Inhibition of Akt survival pathway by a small-molecule inhibitor in human glioblastoma

Nano-sensitizer with self-amplified drug release and hypoxia normalization properties potentiates efficient chemoradiotherapy of pancreatic cancer

The hypoxic nature of pancreatic cancer, one of the most lethal malignancies worldwide, significantly impedes the effectiveness of chemoradiotherapy. Although the development of oxygen carriers and hypoxic sensitizers has shown promise in overcoming tumor hypoxia. The heterogeneity of hypoxia-primarily caused by limited oxygen penetration-has posed challenges. In this study, we designed a hypoxia-responsive nano-sensitizer by co-loading tirapazamine (TPZ), KP372-1, and MK-2206 in a metronidazole-modified polymeric vesicle. This nano-sensitizer relies on efficient endogenous NAD(P)H quinone oxidoreductase 1-mediated redox cycling induced by KP372-1, continuously consuming periphery oxygen and achieving evenly distributed hypoxia. Consequently, the normalized tumor microenvironment facilitates the self-amplified release and activation of TPZ without requiring deep penetration. The activated TPZ and metronidazole further sensitize radiotherapy, significantly reducing the radiation dose needed for extensive cell damage. Additionally, the coloaded MK-2206 complements inhibition of therapeutic resistance caused by Akt activation, synergistically enhancing the hypoxic chemoradiotherapy. This successful hypoxia normalization strategy not only overcomes hypoxia resistance in pancreatic cancer but also provides a potential universal approach to sensitize hypoxic tumor chemoradiotherapy by reshaping the hypoxic distribution.

Recurrent Glioblastoma-Molecular Underpinnings and Evolving Treatment Paradigms

Glioblastoma is the most common and lethal central nervous system malignancy with a median survival after progression of only 6-9 months. Major biochemical mechanisms implicated in glioblastoma recurrence include aberrant molecular pathways, a recurrence-inducing tumor microenvironment, and epigenetic modifications. Contemporary standard-of-care (surgery, radiation, chemotherapy, and tumor treating fields) helps to control the primary tumor but rarely prevents relapse. Cytoreductive treatment such as surgery has shown benefits in recurrent glioblastoma; however, its use remains controversial. Several innovative treatments are emerging for recurrent glioblastoma, including checkpoint inhibitors, chimeric antigen receptor T cell therapy, oncolytic virotherapy, nanoparticle delivery, laser interstitial thermal therapy, and photodynamic therapy. This review seeks to provide readers with an overview of (1) recent discoveries in the molecular basis of recurrence; (2) the role of surgery in treating recurrence; and (3) novel treatment paradigms emerging for recurrent glioblastoma.

Challenges and advances for glioma therapy based on inorganic nanoparticles

Glioma is one of the most serious central nervous system diseases, with high mortality and poor prognosis. Despite the continuous development of existing treatment methods, the median survival time of glioma patients is still only 15 months. The main treatment difficulties are the invasive growth of glioma and the obstruction of the blood-brain barrier (BBB) to drugs. With rapid advancements in nanotechnology, inorganic nanoparticles (INPs) have shown favourable application prospects in the diagnosis and treatment of glioma. Due to their extraordinary intrinsic features, INPs can be easily fabricated, while doping with other elements and surface modification by biological ligands can be used to enhance BBB penetration, targeted delivery and biocompatibility. Guided glioma theranostics with INPs can improve and enhance the efficacy of traditional methods such as chemotherapy, radiotherapy and gene therapy. New strategies, such as immunotherapy, photothermal and photodynamic therapy, magnetic hyperthermia therapy, and multifunctional inorganic nanoplatforms, have also been facilitated by INPs. This review emphasizes the current state of research and clinical applications of INPs, including glioma targeting and BBB penetration enhancement methods, in vivo and in vitro biocompatibility, and diagnostic and treatment strategies. As such, it provides insights for the development of novel glioma treatment strategies.

Characterization and comparison of human glioblastoma models

Glioblastoma (GBM) is one of the deadliest cancers. Treatment options are limited, and median patient survival is only several months. Translation of new therapies is hindered by a lack of GBM models that fully recapitulate disease heterogeneity. Here, we characterize two human GBM models (U87-luc2, U251-RedFLuc). In vitro, both cell lines express similar levels of luciferase and show comparable sensitivity to temozolomide and lapatinib exposure. In vivo, however, the two GBM models recapitulate different aspects of the disease. U87-luc2 cells quickly grow into large, well-demarcated tumors; U251-RedFLuc cells form small, highly invasive tumors. Using a new method to assess GBM invasiveness based on detecting tumor-specific anti-luciferase staining in brain slices, we found that U251-RedFLuc cells are more invasive than U87-luc2 cells. Lastly, we determined expression levels of ABC transporters in both models. Our findings indicate that U87-luc2 and U251-RedFLuc GBM models recapitulate different aspects of GBM heterogeneity that need to be considered in preclinical research.

Wnt and PI3K/Akt/mTOR Survival Pathways as Therapeutic Targets in Glioblastoma

Glioblastoma (GBM) is a devastating type of brain tumor, and current therapeutic treatments, including surgery, chemotherapy, and radiation, are palliative at best. The design of effective and targeted chemotherapeutic strategies for the treatment of GBM require a thorough analysis of specific signaling pathways to identify those serving as drivers of GBM progression and invasion. The Wnt/β-catenin and PI3K/Akt/mTOR (PAM) signaling pathways are key regulators of important biological functions that include cell proliferation, epithelial–mesenchymal transition (EMT), metabolism, and angiogenesis. Targeting specific regulatory components of the Wnt/β-catenin and PAM pathways has the potential to disrupt critical brain tumor cell functions to achieve critical advancements in alternative GBM treatment strategies to enhance the survival rate of GBM patients. In this review, we emphasize the importance of the Wnt/β-catenin and PAM pathways for GBM invasion into brain tissue and explore their potential as therapeutic targets.

Cediranib, a pan-inhibitor of vascular endothelial growth factor receptors, inhibits proliferation and enhances therapeutic sensitivity in glioblastoma cells

AIMS

Glioblastoma (GB) is the most aggressive type of brain tumor. Rapid progression, active angiogenesis, and therapy resistance are major reasons for its high mortality. Elevated expression of members of the vascular endothelial growth factor (VEGF) family suggests that anti-VEGF therapies may be potent anti-glioma therapeutic approaches. Here, we evaluated the anti-tumor activity of cediranib, a pan inhibitor of the VEGF receptors, on GB cells.

MATERIALS AND METHODS

Anti-proliferative effects of cediranib were determined using MTT, crystal-violet staining, clonogenic and anoikis resistance assays. Apoptosis induction was assessed by Annexin V/PI staining and Western blot analysis and aggressive abilities of GB cells were investigated using cell migration/invasion assays and zymography. Small-interfering RNA (siRNA)-mediated Knockdown was used to study resistance mechanisms. The anti-proliferative and apoptotic effects of cediranib in combination with radiotherapy, temozolomide, bevacizumab were also evaluated using MTT, Annexin V/PI staining and Western blot analysis for cleaved PARP-1.

KEY FINDINGS

Cediranib reduced GB cell proliferation, induced apoptotic cell death and inhibited the aggressive abilities of GB cells. Cediranib synergistically increased the anti-proliferative and apoptotic effects of radiotherapy and bevacizumab and augmented the sensitivity of GB cells to temozolomide chemotherapy. In addition, knockdown of MET and AKT potentiated cediranib sensitivity in cediranib-resistant GB cells.

