Targeting the insulin-like growth factor-1 receptor by picropodophyllin as a treatment option for glioblastoma

Metabolic imbalance and brain tumors: The interlinking metabolic pathways and therapeutic actions of antidiabetic drugs

Brain tumors are complex, heterogeneous malignancies, often associated with significant morbidity and mortality. Emerging evidence suggests the important role of metabolic syndrome, such as that observed in diabetes mellitus, in the progression of brain tumors. Several studies indicated that hyperglycemia, insulin resistance, oxidative stress, and altered adipokine profiles influence tumor growth, proliferation, and treatment resistance. Intriguingly, antidiabetic drugs (e.g., metformin, sulfonylureas, dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, and thiazolidinediones) have shown promise as adjunctive or repurposed agents in managing brain tumors. Metformin can impair tumor cell proliferation, enhance treatment sensitivity, and modify the tumor microenvironment by activating AMP-activated protein kinase (AMPK) and inhibiting mammalian target of rapamycin (mTOR) signaling pathways. DPP-4 inhibitors and GLP-1 receptor agonists can target both metabolic and inflammatory aspects of brain tumors, while thiazolidinediones may induce apoptosis in tumor cells and synergize with other therapeutics. Consequently, further studies and clinical trials are needed to confirm the efficacy, safety, and utility of metabolic interventions in treating brain tumors. Here, we review the evidence for the metabolic interconnections between metabolic diseases and brain tumors and multiple actions of anti-diabetes drugs in brain tumors.

Targeting HSP90 with picropodophyllin suppresses gastric cancer tumorigenesis by disrupting the association of HSP90 and AKT

Gastric cancer (GC) is one of the most common malignant tumors worldwide. Thus, the development of safe and effective therapeutic compounds for GC treatment is urgently required. Here, we aimed to examine the role of picropodophyllin (PPP), a compound extracted from the rhizome of Dysosma versipellis (Hance) M. Cheng ex Ying, on the proliferation of GC cells. Our study revealed that PPP inhibits the proliferation of GC cells in a dose-dependent manner by inducing apoptosis. Moreover, our study elucidated that PPP suppresses the growth of GC tumor xenografts with no side effects of observable toxicity. Mechanistically, PPP exerts its effects by blocking the AKT/mammalian target of rapamycin (mTOR) signaling pathway; these effects are markedly abrogated by the overexpression of constitutively active AKT. Furthermore, drug affinity responsive target stability (DARTS) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) revealed that heat shock protein 90 (HSP90) may be a potential target of PPP. Surface plasmon resonance and immunoprecipitation assay validated that PPP directly targets HSP90 and disrupts the binding of HSP90 to AKT, thereby suppressing GC cell proliferation. Thus, our study revealed that PPP may be a promising therapeutic compound for GC treatment.

Identification of Promising Drug Candidates against Prostate Cancer through Computationally-Driven Drug Repurposing

Prostate cancer (PC) is one of the most common types of cancer in males. Although early stages of PC are generally associated with favorable outcomes, advanced phases of the disease present a significantly poorer prognosis. Moreover, currently available therapeutic options for the treatment of PC are still limited, being mainly focused on androgen deprivation therapies and being characterized by low efficacy in patients. As a consequence, there is a pressing need to identify alternative and more effective therapeutics. In this study, we performed large-scale 2D and 3D similarity analyses between compounds reported in the DrugBank database and ChEMBL molecules with reported anti-proliferative activity on various PC cell lines. The analyses included also the identification of biological targets of ligands with potent activity on PC cells, as well as investigations on the activity annotations and clinical data associated with the more relevant compounds emerging from the ligand-based similarity results. The results led to the prioritization of a set of drugs and/or clinically tested candidates potentially useful in drug repurposing against PC.

Diabetes Mellitus Management in the Context of Cranial Tumors

The study of the relationship between cancer and diabetes mellitus (DM) has been under investigation for many decades. Particularly in the field of neurology and neurosurgery, increasing emphasis has been put on the examination of comorbid DM in patients with cranial tumors. Namely, as the most common and invasive type of malignant adult brain tumor, glioblastoma (GBS) has been the focus of said research. Several mechanisms have been described in the attempt to elucidate the underlying association between DM and GBS, with the metabolic phenomenon known as the Warburg effect and its consequential downstream effects serving as the resounding culprits in recent literature. Since the effect seen in cancers like GBS exploits an upregulated form of aerobic glycolysis, the role of a sequela of DM, known as hyperglycemia, will be investigated. In particular, in the treatment of GBS, surgical resection and subsequent chemotherapy and/or radiotherapy are used in conjunction with corticosteroid therapy, the latter of which has been linked to hyperglycemia. Unsurprisingly, comorbid DM patients are significantly susceptible to this disposition. Further, this fact is reflected in recent literature that demonstrates the impact of hyperglycemia on cancer advancement and patient outcomes in several preclinical and clinical studies. Thus, this review will aim to underline the significance of diabetes and glycemic control via standard-of-care treatments such as metformin administration, as well as to describe emerging treatments such as the signaling modulation of insulin-like growth factor and the employment of the ketogenic diet.

Phytochemicals as Chemo-Preventive Agents and Signaling Molecule Modulators: Current Role in Cancer Therapeutics and Inflammation

Cancer is one of the deadliest non communicable diseases. Numerous anticancer medications have been developed to target the molecular pathways driving cancer. However, there has been no discernible increase in the overall survival rate in cancer patients. Therefore, innovative chemo-preventive techniques and agents are required to supplement standard cancer treatments and boost their efficacy. Fruits and vegetables should be tapped into as a source of compounds that can serve as cancer therapy. Phytochemicals play an important role as sources of new medication in cancer treatment. Some synthetic and natural chemicals are effective for cancer chemoprevention, i.e., the use of exogenous medicine to inhibit or impede tumor development. They help regulate molecular pathways linked to the development and spread of cancer. They can enhance antioxidant status, inactivating carcinogens, suppressing proliferation, inducing cell cycle arrest and death, and regulating the immune system. While focusing on four main categories of plant-based anticancer agents, i.e., epipodophyllotoxin, camptothecin derivatives, taxane diterpenoids, and vinca alkaloids and their mode of action, we review the anticancer effects of phytochemicals, like quercetin, curcumin, piperine, epigallocatechin gallate (EGCG), and gingerol. We examine the different signaling pathways associated with cancer and how inflammation as a key mechanism is linked to cancer growth.

Brain Tumor Networks in Diffuse Glioma

Diffuse gliomas are primary brain tumors associated with a poor prognosis. Cellular and molecular mechanisms driving the invasive growth patterns and therapeutic resistance are incompletely understood. The emerging field of cancer neuroscience offers a novel approach to study these brain tumors in the context of their intricate interactions with the nervous system employing and combining methodological toolsets from neuroscience and oncology. Increasing evidence has shown how neurodevelopmental and neuronal-like mechanisms are hijacked leading to the discovery of multicellular brain tumor networks. Here, we review how gap junction-coupled tumor-tumor-astrocyte networks, as well as synaptic and paracrine neuron-tumor networks drive glioma progression. Molecular mechanisms of these malignant, homo- and heterotypic networks, and their complex interplay are reviewed. Lastly, potential clinical-translational implications and resulting therapeutic strategies are discussed.

A Role for Insulin-like Growth Factor 1 in the Generation of Epileptic Spasms in a murine model

OBJECTIVE

Infantile spasms are associated with a wide variety of clinical conditions, including perinatal brain injuries. We have created a model in which prolonged infusion of tetrodotoxin (TTX) into the neocortex, beginning in infancy, produces a localized lesion and reproduces the behavioral spasms, electroencephalogram (EEG) abnormalities, and drug responsiveness seen clinically. Here, we undertook experiments to explore the possibility that the growth factor IGF-1 plays a role in generating epileptic spasms.

