Mechanisms of disease: the PI3K-Akt-PTEN signaling node--an intercept point for the control of angiogenesis in brain tumors

Rigosertib is more potent than wortmannin and rapamycin against adult T-cell leukemia-lymphoma

Human T lymphotropic virus type 1 (HTLV-1) infection can cause adult T-cell lymphoblastic leukemia (ATLL), an incurable, chemotherapy-resistant malignancy. In a quest for new therapeutic targets, our study sought to determine the levels of AKT, mTOR, and PI3K in ATLL MT-2 cells, HTLV-1 infected NIH/3T3 cells (Inf-3T3), and HTLV-1 infected patients (Carrier, HAM/TSP, and ATLL). Furthermore, the effects of rigosertib, wortmannin, and rapamycin on the PI3K/Akt/mTOR pathway to inhibit the proliferation of ATLL cells were examined. The results showed that mRNA expression of Akt/PI3K/mTOR was down-regulated in carrier, HAM/TSP, and ATLL patients, as well as MT-2, and Inf-3T3 cells, compared to the healthy individuals and untreated MT-2 and Inf-3T3 as controls. However, western blotting revealed an increase in the phosphorylated and activated forms of AKT and mTOR. Treating the cells with rapamycin, wortmannin, and rigosertib decreased the phosphorylated forms of Akt and mTOR and restored their mRNA expression levels. Using these inhibitors also significantly boosted the expression of the pro-apoptotic genes, Bax/Bcl-2 ratio as well as the expression of the tumor suppressor gene p53 in the MT-2 and Inf-3T3cells. Rigosertib was more potent than wortmannin and rapamycin in inducing sub-G1 and G2-M cell cycle arrest, as well as late apoptosis in the Inf-3T3 and MT-2 cells. It also synergized the cytotoxic effects of vincristine. These findings demonstrate that HTLV-1 downregulation of the mRNA level may occur as a negative feedback response to increased PI3K-Akt-mTOR phosphorylation by HTLV-1. Therefore, using rigosertib alone or in combination with common chemotherapy drugs may be beneficial in ATLL patients.

Research progress in molecular pathology markers in medulloblastoma

Medulloblastoma (MB) is the commonest primary malignant brain cancer. The current treatment of MB is usually surgical resection combined with radiotherapy or chemotherapy. Although great progress has been made in the clinical management of MB, tumor metastasis and recurrence are still the main cause of death. Therefore, definitive and timely diagnosis is of great importance for improving therapeutic effects on MB. In 2016, the World Health Organization (WHO) divided MB into four subtypes: wingless-type mouse mammary tumor virus integration site (WNT), sonic hedgehog (SHH), non-WNT/non-SHH group 3, and group 4. Each subtype of MB has a unique profile in copy number variation, DNA alteration, gene transcription, or post-transcriptional/translational modification, all of which are associated with different biological manifestations, clinical features, and prognosis. This article reviewed the research progress of different molecular pathology markers in MB and summarized some targeted drugs against these molecular markers, hoping to stimulate the clinical application of these molecular markers in the classification, diagnosis, and treatment of MB.

How do phosphodiesterase-5 inhibitors affect cancer? A focus on glioblastoma multiforme

Since the discovery of phosphodiesterase-5 (PDE5) enzyme overexpression in the central nervous system (CNS) malignancies, investigations have explored the potential capacity of current PDE5 inhibitor drugs for repositioning in the treatment of brain tumors, notably glioblastoma multiforme (GBM). It has now been recognized that these drugs increase brain tumors permeability and enhance standard chemotherapeutics effectiveness. More importantly, studies have highlighted the promising antitumor functions of PDE5 inhibitors, e.g., triggering apoptosis, suppressing tumor cell growth and invasion, and reversing tumor microenvironment (TME) immunosuppression in the brain. However, contradictory reports have suggested a pro-oncogenic role for neuronal cyclic guanosine monophosphate (cGMP), indicating the beneficial function of PDE5 in the brain of GBM patients. Unfortunately, due to the inconsistent preclinical findings, only a few clinical trials are evaluating the therapeutic value of PDE5 inhibitors in GBM treatment. Accordingly, additional studies should be conducted to shed light on the precise effect of PDE5 inhibitors in GBM biology regarding the existing molecular heterogeneities among individuals. Here, we highlighted and discussed the previously investigated mechanisms underlying the impacts of PDE5 inhibitors in cancers, focusing on GBM to provide an overview of current knowledge necessary for future studies.

Role of Inflammatory Mediators, Macrophages, and Neutrophils in Glioma Maintenance and Progression: Mechanistic Understanding and Potential Therapeutic Applications

Simple Summary

The tumor microenvironment is a complex network comprised of neoplastic and a variety of immune cells, proteins, and inflammatory mediators. Previous studies have shown that during cancer progression, diverse inflammatory molecules, either directly or indirectly via recruiting immune cells, support the process of carcinogenesis. The present review focuses on the mechanistic understanding of the oncogenic role of these inflammatory mediators and immune cells, particularly tumor-associated macrophages (TAMs) and tumor-associated neutrophils (TANs) in glioma maintenance and progression. Moreover, the potential therapeutic benefits of targeting inflammatory mediators, immune cells, and associated signaling pathways in glioma genesis have also been discussed.

Abstract

Gliomas are the most common, highly malignant, and deadliest forms of brain tumors. These intra-cranial solid tumors are comprised of both cancerous and non-cancerous cells, which contribute to tumor development, progression, and resistance to the therapeutic regimen. A variety of soluble inflammatory mediators (e.g., cytokines, chemokines, and chemotactic factors) are secreted by these cells, which help in creating an inflammatory microenvironment and contribute to the various stages of cancer development, maintenance, and progression. The major tumor infiltrating immune cells of the tumor microenvironment include TAMs and TANs, which are either recruited peripherally or present as brain-resident macrophages (microglia) and support stroma for cancer cell expansion and invasion. These cells are highly plastic in nature and can be polarized into different phenotypes depending upon different types of stimuli. During neuroinflammation, glioma cells interact with TAMs and TANs, facilitating tumor cell proliferation, survival, and migration. Targeting inflammatory mediators along with the reprogramming of TAMs and TANs could be of great importance in glioma treatment and may delay disease progression. In addition, an inhibition of the key signaling pathways such as NF-κB, JAK/STAT, MAPK, PI3K/Akt/mTOR, and TLRs, which are activated during neuroinflammation and have an oncogenic role in glioblastoma (GBM), can exert more pronounced anti-glioma effects.

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.