SIGNIFICANCE

These findings suggest that cediranib, alone or in combination with other therapeutics, is a promising strategy for the treatment of GB and provide a rationale for further investigation of the therapeutic potential of cediranib for the treatment of this fatal malignancy.

SOCS3 is Related to Cell Proliferation in Neuronal Tissue: An Integrated Analysis of Bioinformatics and Experiments

Glioma is the most common primary malignant tumor that occurs in the central nervous system. Gliomas are subdivided according to a combination of microscopic morphological, molecular, and genetic factors. Glioblastoma (GBM) is the most aggressive malignant tumor; however, efficient therapies or specific target molecules for GBM have not been developed. We accessed RNA-seq and clinical data from The Cancer Genome Atlas, the Chinese Glioma Genome Atlas, and the GSE16011 dataset, and identified differentially expressed genes (DEGs) that were common to both GBM and lower-grade glioma (LGG) in three independent cohorts. The biological functions of common DEGs were examined using NetworkAnalyst. To evaluate the prognostic performance of common DEGs, we performed Kaplan-Meier and Cox regression analyses. We investigated the function of SOCS3 in the central nervous system using three GBM cell lines as well as zebrafish embryos. There were 168 upregulated genes and 50 downregulated genes that were commom to both GBM and LGG. Through survival analyses, we found that SOCS3 was the only prognostic gene in all cohorts. Inhibition of SOCS3 using siRNA decreased the proliferation of GBM cell lines. We also found that the zebrafish ortholog, socs3b, was associated with brain development through the regulation of cell proliferation in neuronal tissue. While additional mechanistic studies are necessary, our results suggest that SOCS3 is an important biomarker for glioma and that SOCS3 is related to the proliferation of neuronal tissue.

Expression of activator proteins of SHH/GLI and PI3K/Akt/mTORC1 signaling pathways in human gliomas is associated with high grade tumors

Recent findings have demonstrated a synergic crosstalk between SHH/GLI and PI3K/Akt/mTORC1 signaling in glioblastoma progression cells in vitro and in tumors in mice, but it is not known if this also occurs in human gliomas. We then aimed to investigate the expression of key proteins of these pathways in different human gliomas. The expression of PTEN, phospho-Akt (Ser473), phospho-S6K1 (Thr389), SHH, GLI1, GLI2 and GLI3 was assessed by immunohistochemistry in gliomas and in control brain tissues. The pattern of expression of each protein was established according to glioma type, glioma grade and to cell type; the relative expression of each protein was used to perform statistical analyses. We found that the expression of proteins of both signaling pathways differs between normal brain and glioma tissues. For instance, normal astrocytes had a different protein expression pattern compared with reactive and tumoral astrocytes. Interestingly, we detected a recurrent pattern of expression of GLI3 in oligodendrocytes and of phospho-S6K1 in mitotic neoplastic cells. We also identified differences of cell signaling according to glioma type: oligodendrogliomas and ependymomas are related with the expression of SHH/GLI proteins. Finally, we detected that high grade gliomas statistically correlate with the expression of GLI1 and GLI2, and that GLI1, GLI2, phospho-Akt and phospho-S6K1 are more expressed in patients with less survival, suggesting that activation of these cell signaling influences glioma outcome and patient survival. In summary, our results show that proteins of PI3K/Akt/mTORC1 and SHH/GLI pathways are differentially expressed in human gliomas according to tumor type and grade, and suggest that the activation of these signaling networks is associated with glioma progression.

PAM (PIK3/AKT/mTOR) signaling in glia: potential contributions to brain tumors in aging

Despite a growing proportion of aged individuals at risk for developing cancer in the brain, the prognosis for these conditions remains abnormally poor due to limited knowledge of underlying mechanisms and minimal treatment options. While cancer metabolism in other organs is commonly associated with upregulated glycolysis (i.e. Warburg effect) and hyperactivation of PIK3/AKT/mTOR (PAM) pathways, the unique bioenergetic demands of the central nervous system may interact with these oncogenic processes to promote tumor progression in aging. Specifically, constitutive glycolysis and PIK3/AKT/mTOR signaling in glia may be dysregulated by age-dependent alterations in neurometabolic demands, ultimately contributing to pathological processes otherwise associated with PIK3/AKT/mTOR induction (e.g. cell cycle entry, impaired autophagy, dysregulated inflammation). Although several limitations to this theoretical model exist, the consideration of aberrant PIK3/AKT/mTOR signaling in glia during aging elucidates several therapeutic opportunities for brain tumors, including non-pharmacological interventions.

DNA damage induced by KP372-1 hyperactivates PARP1 and enhances lethality of pancreatic cancer cells with PARP inhibition

The overall prognosis for pancreatic cancer remains dismal and potent chemotherapeutic agents that selectively target this cancer are critically needed. Elevated expression of NAD(P)H:quinone oxidoreductase 1 (NQO1) is frequent in pancreatic cancer, and it offers promising tumor-selective targeting. Recently, KP372-1 was identified as a novel NQO1 redox cycling agent that induces cytotoxicity in cancer cells by creating redox imbalance; however, the mechanistic basis of KP372-1-induced cytotoxicity remains elusive. Here, we show that KP372-1 sensitizes NQO1-expressing pancreatic cancer cells and spares immortalized normal pancreatic duct cells, hTERT-HPNE. Notably, we found that KP372-1 is ~ 10- to 20-fold more potent than β-lapachone, another NQO1 substrate, against pancreatic cancer cells. Mechanistically, our data strongly suggest that reactive oxygen species produced by NQO1-dependent redox cycling of KP372-1 cause robust DNA damage, including DNA breaks. Furthermore, we found that KP372-1-induced DNA damage hyperactivates the central DNA damage sensor protein poly(ADP-ribose) polymerase 1 (PARP1) and activates caspase-3 to initiate cell death. Our data also show that the combination of KP372-1 with PARP inhibition creates enhanced cytotoxicity in pancreatic cancer cells. Collectively, our study provides mechanistic insights into the cytotoxicity instigated by KP372-1 and lays an essential foundation to establish it as a promising chemotherapeutic agent against cancer.

MiR-1271 regulates glioblastoma cell proliferation and invasion by directly targeting the CAMKK2 gene

This study explored the regulatory role of microRNA-1271 (miR-1271) in glioblastoma multiforme (GBM) proliferation and invasion via calcium/calmodulin-dependent protein kinase 2 (CaMKK2). MiR-1271 and CaMKK2 expression were quantified in normal human astrocyte cells, GBM cell lines, and low- and high-grade glioma tissues. MKI67 expression in GBM cells was measured using quantitative real-time polymerase chain reaction. The target relationship between miR-1271 and the CAMKK2 gene was confirmed using the luciferase reporter assay. MTT and Transwell assays were used to analyze the role of miR-1271 and CAMKK2 in cell proliferation and invasion. Finally, CaMKK2 expression and AKT phosphorylation were detected by western blotting. MiR-1271 was significantly downregulated in high-grade glioma tissues and GBM cell lines. Conversely, CAMKK2 mRNA expression was upregulated in high-grade glioma tissues and GBM cell lines. We observed that miR-1271 directly targeted the 3'-untranslated region of CAMKK2, indicating an inverse relationship with miR-1271. Overexpressing miR-1271 inhibited GBM cell proliferation and invasion, whereas inhibiting miR-1271 increased cell proliferation and invasion. Silencing CAMKK2 expression also inhibited GBM cell proliferation and invasion. Furthermore, overexpressing miR-1271 inhibited AKT phosphorylation and MKI67 mRNA expression by targeting CAMKK2. These results indicate that miR-1271 regulates GBM cell proliferation and invasion, and that these effects involve directly targeting the CAMKK2 gene. Therefore, miR-1271 may serve as a new therapeutic target for developing GBM treatments.

