Multi-combination therapy for temozolomide-resistant GBM: identification of temozolomide/small molecule inhibitor combinations that target the MDM2/p53 and PI3K-AKT/mTOR networks

Introduction: Glioblastoma (GBM) is the most aggressive malignant brain cancer in adults. Induction of the DNA damage response pathway by Temozolomide (TMZ), a DNA alkylating agent, activates p53 resulting in apoptosis. GBM can adapt by upregulatingthe pro-survival pathway regulator Protein Kinase B (AKT), which phosphorylates murine double minute 2 (MDM2) resulting in increased MDM2-mediated p53 ubiquitination. We hypothesize that a combination treatment of blood-brain-barrier penetrant small molecule inhibitors (SMIs) to AKT (GDC-0068) and MDM2 protein-protein interaction inhibitor (RG7388), will stabilize p53 expression and potentiate TMZ-mediated effects in a recurrent p53wt GBM xenoline. Methods: Dose response assays followed by Calcusyn statistical analysis determined optimal combination dose ratios. Incucyte imaging analyzedconfluence throughout a treatment cycle. Cellular response was characterized by: 1) Western blotting 2) Flow cytometry with SPiDER β-Gal and FITC Annexin V/ Propidium Iodide to quantify senescent and apoptotic cells, respectively 3) p53 siRNA knockdown to examine p53 dependency in treated cells. Results: Combination index identified synergismof TMZ in the presence of AKT and MDM2 inhibitors at clinically achievable concentrations. Incucyte confirmed a low-dose triple combination significantly inhibited tumor growth. Western blots detected low expression of cleaved PARP and elevated expression of p53 and p21 in RG7388-treated cells compared to vehicle, suggesting senescence-related growth inhibition. SPiDER β-Gal and FITC Annexin V/PI assays confirmed a high percentage of senescent cells and minimal apoptosis following combination treatment compared to vehicle or single SMI-treated cells. P53 siRNA knockdown confirmed that cell growth inhibition is p53 dependent in treated cells. Conclusion: This study provides rationale for targeting p53 in recurrent p53wt GBM and reveals that senescence could function as a potential therapeutic resistance mechanism. In future studies, targeting of the MDM2-p53 network in the presence of a SM senescence inhibitor will be evaluated to determine if this increases GBM cell death.

Microglial Cytokines Induce Invasiveness and Proliferation of Human Glioblastoma through Pyk2 and FAK Activation

Glioblastoma is the most aggressive brain tumor in adults. Multiple lines of evidence suggest that microglia create a microenvironment favoring glioma invasion and proliferation. Our previous studies and literature reports indicated the involvement of focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (Pyk2) in glioma cell proliferation and invasion, stimulated by tumor-infiltrating microglia. However, the specific microglia-released factors that modulate Pyk2 and FAK signaling in glioma cells are unknown. In this study, 20 human glioblastoma specimens were evaluated with the use of RT-PCR and western blotting. A Pierson correlation test demonstrated a correlation (0.6–1.0) between the gene expression levels for platelet-derived growth factor β(PDGFβ), stromal-derived factor 1α (SDF-1α), IL-6, IL-8, and epidermal growth factor (EGF) in tumor-purified microglia and levels of p-Pyk2 (Y579/Y580) and p-FAK(Y925) in glioma cells. siRNA knockdown against Pyk2 or FAK in three primary glioblastoma cell lines, developed from the investigated specimens, in combination with the cytokine receptor inhibitors gefitinib (1 μM), DMPQ (200 nM), and burixafor (1 μM) identified EGF, PDGFβ, and SDF-1α as key extracellular factors in the Pyk2- and FAK-dependent activation of invadopodia formation and the migration of glioma cells. EGF and IL-6 were identified as regulators of the Pyk2- and FAK-dependent activation of cell viability and mitosis.

