EGFR-targeted therapy in malignant glioma: novel aspects and mechanisms of drug resistance

Oncogenic roles of long non-coding RNAs in essential glioblastoma signaling pathways

Glioblastoma multiforme (GBM) is an aggressive and diffuse type of glioma with the lowest survival rate in patients. The recent failure of multiple treatments suggests that targeting several targets at once may be a different strategy to overcome GBM carcinogenesis. Normal function of oncogenes and tumor suppressor genes need for the preservation of regular cellular processes, so any defects in these genes' activity, operate the corresponding signaling pathways, which initiate carcinogenic processes. Long non-coding RNAs (lncRNAs) that can be found in the cytoplasm or nucleus of the cells, control the transcription and translation of genes. LncRNAs perform a variety of functions, including epigenetic alteration, protein modification and stability, transcriptional regulation, and competition for miRNA that regulate mRNA translation through sponging miRNAs. Identification of various oncogenic lncRNAs and their multiple roles in brain cancers making them potential candidates for use as glioma diagnostic, prognostic, and therapeutic targets in the future. This study highlighted multiple oncogenic lncRNAs and classified them into different signaling pathways based on the regulated target genes in glioblastoma.

Origin recognition complex 6 overexpression promotes growth of glioma cells

The discovery of novel oncotargets for glioma is of immense significance. We here explored the expression patterns, biological functions, and underlying mechanisms associated with ORC6 (origin recognition complex 6) in glioma. Through the bioinformatics analyses, we found a significant increase in ORC6 expression within human glioma tissues, correlating with poorer overall survival, higher tumor grade, and wild-type isocitrate dehydrogenase status. Additionally, ORC6 overexpression is detected in glioma tissues obtained from locally-treated patients and across various primary/established glioma cells. Further bioinformatics scrutiny revealed that genes co-expressed with ORC6 are enriched in multiple signaling cascades linked to cancer. In primary and immortalized (A172) glioma cells, depleting ORC6 using specific shRNA or Cas9-sgRNA knockout (KO) significantly decreased cell viability and proliferation, disrupted cell cycle progression and mobility, and triggered apoptosis. Conversely, enhancing ORC6 expression via a lentiviral construct augmented malignant behaviors in human glioma cells. ORC6 emerged as a crucial regulator for the expression of key oncogenic genes, including Cyclin A2, Cyclin B2, and DNA topoisomerase II (TOP2A), within glioma cells. Silencing or KO of ORC6 reduced the mRNA and protein levels of these genes, while overexpression of ORC6 increased their expression in primary glioma cells. Bioinformatics analyses further identified RBPJ as a potential transcription factor of ORC6. RBPJ shRNA decreased ORC6 expression in primary glioma cells, while its overexpression increased it. Additionally, significantly enhanced binding between the RBPJ protein and the proposed ORC6 promoter region was detected in glioma tissues and cells. In vivo experiments demonstrated a significant reduction in the growth of patient-derived glioma xenografts in the mouse brain subsequent to ORC6 KO. ORC6 depletion, inhibited proliferation, decreased expression of Cyclin A2/B2/TOP2A, and increased apoptosis were detected within these ORC6 KO intracranial glioma xenografts. Altogether, RBPJ-driven ORC6 overexpression promotes glioma cell growth, underscoring its significance as a promising therapeutic target.

A natural compound melatonin enhances the effects of Nimotuzumab via inhibiting EGFR in glioblastoma

Sleep disorders are prevalent and debilitating symptoms in primary brain tumor patients, notably those receiving radiation therapy. Nevertheless, the relationship between sleep disorders, melatonin - a circadian rhythm regulatory hormone, and gliomas is underexplored. Melatonin exhibits various biological functions, one of them being anti-tumor activity. In the context of gliomas, often overexpressing EGFR, the humanized monoclonal antibody Nimotuzumab targets this marker. Our research discovered that variations in circadian rhythm significantly influence tumor growth in mice through impacting melatonin secretion. Harnessing proteogenomic, we identified that melatonin could inhibit the phosphorylation of EGFR and its downstream effectors, key elements in angiogenesis and tumor progression. Building on structural simulations, we propose that melatonin may amplify Nimotuzumab's anti-glioma efficacy by inhibiting EGFR TK dimerization. This proposition was validated in our in vitro and in vivo studies where melatonin synergistically augmented cytotoxicity and apoptosis in Nimotuzumab-treated glioma cells. Thus, melatonin shows promise as a beneficial addition to Nimotuzumab treatment in glioma patients.

Glioblastoma Therapy: Past, Present and Future

Glioblastoma (GB) stands out as the most prevalent and lethal form of brain cancer. Although great efforts have been made by clinicians and researchers, no significant improvement in survival has been achieved since the Stupp protocol became the standard of care (SOC) in 2005. Despite multimodality treatments, recurrence is almost universal with survival rates under 2 years after diagnosis. Here, we discuss the recent progress in our understanding of GB pathophysiology, in particular, the importance of glioma stem cells (GSCs), the tumor microenvironment conditions, and epigenetic mechanisms involved in GB growth, aggressiveness and recurrence. The discussion on therapeutic strategies first covers the SOC treatment and targeted therapies that have been shown to interfere with different signaling pathways (pRB/CDK4/RB1/P16ink4, TP53/MDM2/P14arf, PI3k/Akt-PTEN, RAS/RAF/MEK, PARP) involved in GB tumorigenesis, pathophysiology, and treatment resistance acquisition. Below, we analyze several immunotherapeutic approaches (i.e., checkpoint inhibitors, vaccines, CAR-modified NK or T cells, oncolytic virotherapy) that have been used in an attempt to enhance the immune response against GB, and thereby avoid recidivism or increase survival of GB patients. Finally, we present treatment attempts made using nanotherapies (nanometric structures having active anti-GB agents such as antibodies, chemotherapeutic/anti-angiogenic drugs or sensitizers, radionuclides, and molecules that target GB cellular receptors or open the blood-brain barrier) and non-ionizing energies (laser interstitial thermal therapy, high/low intensity focused ultrasounds, photodynamic/sonodynamic therapies and electroporation). The aim of this review is to discuss the advances and limitations of the current therapies and to present novel approaches that are under development or following clinical trials.

Characterization of prevalent tyrosine kinase inhibitors and their challenges in glioblastoma treatment

Glioblastoma multiforme (GBM) is a highly aggressive malignant primary tumor in the central nervous system. Despite extensive efforts in radiotherapy, chemotherapy, and neurosurgery, there remains an inadequate level of improvement in treatment outcomes. The development of large-scale genomic and proteomic analysis suggests that GBMs are characterized by transcriptional heterogeneity, which is responsible for therapy resistance. Hence, knowledge about the genetic and epigenetic heterogeneity of GBM is crucial for developing effective treatments for this aggressive form of brain cancer. Tyrosine kinases (TKs) can act as signal transducers, regulate important cellular processes like differentiation, proliferation, apoptosis and metabolism. Therefore, TK inhibitors (TKIs) have been developed to specifically target these kinases. TKIs are categorized into allosteric and non-allosteric inhibitors. Irreversible inhibitors form covalent bonds, which can lead to longer-lasting effects. However, this can also increase the risk of off-target effects and toxicity. The development of TKIs as therapeutics through computer-aided drug design (CADD) and bioinformatic techniques enhance the potential to improve patients' survival rates. Therefore, the continued exploration of TKIs as drug targets is expected to lead to even more effective and specific therapeutics in the future.

Intragenic EGFR::EGFR.E1E8 Fusion (EGFRvIII) in 4331 Solid Tumors

Epidermal growth factor receptor variant III (EGFRvIII, the deletion of exons 2-7) is a recurrent intragenic EGFR::EGFR.E1E8 fusion that occurs in high-grade gliomas. The presence of EGFRvIII in other solid tumors has not been well characterized. We retrospectively reviewed advanced malignant solid tumor cases tested by a custom hybrid capture 610-gene next-generation sequencing platform from 2021 to 2022. EGFRvIII was identified in 17 of 4331 (0.4%) cases, including 16 of 238 (7%) brain tumors and 1/301 (0.3%) breast tumors. EGFRvIII-positive brain tumors were all glioblastoma IDH-wildtype, most with concurrent TERT promoter mutation (14 of 16), EGFR amplification (13 of 16), and EGFR mutation (8 of 16). The only EGFRvIII-positive breast lesion was a sarcomatoid neoplasm in a young female patient. A separate breast case tested outside our institution with reported EGFRvIII was noted in a young female patient with a malignant phyllodes tumor with stromal overgrowth. Microscopically, both EGFRvIII-positive breast tumors showed high-grade sarcomatoid morphology with brisk mitotic activity. In summary, EGFRvIII is rare, occurring primarily in glioblastoma and rarely in breast sarcomatoid neoplasm, with no instances identified in other tumor types in our series. This select group of patients may benefit from chemotherapy and/or targeted anti-EGFR therapy.