METHODS

We combined long-term video EEG recordings with quantitative immunohistochemical and biochemical analyses to unravel IGF-1's role in spasm generation. Immunohistochemistry was undertaken in surgically resected tissue from infantile spasms patients. We used viral injections in neonatal conditional IGF-1R knock-out mice to show that an IGF-1-derived tripeptide (1-3)IGF-1, acts through the IGF-1 receptor to abolish spasms.

RESULTS

Immunohistochemical methods revealed widespread loss of IGF-1 from cortical neurons, but an increase in IGF-1 in the reactive astrocytes in the TTX-induced lesion. Very similar changes were observed in the neocortex from patients with spasms. In animals, we observed reduced signaling through the IGF-1 growth pathways in areas remote from the lesion. To show the reduction in IGF-1 expression plays a role in spasm generation, epileptic rats were treated with (1-3)IGF-1. We provide 3 lines of evidence that (1-3)IGF-1 activates the IGF-1 signaling pathway by acting through the receptor for IGF-1. Treatment with (1-3)IGF-1 abolished spasms and hypsarrhythmia-like activity in the majority of animals.

INTERPRETATION

Results implicate IGF-1 in the pathogenesis of infantile spasms and IGF-1 analogues as potential novel therapies for this neurodevelopmental disorder. ANN NEUROL 2022;92:45-60.

Therapeutic Options in Neuro-Oncology

One of the biggest challenges in neuro-oncology is understanding the complexity of central nervous system tumors, such as gliomas, in order to develop suitable therapeutics. Conventional therapies in malignant gliomas reconcile surgery and radiotherapy with the use of chemotherapeutic options such as temozolomide, chloroethyl nitrosoureas and the combination therapy of procarbazine, lomustine and vincristine. With the unraveling of deregulated cancer cell signaling pathways, targeted therapies have been developed. The most affected signaling pathways in glioma cells involve tyrosine kinase receptors and their downstream pathways, such as the phosphatidylinositol 3-kinases (PI3K/AKT/mTOR) and mitogen-activated protein kinase pathways (MAPK). MAPK pathway inhibitors include farnesyl transferase inhibitors, Ras kinase inhibitors and mitogen-activated protein extracellular regulated kinase (MEK) inhibitors, while PI3K/AKT/mTOR pathway inhibitors are divided into pan-inhibitors, PI3K/mTOR dual inhibitors and AKT inhibitors. The relevance of the immune system in carcinogenesis has led to the development of immunotherapy, through vaccination, blocking of immune checkpoints, oncolytic viruses, and adoptive immunotherapy using chimeric antigen receptor T cells. In this article we provide a comprehensive review of the signaling pathways underlying malignant transformation, the therapies currently used in the treatment of malignant gliomas and further explore therapies under development, including several ongoing clinical trials.

DNA Damage Response in Glioblastoma: Mechanism for Treatment Resistance and Emerging Therapeutic Strategies

ABSTRACT

Glioblastoma (GBM) is an intrinsically treatment-resistant tumor and has been shown to upregulate DNA damage response (DDR) components after treatment. DNA damage response signaling mediates treatment resistance by promoting cell cycle arrest in order to allow for DNA damage repair and avoid mitotic catastrophe. Therefore, targeting the DDR pathway is an attractive strategy to combat treatment resistance in GBM. In this review, we discuss the different DDR pathways and then summarize the current preclinical evidence for DDR inhibitors in GBM, as well as completed and ongoing clinical trials.

Novel Receptor Tyrosine Kinase Pathway Inhibitors for Targeted Radionuclide Therapy of Glioblastoma

Glioblastoma (GB) remains the most fatal brain tumor characterized by a high infiltration rate and treatment resistance. Overexpression and/or mutation of receptor tyrosine kinases is common in GB, which subsequently leads to the activation of many downstream pathways that have a critical impact on tumor progression and therapy resistance. Therefore, receptor tyrosine kinase inhibitors (RTKIs) have been investigated to improve the dismal prognosis of GB in an effort to evolve into a personalized targeted therapy strategy with a better treatment outcome. Numerous RTKIs have been approved in the clinic and several radiopharmaceuticals are part of (pre)clinical trials as a non-invasive method to identify patients who could benefit from RTKI. The latter opens up the scope for theranostic applications. In this review, the present status of RTKIs for the treatment, nuclear imaging and targeted radionuclide therapy of GB is presented. The focus will be on seven tyrosine kinase receptors, based on their central role in GB: EGFR, VEGFR, MET, PDGFR, FGFR, Eph receptor and IGF1R. Finally, by way of analyzing structural and physiological characteristics of the TKIs with promising clinical trial results, four small molecule RTKIs were selected based on their potential to become new therapeutic GB radiopharmaceuticals.

Targeting RTK-PI3K-mTOR Axis in Gliomas: An Update

Gliomas are the most common and challenging malignancies of the central nervous system (CNS), due to their infiltrative nature, tendency to recurrence, and poor response to treatments. Indeed, despite the advances in neurosurgical techniques and in radiation therapy, the modest effects of therapy are still challenging. Moreover, tumor recurrence is associated with the onset of therapy resistance; it is therefore critical to identify effective and well-tolerated pharmacological approaches capable of inducing durable responses in the appropriate patient groups. Molecular alterations of the RTK/PI3K/Akt/mTOR signaling pathway are typical hallmarks of glioma, and several clinical trials targeting one or more players of this axis have been launched, showing disappointing results so far, due to the scarce BBB permeability of certain compounds or to the occurrence of resistance/tolerance mechanisms. However, as RTK/PI3K/mTOR is one of the pivotal pathways regulating cell growth and survival in cancer biology, targeting still remains a strong rationale for developing strategies against gliomas. Future rigorous clinical studies, aimed at addressing the tumor heterogeneity, the interaction with the microenvironment, as well as diverse posology adjustments, are needed-which might unravel the therapeutic efficacy and response prediction of an RTK/PI3K/mTOR-based approach.

N-cadherin upregulation mediates adaptive radioresistance in glioblastoma

Glioblastoma (GBM) is composed of heterogeneous tumor cell populations, including those with stem cell properties, termed glioma stem cells (GSCs). GSCs are innately less radiation sensitive than the tumor bulk and are believed to drive GBM formation and recurrence after repeated irradiation. However, it is unclear how GSCs adapt to escape the toxicity of repeated irradiation used in clinical practice. To identify important mediators of adaptive radioresistance in GBM, we generated radioresistant human and mouse GSCs by exposing them to repeat cycles of irradiation. Surviving subpopulations acquired strong radioresistance in vivo, which was accompanied by a reduction in cell proliferation and an increase in cell-cell adhesion and N-cadherin expression. Increasing N-cadherin expression rendered parental GSCs radioresistant, reduced their proliferation, and increased their stemness and intercellular adhesive properties. Conversely, radioresistant GSCs lost their acquired phenotypes upon CRISPR/Cas9-mediated knockout of N-cadherin. Mechanistically, elevated N-cadherin expression resulted in the accumulation of β-catenin at the cell surface, which suppressed Wnt/β-catenin proliferative signaling, reduced neural differentiation, and protected against apoptosis through Clusterin secretion. N-cadherin upregulation was induced by radiation-induced IGF1 secretion, and the radiation resistance phenotype could be reverted with picropodophyllin, a clinically applicable blood-brain-barrier permeable IGF1 receptor inhibitor, supporting clinical translation.

Receptor Tyrosine Kinase Signaling and Targeting in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is amongst the deadliest of human cancers, with a median survival rate of just over one year following diagnosis. Characterized by rapid proliferation and diffuse infiltration into the brain, GBM is notoriously difficult to treat, with tumor cells showing limited response to existing therapies and eventually developing resistance to these interventions. As such, there is intense interest in better understanding the molecular alterations in GBM to guide the development of more efficient targeted therapies. GBM tumors can be classified into several molecular subtypes which have distinct genetic signatures, and they show aberrant activation of numerous signal transduction pathways, particularly those connected to receptor tyrosine kinases (RTKs) which control glioma cell growth, survival, migration, invasion, and angiogenesis. There are also non-canonical modes of RTK signaling found in GBM, which involve G-protein-coupled receptors and calcium channels. This review uses The Cancer Genome Atlas (TCGA) GBM dataset in combination with a data-mining approach to summarize disease characteristics, with a focus on select molecular pathways that drive GBM pathogenesis. We also present a unique genomic survey of RTKs that are frequently altered in GBM subtypes, as well as catalog the GBM disease association scores for all RTKs. Lastly, we discuss current RTK targeted therapies and highlight emerging directions in GBM research.

