Phosphoinositide 3-kinase Akt Research Articles

Targeting the Phosphoinositide-3 (PI3) Kinase Pathway in Breast Cancer

The phosphoinositide-3 kinase (PI3K) pathway has been identified as an important target in breast cancer research for a number of years, but is new to most clinicians responsible for the daily challenges of breast cancer management. In fact, the PI3K pathway is probably one of the most important pathways in cancer metabolism and growth. Mutations in the PI3K pathway are frequent in breast cancer, causing resistance to human epidermal growth factor receptor 2-targeted agents and, possibly, to hormonal agents as well. Available agents that affect the PI3K pathway include monoclonal antibodies and tyrosine kinase inhibitors, as well as PI3K inhibitors, Akt inhibitors, rapamycin analogs, and mammalian target of rapamycin (mTOR) catalytic inhibitors. Multiple PI3K inhibitors are currently under development, including pure PI3K inhibitors, compounds that block both PI3K and mTOR (dual inhibitors), pure catalytic mTOR inhibitors, and inhibitors that block Akt. It is likely that these agents will have to be given in combination with other signal inhibitors because anti-mTOR agents and PI3K inhibitors may result in the activation of compensatory feedback loops that would in turn result in decreased efficacy. This article reviews current data related to the PI3K pathway, its role in breast cancer, the frequency with which PI3K is aberrant in breast cancer, and the potential clinical implications of using agents that target the PI3K pathway.

Phosphoinositide-3-Kinase Inhibition Enhances Radiosensitization of Cervical Cancer In Vivo

Phosphoinositide-3-kinase (PI3K)/Akt pathway is downregulated in several human cancers, and PI3K inhibition can sensitize these cancer cells to radiation. However, no research on cervical cancer in vivo has been reported. The present study further investigated whether PI3K inhibition could sensitize cervical cancer to radiation in vivo. HeLa cells with sustained PI3K activity and Akt phosphorylation were injected subcutaneously into BALB/C nude mice to establish tumor cell xenograft, which were randomly assigned to control, PI3K inhibitor LY294002 alone, radiation alone, or combined LY294002 and radiation group. Akt phosphorylation was detected by Western blotting to evaluate the blocking efficiency on PI3K activity. The radiosensitization of PI3K inhibition was measured by clonogenic assays, apoptosis analysis, and tumor regrowth assays. The combination of LY294002 and radiation resulted in significant and synergistic suppression of cervical cancer cells in a dose-dependent manner in clonogenic assays (P < 0.05), higher ratio of apoptosis cells, and more remarkable reduction of Akt phosphorylation. Tumor regrowth delay curve showed the lowest increase of tumor volume in the combined group (37 days in average) (P = 0.003). Besides, LY294002 (100 mg/kg) alone decreased cell survival and produced xenograft regrowth delay. Phosphoinositide-3-kinase inhibition by LY294002 can synergistically enhance radiation efficacy via dephosphorylation of Akt in cervical cancer, and PI3K inhibition alone can also suppress tumor regrowth. This may provide novel therapeutic opportunities to enhance the effect of radiotherapy against cervical cancer.

FoxO1 regulates Tlr4 inflammatory pathway signalling in macrophages

The macrophage-mediated inflammatory response is a key etiologic component of obesity-related tissue inflammation and insulin resistance. The transcriptional factor FoxO1 is a key regulator of cell metabolism, cell cycle and cell death. Its activity is tightly regulated by the phosphoinositide-3-kinase-AKT (PI3K-Akt) pathway, which leads to phosphorylation, cytoplasmic retention and inactivation of FoxO1. Here, we show that FoxO1 promotes inflammation by enhancing Tlr4-mediated signalling in mature macrophages. By means of chromatin immunoprecipitation (ChIP) combined with massively parallel sequencing (ChIP-Seq), we show that FoxO1 binds to multiple enhancer-like elements within the Tlr4 gene itself, as well as to sites in a number of Tlr4 signalling pathway genes. While FoxO1 potentiates Tlr4 signalling, activation of the latter induces AKT and subsequently inactivates FoxO1, establishing a self-limiting mechanism of inflammation. Given the central role of macrophage Tlr4 in transducing extrinsic proinflammatory signals, the novel functions for FoxO1 in macrophages as a transcriptional regulator of the Tlr4 gene and its inflammatory pathway, highlights FoxO1 as a key molecular adaptor integrating inflammatory responses in the context of obesity and insulin resistance.