Sitravatinib is a potential EGFR inhibitor and induce a new death phenotype in Glioblastoma

Glioblastoma (GBM) is a highly lethal neurological tumor that presents significant challenge for clinicians due to its heterogeneity and high mortality rate. Despite extensive research, there is currently no effective drug treatment available for GBM. Research evidence has consistently demonstrated that the epidermal growth factor receptor (EGFR) promotes tumor progression and is associated with poor prognosis in several types of cancer. In glioma, EGFR abnormal amplification is reported in approximately 40% of GBM patients, with overexpression observed in 60% of cases, and deletion or mutation in 24% to 67% of patients. In our study, Sitravatinib, a potential EGFR inhibitor, was identified through molecular docking screening based on protein structure. The targeting of EGFR and the tumor inhibitory effect of Sitravatinib on glioma were verified through cellular and in vivo experiments, respectively. Our study also revealed that Sitravatinib effectively inhibited GBM invasive and induced DNA damage and cellular senescence. Furthermore, we observed a novel cell death phenotype induced by Sitravatinib, which differed from previously reported programmed death patterns such as apoptosis, pyroptosis, ferroptosis, and necrosis.

Discovery of novel thyrointegrin αvβ3 antagonist fb-PMT (NP751) in the management of human glioblastoma multiforme

Background

Thyrointegrin αvβ3 receptors are unique molecular cancer therapeutic targets because of their overexpression on cancer and rapidly dividing blood vessel cells compared and quiescent on normal cells. A macromolecule, TriAzole Tetraiodothyroacetic acid (TAT) conjugated to polyethylene glycol with a lipophilic 4-fluorobenyl group (fb-PMT and NP751), interacts with high affinity (0.21 nM) and specificity with the thyrointegrin αvβ3 receptors on the cell surface without nuclear translocation in contrast to the non-polymer conjugated TAT.

Methods

The following in vitro assays were carried out to evaluate NP751 including binding affinity to different integrins, transthyretin (TTR)-binding affinity, glioblastoma multiforme (GBM) cell adhesion, proliferation assays, nuclear translocations, chorioallantoic membrane model of angiogenesis, and microarray for molecular mechanisms. Additionally, in vivo studies were carried out to evaluate the anticancer efficacy of NP751, its biodistribution, and brain GBM tumor versus plasma levels kinetics.

Results

NP751 demonstrated a broad spectrum of antiangiogenesis and anticancer efficacy in experimental models of angiogenesis and xenografts of human GBM cells. Tumor growth and cancer cells' viability were markedly decreased (by > 90%; P < .001) in fb-PMT-treated U87-luc or 3 different primary human GBM xenograft-bearing mice based on tumor in vivo imaging system (IVIS) imaging and histopathological examination, without relapse upon treatment discontinuation. Additionally, it effectively transports across the blood-brain barrier via its high-affinity binding to plasma TTR with high retention in brain tumors. NP751-induced effects on gene expression support the model of molecular interference at multiple key pathways essential for GBM tumor progression and vascularization.

Conclusions

fb-PMT is a potent thyrointegrin αvβ3 antagonist with potential impact on GBM tumor progression.

Antitumor activity of irinotecan with ellagic acid in C6 glioma cells

OBJECTIVE:

Irinotecan-based combination chemotherapies in malignant gliomas need to be examined. The aim of this study was to investigate the synergetic effect of ellagic acid, a natural polyphenolic antioxidant compound, with irinotecan, an inhibitor of topoisomerase I enzyme, on the growth, cadherin switch, and angiogenic processes of a glioma cell line.

METHODS:

A combination of 100 μM ellagic acid and 100 μM irinotecan was applied to rat C6 glioma cells for 24th, 48th, and 72nd h. The cell proliferation was evaluated by 5-bromo-2′-deoxyuridine immunocytochemistry. The expression levels of vascular endothelial growth factor, E-cadherin, and N-cadherin were measured using real-time polymerase chain reaction and their immunoreactivities using immunocytochemistry.

RESULTS:

The treatment of irinotecan with combining ellagic acid enhanced antitumor activity and the synergistic effect of these reduced the cell proliferation of C6 glioma by inhibiting the cadherin switch and promoting the antiangiogenic processes.

CONCLUSIONS:

Further research is required to prove a negative relationship between C6 glial cell proliferation and irinotecan with ellagic acid application. Our preliminary data suggest that even with the extremely short-term application, irinotecan with ellagic acid may affect glioma cells at the level of gene and protein expression.

Effects of Anticancer Agent P-bi-TAT on Gene Expression Link the Integrin Thyroid Hormone Receptor to Expression of Stemness and Energy Metabolism Genes in Cancer Cells

Chemically modified forms of tetraiodothyroacetic acid (tetrac), an L-thyroxine derivative, have been shown to exert their anticancer activity at plasma membrane integrin αvβ3 of tumor cells. Via a specific hormone receptor on the integrin, tetrac-based therapeutic agents modulate expression of genes relevant to cancer cell proliferation, survival and energy metabolism. P-bi-TAT, a novel bivalent tetrac-containing synthetic compound has anticancer activity in vitro and in vivo against glioblastoma multiforme (GBM) and other types of human cancers. In the current study, microarray analysis was carried out on a primary culture of human GBM cells exposed to P-bi-TAT (10⁻⁶ tetrac equivalent) for 24 h. P-bi-TAT significantly affected expression of a large panel of genes implicated in cancer cell stemness, growth, survival and angiogenesis. Recent interest elsewhere in ATP synthase as a target in GBM cells caused us to focus attention on expression of genes involved in energy metabolism. Significantly downregulated transcripts included multiple energy-metabolism-related genes: electron transport chain genes ATP5A1 (ATP synthase 1), ATP51, ATP5G2, COX6B1 (cytochrome c oxidase subunit 6B1), NDUFA8 (NADH dehydrogenase (ubiquinone) FA8), NDUFV2I and other NDUF genes. The NDUF and ATP genes are also relevant to control of oxidative phosphorylation and transcription. Qualitatively similar actions of P-bi-TAT on expression of subsets of energy-metabolism-linked genes were also detected in established human GBM and pancreatic cancer cell lines. In conclusion, acting at αvβ3 integrin, P-bi-TAT caused downregulation in human cancer cells of expression of a large number of genes involved in electron transport and oxidative phosphorylation. These observations suggest that cell surface thyroid hormone receptors on αvβ3 regulate expression of genes relevant to tumor cell stemness and energy metabolism.

Antitumor Efficacy of EGFR-Targeted Recombinant Immunotoxin in Human Head and Neck Squamous Cell Carcinoma

Over 90% of head and neck squamous cell carcinoma (HNSCC) overexpresses the epidermal growth factor receptor (EGFR). However, the EGFR-targeted monotherapy response rate only achieves 10-30% in HNSCC. Recombinant immunotoxin (RIT) often consists of an antibody targeting a tumor antigen and a toxin (e.g., diphtheria toxin [DT]) that kills cancer cells. We produced a humanized RIT, designated as hDT806, targeting overexpressed EGFR and investigated its effects in HNSCC. Distinct from the EGFR-targeted tyrosine kinase inhibitor erlotinib or antibody cetuximab, hDT806 effectively suppressed cell proliferation in the four HNSCC lines tested (JHU-011, -013, -022, and -029). In JHU-029 mouse xenograft models, hDT806 substantially reduced tumor growth. hDT806 decreased EGFR protein levels and disrupted the EGFR signaling downstream effectors, including MAPK/ERK1/2 and AKT, while increased proapoptotic proteins, such as p53, caspase-9, caspase-3, and the cleaved PAPR. The hDT806-induced apoptosis of HNSCC cells was corroborated by flow cytometric analysis. Furthermore, hDT806 resulted in a drastic inhibition in RNA polymerase II carboxy-terminal domain phosphorylation critical for transcription and a significant increase in the γH2A.X level, a DNA damage marker. Thus, the direct disruption of EGFR signaling, transcription inhibition, DNA damage, as well as apoptosis induced by hDT806 may contribute to its antitumor efficacy in HNSCC.

