A critical evaluation of PI3K inhibition in Glioblastoma and Neuroblastoma therapy

RND1 inhibits epithelial-mesenchymal transition and temozolomide resistance of glioblastoma via AKT/GSK3-β pathway

GBM is one of the most malignant tumor in central nervous system. The resistance to temozolomide (TMZ) is inevitable in GBM and the characterization of TMZ resistance seriously hinders clinical treatment. It is worthwhile exploring the underlying mechanism of aggressive invasion and TMZ resistance in GBM treatment. Bioinformatic analysis was used to analyze the association between RND1 and a series of EMT-related genes. Colony formation assay and cell viability assay were used to assess the growth of U87 and U251 cells. The cell invasion status was evaluated based on transwell and wound-healing assays. Western blot was used to detect the protein expression in GBM cells. Treatment targeted RND1 combined with TMZ therapy was conducted in nude mice to evaluate the potential application of RND1 as a clinical target for GBM. The overexpression of RND1 suppressed the progression and migration of U87 and U251 cells. RND1 knockdown facilitated the growth and invasion of GBM cells. RND1 regulated the EMT of GBM cells via inhibiting the phosphorylation of AKT and GSK3-β. The promoted effects of RND1 on TMZ sensitivity was identified both in vitro and in vivo. This research demonstrated that the overexpression of RND1 suppressed the migration and EMT status by downregulating AKT/GSK3-β pathway in GBM. RND1 enhanced the TMZ sensitivity of GBM cells both in vitro and in vivo. Our findings may contribute to the targeted therapy for GBM and the understanding of mechanisms of TMZ resistance in GBM.

The dual HDAC and PI3K inhibitor, CUDC‑907, inhibits tumor growth and stem‑like properties by suppressing PTX3 in neuroblastoma

Neuroblastoma (NB) is one of the common solid tumors in childhood and poses a threat to the lives of children. Patients with advanced‑stage or recurrent NB have a poor prognosis. CUDC‑907, as a novel dual‑target inhibitor of histone deacetylase (HDAC) and phosphatidylinositol‑3‑kinase (PI3K), has been proven to play an antitumor role in several types of tumors. However, the exact role of CUDC‑907 in NB remains unclear. In the present study, in vivo and in vitro assays were performed to investigate the anti‑NB activity of CUDC‑907. Pentraxin 3 (PTX3) small interfering RNA (siRNA) and PTX3 overexpression plasmid were transfected into cells to define the underlying mechanisms of CUDC‑907. Tumor tissues and clinical information were collected and immunohistochemistry (IHC) was conducted to analyze the association between the expression of HDAC1, HDAC2, HDAC3 and CD44, and the prognosis of patients with NB. The results indicated that CUDC‑907 significantly inhibited the proliferation and migration, and induced the apoptosis of NB cells, downregulating the expression level of MYCN, and suppressing the PI3K/AKT and MAPK/ERK pathways. Furthermore, CUDC‑907 suppressed the stem‑like properties of NB cells by inhibiting PTX3, a ligand and upstream protein of CD44. IHC revealed that the high expression of HDAC1, 2, 3 and CD44 was associated with a poor prognosis of patients with NB. On the whole, these findings indicate that CUDC‑907 may be developed into a possible therapeutic approach for patients with NB.

Effect of gold-conjugated resveratrol nanoparticles on glioma cells and its underlying mechanism

BACKGROUND

 Glioblastoma is the most aggressive brain tumor with poor prognosis. Although Resveratrol (Rsv) is known to have therapeutic effects on glioma, the effects of gold-conjugated resveratrol nanoparticles (Rsv-AuNPs) on glioma cells are rarely reported.

OBJECTIVE

We aimed to investigate the effects of Rsv-AuNPs on glioma cells and its underlying mechanism.

METHOD

Human glioma cell line U87 was treated with different concentrations of Rsv-AuNPs. CCK-8, transwell, and wound healing assay were performed to measure the effects of Rsv-AuNPs on cell proliferation, invasion, and migration ability, respectively. Flow cytometry assay was used to detect the effects of Rsv-AuNPs on apoptosis. Changes of protein expressions related to proliferation, invasion, migration, and apoptosis were measured by Western blot assay. In addition, the inhibitory role of Rsv-AuNPs in the PI3K/AKT/mTOR signaling pathway was verified by using PI3K inhibitor LY294002.

RESULTS

Rsv-AuNPs treatment significantly suppressed proliferation, migration, and invasion of U87 cells (all P < 0.05) and increased the apoptosis rate (P < 0.05). The changes of proteins related to proliferation, migration, invasion and apoptosis were consistent (all P < 0.05). Moreover, Rsv-AuNPs treatment significantly inhibited the phosphorylation of PI3K, AKT and mTOR proteins in U87 cells (P < 0.05).

CONCLUSION

The present study found that Rsv-AuNPs inhibited the proliferation, migration, and invasion of U87 cells and induced apoptosis by inhibiting the activation of PI3K/AKT/mTOR signaling pathway. In the future, Rsv-AuNPs might be applied to the clinical treatment of glioma through more in-depth animal and clinical research.

Downregulation of Williams syndrome transcription factor (WSTF) suppresses glioblastoma cell growth and invasion by inhibiting PI3K/AKT signal pathway

Williams syndrome transcription factor (WSTF) participates in diverse cellular processes, including tumor cell proliferation and migration. However, the function of WSTF in glioblastoma (GBM) remains unknown. Data from the Gene Expression Profiling Interactive Analysis (GEPIA) and The Cancer Genome Atlas (TCGA) datasets showed that WSTF was upregulated in GBM tissues. Moreover, WSTF was also increased in the GBM cells. pcDNA-mediated over-expression of WSTF contributed to cell proliferation and invasion of GBM cells, while GBM cell proliferation and invasion were suppressed by shRNA-mediated silencing of WSTF. Additionally, GBM cell apoptosis was reduced by over-expression of WSTF accompanied by decrease in Bax and cleaved caspase-3, while promoted by silencing of WSTF with increase in Bax and cleaved caspase-3. Protein expression of AKT phosphorylation was enhanced by WSTF over-expression while reduced by WSTF silencing. Inhibitor of phosphatidylinositol 3 kinase attenuated WSTF over-expression-induced increase in GBM cell proliferation and invasion. In conclusion, WSTF contributed to GBM cell growth and invasion through activation of PI3K/AKT pathway.