Nobiletin, a citrus flavonoid, suppresses invasion and migration involving FAK/PI3K/Akt and small GTPase signals in human gastric adenocarcinoma AGS cells

Nobiletin, a compound isolated from citrus fruits, is a polymethoxylated flavone derivative shown to have anti-inflammatory, antitumor, and neuroprotective properties. This study has investigated that nobiletin exerted inhibitory effects on the cell adhesion, invasion, and migration abilities of a highly metastatic AGS cells under non-cytotoxic concentrations. Data also showed nobiletin could inhibit the activation of focal adhesion kinase (FAK) and phosphoinositide-3-kinase/Akt (PI3K/Akt) involved in the downregulation of the enzyme activities, protein expressions, messenger RNA levels of matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-2 (MMP-9). Also, our data revealed that nobiletin inhibited FAK/PI3K/Akt with concurrent reduction in the protein expressions of Ras, c-Raf, Rac-1, Cdc42, and RhoA by western blotting, whereas the protein level of RhoB increased progressively. Otherwise, nobiletin-treated AGS cells showed tremendously decreased in the phosphorylation and degradation of inhibitor of kappaBα (IκBα), the nuclear level of NF-κB, and the binding ability of NF-κB to NF-κB response element. Furthermore, nobiletin significantly decreased the levels of phospho-Akt and MMP-2/9 in Akt1-cDNA-transfected cells concomitantly with a marked reduction in cell invasion and migration. These results suggest that nobiletin can reduce invasion and migration of AGS cells, and such a characteristic may be of great value in the development of a potential cancer therapy.

Postconditioning with sevoflurane protects against focal cerebral ischemia and reperfusion injury via PI3K/Akt pathway

Emerging evidence has demonstrated that postconditioning with sevoflurane provided neuroprotection. In this study, we investigated the neuroprotective effect of different concentrations of sevoflurane in rats with middle cerebral artery occlusion (MCAO). Furthermore, we tested the hypothesis that the neuroprotective effect of postconditioning with sevoflurane is associated with inhibition of apoptosis and mediated by activation of the phosphoinositide-3-kinase/Akt (PI3K/Akt) pathway. Adult male Sprague–Dawley rats were subjected to MCAO for 90 min and then treated with sevoflurane at the beginning of reperfusion. The infarct volume, neurological deficit scores and brain edema were evaluated at 24 hours. Spatial learning and memory was examined by Morris water maze. Apoptosis and apoptosis-related proteins were studied by TUNEL, immunohistochemistry and western blot. The neuroprotective effect and the amount of p-Akt after sevoflurane administration with or without wortmannin were analyzed. Postconditioning with sevoflurane 1.0 minimum alveolar concentration (MAC) and 1.5 MAC significantly decreased neurological deficit scores, infarct volume and brain edema and markedly improved spatial learning and memory. Postconditioning also reduced apoptotic cells, upregulated Bcl-2 and downregulated P53 and Bax. Wortmannin abolished the neuroprotective effect and prevented the increasing of p-Akt. Our data suggest postconditioning with sevoflurane (1.0 MAC and 1.5 MAC) not only reduced infarct volume but also improved learning and memory. Our study further showed that this neuroprotective effect may be partly due to the activation of PI3K/Akt pathway and inhibiting neuronal apoptosis.

The PI3K–Akt mediates oncogenic Met-induced centrosome amplification and chromosome instability