A PDK-1 allosteric agonist neutralizes insulin signaling derangements and beta-amyloid toxicity in neuronal cells and in vitro

The Alzheimer's brain is affected by multiple pathophysiological processes, which include a unique, organ-specific form of insulin resistance that begins early in its course. An additional complexity arises from the four-fold risk of Alzheimer's Disease (AD) in type 2 diabetics, however there is no definitive proof of causation. Several strategies to improve brain insulin signaling have been proposed and some have been clinically tested. We report findings on a small allosteric molecule that reverses several indices of insulin insensitivity in both cell culture and in vitro models of AD that emphasize the intracellular accumulation of β-amyloid (Aβi). PS48, a chlorophenyl pentenoic acid, is an allosteric activator of PDK-1, which is an Akt-kinase in the insulin/PI3K pathway. PS48 was active at 10 nM to 1 μM in restoring normal insulin-dependent Akt activation and in mitigating Aβi peptide toxicity. Synaptic plasticity (LTP) in prefrontal cortical slices from normal rat exposed to Aβ oligomers also benefited from PS48. During these experiments, neither overstimulation of PI3K/Akt signaling nor toxic effects on cells was observed. Another neurotoxicity model producing insulin insensitivity, utilizing palmitic acid, also responded to PS48 treatment, thus validating the target and indicating that its therapeutic potential may extend outside of β-amyloid reliance. The described in vitro and cell based-in vitro coupled enzymatic assay systems proved suitable platforms to screen a preliminary library of new analogs.

Ferroptosis Activation Scoring Model Assists in Chemotherapeutic Agents’ Selection and Mediates Cross-Talk With Immunocytes in Malignant Glioblastoma

Gliomas are aggressive tumors in the central nervous system and glioblastoma is the most malignant type. Ferroptosis is a programmed cell death that can modulate tumor resistance to therapy and the components of tumor microenvironment. However, the relationship between ferroptosis, tumor immune landscape, and glioblastoma progression is still elusive. In this work, data from bulk RNA-seq analysis, single cell RNA-seq analysis, and our own data (the Xiangya cohort) are integrated to reveal their relationships. A scoring system is constructed according to ferroptosis related gene expression, and high scoring samples resistant to ferroptosis and show worse survival outcome than low scoring samples. Notably, most of the high scoring samples are aggressive glioblastoma subtype, mesenchymal, and classical, by calculating RNA velocity. Cross-talk between high scoring glioblastoma cells and immunocytes are explored by R package ‘celltalker’. Ligand–receptor pairs like the TRAIL or TWEAK signaling pathway are identified as novel bridges implying how ferroptosis modulate immunocytes’ function and shape tumor microenvironment. Critically, potential drugs target to high scoring samples are predicted, namely, SNX2112, AZ628, and bortezomib and five compounds from the CellMiner database. Taken together, ferroptosis associates with glioblastoma aggressiveness, cross-talk with immunocytes and offer novel chemotherapy strategy.

EGFR-Targeted Pentacyclic Triterpene Analogues for Glioma Therapy

Glioma, particularly its most malignant form, glioblastoma multiforme (GBM), is the most common and aggressive malignant central nervous system tumor. The drawbacks of the current chemotherapy for GBM have aroused curiosity in the search for targeted therapies. Aberrantly overexpressed epidermal growth factor receptor (EGFR) in GBM results in poor prognosis, low survival rates, poor responses to therapy and recurrence, and therefore EGFR-targeted therapy stands out as a promising approach for the treatment of gliomas. In this context, a series of pentacyclic triterpene analogues were subjected to in vitro and in silico assays, which were conducted to assess their potency as EGFR-targeted anti-glioma agents. In particular, compound 10 was the most potent anti-glioma agent with an IC₅₀ value of 5.82 µM towards U251 human glioblastoma cells. Taking into account its low cytotoxicity to peripheral blood mononuclear cells (PBMCs), compound 10 exerts selective antitumor action towards Jurkat human leukemic T-cells. This compound also induced apoptosis and inhibited EGFR with an IC₅₀ value of 9.43 µM compared to erlotinib (IC₅₀ = 0.06 µM). Based on in vitro and in silico data, compound 10 stands out as a potential orally bioavailable EGFR-targeted anti-glioma agent endowed with the ability to cross the blood–brain barrier (BBB).

Neuronal-driven glioma growth requires Gαi1 and Gαi3

Neuroligin-3 (NLGN3) is necessary and sufficient to promote glioma cell growth. The recruitment of Gαi1/3 to the ligand-activated receptor tyrosine kinases (RTKs) is essential for mediating oncogenic signaling.

Methods: Various genetic strategies were utilized to examine the requirement of Gαi1/3 in NLGN3-driven glioma cell growth.

Results: NLGN3-induced Akt-mTORC1 and Erk activation was inhibited by decreasing Gαi1/3 expression. In contrast ectopic Gαi1/3 overexpression enhanced NLGN3-induced signaling. In glioma cells, NLGN3-induced cell growth, proliferation and migration were attenuated by Gαi1/3 depletion with shRNA, but facilitated with Gαi1/3 overexpression. Significantly, Gαi1/3 silencing inhibited orthotopic growth of patient-derived glioma xenografts in mouse brain, whereas forced Gαi1/3-overexpression in primary glioma xenografts significantly enhanced growth. The growth of brain-metastatic human lung cancer cells in mouse brain was largely inhibited with Gαi1/3 silencing. It was however expedited with ectopic Gαi1/3 overexpression. In human glioma Gαi3 upregulation was detected, correlating with poor prognosis.

Conclusion: Gαi1/3 mediation of NLGN3-induced signaling is essential for neuronal-driven glioma growth.

Inhibitory effect of gefitinib derivative LPY‑9 on human glioma

The present study aimed to investigate the effects of a gefitinib derivative, LPY-9, on the proliferation, apoptosis and migration of human glioma cell line U251-MG by CCK8, Transwell or flow cytometry, and the effect of LPY-9 on the activity of caspase-3 enzyme and related proteins in the vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) pathways by western blot and ELISA. It was found that LPY-9 exhibited higher a inhibitory effect on the proliferation of U251-MG cell lines compared with gefitinib and it also exhibited a certain dose-dependence. Following LPY-9 treatment, typical apoptotic morphology was observed under the microscope after Giemsa staining. LPY-9 induced apoptosis at low concentration, and the activity of caspase-3 enzyme increased with the increase in drug concentration, significantly inhibiting the secretion of VEGF in a dose-dependent manner. The effect was notably more evident compared with gefitinib at the same concentration. The expression level of caspase-3 and cleaved caspase-3 increased with the increase in LPY-9 concentration; however, expression levels of VEGF, EGFR, phosphorylated AKT and PI3K decreased with the increase of LPY-9 concentration and no change was observed in the expression level of AKT. LPY-9 inhibited the proliferation of the human glioma cell line U251-MG, promoted apoptosis and effectively inhibited the migration of U251-MG cells. The effect of LPY-9 was more noticeable compared with gefitinib. The results of the present study may provide a foundation for further study and clinical research of this as an anti-tumor drug in animal models.

Rethinking CRITID Procedure of Brain Targeting Drug Delivery: Circulation, Blood Brain Barrier Recognition, Intracellular Transport, Diseased Cell Targeting, Internalization, and Drug Release

The past decades have witnessed great progress in nanoparticle (NP)-based brain-targeting drug delivery systems, while their therapeutic potentials are yet to be fully exploited given that the majority of them are lost during the delivery process. Rational design of brain-targeting drug delivery systems requires a deep understanding of the entire delivery process along with the issues that they may encounter. Herein, this review first analyzes the typical delivery process of a systemically administrated NPs-based brain-targeting drug delivery system and proposes a six-step CRITID delivery cascade: circulation in systemic blood, recognizing receptor on blood-brain barrier (BBB), intracellular transport, diseased cell targeting after entering into parenchyma, internalization by diseased cells, and finally intracellular drug release. By dissecting the entire delivery process into six steps, this review seeks to provide a deep understanding of the issues that may restrict the delivery efficiency of brain-targeting drug delivery systems as well as the specific requirements that may guarantee minimal loss at each step. Currently developed strategies used for troubleshooting these issues are reviewed and some state-of-the-art design features meeting these requirements are highlighted. The CRITID delivery cascade can serve as a guideline for designing more efficient and specific brain-targeting drug delivery systems.