Novel Dual PI3K/mTOR Inhibitor, Apitolisib (GDC-0980), Inhibits Growth and Induces Apoptosis in Human Glioblastoma Cells

Deregulated PI3K/AKT/mTOR signalling commonly exists in glioblastoma, making this axis an attractive target for therapeutic manipulation. Given that activation of PI3K/AKT/mTOR promotes tumour growth, metastasis, and resistance to anticancer therapies, mTOR inhibitors show promise in the treatment of cancer. The aim of this study was to investigate the underlying mechanism of novel dual PI3K/mTOR inhibitor, Apitolisib (GDC-0980), in A-172 and U-118-MG GBM tumour cell line suppression. It has been demonstrated that GDC-0980 induces time- and dose-dependent cytotoxicity and apoptosis in investigated glioma cell lines. In our study, the strongest induction of apoptosis was exhibited in the A-172 line after 48 h of incubation with 20 µM GDC-0980, where we observed 46.47% of apoptotic cells. In conclusion, we first discovered that dual PI3K/mTOR blockade by GDC-0980 markedly suppressed survival of human GBM cells and induced apoptosis, independent of the ER stress-mediated DR5 activation. We suggest that GDC-0980, by exerting an inhibitory effect on PERK expression, may thus block its inhibitory effect on protein synthesis, leading to intensification of translation, and this may result in an increase in apoptosis. On the other hand, CHOP stimulates protein synthesis and increases apoptosis. These findings suggest that GDC-0980 may be a candidate for further evaluation as a chemotherapeutic agent for anti-GBM therapy.

Buparlisib plus carboplatin or lomustine in patients with recurrent glioblastoma: a phase Ib/II, open-label, multicentre, randomised study

Background

Glioblastoma relapse is associated with activation of phosphatidylinositol 3-kinase (PI3K) signalling pathway. In preclinical studies, the pan-PI3K inhibitor buparlisib showed antitumour activity in glioma models.

Methods

This was a two-part, multicentre, phase Ib/II study in patients with recurrent glioblastoma pretreated with radiotherapy and temozolomide standard of care. Patients received buparlisib (80 mg or 100 mg once daily) plus carboplatin (area under the curve (AUC)=5 every 3 weeks), or buparlisib (60 mg once daily) plus lomustine (100 mg/m² every 6 weeks). The primary endpoint was to determine the maximum tolerable dose (MTD) and/or recommended phase II dose of buparlisib plus carboplatin or lomustine.

Results

Between 28 February 2014 and 7 July 2016, 35 patients were enrolled and treated with buparlisib plus carboplatin (n=17; buparlisib (80 mg) plus carboplatin, n=3; and buparlisib (100 mg) plus carboplatin, n=14), or buparlisib (60 mg) plus lomustine (n=18). The MTD of buparlisib was determined to be 100 mg per day in combination with carboplatin at an AUC of 5 every 3 weeks. The MTD of buparlisib in combination with lomustine could not be determined as it did not satisfy the MTD criteria per the Bayesian logistic regression model.

Conclusion

The overall safety profile of buparlisib remained unchanged, and no new or unexpected safety findings were reported in this study. Preliminary assessment for both combinations did not demonstrate sufficient antitumour activity compared with historical data on single-agent carboplatin or lomustine.

Trial registration number

NCT01934361.

Cell-to-cell communication mediates glioblastoma progression in Drosophila

Glioblastoma (GB) is the most aggressive and lethal tumour of the central nervous system (CNS). GB cells grow rapidly and display a network of projections, ultra-long tumour microtubes (TMs), that mediate cell to cell communication. GB-TMs infiltrate throughout the brain, enwrap neurons and facilitate the depletion of the signalling molecule wingless (Wg)/WNT from the neighbouring healthy neurons. GB cells establish a positive feedback loop including Wg signalling upregulation that activates cJun N-terminal kinase (JNK) pathway and matrix metalloproteases (MMPs) production, which in turn promote further TMs infiltration, GB progression and neurodegeneration. Thus, cellular and molecular signals other than primary mutations emerge as central players of GB. Using a Drosophila model of GB, we describe the temporal organisation of the main cellular events that occur in GB, including cell-to-cell interactions, neurodegeneration and TM expansion. We define the progressive activation of JNK pathway signalling in GB mediated by the receptor Grindelwald (Grnd) and activated by the ligand Eiger (Egr)/TNFα produced by surrounding healthy brain tissue. We propose that cellular interactions of GB with the healthy brain tissue precede TM expansion and conclude that non-autonomous signals facilitate GB progression. These results contribute to deciphering the complexity and versatility of these incurable tumours.

Prazosin inhibits the proliferation, migration and invasion, but promotes the apoptosis of U251 and U87 cells via the PI3K/AKT/mTOR signaling pathway

Prazosin, an α-adrenergic receptor antagonist, is used to treat mild to moderate hypertension. It has recently been discovered that α-adrenergic receptors may have potential antitumor properties. Therefore, in the present study, the effect of prazosin on human glioblastoma and the underlying mechanism were investigated. Human glioblastoma U251 and U87 cells were treated with different concentrations of prazosin, and a Cell Counting Kit-8 assay was performed to investigate the effects of prazosin on cell proliferation. Transwell migration and invasion assays were used to assess the effects of prazosin on cell migration and invasion. Prazosin-induced apoptosis in U251 and U87 cells was detected by flow cytometry, and the protein expression levels of anti-apoptotic proteins and proteins related to the PI3K/AKT/mTOR signaling pathway were detected by western blotting. The results suggested that following treatment with prazosin, the proliferation, migration and invasion of U251 and U81 cells were decreased. By contrast, U251 and U81 cell apoptosis, as well as the protein expression levels of Bax and active Caspase-3 were increased after prazosin treatment (P<0.05). Bcl-2 levels were also decreased after prazosin treatment (P<0.05). Additionally, the expression of phosphorylated (p)-AKT and p-mTOR, P70 and cyclin D1 were decreased in U251 and U81 cells following prazosin treatment (P<0.05). The present study suggested that prazosin may suppress glioblastoma progression by downregulating the activity of the PI3K/AKT/mTOR signaling pathway.