The impact of microRNAs on myeloid-derived suppressor cells in cancer

Inflammation promotes cancer development. To a large extent, this can be attributed to the recruitment of myeloid-derived suppressor cells (MDSCs) to tumors. These cells are known for establishing an immunosuppressive tumor microenvironment by suppressing T cell activities. However, MDSCs also promote metastasis and angiogenesis. Critically, as small non-coding RNAs that regulate gene expression, microRNAs (miRNAs) control MDSC activities. In this review, we discuss how miRNA networks regulate key MDSC signaling pathways, how they shape MDSC development, differentiation and activation, and how this impacts tumor development. By targeting the expression of miRNAs in MDSCs, we can alter their main signaling pathways. In turn, this can compromise their ability to promote multiple hallmarks of cancer. Therefore, this may represent a new powerful strategy for cancer immunotherapy.

Rapamycin-Loaded Lipid Nanocapsules Induce Selective Inhibition of the mTORC1-Signaling Pathway in Glioblastoma Cells

Inhibition of the PI3K/Akt/mTOR signaling pathway represents a potential issue for the treatment of cancer, including glioblastoma. As such, rapamycin that inhibits the mechanistic target of rapamycin (mTOR), the downstream effector of this signaling pathway, is of great interest. However, clinical development of rapamycin has floundered due to the lack of a suitable formulation of delivery systems. In the present study, a novel method for the formulation of safe rapamycin nanocarriers is investigated. A phase inversion process was adapted to prepare lipid nanocapsules (LNCs) loaded with the lipophilic and temperature sensitive rapamycin. Rapamycin-loaded LNCs (LNC-rapa) are ~110 nm in diameter with a low polydispersity index (<0.05) and the zeta potential of about −5 mV. The encapsulation efficiency, determined by spectrophotometry conjugated with filtration/exclusion, was found to be about 69%, which represents 0.6 wt% of loading capacity. Western blot analysis showed that LNC-rapa do not act synergistically with X-ray beam radiation in U87MG glioblastoma model in vitro. Nevertheless, it demonstrated the selective inhibition of the phosphorylation of mTORC1 signaling pathway on Ser2448 at a concentration of 1 μM rapamycin in serum-free medium. Interestingly, cells cultivated in normoxia (21% O₂) seem to be more sensitive to mTOR inhibition by rapamycin than those cultivated in hypoxia (0.4% O₂). Finally, we also established that mTOR phosphorylation inhibition by LNC-rapa induced a negative feedback through the activation of Akt phosphorylation. This phenomenon was more noticeable after stabilization of HIF-1α in hypoxia.

Lipid-Based Nanocarriers for The Treatment of Glioblastoma

Glioblastoma multiforme (GBM) is the most common and malignant neoplasia having origin in the brain. The current treatments involve surgery, radiotherapy, and chemotherapy, being complete surgical resection the best option for the patient survival chances. However, in those cases where a complete removal is not possible, radiation and chemotherapy are applied. Herein, the main challenges of chemotherapy, and how they can be overcome with the help of nanomedicine, are approached. Natural pathways to cross the blood-brain barrier (BBB) are detailed, and different in vivo studies where these pathways are mimicked functionalizing the nanomaterial surface are shown. Later, lipid-based nanocarriers, such as liposomes, solid lipid nanoparticles, and nanostructured lipid carriers, are presented. To finish, recent studies that have used lipid-based nanosystems carrying not only therapeutic agents, yet also magnetic nanoparticles, are described. Although the advantages of using these types of nanosystems are explained, including their biocompatibility, the possibility of modifying their surface to enhance the cell targeting, and their intrinsic ability of BBB crossing, it is important to mention that research in this field is still at its early stage, and extensive preclinical and clinical investigations are mandatory in the close future.

Radioresistance in Glioblastoma and the Development of Radiosensitizers

Ionizing radiation is a common and effective therapeutic option for the treatment of glioblastoma (GBM). Unfortunately, some GBMs are relatively radioresistant and patients have worse outcomes after radiation treatment. The mechanisms underlying intrinsic radioresistance in GBM has been rigorously investigated over the past several years, but the complex interaction of the cellular molecules and signaling pathways involved in radioresistance remains incompletely defined. A clinically effective radiosensitizer that overcomes radioresistance has yet to be identified. In this review, we discuss the current status of radiation treatment in GBM, including advances in imaging techniques that have facilitated more accurate diagnosis, and the identified mechanisms of GBM radioresistance. In addition, we provide a summary of the candidate GBM radiosensitizers being investigated, including an update of subjects enrolled in clinical trials. Overall, this review highlights the importance of understanding the mechanisms of GBM radioresistance to facilitate the development of effective radiosensitizers.

Roles of the PI3K/AKT/mTOR signalling pathways in neurodegenerative diseases and tumours

The PI3 K/AKT/mTOR signalling pathway plays an important role in the regulation of signal transduction and biological processes such as cell proliferation, apoptosis, metabolism and angiogenesis. Compared with those of other signalling pathways, the components of the PI3K/AKT/mTOR signalling pathway are complicated. The regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway are important in many human diseases, including ischaemic brain injury, neurodegenerative diseases, and tumours. PI3K/AKT/mTOR signalling pathway inhibitors include single-component and dual inhibitors. Numerous PI3K inhibitors have exhibited good results in preclinical studies, and some have been clinically tested in haematologic malignancies and solid tumours. In this review, we briefly summarize the results of research on the PI3K/AKT/mTOR pathway and discuss the structural composition, activation, communication processes, regulatory mechanisms and biological functions of the PI3K/AKT/mTOR signalling pathway in the pathogenesis of neurodegenerative diseases and tumours.

MiR-214 Mediates Cell Proliferation and Apoptosis of Nasopharyngeal Carcinoma Through Targeting Both WWOX and PTEN

Background: This study aimed to investigate interactions between miR-214, PTEN, and WWOX and their effect on AKT signaling during the NPC progression. Nasopharyngeal carcinoma (NPC) was highly prevalent with poor prognosis among the patients. MiR-214 reported as an important NPC biomarker was associated with regulation of biological functions.

Methods: 5–8F and 6–10B NPC cells were transfected with miR-214 inhibitor. MTT and colony formation assays were performed to assess cell proliferation. PI staining assay was performed to determine distribution of cell cycle. Annexin-V/PI staining assay was used to evaluate cell apoptosis in NPC. The effects of miR-214 inhibitor on the expression levels of PTEN, WWOX, AKT signaling pathway, cell-cycle-, and apoptosis-associated proteins were assessed by Western blotting or qRT-PCR assay. PTEN and WWOX were knocked down using the corresponding shRNA to investigate their effects on miR-214 inhibitor involved in proapoptosis and antiproliferation mechanisms in NPC.

Results: Inhibition of miR-214 suppressed cell growth and induced apoptosis of 5–8F and 6–10B cells. MiR-214 regulated the expression of both PTEN and WWOX through targeting the 3′-UTR. Inhibition of miR-214 promoted WWOX and PTEN expression, inactivated AKT signaling pathway, and regulated cell-cycle- and apoptosis-associated proteins. Knockdown of PTEN or WWOX reversed effects of miR-214 inhibitor on AKT signaling, cell proliferation, and apoptosis.