Effect of Ras-guanine nucleotide release factor 1-mediated H-Ras/ERK signaling pathway on glioma

OBJECTIVE

To investigate the function of Ras-guanine nucleotide release factor 1 (Ras-GRF1) in glioma through mediating H-Ras/ERK signaling pathway.

METHODS

Ras-GRF1, H-Ras, K-Ras and N-Ras expressions in glioma and normal brain tissues were detected via Immunohistochemistry. Glioma cells (U87 cells, U251 cells and primary human glioma cells) were transfected with Ras-GRF1 siRNA, H-Ras siRNA and/or Ras-GRF1 lentivirus activation particles. Then, the following aspects were evaluated: cell proliferation by MTT assay, clonogenic ability by the plate clone formation experiment, cell migration and invasion by Wound-healing and Transwell assays, and cell apoptosis by Annexin-V-FITC/PI staining. The protein expressions were measured by Western blotting. Subcutaneous and orthotopic mouse models of glioma were conducted to determine the role of Ras-GRF1 in glioma tumorigenesis.

RESULTS

Ras-GRF1, H-Ras, K-Ras and N-Ras expressions were upregulated in the glioma tissues, which were correlated with the WHO grade of glioma. Besides, Ras-GRF1 expression was positively related to H-Ras expression. Ras-GRF1 siRNA could reduce the expression of H-Ras and p-ERK/ERK in glioma cell. H-Ras siRNA inhibited the proliferation, clone formation, migration and invasion, and enhance the apoptosis of glioma cells, which, however, were reversed by Ras-GRF1 lentivirus activation particles. In vivo experiments also revealed that Ras-GRF1 shRNA reduced the volume and weight of the tumors in the nude mice, with down-regulations of H-Ras and p-ERK/ERK.

CONCLUSION

Ras-GRF1 was upregulated in glioma tissues and correlated with its malignancy and prognosis. Silencing Ras-GRF1, through mediating H-Ras/ERK pathway, may suppress the growth and metastasis of glioma.

SH3KBP1 Promotes Glioblastoma Tumorigenesis by Activating EGFR Signaling

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Overexpression or activation of epidermal growth factor receptor (EGFR) occurs commonly in multiple human cancers and promotes tumorigenesis. However, the underlying molecular mechanism of EGFR aberrant activation and the downstream signaling pathways remains largely unknown. In this study, we report that both SH3-domain kinase binding protein 1 (SH3KBP1) mRNA and protein levels are highly expressed in GBM and its high expression is associated with worse survival of glioma patients. In addition, we provide evidence that SH3KBP1 is prominently expressed in GBM stem cells (GSCs) and have potential to serve as a novel GSCs marker. Moreover, silencing SH3KBP1 dramatically impairs GBM cell proliferation, migration and GSCs self-renewal ability in vitro and xenograft tumors growth in vivo. Most importantly, we found that SH3KBP1 directly interacts with EGFR and may act as an adaptor protein to transduce EGFR signaling. Together, our work uncovers SH3KBP1 as a novel regulator of oncogenic EGFR signaling and also as a potential therapeutic target for GBM patients with EGFR activation.

Synthesis, characterization and preliminary biological evaluation of chrysin amino acid derivatives that induce apoptosis and EGFR downregulation

Chrysin amino acid derivatives were synthesized to evaluate for their antiproliferative activities. Among them, N-(7-((5-hydroxy-4-oxo-2-phenyl-4H-chromen-7-yl)oxy)valeryl)-L-leucine (8c) displayed the most remarkable inhibitory activities against MCF-7 cells with IC₅₀ values of 16.6 μM. Preliminary mechanistic studies showed that 8c could inhibit the colony formation and migration of MCF-7 cells. Flow cytometry analysis demonstrated that 8c mediated cell apoptosis and the prolongation of cell cycle progression in G1/S-phase against MCF-7 cells. Besides, 8c displayed the moderate inhibition against EGFR. Western blot assay suggested that 8c significantly inhibited EGFR phosphorylation. Molecular docking showed that 8c can bind the EGFR kinase well.

Disentangling the therapeutic tactics in GBM: From bench to bedside and beyond

Glioblastoma multiforme (GBM) is one of the most common and malignant form of adult brain tumor with a high mortality rate and dismal prognosis. The present standard treatment comprising surgical resection followed by radiation and chemotherapy using temozolomide can broaden patient's survival to some extent. However, the advantages are not palliative due to the development of resistance to the drug and tumor recurrence following the multimodal treatment approaches due to both intra- and intertumoral heterogeneity of GBM. One of the major contributors to temozolomide resistance is O⁶ -methylguanine-DNA methyltransferase. Furthermore, deficiency of mismatch repair, base excision repair, and cytoprotective autophagy adds to temozolomide obstruction. Rising proof additionally showed that a small population of cells displaying certain stem cell markers, known as glioma stem cells, adds on to the resistance and tumor progression. Collectively, these findings necessitate the discovery of novel therapeutic avenues for treating glioblastoma. As of late, after understanding the pathophysiology and biology of GBM, some novel therapeutic discoveries, such as drug repurposing, targeted molecules, immunotherapies, antimitotic therapies, and microRNAs, have been developed as new potential treatments for glioblastoma. To help illustrate, "what are the mechanisms of resistance to temozolomide" and "what kind of alternative therapeutics can be suggested" with this fatal disease, a detailed history of these has been discussed in this review article, all with a hope to develop an effective treatment strategy for GBM.

The Role of Hormones and Trophic Factors as Components of Preservation Solutions in Protection of Renal Function before Transplantation: A Review of the Literature

Transplantation is currently a routine method for treating end-stage organ failure. In recent years, there has been some progress in the development of an optimal composition of organ preservation solutions, improving the vital functions of the organ and allowing to extend its storage period until implantation into the recipient. Optimizations are mostly based on commercial solutions, routinely used to store grafts intended for transplantation. The paper reviews hormones with a potential nephroprotective effect, which were used to modify the composition of renal perfusion and preservation solutions. Their effectiveness as ingredients of preservation solutions was analysed based on a literature review. Hormones and trophic factors are innovative preservation solution supplements. They have a pleiotropic effect and affect normal renal function. The expression of receptors for melatonin, prolactin, thyrotropin, corticotropin, prostaglandin E1 and trophic factors was confirmed in the kidneys, which suggests that they are a promising therapeutic target for renal IR (ischemia-reperfusion) injury. They can have anti-inflammatory, antioxidant and anti-apoptotic effects, limiting IR injury.

Ninjurin2 overexpression promotes glioma cell growth

Ninjurin2 (Ninj2) is an adhesion protein expressed in neurons and glial cells. The current study tested its expression and potential functions in human glioma. We show that Ninj2 mRNA and protein levels are significantly upregulated in human glioma cells and tissues. In established and primary human glioma cells, Ninj2 shRNA or knockout (by CRISPR/Cas9 gene editing) potently inhibited cell survival, growth, proliferation, cell migration and invasion, while inducing apoptosis activation. Contrarily, ectopic overexpression of Ninj2 promoted glioma cell progression in vitro. In human glioma tissues and cells, Ninj2 co-immunoprecipitated with multiple receptor tyrosine kinases (EGFR, PDGFRβ and FGFR), required for downstream Akt and Erk activation. Akt and Erk activation was potently inhibited by Ninj2 shRNA or knockout, but enhanced with ectopic Ninj2 overexpression in glioma cells. In summary, we show that Ninj2 overexpression promotes glioma cell growth.

