72 distinct disease marker proteins were identified that had not been described before. Additionally, categorizing cancer cells in accordance to their original location (primary tumour, liver metastases, or ascites) was made possible. A comparison of the cells' degree of differentiation (well, moderately, or poorly differentiated) resulted in unique marker sets of high relevance. Last, 187 proteins were differentially expressed in primary versus metastatic cancer cells, of which the majority is functionally related to cellular movement.

Recent developments on immunotherapy for brain cancer

INTRODUCTION

Brain tumors are a unique class of cancers since they are anatomically shielded from normal immunosurveillance by the blood-brain barrier, lack a normal lymphatic drainage system and reside in a potently immunosuppressive environment. Of the primary brain cancers, glioblastoma multiforme (GBM) is the most common and aggressive in adults. Although treatment options include surgery, radiation and chemotherapy, the average lifespan of GBM patients remains at only 14.6 months post-diagnosis.

AREAS COVERED

A review of key cellular and molecular immune system mediators in the context of brain tumors including TGF-β, cytotoxic T cells, Tregs, CTLA-4, PD-1 and IDO is discussed. In addition, prognostic factors, currently utilized immunotherapeutic strategies, ongoing clinical trials and a discussion of new or potential immunotherapies for brain tumor patients are considered.

EXPERT OPINION

Current drugs that improve the quality of life and overall survival in patients with brain tumors, especially for GBM, are poorly effective. This disease requires a reanalysis of currently accepted treatment strategies, as well as newly designed approaches. Here, we review the fundamental aspects of immunosuppression in brain tumors, new and promising immunotherapeutic drugs as well as combinatorial strategies that focus on the simultaneous inhibition of immunosuppressive hubs, both in immune and brain tumor cells, which is critical to consider for achieving future success for the treatment of this devastating disease.

Methodology for Anti-Gene Anti-IGF-I Therapy of Malignant Tumours

The aim of this study was to establish the criteria for methodology of cellular “anti-IGF-I” therapy of malignant tumours and particularly for glioblastoma multiforme. The treatment of primary glioblastoma patients using surgery, radiotherapy, and chemotherapy was followed by subcutaneous injection of autologous cancer cells transfected by IGF-I antisense/triple helix expression vectors. The prepared cell “vaccines” should it be in the case of glioblastomas or other tumours, have shown a change of phenotype, the absence of IGF-I protein, and expression of MHC-I and B7. The peripheral blood lymphocytes, PBL cells, removed after each of two successive vaccinations, have demonstrated for all the types of tumour tested an increasing level of CD8⁺ and CD8⁺28⁺ molecules and a switch from CD8⁺11b⁺ to CD8⁺11. All cancer patients were supervised for up to 19 months, the period corresponding to minimum survival of glioblastoma patients. The obtained results have permitted to specify the common criteria for “anti-IGF-I” strategy: characteristics sine qua non of injected “vaccines” (cloned cells IGF-I(−) and MHC-I(+)) and of PBL cells (CD8⁺ increased level).

Targeting regulatory T cells

Cancers express tumor-associated antigens that should elicit immune response to antagonize the tumor growth, but spontaneous immune rejection of established cancer is rare, suggesting an immunosuppressive environment hindering host antitumor immunity. Among the specific and active tumor-mediated mechanisms, CD4(+)CD25(high) T regulatory cells (Treg) are important mediators of active immune evasion in cancer. In this review, we will discuss Treg subpopulations and the mechanisms of their suppressive functions. Treg depletion improves endogenous antitumor immunity and the efficacy of active immunotherapy in animal models for cancer, suggesting that inhibiting Treg function could also improve the limited successes of human cancer immunotherapy. We will also discuss specific strategies for devising effective cancer immunotherapy targeting Treg.

Regulatory T cells in human ovarian cancer

Multiple layers of suppressive components including regulatory T (T(Reg)) cells, suppressive antigen-presenting cells, and inhibitory cytokines form suppressive networks in the ovarian cancer microenvironment. It has been demonstrated that as a major suppressive element, T(Reg) cells infiltrate tumor, interact with several types of immune cells, and mediate immune suppression through different molecular and cellular mechanisms. In this paper, we focus on human ovarian cancer and will discuss the nature of T(Reg) cells including their subsets, trafficking, expansion, and function. We will briefly review the development of manipulation of T(Reg) cells in preclinical and clinical settings.

