Downregulation of PIK3CB by siRNA suppresses malignant glioma cell growth in vitro and in vivo

Selective regulation of chemosensitivity in glioblastoma by phosphatidylinositol 3-kinase beta

Resistance to chemotherapies such as temozolomide is a major hurdle to effectively treat therapy-resistant glioblastoma. This challenge arises from the activation of phosphatidylinositol 3-kinase (PI3K), which makes it an appealing therapeutic target. However, non-selectively blocking PI3K kinases PI3Kα/β/δ/γ has yielded undesired clinical outcomes. It is, therefore, imperative to investigate individual kinases in glioblastoma's chemosensitivity. Here, we report that PI3K kinases were unequally expressed in glioblastoma, with levels of PI3Kβ being the highest. Patients deficient of O6-methylguanine-DNA-methyltransferase (MGMT) and expressing elevated levels of PI3Kβ, defined as MGMT-deficient/PI3Kβ-high, were less responsive to temozolomide and experienced poor prognosis. Consistently, MGMT-deficient/PI3Kβ-high glioblastoma cells were resistant to temozolomide. Perturbation of PI3Kβ, but not other kinases, sensitized MGMT-deficient/PI3Kβ-high glioblastoma cells or tumors to temozolomide. Moreover, PI3Kβ-selective inhibitors and temozolomide synergistically mitigated the growth of glioblastoma stem cells. Our results have demonstrated an essential role of PI3Kβ in chemoresistance, making PI3Kβ-selective blockade an effective chemosensitizer for glioblastoma.

Apigenin and Temozolomide Synergistically Inhibit Glioma Growth Through the PI3K/AKT Pathway

Background: Glioma is a devastating disease with the worst prognosis among human malignant tumors. Although temozolomide (TMZ) improves the overall survival of glioma patients, there are still many glioma patients who are resistant to TMZ. In this study, we focused on the effect of apigenin (API) and TMZ on glioma cells in vitro and in vivo, and we studied the underlying molecular mechanisms. Materials and Methods: To investigate the effect of API on glioblastoma cell proliferation, cell viability was assessed after glioma cells were incubated with various concentrations of API with or without TMZ using MTT assays. Then, we explored the synergistic effect of API and TMZ on glioma cell cycle, apoptosis, and migration. To investigate the molecular mechanism behind the synergism of API and TMZ, we examined the related genes of the major signaling pathways involved in glioma pathogenesis by Western blotting. Results: In this study, we found that API significantly suppressed the proliferation of glioma cells in a dose- and time-dependent manner. Combining API and TMZ significantly induced glioma cells arrest at the G2 phase and inhibited glioma cells proliferation compared with API or TMZ alone. In addition, API promoted the ability of TMZ to induce glioma cells apoptosis and inhibit glioma cells invasion. Furthermore, compared with treatment with individual agents, the combination of API and TMZ significantly inhibited the growth of subcutaneous tumors in mice. These results implied that API could synergistically suppress the growth of glioma cells when combined with TMZ. Combining API and TMZ significantly inhibited the protein expression of p-AKT, cyclin D1, Bcl-2, Matrix Metallopeptidase 2, and Matrix Metallopeptidase 9. Conclusion: API and TMZ synergistically inhibited glioma growth through the PI3K/AKT pathway.

Nucleic acid drug vectors for diagnosis and treatment of brain diseases

Nucleic acid drugs have the advantages of rich target selection, simple in design, good and enduring effect. They have been demonstrated to have irreplaceable superiority in brain disease treatment, while vectors are a decisive factor in therapeutic efficacy. Strict physiological barriers, such as degradation and clearance in circulation, blood-brain barrier, cellular uptake, endosome/lysosome barriers, release, obstruct the delivery of nucleic acid drugs to the brain by the vectors. Nucleic acid drugs against a single target are inefficient in treating brain diseases of complex pathogenesis. Differences between individual patients lead to severe uncertainties in brain disease treatment with nucleic acid drugs. In this Review, we briefly summarize the classification of nucleic acid drugs. Next, we discuss physiological barriers during drug delivery and universal coping strategies and introduce the application methods of these universal strategies to nucleic acid drug vectors. Subsequently, we explore nucleic acid drug-based multidrug regimens for the combination treatment of brain diseases and the construction of the corresponding vectors. In the following, we address the feasibility of patient stratification and personalized therapy through diagnostic information from medical imaging and the manner of introducing contrast agents into vectors. Finally, we take a perspective on the future feasibility and remaining challenges of vector-based integrated diagnosis and gene therapy for brain diseases.

Nucleic acid therapy in pediatric cancer

The overall survival, progress free survival, and life quality of cancer patients have improved due to the advance in minimally invasive surgery, precision radiotherapy, and various combined chemotherapy in the last decade. Furthermore, the discovery of new types of therapeutics, such as immune checkpoint inhibitors and immune cell therapies have facilitated both patients and doctors to fight with cancers. Moreover, in the context of the development in biocompatible and cell type targeting nano-carriers as well as nucleic acid-based drugs for initiating and enhancing the anti-tumor response have come to the age. The treatment paradigms utilization of nucleic acids, including short interfering RNA (siRNA), antisense oligonucleotides (ASO), and messenger RNA (mRNA), can target specific protein expression to achieve the therapeutic effects. Over ten nucleic acid therapeutics have been approved by the FDA and EMA in rare diseases and genetic diseases as well as dozens of registered clinical trails for varies cancers. Though generally less dangerous of pediatric cancers than adult cancers was observed during the past decades, yet pediatric cancers accounted for a significant proportion of child deaths which hurt those family very deeply. Therefore, it is necessary to pay more attention for improving the treatment of pediatric cancer and discovering new nucleic acid therapeutics which may help to improve the therapeutic effect and prognoses in turns to ameliorate the survival period and quality of life for children patient. In this review, we focus on the nucleic acid therapy in pediatric cancers.