The synergistic effect of DZ‑NEP, panobinostat and temozolomide reduces clonogenicity and induces apoptosis in glioblastoma cells

Current treatment against glioblastoma consists of surgical resection followed by temozolomide, with or without combined radiotherapy. Glioblastoma frequently acquires resistance to chemotherapy and/or radiotherapy. Novel therapeutic approaches are thus required. The inhibition of enhancer of zeste homolog 2 (EZH2; a histone methylase) and histone deacetylases (HDACs) are possible epigenetic treatments. Temozolomide, 3‑deazaneplanocin A (DZ‑Nep; an EZH2 inhibitor) and panobinostat (an HDAC inhibitor) were tested in regular and temozolomide‑resistant glioblastoma cells to confirm whether the compounds could behave in a synergistic, additive or antagonistic manner. A total of six commercial cell lines, two temozolomide‑induced resistant cell lines and two primary cultures derived from glioblastoma samples were used. Cell lines were exposed to single treatments of the drugs in addition to all possible two‑ and three‑drug combinations. Colony formation assays, synergistic assays and reverse transcription‑quantitative PCR analysis of apoptosis‑associated genes were performed. The highest synergistic combination was DZ‑Nep + panobinostat. Triple treatment was also synergistic. Reduced clonogenicity and increased apoptosis were both induced. It was concluded that the therapeutic potential of the combination of these three drugs in glioblastoma was evident and should be further explored.

Combining Ellagic Acid with Temozolomide Mediates the Cadherin Switch and Angiogenesis in a Glioblastoma Model

OBJECTIVE

We aimed to evaluate the combined effect of ellagic acid (EA) and temozolomide (TEM) on the cadherin switch and angiogenesis in the C6 glioma cell line.

METHODS

A total of 100 μM EA and 100 μM TEM were applied to rat C6 glioma cells for 24, 48, and 72 hours. Cell proliferation was detected by 5-bromo-2'-deoxyuridine immunohistochemistry. The messenger RNA and protein levels of E-cadherin, N-cadherin, and vascular endothelial growth factor (VEGF) were determined by real-time polymerase chain reaction and their immunohistochemistry, respectively, subsequent to EA treatment combined with TEM.

RESULTS

EA in combination with TEM conspicuously reduced the viability of C6 glioma cells at all incubation times (P < 0.001). EA upregulated the expression of E-cadherin at the gene and protein levels in a time-independent manner (P < 0.05 and P < 0.001, respectively). By the presence of TEM, the increase was exaggerated at 24-hour incubation (P < 0.01). Conversely, EA reduced N-cadherin expression and immunoreactivity in a time-independent manner (P < 0.05 and P < 0.001, respectively), and combination with TEM enhanced this effect at the 24th hour (P < 0.001). Combination also downregulated the gene expression (P < 0.001) and immunoreactivity of VEGF only at 72 hours (P < 0.001).

CONCLUSIONS

A successful therapeutic efficacy of EA combined with TEM is suggested probably by inhibiting the cadherin switch and angiogenesis.

Filamin A regulates EGFR/ERK/Akt signaling and affects colorectal cancer cell growth and migration

The metastasis and recurrence rate, and the overall prognosis of colorectal cancer (CRC) remain unsatisfactory. Filamin A (FLNa), as an actin-binding protein, can interact with various signaling molecules and membrane receptors to affect cell signal transduction and function. However, whether FLNa is involved in the progression of CRC remains to be elucidated. The aim of the present study was to explore the role of FLNa in CRC cell proliferation and migration, as well as in the regulation of epidermal growth factor receptor (EGFR) signaling. Following transfection with a FLNa-targeting short hairpin RNA plasmid to knockdown expression of FLNa in the EGF-treated SW480 cell line, it was found that decreased expression of FLNa promoted cell proliferation and migration. Additionally, there was a negative correlation between FLNa levels and the activation of EGFR and Akt signaling pathways. Similarly, the expression of FLNa was significantly lower in human CRC tissues compared with adjacent normal tissues and FLNa expression was negatively correlated with the expression of Ki-67 in human CRC tissues. Although there was no significant difference in the Kaplan-Meier estimate of CRC between high expression and low expression of FLNa, there were significant negative associations between FLNa expression and TNM stage. The results suggested that FLNa may participate in EGF-induced cell proliferation and migration in CRC cells. Hence, interventions in the FLNa-mediated signaling pathway could provide attractive therapeutic targets for CRC.

Ursolic acid suppresses the biological function of osteosarcoma cells

Osteosarcoma is a highly malignant tumour that occurs in adolescents. Upregulation or the constitutive activation of epidermal growth factor receptor (EGFR) is a hallmark of osteosarcoma. To investigate the effect of ursolic acid on the biological function of osteosarcoma, MTT assay was used to detect the effect of ursolic acid on the proliferation of HOS and MG63 cells, while flow cytometry was used to analyse the effect on the cell cycle and apoptosis. Transwell and Matrigel assays were used to detect the effect of ursolic acid on cell migration and invasion, respectively. Western blot analysis and reverse transcription-quantitative polymerase chain reaction were used to detect the effects of different concentrations of ursolic acid on EGFR signaling pathway-related proteins, cell cycle, apoptosis and cell migration-related proteins. After overexpression or silencing of EGFR, the effects of ursolic acid on EGFR pathway and cell biological function were subsequently detected, using the same methods. The present study identified that ursolic acid had inhibitory effects on the growth and metastatic ability of osteosarcoma cells by suppressing EGFR.

The tumor suppressor FOXO3a mediates the response to EGFR inhibition in glioblastoma cells

PURPOSE

Although EGFR activation is a hallmark of glioblastoma (GBM), anti-EGFR therapy has so far not yielded the desired effects. Targeting PI3K/Akt has been proposed as a strategy to increase the cellular sensitivity to EGFR inhibitors. Here we evaluated the contribution of FOXO3a, a key Akt target, in the response of GBM cells to EGFR inhibition.

METHODS

FOXO3a activation was assessed by immunofluorescence and gene reporter assays, and by evaluating target gene expression using Western blotting and qRT-PCR. Cellular effects were evaluated using cell viability and apoptosis assays, i.e., Annexin V/PI staining and caspase 3/7 activity measurements. Drug synergism was evaluated by performing isobolographic analyses. Gene silencing experiments were performed using stable shRNA transfections.

RESULTS

We found that EGFR inhibition in GBM cells led to FOXO3a activation and to transcriptional modulation of its key targets, including repression of the oncogene FOXM1. In addition, we found that specific FOXO3a activation recapitulated the molecular effects of EGFR inhibition, and that the FOXO3a activator trifluoperazine, a FDA-approved antipsychotic agent, reduced GBM cell growth. Subsequent isobolographic analyses of combination experiments indicated that trifluoperazine and erlotinib cooperated synergistically and that their concomitant treatment induced a robust activation of FOXO3a, leading to apoptosis in GBM cells. Using gene silencing, we found that FOXO3a is essential for the response of GBM cells to EGFR inhibition.

CONCLUSIONS

Our data indicate that FOXO3a activation is a crucial event in the response of GBM cells to EGFR inhibition, suggesting that FOXO3a may serve as an actionable therapeutic target that can be modulated using FDA-approved drugs.

EGFRvIII Is Expressed in Cellular Areas of Tumor in a Subset of Glioblastoma

Epidermal growth factor receptor variant III (EGFRvIII) is a tumor-specific cell surface antigen often expressed in glioblastoma and has drawn much attention as a possible therapeutic target. We performed immunohistochemistry on histology sections of surgical specimens taken from 67 cases with glioblastoma, isocitrate dehydrogenase-wild type, and evaluated the morphological characteristics and distribution of the EGFRvIII-positive tumor cells. We then evaluated the localization of EGFRvIII-expression within the tumor and peritumoral areas. EGFRvIII immunopositivity was detected in 15 specimens taken from 13 patients, including two recurrent specimens taken from the same patient at relapse. Immunofluorescence staining demonstrated that EGFRvIII-positive cells were present in cells positive for glial fibrillary acidic protein (GFAP), and some showed astrocytic differentiation with multiple fine processes and others did not shown. The EGFRvIII-positive cells were located in cellular areas of the tumor, but not in the invading zone. In the two recurrent cases, EGFRvIII-positive cells were markedly decreased in one case and retained in the other. With regard to overall survival, univariate analysis indicated that EGFRvIII-expression in patients with glioblastoma was not significantly associated with a favorable outcome. Double-labeling immunofluorescence staining of EGFRvIII and GFAP showed that processes of large, well differentiated, GFAP-positive glia extend to and surround less differentiated, EGFRvIII-positive glial cells in cellular areas of tumor. However, in the tumor periphery, EGFRvIII-positive tumor cells were not observed. This finding suggests that EGFRvIII is involved in tumor proliferation, but that invading glioma cells lose their EGFRvIII expression.