PDIA3 inhibits mitochondrial respiratory function in brain endothelial cells and C. elegans through STAT3 signaling and decreases survival after OGD

Background Protein disulfide isomerase A3 (PDIA3, also named GRP58, ER-60, ERp57) is conserved across species and mediates protein folding in the endoplasmic reticulum. PDIA3 is, reportedly, a chaperone for STAT3. However, the role of PDIA3 in regulating mitochondrial bioenergetics and STAT3 phosphorylation at serine 727 (S727) has not been described. Methods Mitochondrial respiration was compared in immortalized human cerebral microvascular cells (CMEC) wild type or null for PDIA3 and in whole organism C. Elegans WT or null for pdi-3 (worm homologue). Mitochondrial morphology and cell signaling pathways in PDIA3-/- and WT cells were assessed. PDIA3-/- cells were subjected to oxygen–glucose deprivation (OGD) to determine the effects of PDIA3 on cell survival after injury. Results We show that PDIA3 gene deletion using CRISPR-Cas9 in cultured CMECs leads to an increase in mitochondrial bioenergetic function. In C. elegans, gene deletion or RNAi knockdown of pdi-3 also increased respiratory rates, confirming a conserved role for this gene in regulating mitochondrial bioenergetics. The PDIA3-/- bioenergetic phenotype was reversed by overexpression of WT PDIA3 in cultured PDIA3-/- CMECs. PDIA3-/- and siRNA knockdown caused an increase in phosphorylation of the S727 residue of STAT3, which is known to promote mitochondrial bioenergetic function. Increased respiration in PDIA3-/- CMECs was reversed by a STAT3 inhibitor. In PDIA3-/- CMECs, mitochondrial membrane potential and reactive oxygen species production, but not mitochondrial mass, was increased, suggesting an increased mitochondrial bioenergetic capacity. Finally, PDIA3-/- CMECs were more resistant to oxygen–glucose deprivation, while STAT3 inhibition reduced the protective effect. Conclusions We have discovered a novel role for PDIA3 in suppressing mitochondrial bioenergetic function by inhibiting STAT3 S727 phosphorylation.

Decrease in ITGA7 Levels Is Associated with an Increase in α-Synuclein Levels in an MPTP-Induced Parkinson’s Disease Mouse Model and SH-SY5Y Cells

We investigated the potential association between integrin α7 (ITGA7) and alpha-synuclein (α-syn) in a methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson’s disease (PD) mouse model. Tyrosine hydroxylase (TH), ITGA7, and α-syn expression in the substantia nigra (SN) of the brain were observed to examine the pathological characteristics of PD. To determine the relationship between ITGA7 and PD, the expression of TH and α-syn was investigated after ITGA7 siRNA knockdown in SH-SY5Y cells. The ITGA7 microarray signal was decreased in the SN of the MPTP group, indicating reduced ITGA7 expression compared to that in the control. The expression patterns of ITGA7 in the control group and those of α-syn in the MPTP group were similar on immunohistochemical staining. Reduction in ITGA7 expression by ITGA7 siRNA administration induced a decrease in TH expression and an increase in α-syn expression in SH-SY5Y cells. The decreased expression of ITGA7 significantly decreased the expression of bcl2 and increased the bax/bcl2 ratio in SH-SY5Y cells. These results suggest that reduced ITGA7 expression may be related to increased α-syn expression and apoptosis of dopaminergic cells in an MPTP-induced PD mouse model. To the best of our knowledge, this is the first study to show an association between ITGA7 and PD.

Inhibition of MUS81 By siRNA Reverses Resistance to Cisplatin in Human Ovarian Cancer Cell Lines

Bacground: Drugs that induce DNA interstrand crosslinks form the mainstay of anticancer treatments for different cancers. These drugs are used to treat ovarian cancer which is the most prevalent gynaecological cancer. Five-year survival rates are approximately 40% and the development of drug resistant disease is an important factor in treatment failure. Methods: In this study a comprehensive evaluation of the expression and function of the site-specific endonuclease MUS81 was conducted. Using quantitative real time PCR analysis and imaging flow cytometry we determined the mRNA and protein expression of MUS81 in three ovarian cancer cell lines and two immortalised human fibroblast cell lines which had been made resistant to cisplatin by chronic exposure. siRNA knockdown of MUS81 was employed to determine the effect on overall cell survival which was assessed using clonogenic assays. Results: In the five cisplatin-resistant cell lines we observed increased MUS81 mRNA expression. In addition MUS81 protein expression in the form of discrete nuclear foci in cells was observed in all cell lines following cisplatin exposure, there being significantly more foci in cisplatin resistant cell lines. siRNA knockdown of MUS81 significantly reduced both mRNA and protein levels in two cell lines (SK-OV-3 and MRC5-SV1 – wild-type and resistant) and critically re-sensitised cisplatin resistant cells to wild-type level, determined by clonogenic assay.Conclusion: MUS81 is central to the development of cisplatin resistance in ovarian cancer cell lines. Inhibition of MUS81 restored drug sensitivity to the cells. MUS81 may be a useful therapeutic target to overcome drug resistance in ovarian and other cancers.