Conclusion: MiR-214 was suggested to induce cell proliferation and inhibit cell apoptosis of NPC through directly targeting both PTEN and WWOX, which provided a novel therapeutic target for clinical treatment of NPC.

Exploration of Involved Key Genes and Signaling Diversity in Brain Tumors

Brain tumors are becoming a major cause of death. The classification of brain tumors has gone through restructuring with regard to some criteria such as the presence or absence of a specific genetic alteration in the 2016 central nervous system World Health Organization update. Two categories of genes with a leading role in tumorigenesis and cancer induction include tumor suppressor genes and oncogenes; tumor suppressor genes are inactivated through a variety of mechanisms that result in their loss of function. As for the oncogenes, overexpression and amplification are the most common mechanisms of alteration. Important cell cycle genes such as p53, ATM, cyclin D2, and Rb have shown altered expression patterns in different brain tumors such as meningioma and astrocytoma. Some genes in signaling pathways have a role in brain tumorigenesis. These pathways include hedgehog, EGFR, Notch, hippo, MAPK, PI3K/Akt, and WNT signaling. It has been shown that telomere length in some brain tumor samples is shortened compared to that in normal cells. As the shortening of telomere length triggers chromosome instability early in brain tumors, it could lead to initiation of cancer. On the other hand, telomerase activity was positive in some brain tumors. It is suggestive that telomere length and telomerase activity are important diagnostic markers in brain tumors. This review focuses on brain tumors with regard to the status of oncogenes, tumor suppressors, cell cycle genes, and genes in signaling pathways as well as the role of telomere length and telomerase in brain tumors.

Monitoring response to anti-angiogenic mTOR inhibitor therapy in vivo using 111In-bevacizumab

BACKGROUND

The ability to image vascular endothelial growth factor (VEGF) could enable prospective, non-invasive monitoring of patients receiving anti-angiogenic therapy. This study investigates the specificity and pharmacokinetics of 111In-bevacizumab binding to VEGF and its use for assessing response to anti-angiogenic therapy with rapamycin. Specificity of 111In-bevacizumab binding to VEGF was tested in vitro with unmodified radiolabelled bevacizumab in competitive inhibition assays. Uptake of 111In-bevacizumab in BALB/c nude mice bearing tumours with different amounts of VEGF expression was compared to that of isotype-matched control antibody (111In-IgG1κ) with an excess of unlabelled bevacizumab. Intratumoural VEGF was evaluated using ELISA and Western blot analysis. The effect of anti-angiogenesis therapy was tested by measuring tumour uptake of 111In-bevacizumab in comparison to 111In-IgG1κ following administration of rapamycin to mice bearing FaDu xenografts. Uptake was measured using gamma counting of ex vivo tumours and effect on vasculature by using anti-CD31 microscopy.

RESULTS

Specific uptake of 111In-bevacizumab in VEGF-expressing tumours was observed. Rapamycin led to tumour growth delay associated with increased relative vessel size (8.5 to 10.3, P = 0.045) and decreased mean relative vessel density (0.27 to 0.22, P = 0.0015). Rapamycin treatment increased tumour uptake of 111In-bevacizumab (68%) but not 111In-IgGκ and corresponded with increased intratumoural VEGF165.

CONCLUSIONS

111In-bevacizumab accumulates specifically in VEGF-expressing tumours, and changes after rapamycin therapy reflect changes in VEGF expression. Antagonism of mTOR may increase VEGF in vivo, and this new finding provides the basis to consider combination studies blocking both pathways and a way to monitor effects.

Correlation of NEDD4-1 and PTEN expression with the invasive capacity of pituitary adenomas

The aim of the present study was to correlate the expression of neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) with the invasive capacity of pituitary adenomas. A total of 50 pituitary adenoma tissues and 10 normal pituitary tissues were divided into the invasive group (26 cases), the non-invasive group (24 cases) and the normal group (10 cases). The expression of NEDD4-1 and PTEN was determined by immunohistochemistry. NEDD4-1 was revealed to be located in the nucleus and cytoplasm, whereas PTEN was only located in the cytoplasm. Furthermore, expression of NEDD4-1 was higher in pituitary adenomas compared with normal pituitary tissues (P<0.05), and higher in the invasive group compared with the non-invasive group, whereas the opposite trend was observed for PTEN. There was a strong negative correlation between NEDD4-1 and PTEN expression, indicating a dependency between the two and an association with invasiveness. In conclusion, NEDD4-1 may serve as a diagnostic and prognostic factor, and as a novel therapeutic target, in pituitary adenomas.

MicroRNA-20b (miR-20b) Promotes the Proliferation, Migration, Invasion, and Tumorigenicity in Esophageal Cancer Cells via the Regulation of Phosphatase and Tensin Homologue Expression

Increasing evidence has indicated that many microRNAs participate in the development and progression of esophageal cancer and gene expression regulation. MicroRNA-20b (miR-20b) has been reported to be aberrantly expressed in various cancers, but its exact role in esophageal cancer cells remains unclear so far. Therefore, we detected the levels of miR-20b in esophageal tumor tissues and their adjacent normal tissues, and various esophageal cancer cell lines by qRT-PCR. We also explored the effects of miR-20b on cell proliferation, migration, invasion and tumorigenicity of esophageal carcinoma cells through transfection with miR-20b mimics or inhibitor to upregulate or downregulate miR-20b expression in the esophageal cancer cells Eca-109 and KYSE-150, respectively. Additionally, the 3'-untranslated region (3'-UTR) of phosphatase and tensin homologue (PTEN) binding with miR-20b was analyzed by dual-luciferase reporter assays. The results indicated that miR-20b expression level in esophageal tumor tissues was significantly increased compared with their neighboring normal tissues, but its expression was inverse with PTEN protein expression. Luciferase assays confirmed that the 3'-UTR of PTEN was a target of miR-20b in esophageal cancer cells. MiR-20b upregulation promoted cell proliferation, migration, invasiveness, and tumor growth, and decreased apoptosis, and reduced PTEN protein level but not mRNA expression in Eca-109 cells. Conversely, downregulation of miR-20b suppressed these processes in KYSE-150 cells, and enhanced PTEN protein expression. These data indicate that miR-20b plays important roles in tumorigenesis of esophageal cancer possibly via regulation of PTEN expression, and it may be a potential therapeutic target for esophageal cancer treatment.

Discovery of Chromeno[4,3-c]pyrazol-4(2H)-one Containing Carbonyl or Oxime Derivatives as Potential, Selective Inhibitors PI3Kα

A series of novel chromeno[4,3-c]pyrazol-4(2H)-one containing carbonyl or oxime derivatives (4a-n, 5a-n) have been synthesized and evaluated their biological activities as phosphatidyl inositol 3-kinase (PI3K) inhibitors. Out of them, compound 5l showed the most potent antiproliferative activities against HCT-116 with IC₅₀ of 0.10 µM in vitro, and exhibited the most potent activity for PI3Kα with the value of 0.012 µM. Docking simulation of 5l into PI3Kα active site were performed to determine the probable binding model, and it indicated that compound 5l could be optimized as a potential inhibitor of PI3Kα in the further study.