The limitations of targeting MEK signalling in Glioblastoma therapy

Glioblastoma (GB) is a highly aggressive, difficult to treat brain tumour. Successful treatment, consisting of maximal safe tumour de-bulking, followed by radiotherapy and treatment with the alkylating agent Temozolomide (TMZ), can extend patient survival to approximately 15 months. Combination treatments based on the inhibition of the PI3K pathway, which is the most frequently activated signalling cascade in GB, have so far only shown limited therapeutic success. Here, we use the clinically approved MEK inhibitor Trametinib to investigate its potential use in managing GB. Trametinib has a strong anti-proliferative effect on established GB cell lines, stem cell-like cells and their differentiated progeny and while it does not enhance anti-proliferative and cell death-inducing properties of the standard treatment, i.e. exposure to radiation or TMZ, neither does MEK inhibition block their effectiveness. However, upon MEK inhibition some cell populations appear to favour cell-substrate interactions in a sprouting assay and become more invasive in the Chorioallantoic Membrane assay, which assesses cell penetration into an organic membrane. While this increased invasion can be modulated by additional inhibition of the PI3K signalling cascade, there is no apparent benefit of blocking MEK compared to targeting PI3K.

FUBP1 promotes neuroblastoma proliferation via enhancing glycolysis-a new possible marker of malignancy for neuroblastoma

Background

Neuroblastoma (NB) is one of the deadliest paediatric solid tumours due to its rapid proliferative characteristics. Amplified copies of MYCN are considered the most important marker for the prediction of tumour relapse and progression in NB, but they were only detected in 20–30% of NB patients, indicating there might be other oncogenes in the development of NB. The far upstream element binding protein 1 (FUBP1) was first identified as a transcriptional regulator of the proto-oncogene MYC. However, the expression and role of FUBP1 in NB have not been documented.

Methods

FUBP1 expression was analysed from GEO database and verified by immunohistochemistry (IHC) and western blotting (WB) in NB tissues and cell lines. Cell proliferation and apoptosis were detected by Cell Counting Kit-8, Colony formation assay, EDU, TUNEL staining and flow cytometric analysis. Several glycolytic metabolites production was confirmed by ELISA and oxygen consuming rate (OCR). Luciferase assay, WB, chromatin immunoprecipitation (CHIP) were used to explore the mechanisms of the effect of FUBP1 on NB.

Results

FUBP1 mRNA levels were increased along with the increase in International Neuroblastoma Staging System (INSS) stages. High expression of FUBP1 with low N-Myc expression accounted for 44.6% of NB patient samples (n = 65). In addition, FUBP1 protein levels were remarkably increased with NB malignancy in the NB tissue microarray (NB: n = 65; ganglioneuroblastoma: n = 31; ganglioneuroma: n = 27). Furthermore, FUBP1 expression was negatively correlated with patient survival rate but positively correlated with ki67 content. In vitro experiments showed that FUBP1 promotes NB cell proliferation and inhibits cell apoptosis via enhancing glycolysis and ATP production. Mechanistically, FUBP1 inhibited the degradation of HIF1α via downregulation of Von Hippel-Lindau (VHL), the E3 ligase for HIF1α, resulting in upregulation of lactate dehydrogenase isoform B (LDHB) expression to enhance glycolysis. Overexpressed or silenced N-Myc could not regulate FUBP1 or LDHB levels.

Conclusions

Taken together, our findings demonstrate for the first time that elevated FUBP1 promotes NB glycolysis and growth by targeting HIF1α rather than N-Myc, suggesting that FUBP1 is a novel and powerful oncogene in the development of NB independent of N-Myc and may have potential in the diagnosis and treatment of NB.

Analysis of microarray data for identification of key microRNA signatures in glioblastoma multiforme

Glioblastoma multiforme (GBM) is one of the most malignant types of glioma known for its reduced survival rate and rapid relapse. Previous studies have shown that the expression patterns of different microRNAs (miRNA/miR) play a crucial role in the development and progression of GBM. In order to identify potential miRNA signatures of GBM for prognostic and therapeutic purposes, we downloaded and analyzed two expression data sets from Gene Expression Omnibus profiling miRNA patterns of GBM compared with normal brain tissues. Validated targets of the deregulated miRNAs were identified using MirTarBase, and were mapped to Search Tool for the Retrieval of Interacting Genes/Proteins, Database for Annotation, Visualization and Integrated Discovery and Kyoto Encyclopedia of Genes and Genomes databases in order to construct interaction networks and identify enriched pathways of target genes. A total of 6 miRNAs were found to be deregulated in both expression datasets studied. Pathway analysis demonstrated that most of the target genes were enriched in signaling cascades connected to cancer development, such as ‘Pathways in cancer’, ‘Focal adhesion’ and ‘PI3K-Akt signaling pathway’. Of the five target genes that were enriched in the glioblastoma pathway, in the WikiPathway database, both HRas proto-oncogene, GTPase and MET proto-oncogene, receptor tyrosine kinase target genes of hsa-miR-139-5p, were found to be significantly associated with patient survival. The present study may thus form the basis for further exploration of hsa-miR-139-5p, not only as a therapeutic agent, but also as a diagnostic biomarker for GBM as well as a predictive marker for patient survival.