Major Vault Protein Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection in CRL2843CD163 Cell Lines and Primary Porcine Alveolar Macrophages

Porcine reproductive and respiratory syndrome (PRRS), a significant viral infectious disease that commonly occurs among farmed pigs, leads to considerable economic losses to the swine industry worldwide. Major vault protein (MVP) is a host factor that induces type Ⅰ interferon (IFN) production. In this study, we evaluated the effect of MVP on PRRSV infection in CRL2843CD163 cell lines and porcine alveolar macrophages (PAMs). Our results showed that MVP expression was downregulated by PRRSV infection. Adenoviral overexpression of MVP inhibited PRRSV replication, whereas the siRNA knockdown of MVP promoted PRRSV replication. In addition, MVP knockdown has an adverse effect on the inhibitive role of MVP overexpression on PRRSV replication. Moreover, MVP could induce the expression of type Ⅰ IFNs and IFN-stimulated gene 15 (ISG15) in PRRSV-infected PAMs. Based on these results, MVP may be a potential molecular target of drugs for the effective prevention and treatment of PRRSV infection.

β2-Adrenoceptor Activation Stimulates IL-6 Production via PKA, ERK1/2, Src, and Beta-Arrestin2 Signaling Pathways in Human Bronchial Epithelia

Objective β2-Adrenoceptor agonists are widely used to treat asthma because of their bronchial-dilation effects. We previously reported that isoprenaline, via the apical and basolateral β2-adrenoceptor, induced Cl− secretion by activating cyclic AMP (cAMP)-dependent pathways in human bronchial epithelia. Despite these results, whether and how the β2-adrenoceptor-mediated cAMP-dependent pathway contributes to pro-inflammatory cytokine release in human bronchial epithelia remains poorly understood. Methods We investigated β2-adrenoceptor-mediated signaling pathways involved in the production of two pro-inflammatory cytokines, interleukin (IL)-6 and IL-8, in 16HBE14o- human bronchial epithelia. The effects of isoprenaline or formoterol were assessed in the presence of protein kinase A (PKA), exchange protein directly activated by cAMP (EPAC), Src, and extracellular signal-regulated protein kinase (ERK)1/2 inhibitors. The involvement of β-arrestin2 was examined using siRNA knockdown. Results Isoprenaline and formoterol (both β2 agonists) induced IL-6, but not IL-8, release, which could be inhibited by ICI 118,551 (β2 antagonist). The PKA-specific inhibitor, H89, partially inhibited IL-6 release. Another intracellular cAMP receptor, EPAC, was not involved in IL-6 release. Isoprenaline-mediated IL-6 secretion was attenuated by dasatinib, a Src inhibitor, and PD98059, an ERK1/2 inhibitor. Isoprenaline treatment also led to ERK1/2 phosphorylation. In addition, knockdown of β-arrestin2 by siRNA specifically suppressed cytokine release when a high concentration of isoprenaline (1 mM) was used. Conclusion Our results suggest that activation of the β2-adrenoceptor in 16HBE14o- cells stimulated the PKA/Src/ERK1/2 and/or β-arrestin2 signaling pathways, leading to IL-6 release. Therefore, our data reveal that β2-adrenoceptor signaling plays a role in the immune regulation of human airway epithelia.

Screening of Porcine Innate Immune Adaptor Signaling Revealed Several Anti-PRRSV Signaling Pathways