Akt/PKB-mediated phosphorylation of Twist1 promotes tumor metastasis via mediating cross-talk between PI3K/Akt and TGF-β signaling axes

Metastatic breast tumor cells display an epithelial-mesenchymal transition (EMT) that increases cell motility, invasion, and dissemination. Although the transcription factor Twist1 has been shown to contribute to EMT and cancer metastasis, the signaling pathways regulating Twist1 activity are poorly understood. Here, we show that Twist1 is ubiquitously phosphorylated in 90% of 1,532 invasive human breast tumors. Akt/protein kinase B (PKB)-mediated Twist1 phosphorylation promotes EMT and breast cancer metastasis by modulating its transcriptional target TGF-β2, leading to enhanced TGF-β receptor signaling, which in turn maintains hyperactive phosphoinositide 3-kinase (PI3K)/Akt signaling. Preventing phosphorylation of Twist1, as well as depletion of TGF-β2, significantly impaired the metastatic potential of cancer cells in vivo, indicating a key role of phosphorylated Twist1 (phospho-Twist1) in mediating cross-talk between the PI3K/Akt and TGF-β/Smad signaling axes that supports metastatic tumor development. Our results describe a novel signaling event linking PI3K/Akt hyperactivation in tumor cells to direct regulation of Twist1 activation and tumor metastasis.

SIGNIFICANCE

We identified the first phospho-Twist1 transcriptional target TGF-β2, which mediates cross-talk between PI3K/Akt and TGF-β signaling and promotes tumor metastasis. Our results thus illustrate a direct role of PI3K/Akt signaling in metastatic cancer development and suggest that Twist1 phosphorylation could be a potential therapeutic target in clinical cancer treatment.

Antisense oligodeoxynucleotide targeting HER2 mRNA sensitized docetaxel in breast cancer treatment

CONTEXT

Human epidermal growth factor receptor 2 (HER2) is one of the oncogenes closely associated with the development and prognosis of breast carcinoma. Down-regulation of HER2 mRNA by antisense oligodeoxynucleotide (ASO) HER2 has been suggested to be a feasible treatment for patients with breast carcinoma.

OBJECTIVE

The antitumor effects of ASO HA6722 were investigated in vitro and in vivo.

MATERIALS AND METHODS

In this study, SK-BR-3, a HER2-overexpressing breast carcinoma cell line, was used as the model for in vitro experiments. Inhibitory effects of the ASO HA6722 were detected by methyl-thiazoldiphenyl tetrazolium (MTT) assay. Meanwhile, HER2 mRNA levels were monitored by reverse transcription polymerase chain reaction (RT-PCR). The in vivo antitumor effects were evaluated in nude mice xenograft model.

RESULTS

Our results showed that HA6722 alone could inhibit the growth of SK-BR-3 cells in a dose-dependent manner with the IC(50) value of 41.8 ± 8.1 nM. In addition, the antitumor effect of docetaxel (TXT) could be sensitized by low dose of HA6722 both in vitro and in vivo, suggesting that ASO HA6722 could inhibit the growth of breast cancer cells and enhance the cytotoxic effects of TXT.

DISCUSSION AND CONCLUSION

The combination treatment of TXT and HA6722 could be a more effective approach for breast cancer treatment. The future study should focus on the antitumor effect in other models.

TGF-β in progression of liver disease

Transforming growth factor-β (TGF-β) is a central regulator in chronic liver disease contributing to all stages of disease progression from initial liver injury through inflammation and fibrosis to cirrhosis and hepatocellular carcinoma. Liver-damage-induced levels of active TGF-β enhance hepatocyte destruction and mediate hepatic stellate cell and fibroblast activation resulting in a wound-healing response, including myofibroblast generation and extracellular matrix deposition. Being recognised as a major profibrogenic cytokine, the targeting of the TGF-β signalling pathway has been explored with respect to the inhibition of liver disease progression. Whereas interference with TGF-β signalling in various short-term animal models has provided promising results, liver disease progression in humans is a process of decades with different phases in which TGF-β or its targeting might have both beneficial and adverse outcomes. Based on recent literature, we summarise the cell-type-directed double-edged role of TGF-β in various liver disease stages. We emphasise that, in order to achieve therapeutic effects, we need to target TGF-β signalling in the right cell type at the right time.