Myristoylated alanine-rich C-kinase substrate effector domain phosphorylation regulates the growth and radiation sensitization of glioblastoma

Glioblastoma harbors frequent alterations in receptor tyrosine kinases, phosphatidylinositol-3 kinase (PI3K) and phosphatase and tensin homolog (PTEN) that dysregulate phospholipid signaling driven tumor proliferation and therapeutic resistance. Myristoylated alanine-rich C-kinase substrate (MARCKS) is a 32 kDa intrinsically unstructured protein containing a polybasic (+13) effector domain (ED), which regulates its electrostatic sequestration of phospholipid phosphatidylinositol (4,5)-bisphosphate (PIP2), and its binding to phosphatidylserine, calcium/calmodulin, filamentous actin, while also serving as a nuclear localization sequence. MARCKS ED is phosphorylated by protein kinase C (PKC) and Rho-associated protein kinase (ROCK) kinases; however, the impact of MARCKS on glioblastoma growth and radiation sensitivity remains undetermined. In the present study, using a tetracycline-inducible system in PTEN-null U87 cells, we demonstrate that MARCKS overexpression suppresses growth and enhances radiation sensitivity in vivo. A new image cytometer, Xcyto10, was utilized to quantify differences in MARCKS ED phosphorylation on localization and its association with filamentous actin. The overexpression of the non-phosphorylatable ED mutant exerted growth-suppressive and radiation-sensitizing effects, while the pseudo-phosphorylated ED mutant exhibited an enhanced colony formation and clonogenic survival ability. The identification of MARCKS protein-protein interactions using co-immunoprecipitation coupled with tandem mass spectrometry revealed novel MARCKS-associated proteins, including importin-β and ku70. On the whole, the findings of this study suggest that the determination of the MARCKS ED phosphorylation status is essential to understanding the impact of MARCKS on cancer progression.

Activation of WEE1 confers resistance to PI3K inhibition in glioblastoma

Background

Oncogenic activation of phosphatidylinositol-3 kinase (PI3K) signaling plays a pivotal role in the development of glioblastoma (GBM). However, pharmacological inhibition of PI3K has so far not been therapeutically successful due to adaptive resistance through a rapid rewiring of cancer cell signaling. Here we identified that WEE1 is activated after transient exposure to PI3K inhibition and confers resistance to PI3K inhibition in GBM.

Methods

Patient-derived glioma-initiating cells and established GBM cells were treated with PI3K inhibitor or WEE1 inhibitor alone or in combination, and cell proliferation was evaluated by CellTiter-Blue assay. Cell apoptosis was analyzed by TUNEL, annexin V staining, and blotting of cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase. Both subcutaneous xenograft and orthotropic xenograft studies were conducted to evaluate the effects of the combination on tumorigenesis; the tumor growth was monitored by bioluminescence imaging, and tumor tissue was analyzed by immunohistochemistry to validate signaling changes.

Results

PI3K inhibition activates WEE1 kinase, which in turn phosphorylates cell division control protein 2 homolog (Cdc2) at Tyr15 and inhibits Cdc2 activity, leading to G2/M arrest in a p53-independent manner. WEE1 inhibition abrogated the G2/M arrest and propelled cells to prematurely enter into mitosis and consequent cell death through mitotic catastrophe and apoptosis. Additionally, combination treatment significantly suppressed tumor growth in a subcutaneous model but not in an intracranial model due to limited blood-brain barrier penetration.

Conclusions

Our findings highlight WEE1 as an adaptive resistant gene activated after PI3K inhibition, and inhibition of WEE1 potentiated the effectiveness of PI3K targeted inhibition, suggesting that a combinational inhibition of WEE1 and PI3K might allow successful targeted therapy in GBM.

Inhibition of PI3K signalling increases the efficiency of radiotherapy in glioblastoma cells

Glioblastoma, the most common primary brain tumour, is also considered one of the most lethal cancers per se. It is highly refractory to therapeutic intervention, as highlighted by the mean patient survival of only 15 months, despite an aggressive treatment approach, consisting of maximal safe surgical resection, followed by radio- and chemotherapy. Radiotherapy, in particular, can have effects on the surviving fractions of tumour cells, which are considered adverse to the desired clinical outcome: It can induce increased cellular proliferation, as well as enhanced invasion. In this study, we established that differentiated glioblastoma cells alter their DNA repair response following repeated exposure to radiation and, therefore, high single-dose irradiation (SD-IR) is not a good surrogate marker for fractionated dose irradiation (FD-IR), as used in clinical practice. Integrating irradiation into a combination therapy approach, we then investigated whether the pharmacological inhibition of PI3K signalling, the most abundantly activated survival cascade in glioblastoma, enhances the efficacy of radiotherapy. Of note, treatment with GDC-0941, which blocks PI3K-mediated signalling, did not enhance cell death upon irradiation, but both treatment modalities functioned synergistically to reduce the total cell number. Furthermore, GDC-0941 not only prevented the radiation-induced increase in the motility of the differentiated cells, but further reduced their speed below that of untreated cells. Therefore, combining radiotherapy with the pharmacological inhibition of PI3K signalling is a potentially promising approach for the treatment of glioblastoma, as it can reduce the unwanted effects on the surviving fraction of tumour cells.

Inhibition of the PI3K but not the MEK/ERK pathway sensitizes human glioma cells to alkylating drugs

Background

Intrinsic chemoresistance of glioblastoma (GBM) is frequently owed to activation of the PI3K and MEK/ERK pathways. These signaling cascades are tightly interconnected however the quantitative contribution of both to intrinsic resistance is still not clear. Here, we aimed at determining the activation status of these pathways in human GBM biopsies and cells and investigating the quantitative impact of both pathways to chemoresistance.

Methods

Receptor tyrosine kinase (RTK) pathways in temozolomide (TMZ) treatment naive or TMZ resistant human GBM biopsies and GBM cells were investigated by proteome profiling and immunoblotting of a subset of proteins. Resistance to drugs and RTK pathway inhibitors was assessed by MTT assays. Apoptotic rates were determined by Annexin V staining and DNA damage with comet assays and immunoblotting.