Targeting annexin A2 reduces tumorigenesis and therapeutic resistance of nasopharyngeal carcinoma

The expression of annexin A2 (ANXA2) in nasopharyngeal carcinoma (NPC) cells induces the immunosuppressive response in dendritic cells; however, the oncogenic effect and clinical significance of ANXA2 have not been fully investigated in NPC cells. Immunohistochemical staining for ANXA2 was performed in 61 patients and the association with clinicopathological status was determined. Short hairpin (sh)RNA knockdown of ANXA2 was used to examine cellular effects of ANXA2, by investigating alterations in cell proliferation, migration, invasion, adhesion, tube-formation assay, and chemo- and radiosensitivity assays were performed. RT-qPCR, Western blotting, and immunofluorescence were applied to determine molecular expression levels. Clinical association studies showed that the expression of ANXA2 was significantly correlated with metastasis (p = 0.0326) and poor survival (p = 0.0256). Silencing of ANXA2 suppressed the abilities of cell proliferation, adhesion, migration, invasion, and vascular formation in NPC cell. ANXA2 up-regulated epithelial-mesenchymal transition associated signal proteins. Moreover, ANXA2 reduced sensitivities to irradiation and chemotherapeutic drugs. These results define ANXA2 as a novel prognostic factor for malignant processes, and it can serve as a molecular target of therapeutic interventions for NPC.

MiR-454 promotes the progression of human non-small cell lung cancer and directly targets PTEN

PURPOSE

MicroRNA-454 has been proven dysregulated in some human malignancies and correlated with tumor progression. However, its expression and function in non-small cell lung cancer (NSCLC) is still unclear. Thus, the aim of this study was to explore the effects of miR-454 in NSCLC tumorigenesis and development.

METHODS

Using quantitative RT-PCR, we detected miR-454 expression in NSCLC cell lines and primary tumor tissues. The association of miR-454 expression with clinicopathological factors and prognosis was also analyzed. Then, the effects of miR-454 on the biological behavior of NSCLC cells were investigated. At last, the potential regulatory function of miR-454 on PTEN expression was confirmed.

RESULTS

miR-454 was found to be up-regulated in NSCLC tissues and cell lines. High miR-454 expression was closely correlated with lymph node metastasis, advanced TNM stage, and shorter overall survival. Multivariate regression analysis corroborated that miR-454 overexpression was an independent unfavourable prognostic factor for patients with NSCLC. Down-regulation of miR-454 could significantly reduce NSCLC cell proliferation, enhance cell apoptosis, and impair cell invasion and migration in vitro, while up-regulation of miR-454 showed opposite effects. Further, PTEN was confirmed as a direct target of miR-454 by using Luciferase Reporter Assay.

CONCLUSIONS

These findings indicate that miR-454 may act as an oncogene in NSCLC and would serve as a potential therapy target for this disease.

Relevance of miR-21 in regulation of tumor suppressor gene PTEN in human cervical cancer cells

BACKGROUND

Expression of the microRNA miR-21 has been found to be altered in almost all types of cancers and it has been classified as an oncogenic microRNA or oncomir. Due to the critical functions of its target proteins in various signaling pathways, miR-21 is an attractive target for genetic and pharmacological modulation in various cancers. Cervical cancer is the second most common cause of death from cancer in women worldwide and persistent HPV infection is the main etiologic agent. This malignancy merits special attention for the development of new treatment strategies. In the present study we analyze the role of miR-21 in cervical cancer cells.

METHODS

To identify the downstream cellular target genes of upstream miR-21, we silenced endogenous miR-21 expression in a cervical intraepithelial neoplasia-derived cell lines using siRNAs. The effect of miR-21 on gene expression was assessed in cervical cancer cells transfected with the siRNA expression plasmid pSIMIR21. We identified the tumor suppressor gene PTEN as a target of miR-21 and determined the mechanism of its regulation throughout reporter construct plasmids. Using this model, we analyzed the expression of miR-21 and PTEN as well as functional effects such as autophagy and apoptosis induction.

RESULTS

In SiHa cells, there was an inverse correlation between miR-21 expression and PTEN mRNA level as well as PTEN protein expression in cervical cancer cells. Transfection with the pSIMIR21 plasmid increased luciferase reporter activity in construct plasmids containing the PTEN-3'-UTR microRNA response elements MRE21-1 and MRE21-2. The role of miR-21 in cell proliferation was also analyzed in SiHa and HeLa cells transfected with the pSIMIR21 plasmid, and tumor cells exhibited markedly reduced cell proliferation along with autophagy and apoptosis induction.

CONCLUSIONS

We conclude that miR-21 post-transcriptionally down-regulates the expression of PTEN to promote cell proliferation and cervical cancer cell survival. Therefore, it may be a potential therapeutic target in gene therapy for cervical cancer.

EB-virus latent membrane protein 1 potentiates the stemness of nasopharyngeal carcinoma via preferential activation of PI3K/AKT pathway by a positive feedback loop

Our previous study reported that Epstein-Barr virus(EBV)-encoded latent membrane protein 1 (LMP1) could induce development of CD44(+/High) stem-like cells in nasopharyngeal carcinoma (NPC). However, the molecular mechanisms that underlie modulation of cancer stem cells (CSCs) in NPC remain unclear. Here, we show that LMP1 induced CSC-like properties through promotion of the expression of epithelial-mesenchymal transition-like cellular markers and through alterations in differentiation markers. Furthermore, LMP1 activated and triggered phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway, which subsequently stimulated expression of CSC markers, development of side population and tumor sphere formation. This suggests that PI3K/AKT pathway has an important role in the induction and maintenance of CSC properties in NPC. Similarly, PI3K/AKT pathway was also activated by phosphorylase in LMP1-induced CD44(+/High) cells. In addition, LMP1 greatly increased expression of miR-21 and downregulated expression of the miR-21 target, PTEN. Overexpression of miR-21 by transfection of miR-21 mimics into LMP1-transformed cells led to phosphorylase-mediated activation of the PI3K/AKT pathway and induction of CSCs. On the contrary, phosphorylation of the PI3K/AKT pathway and the expression of CSC were reversed by an miR-21 inhibitor. The specific inhibitor (Ly294002) of PI3K/AKT pathway significantly decreased expression of miR-21 and CSC markers and upregulated the expression of PTEN, which indicates that miR-21 and PTEN are the downstream effectors of PI3K/AKT and that expression of these two effectors are related to the development of NPC CSCs. Taken together, our novel findings indicate that LMP1, PI3K/AKT, miR-21 and PTEN constitute a positive feedback loop and have a key role in LMP1-induced CSCs in NPC.

