PI3K P85 Research Articles

Guava (Psidium guajava Linn.) leaf extract promotes glucose uptake and glycogen accumulation by modulating the insulin signaling pathway in high-glucose-induced insulin-resistant mouse FL83B cells

The effects of aqueous guava leaf extract (GvEx) on insulin resistance were evaluated in high glucose-induced insulin-resistant mouse FL83B cells. Glucose uptake and glycogen content were determined and western blot analysis was performed to study the anti-diabetic effects of GvEx. Our results showed that administration of 200 and 400μg/mL GvEx resulted in a significant increase in glucose uptake in both normal and insulin-resistant cells. Glycogen content in cells was significantly higher after incubation with GvEx (200, 400μg/mL) than that in control group (p<0.05). Further, western blot analysis revealed that 200 and 400μg/mL GvEx significantly enhanced the levels of insulin-related signaling components, including insulin receptor (IR), as well as enhancing the phosphorylation of the insulin receptor (p-IR (Tyr)), insulin receptor substrate (p-IRS (Tyr)), p85 regulatory subunit of phospho-inositide 3 kinase (PI3K (p85)), protein kinase B (p-Akt (Ser)), glucose transporter 2 (Glut 2), and total glycogen synthase. In conclusion, GvEx improved insulin resistance by promoting glucose uptake and enhancing glycogen content via modulation of the insulin signaling pathway in high glucose-induced insulin-resistant mouse FL83B cells.

Idelalisib: First-in-Class PI3K Delta Inhibitor for the Treatment of Chronic Lymphocytic Leukemia, Small Lymphocytic Leukemia, and Follicular Lymphoma.

Idelalisib [Zydelig (Gilead Sciences, Inc.), also known as CAL-101 and GS-1101] was approved in 2014 in the United States and European Union for the treatment of three indolent B-cell neoplasms: relapsed/refractory chronic lymphocytic leukemia (CLL, in combination with rituximab), relapsed follicular lymphoma, and relapsed small lymphocytic lymphoma (as monotherapy). Furthermore, it was approved in the European Union as first-line therapy for poor-prognosis CLL with 17p deletions or TP53 mutations and in patients unsuitable for chemoimmunotherapy. Idelalisib is an orally bioavailable ATP-competitive kinase inhibitor that targets the PI3K p110 isoform δ (PI3Kδ) with high potency and selectivity. PI3Kδ is hyperactivated in B-cell malignancies and plays a pivotal role in the B-cell receptor pathway, a key oncogenic driver in B-cell malignancies. The near exclusive expression of the PI3Kδ isoform in hematopoietic cells and the selectivity of idelalisib for the PI3Kδ isoform are essential for its efficacy and tolerability, even in elderly patients unfit for chemotherapy. Idelalisib is the first PI3K inhibitor approved by the regulatory agencies; this approval will change the treatment landscape of indolent B-cell malignancies.

Coffee and caffeine potentiate the antiamyloidogenic activity of melatonin via inhibition of Aβ oligomerization and modulation of the Tau-mediated pathway in N2a/APP cells.