Porcine reproductive and respiratory syndrome virus (PRRSV) causes PRRS and is known to effectively suppress host innate immunity. The current strategies for controlling PRRSV are limited and complete understanding of anti-PRRSV innate immunity is needed. Here, we utilized nine porcine innate immune signaling adaptors which represent all currently known innate immune receptor signaling pathways for screening of anti-PRRSV activity. The analysis of PRRSV N gene transcription and protein expression both suggested that the multiple ectopic adaptors exhibited varying degrees of anti-PRRSV activities, with TRIF and MAVS most effective. To better quantify the PRRSV replication, the GFP signal of PRRSV from reverse genetics were measured by flow cytometry and similarly varying anti-PRRSV activities by different signaling adaptors were observed. Based on the screening data, and considering the importance of viral nucleic acid in innate immune response, endogenous TRIF, MAVS and STING were selected for further examination of anti-PRRSV activity. Agonist stimulation assay showed that MAVS and STING signaling possessed significant anti-PRRSV activities, whereas siRNA knockdown assay showed that TRIF, MAVS and STING are all involved in anti-PRRSV activity, with TLR3-TRIF displaying discrepancy in anti-PRRSV infection. Nevertheless, our work suggests that multiple pattern recognition receptor (PRR) signaling pathways are involved in anti-PRRSV innate immunity, which may have implications for the development of future antiviral strategies.

EMMPRIN expression is associated with metastatic progression in osteosarcoma

Background Extracellular matrix metalloproteinase inducer (EMMPRIN), a cell-surface glycoprotein, is overexpressed in several cancer types. EMMPRIN induces a metastatic phenotype by triggering the production of matrix metalloproteinase proteins (MMPs) such as MMP1 and MMP2, and vascular endothelial growth factor (VEGF) in cancer cells and the surrounding stromal cells. The purpose of this study was to investigate the expression and role of EMMPRIN in osteosarcoma. Methods The level of EMMPRIN expression was evaluated using reverse transcriptase polymerase chain reaction (RT-PCR) in 6 tumor-derived osteosarcoma cell lines and compared with that in normal osteoblasts. To study the prognostic significance of EMMPRIN expression, immunohistochemistry was carried out in prechemotherapy biopsies of 54 patients. siRNA knockdown of EMMPRIN in SaOS-2 cells was conducted to explore the role of EMMPRIN. To study the role of EMMPRIN in tumor-stromal interaction in MMP production and invasion, co-culture of SaOS-2 cells with osteoblasts and fibroblasts was performed. Osteosarcoma 143B cells were injected into the tail vein of BALB/c mice and lung metastasis was analyzed. Results EMMRIN mRNA expression was significantly higher in 5 of 6 (83%) tumor-derived cells than in MG63 cells. 90% of specimens (50/54) stained positive for EMMPRIN by immunohistochemistry, and higher expression of EMMPRIN was associated with shorter metastasis-free survival (p = 0.023). Co-culture of SaOS-2 with osteoblasts resulted in increased production of pro-MMP2 and VEGF expression, which was inhibited by EMMPRIN-targeting siRNA. siRNA knockdown of EMMPRIN resulted in decreased invasion. EMMPRIN shRNA-transfected 143B cells showed decreased lung metastasis in vivo. Conclusions Our data suggest that EMMPRIN acts as a mediator of osteosarcoma metastasis by regulating MMP and VEGF production in cancer cells as well as stromal cells. EMMPRIN could serve as a therapeutic target in osteosarcoma.

Actin Beta-Like 2 as a New Mediator of Proliferation and Migration in Epithelial Ovarian Cancer

The impact of Actin beta-like 2 (ACTBL2), a novel described actin isoform, on epithelial ovarian cancer (EOC) biology has not been investigated so far. In this study, we analyzed the prognostic and functional significance of ACTBL2 and its regulatory element Nuclear factor of activated T-cells 5 (NFAT5). The expression of ACTBL2 and NFAT5 was examined in tissue microarrays of 156 ovarian cancer patients by immunohistochemistry. Aiming to assess the molecular impact of ACTBL2 on cellular characteristics, functional assays were executed in vitro upon siRNA knockdown of ACTBL2 and NFAT5. ACTBL2 expression was identified as an independent negative prognostic factor for overall survival of EOC patients. EOC cell lines showed a significantly increased mRNA and protein level of ACTBL2 compared to the benign control. In vitro analyses upon siRNA knockdown of ACTBL2 displayed a significantly reduced cellular viability, proliferation and migration. siRNA knockdown of NFAT5 proved a significant molecular interplay by inducing a downregulation of ACTBL2 with a thus resulting concordant alteration in cellular functions, predominantly reflected in a decreased migratory potential of EOC cells. Our results provide significant evidence on the negative prognostic impact of ACTBL2 in EOC, suggesting its crucial importance in ovarian carcinogenesis by modulating cellular motility and proliferation.