The Emerging Role of RNA N6-Methyladenosine Modification in Pancreatic Cancer

Pancreatic cancer (PC) is one of the most common malignant cancers, ranking the seventh highest causes of cancer-related deaths globally. Recently, RNA N6-methyladenosine (m6A) is emerging as one of the most abundant RNA modifications in eukaryote cells, involved in multiple RNA processes including RNA translocation, alternative splicing, maturation, stability, and degradation. As reported, m6A was dynamically and reversibly regulated by its “writers”, “erasers”, and “readers”, Increasing evidence has revealed the vital role of m6A modification in the development of multiple types of cancers including PC. Currently, aberrant m6A modification level has been found in both PC tissues and cell lines. Moreover, abnormal expressions of m6A regulators and m6A-modified genes have been reported to contribute to the malignant development of PC. Here in this review, we will focus on the function and molecular mechanism of m6A-modulated RNAs including coding RNAs as well as non-coding RNAs. Then the m6A regulators will be summarized to reveal their potential applications in the clinical diagnosis, prognosis, and therapeutics of PC.

Structural Optimization and Improving Antitumor Potential of Moreollic Acid from Gamboge

Moreollic acid, a caged-tetraprenylated xanthone from Gamboge, has been indicated as a potent antitumor molecule. In the present study, a series of moreollic acid derivatives with novel structures were designed and synthesized, and their antitumor activities were determined in multifarious cell lines. The preliminary screening results showed that all synthesized compounds selectively inhibited human colon cancer cell proliferation. TH12-10, with an IC50 of 0.83, 1.10, and 0.79 μM against HCT116, DLD1, and SW620, respectively, was selected for further antitumor mechanism studies. Results revealed that TH12-10 effectively inhibited cell proliferation by blocking cell-cycle progression from G1 to S. Besides, the apparent structure-activity relationships of target compounds were discussed. To summarize, a series of moreollic acid derivatives were discovered to possess satisfactory antitumor potentials. Among them, TH12-10 displays the highest antitumor activities against human colon cancer cells, in which the IC50 values in DLD1 and SW620 are lower than that of 5-fluorouracil.

Small interfering RNA (siRNA) to target genes and molecular pathways in glioblastoma therapy: Current status with an emphasis on delivery systems

Glioblastoma multiforme (GBM) is one of the worst brain tumors arising from glial cells, causing many deaths annually. Surgery, chemotherapy, radiotherapy and immunotherapy are used for GBM treatment. However, GBM is still an incurable disease, and new approaches are required for its successful treatment. Because mutations and amplifications occurring in several genes are responsible for the progression and aggressive behavior of GBM cells, genetic approaches are of great importance in its treatment. Small interfering RNA (siRNA) is a new emerging tool to silence the genes responsible for disease progression, particularly cancer. SiRNA can be used for GBM treatment by down-regulating genes such as VEGF, STAT3, ELTD1 or EGFR. Furthermore, the use of siRNA can promote the chemosensitivity of GBM cells. However, the efficiency of siRNA in GBM is limited via its degradation by enzymes, and its off-targeting effects. SiRNA-loaded carriers, especially nanovehicles that are ligand-functionalized by CXCR4 or angiopep-2, can be used for the protection and targeted delivery of siRNA. Nanostructures can provide a platform for co-delivery of siRNA plus anti-tumor drugs as another benefit. The prepared nanovehicles should be stable and biocompatible in order to be tested in human studies.

SYPL1 Inhibits Apoptosis in Pancreatic Ductal Adenocarcinoma via Suppression of ROS-Induced ERK Activation

Synaptophysin-like 1 (SYPL1) is a neuroendocrine-related protein. The role of SYPL1 in pancreatic ductal adenocarcinoma (PDAC) and the underlying molecular mechanism remain unclarified. Here, after analyzing five datasets (GSE15471, GSE16515, GSE28735, TCGA, and PACA-AU) and 78 PDAC patients from Sun Yat-sen University Cancer Center, we demonstrated that SYPL1 was upregulated in PDAC and that a high level of SYPL1 indicated poor prognosis. Bioinformatics analysis implied that SYPL1 was related to cell proliferation and cell death. To validate these findings, gain-of-function and loss-of-function experiments were carried out, and we found that SYPL1 promoted cell proliferation in vitro and in vivo and that it protected cells from apoptosis. Mechanistic studies revealed that sustained extracellular-regulated protein kinase (ERK) activation was responsible for the cell death resulting from knockdown of SYPL1. In addition, bioinformatics analysis showed that the expression of SYPL1 positively correlated with antioxidant activity. Reactive oxygen species (ROS) were upregulated in cells with SYPL1 knockdown and vice versa. Upregulated ROS led to ERK activation and cell death. These results suggest that SYPL1 plays a vital role in PDAC and promotes cancer cell survival by suppressing ROS-induced ERK activation.