Results

We analyzed activation of RTK pathways by proteome profiling of tumor samples of patients which were diagnosed a secondary GBM and underwent surgery and patients which underwent a second surgery after TMZ treatment due to recurrence of the tumor. We observed substantial activation of the PI3K and MEK/ERK pathways in both groups. However, AKT and CREB phosphorylation was reduced in biopsies of resistant tumors while ERK phosphorylation remained unchanged. Subsequent proteome profiling revealed that multiple RTKs and downstream targets are also activated in three GBM cell lines. We then systematically describe a mechanism of resistance of GBM cell lines and human primary GBM cells to the alkylating drugs TMZ and cisplatin. No specific inhibitor of the upstream RTKs sensitized cells to drug treatment. In contrast, we were able to restore sensitivity to TMZ and cisplatin by inhibiting PI3K in all cell lines and in human primary GBM cells. Interestingly, an opposite effect was observed when we inhibited the MEK/ERK signaling cascade with two different inhibitors.

Conclusions

Temozolomide treatment naive and TMZ resistant GBM biopsies show a distinct activation pattern of the MEK/ERK and PI3K signaling cascades indicating a role of these pathways in resistance development. Both pathways are also activated in GBM cell lines, however, only the PI3K pathway seems to play a crucial role in resistance to alkylating agents and might serve as drug target for chemosensitization.

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.

PI3K/Akt/mTOR signaling pathway and targeted therapy for glioblastoma

Glioblastoma multiform (GBM) is the most common malignant glioma of all the brain tumors and currently effective treatment options are still lacking. GBM is frequently accompanied with overexpression and/or mutation of epidermal growth factor receptor (EGFR), which subsequently leads to activation of many downstream signal pathways such as phosphatidylinositol 3-kinase (PI3K)/Akt/rapamycin-sensitive mTOR-complex (mTOR) pathway. Here we explored the reason why inhibition of the pathway may serve as a compelling therapeutic target for the disease, and provided an update data of EFGR and PI3K/Akt/mTOR inhibitors in clinical trials.

Targeting of glioblastoma cell lines and glioma stem cells by combined PIM kinase and PI3K-p110α inhibition

The PIM family of proteins encodes serine/threonine kinases with important roles in protein synthesis and cancer cell metabolism. In glioblastoma (GBM) cell lines, siRNA-mediated knockdown of PIM kinases or pharmacological inhibition of PIM kinases by SGI-1776 or AZD-1208 results in reduced phosphorylation of classic PIM effectors and also elements of the PI3K/mTOR pathway, suggesting interplay between PIM and mTOR signals in GBM cells. Combination of PIM kinase inhibitors with BYL-719, an inhibitor specific for the PI3K catalytic isoform p110α, results in enhanced antineoplastic effects in GBM cells. Additionally, pharmacologic inhibition of PIM kinases impairs growth of patient-derived glioma sphere cells, suggesting an important role for PIM kinases in cancer stem cell (CSC) function and survival. Such effects are further enhanced by concomitant inhibition of PIM kinase and p110α activities. Altogether these findings suggest that pharmacological PIM targeting in combination with PI3K inhibition may provide a unique therapeutic approach for the treatment of heterogeneous tumors containing populations of therapy-resistant CSCs in GBM.

New therapies for advanced, recurrent, and metastatic endometrial cancers

Endometrial cancer is the most common gynecologic malignancy in the United States, accounting for 6% of cancers in women. In 2017, an estimated 61,380 women were diagnosed with endometrial cancer, and approximately 11,000 died from this disease. From 1987 to 2008, there was a 50% increase in the incidence of endometrial cancer, with an approximate 300% increase in the number of associated deaths. Although there are many chemotherapeutic and targeted therapy agents approved for ovarian, fallopian tube and primary peritoneal cancers, since the 1971 approval of megestrol acetate for the palliative treatment of advanced endometrial cancer, only pembrolizumab has been Food and Drug Administration (FDA)-approved for high microsatellite instability (MSI-H) or mismatch repair deficient (dMMR) endometrial cancer; this highlights the need for new therapies to treat advanced, recurrent, metastatic endometrial cancer. In this review, we discuss current and emerging treatment options for endometrial cancer, including chemotherapy, targeted therapy, and immunotherapy. The National Cancer Institute (NCI) and others are now focusing their efforts on the design of scientifically rational targeted therapy and immunotherapy trials for specific molecular phenotypes of endometrial cancer. This is essential for the advancement of cancer care for women, which is threatened by a severe enrollment decline of approximately 80% for gynecologic oncology clinical trials.

The effects of PI3K-mediated signalling on glioblastoma cell behaviour

The PI3K/Akt/mTOR signalling network is activated in almost 90% of all glioblastoma, the most common primary brain tumour, which is almost invariably lethal within 15 months of diagnosis. Despite intensive research, modulation of this signalling cascade has so far yielded little therapeutic benefit, suggesting that the role of the PI3K network as a pro-survival factor in glioblastoma and therefore a potential target in combination therapy should be re-evaluated. Therefore, we used two distinct pharmacological inhibitors that block signalling at different points of the cascade, namely, GDC-0941 (Pictilisib), a direct inhibitor of the near apical PI3K, and Rapamycin which blocks the side arm of the network that is regulated by mTOR complex 1. While both substances, at concentrations where they inhibit their primary target, have similar effects on proliferation and sensitisation for temozolomide-induced apoptosis, GDC-0941 appears to have a stronger effect on cellular motility than Rapamycin. In vivo GDC-0941 effectively retards growth of orthotopic transplanted human tumours in murine brains and significantly prolongs mouse survival. However, when looking at genetically identical cell populations that are in alternative states of differentiation, i.e. stem cell-like cells and their differentiated progeny, a more complex picture regarding the PI3K/Akt/mTOR pathway emerges. The pathway is differently regulated in the alternative cell populations and, while it contributes to the increased chemo-resistance of stem cell-like cells compared to differentiated cells, it only contributes to the motility of the latter. Our findings are the first to suggest that within a glioblastoma tumour the PI3K network can have distinct, cell-specific functions. These have to be carefully considered when incorporating inhibition of PI3K-mediated signals into complex combination therapies.