Prognostic and Therapeutic Roles of the Insulin Growth Factor System in Glioblastoma

Glioblastoma multiforme (GBM) is the most common primary brain malignancy and is often resistant to conventional treatments due to its extensive cellular heterogeneity. Thus, the overall survival of GBM patients remains extremely poor. Insulin-like growth factor (IGF) signaling entails a complex system that is a key regulator of cell transformation, growth and cell-cycle progression. Hence, its deregulation is frequently involved in the development of several cancers, including brain malignancies. In GBM, differential expression of several IGF system components and alterations of this signaling axis are linked to significantly worse prognosis and reduced responsiveness to temozolomide, the most commonly used pharmacological agent for the treatment of the disease. In the present review we summarize the biological role of the IGF system in the pathogenesis of GBM and comprehensively discuss its clinical significance and contribution to the development of resistance to standard chemotherapy and experimental treatments.

Inhibition of miR-129 Improves Neuronal Pyroptosis and Cognitive Impairment Through IGF-1/GSK3β Signaling Pathway: An In Vitro and In Vivo Study

Pyroptosis is a programmed cell death process which is accompanied by inflammation. The aims of this in vitro and in vivo study were to reveal whether miR-129 contributed to neuronal pyroptosis and cognitive impairment and to further explore its mechanism involved. PC-12 cells were treated with LPS, miR-129 antagomir, AXL1717 (IGF-1 receptor blocker), or SB216763 (GSK3β blocker). After that, expression of miR-129 was measured using qRT-PCR. Relationship between miR-129 and IGF-1 was revealed using luciferase reporter assay. Protein expression of IGF-1, p-Ser9-GSK3β, NLRP3, and Caspase-1 was determined using western blotting. Pyroptosis rate was measured using flow cytometry. Wistar rats were fed with high-fat diet to induce neural inflammation and were further treated with miR-129 antagomir through intracerebroventricular injection. Then, cognitive impairment was assessed by water maze test. Expression of the proteins mentioned above was measured again in midbrain and hippocampus of the rats. In the PC-12 cells, LPS-induced neuronal pyroptosis can be alleviated by miR-129 antagomir. IGF-1 was a specific target for miR-129. Up-regulation and down-regulation of IGF-1/GSK3β signaling pathway separately alleviated and deteriorated neuronal pyroptosis in the cells. In the rats, high-fat diet caused cognitive impairment following with neuronal pyroptosis and down-regulation of IGF-1/GSK3β signaling pathway in midbrain and hippocampus tissues. Also, miR-129 antagomir improved these abnormalities in the rats. Inhibition of miR-129 improved neuronal pyroptosis and cognitive impairment through IGF-1/GSK3β signaling pathway.

Recurrent Glioblastoma: From Molecular Landscape to New Treatment Perspectives

Glioblastoma is the most frequent and aggressive form among malignant central nervous system primary tumors in adults. Standard treatment for newly diagnosed glioblastoma consists in maximal safe resection, if feasible, followed by radiochemotherapy and adjuvant chemotherapy with temozolomide; despite this multimodal treatment, virtually all glioblastomas relapse. Once tumors progress after first-line therapy, treatment options are limited and management of recurrent glioblastoma remains challenging. Loco-regional therapy with re-surgery or re-irradiation may be evaluated in selected cases, while traditional systemic therapy with nitrosoureas and temozolomide rechallenge showed limited efficacy. In recent years, new clinical trials using, for example, regorafenib or a combination of tyrosine kinase inhibitors and immunotherapy were performed with promising results. In particular, molecular targeted therapy could show efficacy in selected patients with specific gene mutations. Nonetheless, some molecular characteristics and genetic alterations could change during tumor progression, thus affecting the efficacy of precision medicine. We therefore reviewed the molecular and genomic landscape of recurrent glioblastoma, the strategy for clinical management and the major phase I-III clinical trials analyzing recent drugs and combination regimens in these patients.

Oncogenic State and Cell Identity Combinatorially Dictate the Susceptibility of Cells within Glioma Development Hierarchy to IGF1R Targeting

Glioblastoma is the most malignant cancer in the brain and currently incurable. It is urgent to identify effective targets for this lethal disease. Inhibition of such targets should suppress the growth of cancer cells and, ideally also precancerous cells for early prevention, but minimally affect their normal counterparts. Using genetic mouse models with neural stem cells (NSCs) or oligodendrocyte precursor cells (OPCs) as the cells-of-origin/mutation, it is shown that the susceptibility of cells within the development hierarchy of glioma to the knockout of insulin-like growth factor I receptor (IGF1R) is determined not only by their oncogenic states, but also by their cell identities/states. Knockout of IGF1R selectively disrupts the growth of mutant and transformed, but not normal OPCs, or NSCs. The desirable outcome of IGF1R knockout on cell growth requires the mutant cells to commit to the OPC identity regardless of its development hierarchical status. At the molecular level, oncogenic mutations reprogram the cellular network of OPCs and force them to depend more on IGF1R for their growth. A new-generation brain-penetrable, orally available IGF1R inhibitor harnessing tumor OPCs in the brain is also developed. The findings reveal the cellular window of IGF1R targeting and establish IGF1R as an effective target for the prevention and treatment of glioblastoma.

Glioma Cells With Genetically Engineered IGF-I Receptor Downregulation Can Persist in the Brain in a Dormant State

Glioblastoma multiforme is an aggressive malignancy, resistant to standard treatment modalities and associated with poor prognosis. We analyzed the role of the IGF system in intracerebral glioma growth using human and rat glioma cells. The glioma cells C6 and U87MG were transduced with a genetically engineered retrovirus expressing type 1 insulin-like growth factor (IGF-IR) antisense RNA, either before or after intra-cerebral implantation of the cells into Sprague Dawley rats or nude mice, respectively and tumor growth and animal survival were monitored. Rat glioma cells transduced prior to orthotopic, intra-cerebral implantation had a significantly increased apoptotic rate in vivo and a significantly reduced tumor volume as seen 24 days post implantation (p < 0.0015). This resulted in increased survival, as greater than 70% of the rats were still alive 182 days after tumor implantation (p < 0.01), as compared to 80% mortality by day 24 in the control group. Histomorphology and histochemical studies performed on brain tissue that was obtained from rats that survived for 182 days revealed numerous single cells that were widely disseminated throughout the brain. These cells expressed the β-galactosidase marker protein, but were Ki67negative, suggesting that they acquired a dormant phenotype. Direct targeting of the C6 cells with retroviral particles in vivo was effective and reduced tumor volumes by 22% relative to controls. A significant effect on tumor growth was also seen with human glioma U87MG cells that were virally transduced and implanted intra-cerebrally in nude mice. We observed in these mice a significant reduction in tumor volumes and 70% of the animals were still alive 6 months after tumor implantation, as compared to 100% mortality in the control group by day 63. Our results show that IGF-IR targeting can inhibit the intracerebral growth of glioma cells. They also suggest that IGF-IR expression levels may determine a delicate balance between glioma cell growth, death and the acquisition of a dormant state in the brain.

Neurofibromatosis 1-associated optic pathway gliomas

BACKGROUND

Optic Pathway Gliomas (OPG) are the most common brain tumor in Neurofibromatosis 1 patients (NF1). They are found along the optic pathway and may involve the optic nerves, chiasm, retro-chiasmatic structures, and the optic radiations. NF1 associate OPG (NF1-OPG) have variable presentation, disease course and response to treatment. The optimal management is patient-specific and should be tailored by a multidisciplinary team. Age, sex, histology, and molecular markers may be important factors in the individualized decision-making process. Chemotherapy is the first-line treatment in cases of progressive tumors, and visual preservation is the main goal of treatment.