There is an increasing prevalence of Alzheimer’s disease (AD), which has become a public health issue. However, the underlying mechanisms for the pathogenesis of AD are not fully understood, and the current therapeutic drugs cannot produce acceptable efficacy in AD patients. Previous animal studies have shown that coffee (Coff), caffeine (Caff), and melatonin (Mel) have beneficial effects on AD. Disturbed circadian rhythms are observed in AD, and chronotherapy has shown promising effects on AD. In this study, we examined whether a combination of Coff or Caff plus Mel produced a synergistic/additive effect on amyloid-β (Aβ) generation in Neuro-2a (N2a)/amyloid precursor protein (APP) cells and the possible mechanisms involved. Cells were treated with Coff or Caff, with or without combined Mel, with three different chronological regimens. In regimen 1, cells were treated with Coff or Caff for 12 hours in the day, followed by Mel for 12 hours in the night. For regimen 2, cells were treated with Coff or Caff plus Mel for 24 hours, from 7 am to 7 am the next day. In regimen 3, cells were treated with Coff or Caff plus Mel with regimen 1 or 2 for 5 consecutive days. The extracellular Aβ40/42 and Aβ oligomer levels were determined using enzyme-linked immunosorbent assay (ELISA) kits. The expression and/or phosphorylation levels of glycogen synthase kinase 3β (GSK3β), Erk1/2, PI3K, Akt, Tau, Wnt3α, β-catenin, and Nrf2 were detected by Western blot assay. The results showed that regimen 1 produced an additive antiamyloidogenic effect with significantly reduced extracellular levels of Aβ40/42 and Aβ42 oligomers. Regimen 2 did not result in remarkable effects, and regimen 3 showed a less antiamyloidogenic effect compared to regimen 1. Coff or Caff, plus Mel reduced oxidative stress in N2a/APP cells via the Nrf2 pathway. Coff or Caff, plus Mel inhibited GSK3β, Akt, PI3K p55, and Tau phosphorylation but enhanced PI3K p85 and Erk1/2 phosphorylation in N2a/APP cells. Coff or Caff, plus Mel downregulated Wnt3α expression but upregulated β-catenin. However, Coff or Caff plus Mel did not significantly alter the production of T helper cell (Th)1-related interleukin (IL)-12 and interferon (IFN)-γ and Th2-related IL-4 and IL-10 in N2a/APP cells. The autophagy of cells was not affected by the combinations. Taken together, combination of Caff or Coff, before treatment with Mel elicits an additive antiamyloidogenic effects in N2a/APP cells, probably through inhibition of Aβ oligomerization and modulation of the Akt/GSK3β/Tau signaling pathway.

Glimepiride promotes osteogenic differentiation in rat osteoblasts via the PI3K/Akt/eNOS pathway in a high glucose microenvironment.

Our previous studies demonstrated that glimepiride enhanced the proliferation and differentiation of osteoblasts and led to activation of the PI3K/Akt pathway. Recent genetic evidence shows that endothelial nitric oxide synthase (eNOS) plays an important role in bone homeostasis. In this study, we further elucidated the roles of eNOS, PI3K and Akt in bone formation by osteoblasts induced by glimepiride in a high glucose microenvironment. We demonstrated that high glucose (16.5 mM) inhibits the osteogenic differentiation potential and proliferation of rat osteoblasts. Glimepiride activated eNOS expression in rat osteoblasts cultured with two different concentrations of glucose. High glucose-induced osteogenic differentiation was significantly enhanced by glimepiride. Down-regulation of PI3K P85 levels by treatment with LY294002 (a PI3K inhibitor) led to suppression of P-eNOS and P-AKT expression levels, which in turn resulted in inhibition of RUNX2, OCN and ALP mRNA expression in osteoblasts induced by glimepiride at both glucose concentrations. ALP activity was partially inhibited by 10 µM LY294002. Taken together, our results demonstrate that glimepiride-induced osteogenic differentiation of osteoblasts occurs via eNOS activation and is dependent on the PI3K/Akt signaling pathway in a high glucose microenvironment.

FOXO1 content is reduced in cystic fibrosis and increases with IGF-I treatment.

Cystic fibrosis-related diabetes is to date the most frequent complication in cystic fibrosis (CF). The mechanisms underlying this condition are not well understood, and a possible role of insulin resistance is debated. We investigated insulin signal transduction in CF. Total insulin receptor, IRS1, p85 PI3K, and AKT contents were substantially normal in CF cells (CFBE41o-), whereas winged helix forkhead (FOX)O1 contents were reduced both in baseline conditions and after insulin stimulation. In addition, CF cells showed increased ERK1/2, and reduced β2 arrestin contents. No significant change in SOCS2 was observed. By using a CFTR inhibitor and siRNA, changes in FOXO1 were related to CFTR loss of function. In a CF-affected mouse model, FOXO1 content was reduced in the muscle while no significant difference was observed in liver and adipose tissue compared with wild-type. Insulin-like growth factor 1 (IGF-I) increased FOXO1 content in vitro and in vivo in muscle and adipose tissue. In conclusion; we present the first description of reduced FOXO1 content in CF, which is compatible with reduced gluconeogenesis and increased adipogenesis, both features of insulin insensitivity. IGF-I treatment was effective in increasing FOXO1, thereby suggesting that it could be considered as a potential treatment in CF patients possibly to prevent and treat cystic fibrosis-related diabetes.