Sphingosine 1-phosphate (S1P) signaling in glioblastoma multiforme-A systematic review

The multifunctional sphingosine-1-phosphate (S1P) is a lipid signaling molecule and central regulator in the development of several cancer types. In recent years, intriguing information has become available regarding the role of S1P in the progression of Glioblastoma multiforme (GBM), the most aggressive and common brain tumor in adults. S1P modulates numerous cellular processes in GBM, such as oncogenesis, proliferation and survival, invasion, migration, metastasis and stem cell behavior. These processes are regulated via a family of five G-protein-coupled S1P receptors (S1PR1-5) and may involve mainly unknown intracellular targets. Distinct expression patterns and multiple intracellular signaling pathways of each S1PR subtype enable S1P to exert its pleiotropic cellular actions. Several studies have demonstrated alterations in S1P levels, the involvement of S1PRs and S1P metabolizing enzymes in GBM pathophysiology. While the tumorigenic actions of S1P involve the activation of several kinases and transcription factors, the specific G-protein (Gi, Gq, and G12/13)-coupled signaling pathways and downstream mediated effects in GBM remain to be elucidated in detail. This review summarizes the recent findings concerning the role of S1P and its receptors in GBM. We further highlight the current insights into the signaling pathways considered fundamental for regulating the cellular processes in GMB and ultimately patient prognosis.

Extracellular Hyaluronic Acid Influences the Efficacy of EGFR Tyrosine Kinase Inhibitors in a Biomaterial Model of Glioblastoma

3D biomaterial models have potential to explore the influence of the tumor microenvironment on aberrant signaling pathways and compensatory signals using patient-derived cells. Glioblastoma (GBM) tumors are highly heterogeneous, with both cell composition and extracellular matrix biophysical factors seen as key regulators of malignant phenotype and treatment outcomes. Amplification, overexpression, and mutation of the epidermal growth factor receptor (EGFR) tyrosine kinase have been identified in 50% of GBM patients. Here, hyaluronic acid (HA) decorated methacrylamide-functionalized gelatin (GelMA) hydrogels are used to examine the synergies between microenvironmental factors and a model EGFR tyrosine kinase inhibitor (TKI) using patient-derived xenograft cells. The in vitro behavior of 3 patient-derived xenografts that reflect a clinically relevant range of EGFR variants is characterized: GBM10 (EGFR, wild type), GBM12 (EGFR+), and GBM6 (EGFRvIII). GelMA hydrogels support xenograft culture; cells remain viable, active, respond to matrix-immobilized HA, and upregulate genes associated with matrix remodeling and tumor growth. Interestingly, matrix-immobilized HA alters the response of GBM cells to a model tyrosine kinase inhibitor, erlotinib. While constitutively activated EGFRvIII cells are sensitive to TKI in gelatin hydrogels, hyaluronic acid mediated adhesive signaling interacts with EGFRvIII signaling to increase cell metabolic activity, increase soluble hyaluronic acid synthesis, and modify response to erlotinib exposure.

The preliminary radiogenomics association between MR perfusion imaging parameters and genomic biomarkers, and their predictive performance of overall survival in patients with glioblastoma

The radiogenomics association of neovascularization is important for overall survival (OS) in glioblastoma patients and remains unclear. The purpose of this study is to assess the association between MR perfusion imaging derived parameters and genomic biomarkers of glioblastoma, and to evaluate their prognostic value. This retrospective study enrolled 41 patients with newly diagnosed glioblastoma. The mean and maximal relative cerebral blood volume (rCBV) ratio (rCBV_mean and rCBV_max), derived from MR perfusion weighted imaging, of the enhancing tumor, as well as maximal rCBV ratio of peri-enhancing tumor area (rCBV_peri-tumor) were measured. The ki-67 labeling index, mammalian target of rapamycin (mTOR) activation, epidermal growth factor receptor (EGFR) amplification, isocitrate dehydrogenase (IDH) mutation and TP53 were assessed. There was a significant correlation between rCBV_max and mTOR based on Pearson's correlations with Benjamini-Hochberg adjustment for controlling false discovery rate, p = 0.047. The rCBV_peri-tumor showed significant correlation with mTOR (p = 0.0183) after adjustment of gender and EGFR status. The mean rCBV_peri-tumor value of the patients with OS shorter than 14 months was significantly higher than patients with OS longer than 14 months, p = 0.002. The rCBV_peri-tumor and age were the two strongest predictors of OS (hazard ratio = 1.29 and 1.063 respectively) by Cox regression analysis. This study showed that hemodynamic abnormalities of glioblastoma were associated with genomics activation status of mTOR-EGFR pathway, however, the radiogenomics associations are different in enhancing and peri-enhancing area of glioblastoma. The rCBV_peri-tumor has better prognostic value than genomic biomarkers alone.

Mammalian target of rapamycin inhibitors, temsirolimus and torin 1, attenuate stemness-associated properties and expression of mesenchymal markers promoted by phorbol-myristate-acetate and oncostatin-M in glioblastoma cells

The phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin signaling pathway is crucial for tumor survival, proliferation, and progression, making it an attractive target for therapeutic intervention. In glioblastoma, activated mammalian target of rapamycin promotes invasive phenotype and correlates with poor patient survival. A wide range of mammalian target of rapamycin inhibitors are currently being evaluated for cytotoxicity and anti-proliferative activity in various tumor types but are not explored sufficiently for controlling tumor invasion and recurrence. We recently reported that mammalian target of rapamycin inhibitors-rapamycin, temsirolimus, torin 1, and PP242-suppressed invasion and migration promoted by tumor necrosis factor-alpha and phorbol-myristate-acetate in glioblastoma cells. As aggressive invasion and migration of tumors are associated with mesenchymal and stem-like cell properties, this study aimed to examine the effect of mammalian target of rapamycin inhibitors on these features in glioblastoma cells. We demonstrate that temsirolimus and torin 1 effectively reduced the constitutive as well as phorbol-myristate-acetate/oncostatin-M-induced expression of mesenchymal markers (fibronectin, vimentin, and YKL40) and neural stem cell markers (Sox2, Oct4, nestin, and mushashi1). The inhibitors significantly abrogated the neurosphere-forming capacity induced by phorbol-myristate-acetate and oncostatin-M. Furthermore, we demonstrate that the drugs dephosphorylated signal transducer and activator transcription factor 3, a major regulator of mesenchymal and neural stem cell markers implicating the role of signal transducer and activator transcription factor 3 in the inhibitory action of these drugs. The findings demonstrate the potential of mammalian target of rapamycin inhibitors as "stemness-inhibiting drugs" and a promising therapeutic approach to target glioma stem cells.