The oncogenic ability of aberrant hepatocyte growth factor receptor (Met) signaling is thought to mainly rely on its mitogenic and anti-apoptotic effects. Recently, however, cumulating evidences suggest that genomic instability may be a crucial factor in tumorigenesis. Here, we address whether oncogenic Met receptor is linked to the centrosome abnormality and genomic instability. We showed that expression of the constitutive active Met (CA-Met) induced supernumerary centrosomes probably due to deregulated centrosome duplication, which was accompanied with multipolar spindle formation and aneuploidy. Interestingly, LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, significantly suppressed the appearance of supernumerary centrosomes. Moreover, knockdown of Akt with small interfering RNAs and overexpression of phosphatase and tensin homolog or dominant-negative Akt abrogated supernumerary centrosome formation, evidencing the involvement of PI3K signaling. We further showed that expression of CA-Met significantly increased aneuploidy in p53(-/-) HCT116 cells, but not in p53(+/+) HCT116 cells, indicating that the ability of CA-Met to induce chromosomal instability (CIN) phenotype is related with p53 status. Together, our data demonstrate that aberrant hepatocyte growth factor/Met signaling induces centrosome amplification and CIN via the PI3K-Akt pathway, providing an example that oncogenic growth factor signals prevalent in a wide variety of cancers have cross talks to centrosome abnormality and CIN.

Poly(I:C)-Induced Adhesion Molecule Expression Mediated by NF-κB and Phosphoinositide 3-Kinase–Akt Signaling Pathways in Human Corneal Fibroblasts

Viral infection at the ocular surface can lead to the chronic condition of viral stromal keratitis. Polyinosinic-polycytidylic acid [poly(I:C)], an analog of viral double-stranded RNA, induces the expression of adhesion molecules in cultured corneal fibroblasts. The authors investigated the roles of nuclear factor (NF)-κB and phosphoinositide 3-kinase (PI3K)-Akt signaling pathways in the poly(I:C)-induced expression of adhesion molecules in corneal fibroblasts. Human corneal fibroblasts were cultured with poly(I:C) in the absence or presence of IκB kinase 2 (IKK2) inhibitor (an inhibitor of NF-κB activation) or the PI3K inhibitor LY294002. The expression of vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1, ICAM-2, and E-selectin, as well as the phosphorylation of the NF-κB inhibitory protein IκB-α and Akt, were examined by immunoblot analysis. The subcellular localization of adhesion molecules was determined by immunofluorescence analysis. Poly(I:C) increased the expression of VCAM-1 and ICAM-1 but not that of ICAM-2 or E-selectin in corneal fibroblasts. Poly(I:C) also induced the phosphorylation of IκB-α and Akt. The poly(I:C)-induced expression of VCAM-1 and ICAM-1 was attenuated by both IKK2 inhibitor and LY294002. The NF-κB and PI3K-Akt signaling pathways mediate the poly(I:C)-induced upregulation of VCAM-1 and ICAM-1 in corneal fibroblasts, with PI3K acting upstream of NF-κB activation. These pathways thus likely modulate local immune and inflammatory responses to viral infection in the corneal stroma.

Genetic variations of the PI3K-AKT-mTOR pathway and clinical outcome in muscle invasive and metastatic bladder cancer patients

The phosphoinositide-3 kinase (PI3K)-AKT- mammalian target of rapamycin (mTOR) pathway is an important cellular pathway controlling cell growth, tumorigenesis, cell invasion and drug response. We hypothesized that genetic variations in the PI3K-AKT-mTOR pathway may affect the survival in muscle invasive and metastatic bladder cancer (MiM-BC) patients. We conducted a follow-up study of 319 MiM-BC patients to systematically evaluate 289 single-nucleotide polymorphisms (SNPs) of 20 genes in the PI3K-AKT-mTOR pathway as predicators of survival. In multivariate Cox regression, AKT2 rs3730050, PIK3R1 rs10515074 and RAPTOR rs9906827 were significantly associated with survival. In combined analysis, we found a cumulative effect of these three SNPs on survival. With the increasing number of unfavorable genotypes, there was a significant trend of higher risk of death in multivariate Cox regression (P for trend <0.001) and shorter median survival time in Kaplan-Meier estimates (P log rank <0.001). This is the first study to evaluate the role of germ line genetic variations in the PI3K-AKT-mTOR pathway genes as predictors of MiM-BC clinical outcomes. These findings warrant further replication in independent populations and may provide information on disease management and development of target therapies.