The Ig superfamily protein PTGFRN coordinates survival signaling in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most malignant primary brain tumor with a median survival of approximately 14 months. Despite aggressive treatment of surgical resection, chemotherapy and radiation therapy, only 3-5% of GBM patients survive more than 3 years. Contributing to this poor therapeutic response, it is believed that GBM contains both intrinsic and acquired mechanisms of resistance, including resistance to radiation therapy. In order to define novel mediators of radiation resistance, we conducted a functional knockdown screen, and identified the immunoglobulin superfamily protein, PTGFRN. In GBM, PTGFRN is found to be overexpressed and to correlate with poor survival. Reducing PTGFRN expression radiosensitizes GBM cells and potently decreases the rate of cell proliferation and tumor growth. Further, PTGFRN inhibition results in significant reduction of PI3K p110β and phosphorylated AKT, due to instability of p110β. Additionally, PTGFRN inhibition decreases nuclear p110β leading to decreased DNA damage sensing and DNA damage repair. Therefore overexpression of PTGFRN in glioblastoma promotes AKT-driven survival signaling and tumor growth, as well as increased DNA repair signaling. These findings suggest PTGFRN is a potential signaling hub for aggressiveness in GBM.

PI3Kβ-A Versatile Transducer for GPCR, RTK, and Small GTPase Signaling

The phosphoinositide 3-kinase (PI3K) family includes eight distinct catalytic subunits and seven regulatory subunits. Only two PI3Ks are directly regulated downstream from G protein-coupled receptors (GPCRs): the class I enzymes PI3Kβ and PI3Kγ. Both enzymes produce phosphatidylinositol 3,4,5-trisposphate in vivo and are regulated by both heterotrimeric G proteins and small GTPases from the Ras or Rho families. However, PI3Kβ is also regulated by direct interactions with receptor tyrosine kinases (RTKs) and their tyrosine phosphorylated substrates, and similar to the class II and III PI3Ks, it binds activated Rab5. The unusually complex regulation of PI3Kβ by small and trimeric G proteins and RTKs leads to a rich landscape of signaling responses at the cellular and organismic levels. This review focuses first on the regulation of PI3Kβ activity in vitro and in cells, and then summarizes the biology of PI3Kβ signaling in distinct tissues and in human disease.

PIK3CB/p110β is a selective survival factor for glioblastoma

Background

Glioblastoma (GBM) is difficult to treat. Phosphoinositide 3-kinase (PI3K) is an attractive therapeutic target for GBM; however, targeting this pathway to effectively treat GBM is not successful because the roles of PI3K isoforms remain to be defined. The aim of this study is to determine whether PIK3CB/p110β, but not other PI3K isoforms, is a biomarker for GBM recurrence and important for cell survival.

Methods

Gene expression and clinical relevance of PI3K genes in GBM patients were analyzed using online databases. Expression/activity of PI3K isoforms was determined using immunoblotting. PI3K genes were inhibited using short hairpin RNAs or isoform-selective inhibitors. Cell viability/growth was assessed by the MTS assay and trypan blue exclusion assay. Apoptosis was monitored using the caspase activity assay. Mouse GBM xenograft models were used to gauge drug efficacy.

Results

PIK3CB/p110β was the only PI3K catalytic isoform that significantly correlated with high incidence rate, risk, and poor survival of recurrent GBM. PIK3CA/p110α, PIK3CB/p110β, and PIK3CD/p110δ were differentially expressed in GBM cell lines and primary tumor cells derived from patient specimens, whereas PIK3CG/p110γ was barely detected. PIK3CB/p110β protein levels presented a stronger association with the activities of PI3K signaling than other PI3K isoforms. Blocking p110β deactivated PI3K signaling, whereas inhibition of other PI3K isoforms had no effect. Specific inhibitors of PIK3CB/p110β, but not other PI3K isoforms, remarkably suppressed viability and growth of GBM cells and xenograft tumors in mice, with minimal cytotoxic effects on astrocytes.

Conclusions

PIK3CB/p110β is a biomarker for GBM recurrence and selectively important for GBM cell survival.

An Efficient Bivalent Cyclic RGD-PIK3CB siRNA Conjugate for Specific Targeted Therapy against Glioblastoma In Vitro and In Vivo

The PI3K-AKT-mTOR-signaling pathway is frequently activated in glioblastoma (GBM). Inhibition of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta (PIK3CB)/p110β (a PI3K catalytic isoform) by RNAi substantially suppresses GBM growth with less toxicity to normal astrocytes. However, insufficient and non-specific small interfering RNA (siRNA) delivery may limit the efficacy of RNAi-based therapies against GBM. Here we prepared a novel methoxy-modified PIK3CB siRNA molecule (siPIK3CB) that was covalently conjugated to a [cyclo(Arg-Gly-Asp-D-Phe-Lys)-Ahx]₂-Glu-PEG-MAL (biRGD) peptide, which selectively binds to integrin αvβ3 receptors. The αvβ3-positive U87MG cell line was selected as a representative for GBM. An orthotopic GBM xenograft model based on luciferase-expressing U87MG was established and validated in vivo to investigate bio-distribution and anti-tumor efficacy of biRGD-siPIK3CB. In vitro, biRGD-siPIK3CB specifically entered and silenced PIK3CB expression in GBM cells in an αvβ3 receptor-dependent manner, thus inhibiting cell cycle progression and migration and enhancing apoptosis. In vivo, intravenously injected biRGD-siPIK3CB substantially slowed GBM growth and prolonged survival by reducing tumor viability with silencing PIK3CB expression. Furthermore, biRGD-siPIK3CB led to mild tubulointerstitial injury in the treatment of GBM without obvious hepatotoxicity, whereas co-infusion of Gelofusine obviously alleviated this injury without compromising anti-tumor efficacy. These findings revealed a great translational potential of biRGD-siPIK3CB conjugate as a novel molecule for GBM therapy.