Transforming growth factor-β in the gastrointestinal and hepatic tumor microenvironment

Transforming growth factor (TGF)-β is a multifunctional cytokine that has important roles in tumor formation, progression, and metastasis. TGF-β is overproduced, and its signaling is deregulated, in a variety of human tumors, including colorectal, gastric, pancreatic, and liver. Therapeutics are being developed to block TGF-β signaling. However, TGF-β also functions as a tumor suppressor in premalignant cells. It is not clear how its function changes from that of a tumor suppressor to a tumor promoter; improvements are needed in our understanding of TGF-β functions in tumor development before we can design inhibitors for use as anticancer therapies. TGF-β regulates not only different tumor-cell autonomous signaling pathways, but also interactions between tumor and host cells, through paracrine mechanisms. We review recent findings about how TGF-β is regulated and its roles in the tumor microenvironment and metastasis, with a focus on gastrointestinal cancers. Improved understanding of TGF-β regulation and how it mediates interaction between cancer epithelial cells, immune cells, and fibroblasts will provide important insights into tumor development and progression.

Novel therapeutic approaches for pulmonary fibrosis

Pulmonary fibrosis represents the end stage of a number of heterogeneous conditions and is, to a greater or lesser degree, the hallmark of the interstitial lung diseases. It is characterized by the excessive deposition of extracellular matrix proteins within the pulmonary interstitium leading to the obliteration of functional alveolar units and in many cases, respiratory failure. While a small number of interstitial lung diseases have known aetiologies, most are idiopathic in nature, and of these, idiopathic pulmonary fibrosis is the most common and carries with it an appalling prognosis - median survival from the time of diagnosis is less than 3 years. This reflects the lack of any effective therapy to modify the course of the disease, which in turn is indicative of our incomplete understanding of the pathogenesis of this condition. Current prevailing hypotheses focus on dysregulated epithelial-mesenchymal interactions promoting a cycle of continued epithelial cell injury and fibroblast activation leading to progressive fibrosis. However, it is likely that multiple abnormalities in a myriad of biological pathways affecting inflammation and wound repair - including matrix regulation, epithelial reconstitution, the coagulation cascade, neovascularization and antioxidant pathways - modulate this defective crosstalk and promote fibrogenesis. This review aims to offer a pathogenetic rationale behind current therapies, briefly outlining previous and ongoing clinical trials, but will focus on recent and exciting advancements in our understanding of the pathogenesis of idiopathic pulmonary fibrosis, which may ultimately lead to the development of novel and effective therapeutic interventions for this devastating condition.

Oligonucleotide Therapeutics

The idea of sequence-specific gene silencing by synthetic oligonucleotides targeting mRNA is at least 40 years old, but it was only in the mid-1980s when technical advances made the chemical synthesis of oligonucleotides possible that practical steps could be taken toward its implementation. The result was a deluge of experimental data in a variety of systems [1], most of which employed the phosphorothioate (PS) backbone modification, and much of which was ultimately, and unfortunately, uninterpretable.

Dexamethasone differentially regulates functional membrane properties in glioma cell lines and primary astrocytes in vitro

Similar to astrocytes, glioma cells form a well-coupled syncytium via gap junctions. This can be influenced, for example, by activated microglia, the main inflammatory cell population within the central nervous system (CNS). Under pathological conditions such as neoplastic cell growth, microglia number and activation state are enhanced. The aim of the present study is to analyze the influence of dexamethasone (DEX) on cellular and molecular properties in glial coculture models consisting of astroglia and microglia and human and rat glioma cell lines. Primary rat glial cocultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) microglia as well as rat and human glioma cell lines (F98, C6, U87) were incubated with DEX for 24 h. DEX-treated M30 cocultures showed significant increased gap junctional intercellular communication (GJIC). DEX treatment of glioma cells resulted in depolarization of the membrane resting potential (MRP) and a significant reduction of GJIC. Furthermore, DEX reduced the amount of activated microglia in M30 cocultures. DEX had no significant effects on the tested variables in the M5 coculture. DEX differentially regulates functional membrane properties of glioma cells and astrocytes in primary glial cocultures, which might resemble steroid effects in glioma cells and adjacent glial components in vivo.