Involvement of Phosphatase and Tensin Homolog in Cyclin-Dependent Kinase 4/6 Inhibitor-Induced Blockade of Glioblastoma

Dysregulation of retinoblastoma (Rb) signaling pathway have been established as a requirement for glioblastoma (GBM) initiation and progression, which suggests that blockade of CDK4/6-Rb signaling axis for GBM treatment. Palbociclib, a selective inhibitor of the cyclin-dependent kinases CDK4/6, has been applied for breast cancer treatment. However, its efficacy against glioblastoma has not been well clarified. Here, effects of CDK4/6 inhibitors on various kinds of GBM cell lines are investigated and the functional mechanisms are identified. Data showed that cells with diverse PTEN status respond to palbociclib differently. Gain-of-function and loss-of-function studies indicated that PTEN enhanced the sensitivity of GBM cells to palbociclib in vitro and in vivo, which was associated with suppressions of Akt and ERK signaling and independent of Rb signaling inhibition. Hence, our findings support that palbociclib selectively

Correlated MRI and Ultramicroscopy (MR-UM) of Brain Tumors Reveals Vast Heterogeneity of Tumor Infiltration and Neoangiogenesis in Preclinical Models and Human Disease

Diffuse tumor infiltration into the adjacent parenchyma is an effective dissemination mechanism of brain tumors. We have previously developed correlated high field magnetic resonance imaging and ultramicroscopy (MR-UM) to study neonangiogenesis in a glioma model. In the present study we used MR-UM to investigate tumor infiltration and neoangiogenesis in a translational approach. We compare infiltration and neoangiogenesis patterns in four brain tumor models and the human disease: whereas the U87MG glioma model resembles brain metastases with an encapsulated growth and extensive neoangiogenesis, S24 experimental gliomas mimic IDH1 wildtype glioblastomas, exhibiting infiltration into the adjacent parenchyma and along white matter tracts to the contralateral hemisphere. MR-UM resolves tumor infiltration and neoangiogenesis longitudinally based on the expression of fluorescent proteins, intravital dyes or endogenous contrasts. Our study demonstrates the huge morphological diversity of brain tumor models regarding their infiltrative and neoangiogenic capacities and further establishes MR-UM as a platform for translational neuroimaging.

Ultra-small but ultra-effective: Folic acid-targeted gold nanoclusters for enhancement of intracranial glioma tumors' radiation therapy efficacy

The aim of the present study is to investigate folic acid and BSA decorated gold nanoclusters (FA-AuNCs) effect on the enhancement of intracranial C6 glioma tumors radiation therapy (RT) efficacy. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements exhibited about 2.5 times more FA-AuNCs uptake by C6 cancer cells (32.8 ng/10⁶ cells) than the normal cells. FA-AuNCs had significantly higher concentration in the brain tumors (8.1 μg/mg) in comparison with surrounding normal brain tissue (4.3 μg/mg). Moreover, FA-AuNCs exhibited dose enhancement factor (DEF) of 1.6. The glioma-bearing rats' survival times were almost doubled at radiation therapy + FA-AuNCs (25.0 ± 1.5 days) in comparison with no-treatment group (12.8 ± 0.7 days). The Ki-67 labeling index was 48.89% ± 9.93 for control, 29.98% ± 8.32 for RT, and 11.53% ± 7.65 for RT + FA-AuNCs. Therefore, FA-AuNCs can be effective radiosensitizers for intracranial glioma tumors RT.

PDGFA/PDGFRα-regulated GOLM1 promotes human glioma progression through activation of AKT

BACKGROUND

Golgi Membrane Protein 1 (GOLM1), a protein involved in the trafficking of proteins through the Golgi apparatus, has been shown to be oncogenic in a variety of human cancers. Here, we examined the role of GOLM1 in the development of human glioma.

METHODS

qRT-PCR, immunohistochemistry, and western blot analysis were performed to evaluate GOLM1 levels in cell lines and a cohort of primary human glioma and non-neoplastic brain tissue samples. Glioma cell lines were modified with lentiviral constructs expressing short hairpin RNAs targeting GOLM1 or overexpressing the protein to assess function in proliferation, viability, and migration and invasion in vitro using EdU, CCK8, clone-forming, Transwell assays, 3D tumor spheroid invasion assay and in vivo in orthotopic implantations. Protein lysates were used to screen a membrane-based antibody array to identify kinases mediated by GOLM1. Specific inhibitors of PDGFRα (AG1296) and AKT (MK-2206) were used to examine the regulation of PDGFA/PDGFRα on GOLM1 and the underlying pathway respectively.

RESULTS

qRT-PCR, immunohistochemistry and western blot analysis revealed GOLM1 expression to be elevated in glioma tissues and cell lines. Silencing of GOLM1 attenuated proliferation, migration, and invasion of U251, A172 and P3#GBM (primary glioma) cells, while overexpression of GOLM1 enhanced malignant behavior of U87MG cells. We further demonstrated that activation of AKT is the driving force of GOLM1-promoted glioma progression. The last finding of this research belongs to the regulation of PDGFA/PDGFRα on GOLM1, while GOLM1 was also a key element of PDGFA/PDGFRα-mediated activation of AKT, as well as the progression of glioma cells.

CONCLUSIONS

PDGFA/PDGFRα-regulated GOLM1 promotes glioma progression possibly through activation of a key signaling kinase, AKT. GOLM1 interference may therefore provide a novel therapeutic target and improve the efficacy of glioma treatment, particularly in the case of the proneural molecular subtype of human glioma.

Lack of Constitutively Active DNA Repair Sensitizes Glioblastomas to Akt Inhibition and Induces Synthetic Lethality with Radiation Treatment in a p53-Dependent Manner

Treatment refractory glioblastoma (GBM) remains a major clinical problem globally, and targeted therapies in GBM have not been promising to date. The Cancer Genome Atlas integrative analysis of GBM reported the striking finding of genetic alterations in the p53 and PI3K pathways in more than 80% of GBMs. Given the role of these pathways in making cell-fate decisions and responding to genotoxic stress, we investigated the reliance of these two pathways in mediating radiation resistance. We selected a panel of GBM cell lines and glioma stem cells (GSC) with wild-type TP53 (p53-wt) and mutant TP53, mutations known to interfere with p53 functionality (p53-mt). Cell lines were treated with a brain permeable inhibitor of P-Akt (ser473), phosphatidylinositol ether lipid analogue (PIA), with and without radiation treatment. Sensitivity to treatment was measured using Annexin-V/PI flow cytometry and Western blot analysis for the markers of apoptotic signaling, alkaline COMET assay. All results were verified in p53 isogenic cell lines. p53-mt cell lines were selectively radiosensitized by PIA. This radiosensitization effect corresponded with an increase in DNA damage and a decrease in DNA-PKcs levels. TP53 silencing in p53-wt cells showed a similar response as the p53-mt cells. In addition, the radiosensitization effects of Akt inhibition were not observed in normal human astrocytes, suggesting that this treatment strategy could have limited off-target effects. We demonstrate that the inhibition of the PI3K/Akt pathway by PIA radiosensitizes p53-mt cells by antagonizing DNA repair. In principle, this strategy could provide a large therapeutic window for the treatment of TP53-mutant tumors. Mol Cancer Ther; 17(2); 336-46. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."