SYK inhibition blocks proliferation and migration of glioma cells and modifies the tumor microenvironment

Background

Glioblastoma (GBM) is one of the most aggressive human brain tumors, with a median survival of 15-18 months. There is a desperate need to find novel therapeutic targets. Various receptor protein kinases have been identified as potential targets; however, response rates in clinical studies have been somewhat disappointing. Targeting the spleen tyrosine kinase (SYK), which acts downstream of a range of oncogenic receptors, may therefore show more promising results.

Methods

Kinase expression of brain tumor samples including GBM and low-grade tumors were compared with normal brain and normal human astrocytes by microarray analysis. Furthermore, SYK, LYN, SLP76, and PLCG2 protein expressions were analyzed by immunohistochemistry, western blot, and immunofluorescence of additional GBM patient samples, murine glioma samples, and cell lines. SYK was then blocked chemically and genetically in vitro and in vivo in 2 different mouse models. Multiphoton intravital imaging and multicolor flow cytometry were performed in a syngeneic immunocompetent C57BL/6J mouse GL261 glioma model to study the effect of these inhibitors on the tumor microenvironment.

Results

SYK, LYN, SLP76, and PLCG2 were found expressed in human and murine glioma samples and cell lines. SYK inhibition blocked proliferation, migration, and colony formation. Flow cytometric and multiphoton imaging imply that targeting SYK in vivo attenuated GBM tumor growth and invasiveness and reduced B and CD11b+ cell mobility and infiltration.

Conclusions

Our data suggest that gliomas express a SYK signaling network important in glioma progression, inhibition of which results in reduced invasion with slower tumor progression.

Discovery and Therapeutic Exploitation of Mechanisms of Resistance to MET Inhibitors in Glioblastoma

PURPOSE

Glioblastoma (GBM) is the most common and most lethal primary malignant brain tumor. The receptor tyrosine kinase MET is frequently upregulated or overactivated in GBM. Although clinically applicable MET inhibitors have been developed, resistance to single modality anti-MET drugs frequently occurs, rendering these agents ineffective. We aimed to determine the mechanisms of MET inhibitor resistance in GBM and use the acquired information to develop novel therapeutic approaches to overcome resistance.Experimental Design: We investigated two clinically applicable MET inhibitors: crizotinib, an ATP-competitive small molecule inhibitor of MET, and onartuzumab, a monovalent monoclonal antibody that binds to the extracellular domain of the MET receptor. We developed new MET inhibitor-resistant cells lines and animal models and used reverse phase protein arrays (RPPA) and functional assays to uncover the compensatory pathways in MET inhibitor-resistant GBM.

RESULTS

We identified critical proteins that were altered in MET inhibitor-resistant GBM including mTOR, FGFR1, EGFR, STAT3, and COX-2. Simultaneous inhibition of MET and one of these upregulated proteins led to increased cell death and inhibition of cell proliferation in resistant cells compared with either agent alone. In addition, in vivo treatment of mice bearing MET-resistant orthotopic xenografts with COX-2 or FGFR pharmacological inhibitors in combination with MET inhibitor restored sensitivity to MET inhibition and significantly inhibited tumor growth.

CONCLUSIONS

These data uncover the molecular basis of adaptive resistance to MET inhibitors and identify new FDA-approved multidrug therapeutic combinations that can overcome resistance.

Connexin 43 C-terminus directly inhibits the hyperphosphorylation of Akt/ERK through protein-protein interactions in glioblastoma

Although the deregulation of epidermal growth factor receptor (EGFR) is one of the most common molecular mechanisms of glioblastoma (GBM) pathogenesis, the efficacy of anti-EGFR therapy is limited. Additionally, response to anti-EGFR therapy is not solely dependent on EGFR expression and is more promising in patients with reduced activity of EGFR downstream signaling pathways. Thus, there is considerable interest in identifying the compensatory regulatory factors of the EGFR signaling pathway to improve the efficacy of anti-EGFR therapies for GBM. In this study, we confirmed the low efficacy of EGFR inhibitors in GBM patients by meta-analysis. We then identified a negative correlation between connexin 43 (Cx43) expression and Akt/ERK activation, which was caused by the direct interactions between Akt/ERK and Cx43. By comparing the interactions between Akt/ERK and Cx43 using a series of truncated and mutated Cx43 variants, we revealed that the residues T286/A305/Q308/Y313 and S272/S273 at the carboxy terminus of Cx43 are critical for its binding with Akt and ERK, respectively. In addition, Kaplan-Meier survival analysis using data from The Cancer Genome Atlas datasets indicated that the expression of Cx43 significantly improved the prognosis of GBM patients who express EGFR. Together, our results suggested that Cx43 acts as an inhibitory regulator of the activation of growth factor receptor downstream signaling pathways, indicating the potential of Cx43 as a marker for predicting the efficacy of EGFR inhibitor treatments for GBM. Targeting the interaction between the carboxy terminus of Cx43 and Akt/ERK could be an effective therapeutic strategy against GBM.

Linderane Suppresses Hepatic Gluconeogenesis by Inhibiting the cAMP/PKA/CREB Pathway Through Indirect Activation of PDE 3 via ERK/STAT3

The role of phosphodiesterase 3 (PDE3), a cyclic AMP (cAMP)-degrading enzyme, in modulating gluconeogenesis remains unknown. Here, linderane, a natural compound, was found to inhibit gluconeogenesis by activating hepatic PDE3 in rat primary hepatocytes. The underlying molecular mechanism and its effects on whole-body glucose and lipid metabolism were investigated. The effect of linderane on gluconeogenesis, cAMP content, phosphorylation of cAMP-response element-binding protein (CREB) and PDE activity were examined in cultured primary hepatocytes and C57BL/6J mice. The precise mechanism by which linderane activates PDE3 and inhibits the cAMP pathway was explored using pharmacological inhibitors. The amelioration of metabolic disorders was observed in ob/ob mice. Linderane inhibited gluconeogenesis, reduced phosphoenolpyruvate carboxykinase (Pck1) and glucose-6-phosphatase (G6pc) gene expression, and decreased intracellular cAMP concentration and CREB phosphorylation in rat primary hepatocytes under both basal and forskolin-stimulated conditions. In rat primary hepatocytes, it also increased total PDE and PDE3 activity but not PDE4 activity. The suppressive effect of linderane on the cAMP pathway and gluconeogenesis was abolished by the non-specific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX) and the specific PDE3 inhibitor cilostazol. Linderane indirectly activated PDE3 through extracellular regulated protein kinase 1/2 (ERK1/2) and signal transducer and activator of transcription 3 (STAT3) activation. Linderane improved glucose and lipid metabolism after chronic oral administration in ob/ob mice. Our findings revealed linderane as an indirect PDE3 activator that suppresses gluconeogenesis through cAMP pathway inhibition and has beneficial effects on metabolic syndromes in ob/ob mice. This investigation highlighted the potential for PDE3 activation in the treatment of type 2 diabetes.

Sym004-induced EGFR elimination is associated with profound anti-tumor activity in EGFRvIII patient-derived glioblastoma models

BACKGROUND

Sym004 is a mixture of two monoclonal antibodies (mAbs), futuximab and modotuximab, targeting non-overlapping epitopes on the epidermal growth factor receptor (EGFR). Previous studies have shown that Sym004 is more efficient at inducing internalization and degradation of EGFR than individual components, which translates into superior cancer cell inhibition. We investigated whether Sym004 induces removal of EGFRvIII and if this removal translates into tumor growth inhibition in hard-to-treat glioblastomas (GBMs) harboring the mutated, constitutively active EGFR variant III (EGFRvIII).

METHODS

To address this question, we tested the effect of Sym004 versus cetuximab in eight patient-derived GBM xenograft models expressing either wild-type EGFR (EGFRwt) and/or mutant EGFRvIII. All models were tested as both subcutaneous and orthotopic intracranial xenograft models.

RESULTS

In vitro studies demonstrated that Sym004 internalized and removed EGFRvIII more efficiently than mAbs, futuximab, modotuximab, and cetuximab. Removal of EGFRvIII by Sym004 translated into significant in vivo anti-tumor activity in all six EGFRvIII xenograft models. Furthermore, the anti-tumor activity of Sym004 in vivo was superior to that of its individual components, futuximab and modotuximab, suggesting a clear synergistic effect of the mAbs in the mixture.