The Role of Class IA Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunits in Glioblastoma

Phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) plays a critical role in the pathogenesis of cancer including glioblastoma, the most common and aggressive form of brain cancer. Targeting the PI3K pathway to treat glioblastoma has been tested in the clinic with modest effect. In light of the recent finding that PI3K catalytic subunits (PIK3CA/p110α, PIK3CB/p110β, PIK3CD/p110δ, and PIK3CG/p110γ) are not functionally redundant, it is imperative to determine whether these subunits play divergent roles in glioblastoma and whether selectively targeting PI3K catalytic subunits represents a novel and effective strategy to tackle PI3K signaling. This article summarizes recent advances in understanding the role of PI3K catalytic subunits in glioblastoma and discusses the possibility of selective blockade of one PI3K catalytic subunit as a treatment option for glioblastoma.

TGX-221 inhibits proliferation and induces apoptosis in human glioblastoma cells

Glioblastoma is the most common type of primary brain tumor in adults, with high mortality and morbidity rates. More effective therapeutic strategies are imperative. Previous studies have shown that the known p110-β-selective inhibitor TGX-221 blocks the activation of PKB/Akt in PTEN-deficient cells. We treated U87 and U251 glioblastoma cells with TGX-221 to determine the effect of TGX-221. We performed a Cell Counting Kit-8 (CCK-8) test, EDU staining and cell cycle distribution analysis and found that TGX-221 inhibited glioblastoma cell proliferation. Next, the effect of TGX-221 on cell apoptosis was investigated using flow cytometry. These results demonstrated that TGX-221 induced apoptosis in glioblastoma cells. Moreover, migration and invasion assays revealed that TGX-221 inhibited human glioblastoma cell migration and invasion. Collectively, our study revealed that TGX-221 could inhibit proliferation and induce apoptosis in glioblastoma cells.

Advances in subunits of PI3K class I in cancer

Phosphatidylinositol 3-kinases (PI3Ks) include members of a unique and conserved family of intracellular lipid kinases that phosphorylate the 3-hydroxyl group of phosphatidylinositols and phosphoinositides. The resultant activation of many intracellular signalling pathways regulates various biological functions such as cell metabolism, survival, growth, proliferation, polarity, and apoptosis. PI3Ks are classified into three types: class I, II, and III. Of them, class I PI3K is most widely studied and plays an important role in the development and progression of tumours. In this review, we describe PI3K family members and their functions, especially the subunits of class I PI3K, their alterations in cancers, as well as PI3K inhibitors and their clinical trial status in cancer-targeted therapy.

Resveratrol inhibits glioma cell growth via targeting oncogenic microRNAs and multiple signaling pathways

Resveratrol (Res), a natural polyphenolic compound, has anticancer activity in a variety of cancers. In the present study, the antitumor effect and underlying molecular mechanism of Res on rat C6 glioma growth was studied. The results demonstrated that Res inhibited glioma cell proliferation, arrested cell cycle in S phase and induced apoptosis in vitro. Res also suppressed intracranial C6 tumor growth in vivo and prolonged survival in a fraction of the rats bearing intracranial gliomas. Res significantly downregulated the specific miRs, including miR-21, miR-30a-5p and miR-19, which have been identified as oncomiRs in our previous studies, and altered the expression of their targeting and crucial genes for glioma formation and progression such as p53, PTEN, EGFR, STAT3, COX-2, NF-κB and PI3K/AKT/mTOR pathway. Therefore, the anti-glioma effect of Res, at least in part, is through the regulation of oncogenic miRNAs. The effect of Res on non-coding RNAs should be studied further. Res is a potential multi-targeting drug for the treatment of gliomas.

Construction of a recombinant lentivirus containing human microRNA-7-3 and its inhibitory effects on glioma proliferation

In the present study, we constructed a lentivirus, FIV-CMV-GFP-miR-7-3, containing the microRNA-7-3 gene and the green fluorescent protein gene, and used it to transfect human glioma U251 cells. Fluorescence microscopy showed that 80% of U251 cells expressed green fluorescence. Real-time reverse transcription PCR showed that microRNA-7-3 RNA expression in U251 cells was significantly increased. Proliferation was slowed in transfected U251 cells, and most cells were in the G1 phase of the cell cycle. In addition, the expression of the serine/threonine protein kinase 2 was decreased. Results suggested that transfection with a lentivirus carrying microRNA-7-3 can effectively suppress epidermal growth factor receptor pathway activity in U251 cells, arrest cell cycle transition from G1 phase to S phase and inhibit glioma cell growth.

Human cytomegalovirus inhibits apoptosis by regulating the activating transcription factor 5 signaling pathway in human malignant glioma cells

The activating transcription factor 5 (ATF5), also termed ATFx, is a member of the ATF/cAMP response element-binding protein (CREB) family of basic zipper proteins. ATF5 is an anti-apoptotic protein that is highly expressed in malignant glioma and is essential for glioma cell survival. Accumulating evidence indicates that human malignant gliomas are universally infected with human cytomegalovirus (HCMV). Recent studies have shown that HCMV may be resistant to the induction of apoptosis by disrupting cellular pathways in glioblastoma. To investigate the potential anti-apoptotic function of HCMV in glioma, malignant U87 glioma cells were infected with HCMV. The present study showed that HCMV infection suppressed apoptosis in glioblastoma U87 cells by regulating the expression of ATF5. Furthermore, in glioblastoma U87 cells, HCMV infection induced cellular proliferation in parallel with an increase in the expression level of ATF5 and B-cell lymphoma/leukemia-2 to Bcl-2-associated X protein ratio. Loss of ATF5 function was achieved using a dominant-negative form of ATF5 in U87 cells, whereby cells appeared to grow marginally following HCMV infection when compared with the control. However, the anti-apoptotic ability was appeared to decline in the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. These results indicate that ATF5 signaling pathways may be important in the anti-apoptotic activity of HCMV-infected glioblastoma cells; therefore, the anti-apoptotic molecular mechanisms of HCMV in human glioblastoma cells were investigated in the current study. Prevention of HCMV infection may present a potential and promising approach for the treatment of malignant gliomas.