ILK promotes cell proliferation in breast cancer cells by activating the PI3K/Akt pathway

Breast cancer is a very common malignant tumor, whose incidence ranks the first among various types of cancer in women worldwide. An important hallmark of cancer is the activation of oncogenes, which lead to overgrowth of cancer cells. Therefore, it is necessary to identify the critical genes involved in regulating the progression of breast cancer and elucidate the corresponding molecular mechanisms. The present study demonstrated that integrin‑linked kinase (ILK) overexpression promoted cell proliferation and growth in MCF‑7 cells, while ILK knockdown led to growth arrest in MDA‑MB‑231 cells. In addition, activation of the phosphoinositide 3‑kinase (PI3K)/Akt pathway was positively regulated by ILK, suggesting that the regulatory effects of ILK on cell growth and proliferation may be at least in part mediated by PI3K/Akt signaling. These results indicated that ILK promoted cell proliferation and growth in breast cancer cells through activation of the PI3K/Akt pathway, suggesting that ILK may be considered to be a potential therapeutic target for the therapy of breast cancer in the future.

Antiglioma effects of cytarabine on leptomeningeal metastasis of high-grade glioma by targeting the PI3K/Akt/mTOR pathway

Leptomeningeal metastasis (LM) of high-grade glioma is a highly lethal disease requiring new effective therapeutic measures. For both de novo or relapsed glioma with LM, intrathecal cytarabine chemotherapy is not frequently used for first-line and relapse protocols. We encountered a clinical case demonstrating effective application of cytarabine in high-grade glioma with LM, prompting us to explore the effects of cytarabine on malignant glioma and molecular mechanisms of such effects through in vivo and in vitro experiments. The U87 cell line was selected to represent human glioma for studies. Cell viability was measured by MTT assay, plate colony formation assay, and trypan-blue dye exclusion test. Apoptosis was assessed by flow cytometry. Protein expression levels were detected by Western blot assay and immunohistochemistry. mRNA expression was examined by quantitative real-time reverse transcription polymerase chain reaction. Cytarabine inhibited tumor growth during the in vivo experiment. The present study confirmed that cytarabine inhibits proliferation and promotes apoptosis of U87 cells, and molecular analysis of this effect showed that cytarabine significantly reduces expression of phosphatidylinositol 3-kinase/serine/threonine kinase also known as the protein kinase B/mechanistic target of rapamycin (PI3K/Akt/mTOR) pathway, Ki-67, BCL2, and 4-1BB, and upregulates Bax and cleaved caspase-3. Our findings indicated that intrathecal administration of cytarabine manifests potential in prophylaxis and treatment of malignant glioma with LM. Effective medications for high-grade glioma with LM should contain cytarabine.

Combination screening in vitro identifies synergistically acting KP372-1 and cytarabine against acute myeloid leukemia

Cytogenetic lesions often alter kinase signaling in acute myeloid leukemia (AML) and the addition of kinase inhibitors to the treatment arsenal is of interest. We have screened a kinase inhibitor library and performed combination testing to find promising drug-combinations for synergistic killing of AML cells. Cytotoxicity of 160 compounds in the library InhibitorSelect™ 384-Well Protein Kinase Inhibitor I was measured using the fluorometric microculture cytotoxicity assay (FMCA) in three AML cell lines. The 15 most potent substances were evaluated for dose-response. The 6 most cytotoxic compounds underwent combination synergy analysis based on the FMCA readouts after either simultaneous or sequential drug addition in AML cell lines. The 4 combinations showing the highest level of synergy were evaluated in 5 primary AML samples. Synergistic calculations were performed using the combination interaction analysis package COMBIA, written in R, using the Bliss independence model. Based on obtained results, an iterative combination search was performed using the therapeutic algorithmic combinatorial screen (TACS) algorithm. Of 160 substances, cell survival was ⩽50% at <0.5μM for Cdk/Crk inhibitor, KP372-1, synthetic fascaplysin, herbimycin A, PDGF receptor tyrosine kinase inhibitor IV and reference-drug cytarabine. KP372-1, synthetic fascaplysin or herbimycin A obtained synergy when combined with cytarabine in AML cell lines MV4-11 and HL-60. KP372-1 added 24h before cytarabine gave similar results in patient cells. The iterative search gave further improved synergy between cytarabine and KP372-1. In conclusion, our in vitro studies suggest that combining KP372-1 and cytarabine is a potent and synergistic drug combination in AML.

Creation of an apoptin-derived peptide that interacts with SH3 domains and inhibits glioma cell migration and invasion

Glioblastoma multiforme (GBM) is an aggressive tumor of the central nervous system characterized by high rates of recurrence, morbidity, and mortality. This study investigated the antitumor effects of an apoptin-derived peptide (ADP) on glioma cells and explored the underlying mechanisms. The U251, U87, and C6 glioma cell lines were used in the present study, and the expression of p-Akt, Akt, and MMP-9 was determined through Western blotting, quantitative real-time PCR, and hematoxylin and eosin (HE) staining. Tumor growth was evaluated by magnetic resonance imaging, and cell viability was assessed through an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay. Glioma cell metastasis was evaluated using transwell migration, invasion, and scratch-wound assays. An ADP was designed and synthesized based on the results of a domain-based analysis of the structure of apoptin. The ADP inhibited glioma cell viability, invasion and migration, and treatment with the synthesized ADP led to downregulation of p-Akt and MMP-9 and inhibited MMP-9 translation. The ADP also inhibited glioma invasion and migration in vivo, and HE staining showed decreases in the satellite-like invasion of cell masses and apoptotic cell populations after treatment with the ADP. Our findings demonstrate that treatment with an ADP can suppress glioma cell migration and invasion via the PI3K/Akt/MMP-9 signaling pathway and provide a new platform for the development of drugs for treating glioma.

The impact of heterogeneity in phosphoinositide 3-kinase pathway in human cancer and possible therapeutic treatments

Phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) plays a crucial role in the initiation and progress of cancerous tumors through the overexpression of the PI3K pathway promoting uncontrollable levels of cell proliferation. In addition only Class I PI3K has been discovered to be involved in human cancer due to its unique ability to produce phosphoinositide 3,4,5 trisphosphate (PIP3), which has been discovered to play a crucial role in human oncogenesis. The role of PIK3CA is lucubrated in breast cancer and gastric cancer, but is not well characterized in lung diseases. In this review, we summarized the common biology and mutations in PIK3CA with its related signaling pathways. Furthermore, we elucidated the PIK3CA heterogeneity in different domains, between various cancers and in different lung cancers. We also take a look at current inhibitors such as KP-372-1 (KP-1), KP-372-2 (KP-2), GSK690693, etc. in order to highlight potential treatment of PIK3CA mutations in human cancer and what directions future research should focus on.