PI3K/Akt signaling transduction pathway is involved in rat vascular smooth muscle cell proliferation induced by apelin-13

Vascular smooth muscle cells (VSMCs) were prepared from thoracic aortas of male Sprague-Dawley rats by the explant method to observe VSMC proliferation via phosphoinositide 3 kinase (PI3K)/Akt signaling transduction pathway induced by apelin-13. Expression of PI3K, phospho-PI3K, phospho-Akt, ERK1/2, phospho-ERK1/2 and cyclin D1 was detected by western blot analysis. Results showed that apelin-13 promoted the expression of phospho-PI3K and phospho-Akt in dose- and timedependent manner. PI3K inhibitor LY294002 significantly decreased the expression of phospho-PI3K, phospho-Akt, phospho-ERK1/2, and cyclin D1 induced by apelin-13. The Akt inhibitor 1701-1 significantly diminished the expression of phospho-Akt, phospho-ERK1/2, and cyclin D1 stimulated by apelin-13. MTT assay results showed that PI3K inhibitor LY294002 and Akt inhibitor 1701-1 significantly inhibited the VSMC proliferation induced by apelin-13. Apelin-13 promoted VSMC proliferation through PI3K/Akt signaling transduction pathway.

Suppression of Akt1 phosphorylation by adenoviral transfer of the PTEN gene inhibits hypoxia-induced proliferation of rat pulmonary arterial smooth muscle cells

Recent findings identify the role of proliferation of pulmonary artery smooth muscle cells (PASMCs) in pulmonary vascular remodeling. Phosphoinositide 3 kinase (PI3K) and serine/threonine kinase (Akt) proteins are expressed in vascular smooth muscle cells. In addition, phosphatase and tensin homolog deleted on chromosome 10 (PTEN) has been identified as a negative regulator of cytokine signaling that inhibits the PI3K–Akt pathway. However, little is known about the role of PTEN/Akt signaling in hypoxia-associated vascular remodeling. In this study, we found that hypoxia-induced the expression of Akt1 mRNA and phosphorylated protein by at least twofold in rat PASMCs. Phospho-PTEN significantly decreased in the nuclei of PASMCs after hypoxic stimulation. After forcing over-expression of PTEN by adenovirus-mediated PTEN (Ad-PTEN) transfection, the expression of phospho-Akt1 was significantly suppressed in PASMCs at all time-points measured. Additionally, we showed here that hypoxia increased proliferation of PASMCs by nearly twofold and over-expression of PTEN significantly inhibited hypoxia-induced PASMCs proliferation. These findings suggest that phospho-PTEN loss in the nuclei of PASMCs under hypoxic conditions may be the major cause of aberrant activation of Akt1 and may, therefore, play an important role in hypoxia-associated pulmonary arterial remodeling. Finally, the fact that transfection with Ad-PTEN inhibits the phosphorylation of Akt1 in PASMCs suggests a potential therapeutic effect on hypoxia-associated pulmonary arterial remodeling.

Abstract 301: Galectin-1 modulates PI3 kinase activity

Abstract The purpose of these experiments was to study the role that Galectin-1 (GAL1) has in Phosphoinositide 3-kinase (PI3K) signaling. GAL1 protein levels have been identified to be significantly upregulated in gliomas. GAL1 levels have also been closely associated with patient survival. The PI3K enzyme converts phosphatidylinositol 4,5-bisphosphate (PIP2) to phosphatidylinositol (3,4,5)-trisphosphate (PIP3). PIP3 serves as a membrane anchor leading to the activation of AKT. PI3K/AKT signaling is important in cancer cell biology because induction of this pathway is associated with increased cell survival, cell cycle progression, and growth. A PIP3 Mass ELISA was performed on cell lysates isolated from wild type (WT) and GAL1 knockdown cells with and without Inslulin-like growth factor 1 (IGF1) stimulation. Briefly, cells were stimulated with 5mM IGF1 followed by cell lysis. Lysates were compared by ELISA for PIP3 levels. Following this an in vitro PI3K assay was done. This assay is designed to measure the activity of a purified PI3K enzyme by detecting PIP2 to PIP3 conversion. Enzyme was incubated with Gal1 alone, LY294002 PI3K inhibitor, or with both Gal1 and the inhibitor. Controls included enzyme only, enzyme with inhibitor, no enzyme, and no substrate. In order to investigate whether a physical interaction was occurring between Gal1 and PI3K, Co-IP experiments were performed. These experiments involved isolation of cell lysates from WT LN229 cells and GAL1 knockdown LN229 cells. Following pulldown, Co-IP's were run on an SDS-PAGE gel, transferred to blots, and probed for GAL1 and p85 α or β. Previous experiments demonstrated a possible role for GAL1 in PI3K signaling and AKT activation. In the PIP3 mass ELISA experiment, WT cells demonstrated elevated cellular PIP3 levels in response to IGF1 stimulation, as expected. GAL1 knockdown cells did not show any increase in PIP3 levels in response to stimulation. We next examined if GAL1 was having a direct effect on PI3K activity. In vitro PI3K reactions showed a specific upregulation of PI3K activity in response to addition of GAL1. In response to 1000-fold changes in GAL1 concentration there was an approximate 2-fold increase in PI3K (p85α/p110α) activity. GAL1 also demonstrated an ability to overcome LY294002 inhibition of the enzyme. Enzyme incubated with both inhibitor and 5uM GAL1 showed 4 times the conversion as compared to enzyme with inhibitor alone. Interaction studies indicate that there is not a physical interaction between GAL1 and either p85 α or β. Future studies characterizing the role of GAL1 in PI3K signaling include repeating the PI3K assay with other PI3K class I isoforms to examine differences. Fluorescence Resonance Energy Transfer (FRET) experiments will also be performed to further test for a physical interaction between PI3K and GAL1. In conclusion GAL1 has demonstrated an ability to effect PI3K activity, and thereby PI3K signaling. However, a physical interaction between GAL1 and PI3K was not observed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 301.