Berberine hydrochloride IL-8 dependently inhibits invasion and IL-8-independently promotes cell apoptosis in MDA-MB-231 cells.

Breast cancer, the leading cause of cancer-related mortality worldwide in females, has high metastastic and recurrence rates. The aim of the present study was to evaluate the anti-metastatic and anticancer in situ effect of berberine hydrochloride (BER) in MDA-MB-231 cells. BER dose-dependently inhibited proliferation and the IL-8 secretion of MDA-MB-231 cells. Additional experiments revealed that the inactivation of PI3K, JAK2, NF-κB and AP-1 by BER contributed to the decreased IL-8 secretion. BER abrogated cell invasion induced by IL-8 accompanied with the downregulation of the gene expression of MMP-2, EGF, E-cadherin, bFGF and fibronectin. In addition, BER reduced cell motility but induced G2/M arrest and cell apoptosis in an IL-8‑independent manner. BER modulated multiple signaling pathway molecules involved in the regulation of cell apoptosis, including activation of p38 MAPK and JNK and deactivation of JAK2, p85 PI3K, Akt and NF-κB. The enhanced cell apoptosis induced by BER was eliminated by inhibitors of p38 MAPK and JNK but was strengthened by activator of p38 MAPK. Thus, BER inhibited cell metastasis partly through the IL-8 mediated pathway while it induced G2/M arrest and promoted cell apoptosis through the IL-8 independent pathway. Apoptosis induced by BER was mediated by crosstalks of various pathways including activation of p38 MAPK and JNK pathways and inactivation of Jak2/PI3K/NF-κB/AP-1 pathways. The results suggested that BER may be an efficient and safe drug candidate for treating highly metastatic breast cancer.

P38 MAPK and ERK1/2 pathways are involved in the pro-apoptotic effect of notoginsenoside Ft1 on human neuroblastoma SH-SY5Y cells

AimsThis study aims to investigate the effect and the mechanisms of notoginsenoside Ft1, a natural compound exclusively found in P. notoginseng, on the proliferation and apoptosis of human neuroblastoma SH-SY5Y cells. Main methodsCCK-8 assay was used to assess the cell proliferation. Flow cytometry was performed to measure the cell cycle distribution and cell apoptosis. Hoechst 33258 staining was conducted to confirm the morphological changes of apoptotic cells. Protein expression was detected by western blot analysis and caspase 3 activity was measured by colorimetric assay kit. Key findingsAmong the saponins examined, Ft1 showed the best inhibitory effect on cell proliferation of SH-SY5Y cells with IC50 of 45μM. Ft1 not only arrested the cell cycle at S, G2/M stages, but also promoted cell apoptosis, which was confirmed by Hoechst 33258 staining. Further studies demonstrated that Ft1 up-regulated the protein expressions of cleaved caspase 3, phospho-p53, p21, and cyclin B1, but down-regulated that of Bcl-2. Moreover, Ft1 enhanced the phosphorylation of ERK1/2, JNK and p38 MAPK. However, the phosphorylation of Jak2 and p85 PI3K was reduced by Ft1. Inhibitors of p38 MAPK and ERK1/2 but not JNK abrogated the up-regulated protein expressions of cleaved caspase 3, p21 and down-regulated protein expression of Bcl-2 as well as elevated caspase 3 activity induced by Ft1. SignificanceFt1 arrested the proliferation and elicited the apoptosis of SH-SY5Y cells possibly via p38 MAPK and ERK1/2 pathways, which indicates the potential therapeutic effect of it on human neuroblastoma.

Biologically active leptin-related synthetic peptides activate STAT3 via phosphorylation of ERK1/2 and PI-3K