Akt2 knock-down reveals its contribution to human lung cancer cell proliferation, growth, motility, invasion and endothelial cell tube formation

The Akt/PKB serine/threonine protein kinase consists of three isoforms: Akt-1, -2 and -3. Their overexpression has been detected in human cancers, but their roles in cancer progression are unclear. We investigated the impact of specific silencing of Akt1 and Akt2 on human lung cancer cell proliferation, colony growth, motility, and invasion in vitro as well as tumor growth in vivo using human Non-Small Cell Lung Cancer cells LNM35, and on the vascular tube formation using HUVEC cells. Although silencing of Akt1 decreased cellular invasion at least in part via COX-2 inhibition, it had almost no effect on cell motility, proliferation, colony formation, and angiogenesis. Transient as well as stable silencing of Akt2 resulted in a strong inhibition of Rb phosphorylation associated with a decrease in cellular proliferation and colony formation, leading to the inhibition of tumor growth in the xenograft model. Silencing of Akt2 also reduced cellular motility and invasion in vitro, presumably via COX-2 inhibition. Moreover, silencing of Akt2 in the HUVEC cells resulted in the inhibition of their spontaneous angiogenic phenotype. Altogether, these results indicate that Akt2 plays an important role in lung cancer progression and can be a promising target for lung cancer therapy.

SoNar, a Highly Responsive NAD+/NADH Sensor, Allows High-Throughput Metabolic Screening of Anti-tumor Agents

The altered metabolism of tumor cells confers a selective advantage for survival and proliferation, and studies have shown that targeting such metabolic shifts may be a useful therapeutic strategy. We developed an intensely fluorescent, rapidly responsive, pH-resistant, genetically encoded sensor of wide dynamic range, denoted SoNar, for tracking cytosolic NAD(+) and NADH redox states in living cells and in vivo. SoNar responds to subtle perturbations of various pathways of energy metabolism in real time, and allowed high-throughput screening for new agents targeting tumor metabolism. Among > 5,500 unique compounds, we identified KP372-1 as a potent NQO1-mediated redox cycling agent that produced extreme oxidative stress, selectively induced cancer cell apoptosis, and effectively decreased tumor growth in vivo. This study demonstrates that genetically encoded sensor-based metabolic screening could serve as a valuable approach for drug discovery.

miR-494-3p Regulates Cellular Proliferation, Invasion, Migration, and Apoptosis by PTEN/AKT Signaling in Human Glioblastoma Cells

Malignant gliomas are the most common primary brain tumors, and the molecular mechanisms involving their progression and recurrence are still largely unclear. Substantial data indicate that the oncogene miR-494-3p is significantly elevated in gliomas, but the molecular functions of miR-494-3p in gliomagenesis are largely unknown. The present study aimed to explore the role of miR-494-3p and its molecular mechanism in human brain gliomas, malignant glioma cell lines, and cancer stem-like cells. The expression level of miR-494-3p in 48 human glioma issues and 8 normal brain tissues was determined using stem-loop real-time polymerase chain reaction (PCR). To study the function of miR-494-3p inhibitor in glioma cells, the miR-494-3p inhibitor lentivirus was used to transfect glioma cells. Transwell invasion system was used to estimate the effects of miR-494-3p inhibitor on the invasiveness of glioma cells. A mouse model was used to test the effect of miR-494-3p inhibitor on glioma proliferation and invasion in vivo. Results showed that the expression of miR-494-3p in human brain glioma tissues was higher than in normal brain tissues. Downregulated expression of miR-494-3p can inhibit the invasion and proliferation and promote apoptosis in glioma cells. Quantitative reverse transcription PCR and Western blotting analysis revealed that the expression of PTEN was increased after downexpression of miR-494-3p in glioma cells (U87 and U251). miR-494-3p inhibitor could prevent migration, invasion, proliferation, and promote apotosis in gliomas through PTEN/AKT pathway. Therefore, the study results have shown that miR-494-3p may act as a therapeutic target in gliomas.

Cell death pathway induced by resveratrol-bovine serum albumin nanoparticles in a human ovarian cell line

Resveratrol-bovine serum albumin nanoparticles (RES-BSANP) exhibit chemotherapeutic properties, which trigger apoptosis. The aim of the present study was to investigate the caspase-independent cell death pathway induced by RES-BSANP in human ovarian cancer SKOV3 cells and to analyze its mechanism. Morphological changes were observed by apoptotic body/cell nucleus DNA staining using inverted and fluorescence microscopy. The cell death pathway was determined by phosphatidylserine translocation. Western blot analysis was conducted to detect the activation of apoptosis-inducing factor (AIF), cytochrome c (Cyto c) and B-cell lymphoma 2-associated X protein (Bax). Apoptotic body and nuclear condensation and fragmentation were observed simultaneously following treatment with RES-BSANP. RES-BSANP induced apoptosis in a dose-dependent manner in the human ovarian cancer SKOV3 cells. The translocation of AIF from the mitochondria to the cytoplasm occurred earlier than that of Cyto c. In addition, Bax binding to the mitochondria was required for the release of AIF and Cyto c from the mitochondria. The AIF apoptosis pathway may present an alternative caspase-dependent apoptosis pathway in human ovarian cell death induced by RES-BSANP. Elucidation of this pathway may be critical for the treatment of cancer using high doses of RES-BSANP.

Exogenous endothelin-1 induces cell migration and matrix metalloproteinase expression in U251 human glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and lethal type of primary brain tumor characterized by its rapid infiltration to surrounding tissues during the early stages. The fast spreading of GBM obscures the initiation of the tumor mass making the treatment outcome undesirable. Endothelin-1 is known as a secretory protein presented in various types of brain cells, which has been indicated as a factor for cancer pathology. The aim of the present study was to investigate the molecular mechanism of cell migration in GBM. We found that various malignant glioma cells expressed higher amounts of endothelin-1, ETA, and ETB receptors than nonmalignant human astrocytes. The application of endothelin-1 enhanced the migratory activity in human U251 glioma cells corresponding to increased expression of matrix metalloproteinase (MMP)-9 and MMP-13. The endothelin-1-induced cell migration was attenuated by MMP-9 and MMP-13 inhibitors and inhibitors of mitogen-activated protein (MAP) kinase and PI3 kinase/Akt. Furthermore, the elevated levels of phosphate c-Jun accumulation in the nucleus and activator protein-1 (AP-1)-DNA binding activity were also found in endothelin-1 treated glioma cells. In migration-prone sublines, cells with greater migration ability showed higher endothelin-1, ETB receptor, and MMP expressions. These results indicate that endothelin-1 activates MAP kinase and AP-1 signaling, resulting in enhanced MMP-9 and MMP-13 expressions and cell migration in GBM.

Osthole suppresses the migratory ability of human glioblastoma multiforme cells via inhibition of focal adhesion kinase-mediated matrix metalloproteinase-13 expression

Glioblastoma multiforme (GBM) is the most common type of primary and malignant tumor occurring in the adult central nervous system. GBM often invades surrounding regions of the brain during its early stages, making successful treatment difficult. Osthole, an active constituent isolated from the dried C. monnieri fruit, has been shown to suppress tumor migration and invasion. However, the effects of osthole in human GBM are largely unknown. Focal adhesion kinase (FAK) is important for the metastasis of cancer cells. Results from this study show that osthole can not only induce cell death but also inhibit phosphorylation of FAK in human GBM cells. Results from this study show that incubating GBM cells with osthole reduces matrix metalloproteinase (MMP)-13 expression and cell motility, as assessed by cell transwell and wound healing assays. This study also provides evidence supporting the potential of osthole in reducing FAK activation, MMP-13 expression, and cell motility in human GBM cells.