FGFR1 Amplification Drives Endocrine Therapy Resistance and Is a Therapeutic Target in Breast Cancer

Amplification of fibroblast growth factor receptor 1 (FGFR1) occurs in approximately 10% of breast cancers and is associated with poor prognosis. However, it is uncertain whether overexpression of FGFR1 is causally linked to the poor prognosis of amplified cancers. Here, we show that FGFR1 overexpression is robustly associated with FGFR1 amplification in two independent series of breast cancers. Breast cancer cell lines with FGFR1 overexpression and amplification show enhanced ligand-dependent signaling, with increased activation of the mitogen-activated protein kinase and phosphoinositide 3-kinase-AKT signaling pathways in response to FGF2, but also show basal ligand-independent signaling, and are dependent on FGFR signaling for anchorage-independent growth. FGFR1-amplified cell lines show resistance to 4-hydroxytamoxifen, which is reversed by small interfering RNA silencing of FGFR1, suggesting that FGFR1 overexpression also promotes endocrine therapy resistance. FGFR1 signaling suppresses progesterone receptor (PR) expression in vitro, and likewise, amplified cancers are frequently PR negative, identifying a potential biomarker for FGFR1 activity. Furthermore, we show that amplified cancers have a high proliferative rate assessed by Ki67 staining and that FGFR1 amplification is found in 16% to 27% of luminal B-type breast cancers. Our data suggest that amplification and overexpression of FGFR1 may be a major contributor to poor prognosis in luminal-type breast cancers, driving anchorage-independent proliferation and endocrine therapy resistance.

MK-2461, a Novel Multitargeted Kinase Inhibitor, Preferentially Inhibits the Activated c-Met Receptor

The receptor tyrosine kinase c-Met is an attractive target for therapeutic blockade in cancer. Here, we describe MK-2461, a novel ATP-competitive multitargeted inhibitor of activated c-Met. MK-2461 inhibited in vitro phosphorylation of a peptide substrate recognized by wild-type or oncogenic c-Met kinases (N1100Y, Y1230C, Y1230H, Y1235D, and M1250T) with IC(50) values of 0.4 to 2.5 nmol/L. In contrast, MK-2461 was several hundredfold less potent as an inhibitor of c-Met autophosphorylation at the kinase activation loop. In tumor cells, MK-2461 effectively suppressed constitutive or ligand-induced phosphorylation of the juxtamembrane domain and COOH-terminal docking site of c-Met, and its downstream signaling to the phosphoinositide 3-kinase-AKT and Ras-extracellular signal-regulated kinase pathways, without inhibiting autophosphorylation of the c-Met activation loop. BIAcore studies indicated 6-fold tighter binding to c-Met when it was phosphorylated, suggesting that MK-2461 binds preferentially to activated c-Met. MK-2461 displayed significant inhibitory activities against fibroblast growth factor receptor (FGFR), platelet-derived growth factor receptor, and other receptor tyrosine kinases. In cell culture, MK-2461 inhibited hepatocyte growth factor/c-Met-dependent mitogenesis, migration, cell scatter, and tubulogenesis. Seven of 10 MK-2461-sensitive tumor cell lines identified from a large panel harbored genomic amplification of MET or FGFR2. In a murine xenograft model of c-Met-dependent gastric cancer, a well-tolerated oral regimen of MK-2461 administered at 100 mg/kg twice daily effectively suppressed c-Met signaling and tumor growth. Similarly, MK-2461 inhibited the growth of tumors formed by s.c. injection of mouse NIH-3T3 cells expressing oncogenic c-Met mutants. Taken together, our findings support further preclinical development of MK-2461 for cancer therapy.