CONCLUSION

These results demonstrate the broad activity of Sym004 in patient-derived EGFRvIII-expressing GBM xenograft models and provide a clear rationale for clinical evaluation of Sym004 in EGFRvIII-positive adult GBM patients.

microRNA-200a downregulation in human glioma leads to Gαi1 over-expression, Akt activation, and cell proliferation

We previously identified a pivotal role for G protein α inhibitory subunit 1 (Gαi1) in mediating PI3K-Akt signaling by receptor tyrosine kinases (RTKs). Here, we examined the expression and biological function of Gαi1 in human glioma. Gαi1 mRNA and protein expression were significantly upregulated in human glioma tissues, which correlated with downregulation of an anti-Gαi1 miRNA: microRNA-200a ("miR-200a"). Forced-expression of miR-200a in established (A172/U251MG lines) and primary (patient-derived) human glioma cells resulted in Gαi1 downregulation, Akt inactivation and proliferation inhibition. Reduction of Gαi1 expression by shRNA, dominant negative mutant interference, or complete Gαi1 depletion inhibited Akt activation and cell proliferation. Notably, miR-200a was unable to inhibit glioma cell proliferation when Gαi1 was silenced or mutated. Co-immunoprecipitation studies, in human glioma cells and tissues, show that Gαi1 forms a complex with multiple RTKs (EGFR, PDGFRα, and FGFR) and the adapter protein Gab1. In vivo, the growth of subcutaneous and orthotopic glioma xenografts in nude mice was largely inhibited by expression of Gαi1 shRNA or miRNA-200a. Collectively, miR-200a downregulation in human glioma leads to Gαi1 over-expression, Akt activation and glioma cell proliferation.

Crizotinib and erlotinib inhibits growth of c-Met+/EGFRvIII+ primary human glioblastoma xenografts

OBJECTIVES

Receptor tyrosine kinases (RTK), such as c-Met and epidermal growth factor receptor (EGFR), are implicated in the malignant progression of glioblastoma. Studies show that RTK systems can co-modulate distinct and overlapping oncogenic downstream signaling pathways. EGFRvIII, a constitutively activated EGFR deletion mutant variant, leads to increased tumor growth and diminishes the tumor growth response to HGF: c-Met pathway inhibitor therapy. Conversely, activation of the c-Met pathway diminishes the tumor growth response to EGFR pathway inhibitors. Previously we reported that EGFRvIII and c-Met pathway inhibitors synergize to inhibit tumor growth in isogenic GBM cell lines engineered to express EGFRvIII. More recently, studies suggest that despite targeting RTK signaling in glioblastoma multiforme, a subpopulation of stem-like tumor-propagating cells can persist to replenish the tumor cell population leading to tumor recurrence.

PATIENTS AND METHODS

Mayo 39 and Mayo 59 xenograft lines were cultured and xenografts were maintained. Subcutaneous xenograft lines were serially passaged in nude mice to generate subcutaneous xenografts. Xenografts were implanted in 6-8 week old nude mice. Once tumors reached a substantial size (150 mm³), mice were randomly divided into 4 groups: 1) control vehicle, 2) Crizotinib (crizo), 3) Erlotinib (erlot), or 4) Crizotinib + Erlotinib, (n = 5 per group).

RESULTS

Crizotinib (c-Met pathway inhibitor) and Erlotinib (EGFR pathway inhibitor) in combination significantly inhibited tumor growth, phospho-EGFRvIII, phospho-Met, phospho-AKT, phospho-MAPK, and neurosphere growth in Mayo 39 and Mayo 59 primary GBM subcutaneous xenografts. The expression of the stem cell markers Nestin, Musashi, Olig 2 and Sox2 were also significantly down-regulated by c-Met inhibition, but no additive down-regulation was seen by co-treatment with Erlotinib.

CONCLUSIONS

These results are consistent with and corroborate our previous findings demonstrating that targeting these two parallel pathways with c-Met and EGFR inhibitor therapy provides substantial anti-tumor activity in glioblastoma models.

mTOR regulates proteasomal degradation and Dp1/E2F1- mediated transcription of KPNA2 in lung cancer cells

Karyopherin subunit alpha-2 (KPNA2) is overexpressed in various human cancers and is associated with cancer invasiveness and poor prognosis in patient. Nevertheless, the regulation of KPNA2 expression in cancers remains unclear. We herein applied epidermal growth factor (EGF) and five EGF receptor (EGFR)-related kinase inhibitors to investigate the role of EGFR signaling in KPNA2 expression in non-small cell lung cancer (NSCLC) cells. We found that EGFR signaling, particularly the mammalian target of rapamycin (mTOR) activity was positively correlated with KPNA2 protein levels in NSCLC cells. The mTOR inhibitors and mTOR knockdown reduced the protein and mRNA levels of KPNA2 in NSCLC and breast cancer cells. Specifically, rapamycin treatment induced proteasome-mediated KPNA2 protein decay and attenuated the transcriptional activation of KPNA2 by decreasing Dp1/E2F1 level in vivo. Immunoprecipitation assay further revealed that KPNA2 physically associated with the phospho-mTOR/mTOR and this association was abolished by rapamycin treatment. Collectively, our results show for the first time that KPNA2 is transcriptionally and post-translationally regulated by the mTOR pathway and provide new insights into targeted therapy for NSCLC.

Redirecting T-Cell Specificity to EGFR Using mRNA to Self-limit Expression of Chimeric Antigen Receptor

Potential for on-target, but off-tissue toxicity limits therapeutic application of genetically modified T cells constitutively expressing chimeric antigen receptors (CARs) from tumor-associated antigens expressed in normal tissue, such as epidermal growth factor receptor (EGFR). Curtailing expression of CAR through modification of T cells by in vitro-transcribed mRNA species is one strategy to mitigate such toxicity. We evaluated expression of an EGFR-specific CAR coded from introduced mRNA in human T cells numerically expanded ex vivo to clinically significant numbers through coculture with activating and propagating cells (AaPC) derived from K562 preloaded with anti-CD3 antibody. The density of AaPC could be adjusted to affect phenotype of T cells such that reduced ratio of AaPC resulted in higher proportion of CD8 and central memory T cells that were more conducive to electrotransfer of mRNA than T cells expanded with high ratios of AaPC. RNA-modified CAR T cells produced less cytokine, but demonstrated similar cytolytic capacity as DNA-modified CAR T cells in response to EGFR-expressing glioblastoma cells. Expression of CAR by mRNA transfer was transient and accelerated by stimulation with cytokine and antigen. Loss of CAR abrogated T-cell function in response to tumor and normal cells expressing EGFR. We describe a clinically applicable method to propagate and modify T cells to transiently express EGFR-specific CAR to target EGFR-expressing tumor cells that may be used to limit on-target, off-tissue toxicity to normal tissue.

HB-EGF is associated with DNA damage and Mcl-1 turnover in human glioma cell lines treated by Temozolomide

Temozolomide (TMZ) is the main chemotherapeutic agent used for treating newly diagnosed Glioblastoma Multiforme (GBM), the most frequent malignant brain tumors in adults. This alkylating agent induces DNA double strand breaks (DSBs) which in turn lead to apoptosis by activating the Bcl-2 controlled mitochondrial pathway. However, GBM invariably recur as tumors become resistant to TMZ. We investigated the implication of EGFR ligands in this resistance and we found that the pro Heparin Binding Epidermal Growth Factor (proHB-EGF) expression is linked to the early response to TMZ in human glioma cell lines. However, HB-EGF does not affect apoptosis per se although its expression is associated with the degradation of Mcl-1. HB-EGF is implicated in DSBs repair as silencing of HB-EGF increased γH2AX foci half-life as well as USP9X expression, two features that could be linked to the observed effect on Mcl-1. Our data demonstrate a new role for HB-EGF in TMZ treated cell lines.

Chemoresistance in cancer cells: exosomes as potential regulators of therapeutic tumor heterogeneity

Drug resistance in cancer cells remains a fundamental challenge. Be it nontargeted or targeted drugs, the presence of intrinsic or acquired cancer cell resistance remains a great obstacle in chemotherapy. Conventionally, a spectrum of cellular mechanisms defines drug resistance including overexpression of antiapoptotic proteins and drug efflux pumps, mutations in target and synergistic activation of prosurvival pathways in tumor cells. In addition to these well-studied routes, exosome-induced chemoresistance is emerging as a novel mechanism. Mechanistically, exosomes impart resistance by direct drug export, transport of drug efflux pumps and miRNAs exchange among cells. Moreover, exosome signaling creates ‘therapeutic tumor heterogeneity’ and favorably condition tumor microenvironment. Here, we discuss exosomes’ role in chemoresistance and possibilities of developing novel therapeutic strategies.