Molecularly targeted therapies for malignant gliomas: advances and challenges

The identification of molecular markers associated with tumor but not with normal tissue has allowed the development of highly specific, targeted therapies for the treatment of cancer. Over the last several years, tremendous advances in our understanding of the genetic and molecular changes involved in the progression of malignant gliomas have triggered a large effort in the development of targeted therapies to treat these tumors. However, to date only a modest clinical benefit, limited to subsets of patients, has been demonstrated. Furthermore, despite a high degree of target selectivity, the use of targeted therapies often has systemic toxicity. The reasons behind this limited clinical success are complex and include the intricacy of the signaling pathways in gliomas and the heterogeneity of the disease process, compounded by existing limitations in assessing the efficacy of these novel agents when conventional end points and clinical trial designs are utilized. However, despite these difficulties targeted therapies remain a very attractive avenue of treatment for malignant gliomas. Three basic approaches are needed to overcome the hurdles associated with targeted therapies: first, further development of genetic profiling techniques will help to better determine the genetic changes and molecular pathways involved in gliomas and will potentially allow the design of individualized therapies based on the genetic and molecular signature of each tumor. Second, there is a need for the development of better combination strategies (complementary targeted agents or targeted agents with chemotherapy drugs) directed towards disease heterogeneity. Third, we need to optimize the design of preclinical and clinical trials to obtain the maximum amount of information in the shortest period of time.

Anti-cancer Therapies in High Grade Gliomas

High grade gliomas represent one of the most aggressive and treatment-resistant types of human cancer, with only 1–2 years median survival rate for patients with grade IV glioma. The treatment of glioblastoma is a considerable therapeutic challenge; combination therapy targeting multiple pathways is becoming a fast growing area of research. This review offers an up-to-date perspective of the literature about current molecular therapy targets in high grade glioma, that include angiogenic signals, tyrosine kinase receptors, nodal signaling proteins and cancer stem cells related approaches. Simultaneous identification of proteomic signatures could provide biomarker panels for diagnostic and personalized treatment of different subsets of glioblastoma. Personalized medicine is starting to gain importance in clinical care, already having recorded a series of successes in several types of cancer; nonetheless, in brain tumors it is still at an early stage.

Therapeutic targeting of EGFR-activated metabolic pathways in glioblastoma

INTRODUCTION

The highly divergent histological heterogeneities, aggressive invasion and extremely poor response to treatment make glioblastoma (GBM) one of the most lethal and difficult cancers in humans. Among key elements driving its behavior is epidermal growth factor receptor (EGFR), however, neither traditional therapy including neurosurgery, radiation, temozolomide, nor targeted EGFR therapeutics in clinic has generated promising results to date. Strategies are now focusing on blocking the downstream EGFR-activated metabolic pathways and the key phosphorylated kinases.

AREAS COVERED

Here, we review two major EGFR-activated downstream metabolic pathways including the PI3K/AKT/mTOR and RAS/RAF/MAPK pathways and their key phosphorylated kinase alterations in GBMs. This review also discusses potential pharmacological progress from bench work to clinical trials in order to evaluate specific inhibitors as well as therapeutics targeting PI3K and RAS signaling pathways.

EXPERT OPINION

Several factors impede clinical progress in targeting GBM, including the high rates of acquired resistance, heterogeneity within and across the tumors, complexity of signaling pathways and difficulty in traversing the blood-brain barrier (BBB). Substantial insight into genetic and molecular pathways and strategies to better tap the potential of these agents include rational combinatorial regimens and molecular phenotype-based patient enrichment, each of which will undoubtedly generate new therapeutic approaches to combat these devastating disabilities in the near future.

DARPP32, STAT5 and STAT3 mRNA expression ratios in glioblastomas are associated with patient outcome

Based on recent developments in glioblastoma subtyping, we examined DARPP32 (PPP1R1B), a neuronal marker against STAT5 and STAT3 that are pro-oncogenic in glioblastoma. mRNA ratios of DARPP32, STAT1, STAT3, STAT5A and STAT5B were assessed in routinely diagnosed gliomas s including a series of glioblastomas from patients (n = 67) treated with chemoradiotherapy (temozolomide), out of which 88 % had sequencing validated IDH-negative disease. DARPP32/STAT1 (p = 0.0007), DARPP32/STAT3 (p = 0.0004) and DARPP32/STAT5B (p = 0.0039) ratios were significantly higher in grade II and III as compared to grade IV tumours. The same high ratios were also associated with absence of immunohistochemically assessed AKT/PKB phosphorylation and survivin protein expression. High DARPP32/STAT3, DARPP32/STAT5B, and STAT5B/STAT3 ratios were associated with longer patient progression free (PFS) and overall survival (OS). Upon multivariate analysis, total/subtotal removal of the tumour (HR:0.431; 95%CI:0.241-0.771, Wald p = 0.005), high DARPP32/STAT5B (HR:0.341; 95%CI:0.169-0.690; Wald p = 0.003) and STAT5B/STAT3 mRNA ratios (HR:0.480; 95%CI:0.280-0.824; Wald p = 0.008) were independent favorable parameters for prolonged PFS. Extent of surgery (HR:0.198; 95%CI:0.101-0.390; p < 0.001) and high DARPP32/STAT5A ratios (HR:0.320; 95%CI:0.160-0.638, p = 0.001) were independently predictive for longer OS. The presented approach is applicable for prospective validation and appears promising towards an effective glioblastoma patient stratification in addition to IDH mutations. These data may contribute to understanding the biology of gliomas with respect to their potential neuronal characteristics and justify STAT-inhibiting therapeutic interventions in the same tumour system.

PI3K and Akt as molecular targets for cancer therapy: current clinical outcomes

The PI3K-Akt pathway is a vital regulator of cell proliferation and survival. Alterations in the PIK3CA gene that lead to enhanced PI3K kinase activity have been reported in many human cancer types, including cancers of the colon, breast, brain, liver, stomach and lung. Deregulation of PI3K causes aberrant Akt activity. Therefore targeting this pathway could have implications for cancer treatment. The first generation PI3K-Akt inhibitors were proven to be highly effective with a low IC(50), but later, they were shown to have toxic side effects and poor pharmacological properties and selectivity. Thus, these inhibitors were only effective in preclinical models. However, derivatives of these first generation inhibitors are much more selective and are quite effective in targeting the PI3K-Akt pathway, either alone or in combination. These second-generation inhibitors are essentially a specific chemical moiety that helps to form a strong hydrogen bond interaction with the PI3K/Akt molecule. The goal of this review is to delineate the current efforts that have been undertaken to inhibit the various components of the PI3K and Akt pathway in different types of cancer both in vitro and in vivo. Our focus here is on these novel therapies and their inhibitory effects that depend upon their chemical nature, as well as their development towards clinical trials.