Not so Fast: Co-Requirements for Sonic Hedgehog Induced Brain Tumorigenesis

The Sonic hedgehog (Shh) pathway plays an integral role in cellular proliferation during normal brain development and also drives growth in a variety of cancers including brain cancer. Clinical trials of Shh pathway inhibitors for brain tumors have yielded disappointing results, indicating a more nuanced role for Shh signaling. We postulate that Shh signaling does not work alone but requires co-activation of other signaling pathways for tumorigenesis and stem cell maintenance. This review will focus on the interplay between the Shh pathway and these pathways to promote tumor growth in brain tumors, presenting opportunities for the study of combinatorial therapies.

Chronic Dietary Administration of the Glycolytic Inhibitor 2-Deoxy-D-Glucose (2-DG) Inhibits the Growth of Implanted Ehrlich's Ascites Tumor in Mice

Background

Dietary energy restriction (DER) has been well established as a potent anticancer strategy. Non-adoption of restricted diet for an extended period has limited its practical implementation in humans with a compelling need to develop agents that mimic effects similar to DER, without reduction in actual dietary intake. Glycolytic inhibitor, 2-deoxy-D-glucose (2-DG), has recently been shown to possess potential as an energy restriction mimetic agent (ERMA). In the present study we evaluated the effect of dietary 2-DG administration on a mouse tumor model, with a focus on several potential mechanisms that may account for the inhibition of tumorigenesis.

Methodology/Principal Findings

Swiss albino strain ‘A’ mice were administered with 0.2% and 0.4% w/v 2-DG in drinking water for 3 months prior to tumor implantation (Ehrlich’s ascites carcinoma; EAC) and continued till the termination of the study with no adverse effects on general physiology and animal growth. Dietary 2-DG significantly reduced the tumor incidence, delayed the onset, and compromised the tumor growth along with enhanced survival. We observed reduced blood glucose and serum insulin levels along with decreased proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine positive (BrdU⁺) tumor cells in 2-DG fed mice. Also, reduced levels of certain key players of metabolic pathways such as phosphatidylinositol 3-kinase (PI3K), phosphorylated-Akt and hypoxia inducible factor-1 alpha (HIF-1α) were also noted in tumors of 2-DG fed mice. Further, decrease in CD4⁺/CD8⁺ ratio and T-regulatory cells observed in 2-DG fed mice suggested enhanced antitumor immunity and T cell effector function.

Conclusion/Significance

These results strongly suggest that dietary 2-DG administration in mice, at doses easily achievable in humans, suitably modulates several pleotrophic factors mimicking DER and inhibits tumorigenesis, emphasizing the use of ERMAs as a promising cancer preventive strategy.

Activation of PI3Kγ/Akt pathway mediates bone cancer pain in rats

Bone cancer pain (BCP) is one of the most common and severe complications in patients suffering from primary bone cancer or metastatic bone cancer such as breast, prostate, or lung, which profoundly compromises their quality of life. Emerging lines of evidence indicate that central sensitization is required for the development and maintenance of BCP. However, the underlying mechanisms are largely unknown. In this study, we investigated the role of PI3Kγ/Akt in the central sensitization in rats with tumor cell implantation in the tibia, a widely used model of BCP. Our results showed that PI3Kγ and its downstream target pAkt were up-regulated in a time-dependent manner and distributed predominately in the superficial layers of the spinal dorsal horn neurons, astrocytes and a minority of microglia, and were colocalized with non-peptidergic, calcitonin gene-related peptide-peptidergic, and A-type neurons in dorsal root ganglion ipsilateral to tumor cell inoculation in rats. Inhibition of spinal PI3Kγ suppressed BCP-associated behaviors and the up-regulation of pAkt in the spinal cord and dorsal root ganglion. This study suggests that PI3Kγ/Akt signal pathway mediates BCP in rats. Central sensitization is required for the development and maintenance of bone cancer pain (BCP). In this study, we reported that PI3Kγ/Akt mediated the function of ephrinBs/EphBs in the central sensitization under BCP condition, and inhibition of spinal PI3Kγ suppressed BCP-associated behaviors. Our results suggest that inhibition of PI3Kγ/Akt may be a new target for the treatment of BCP.

Nanomedicine to overcome radioresistance in glioblastoma stem-like cells and surviving clones

Radiotherapy is one of the standard treatments for glioblastoma, but its effectiveness often encounters the phenomenon of radioresistance. This resistance was recently attributed to distinct cell contingents known as glioblastoma stem-like cells (GSCs) and dominant clones. It is characterized in particular by the activation of signaling pathways and DNA repair mechanisms. Recent advances in the field of nanomedicine offer new possibilities for radiosensitizing these cell populations. Several strategies have been developed in this direction, the first consisting of encapsulating a contrast agent or synthesizing metal-based nanocarriers to concentrate the dose gradient at the level of the target tissue. In the second strategy the physicochemical properties of the vectors are used to encapsulate a wide range of pharmacological agents which act in synergy with the ionizing radiation to destroy the cancerous cells. This review reports on the various molecular anomalies present in GSCs and the predominant role of nanomedicines in the development of radiosensitization strategies.

Activation of miR-21 by STAT3 induces proliferation and suppresses apoptosis in nasopharyngeal carcinoma by targeting PTEN gene

The present study is to investigate the role of microRNA-21 (miR-21) in nasopharyngeal carcinoma (NPC) and the mechanisms of regulation of PTEN by miR-21. Fifty-four tissue samples were collected from 42 patients with NPC and 12 healthy controls. Human NPC cell lines CNE-1, CNE-2, TWO3 and C666-1 were used for cell assays. To investigate the expression of miR-21, RT-PCR was employed. RT-PCR, Western blotting, and immunohistochemistry were used to measure the expression of STAT3 mRNA and STAT3 protein. To test the effect of miR-21 on the cell growth and apoptosis of NPC cells in vitro, transfection of CNE1 and CNE2 cell lines and flow cytometry were performed. TUNEL assay was used to detect DNA fragmentation. To validate whether miR-21 directly recognizes the 3'-UTRs of PTEN mRNA, luciferase reporter assay was employed. miR-21 expression was increased in NPC tissues compared with control and the same result was found in NPC cell lines. Notably, increased expression of miR-21 was directly related to advanced clinical stage and lymph node metastasis. STAT3, a transcription factor activated by IL-6, directly activated miR-21 in transformed NPC cell lines. Furthermore, miR-21 markedly inhibited PTEN tumor suppressor, leading to increased AKT activity. Both in vitro and in vivo assays revealed that miR-21 enhanced NPC cell proliferation and suppressed apoptosis. miR-21, activated by STAT3, induced proliferation and suppressed apoptosis in NPC by targeting PTEN-AKT pathway.

miR‑494 is an independent prognostic factor and promotes cell migration and invasion in colorectal cancer by directly targeting PTEN