PURPOSE

In this paper we will review the disease, practical management, and recent advances of NF1-OPG.

IGF-1R Inhibitor Ameliorates Neuroinflammation in an Alzheimer's Disease Transgenic Mouse Model

Aging is a major risk factor for Alzheimer's disease (AD). Insulin-like growth factor-1 receptor (IGF-1R) regulates general aging and lifespan. However, the contribution of IGF-1 to age-related AD pathology and progression is highly controversial. Based on our previous work, AβPP/PS1 double transgenic mice, which express human mutant amyloid precursor protein (APP) and presenilin-1 (PS-1), demonstrated a decrease in brain IGF-1 levels when they were crossed with IGF-1 deficient Ames dwarf mice (df/df). Subsequently, a reduction in gliosis, amyloid-β (Aβ) plaque deposition, and Aβ_1-40/42 concentrations were observed in this mouse model. This supported the hypothesis that IGF-1 may contribute to the progression of the disease. To assess the role of IGF-1 in AD, 9-10-month-old male littermate control wild type and AβPP/PS1 mice were randomly divided into two treatment groups including control vehicle (DMSO) and picropodophyllin (PPP), a selective, competitive, and reversible IGF-1R inhibitor. The brain penetrant inhibitor was given ip. at 1 mg/kg/day. Mice were sacrificed after 7 days of daily injection and the brains, spleens, and livers were collected to quantify histologic and biochemical changes. The PPP-treated AβPP/PS1 mice demonstrated attenuated insoluble Aβ_1-40/42. Additionally, an attenuation in microgliosis and protein p-tyrosine levels was observed due to drug treatment in the hippocampus. Our data suggest IGF-1R signaling is associated with disease progression in this mouse model. More importantly, modulation of the brain IGF-1R signaling pathway, even at mid-life, was enough to attenuate aspects of the disease phenotype. This suggests that small molecule therapy targeting the IGF-1R pathway may be viable for late-stage disease treatment.

Pericyte-secreted IGF2 promotes breast cancer brain metastasis formation

Brain metastases are life-threatening complications of triple-negative breast cancer, melanoma, and a few other tumor types. Poor outcome of cerebral secondary tumors largely depends on the microenvironment formed by cells of the neurovascular unit, among which pericytes are the least characterized. By using in vivo and in vitro techniques and human samples, here we show that pericytes play crucial role in the development of metastatic brain tumors by directly influencing key steps of the development of the disease. Brain pericytes had a prompt chemoattractant effect on breast cancer cells and established direct contacts with them. By secreting high amounts of extracellular matrix proteins, pericytes enhanced adhesion of both melanoma and triple-negative cancer cells, which might be particularly important in the exclusive perivascular growth of these tumor cells. In addition, pericytes secreted insulin-like growth factor 2 (IGF2), which had a very significant pro-proliferative effect on mammary carcinoma, but not on melanoma cells. By inhibiting IGF2 signaling using silencing or picropodophyllin (PPP), we could block the proliferation-increasing effect of pericytes on breast cancer cells. Administration of PPP (a blood-brain barrier-permeable substance) significantly decreased the size of brain tumors in mice inoculated with triple-negative breast cancer cells. Taken together, our results indicate that brain pericytes have significant pro-metastatic features, especially in breast cancer. Our study underlines the importance of targeting pericytes and the IGF axis as potential strategies in brain metastatic diseases.

Receptor tyrosine kinase targeting in glioblastoma: performance, limitations and future approaches

From all central nervous system tumors, gliomas are the most common. Nowadays, researchers are looking for more efficient treatments for these tumors, as well as ways for early diagnosis. Receptor tyrosine kinases (RTKs) are major targets for oncology and the development of small-molecule RTK inhibitors has been proven successful in cancer treatment. Mutations or aberrant activation of the RTKs and their intracellular signaling pathways are linked to several malignant diseases, including glioblastoma. The progress in the understanding of malignant glioma evolution has led to RTK targeted therapies with high capacity to improve the therapeutic response while reducing toxicity. In this review, we present the most important RTKs (i.e. EGFR, IGFR, PDGFR and VEGFR) currently used for developing cancer therapeutics together with the potential of RTK-related drugs in glioblastoma treatment. Also, we focus on some therapeutic agents that are currently at different stages of research or even in clinical phases and proved to be suitable as re-purposing candidates for glioblastoma treatment.

IGF1R regulates retrograde axonal transport of signalling endosomes in motor neurons

Signalling endosomes are essential for trafficking of activated ligand-receptor complexes and their distal signalling, ultimately leading to neuronal survival. Although deficits in signalling endosome transport have been linked to neurodegeneration, our understanding of the mechanisms controlling this process remains incomplete. Here, we describe a new modulator of signalling endosome trafficking, the insulin-like growth factor 1 receptor (IGF1R). We show that IGF1R inhibition increases the velocity of signalling endosomes in motor neuron axons, both in vitro and in vivo. This effect is specific, since IGF1R inhibition does not alter the axonal transport of mitochondria or lysosomes. Our results suggest that this change in trafficking is linked to the dynein adaptor bicaudal D1 (BICD1), as IGF1R inhibition results in an increase in the de novo synthesis of BICD1 in the axon of motor neurons. Finally, we found that IGF1R inhibition can improve the deficits in signalling endosome transport observed in a mouse model of amyotrophic lateral sclerosis (ALS). Taken together, these findings suggest that IGF1R inhibition may be a new therapeutic target for ALS.

Proteasome activation by insulin-like growth factor-1/nuclear factor erythroid 2-related factor 2 signaling promotes exercise-induced neurogenesis

Physical exercise-induced enhancement of learning and memory and alleviation of age-related cognitive decline in humans have been widely acknowledged. However, the mechanistic relationship between exercise and cognitive improvement remains largely unknown. In this study, we found that exercise-elicited cognitive benefits were accompanied by adaptive hippocampal proteasome activation. Voluntary wheel running increased hippocampal proteasome activity in adult and middle-aged mice, contributing to an acceleration of neurogenesis that could be reversed by intrahippocampal injection of the proteasome inhibitor MG132. We further found that increased levels of insulin-like growth factor-1 (IGF-1) in both serum and hippocampus may be essential for exercise-induced proteasome activation. Our in vitro study demonstrated that IGF-1 stimulated proteasome activity in cultured adult neural progenitor cells (NPCs) by promoting nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), followed by elevated expressions of proteasome subunits such as PSMB5. In contrast, pretreating adult mice with the selective IGF-1R inhibitor picropodophyllin diminished exercise-induced neurogenesis, concurrent with reduced Nrf2 nuclear translocation and proteasome activity. Likewise, lowering Nrf2 expression by RNA interference with bilateral intrahippocampal injections of recombinant adeno-associated viral particles significantly suppressed exercise-induced proteasome activation and attenuated cognitive function. Collectively, our work demonstrates that proteasome activation in hippocampus through IGF-1/Nrf2 signaling is a key adaptive mechanism underlying exercise-related neurogenesis, which may serve as a potential targetable pathway in neurodegeneration.

Anti-Tumor Effects of Osthole on Different Malignant Tissues: A Review of Molecular Mechanisms

Cancer management and/or treatment require a comprehensive understanding of the molecular and signaling pathways involved. Recently, much attention has been directed to these molecular and signaling pathways, and it has been suggested that a number of biomolecules/players involved in such pathways, such as PI3K/Akt, NF-kB, STAT, and Nrf2 contribute to the progression, invasion, proliferation, and metastasis of malignant cells. Synthetic anti-tumor agents and chemotherapeutic drugs have been a mainstay in cancer therapy and are widely used to suppress the progression and, hopefully, halt the proliferation of malignant cells. However, these agents have some undesirable side-effects and, therefore, naturally-occurring compounds with high potency and fewer side-effects are now of great interest. Osthole is a plant-derived chemical compound that can inhibit the proliferation of malignant cells and provide potent anti-cancer effects in various tissues. Therefore, in this review, we presented the main findings concerning the potential anti-tumor effects of osthole and its derivatives and described possible molecular mechanisms by which osthole may suppress malignant cell proliferation in different tissues.