Cancer stem cells: The potential role of autophagy, proteolysis, and cathepsins in glioblastoma stem cells

One major obstacle in cancer therapy is chemoresistance leading to tumor recurrence and metastasis. Cancer stem cells, in particular glioblastoma stem cells, are highly resistant to chemotherapy, radiation, and immune recognition. In case of immune recognition, several survival mechanisms including, regulation of autophagy, proteases, and cell surface major histocompatibility complex class I molecules, are found in glioblastoma stem cells. In different pathways, cathepsins play a crucial role in processing functional proteins that are necessary for several processes and proper cell function. Consequently, strategies targeting these pathways in glioblastoma stem cells are promising approaches to interfere with tumor cell survival and will be discussed in this review.

Silencing of epidermal growth factor, latrophilin and seven transmembrane domain-containing protein 1 (ELTD1) via siRNA-induced cell death in glioblastoma

The failure of therapies targeting tumor angiogenesis may be caused by anti-angiogenic resistance mechanisms induced by VEGF and non-VEGF pathways alterations. Anti-angiogenic therapy failure is also attributed to immune system, acting by tumor-associated macrophages that release pro-angiogenic factors and a consequent increase of blood vessels. Recently, in a study by Rheal et al., a new angiogenic receptor, epidermal growth factor, latrophilin, and 7 trans-membrane domain-containing protein 1 on chromosome 1(ELTD1) has been identified as a promising glioma biomarker. In this study we aim to analyse whether this receptor may be used as a target molecule in glioblastoma therapy. Our results showed that small interfering RNA silencing ELTD1 caused cytotoxicity in glioblastoma cells. We also found that PDGFR, VEGFR, and their common PI3K/mTOR intracellular pathway inactivation-induced cytotoxicity in glioblastoma cells. Further, we found high percent of cytotoxicity in a low passage glioblastoma cell line after BEZ235 (a dual inhibitor of PI3K/mTOR pathway) treatment at nanomolar concentrations, compared to AG1433 (a PDGFR inhibitor) and SU1498 (a VEGFR inhibitor) that were only cytotoxic at micromolar ranges. In the future, these could prove as attractive therapeutic targets in single therapy or coupled with classic therapeutic approaches such as chemotherapy of radiotherapy.

Anti-Proliferative Activity of λ-Carrageenan Through the Induction of Apoptosis in Human Breast Cancer Cells

Background

Sulfated Polysaccharides (SPs) possess spectrum of pharmacological and therapeutic properties that could attributed to their origins variation, chemical structures and biological activities. Various studies have shown the impact of SPs on proliferation in different cancer cell lines.

Objectives

In this study, we have evaluated the biological effects of λ-carrageenan, a highly SP, extracted from the red seaweed Laurencia papillosa, on MDA-MB-231 cancer cell line.

Materials and Methods

MDA-MB-231 cells have treated with λ-carrageenan, the viability and apoptosis have assessed by the appropriate florescent probes on flow cytometer. The expression levels of mRNA of apoptotic genes have detected by real-time PCR analysis.

Results

Our results have indicated that the signaling pathway of λ-carrageenan inhibited the proliferation of MDA-MB-231 cells by up-regulating the pro-apoptotic genes caspase-8, caspase-9, caspase-3 which have been resulting the increased levels of active caspase-3 protein. Furthermore, This SP had that capacity to disrupt the mitochondrial function by altering the bax/bcl-2 ratio of expression which has considered an important element in apoptosis induction.

Conclusions

The presented results have signposted that λ-carrageenan was a promising bioactive polymer which could be a potential candidate in preventing or treating breast cancer.

Targeted inhibition of dominant PI3-kinase catalytic isoforms increase expression of stem cell genes in glioblastoma cancer stem cell models

Cancer stem cells (CSC) exhibit therapy resistance and drive self-renewal of the tumour, making cancer stem cells an important target for therapy. The PI3K signalling pathway has been the focus of considerable research effort, including in glioblastoma (GBM), a cancer that is notoriously resistant to conventional therapy. Different isoforms of the catalytic sub-unit have been associated with proliferation, migration and differentiation in stem cells and cancer stem cells. Blocking these processes in CSC would improve patient outcome. We examined the effect of isoform specific PI3K inhibitors in two models of GBM CSC, an established GBM stem cell line 08/04 and a neurosphere formation model. We identified the dominant catalytic PI3K isoform for each model, and inhibition of the dominant isoform blocked AKT phosphorylation, as did pan-PI3K/mTOR inhibition. Analysis of SOX2, OCT4 and MSI1 expression revealed that inhibition of the dominant p110 subunit increased expression of cancer stem cell genes, while pan-PI3K/mTOR inhibition caused a similar, though not identical, increase in cancer stem cell gene expression. This suggested that PI3K inhibition enhanced, rather than blocked, CSC activity. Careful analysis of the response to specific isoform inhibition will be necessary before specific subunit inhibitors can be successfully deployed against GBM CSC.

The Role of Glucose Modulation and Dietary Supplementation in Patients With Central Nervous System Tumors

OPINION STATEMENT

Central nervous system gliomas are the most common primary brain tumor, and these are most often high-grade gliomas. Standard therapy includes a combination of surgery, radiation, and chemotherapy which provides a modest increase in survival, but virtually, no patients are cured, the overall prognosis remains poor, and new therapies are desperately needed. Tumor metabolism is a well-recognized but understudied therapeutic approach to treating cancers. Dietary and nondietary modulation of glucose homeostasis and the incorporation of dietary supplements and other natural substances are potentially important interventions to affect cancer cell growth, palliate symptoms, reduce treatment-associated side effects, and improve the quality and quantity of life in patients with cancer. These approaches are highly desired by patients. However, they can be financially burdensome, associated with toxicities, and have, on occasion, reduced the efficacy of proven therapies and negatively impacted patient outcomes. The lack of rigorous scientific data evaluating almost all diet and supplement-based therapies currently limits their incorporation into standard oncologic practice. Rigorous studies are needed to document and improve these potentially useful approaches in patients with brain and other malignancies.