Acquired microcephaly in blepharophimosis-ptosis-epicanthus inversus syndrome because of an interstitial 3q22.3q23 deletion

BACKGROUND

Blepharophimosis-ptosis-epicanthus inversus syndrome is an autosomal dominant condition because of mutations or deletions of the FOXL2 gene. Microcephaly is not associated with FOXL2 mutations but has been reported in individuals with chromosome 3q deletions, which include the FOXL2 gene and other contiguous genes. The ATR gene has been reported as a candidate gene for microcephaly in individuals with contiguous deletion of chromosome 3q involving the FOXL2 gene.

PATIENT

We describe a girl with blepharophimosis-ptosis-epicanthus inversus syndrome along with acquired microcephaly and intellectual disability.

RESULTS

Our patient had a deletion of chromosome 3q22.2q23, which does not include the ATR gene but does include the PIK3CB gene as a candidate gene for microcephaly.

CONCLUSION

We propose that the PIK3CB gene included in our patient's chromosome 3q deletion may be the gene responsible for microcephaly and other patients with blepharophimosis-ptosis-epicanthus inversus syndrome because of a chromosome 3q deletion.

Artemether combined with shRNA interference of vascular cell adhesion molecule-1 significantly inhibited the malignant biological behavior of human glioma cells

Artemether is the derivative extracted from Chinese traditional herb and originally used for malaria. Artemether also has potential therapeutic effects against tumors. Vascular cell adhesion molecule-1 (VCAM-1) is an important cell surface adhesion molecule associated with malignancy of gliomas. In this work, we investigated the role and mechanism of artemether combined with shRNA interference of VCAM-1 (shRNA-VCAM-1) on the migration, invasion and apoptosis of glioma cells. U87 human glioma cells were treated with artemether at various concentrations and shRNA interfering technology was employed to silence the expression of VCAM-1. Cell viability, migration, invasiveness and apoptosis were assessed with MTT, wound healing, Transwell and Annexin V-FITC/PI staining. The expression of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and phosphorylated Akt (p-Akt) was checked by Western blot assay. Results showed that artemether and shRNA-VCAM-1 not only significantly inhibited the migration, invasiveness and expression of MMP-2/9 and p-Akt, but also promoted the apoptosis of U87 cells. Combined treatment of both displayed the maximum inhibitory effects on the malignant biological behavior of glioma cells. Our work revealed the potential therapeutic effects of artemether and antiVCAM-1 in the treatments of gliomas.

The different role of Notch1 and Notch2 in astrocytic gliomas

It is well known that Notch signaling plays either oncogenic or tumor suppressive role in a variety of tumors, depending on the cellular context. However, in our previous study, we found that Notch1 was overexpressed while Notch2 downregulated in the majority of astrocytic gliomas with different grades as well as in glioblastoma cell lines U251 and A172. We had knocked down Notch1 by siRNA in glioblastoma cells, and identified that the cell growth and invasion were inhibited, whereas cell apoptosis was induced either in vitro or in vivo. For further clarification of the role of Notch2 in pathogenesis of gliomas, enforced overexpression of Notch2 was carried out with transfection of Notch2 expression plasmid in glioma cells and the cell growth, invasion and apoptosis were examined in vitro and in vivo in the present study, and siRNA targeting Notch1 was used as a positive control in vivo. The results showed that upregulating Notch2 had the effect of suppressing cell growth and invasion as well as inducing apoptosis, just the same as the results of knocking down Notch1. Meanwhile, the activity of core signaling pathway–EGFR/PI3K/AKT in astrocytic glioma cells was repressed. Thus, the present study reveals, for the first time, that Notch1 and Notch2 play different roles in the biological processes of astrocytic gliomas. Knocking down the Notch1 or enforced overexpression of Notch2 both modulate the astrocytic glioma phenotype, and the mechanism by which Notch1 and 2 play different roles in the glioma growth should be further investigated.

Signal transduction molecule patterns indicating potential glioblastoma therapy approaches

PURPOSE

The expression of an array of signaling molecules, along with the assessment of real-time cell proliferation, has been performed in U87 glioma cell line and in patients' glioblastoma established cell cultures in order to provide a better understanding of cellular and molecular events involved in glioblastoma pathogenesis. Experimental therapy was performed using a phosphatidylinositol-3'-kinase (PI3K) inhibitor.

PATIENTS AND METHODS

xMAP technology was employed to assess expression levels of several signal transduction molecules and real-time xCELLigence platform for cell behavior.

RESULTS

PI3K inhibition induced the most significant effects on global signaling pathways in patient-derived cell cultures, especially on members of the mitogen-activated protein-kinase family, P70S6 serine-threonine kinase, and cAMP response element-binding protein expression and further prevented tumor cell proliferation.

CONCLUSION

The PI3K pathway might be a prime target for glioblastoma treatment.

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.