The dynamic roles of TGF-β in cancer

The transforming growth factor-β (TGF-β) signalling pathway plays a critical and dual role in the progression of human cancer. During the early phase of tumour progression, TGF-β acts as a tumour suppressor, exemplified by deletions or mutations in the core components of the TGF-β signalling pathway. On the contrary, TGF-β also promotes processes that support tumour progression such as tumour cell invasion, dissemination, and immune evasion. Consequently, the functional outcome of the TGF-β response is strongly context-dependent including cell, tissue, and cancer type. In this review, we describe the molecular signalling pathways employed by TGF-β in cancer and how these, when perturbed, may lead to the development of cancer. Concomitantly with our increased appreciation of the molecular mechanisms that govern TGF-β signalling, the potential to therapeutically target specific oncogenic sub-arms of the TGF-β pathway increases. Indeed, clinical trials with systemic TGF-β signalling inhibitors for treatment of cancer patients have been initiated. However, considering the important role of TGF-β in cardiovascular and many other tissues, careful screening of patients is warranted to minimize unwanted on-target side effects.

Nanoparticle delivery systems in cancer vaccines

Therapeutic strategies that involve the manipulation of the host's immune system are gaining momentum in cancer research. Antigen-loaded nanocarriers are capable of being actively taken up by antigen-presenting cells (APCs) and have shown promising potential in cancer immunotherapy by initiating a strong immunostimulatory cascade that results in potent antigen-specific immune responses against the cancer. Such carrier systems offer versatility in that they can simultaneously co-deliver adjuvants with the antigens to enhance APC activation and maturation. Furthermore, modifying the surface properties of these nanocarriers affords active targeting properties to APCs and/or enhanced accumulation in solid tumors. Here, we review some recent advances in these colloidal and particulate nanoscale systems designed for cancer immunotherapy and the potential for these systems to translate into clinical cancer vaccines.

ROS accumulation and IGF-IR inhibition contribute to fenofibrate/PPARalpha -mediated inhibition of glioma cell motility in vitro

BACKGROUND

Glioblastomas are characterized by rapid cell growth, aggressive CNS infiltration, and are resistant to all known anticancer regimens. Recent studies indicate that fibrates and statins possess anticancer potential. Fenofibrate is a potent agonist of peroxisome proliferator activated receptor alpha (PPARalpha) that can switch energy metabolism from glycolysis to fatty acid beta-oxidation, and has low systemic toxicity. Fenofibrate also attenuates IGF-I-mediated cellular responses, which could be relevant in the process of glioblastoma cell dispersal.

METHODS

The effects of fenofibrate on Glioma cell motility, IGF-I receptor (IGF-IR) signaling, PPARalpha activity, reactive oxygen species (ROS) metabolism, mitochondrial potential, and ATP production were analyzed in human glioma cell lines.

RESULTS

Fenofibrate treatment attenuated IGF-I signaling responses and repressed cell motility of LN-229 and T98G Glioma cell lines. In the absence of fenofibrate, specific inhibition of the IGF-IR had only modest effects on Glioma cell motility. Further experiments revealed that PPARalpha-dependent accumulation of ROS is a strong contributing factor in Glioma cell lines responses to fenofibrate. The ROS scavenger, N-acetyl-cysteine (NAC), restored cell motility, improved mitochondrial potential, and increased ATP levels in fenofibrate treated Glioma cell lines.

CONCLUSIONS

Our results indicate that although fenofibrate-mediated inhibition of the IGF-IR may not be sufficient in counteracting Glioma cell dispersal, PPARalpha-dependent metabolic switch and the resulting ROS accumulation strongly contribute to the inhibition of these devastating brain tumor cells.

Connection between inflammation and carcinogenesis in gastrointestinal tract: Focus on TGF-β signaling

Inflammation is a primary defense process against various extracellular stimuli, such as viruses, pathogens, foods, and environmental pollutants. When cells respond to stimuli for short periods of time, it results in acute or physiological inflammation. However, if the stimulation is sustained for longer time or a pathological state occurs, it is known as chronic or pathological inflammation. Several studies have shown that tumorigenesis in the gastrointestinal (GI) tract is closely associated with chronic inflammation, for which abnormal cellular alterations that accompany chronic inflammation such as oxidative stresses, gene mutations, epigenetic changes, and inflammatory cytokines, are shared with carcinogenic processes, which forms a critical cross-link between chronic inflammation and carcinogenesis. Transforming growth factor (TGF)-β is a multi-potent cytokine that plays an important role in regulation of cell growth, apoptosis and differentiation. Most importantly, TGF-β is a strong anti-inflammatory cytokine that regulates the development of effector cells. TGF-β has a suppressive effect on carcinogenesis under normal conditions by inhibiting abnormal cell growth, but on the other hand, many GI cancers originate from uncontrolled cell growth and differentiation by genetic loss of TGF-β signaling molecules or perturbation of TGF-β adaptors. Once a tumor has developed, TGF-β exerts a promoting effect on the tumor itself and stromal cells to enhance cell growth, alter the responsiveness of tumor cells to stimulate invasion and metastasis, and inhibited immune surveillance. Therefore, novel development of therapeutic agents to inhibit TGF-β-induced progression of tumor and to retain its growth inhibitory activities, in addition to anti-inflammatory actions, could be useful in oncology. In this review, we discuss the role of TGF-β in inflammation and carcinogenesis of the GI tract related to abnormal TGF-β signaling.