Neurokinin-1 receptor directly mediates glioma cell migration by up-regulation of matrix metalloproteinase-2 (MMP-2) and membrane type 1-matrix metalloproteinase (MT1-MMP)

Neurokinin-1 receptor (NK1R) occurs naturally on human glioblastomas. Its activation mediates glioma cell proliferation. However, it is unknown whether NK1R is directly involved in tumor cell migration. In this study, we found human hemokinin-1 (hHK-1), via NK1R, dose-dependently promoted the migration of U-251 and U-87 cells. In addition, we showed that hHK-1 enhanced the activity of MMP-2 and the expression of MMP-2 and MT1-matrix metalloproteinase (MMP), which were responsible for cell migration, because neutralizing the MMPs with antibodies decreased cell migration. The involved mechanisms were then investigated. In U-251, hHK-1 induced significant calcium efflux; phospholipase C inhibitor U-73122 reduced the calcium mobilization, the up-regulation of MMP-2 and MT1-MMP, and the cell migration induced by hHK-1, which meant the migration effect of NK1R was mainly mediated through the G(q)-PLC pathway. We further demonstrated that hHK-1 boosted rapid phosphorylation of ERK, JNK, and Akt; inhibition of ERK and Akt effectively reduced MMP-2 induction by hHK-1. Meanwhile, inhibition of ERK, JNK, and Akt reduced the MT1-MMP induction. hHK-1 stimulated significant phosphorylation of p65 and c-JUN in U-251. Reporter gene assays indicated hHK-1 enhanced both AP-1 and NF-κB activity; inhibition of ERK, JNK, and Akt dose-dependently suppressed the NF-κB activity; only the inhibition of ERK significantly suppressed the AP-1 activity. Treatment with specific inhibitors for AP-1 or NF-κB strongly blocked the MMP up-regulation by hHK-1. Taken together, our data suggested NK1R was a potential regulator of human glioma cell migration by the up-regulation of MMP-2 and MT1-MMP.

Osteopontin increases heme oxygenase-1 expression and subsequently induces cell migration and invasion in glioma cells

Malignant gliomas are associated with high morbidity and mortality because they are highly invasive into surrounding brain tissue, making complete surgical resection impossible. Osteopontin is abundantly expressed in the brain and is involved in cell adhesion, migration, and invasion. The aim of the present study was to investigate the mechanisms of glioma cell migration. Migration and invasion activity were determined by transwell and wound-healing assays. Gene and protein expressions were analyzed by reverse transcription-PCR, real time-PCR, and Western blotting. Nrf2-DNA binding activity was determined by electrophoretic mobility shift assay. Establishment of migration-prone sublines were performed to select highly migratory glioma. An intracranial xenograft mouse model was used for the in vivo study. Application of recombinant human osteopontin enhanced the migration of glioma cells. Expression of heme oxygenase (HO)-1 mRNA and protein also increased in response to osteopontin stimulation. Osteopontin-induced increase in cell migration was antagonized by HO-1 inhibitor or HO-1 small interfering (si)RNA. Osteopontin-mediated HO-1 expression was reduced by treatment with MEK/ERK and phosphatidylinositol 3-kinase/Akt inhibitors, as well as siRNA against Nrf2. Furthermore, osteopontin stimulated Nrf2 accumulation in the nucleus and increased Nrf2-DNA binding activity. In migration-prone sublines, cells with greater migration ability had higher osteopontin and HO-1 expression, and zinc protoporphyrin IX treatment could effectively reduce the enhanced migration ability. In an intracranial xenograft mouse model, transplantation of migration-prone subline cells exhibited higher cell migration than parental tumor cells. These results indicate that osteopontin activates Nrf2 signaling, resulting in enhanced HO-1 expression and cell migration in glioma cells.

The novel phloroglucinol derivative BFP induces apoptosis of glioma cancer through reactive oxygen species and endoplasmic reticulum stress pathways

Prenyl-phloroglucinol derivatives from hop plants have been shown to have anticancer activities. This study is the first to investigate the anticancer effects of the new phloroglucinol derivative (2,4-bis(4-fluorophenylacetyl)phloroglucinol; BFP). BFP induced cell death and anti-proliferation in three glioma, U251, U87 and C6 cells, but not in primary human astrocytes. BFP-induced concentration-dependently cell death in glioma cells was determined by MTT and SRB assay. Moreover, BFP-induced apoptotic cell death in glioma cells was measured by Hochest 33258 staining and fluorescence-activated cell sorter (FACS) of propidine iodine (PI) analysis. Treatment of U251 human glioma cells with BFP was also found to induce reactive oxygen species (ROS) generation, which was detected by a fluorescence dye used FACS analysis. Treatment of BFP also increased a number of signature endoplasmic reticulum (ER) stress markers glucose-regulated protein (GRP)-78, GRP-94, IRE1, phosphorylation of eukaryotic initiation factor-2α (eIF-2α) and up-regulation of CAAT/enhancer-binding protein homologous protein (CHOP). Moreover, treatment of BFP also increased the down-stream caspase activation, such as pro-caspase-7 and pro-caspase-12 degradation, suggesting the induction of ER stress. Furthermore, BFP also induced caspase-9 and caspase-3 activation as well as up-regulation of cleaved PARP expression. Treatment of antioxidants, or pre-transfection of cells with GRP78 or CHOP siRNA reduced BFP-mediated apoptotic-related protein expression. Taken together, the present study provides evidences to support that ROS generation, GRP78 and CHOP activation are mediating the BFP-induced human glioma cell apoptosis.

Wogonin induces reactive oxygen species production and cell apoptosis in human glioma cancer cells

Glioma is the most common primary adult brain tumor with poor prognosis because of the ease of spreading tumor cells to other regions of the brain. Cell apoptosis is frequently targeted for developing anti-cancer drugs. In the present study, we have assessed wogonin, a flavonoid compound isolated from Scutellaria baicalensis Georgi, induced ROS generation, endoplasmic reticulum (ER) stress and cell apoptosis. Wogonin induced cell death in two different human glioma cells, such as U251 and U87 cells but not in human primary astrocytes (IC 50 > 100 μM). Wogonin-induced apoptotic cell death in glioma cells was measured by propidine iodine (PI) analysis, Tunnel assay and Annexin V staining methods. Furthermore, wogonin also induced caspase-9 and caspase-3 activation as well as up-regulation of cleaved PARP expression. Moreover, treatment of wogonin also increased a number of signature ER stress markers glucose-regulated protein (GRP)-78, GRP-94, Calpain I, and phosphorylation of eukaryotic initiation factor-2α (eIF2α). Treatment of human glioma cells with wogonin was found to induce reactive oxygen species (ROS) generation. Wogonin induced ER stress-related protein expression and cell apoptosis was reduced by the ROS inhibitors apocynin and NAC (N-acetylcysteine). The present study provides evidence to support the fact that wogonin induces human glioma cell apoptosis mediated ROS generation, ER stress activation and cell apoptosis.

Regulation of cellular growth, apoptosis, and Akt activity in human U251 glioma cells by a combination of cisplatin with CRM197

The aberrantly activated antiapoptotic phospatidyl-3-inositol-kinase (PI3K)/Akt signaling induced by cisplatin limits the effectiveness of chemotherapy; inhibition of this pathway may augment the sensitivity of tumor cells to cisplatin-induced toxicity and promote apoptosis. Cross-reacting material 197 (CRM197), the nontoxic mutant of diphtheria toxin, could act as an heparin-binding epidermal growth factor inhibitor and has been shown to have some anticancer effects, but the effect of CRM197 on glioma cells remains unclear. The aim of this study was to investigate the effects of a combination of cisplatin with CRM197 on the growth and apoptosis of human U251 glioma cells and the possible mechanism. In this study, we demonstrated that cisplatin or CRM197 induced a dose-dependent growth inhibition in U251 cells, but cisplatin at 5 µg/ml and CRM197 at 1 µg/ml did not affect the viability of human astrocytes. Cisplatin induced a time-dependent growth inhibition in U251 cells, whereas the growth-inhibitory effects induced by CRM197 alone or combined with cisplatin reached a peak at 24 h after treatment. Compared with the administration of cisplatin or CRM197 alone, CRM197 combined with cisplatin significantly enhanced U251 cell growth inhibition and apoptosis. Cisplatin induced sustained activation of Akt, whereas CRM197 markedly suppressed the Akt phosphorylation induced by cisplatin. The effects of growth inhibition and apoptosis were markedly enhanced after a combination of cisplatin with CRM197 plus the PI3K inhibitor LY294002 or wortmannin. Therefore, CRM197 combined with cisplatin could enhance growth inhibition and apoptosis of glioma cells by inhibiting the cisplatin-induced PI3K/Akt pathway.