Accumulating evidence has shown that micro-RNAs (miRNAs) are involved in multiple processes in cancer development and progression. Upregulation of miRNA-494 (miR-494) has been identified as an oncogenic miRNA and is associated with poor prognosis in several types of human cancer. However, the specific function of miR-494 in colorectal cancer remains unclear. In this study we found that the expression of miR-494 in colorectal cancer tissues and cell lines was much higher than in normal control tissues and cells, respectively. In addition, upregulation of miR-494 more frequently occurred in tissue specimens with adverse clinical stage and the presence of distant metastasis. Moreover, multivariate survival analyses demonstrated that overexpression of miR-494 is an independent prognostic factor for both progression-free and overall survival. In addition miR-494 promoted invasion and migration in colorectal cancer cells, and miR-494 directly inhibited the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression by targeting its 3'-untranslated region (3'-UTR). Moreover, PTEN is down regulated and inversely correlated with miR-494 expression in tissues. Thus, for the first time, we provided convincing evidence that upregulation of miR-494 was associated with tumor aggressiveness and tumor metastasis and promoted cell migration and invasion by targeting PTEN gene in colorectal cancer, and miR-494 is an independent prognostic marker for colorectal cancer patients.

Effect of saw palmetto extract on PI3K cell signaling transduction in human glioma

Saw palmetto extract can induce the apoptosis of prostate cancer cells. The aim of the present study was to investigate the effect of saw palmetto extract on the phosphatidylinositol 3-kinase (PI3K)/Akt signaling transduction pathway in human glioma U87 and U251 cell lines. Suspensions of U87 and U251 cells in a logarithmic growth phase were seeded into six-well plates at a density of 10⁴ cells/well. In the experimental group, 1 μl/ml saw palmetto extract was added, while the control group was cultured without a drug for 24 h. The expression levels of PI3K, B-cell lymphoma-extra large (Bcl-xL) and p53 were evaluated through western blot analysis. In the experimental group, the U87 and U251 cells exhibited a lower expression level of PI3K protein as compared with the control group (t=6.849; P<0.001). In addition, the two cell lines had a higher expression level of p53 protein in the experimental group as compared with the control group (t=40.810; P<0.001). Protein expression levels of Bcl-xL decreased significantly in the experimental group as compared with the control group (t=19.640; P=0.000). Therefore, saw palmetto extract induces glioma cell growth arrest and apoptosis via decreasing PI3K/Akt signal transduction.

C-reactive protein inhibits survivin expression via Akt/mTOR pathway downregulation by PTEN expression in cardiac myocytes

C-reactive protein (CRP) is one of the most important biomarkers for arteriosclerosis and cardiovascular disease. Recent studies have shown that CRP affects cell cycle and inflammatory process in cardiac myocytes. Survivin is also involved in cardiac myocytes replication and apoptosis. Reduction of survivin expression is associated with less favorable cardiac remodeling in animal models. However, the effect of CRP on survivin expression and its cellular mechanism has not yet been studied. We demonstrated that treatment of CRP resulted in a significant decrease of survivin protein expression in a concentration-dependent manner in cardiac myocytes. The upstream signaling proteins of survivin, such as Akt, mTOR and p70S6K, were also downregulated by CRP treatment. In addition, CRP increased the protein and mRNA levels of PTEN. The siRNA transfection or specific inhibitor treatment for PTEN restored the CRP-induced downregulation of Akt/mTOR/p70S6K pathway and survivin protein expression. Moreover, pretreatment with a specific p53 inhibitor decreased the CRP-induced PTEN expression. ERK-specific inhibitor also blocked the p53 phosphorylation and PTEN expression induced by CRP. Our study provides a novel insight into CRP-induced downregulation of survivin protein expression in cardiac myocytes through mechanisms that involved in downregulation of Akt/mTOR/p70S6K pathway by expression of PTEN.

Activation of spinal phosphatidylinositol 3-kinase/protein kinase B mediates pain behavior induced by plantar incision in mice

The etiology of postoperative pain may be different from antigen-induced inflammatory pain and neuropathic pain. However, central neural plasticity plays a key role in incision pain. It is also known that phosphatidylinositol 3-kinase (PI3K) and protein kinase B/Akt (PKB/Akt) are widely expressed in laminae I-IV of the spinal horn and play a critical role in spinal central sensitization. In the present study, we explored the role of PI3K and Akt in incision pain behaviors. Plantar incision induced a time-dependent activation of spinal PI3K-p110γ and Akt, while activated Akt and PI3K-p110γ were localized in spinal neurons or microglias, but not in astrocytes. Pre-treatment with PI3K inhibitors, wortmannin or LY294002 prevented the activation of Akt brought on by plantar incision in a dose-dependent manner. In addition, inhibition of spinal PI3K signaling pathway prevented pain behaviors (dose-dependent) and spinal Fos protein expression caused by plantar incision. These data demonstrated that PI3K signaling mediated pain behaviors caused by plantar incision in mice.

miR-17 inhibitor suppressed osteosarcoma tumor growth and metastasis via increasing PTEN expression

MicroRNAs (miRNAs) play essential roles in cancer development and progression. Here, we investigated the role of miR-17 in the progression and metastasis of osteosarcoma (OS). miR-17 was frequently increased in OS tissues and cell lines. Inhibition of miR-17 in OS cell lines substantially suppressed cell proliferation, migration, and invasion. Phosphatase and tensin homolog (PTEN) was identified as a target of miR-17, and ectopic expression of miR-17 inhibited PTEN by direct binding to its 3'-untranslated region (3'-UTR). Expression of miR-17 was negatively correlated with PTEN in OS tissues. Together, these findings indicate that miR-17 acts as an oncogenic miRNA and may contribute to the progression and metastasis of OS, suggesting miR-17 as a potential novel diagnostic and therapeutic target of OS.

MicroRNA-92a functions as an oncogene in colorectal cancer by targeting PTEN

BACKGROUND

Our previous studies show that microRNA-92a (miR-92a) is overexpressed in colorectal cancer (CRC) and is thought to be correlated with the development of the cancer. However, its biological role in CRC remains poorly understood.

AIMS

The aim of the study was to determine the role of miR-92a and to elucidate its regulatory mechanism in CRC.

METHODS

The expression levels of miR-92a and phosphatase and tensin homologue (PTEN) were detected by qRT-PCR and western blot. MTT, migration and invasion assays were used to examine the proliferation, migration and invasion of pre-miR-92a transfected SW480 cells, and a mouse model was used to investigate tumorigenesis. In addition, the regulation of PTEN by miR-92a was evaluated by qRT-PCR, western blot and luciferase reporter assays.