A review of predictive, prognostic and diagnostic biomarkers for brain tumours: towards personalised and targeted cancer therapy

Background:

Brain tumours are relatively rare disease but present a large medical challenge as there is currently no method for early detection of the tumour and are typically not diagnosed until patients have progressed to symptomatic stage which significantly decreases chances of survival and also minimises treatment efficacy. However, if brain cancers can be diagnosed at early stages and also if clinicians have the potential to prospectively identify patients likely to respond to specific treatments, then there is a very high potential to increase patients’ treatment efficacy and survival. In recent years, there have been several investigations to identify biomarkers for brain cancer risk assessment, early detection and diagnosis, the likelihood of identifying which group of patients will benefit from a particular treatment and monitoring patient response to treatment.

Materials and methods:

This paper reports on a review of 21 current clinical and emerging biomarkers used in risk assessment, screening for early detection and diagnosis, and monitoring the response of treatment of brain cancers.

Conclusion:

Understanding biomarkers, molecular mechanisms and signalling pathways can potentially lead to personalised and targeted treatment via therapeutic targeting of specific genetic aberrant pathways which play key roles in malignant brain tumour formation. The future holds promising for the use of biomarker analysis as a major factor for personalised and targeted brain cancer treatment, since biomarkers have the potential to measure early disease detection and diagnosis, the risk of disease development and progression, improved patient stratification for various treatment paradigms, provide accurate information of patient response to a specific treatment and inform clinicians about the likely outcome of a brain cancer diagnosis independent of the treatment received.

PDGFR and IGF-1R Inhibitors Induce a G2/M Arrest and Subsequent Cell Death in Human Glioblastoma Cell Lines

Glioblastomas are highly resistant to radiation and chemotherapy. Currently, there are no effective therapies for this type of tumor. Signaling mechanisms initiated by PDGFR and IGF-1R are important in glioblastoma, and inhibition of the signal transduction pathways initiated by these receptors could be a useful alternative strategy for glioblastoma treatment. We have studied the effects of the PDGFR inhibitor JNJ-10198409 (JNJ) and the IGF-1R inhibitor picropodophyllin (PPP) in glioblastoma cell lines as well as in primary cultures derived from patients affected by this type of tumor. JNJ and PPP treatment blocked PDGFR and IGF-1R signaling respectively and reduced Akt and Erk 1/2 phosphorylation. Both inhibitors diminished cell proliferation, inducing a G2/M block of the cell cycle. Cell death induced by JNJ was caspase-dependent, Annexin-V positive and caused PARP cleavage, especially in T98 cells, suggesting an apoptotic mechanism. However, cell death induced by PPP was not completely inhibited by caspase inhibitors in all cell lines apart from LN-229 cells, indicating a caspase-independent mechanism. Several inhibitors targeted against different cell death pathways could not block this caspase-independent component, which may be a non-programmed necrotic mechanism. Apoptotic arrays performed in T98 and LN-229 cells upon JNJ and PPP treatment revealed that procaspase 3 levels were augmented by both drugs in T98 cells and only by JNJ in LN229-cells. Furthermore, XIAP and survivin levels were much higher in LN-229 cells than in T98 cells, revealing that LN-229 cells are more susceptible to undergo caspase-independent cell death mechanisms. JNJ and PPP combination was more effective than each treatment alone.

Migration/Invasion of Malignant Gliomas and Implications for Therapeutic Treatment

Malignant tumors of the central nervous system (CNS) are among cancers with the poorest prognosis, indicated by their association with tumors of high-level morbidity and mortality. Gliomas, the most common primary CNS tumors that arise from neuroglial stem or progenitor cells, have estimated annual incidence of 6.6 per 100,000 individuals in the USA, and 3.5 per 100,000 individuals in Taiwan. Tumor invasion and metastasis are the major contributors to the deaths in cancer patients. Therapeutic goals including cancer stem cells (CSC), phenotypic shifts, EZH2/AXL/TGF-β axis activation, miRNAs and exosomes are relevant to GBM metastasis to develop novel targeted therapeutics for GBM and other brain cancers. Herein, we highlight tumor metastasis in our understanding of gliomas, and illustrate novel exosome therapeutic approaches in glioma, thereby paving the way towards innovative therapies in neuro-oncology.

Type I insulin-like growth factor receptor signaling in hematological malignancies

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

Targeting IGF1R pathway in cancer with microRNAs: How close are we?

Cancer of the head and neck are the most common cancers in India and account for 30% of all cancers. At molecular level, it could be attributed to the overexpression of growth factors like IGF1-R, EGFR, VEGF-R and deregulation of cell cycle regulators and tumor suppressors. IGF1-R is an emerging target in head and neck cancer treatment, because of its reported role in tumor development, progression and metastasis. IGF1R targeted agents are in advanced stages of clinical development. Nevertheless, these agents suffer from several disadvantages including acquired resistance and toxic side effects. Hence there is a need for developing newer agents targeting not only the receptor but also its downstream signaling. miRNAs are considered as master regulators of gene expression of multiple genes and has been widely reported to be a promising therapeutic strategy. This review discusses the present status of research in both these arenas and emphasizes the role of miRNA as a promising agent for biologic therapy.

Targeting cellular pathways in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a debilitating disease that is associated with poor prognosis, short median patient survival and a very limited response to therapies. GBM has a very complex pathogenesis that involves mutations and alterations of several key cellular pathways that are involved in cell proliferation, survival, migration and angiogenesis. Therefore, efforts that are directed toward better understanding of GBM pathogenesis are essential to the development of efficient therapies that provide hope and extent patient survival. In this review, we outline the alterations commonly associated with GBM pathogenesis and summarize therapeutic strategies that are aimed at targeting aberrant cellular pathways in GBM.

Phase I clinical trial of AXL1717 for treatment of relapsed malignant astrocytomas: analysis of dose and response

Purpose

Early phase I study of safety of AXL1717 in patients with recurrent or progressive malignant astrocytomas and evaluation of preliminary anti-tumor efficacy.

Patients and methods

Nine patients fulfilling the set criteria were enrolled. Eight had recurrent glioblastoma and one gliosarcoma. Patients were treated with an oral suspension of AXL1717 (215-400 mg bid) cycle-by-cycle in 35-day cycles (28 days bid and 7 days off). Patients with progressive disease and/or toxicity-related dose delay of more than 14 days were withdrawn.

Results

Four patients had tumor responses (44%) to AXL1717 treatment. Two of these had stable disease for 12 months (10 cycles at 215-300 mg bid). Due to MRI-detected progression they were then taken off the study. They died 8 and 12 months later, respectively. One patient was treated 8 months (6 cycles with 215 mg bid). He was withdrawn because of disease progression but died after another 25 months. The fourth patient having stable disease died of sepsis due to pancytopenia in the end of cycle 2 on 400 mg bid. A fifth patient underwent surgery after two cycles with 300 mg bid. Pathological analysis demonstrated abundant necrosis and small areas of viable tumor. After one more cycle with 300 mg bid he was withdrawn due to clinical and radiographic worsening and died 11 months later. The other 4 patients did not have any detectable responses and died within 3-13 months after trial entry. Neutropenia was the main adverse effect, which was easily detected and reversible in all but one patient.

Conclusion

This clinical phase I study indicates that AXL1717 as a single agent is capable of producing prolonged stable disease and survival of patients with relapsed malignant astrocytomas. The drug was well tolerated. A new formulation of the drug will be used in further investigations in order to better define the optimal dose.