Down-regulation of p110β expression increases chemosensitivity of colon cancer cell lines to oxaliplatin

This study examined the synergetic effect of class IA Phosphoinositide 3-kinases catalytic subunit p110β knockdown in conjunction with oxaliplatin treatment on colon cancer cells. Down-regulation of p110β by siRNA interference and oxaliplatin treatment were applied in colon cancer cell lines HT29, SW620 and HCT116. MTT assay was used to measure the inhibitory effect of p110β knockdown on the proliferation of colon cancer cell lines. SubG1 assay and Annexin-V FITC/PI double-labeling cytometry were applied to detect cell apoptosis. And cell cycle was evaluated by using PI staining and flow cytometry. The expression of caspase 3, cleaved PARP, p-Akt, T-Akt and p110β was determined by western blotting. The results suggested that down-regulation of p110β expression by siRNA obviously reduced cell number via accumulation in G(0)-G(1) phase of the cell cycle in the absence of notablely increased apoptosis in colon cancer cell lines HT29 and SW620 (S phase arrest in HCT116). Moreover, inhibition of p110β expression increased oxaliplatin-induced cell apoptosis and cell cycle arrest in HT29, HCT116 and SW620 cell lines. In addition, increases of cleaved caspase-3 and cleaved PARP induced by oxaliplatin treatment were determined by immunoblotting in p110β knockdown group compared with normal control group and wild-type group. It is concluded that down-regulated expression of p110β could inhibit colon cancer cells proliferation and result in increased chemosensitivity of colorectal cancer cells to oxaliplatin through augmentation of oxaliplatin-induced cell apoptosis and cell cycle arrest.

A novel therapeutic strategy for the treatment of glioma, combining chemical and molecular targeting of hsp90a

Hsp90α's vital role in tumour survival and progression, together with its highly inducible expression profile in gliomas and its absence in normal tissue and cell lines validates it as a therapeutic target for glioma. Hsp90α was downregulated using the post-transcriptional RNAi strategy (sihsp90α) and a post-translational inhibitor, the benzoquinone antibiotic 17-AAG. Glioblastoma U87-MG and normal human astrocyte SVGp12 were treated with sihsp90α, 17-AAG and concurrent sihsp90α/17-AAG (combined treatment). Both Hsp90α gene silencing and the protein inhibitor approaches resulted in a dramatic reduction in cell viability. Results showed that sihsp90α, 17-AAG and a combination of sihsp90α/17-AAG, reduced cell viability by 27%, 75% and 88% (p < 0.001), respectively, after 72 h. hsp90α mRNA copy numbers were downregulated by 65%, 90% and 99% after 72 h treatment with sihsp90α, 17-AAG and sihsp90α/17-AAG, respectively. The relationship between Hsp90α protein expression and its client Akt kinase activity levels were monitored following treatment with sihsp90α, 17-AAG and sihsp90α/17-AAG. Akt kinase activity was downregulated as a direct consequence of Hsp90α inhibition. Both Hsp90α and Akt kinase levels were significantly downregulated after 72 h. Although, 17-AAG when used as a single agent reduces the Hsp90α protein and the Akt kinase levels, the efficacy demonstrated by combinatorial treatment was found to be far more effective. Combination treatment reduced the Hsp90α protein and Akt kinase levels to 4.3% and 43%, respectively, after 72 h. hsp90α mRNA expression detected in SVGp12 was negligible compared to U87-MG, also, the combination treatment did not compromise the normal cell viability. Taking into account the role of Hsp90α in tumour progression and the involvement of Akt kinase in cell signalling and the anti-apoptotic pathways in tumours, this double targets treatment infers a novel therapeutic strategy.

Targeting PI3K signaling as a therapeutic approach for colorectal cancer

Survival times of patients with colorectal cancer (CRC) have increased over the past decade, primarily as a result of treatment with combinations of conventional cytotoxic agents. Because CRC is commonly associated with mutations in genes that control growth factor signaling, therapies are being developed to target the products of these genes; individualized treatment might also be guided by specific mutations in tumors and by new biomarkers. Currently, targeted therapies confer limited clinical benefit; better drugs are therefore needed. Genomic studies indicate that phosphoinositide 3-kinase (PI3K) signaling is one of the most frequently deregulated pathways in several human cancers, including CRC. PI3K signaling has an important role in cancer cell proliferation, survival, motility, and metabolism and therefore could be an attractive therapeutic target. We review PI3K signaling in CRC and discuss current therapeutic approaches.

PTEN restoration and PIK3CB knockdown synergistically suppress glioblastoma growth in vitro and in xenografts

Glioblastoma is the most frequent and malignant glioma in adults. To develop an effective gene therapy strategy for glioblastoma, we investigated the anti-proliferative effects of phosphatase and tensin homolog (PTEN) restoration and siRNAs specifically targeting PIK3CB and PIK3CA on PTEN-deficient glioblastoma cells in vitro and in subcutaneous xenografts. Restoration of PTEN or knockdown of PIK3CB, but not PIK3CA, in glioblastoma cells markedly down-regulates the phosphorylation level of AKT, inhibits cell proliferation and colony formation, arrests the cell cycle at the G0/G1 stage, and promotes caspase-dependent apoptosis. Combined treatment with PTEN restoration and PIK3CB knockdown shows strong synergy. PTEN restoration or PIK3CB knockdown is also able to efficiently inhibit the growth of human U251 glioblastoma xenografts in nude mice, while tumor growth is entirely suppressed by a combination of the two treatments. In addition, we found that the mRNA levels of inhibitors of apoptosis proteins (IAPs) are reduced in U251 cells by PTEN restoration, suggesting that combined antitumor effects may also be partly attributed to the inhibition of the IAP pathway by PTEN restoration. Collectively, our results demonstrate that PI3 K isoforms play specific roles in tumorigenesis, and that combined treatment of PTEN restoration and PIK3CB siRNA is a promising gene therapy strategy for PTEN-deficient gliomas.