RESULTS

The expression of miR-92a was significantly up-regulated in the tissues of CRC patients with lymph node metastasis. The ectopic expression of miR-92a enhanced CRC cell proliferation, migration and invasion. Similar results were found in xenograft assay performed in nude mice. Up-regulation of miR-92a induced EMT in CRC cells. There was an inverse correlation between the levels of miR-92a and PTEN in CRC tissues. The overexpression of miR-92a in CRC cells decreased PTEN expression at the translational level, and decreased PTEN-driven luciferase-reporter activity.

CONCLUSIONS

Our results demonstrated that miR-92a induced EMT and regulated cell growth, migration and invasion in the SW480 cells, at least partially, via suppression of PTEN expression. MiR-92a may serve as a novel therapeutic target in colorectal cancer.

Down-regulation of PTEN expression modulated by dysregulated miR-21 contributes to the progression of esophageal cancer

BACKGROUND AND AIM

miR-21, a putative tumor oncomiR, is a frequently overexpressed miRNA in a variety of tumors. Because it targets tumor-suppressor genes it has been linked to tumor progression. In this study we investigated the role of miR-21 in esophageal squamous cell carcinoma (ESCC), and its possible mechanism.

METHODS

Expression of miR-21 was detected by stem-loop RT-PCR in tissue from 76 invasive ESCC at stage I-IV and in their corresponding para-cancerous histological normal tissues (PCHNT). Thirty endoscopic esophageal mucosal biopsy specimens from non-tumor patients were used as controls. Expression of PTEN in 76 paired ESCC and PCHNT was investigated by real-time RT-PCR and an immunohistochemical method, respectively. Paired tumor and PCHNT specimens of 20 ESCC cases were randomly selected for western blot analysis. The effect of miR-21 on PTEN expression was assessed in the ESCC cell line with an miR-21 inhibitor to reduce miR-21 expression. Furthermore, the roles of miR-21 in cell biology were analyzed by use of miR-21 inhibitor-transfected cells.

RESULTS

Stem-loop RT-PCR revealed miR-21 was significantly overexpressed in ESCC tissues and cell lines. Overexpression of miR-21 correlated with tumor status, lymph node metastasis, and clinical stage. We demonstrated that knockdown of miR-21 significantly increased expression of PTEN protein. Consequent PTEN expression reduced cell proliferation, invasion, and migration.

CONCLUSIONS

Our findings suggest that miR-21 could be a potential oncomiR, probably by regulation of PTEN, and a novel prognostic factor for ESCC patients.

MiR-214 regulate gastric cancer cell proliferation, migration and invasion by targeting PTEN

Background

MicroRNAs are a class of small non-coding RNAs that play an important role in various human tumor initiation and progression by regulating gene expression negatively. The aim of this study was to investigate the effect of miR-214 on cell proliferation, migration and invasion, as well as the functional connection between miR-214 and PTEN in gastric cancer.

Methods

miR-214 and PTEN expression was determined in gastric cancer and matched normal tissues, and human gastric cancer cell lines by quantitative real-time PCR. The roles of miR-214 in cell proliferation, migration and invasion were analyzed with anti-miR-214 transfected cells. In addition, the regulation of PTEN by miR-214 was evaluated by Western blotting and luciferase reporter assays.

Results

miR-214 was noted to be highly overexpressed in gastric cancer tissues and cell lines using qRT-PCR. The expression level of miR-214 is significantly associated with clinical progression and poor prognosis according to the analysis of the clinicopathologic data. We also found that the miR-214 levels are inversely correlated with PTEN in tumor tissues. And PTEN expression level is also associated with metastasis and invasion of gastric cancer. In addition, knockdown of miR-214 could significantly inhibit proliferation, migration and invasion of gastric cancer cells. Moreover, we demonstrate that PTEN is regulated negatively by miR-214 through a miR-214 binding site within the 3’-UTR of PTEN at the posttranscriptional level in gastric cancer cells.

Conclusions

These findings indicated that miR-214 regulated the proliferation, migration and invasion by targeting PTEN post-transcriptionally in gastric cancer. It may be a novel potential therapeutic agent for gastric cancer.

Cannabinoids inhibit energetic metabolism and induce AMPK-dependent autophagy in pancreatic cancer cells

The anti-tumoral effects of cannabinoids have been described in different tumor systems, including pancreatic adenocarcinoma, but their mechanism of action remains unclear. We used cannabinoids specific for the CB1 (ACPA) and CB2 (GW) receptors and metabolomic analyses to unravel the potential pathways mediating cannabinoid-dependent inhibition of pancreatic cancer cell growth. Panc1 cells treated with cannabinoids show elevated AMPK activation induced by a ROS-dependent increase of AMP/ATP ratio. ROS promote nuclear translocation of GAPDH, which is further amplified by AMPK, thereby attenuating glycolysis. Furthermore, ROS determine the accumulation of NADH, suggestive of a blockage in the respiratory chain, which in turn inhibits the Krebs cycle. Concomitantly, inhibition of Akt/c-Myc pathway leads to decreased activity of both the pyruvate kinase isoform M2 (PKM2), further downregulating glycolysis, and glutamine uptake. Altogether, these alterations of pancreatic cancer cell metabolism mediated by cannabinoids result in a strong induction of autophagy and in the inhibition of cell growth.

MicroRNA-32 (miR-32) regulates phosphatase and tensin homologue (PTEN) expression and promotes growth, migration, and invasion in colorectal carcinoma cells

Background

Colorectal carcinoma (CRC) is one of the leading causes of cancer-related mortality worldwide. MicroRNAs (miRNAs, miRs) play important roles in carcinogenesis. MiR-32 has been shown to be upregulated in CRC. In this study, we identified the potential effects of miR-32 on some important biological properties of CRC cells, and clarified the regulation of PTEN by miR-32.

Methods

The effect of miR-32 on PTEN expression was assessed in CRC cell lines with miR-32 mimics/inhibitor to increase/decrease miR-32 expression. Furthermore, the roles of miR-32 in regulating CRC cells biological properties were analyzed with miR-32 mimics/inhibitor-transfected cells. The 3^′-untranslated region (3^′-UTR) of PTEN combined with miR-32 was verified by dual-luciferase reporter assay.

Results

Gain-of-function and loss-of-function studies showed that overexpression of miR-32 promoted SW480 cell proliferation, migration, and invasion, reduced apoptosis, and resulted in downregulation of PTEN at a posttranscriptional level. However, miR-32 knock-down inhibited these processes in HCT-116 cells and enhanced the expression of PTEN protein. In addition, we further identified PTEN as the functional downstream target of miR-32 by directly targeting the 3^′-UTR of PTEN.

Conclusions

Our results demonstrated that miR-32 was involved in tumorigenesis of CRC at least in part by suppression of PTEN.