Picropodophyllin (PPP) is a potent rhabdomyosarcoma growth inhibitor both in vitro and in vivo

Background

Insulin-like growth factors and insulin are important factors promoting cancer growth and metastasis. The molecules act through IGF1 (IGF1R) and insulin (InsR) receptors. Rhambodmyosarcomas (RMS) overproduce IGF2 – a potent ligand for IGF1R and, at the same time, highly express IGF1 receptor. The purpose of the study was to evaluate possible application of picropodophyllin (PPP) – a potent IGF1R inhibitor.

Methods

In our study we used a number of in vitro assays showing influence of IGF1R blockage on RMS cell lines (both ARMS and ERMS) proliferation, migration, adhesion, cell cycling and signal transduction pathways. Additionally, we tested possible concomitant application of PPP with commonly used chemotherapeutics (vincristine, actinomycin-D and cisplatin). Moreover, we performed an in vivo study where PPP was injected intraperitoneally into RMS tumor bearing SCID mice.

Results

We observed that PPP strongly inhibits RMS proliferation, chemotaxis and adhesion. What is more, application of the IGF1R inhibitor attenuates MAPK phosphorylation and cause cell cycle arrest in G2/M phase. PPP increases sensitivity of RMS cell lines to chemotherapy, specifically to vincristine and cisplatin. In our in vivo studies we noted that mice treated with PPP grew smaller tumors and displayed significantly decreased seeding into bone marrow.

Conclusions

The cyclolignan PPP effectively inhibits RMS tumor proliferation and metastasis in vitro and in an animal model.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3495-y) contains supplementary material, which is available to authorized users.

Luteolin reduces migration of human glioblastoma cell lines via inhibition of the p-IGF-1R/PI3K/AKT/mTOR signaling pathway

Luteolin (3′,4′,5,7-tetrahydroxyflavone) is a common dietary flavonoid, which has been demonstrated to exert anticancer effects in multiple cancer models. However, the detailed mechanisms underlying the inhibitory effect of luteolin on glioblastoma cell metastasis remain poorly understood. The present study assessed the effects of luteolin in the U251MG and U87MG human glioblastoma cell lines. Luteolin treatment significantly inhibited glioblastoma cell migration, and this effect was associated with downregulated matrix metalloproteinase (MMP)-2, MMP-9 and upregulated tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2. In addition, luteolin also inhibited the epithelial-mesenchymal transition-associated phenotype. Furthermore, the phosphorylated insulin-like growth factor-1 receptor/phosphoinositide 3 kinase/protein kinase B/mammalian target of rapamycin (p-IGF-1R/PI3K/AKT/mTOR) signaling pathway was demonstrated to participate in these processes. The results of the present study demonstrated that the flavonoid luteolin reduced the migration of glioblastoma cells by altering p-IGF-1R/PI3K/AKT/mTOR activation, and may have potential applications for chemoprevention in a clinical setting.

Connexin 30 downregulates Insulin-like growth factor receptor-1, abolishes Erk and potentiates effects of an IGF-R inhibitor in a glioma cell line

Connexins (Cx) play a crucial role in cell communication though regulation of cell growth and proliferation. In recent decades, both suppressive and enhancing roles of gap junction proteins in malignancy have been proposed, though mechanisms remain unclear. We intend to evaluate the impact of Cx30 on dysregulated growth of glioma owing to an aberrant expression of Insulin-like growth factor-1 receptor (IGF-1R). The study also examined whether Cx30 expression influenced sensitivity of glioma cells to Picropodophyllin (PPP), the potent inhibitor of IGF-1R. C6 cells transfected with full length Cx30 resulted in complete abolition of colony-forming efficiency. Interestingly, PPP-supplemented cells behaved differently with and without exogenous Cx as confirmed by wound closure assay. The expressions of phosphorylated and unphosphorylated IGF-1R along with its key signaling enzymes, pAkt/pErk, were also varied significantly in transfected and non-transfected C6 cells. pIGF-1R and IGF-1R were significantly reduced on Cx30 transfection when compared with that of non-transfected cells. pErk expression was abolished in transfected C6 with no significant difference in the expression of pAkt. The potency of PPP against C6 was more pronounced in the presence of Cx30. We demonstrate that Cx30 has the potential to alter the IGF-1R mediated pathway thereby influencing the growth, proliferation and migration of glioma cells which could further enhance the effect of therapeutic intervention. Though it could not be corroborated that the observations made are due to Cx30-mediated channel-dependent and/or independent impact, we stress the impact of significance of Cx30 on IGF-1R in glioma and also in therapeutic aspects.

Erythropoietin and IGF-1 signaling synchronize cell proliferation and maturation during erythropoiesis

Kadri et al. show that erythropoietin activates AKT, which phosphorylates GATA-1 at Ser310, thereby increasing GATA-1 affinity for FOG-1. In turn, FOG-1 displaces pRb/E2F-2 from GATA-1, ultimately releasing free, proproliferative E2F-2. Mice bearing a GATA-1^S310A mutation suffer from fatal anemia when a compensatory pathway for E2F-2 production involving IGF-1 signaling is simultaneously abolished.

Tight coordination of cell proliferation and differentiation is central to red blood cell formation. Erythropoietin controls the proliferation and survival of red blood cell precursors, while variations in GATA-1/FOG-1 complex composition and concentrations drive their maturation. However, clear evidence of cross-talk between molecular pathways is lacking. Here, we show that erythropoietin activates AKT, which phosphorylates GATA-1 at Ser310, thereby increasing GATA-1 affinity for FOG-1. In turn, FOG-1 displaces pRb/E2F-2 from GATA-1, ultimately releasing free, proproliferative E2F-2. Mice bearing a Gata-1^S310A mutation suffer from fatal anemia when a compensatory pathway for E2F-2 production involving insulin-like growth factor-1 (IGF-1) signaling is simultaneously abolished. In the context of the GATA-1^V205G mutation resulting in lethal anemia, we show that the Ser310 cannot be phosphorylated and that constitutive phosphorylation at this position restores partial erythroid differentiation. This study sheds light on the GATA-1 pathways that synchronize cell proliferation and differentiation for tissue homeostasis.

The Ames dwarf mutation attenuates Alzheimer's disease phenotype of APP/PS1 mice

APP/PS1 double transgenic mice expressing human mutant amyloid precursor protein (APP) and presenilin-1 (PS1) demonstrate robust brain amyloid beta (Aβ) peptide containing plaque deposition, increased markers of oxidative stress, behavioral dysfunction, and proinflammatory gliosis. On the other hand, lack of growth hormone, prolactin, and thyroid-stimulating hormone due to a recessive mutation in the Prop 1 gene (Prop1df) in Ames dwarf mice results in a phenotype characterized by potentiated antioxidant mechanisms, improved learning and memory, and significantly increased longevity in homozygous mice. Based on this, we hypothesized that a similar hormone deficiency might attenuate disease changes in the brains of APP/PS1 mice. To test this idea, APP/PS1 mice were crossed to the Ames dwarf mouse line. APP/PS1, wild-type, df/+, df/df, df/+/APP/PS1, and df/df/APP/PS1 mice were compared at 6 months of age through behavioral testing and assessing amyloid burden, reactive gliosis, and brain cytokine levels. df/df mice demonstrated lower brain growth hormone and insulin-like growth factor 1 concentrations. This correlated with decreased astrogliosis and microgliosis in the df/df/APP/PS1 mice and, surprisingly, reduced Aβ plaque deposition and Aβ 1-40 and Aβ 1-42 concentrations. The df/df/APP/PS1 mice also demonstrated significantly elevated brain levels of multiple cytokines in spite of the attenuated gliosis. These data indicate that the df/df/APP/PS1 line is a unique resource in which to study aging and resistance to disease and suggest that the affected pituitary hormones may have a role in regulating disease progression.