Interruption of β-catenin suppresses the EGFR pathway by blocking multiple oncogenic targets in human glioma cells

Malignant gliomas are the most common type of intrinsic central nervous system (CNS) tumors with high mortality and morbidity. β-catenin is overexpressed in human glioblastoma and knockdown of β-catenin inhibits glioblastoma cell proliferation and invasive ability, and induces apoptotic cell death. Furthermore, treating the nude mice carrying established subcutaneous LN229 gliomas with siRNA targeting β-catenin intratumorally also delayed the tumor growth. However, the mechanisms of down-regulation of β-catenin that represses glioblastoma malignancy behavior remain to be elucidated. We utilized text-mining of MEDLINE abstracts with natural language processing to establish the β-catenin biologic association network, and identified several interactions of this network with the EGFR pathway. In both in vitro and in vivo studies, our results confirmed down-regulation of β-catenin induced reduced expression of EGFR, STAT3 and AKT1 mRNA and protein, besides, the level of phosphorylated Akt also decreased. A similar reduction in expression of CyclinD1, MMP2 and MMP9, downstream genes of the EGFR pathway, was observed. These results suggest that the Wnt/β-catenin pathway regulates glioma cell proliferation and invasion, in part via the EGFR pathway.

Inactivation of PI3K/AKT signaling inhibits glioma cell growth through modulation of β-catenin-mediated transcription

Aberrant Wnt/β-catenin signaling contributes to the development of many cancers, including glial tumorigenesis. While cross talk between the Wnt/β-catenin and PI3K/AKT signaling pathways has been proposed, the impact of PI3K/AKT inhibition on β-catenin signaling in glioma remains unknown. In the present study, we report decreased cell proliferation and invasive ability upon the LY294002-induced inhibition of PI3K in both U251 and LN229 human glioblastoma cells in vitro. Pharmacologic inhibition of PI3K resulted in the downregulation of several members of the β-catenin pathway, including Fra-1, c-Myc, and cyclin D1. Downregulation impacted β-catenin-mediated transcription, as LY294002 decreased β-catenin/TCF transcriptional activity, determined by the reporter assay. Similar results were observed in vivo, as intratumoral injection of LY294002 downregulated the expression of the components of the β-catenin pathway and delayed tumor growth in nude mice harboring subcutaneous LN229 xenografts. These results suggest that the PI3K/AKT signaling pathway regulates glioma cell proliferation, in part via repression of the Wnt/β-catenin pathway.

Tat-BMPs-PAMAM conjugates enhance therapeutic effect of small interference RNA on U251 glioma cells in vitro and in vivo

Polyamidoamine (PAMAM) dendrimer and Tat peptides were conjugated to bacterial magnetic nanoparticles (BMPs) for the construction of an efficient and targeted gene delivery system with transmembrane ability for the gene therapy of brain tumors. Tat-BMPs-PAMAM was complexed with small interfering RNA expression plasmid (psiRNA) corresponding to the open reading frame of the human epidermal growth factor receptor gene (psiRNA-EGFR) to downregulate the EGFR gene by electrostatic interaction. The antitumor effect of psiRNA-EGFR delivered via Tat-BMPs-PAMAM was assessed both in human glioblastoma U251-MG cells and in nude mouse models. Compared with control groups, Tat-BMPs-PAMAM/psiRNA-EGFR resulted in better suppression of EGFR expression and a more obviously arrested effect on the proliferation and invasion ability of U251 cells in vitro. In addition, the growth rate of tumor in the U251 subcutaneous nude mouse model treated with Tat-BMPs-PAMAM/psiRNA-EGFR was slower than in those treated with phosphate-buffered saline or Lipofectamine 2000/psiRNA-Scr. Also, compared with control groups, the expression of oncoproteins (EGFR, p-AKT, MMP2/9, PCNA, VEGF, Bcl-2, and cyclin D1) was obviously downregulated and the number of apoptotic cells was clearly increased in the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups. In addition, there was no significant difference between the results in vitro and in vivo for the Tat-BMPs-PAMAM/psiRNA-EGFR treatment groups and those of the Lipofectamine 2000/psiRNA-EGFR treatment groups. These results show that Tat-BMPs-PAMAM, with its targeted delivery and transmembrane ability, may be a novel gene delivery system with potential applications in the targeted gene therapy of brain tumors.

The oncogenic roles of Notch1 in astrocytic gliomas in vitro and in vivo

Notch receptors play an essential role in cellular processes during embryonic and postnatal development, including maintenance of stem cell self-renewal, proliferation, and determination of cell fate and apoptosis. Deregulation of Notch signaling has been implicated in some genetic diseases and tumorigenesis. The function of Notch signaling in a variety of tumors can be either oncogenic or tumor-suppressive, depending on the cellular context. In this study, Notch1 overexpression was observed in the majority of 45 astrocytic gliomas with different grades and in U251MG glioma cells. Transfection of siRNA targeting Notch1 into U251 cells in vitro downregulated Notch1 expression, associated with inhibition of cell growth, arrest of cell cycle, reduction of cell invasiveness, and induction of cell apoptosis. Meanwhile, tumor growth was delayed in established subcutaneous gliomas in nude mice treated with Notch1 siRNA in vivo. These results suggest that Notch1 plays an important oncogenic role in the development and progression of astrocytic gliomas. Furthermore, knockdown of Notch1 expression by siRNA simultaneously downregulated the expression of EGFR and the important components of its downstream pathways, including PI3K, p-AKT, K-Ras, cyclin D1 and MMP9, indicating the crosstalk and interaction of Notch and EGFR signaling pathways.