The effects of leptin-related synthetic peptides [d-Leu-4]-OB3 and OB3 on energy balance and glucose homeostasis in ob/ob and db/db mice have been confirmed. The molecular basis of these effects, however, remains unclear. In the present study, we examined the ability of these peptides to activate signal transduction pathways known to be involved in transduction of the leptin signal. In a specific and concentration-dependent manner, [d-Leu-4]-OB3 induced phosphorylation of ERK1/2, PI-3K, Ser-727 STAT3, and Tyr-705 of STAT3. OB3 also induced activation of STAT3 via phosphorylation of ERK1/2, STAT3 Ser-727, STAT3 Tyr-705 and PI-3K p85, but to a lesser degree. Using PD98059 and LY294002, specific inhibitors of MEK and PI-3K, respectively, we were able to identify the signal transduction pathways involved in peptide-induced STAT3 activation. [d-Leu-4]-OB3 induced serine phosphorylation of STAT3 primarily through activation of ERK1/2. Tyrosine phosphorylation of STAT3, however, was induced primarily through activation of PI-3K. Our data suggest that in db/db mice, [d-Leu-4]-OB3 binding to short isoforms of the leptin receptor induces intracellular signaling cascades which do not require OB-Rb activation. These signals may ultimately result in peptide effects on transcriptional and translational events associated with energy balance and glycemic regulation. In summary, we have shown for the first time that, similar to leptin, bioactive leptin-related synthetic peptide analogs activate STAT3 via phosphorylation of serine and tyrosine residues by multiple signal transduction pathways.

TAT-protein blockade during ischemia/reperfusion reveals critical role for p85 PI3K-PTEN interaction in cardiomyocyte injury.

Recent work shows that cooling protection after mouse cardiac arrest and cardiomyocyte ischemia is mediated by Akt activation. The PI3K p85 subunit can either augment or inhibit Akt activation depending on its binding to p110 or PTEN respectively. To further clarify the role of PI3K p85 in cardioprotection, we studied novel TAT-p85 fusion proteins that selectively inhibit PI3K p85 binding. We hypothesized that TAT fused p85 lacking the PTEN binding site (TAT-ΔPTEN p85) would enhance Akt phosphorylation to afford cardioprotection. Conversely, TAT fused p85 lacking the p110 binding site (TAT-Δp110p85) would decrease Akt phosphorylation and abrogate cardioprotection. Microscopy and Western blot analysis demonstrated that TAT fusion protein was transduced into cardiomyocytes within 5 min and remained more than 2 h. Inhibition of PI3K/Akt by TAT-Δp110 p85 significantly increased cell death from 44.6±2.7% to 92.5±3.4% after simulated ischemia and reperfusion. By contrast, PTEN inhibition using TAT-ΔPTEN p85 decreased cell death to 11.9±5.3%, a similar level of cardioprotection seen with past cooling studies. Additional studies with the small molecule PTEN inhibitor VO-OHpic confirmed that PTEN inhibition was highly protective against cell death induced by ischemia and reperfusion. We conclude that blockade of p85-PTEN interaction and PTEN inhibition may be promising strategies for rescuing the heart from ischemia and reperfusion injury.

Phosphorylation of c-Cbl and p85 PI3K driven by all-trans retinoic acid and CD38 depends on Lyn kinase activity

The leukocyte antigen CD38 is expressed after all-trans retinoic acid (ATRA) treatment in HL-60 myelogenous leukemia cells and promotes induced myeloid differentiation when overexpressed. We found that Vav1 and SLP-76 associate with CD38 in two cell lines, and that these proteins complex with Lyn, a Src family kinase (SFK) upregulated by ATRA. SFK inhibitors PP2 and dasatinib, which enhance ATRA-induced differentiation, were used to evaluate the involvement of Lyn kinase activity in CD38-driven signaling. Cells treated with ATRA for 48h followed by one hour of PP2 incubation show SFK/Lyn kinase inhibition. We observed that Lyn inhibition blocked c-Cbl and p85/p55 PI3K phosphorylation driven by the anti-CD38 agonistic mAb IB4 in ATRA-treated HL-60 cells and untreated CD38+ transfectants. In contrast, cells cultured for 48h following concurrent ATRA and PP2 treatment did not show Lyn inhibition, suggesting ATRA regulates the effects on Lyn. 48h of co-treatment preserved CD38-stimulated c-Cbl and p85/p55 PI3K phosphorylation indicating Lyn kinase activity is necessary for these events. In contrast another SFK inhibitor (dasatinib) which blocks Lyn activity with ATRA co-treatment prevented ATRA-induced c-Cbl phosphorylation and crippled p85 PI3K phosphorylation, indicating Lyn kinase activity is important for ATRA-propelled events potentially regulated by CD38. We found that loss of Lyn activity coincided with a decrease in Vav1/Lyn/CD38 and SLP-76/Lyn/CD38 interaction, suggesting these molecules form a complex that regulates CD38 signaling. Lyn inhibition also reduced Lyn and CD38 binding to p85 PI3K, indicating CD38 facilitates a complex responsible for PI3K phosphorylation. Therefore, Lyn kinase activity is important for CD38-associated signaling that may drive ATRA-induced differentiation.