EGFR/EGFRvIII Dual-Targeting Peptide-Mediated Drug Delivery for Enhanced Glioma Therapy

Tumor-homing peptides have been widely used to mediate active targeted drug delivery. l-AE is a reported targeting peptide demonstrating high binding affinity to epidermal growth factor receptor (EGFR) and mutation variant III (EGFRvIII) overexpressed on neovasculature, vasculogenic mimicry, tumor cells, and tumor stem cells. To improve its proteolytic stability, a d-peptide ligand (termed d-AE, the enantiomer of l-AE) was developed. d-AE was confirmed to bind receptors EGFR and EGFRvIII with targeting capability comparable to l-AE. In vivo biodistribution demonstrated the superiority of d-AE in prolonged circulation and enhanced intratumoral accumulation. Furthermore, stabilized peptide modification endowed micelles higher transcytosis efficiency and penetrating capability on blood-brain tumor barrier/U87 tumor spheroids coculture model. When paclitaxel (PTX) was loaded, d-AE-micelle/PTX demonstrated excellent antitumor effect in comparison to Taxol, micelle/PTX, and l-AE-micelle/PTX. These findings indicated that the multitargeted drug delivery system enabled by d-AE ligand provides a promising way for glioma therapy.

Exosomes as a biomarker platform for detecting epidermal growth factor receptor-positive high-grade gliomas

OBJECTIVE High-grade glial brain tumors are often characterized by an elevated expression of the tumorigenic epidermal growth factor receptor variant III ( EGFRvIII). The authors sought to establish a clinically adaptive protocol as a noninvasive diagnostic tool for EGFRvIII detection through serum exosomes. METHODS Purity of serum exosome/RNA was confirmed by electron microscopy and flow cytometry and through an RNA bioanalyzer profile. EGFRvIII amplification was initially established by semiquantitative polymerase chain reaction in tumor tissues and exosomes. Diagnostic performance of EGFRvIII transcript in tissue versus exosome was determined using a 2 × 2 clinical table approach. Overall survival was determined using Kaplan-Meier analysis. RESULTS The EGFRvIII transcript was detected in 39.5% of tumor tissue samples and in 44.7% of their paired serum exosome samples; 28.1% of biopsy tumors coexpressed wild-type EGFR and EGFRvIII. Tissue EGFRvIII amplification served as the reference-positive control for its paired serum expression. The overall clinical sensitivity and specificity of semiquantitative exosome EGFRvIII polymerase chain reaction detection assay in serum were 81.58% (95% CI 65.67%-92.26%) and 79.31% (95% CI 66.65%-88.83%), respectively. Age, sex, tumor location, and side of the body on which the tumor was located had no effect on the detection rate of exosomal EGFRvIII transcript. EGFRvIII expression either in exosomes or tissue correlated with poor survival. CONCLUSIONS The authors established a serum-based method for detection of EGFRvIII in high-grade brain tumors that might serve as an optimal noninvasive method for diagnosing EGFRvIII-positive high-grade gliomas.

Gene Expression Profiling of Chemokines and Their Receptors in Low and High Grade Astrocytoma

Background: Despite intense interest in molecular characterization and searches for novel therapeutic targets, the glioblastoma remains a formidable clinical challenge. Among many contributors to gliomagenesis, chemokines have drawn special attention due to their involvement in a plethora of biological processes and pathological conditions. In the present study we aimed to elucidate any pro-gliomagenic chemokine axis and probable roles in development of glioblastoma multiforme (GBM). Method: An array of 84 chemokines, chemokine receptors and related genes were studied by real time PCR with comparison between low grade astrocytoma (diffuse astrocytoma – grade II) and high grade astrocytoma (glioblastoma multiforme – grade IV). Gene ontology analysis and database mining were performed to funnel down the important axis in GBM followed by validation at the protein level by immunohistochemistry on tissue microarrays. Results: Gene expression and gene ontology analysis identified CXCL8 as an important chemokine which was more frequently up-regulated in GBM as compared to diffuse astrocytoma. Further we demonstrated localization of CXCL8 and its receptors in glioblastoma possibly affecting autocrine and paracrine signalling that promotes tumor cell proliferation and neovascularisation with vascular mimicry. Conclusion: From these results CXCL8 appears to be an important gliomagenic chemokine which may be involved in GBM growth by promoting tumor cell proliferation and neovascularization via vascular mimicry. Further in vitro and in vivo investigations are required to explore its potential candidature in anti-GBM therapy.

Peptide-based PET imaging of the tumor restricted IL13RA2 biomarker

Peptides that target cancer cell surface receptors are promising platforms to deliver diagnostic and therapeutic payloads specifically to cancer but not normal tissue. IL13RA2 is a tumor-restricted receptor found to be present in several aggressive malignancies, including in the vast majority of high-grade gliomas and malignant melanoma. This receptor has been successfully targeted for diagnostic and therapeutic purposes using modified IL-13 ligand and more recently using a specific peptide, Pep-1L. In the current work, we establish the in vitro and in vivo tumor binding properties of radiolabeled Pep-1L, designed for tumor imaging. We radiolabeled Pep-1L with Copper-64 and demonstrated specific cell uptake in the IL13RA2-over expressing G48 glioblastoma cell line having abundant IL13RA2 expression. [⁶⁴Cu]Pep-1L binding was blocked by unlabeled ligand, demonstrating specificity. To demonstrate in vivo tumor uptake, we intravenously injected into tumor-bearing mice and demonstrated that [⁶⁴Cu]Pep-1L specifically bound tumors at 24 hours, which was significantly blocked (3-fold) by pre-injecting unlabeled peptide. To further demonstrate specificity of Pep-1L towards IL13RA2 in vivo, we exploited an IL13RA2-inducible melanoma tumor model that does not express receptor at baseline but expresses abundant receptor after treatment with doxycycline. We injected [⁶⁴Cu]Pep-1L into mice bearing IL13RA2-inducible melanoma tumors and performed in vivo PET/CT and post-necropsy biodistribution studies and found that tumors that were induced to express IL13RA2 receptor by doxycycline pretreatment bound radiolabeled Pep-1L 3-4 fold greater than uninduced tumors, demonstrating receptor specificity. This work demonstrates that [⁶⁴Cu]Pep-1L selectively binds hIL13RA2-expressing tumors and validates Pep-1L as an effective platform to deliver diagnostics and therapeutics to IL13RA2-expressing cancers.

Pluronic-based micelle encapsulation potentiates myricetin-induced cytotoxicity in human glioblastoma cells

As one of the natural herbal flavonoids, myricetin has attracted much research interest, mainly owing to its remarkable anticancer properties and negligible side effects. It holds great potential to be developed as an ideal anticancer drug through improving its bioavailability. This study was performed to investigate the effects of Pluronic-based micelle encapsulation on myricetin-induced cytotoxicity and the mechanisms underlying its anticancer properties in human glioblastoma cells. Cell viability was assessed using a methylthiazol tetrazolium assay and a real-time cell analyzer. Immunoblotting and quantitative reverse transcriptase polymerase chain reaction techniques were used for determining the expression levels of related molecules in protein and mRNA. The results indicated that myricetin-induced cytotoxicity was highly potentiated by the encapsulation of myricetin. Mitochondrial apoptotic pathway was demonstrated to be involved in myricetin-induced glioblastoma cell death. The epidermal growth factor receptor (EGFR)/PI3K/Akt pathway located in the plasma membrane and cytosol and the RAS-ERK pathway located in mitochondria served as upstream and downstream targets, respectively, in myricetin-induced apoptosis. MiR-21 inhibitors interrupted the expression of EGFR, p-Akt, and K-Ras in the same fashion as myricetin-loaded mixed micelles (MYR-MCs) and miR-21 expression were dose-dependently inhibited by MYR-MCs, indicating the interaction of miR-21 with MYR-MCs. This study provided evidence supportive of further development of MYR-MC formulation for preferentially targeting mitochondria of glioblastoma cells.