Shared molecular targets in pediatric gliomas and ependymomas

BACKGROUND

Recent advances in multidisciplinary treatment approaches have improved the overall prognosis of pediatric brain tumors, but some patients remain refractory to treatment and do poorly. Several molecularly targeted therapies are under development for the treatment of brain tumors, and high-grade gliomas in adults are a particular area of study.

PROCEDURE

To better understand if these new therapies can be used in pediatric populations, we examined the expression of the following seven marker genes involved in signaling pathways targeted by new therapies: β-catenin, suppressor of fused (SUFU), erythroblastic leukemia viral oncogene homolog (ERBB) 2, platelet-derived growth factor receptorα (PDGFRα), proliferating cell nuclear antigen (PCNA), secreted protein acid and rich in cysteine (SPARC), and granulocyte colony-stimulating factor receptor (G-CSFR). Samples from 27 patients with the primitive neuroectodermal tumor (PNET)/medulloblastomas (MBs) (n = 8), ependymomas (n = 5), or gliomas (n = 14) were assessed by quantitative real-time PCR. [Correction made here after initial online publication]. We assigned an EXP score to compare across samples and determined the levels of gene expression among tumor cell types.

RESULTS

Gene expression varied among the different tumors, but, within a tumor type, clear expression patterns were seen. The expression of SUFU, ERBB2, and PCNA in metastatic MBs were greater than that seen in non-metastatic MBs. Most glioma cases highly expressed PDGFRα and G-CSFR. Additionally, the expression patterns of gliomas and ependymomas were similar (r = 0.77, P = 0.04), but PNET/MBs substantially differed from gliomas (r = -0.37, P = 0.41) or ependymomas (r = 0.23, P = 0.62).

CONCLUSIONS

The development of new drugs targeting up-regulated pathways may be useful for the treatment of pediatric brain tumors. As new drugs are developed, gliomas and ependymomas may be treated with similar compounds.

The Akt signaling pathway: an emerging therapeutic target in malignant melanoma

Studies using cultured melanoma cells and patient tumor biopsies have demonstrated deregulated PI3 kinase-Akt3 pathway activity in ~70% of melanomas. Furthermore, targeting Akt3 and downstream PRAS40 has been shown to inhibit melanoma tumor development in mice. Although these preclinical studies and several other reports using small interfering RNAs and pharmacological agents targeting key members of this pathway have been shown to retard melanoma development, analysis of early Phase I and Phase II clinical trials using pharmacological agents to target this pathway demonstrate the need for (1) selection of patients whose tumors have PI3 kinase-Akt pathway deregulation, (2) further optimization of therapeutic agents for increased potency and reduced toxicity, (3) the identification of additional targets in the same pathway or in other signaling cascades that synergistically inhibit the growth and progression of melanoma, and (4) better methods for targeted delivery of pharmaceutical agents inhibiting this pathway. In this review we discuss key potential targets in PI3K-Akt3 signaling, the status of pharmacological agents targeting these proteins, drugs under clinical development, and strategies to improve the efficacy of therapeutic agents targeting this pathway.

Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR inhibitors: rationale and importance to inhibiting these pathways in human health

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Integral components of these pathways, Ras, B-Raf, PI3K, and PTEN are also activated/inactivated by mutations. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of these pathways can contribute to chemotherapeutic drug resistance, proliferation of cancer initiating cells (CICs) and premature aging. This review will evaluate more recently described potential uses of MEK, PI3K, Akt and mTOR inhibitors in the proliferation of malignant cells, suppression of CICs, cellular senescence and prevention of aging. Ras/Raf/MEK/ERK and Ras/PI3K/PTEN/Akt/mTOR pathways play key roles in the regulation of normal and malignant cell growth. Inhibitors targeting these pathways have many potential uses from suppression of cancer, proliferative diseases as well as aging.

Current review of in vivo GBM rodent models: emphasis on the CNS-1 tumour model

GBM (glioblastoma multiforme) is a highly aggressive brain tumour with very poor prognosis despite multi-modalities of treatment. Furthermore, recent failure of targeted therapy for these tumours highlights the need of appropriate rodent models for preclinical studies. In this review, we highlight the most commonly used rodent models (U251, U86, GL261, C6, 9L and CNS-1) with a focus on the pathological and genetic similarities to the human disease. We end with a comprehensive review of the CNS-1 rodent model.

A novel oncolytic herpes simplex virus that synergizes with phosphoinositide 3-kinase/Akt pathway inhibitors to target glioblastoma stem cells

PURPOSE

To develop a new oncolytic herpes simplex virus (oHSV) for glioblastoma (GBM) therapy that will be effective in glioblastoma stem cells (GSC), an important and untargeted component of GBM. One approach to enhance oHSV efficacy is by combination with other therapeutic modalities.

EXPERIMENTAL DESIGN

MG18L, containing a U(S)3 deletion and an inactivating LacZ insertion in U(L)39, was constructed for the treatment of brain tumors. Safety was evaluated after intracerebral injection in HSV-susceptible mice. The efficacy of MG18L in human GSCs and glioma cell lines in vitro was compared with other oHSVs, alone or in combination with phosphoinositide-3-kinase (PI3K)/Akt inhibitors (LY294002, triciribine, GDC-0941, and BEZ235). Cytotoxic interactions between MG18L and PI3K/Akt inhibitors were determined using Chou-Talalay analysis. In vivo efficacy studies were conducted using a clinically relevant mouse model of GSC-derived GBM.

RESULTS

MG18L was severely neuroattenuated in mice, replicated well in GSCs, and had anti-GBM activity in vivo. PI3K/Akt inhibitors displayed significant but variable antiproliferative activities in GSCs, whereas their combination with MG18L synergized in killing GSCs and glioma cell lines, but not human astrocytes, through enhanced induction of apoptosis. Importantly, synergy was independent of inhibitor sensitivity. In vivo, the combination of MG18L and LY294002 significantly prolonged survival of mice, as compared with either agent alone, achieving 50% long-term survival in GBM-bearing mice.

CONCLUSIONS

This study establishes a novel therapeutic strategy: oHSV manipulation of critical oncogenic pathways to sensitize cancer cells to molecularly targeted drugs. MG18L is a promising agent for the treatment of GBM, being especially effective when combined with PI3K/Akt pathway-targeted agents.

Molecular tools: biology, prognosis, and therapeutic triage

Diffuse gliomas in adults continue to have a dismal prognosis with the current standard therapeutic methods, including maximal surgical resection, radiation, and chemotherapy. The pathogenesis of adult glioma is complex, involving the loss of function of tumor suppressor genes and activation of oncogenes, which are involved in a network of interconnected signaling pathways. Through activation of these pathways, characteristics of malignant gliomas, including uncontrolled proliferation and growth, invasion, and angiogenesis, are driven. Evolving therapeutic approaches are focused on specifically targeting these genetic lesions. This content gives an overview of the current knowledge about the pathogenesis of adult diffuse gliomas, emphasizing new targeted treatment approaches.