IGF-IR: a new prognostic biomarker for human glioblastoma

Background:

Glioblastomas (GBMs) are the most common malignant primary brain tumours in adults and are refractory to conventional therapy, including surgical resection, radiotherapy and chemotherapy. The insulin-like growth factor (IGF) system is a complex network that includes ligands (IGFI and IGFII), receptors (IGF-IR and IGF-IIR) and high-affinity binding proteins (IGFBP-1 to IGFBP-6). Many studies have reported a role for the IGF system in the regulation of tumour cell biology. However, the role of this system remains unclear in GBMs.

Methods:

We investigate the prognostic value of both the IGF ligands' and receptors' expression in a cohort of human GBMs. Tissue microarray and image analysis were conducted to quantitatively analyse the immunohistochemical expression of these proteins in 218 human GBMs.

Results:

Both IGF-IR and IGF-IIR were overexpressed in GBMs compared with normal brain (P<10⁻⁴ and P=0.002, respectively). Moreover, with regard to standard clinical factors, IGF-IR positivity was identified as an independent prognostic factor associated with shorter survival (P=0.016) and was associated with a less favourable response to temozolomide.

Conclusions:

This study suggests that IGF-IR could be an interesting target for GBM therapy.

GSK1838705A, an IGF-1R inhibitor, inhibits glioma cell proliferation and suppresses tumor growth in vivo

Glioma is a type of primary malignant tumor of the central nervous system in humans. At present, standard treatment involves surgical resection, followed by radiation therapy and chemotherapy. However, the prognosis is poor and the long-term survival rate remains low. An improved understanding of the molecular basis for glioma tumorigenesis is in urgently required. The pro-survival effect of the insulin-like growth factor (IGF) signaling pathway has been implicated in progression of the glioma disease state. GSK1838705A is a novel, small molecule kinase inhibitor of IGF-IR, which inhibits IGF signal transduction and downstream target activation. Its anti-proliferative activity has been demonstrated in various tumor cell lines. The present study investigated the potential use of GSK1838705A for the treatment of glioma. Human U87MG glioma cells were used to examine the inhibitory activity of GSK1838705A in cell proliferation, migration and apoptosis. The antitumor activity of GSK1838705A was assessed in a xenograft mouse model. GSK1838705A inhibited the growth and induced the apoptosis of the U87MG glioma cells in a dose-dependent manner. The GSK1838705A-treated cells exhibited reduced migratory activity in response to chemoattractants. The present study further demonstrated the antitumor activity of GSK1838705A in vivo. The administration of GSK1838705A significantly inhibited the growth of glioma tumors by inducing the apoptosis of tumor cells. These results suggested that targeting IGF signaling with GSK1838705A may be a promising therapeutic strategy for the treatment of patients with glioma.

Insulin-mediated signaling promotes proliferation and survival of glioblastoma through Akt activation

BACKGROUND

Metabolic complications such as obesity, hyperglycemia, and type 2 diabetes are associated with poor outcomes in patients with glioblastoma. To control peritumoral edema, use of chronic high-dose steroids in glioblastoma patients is common, which can result in de novo diabetic symptoms. These metabolic complications may affect tumors via profound mechanisms, including activation of insulin receptor (InsR) and the related insulin-like growth factor 1 receptor (IGF1R) in malignant cells.

METHODS

In the present study, we assessed expression of InsR in glioblastoma surgical specimens and glioblastoma response to insulin at physiologically relevant concentrations. We further determined whether genetic or pharmacological targeting of InsR affected oncogenic functions of glioblastoma in vitro and in vivo.

RESULTS

We showed that InsR was commonly expressed in glioblastoma surgical specimens and xenograft tumor lines, with mitogenic isoform-A predominating. Insulin at physiologically relevant concentrations promoted glioblastoma cell growth and survival, potentially via Akt activation. Depletion of InsR impaired cellular functions and repressed orthotopic tumor growth. The absence of InsR compromised downstream Akt activity, but yet stimulated IGF1R expression. Targeting both InsR and IGF1R with dual kinase inhibitors resulted in effective blockade of downstream signaling, loss of cell viability, and repression of xenograft tumor growth.

CONCLUSIONS

Taken together, our work suggests that glioblastoma is sensitive to the mitogenic functions of insulin, thus significant insulin exposure imposes risks to glioblastoma patients. Additionally, dual inhibition of InsR and IGF1R exhibits promise for treating glioblastoma.

A high-throughput in vitro drug screen in a genetically engineered mouse model of diffuse intrinsic pontine glioma identifies BMS-754807 as a promising therapeutic agent

Diffuse intrinsic pontine gliomas (DIPGs) represent a particularly lethal type of pediatric brain cancer with no effective therapeutic options. Our laboratory has previously reported the development of genetically engineered DIPG mouse models using the RCAS/tv-a system, including a model driven by PDGF-B, H3.3K27M, and p53 loss. These models can serve as a platform in which to test novel therapeutics prior to the initiation of human clinical trials. In this study, an in vitro high-throughput drug screen as part of the DIPG preclinical consortium using cell-lines derived from our DIPG models identified BMS-754807 as a drug of interest in DIPG. BMS-754807 is a potent and reversible small molecule multi-kinase inhibitor with many targets including IGF-1R, IR, MET, TRKA, TRKB, AURKA, AURKB. In vitro evaluation showed significant cytotoxic effects with an IC₅₀ of 0.13 μM, significant inhibition of proliferation at a concentration of 1.5 μM, as well as inhibition of AKT activation. Interestingly, IGF-1R signaling was absent in serum-free cultures from the PDGF-B; H3.3K27M; p53 deficient model suggesting that the antitumor activity of BMS-754807 in this model is independent of IGF-1R. In vivo, systemic administration of BMS-754807 to DIPG-bearing mice did not prolong survival. Pharmacokinetic analysis demonstrated that tumor tissue drug concentrations of BMS-754807 were well below the identified IC₅₀, suggesting that inadequate drug delivery may limit in vivo efficacy. In summary, an unbiased in vitro drug screen identified BMS-754807 as a potential therapeutic agent in DIPG, but BMS-754807 treatment in vivo by systemic delivery did not significantly prolong survival of DIPG-bearing mice.

The dichotomy of the Insulin-like growth factor 1 receptor: RTK and GPCR: friend or foe for cancer treatment?

The prime position of the insulin-like growth factor 1 receptor (IGF-1R), at the head of the principle mitogenic and anti-apoptotic signalling cascades, along with the resilience to transformation of IGF-1R deficient cells fuelled great excitement for its anti-cancer targeting. Yet its potential has not been fulfilled, as clinical trial results fell far short of expectations. Advancements in understanding of other receptors' function have now begun to shed light on this incongruity, with the now apparent parallels highlighting the immaturity of our understanding of IGF-1R biology, with the model used for drug development now recognised as having been too simplistic. Gathering together the many advancements of the field of IGF-1R research over the past decade, alongside those in the GPCR field, advocates for a major paradigm shift in our appreciation of the subtle workings of this receptor. This review will emphasise the updating of the IGF-1R's classification from an RTK, to an RTK/GPCR functional hybrid, which integrates both canonical kinase signalling with many functions characteristic of a GPCR. Recognition of the shortcomings of IGF-1R inhibitor drug development programs and the models used not only allows us to reignite the initial interest in the IGF-1R as an anti-cancer therapeutic target, but also points to the possibility of biased ligand therapeutics, which together may hold a very powerful key to unlocking the true potential of IGF-1R modulation.

Inhibition of intracerebral glioblastoma growth by targeting the insulin-like growth factor 1 receptor involves different context-dependent mechanisms

BACKGROUND

Signaling by insulin-like growth factor 1 receptor (IGF-1R) can contribute to the formation and progression of many diverse tumor types, including glioblastoma. We investigated the effect of the IGF-1R blocking antibody IMC-A12 on glioblastoma growth in different in vivo models.

METHODS

U87 cells were chosen to establish rapidly growing, angiogenesis-dependent tumors in the brains of nude mice, and the GS-12 cell line was used to generate highly invasive tumors. IMC-A12 was administered using convection-enhanced local delivery. Tumor parameters were quantified histologically, and the functional relevance of IGF-1R activation was analyzed in vitro.