Targeting the transforming growth factor-beta signalling pathway in metastatic cancer

Transforming growth factor (TGF)-beta signalling plays a dichotomous role in tumour progression, acting as a tumour suppressor early and as a pro-metastatic pathway in late-stages. There is accumulating evidence that advanced-stage tumours produce excessive levels of TGF-beta, which acts to promote tumour growth, invasion and colonisation of secondary organs. In light of the pro-metastasis function, many strategies are currently being explored to antagonise the TGF-beta pathway as a treatment for metastatic cancers. Strategies such as using large molecule ligand traps, reducing the translational efficiency of TGF-beta ligands using antisense technology, and antagonising TGF-beta receptor I/II kinase function using small molecule inhibitors are the most prominent methods being explored today. Administration of anti-TGF-beta therapies alone, or in combination with immunosuppressive or cytotoxic therapies, has yielded promising results in the preclinical and clinical settings. Despite these successes, the temporal- and context-dependent roles of TGF-beta signalling in cancer has made it challenging to define patient subgroups that are most likely to respond, and the therapeutic regimens that will be most effective in the clinic. Novel mouse models and diagnostic tools are being developed today to circumvent these issues, which may potentially expedite anti-TGF-beta drug development and clinical application.

Targeting the transforming growth factor-beta signaling pathway in human cancer

The transforming growth factor-ss (TGF-beta) signaling pathway plays a pivotal role in diverse cellular processes. TGF-beta switches its role from a tumor suppressor in normal or dysplastic cells to a tumor promoter in advanced cancers. It is widely believed that the Smad-dependent pathway is involved in TGF-beta tumor-suppressive functions, whereas activation of Smad-independent pathways, coupled with the loss of tumor-suppressor functions of TGF-beta, is important for its pro-oncogenic functions. TGF-beta signaling has been considered a useful therapeutic target. The discovery of oncogenic actions of TGF-beta has generated a great deal of enthusiasm for developing TGF-beta signaling inhibitors for the treatment of cancer. The challenge is to identify the group of patients where targeted tumors are not only refractory to TGF-beta-induced tumor suppressor functions but also responsive to the tumor-promoting effects of TGF-beta. TGF-beta pathway inhibitors, including small and large molecules, have now entered clinical trials. Preclinical studies with these inhibitors have shown promise in a variety of different tumor models. Here, we focus on the mechanisms of signaling and specific targets of the TGF-beta pathway that are critical effectors of tumor progression and invasion. This report also examines the therapeutic intervention of TGF-ss signaling in human cancers.

Strategies for TGF-beta modulation: a review of recent patents

BACKGROUND

TGF-beta has been identified as a key factor in the progression of various diseases, in particular cancer and fibrosis. The signaling of TGF-beta can be modulated through three distinct strategies: using antisense nucleotides that block TGF-beta mRNA (trabedersen (AP 12009)), using monoclonal antibodies to block TGF-beta isoforms (lerdelimumab, metelimumab) or using small molecule inhibitors of the TGF-beta receptor 1 (TGF-betaR1 or ALK-5).

OBJECTIVE

This review focuses on small molecules and summarizes the most recent TGF-betaR1 inhibitors reported in the patent literature.

METHODS

We searched and analyzed the patent literature claiming chemical matter for TGF-betaR1 inhibition from the 1(st) of January 2005 to the 1(st) of January 2009.

RESULTS/CONCLUSIONS

The inhibition of TGF-beta has recently been clinically validated with antisense nucleotide trabedersen. Small molecules inhibitors of TGF-betaR1 that are now in Phase I clinical trials and in preclinical stage are, therefore, of high interest and could provide a more versatile route to TGF-beta modulation through oral dosing while maintaining the same therapeutic benefits.