MiR‐503 targets PI3K p85 and IKK‐β and suppresses progression of non‐small cell lung cancer

A microRNA usually has the ability to coordinately repress multiple target genes and therefore are associated with many pathological conditions such as human cancer. Our understanding of the biological roles of microRNAs in lung cancer, however, remains incomplete. In this study, we identified miR-503 as a tumor-suppressive microRNA in human non-small cell lung carcinoma (NSCLC), whose expression level correlates inversely with overall survival in NSCLC patients. Ectopic expression of miR-503 suppressed tumor cell proliferation and metastasis-related traits in vitro as well as in vivo, supporting a anti-cancer role of the microRNA in NSCLC progression. Mechanistic study revealed that oncogenic PI3K p85 and IKK-β were direct targets of miR-503. Overexpression of either PI3K p85 or IKK-β partially restored the malignant properties of NSCLC cells in the presence of miR-503. Taken together, our data demonstrate miR-503 inhibits the malignant phenotype of NSCLC by targeting PI3K p85 and IKK-β and might play a suppressive role in the pathogenesis of NSCLC, thus providing new insights in developing novel diagnostic and therapeutic approaches.

Trim32 reduces PI3K–Akt–FoxO signaling in muscle atrophy by promoting plakoglobin–PI3K dissociation

Activation of the PI3K-Akt-FoxO pathway induces cell growth, whereas its inhibition reduces cell survival and, in muscle, causes atrophy. Here, we report a novel mechanism that suppresses PI3K-Akt-FoxO signaling. Although skeletal muscle lacks desmosomes, it contains multiple desmosomal components, including plakoglobin. In normal muscle plakoglobin binds the insulin receptor and PI3K subunit p85 and promotes PI3K-Akt-FoxO signaling. During atrophy, however, its interaction with PI3K-p85 is reduced by the ubiquitin ligase Trim32 (tripartite motif containing protein 32). Inhibition of Trim32 enhanced plakoglobin binding to PI3K-p85 and promoted PI3K-Akt-FoxO signaling. Surprisingly, plakoglobin overexpression alone enhanced PI3K-Akt-FoxO signaling. Furthermore, Trim32 inhibition in normal muscle increased PI3K-Akt-FoxO signaling, enhanced glucose uptake, and induced fiber growth, whereas plakoglobin down-regulation reduced PI3K-Akt-FoxO signaling, decreased glucose uptake, and caused atrophy. Thus, by promoting plakoglobin-PI3K dissociation, Trim32 reduces PI3K-Akt-FoxO signaling in normal and atrophying muscle. This mechanism probably contributes to insulin resistance during fasting and catabolic diseases and perhaps to the myopathies and cardiomyopathies seen with Trim32 and plakoglobin mutations.

Quantitative analysis by surface plasmon resonance of CD28 interaction with cytoplasmic adaptor molecules Grb2, Gads and p85 PI3K

CD28 surface receptors provide co-stimulatory signals that are required for full T cell activation. The CD28 cytoplasmic region has one YMNM and two PXXP motifs as a functional motif. Upon CD28 ligation, Grb2, Gads, and the p85 subunit of PI3 kinase are recruited to the CD28 cytoplasmic region. Here, the interactions between these adaptor proteins and CD28 cytoplasmic domains were analyzed using a Biacore surface plasmon resonance biosensor. For all three adaptor proteins, entire molecules bound more tightly to CD28 than did their isolated SH2 domains. For each adaptor, different outcomes of mutation of CD28’s PXXP motifs on binding affinity indicated that only the SH3 domain of Grb2 bound directly. Regarding binding of SH2s to CD28, the SH2 domains of p85 bound more strongly than those of both Grb2 and Gads. Since intact p85 had a 50-fold higher binding affinity than its fragments, and yet the p85-CD28 interaction does not involve SH3-PXXP binding, binding of both N-terminal and C-terminal SH2s to YMNM may create an “avidity” effect. In contrast, when Grb2 and Gads interact with CD28, binding of their SH3 domains may be important. These results suggest that all these interactions are multivalent, through both SH2 and SH3 domains.