Akt-Mediated Phosphorylation of Bmi1 Regulates Its Chromatin Association and Growth Promoting Properties.

Abstract 3605Poster Board III-541The Polycomb group (PcG) protein Bmi1 maintains silencing of the Ink4a-Arf locus and plays a key role in stem cell self-renewal and oncogenesis. The phosphoinositide 3-kinase-Akt (PI3K-Akt) signaling pathway regulates cell survival, growth, metabolism, migration and angiogenesis. In response to acute Pten loss (which results in Akt activation), mouse embryonic fibroblasts (mefs) accumulate p16Ink4a and p19Arf and undergo senescence. Similarly, Bmi1 −/− mefs undergo premature senescence and accumulate p16Ink4a and p19Arf. PTEN and Bmi1 have similar effects on hematopoiesis; Pten deletion promotes hematopoietic stem cell (HSC) proliferation, resulting in HSC depletion, whereas loss of Bmi1 impairs HSC self-renewal capability, also leading to bone marrow failure. These similarities led us to examine whether the PI3K/Akt pathway functions upstream of Bmi1 to negatively regulate its function and indeed we found that PKB/Akt phosphorylates Bmi1 in vivo, which results in its dissociation from chromatin and in de-repression of the Ink4a-Arf locus. Furthermore, activation of the PI3K/Akt pathway suppresses the ability of Bmi1 to promote cell growth and tumourigenesis and decreases the global level of histone H2A ubiquitination. PI3K/Akt signaling is not active in hematopoietic stem cells, but it is active in more committed progenitor cells. Thus, phosphorylation and inactivation of Bmi1 by Akt may limit HSC self-renewal. Our study also provides a mechanism for the upregulation of p16Ink4a and p19Arf seen in cancer cells that have activation of the PI3K/Akt signaling pathway, and identifies important crosstalk between phosphorylation and chromatin structure. Disclosures:No relevant conflicts of interest to declare.

Hepatitis C virus NS5A protein interacts with -catenin and stimulates its transcriptional activity in a phosphoinositide-3 kinase-dependent fashion

Hepatitis C virus (HCV) infection is increasingly associated with the development of hepatocellular carcinoma (HCC). HCV is not thought to be directly oncogenic but, by modulating a range of cellular functions, may predispose patients to the development of liver tumours. However, the molecular mechanisms by which HCV infection might contribute to HCC remain to be characterized. In this regard, we showed previously that the HCV NS5A protein bound to the p85 regulatory subunit of phosphoinositide-3 kinase (PI3K), thereby stimulating the activity of the p110 catalytic subunit of the enzyme. One of the downstream consequences of this was the stabilization of the proto-oncogene, beta-catenin, with a concomitant stimulation of its transcriptional activity. Here, we further analyse the mechanism by which NS5A mediates activation of beta-catenin. Although our previous data were consistent with a role for the PI3K downstream effector kinases, Akt and glycogen synthase kinase-3beta, in NS5A-mediated activation of beta-catenin, we demonstrate here that it is in fact independent of both of these kinases. Truncation analysis revealed that both the N and C termini of NS5A are required for full activation of beta-catenin. Furthermore, we demonstrate that NS5A, either alone or in complex with p85, is able to bind directly to beta-catenin; again both N and C termini contribute to this interaction. We propose that NS5A activates beta-catenin via a novel mechanism that involves a direct interaction between the two proteins and is augmented by PI3K activity. This may contribute to the association between chronic HCV infection and the development of HCC.