Future of convection-enhanced delivery in the treatment of brain tumors

Gliomas are one of the most lethal forms of cancer. The poor prognosis associated with these malignant primary brain tumors treated with surgery, radiotherapy and chemotherapy has led researchers to develop new strategies for cure. Interstitial drug delivery has been the most appealing method for the treatment of primary brain tumors because it provides the most direct method of overcoming the barriers to tumor drug delivery. By administering therapeutic agents directly to the brain interstitium and, more specifically, to tumor-infiltrated parenchyma, one can overcome the elevated interstitial pressure produced by brain tumors. Convection-enhanced delivery (CED) has emerged as a leading investigational delivery technique for the treatment of brain tumors. Clinical trials utilizing these methods have been completed, with mixed results, and several more are being initiated. However, the potential efficacy of these drugs may be limited by ineffective tissue distribution. The development of computer models/algorithms to predict drug distribution, new catheter designs, and utilization of tracer models and nanocarriers have all laid the groundwork for the advancement of CED. In this review, we summarize the recent past of the clinical trials utilizing CED and discuss emerging technologies that will shape future CED trials.

Cancer and pregnancy: parallels in growth, invasion, and immune modulation and implications for cancer therapeutic agents

Many proliferative, invasive, and immune tolerance mechanisms that support normal human pregnancy are also exploited by malignancies to establish a nutrient supply and evade or edit the host immune response. In addition to the shared capacity for invading through normal tissues, both cancer cells and cells of the developing placenta create a microenvironment supportive of both immunologic privilege and angiogenesis. Systemic alterations in immunity are also detectable, particularly with respect to a helper T cell type 2 polarization evident in advanced cancers and midtrimester pregnancy. This review summarizes the similarities between growth and immune privilege in cancer and pregnancy and identifies areas for further investigation. Our PubMed search strategy included combinations of terms such as immune tolerance, pregnancy, cancer, cytokines, angiogenesis, and invasion. We did not place any restrictions on publication dates. The knowledge gained from analyzing similarities and differences between the physiologic state of pregnancy and the pathologic state of cancer could lead to identification of new potential targets for cancer therapeutic agents.

Novel drug delivery strategies in neuro-oncology

Treatment of malignant gliomas represents one of the most formidable challenges in oncology. Despite treatment with surgery, radiation therapy, and chemotherapy, the prognosis remains poor, particularly for glioblastoma, which has a median survival of 12 to 15 months. An important impediment to finding effective treatments for malignant gliomas is the presence of the blood brain barrier, which serves to prevent delivery of potentially active therapeutic compounds. Multiple efforts are focused on developing strategies to effectively deliver active drugs to brain tumor cells. Blood brain barrier disruption and convection-enhanced delivery have emerged as leading investigational delivery techniques for the treatment of malignant brain tumors. Clinical trials using these methods have been completed, with mixed results, and several more are being initiated. In this review, we describe the clinically available methods used to circumvent the blood brain barrier and summarize the results to date of ongoing and completed clinical trials.

Novel drug delivery strategies in neuro-oncology

Treatment of malignant gliomas represents one of the most formidable challenges in oncology. Despite treatment with surgery, radiation therapy, and chemotherapy, the prognosis remains poor, particularly for glioblastoma, which has a median survival of 12 to 15 months. An important impediment to finding effective treatments for malignant gliomas is the presence of the blood brain barrier, which serves to prevent delivery of potentially active therapeutic compounds. Multiple efforts are focused on developing strategies to effectively deliver active drugs to brain tumor cells. Blood brain barrier disruption and convection-enhanced delivery have emerged as leading investigational delivery techniques for the treatment of malignant brain tumors. Clinical trials using these methods have been completed, with mixed results, and several more are being initiated. In this review, we describe the clinically available methods used to circumvent the blood brain barrier and summarize the results to date of ongoing and completed clinical trials.

Novel therapeutic targets along the Th17 pathway

The recent discovery of IL-17-producing CD4(+) Th subset significantly revised the Th1/Th2 dichotomy model proposed by Mosmann and Coffman almost two decades ago. Th17 cells are involved in the pathogenesis of many human autoimmune diseases. Th17 cells, their developmental pathways and their effector functions, therefore, provide novel therapeutic targets.