PIK3CA and PIK3CB inhibition produce synthetic lethality when combined with estrogen deprivation in estrogen receptor-positive breast cancer

Several phosphoinositide 3-kinase (PI3K) catalytic subunit inhibitors are currently in clinical trial. We therefore sought to examine relationships between pharmacologic inhibition and somatic mutations in PI3K catalytic subunits in estrogen receptor (ER)-positive breast cancer, in which these mutations are particularly common. RNA interference (RNAi) was used to determine the effect of selective inhibition of PI3K catalytic subunits, p110alpha and p110beta, in ER(+) breast cancer cells harboring either mutation (PIK3CA) or gene amplification (PIK3CB). p110alpha RNAi inhibited growth and promoted apoptosis in all tested ER(+) breast cancer cells under estrogen deprived-conditions, whereas p110beta RNAi only affected cells harboring PIK3CB amplification. Moreover, dual p110alpha/p110beta inhibition potentiated these effects. In addition, treatment with the clinical-grade PI3K catalytic subunit inhibitor BEZ235 also promoted apoptosis in ER(+) breast cancer cells. Importantly, estradiol suppressed apoptosis induced by both gene knockdowns and BEZ235 treatment. Our results suggest that PI3K inhibitors should target both p110alpha and p110beta catalytic subunits, whether wild-type or mutant, and be combined with endocrine therapy for maximal efficacy when treating ER(+) breast cancer.

Should individual PI3 kinase isoforms be targeted in cancer?

Activation of the phosphoinositide-3-kinase (PI3K) signaling pathway is frequently found in common human cancers, brought about by oncogenic receptor tyrosine kinases (RTKs) acting upstream, PTEN loss, or activating mutations of PI3K itself. Recent studies have delineated distinct but overlapping functions in cell signaling and tumorigenesis for p110alpha and p110beta, the two major catalytic subunits of PI3K expressed in the tissues of origin for the common tumor types. In most cell types studied, p110alpha carries the majority of the PI3K signal in classic RTK signal transduction, while p110beta responds to GPCRs. Both p110alpha and p110beta function in cellular transformation induced by alterations in components of PI3K pathway. Specifically, p110alpha is essential for the signaling and growth of tumors driven by PIK3CA mutations and/or oncogenic RTKs/Ras, whereas p110beta is the major isoform in mediating PTEN-deficient tumorigenesis. While pan-PI3K inhibitors are currently being tested in the clinic, p110 isoform-specific inhibition holds promise as a therapeutic strategy.

Downregulation of Wnt2 and beta-catenin by siRNA suppresses malignant glioma cell growth

Increasing evidence suggests that aberrant activation of Wnt signaling is involved in tumor development and progression. Our earlier study on gene expression profile in human gliomas by microarray found that some members of Wnt family were overexpressed. To further investigate the involvement of Wnt signaling in gliomas, the expression of core components of Wnt signaling cascade in 45 astrocytic glioma specimens with different tumor grades was examined by reverse transcription-PCR and immunohistochemistry. Wnt2, Wnt5a, frizzled2 and beta-catenin were overexpressed in gliomas. Knockdown of Wnt2 and its key mediator beta-catenin in the canonical Wnt pathway by siRNA in human U251 glioma cells inhibited cell proliferation and invasive ability, and induced apoptotic cell death. Furthermore, treating the nude mice carrying established subcutaneous U251 gliomas with siRNA targeting Wnt2 and beta-catenin intratumorally also delayed the tumor growth. In both in vitro and in vivo studies, downregulation of Wnt2 and beta-catenin was associated with the decrease of PI3K/p-AKT expression, indicating the interplay between Wnt/beta-catenin and PI3K/AKT signaling cascades. In conclusion, the canonical Wnt pathway is of critical importance in the gliomagenesis and intervention of this pathway may provide a new therapeutic approach for malignant gliomas.

Phosphoinositide 3-kinases p110alpha and p110beta regulate cell cycle entry, exhibiting distinct activation kinetics in G1 phase

Phosphoinositide 3-kinase (PI3K) is an early signaling molecule that regulates cell growth and cell cycle entry. PI3K is activated immediately after growth factor receptor stimulation (at the G(0)/G(1) transition) and again in late G(1). The two ubiquitous PI3K isoforms (p110alpha and p110beta) are essential during embryonic development and are thought to control cell division. Nonetheless, it is presently unknown at which point each is activated during the cell cycle and whether or not they both control S-phase entry. We found that p110alpha was activated first in G(0)/G(1), followed by a minor p110beta activity peak. In late G(1), p110alpha activation preceded that of p110beta, which showed the maximum activity at this time. p110beta activation required Ras activity, whereas p110alpha was first activated by tyrosine kinases and then further induced by active Ras. Interference with p110alpha and -beta activity diminished the activation of downstream effectors with different kinetics, with a selective action of p110alpha in blocking early G(1) events. We show that inhibition of either p110alpha or p110beta reduced cell cycle entry. These results reveal that PI3Kalpha and -beta present distinct activation requirements and kinetics in G(1) phase, with a selective action of PI3Kalpha at the G(0)/G(1) phase transition. Nevertheless, PI3Kalpha and -beta both regulate S-phase entry.