The role of phosphoinositide-3-kinase/Akt pathway in propofol-induced postconditioning against focal cerebral ischemia-reperfusion injury in rats

The aim of this study was to investigate whether propofol could provide postconditioning to ischemic brain injury and the role of phosphoinositide-3-kinase/Akt (PI3K/Akt) pathway in this phenomenon. Rats underwent 2 h of middle cerebral artery occlusion (MCAO) followed by 22 h of reperfusion were randomly divided into nine groups ( n = 15 each): sham-operated group, MCAO group, propofol 10, 20 and 35 mg·kg − 1 ·h − 1 group (propofol 10, 20, 35 mg·kg − 1 ·h − 1 infused at the onset of reperfusion for 30 min), wortmannin group (wortmannin 0.6 mg/kg administered 30 min before MCAO), and the other three groups received wortmannin followed by 10, 20 and 35 mg·kg − 1 ·h − 1 propofol respectively. Propofol at doses of 10 and 20 mg·kg − 1 ·h − 1 significantly reduced infarct volume, decreased neurological deficit scores and attenuated neuron apoptosis compared with MCAO group alone. Increased phosphorylated Akt (P-Akt) was observed in the ischemic penumbra of propofol 10 and 20 mg·kg − 1 ·h − 1 group after transient MCAO. The selective PI3K inhibitor, wortmannin partly eliminated the neuroprotective effect and the elevation of P-Akt expression in ischemic penumbra induced by propofol. Propofol at dose of 35 mg·kg − 1 ·h − 1 did not affect infarct volume, neurological deficit scores, neuronal apoptosis and the level of P-Akt in transient MCAO rats. Taken together, these results demonstrated that propofol at doses of 10 or 20 mg·kg − 1 ·h − 1 infused at the onset of reperfusion for 30 min could provide neuroprotection to transient MCAO rats, and the postconditioning effect induced by propofol partly through maintaining the activity of PI3K/Akt pathway.

Roles of MKK1/2-ERK1/2 and Phosphoinositide 3-Kinase–AKT Signaling Pathways in Erlotinib-Induced Rad51 Suppression and Cytotoxicity in Human Non–Small Cell Lung Cancer Cells

Erlotinib (Tarceva) is a selective epidermal growth factor receptor tyrosine kinase inhibitor in the treatment of human non-small cell lung cancer (NSCLC). In this study, we investigated the roles of ERK1/2 and AKT signaling pathways in regulating Rad51 expression and cytotoxic effects in different NSCLC cell lines treated with erlotinib. Erlotinib decreased cellular levels of phosphorylated ERK1/2, phosphorylated AKT, Rad51 protein, and mRNA in erlotinib-sensitive H1650, A549, and H1869 cells, leading to cell death via apoptosis, but these results were not seen in erlotinib-resistant H520 and H1703 cells. Erlotinib decreased Rad51 protein levels by enhancing Rad51 mRNA and protein instability. Enforced expression of constitutively active MKK1 or AKT vectors could restore Rad51 protein levels, which were inhibited by erlotinib, and decrease erlotinib-induced cytotoxicity. Knocking down endogenous Rad51 expression by si-Rad51 RNA transfection significantly enhanced erlotinib-induced cytotoxicity. In contrast, overexpression of Rad51 by transfection with Rad51 vector could protect the cells from cytotoxic effects induced by erlotinib. Blocking the activations of ERK1/2 and AKT by MKK1/2 inhibitor (U0126) and phosphoinositide 3-kinase inhibitor (wortmannin) suppressed the expression of Rad51 and enhanced the erlotinib-induced cell death in erlotinib-resistant cells. In conclusion, suppression of Rad51 may be a novel therapeutic modality in overcoming drug resistance of erlotinib in NSCLC.