Prevalence of PIK3CA mutations and the SNP rs17849079 in Arab breast cancer patients

Carcinomas initiate and progress due to genetic and epigenetic alterations in epithelial cells. However, recently, these alterations have also been reported in stromal fibroblasts. The gain-of-function mutations in the PI3K p110 catalytic subunit (PIK3CA) have been identified in many cancers with a current global incidence of 26% (18–40%) in breast carcinomas. We analyzed the mutational frequency of PIK3CA of three hotspots (exons 1, 9, and 20) in 81 primary invasive breast cancers (BC) and 25 cultured breast cancer-associated fibroblast (CAF) samples by Sanger sequencing in Arab breast cancer patients. Associations between the incidence of any PIK3CA mutation and several clinicopathologic characteristics were assessed using chi-square tests for categorical or t test for continuous variables. Furthermore, survival curves were estimated using the Kaplan–Meier method with the log rank test to evaluate the significance of their differences. We identified a total of 21 PIK3CA missense mutations with a frequency of 25.9%. The majority of the mutations, 17 out of 21 (81%), were in exon 20 (p.His1047Arg, p.His1047Lys, p.Thr1025Ala, p.Gly1049Arg, p.Asp1056Asn) while the remainder, 4 out of 21 (19%) were in exon 9 (p.Glu545Lys). PIK3CA mutations were significantly associated with lower grade and hormone receptor positivity. Although there was a favorable trend in overall survival for patients whose tumor harbored PIK3CA mutations, the difference was not statistically significant (P = 0.10). However, we did not detect any somatic mutations in CAFs. Furthermore, we have shown a high prevalence (8.2-fold) of a silent variant (SNP, rs17849079) in the Arab breast cancer population compared with disease-free individuals.

Human Breast Cancer Cells Harboring a Gatekeeper T798M Mutation in HER2 Overexpress EGFR Ligands and Are Sensitive to Dual Inhibition of EGFR and HER2

Mutations in receptor tyrosine kinase (RTK) genes can confer resistance to receptor-targeted therapies. A T798M mutation in the HER2 oncogene has been shown to confer resistance to the tyrosine kinase inhibitor (TKI) lapatinib. We studied the mechanisms of HER2-T798M-induced resistance to identify potential strategies to overcome that resistance. HER2-T798M was stably expressed in BT474 and MCF10A cells. Mutant cells and xenografts were evaluated for effects of the mutation on proliferation, signaling, and tumor growth after treatment with combinations of inhibitors targeting the EGFR/HER2/HER3/PI3K axis. A low 3% allelic frequency of the T798M mutant shifted 10-fold the IC50 of lapatinib. In mutant-expressing cells, lapatinib did not block basal phosphorylation of HER2, HER3, AKT, and ERK1/2. In vitro kinase assays showed increased autocatalytic activity of HER2-T798M. HER3 association with PI3K p85 was increased in mutant-expressing cells. BT474-T798M cells were also resistant to the HER2 antibody trastuzumab. These cells were sensitive to the pan-PI3K inhibitors BKM120 and XL147 and the irreversible HER2/EGFR TKI afatinib but not the MEK1/2 inhibitor CI-1040, suggesting continued dependence of the mutant cells on ErbB receptors and downstream PI3K signaling. BT474-T798M cells showed increased expression of the EGFR ligands EGF, TGFα, amphiregulin, and HB-EGF. Addition of the EGFR neutralizing antibody cetuximab or lapatinib restored trastuzumab sensitivity of BT474-T798M cells and xenografts, suggesting that increased EGFR ligand production was causally associated with drug resistance. Simultaneous blockade of HER2 and EGFR should be an effective treatment strategy against HER2 gene-amplified breast cancer cells harboring T798M mutant alleles.