RESULTS

IMC-A12 treatment inhibited the growth of U87 and GS-12 tumors by 75% and 50%, respectively. In GS-12 tumors, the invasive tumor extension and proliferation rate were significantly reduced by IMC-A12 treatment, while apoptosis was increased. In IMC-A12-treated U87 tumors, intratumoral vascularization was markedly decreased, and tumor cell proliferation was moderately reduced. Flow cytometry showed that <2% of U87 cells but >85% of GS-12 cells expressed IGF-1R. Activation of IGF-1R by IGF-1 and IGF-2 in GS-12 cells was blocked by IMC-A12. Both ligands stimulated GS-12 cell proliferation, and IGF-2 also stimulated migration. IMC-A12 inhibited these stimulatory effects and increased apoptosis. In U87 cells, stimulation with either ligand had no functional effect.

CONCLUSIONS

IGF-1R blockade can inhibit glioblastoma growth by different mechanisms, including direct effects on the tumor cells as well as indirect anti-angiogenic effects. Hence, blocking IGF-1R may be useful to target both the highly proliferative, angiogenesis-dependent glioblastoma core component as well as the infiltrative periphery.

Targeting the insulin-like growth factor-1 receptor by picropodophyllin for lung cancer chemoprevention

Insulin-like growth factor-1 receptor (IGF-1R) is a transmembrane heterotetramer that is activated by Insulin-like growth factor 1 and is crucial for tumor transformation and survival of malignant cells. Importantly, IGF-1R overexpression has been reported in many different cancers, implicating this receptor as a potential target for anticancer therapy. Picropodophyllin (PPP) is a potent inhibitor of IGF-1R and has antitumor efficacy in several cancer types. However, the chemopreventive effect of PPP in lung tumorigenesis has not been investigated. In this study, we investigated the chemopreventive activity of PPP in a mouse lung tumor model. Benzo(a)pyrene was used to induce lung tumors, and PPP was given by nasal inhalation to female A/J mice. Lung tumorigenesis was assessed by tumor multiplicity and tumor load. PPP significantly decreased tumor multiplicity and tumor load. Tumor multiplicity and load were decreased by 52% and 78% respectively by 4 mg/ml aerosolized PPP. Pharmacokinetics analysis showed good bioavailability of PPP in lung and plasma. Treatment with PPP increased staining for cleaved caspase-3 and decreased Ki-67 in lung tumors, suggesting that the lung tumor inhibitory effects of PPP were partially through inhibition of proliferation and induction of apoptosis. In human lung cancer cell lines, PPP inhibited cell proliferation, and also inhibited phosphorylation of IGF-1R downstream targets, AKT and MAPK, ultimately resulting in increased apoptosis. PPP also reduced cell invasion in lung cancer cell lines. In view of our data, PPP merits further investigation as a promising chemopreventive agent for human lung cancer.

Osthole inhibits insulin-like growth factor-1-induced epithelial to mesenchymal transition via the inhibition of PI3K/Akt signaling pathway in human brain cancer cells

Glioblastoma multiforme (GBM) is one of the most lethal types of tumors and highly metastatic and invasive. The epithelial-to-mesenchymal transition (EMT) is the crucial step for cancer cells to initiate the metastasis and could be induced by many growth factors. In this study, we found that GBM8401 cells were converted to fibroblastic phenotype and the space between the cells became expanded in response to insulin-like growth factor-1 (IGF-1) treatment. Epithelial markers were downregulated and mesenchymal markers were upregulated simultaneously after IGF-1 treatment. Our results illustrate that IGF-1 was able to induce EMT in GBM8401 cells. Osthole would reverse IGF-1-induced morphological changes, upregulated the expression of epithelial markers, and downregulated the expression of mesenchymal markers. Moreover, wound-healing assay also showed that osthole could inhibit IGF-1-induced migration of GBM8401 cells. By using dual-luciferase reporter assay and real-time PCR, we demonstrated that osthole inhibited IGF-1-induced EMT at the transcriptional level. Our study found that osthole decreased the phosphorylation of Akt and GSK3β and recovered the GSK3β bioactivity in inhibiting EMT transcription factor Snail and Twist expression. These results showed that osthole inhibited IGF-1-induced EMT by blocking PI3K/Akt pathway. We hope that osthole can be used in anticancer therapy and be a new therapeutic medicine for GBM in the future.

Role of receptor tyrosine kinases and their ligands in glioblastoma

Glioblastoma multiforme is the most frequent, aggressive and fatal type of brain tumor. Glioblastomas are characterized by their infiltrating nature, high proliferation rate and resistance to chemotherapy and radiation. Recently, oncologic therapy experienced a rapid evolution towards “targeted therapy,” which is the employment of drugs directed against particular targets that play essential roles in proliferation, survival and invasiveness of cancer cells. A number of molecules involved in signal transduction pathways are used as molecular targets for the treatment of various tumors. In fact, inhibitors of these molecules have already entered the clinic or are undergoing clinical trials. Cellular receptors are clear examples of such targets and in the case of glioblastoma multiforme, some of these receptors and their ligands have become relevant. In this review, the importance of glioblastoma multiforme in signaling pathways initiated by extracellular tyrosine kinase receptors such as EGFR, PDGFR and IGF-1R will be discussed. We will describe their ligands, family members, structure, activation mechanism, downstream molecules, as well as the interaction among these pathways. Lastly, we will provide an up-to-date review of the current targeted therapies in cancer, in particular glioblastoma that employ inhibitors of these pathways and their benefits.

Met, IGF1R, and other new targets in upper GI malignancies

OPINION STATEMENT

Upper gastrointestinal (GI) malignancies comprise some of the most aggressive human cancers. Expanding knowledge of molecular mechanisms is finally translating into clinical application, and this has occurred at a relatively rapid rate in the past several years. However, despite recent advances in targeted therapies in upper GI cancers our overall success with targeted therapeutics in this disease area remains dismal. This statement is particularly troubling given some sobering facts: upper GI malignancies are prevalent as well as aggressive with a high morbidity and mortality. Esophagus and gastric cancer combined have an annual global incidence of over 1.2 million new cases annually while median survival is less than 1 year for most patients with metastatic disease. Progress has been limited due to several factors including: disease heterogeneity and variance of phenotype across the globe, clinical trial design strategies that have not yet incorporated selective mechanisms to afford individualized matching of drug to tumor molecular profile and last, a lack of validated predictive markers. Nevertheless there is evidence that many targeted agents can be administered safely at doses that achieve the required effect at the protein level. Several drugs that have negative early trial results can be potentially vital therapeutic agents if patient selection is appropriate.

Inhibition of type I insulin-like growth factor receptor tyrosine kinase by picropodophyllin induces apoptosis and cell cycle arrest in T lymphoblastic leukemia/lymphoma

It has been recently shown that the type I insulin-like growth factor receptor (IGF-IR) contributes significantly to the survival of T lymphoblastic leukemia/lymphoma (T-LBL) cells, and it was therefore suggested that IGF-IR could represent a legitimate therapeutic target in this aggressive disease. Picropodophyllin (PPP) is a potent, selective inhibitor of IGF-IR that is currently used with notable success in clinical trials that include patients with aggressive types of epithelial tumors. In the present study, we tested the effects of PPP on Jurkat and Molt-3 cells; two prototype T-LBL cell lines. Our results demonstrate that PPP efficiently induced apoptotic cell death and cell cycle arrest of these two cells. These effects were attributable to alterations of downstream target proteins. By using proteomic analysis, seven different proteins were found to be affected by PPP treatment of Jurkat cells. These proteins are involved in various aspects of cellular metabolism, cytoskeleton organization and signal transduction pathways. The results suggest that PPP affects multiple signaling molecules and inhibits fundamental pathways that control cell growth and survival. Our study also provides novel evidence that PPP could be potentially utilized for the treatment of aggressive T-LBL.