In vitro enhancement effect of humic acid on the progression of lung cancer cells

Humic acid, a group of polymer, resulting from the decomposition of organic matter has been implicated as a possible etiological factor for Black foot disease and cancer. However, the role of humic acid in carcinogenesis is not well clarified. In this study, we evaluated the enhancement effect of humic acid on the progression of A549 human lung cancer cells. Our findings showed that humic acid increased the migration, adhesion and invasion of A549 cells significantly after treatment at the concentration of 50 and 100 μg/ml for 24 and 48 h as compared with the untreated group. Results of zymography assay indicated that humic acid enhanced the activity of matrix metalloproteinase 9 (MMP-9). By western blotting analysis, humic acid increased the expression of phosphorylated focal adhesion kinase (FAK) and integrin α2 that may mediate cell motility and adhesion. Since the activation of signal pathways such as phosphoinositide 3-kinase/Akt (PI3K/Akt) and mitogen-activated protein kinases (MAPKs) may play a role in the cell invasion, we detected the expression of phosphorylated Akt and phosphorylated MAPKs including extracellular signal-regulated kinase (ERK), Jun N-terminus kinase (JNK), and p38. The result indicated that all kinases stated above were activated by humic acid in A549 cells. However, by adding an inhibitor respectively in the invasion assay, only Akt, ERK, and JNK pathways were found to be involved in the enhancing the invasion of A549 cells by humic acid. In addition, results of electrophoretic mobility shift assay (EMSA) demonstrated that humic acid increased nuclear extract binding to the DNA probe of activator protein 1 (AP-1) and nuclear factor κB (NFκB) respectively, implying that humic acid enhanced the progression of A549 lung cancer cells through activating multiple signaling pathways including ERK, JNK, and PI3K/Akt and increasing the transcription activation of AP-1 and NFκB.

Antimetastatic potential of fisetin involves inactivation of the PI3K/Akt and JNK signaling pathways with downregulation of MMP-2/9 expressions in prostate cancer PC-3 cells

Fisetin (3,3',4',7-tetrahydroxyflavone), a naturally occurring flavonoid, has been reported to possess some anti-cancer and anti-inflammation capabilities. In this study, fisetin has exhibited inhibitory effects on the adhesion, migration, and invasion ability of a highly metastatic PC-3 cells under non-cytotoxic concentrations. Gelatin zymography assay showed that fisetin inhibited the matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) activities. Our result also showed that fisetin could inhibit the phosphorylation of c-Jun N-terminal kinase 1 and 2 (JNK1/2) and Akt. Moreover, fisetin significantly decreased the nuclear levels of nuclear factor kappa B (NF-kappaB), c-Fos, and c-Jun, and the binding abilities of NF-kappaB and activator protein-1 (AP-1). Also, the results showed that the protein and mRNA levels of MMP-2 and MMP-9 were significantly reduced by Western blot and semi-quantitative RT-PCR. Further, treating specific inhibitors for PI3K (Wortmannin) or JNK (SP600125) to PC-3 cells could reduce the protein expressions of MMP-2 and MMP-9. These results showed fisetin could inhibit the metastatic ability of PC-3 by reducing MMP-2 and MMP-9 expressions through suppressing phosphoinositide 3-kinase/Akt (PI3K/Akt) and JNK signaling pathways. This suggested fisetin can serve as a potential candidate for treating cancer metastasis.

Mal connects TLR2 to PI3Kinase activation and phagocyte polarization.

The recognition of bacterial lipoproteins by toll-like receptor (TLR) 2 is pivotal for inflammation initiation and control in many bacterial infections. TLR2-dependent signalling is currently believed to essentially require both adaptor proteins MyD88 (myeloid differentiation primary response gene 88) and Mal/TIRAP (MyD88-adapter-like/TIR-domain-containing adaptor protein). TLR2-dependent, but MyD88-independent responses have not been described yet. We report here on a novel-signalling pathway downstream of TLR2, which does not adhere to the established model. On stimulation of the TLR2/6 heterodimer with diacylated bacterial lipoproteins, Mal directly interacts with the regulatory subunit of phosphoinositide 3-kinase (PI3K), p85alpha, in an inducible fashion. The Mal-p85alpha interaction drives PI3K-dependent phosphorylation of Akt, phosphatidylinositol(3,4,5)P3 (PIP(3)) generation and macrophage polarization. MyD88 is not essential for PI3K activation and Akt phosphorylation; however, cooperates with Mal for PIP(3) formation and accumulation at the leading edge. In contrast to TLR2/6, TLR2/1 does not require Mal or MyD88 for Akt phosphorylation. Hence, Mal specifically connects TLR2/6 to PI3K activation, PIP(3) generation and macrophage polarization.