Novel Approaches to Apoptosis-Inducing Therapies

Induction of apoptotic programmed cell death is one of the underlying principles of most current cancer therapies. In this review, we discuss the limitations and drawbacks of this approach and identify three distinct, but overlapping strategies to avoid these difficulties and further enhance the efficacy of apoptosis-inducing therapies. We postulate that the application of multi-targeted small molecule inhibitor cocktails will reduce the risk of the cancer cell populations developing resistance towards therapy. Following from these considerations regarding population genetics and ecology, we advocate the reconsideration of therapeutic end points to maximise the benefits, in terms of quantity and quality of life, for the patients. Finally, combining both previous points, we also suggest an altered focus on the cellular and molecular targets of therapy, i.e. targeting the (cancer cells') interaction with the tumour microenvironment.

SHIP2 controls plasma membrane PI(4,5)P2 thereby participating in the control of cell migration in 1321 N1 glioblastoma

Phosphoinositides, particularly PI(3,4,5)P3, and PI(4,5)P2, are recognized by SHIP2 a member of the inositol polyphosphate 5-phosphatase family. SHIP2 dephosphorylates PI(3,4,5)P3 to form PI(3,4)P2; the latter interacts with specific target proteins (e.g. lamellipodin). Although the SHIP2 preferred substrate is PI(3,4,5)P3, PI(4,5)P2 could also be dephosphorylated to PI4P. Through depletion of SHIP2 in a glioblastoma cell line 1321 N1 cells, we show that SHIP2 inhibits cell migration. In different glioblastoma cell lines and primary cultures, SHIP2 staining at the plasma membrane partly overlaps with PI(4,5)P2 immunoreactivity. PI(4,5)P2 was upregulated in SHIP2-deficient N1 cells as compared to control cells; in contrast, PI4P was very much decreased in SHIP2-deficient cells. Therefore, SHIP2 controls both PI(3,4,5)P3 and PI(4,5)P2 levels in intact cells. In N1 cells, the PI(4,5)P2 binding protein myosin-1c was identified as a new interactor of SHIP2. Regulation of PI(4,5)P2 and PI4P content by SHIP2 controls N1 cell migration through the organization of focal adhesions. Thus, our results reveal a novel role of SHIP2 in the control of PI(4,5)P2, PI4P and cell migration in PTEN-deficient glioblastoma N1 cells.

Effect of VEGFR, PDGFR and PI3K/mTOR Targeting in Glioblastoma

Resistance to targeted therapy is a well known obstacle in cancer therapy. The cross-talk between several growth factor receptors generates redundancy in their intracellular pathways that usually mediates resistance to receptor targeted therapy. Simultaneous inactivation of two or more growth factor receptors has been suggested to prevent the cross-talk between their signaling pathways and to better eliminate malignant cells. Here we found that targeted therapy against these receptors induced moderate cell death in glioblastoma cells. More important, dual PDGFR and VEGFR inactivation induced more pronounceable cell death compared to inactivation of each receptor alone but failed to induce synergistic cell death in glioblastoma. PI3K/mTOR dual targeting has been identified as an efficient therapeutic approach in several malignant diseases, including glioblastoma. Therefore, we also investigated the PI3K/mTOR pathways inhibition effect in glioblastoma cells. Our results showed that inactivation of PI3K/mTOR pathways were more efficient than PDGFR or VEGFR single targeting or their dual inhibition.

A Potential Role for the Inhibition of PI3K Signaling in Glioblastoma Therapy

Glioblastoma multiforme (GBM) is the most common primary brain tumor and among the most difficult to treat malignancies per se. In almost 90% of all GBM alterations in the PI3K/Akt/mTOR have been found, making this survival cascade a promising therapeutic target, particular for combination therapy that combines an apoptosis sensitizer, such as a pharmacological inhibitor of PI3K, with an apoptosis inducer, such as radio- or chemotherapy. However, while in vitro data focusing mainly on established cell lines has appeared rather promising, this has not translated well to a clinical setting. In this study, we analyze the effects of the dual kinase inhibitor PI-103, which blocks PI3K and mTOR activity, on three matched pairs of GBM stem cells/differentiated cells. While blocking PI3K-mediated signaling has a profound effect on cellular proliferation, in contrast to data presented on two GBM cell lines (A172 and U87) PI-103 actually counteracts the effect of chemotherapy. While we found no indications for a potential role of the PI3K signaling cascade in differentiation, we saw a clear and strong contribution to cellular motility and, by extension, invasion. While blocking PI3K-mediated signaling concurrently with application of chemotherapy does not appear to be a valid treatment option, pharmacological inhibitors, such as PI-103, nevertheless have an important place in future therapeutic approaches.

Glycemic modulation in neuro-oncology: experience and future directions using a modified Atkins diet for high-grade brain tumors

Dietary glycemic modulation through high-fat, low-carbohydrate diets, which induce a state of systemic ketosis and alter systemic metabolic signaling, have been incorporated into the clinical management of patients with neurological disease for more than a century. Mounting preclinical evidence supports the antitumor, proapoptotic, and antiangiogenic effects of disrupting glycolytic metabolism through dietary intervention. In recent years, interest in incorporating such novel therapeutic strategies in neuro-oncology has increased. To date, 3 published studies incorporating novel dietary therapies in oncology have been reported, including one phase I study in neuro-oncology, and have set the stage for further study in this field. In this article, we review the biochemical pathways, preclinical data, and early clinical translation of dietary interventions that modulate systemic glycolytic metabolism in the management of primary malignant brain tumors. We introduce the modified Atkins diet (MAD), a novel dietary alternative to the classic ketogenic diet, and discuss the critical issues facing future study.