Dopamine D2 receptor-mediated Akt/PKB signalling: initiation by the D2S receptor and role in quinpirole-induced behavioural activation

The short and long isoforms of the dopamine D2 receptor (D2S and D2L respectively) are highly expressed in the striatum. Functional D2 receptors activate an intracellular signalling pathway that includes a cAMP-independent route involving Akt/GSK3 (glycogen synthase kinase 3). To investigate the Akt/GSK3 response to the seldom-studied D2S receptor, we established a rat D2S receptor-expressing cell line [HEK (human embryonic kidney)-293/rD2S]. We found that in HEK-293/rD2S cells, the D2/D3 agonists bromocriptine and quinpirole significantly induced Akt and GSK3 phosphorylation, as well as ERK1/2 (extracellular-signal-regulated kinase 1/2) activation. The D2S receptor-induced Akt signals were profoundly inhibited by the internalization blockers monodansyl cadaverine and concanavalin A. Activation of the D2S receptor in HEK-293/rD2S cells appeared to trigger Akt/phospho-Akt translocation to the cell membrane. In addition to our cell culture experiments, we studied D2 receptor-dependent Akt in vivo by systemic administration of the D2/D3 agonist quinpirole. The results show that quinpirole evoked Akt-Ser⁴⁷³ phosphorylation in the ventral striatum. Furthermore, intra-accumbens administration of wortmannin, a PI3K (phosphoinositide 3-kinase) inhibitor, significantly suppressed the quinpirole-evoked behavioural activation. Overall, we demonstrate that activation of the dopamine D2S receptor stimulates Akt/GSK3 signalling. In addition, in vivo Akt activity in the ventral striatum appears to play an important role in systemic D2/D3 agonist-induced behavioural activation.

Multifaceted roles of PTEN and TSC orchestrate growth and differentiation of Drosophila blood progenitors

The innate plasticity of hematopoietic progenitors is tightly regulated to supply blood cells during normal hematopoiesis and in response to stress or infection. We demonstrate that in the Drosophila lymph gland (LG) the tumor suppressors TSC and PTEN control blood progenitor proliferation through a common TOR- and 4EBP-dependent pathway. Tsc2 or Pten deficiency in progenitors increases TOR signaling and causes LG overgrowth by increasing the number of actively dividing cells that accumulate high levels of phosphorylated (p) 4EBP during a critical window of growth. These phenotypes are associated with increased reactive oxygen species (ROS) levels in the LG, and scavenging ROS in progenitors is sufficient to rescue overgrowth. Blood progenitor number is also sensitive to starvation and hypoxia in a TOR-dependent manner. Differences between Tsc1/2 and Pten function become apparent at later stages. Loss of Tsc1/2 autonomously increases p4EBP and decreases pAKT levels, expands the number of intermediate progenitors and limits terminal differentiation, except for a late induction of lamellocytes. By contrast, absence of PTEN increases p4EBP and pAKT levels and induces myeloproliferative expansion of plasmatocytes and crystal cells. This increased malignancy is associated with non-autonomous increases in p4EBP levels within peripheral differentiating hemocytes, culminating in their premature release into circulation and demonstrating potential non-autonomous effects of Pten dysfunction on malignancy. This study highlights mechanistic differences between TSC and PTEN on TOR function and demonstrates the multifaceted roles of a nutrient-sensing pathway in orchestrating proliferation and differentiation of myeloid-specific blood progenitors through regulation of ROS levels and the resulting myeloproliferative disorder when dysregulated.

PI3K contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs

There is accumulating evidence to implicate the importance of EphBs receptors and ephrinBs ligands were involved in modulation of spinal nociceptive information. However, the downstream mechanisms that control this process are not well understood. In the present study, we investigated whether phosphatidylinositol 3-kinase (PI3K), as the downstream effectors, participates in modulation of spinal nociceptive information related to ephrinBs/EphBs. Intrathecal injection of ephrinB1-Fc produced a dose- and time-dependent thermal and mechanical hyperalgesia, accompanied by the increase of spinal PI3K-p110γ, phosphorylation of AKT (p-AKT) and c-Fos expression. Pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented activation of spinal AKT induced by ephrinB1-Fc. Inhibition of spinal PI3K signaling dose-dependently prevented and reversed pain behaviors and spinal c-Fos protein expression induced by intrathecal injection of ephrinB1-Fc. Inhibition of EphBs receptors by intrathecal injection of EphB1-Fc reduced formalin-induced inflammation and chronic constrictive injury-induced neuropathic pain behaviors accompanied by decreased expression of spinal PI3K,p-AKT and c-Fos protein. Furthermore, pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented ephrinB1-Fc-induced ERK activation in spinal. These data demonstrated that PI3K and PI3K crosstalk to ERK signaling contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs.

Targeting the PI3K/mTOR axis, alone and in combination with autophagy blockade, for the treatment of malignant peripheral nerve sheath tumors

There is a critical need for efficacious therapeutic strategies to improve the outcome of patients afflicted by malignant peripheral nerve sheath tumors (MPNST). Multiple lines of evidence suggest a role for deregulated phosphoinositide 3-kinase (PI3K)/mTOR signaling in MPNST, making this axis an attractive target for therapeutic manipulation. On the basis of previous observations obtained from in vitro experimentation, here we aimed to assess the effects of PI3K/mTOR blockade on MPNST growth in vivo. The anti-MPNST impact of XL765, a dual PI3K/mTOR inhibitor currently being evaluated in human cancer clinical trials, was tested in two human MPNST xenograft models (STS26T and MPNST724) and an experimental model of pulmonary metastasis (STS26T). XL765 abrogated human MPNST local and metastatic growth in severe combined immunodeficient mice. Notably, this therapeutic approach failed to induce apoptosis in MPNST cells but rather resulted in marked productive autophagy. Importantly, genetic and pharmacologic autophagy blockade reversed apoptotic resistance and resulted in significant PI3K/mTOR inhibition-induced MPNST cell death. The addition of the autophagy inhibitor, chloroquine, to the therapeutic regimen of MPNST xenografts after pretreatment with XL765 resulted in superior antitumor effects as compared with either agent alone. Together, preclinical studies described here expand our previous findings and suggest that PI3K/mTOR inhibition alone and (most importantly) in combination with autophagy blockade may comprise a novel and efficacious therapy for patients harboring MPNST.

Antiangiogenic therapy for glioma

Currently, antiangiogenic agents are routinely used for the treatment of patients with glioma. However, despite advances in pharmacological and surgical therapy, glioma remains an incurable disease. Indeed, the formation of an abnormal tumor vasculature and the invasion of glioma cells along neuronal tracts are proposed to comprise the major factors that are attributed to the therapeutic resistance of these tumors. The development of curative therapeutic modalities for the treatment of glioma requires further investigation of the molecular mechanisms regulating angiogenesis and invasion. In this review, we discuss the molecular characteristics of angiogenesis and invasion in human malignant glioma, we present several available drugs that are used or can potentially be utilized for the inhibition of angiogenesis in glioma, and we focus our attention on the key mediators of the molecular mechanisms underlying the resistance of glioma to antiangiogenic therapy.