Endocrine Protection of Ischemic Myocardium by FGF21 from the Liver and Adipose Tissue

Myocardial ischemia, while causing cardiomyocyte injury, can activate innate protective processes, enhancing myocardial tolerance to ischemia. Such processes are present in not only the heart, but also remote organs. In this investigation, we demonstrated a cardioprotective process involving FGF21 from the liver and adipose tissue. In response to myocardial ischemia/reperfusion injury in the mouse, FGF21 was upregulated and released from the hepatic cells and adipocytes into the circulation and interacted with FGFR1 in cardiomyocytes under the mediation of the cell membrane protein β-Klotho, inducing FGFR1 phosphorylation. This action caused phosphorylation of the signaling molecules PI3K p85, Akt1, and BAD, thereby reducing caspase 3 activity, cell death, and myocardial infarction in association with improvement of myocardial function. These observations suggest that FGF21 is upregulated and released from the liver and adipose tissue in myocardial injury, contributing to myocardial protection by the mediation of the FGFR1/β-Klotho–PI3K–Akt1–BAD signaling network.

A pharmacological model reveals biased dependency on PI3K isoforms for tumor cell growth

To identify the contribution of individual isoform (α, β, γ, δ) of class I PI3Ks to tumor cell growth for proper use of PI3K inhibitors in cancer therapy. A panel of human rhabdomyosarcoma Rh30 cells stably expressing myristoylation (Myr)-tagged one of class I PI3K p110 subunits was established. PI3K activity was analyzed by measuring phosphorylated Akt with Western blotting, and isoform-specific PI3K activities were validated with PI3K isoform-selective inhibitors. The growth of prostate cancer PC-3 cells and B cell type leukemia Raji cells was determined using SRB assay and CCK-8 assay, respectively. The phosphorylation of Akt in Rh30-Myr-p110α, β, γ, δ cells was preferentially inhibited by PI3K isoform-selective inhibitors A66 (PI3Kα), TGX221 (PI3Kβ), AS604850 (PI3Kγ) and CAL-101 (PI3Kδ), respectively. A newly obtained PI3K inhibitor WJD008 (10 μmol/L) completely abrogated Akt phosphorylation by all the isoforms of class I PI3Ks, thus acted as a pan-PI3K inhibitor. In prostate cancer PC-3 cells, the PI3K isoform-selective inhibitors were much less potent than WJD008 in suppression of the proliferation. In B cell type leukemia Raji cells, inhibition of PI3Kδ alone or all the isoforms of class I PI3Ks displayed similar potency against the cell proliferation, whereas selective inhibition of individual PI3Kα/β/γ isoforms resulted in negligible activity. Rh30-Myr-p110α, β, γ, δ cells are a useful cell model to identify the selectivity of PI3K inhibitors. Pan-PI3K inhibitors are suitable for treating PC-3 cells, whereas selective PI3Kδ inhibitor is sufficient to block Raji cell growth. The biased dependency on PI3K isoforms for tumor cell growth rationalizes the use of PI3K inhibitors with different selectivity for cancer therapy.

Gli1 Transcriptional Activity is Negatively Regulated by AKT2 in Neuroblastoma

Activation of the Hedgehog (Hh) signaling pathway has been implicated in a variety of malignancies including neuroblastoma. Expression of Gli1, a downstream effector of Hh, correlates with a favorable prognosis in patients with neuroblastoma. Moreover, Gli1 overexpression reduces mitotic index and induces transcription of genes involved in the differentiation of neuroblastoma cells; however, much remains unknown regarding the regulation of Gli1 transcriptional activity. Here, we report a novel negative regulation of Gli1 transcriptional activity by PI3K/AKT2 signal transduction pathway. Constitutively active PI3K subunit, p110α, inhibited Gli1 transcriptional activity in neuroblastoma cells, whereas, overexpression of an inactive form of PI3K subunit, p85, enhanced its activity. Specifically, the AKT2 isoform inhibited Gli1 luciferase activity. Silencing AKT2 using siRNA increased Gli1 transcriptional activity and conversely, overexpression of constitutively active AKT2 (myr-AKT2) decreased Gli1 transcriptional activity. Furthermore, Gli1 overexpression-mediated decrease in anchorage-independent growth was rescued by AKT2 overexpression. We also demonstrated that AKT2 overexpression regulates the nuclear-cytoplasmic distribution of exogenous Gli1 protein in neuroblastoma cells by relieving a GSK3β-mediated destabilization of SUFU, a negative regulator of Gli1 nuclear translocation. Inhibition of nuclear Gli1 accumulation may explain for the suppression of the tumor-suppressive function of Gli1. Collectively, our findings suggest an important role of Gli1 as a tumor suppressor in neuroblastoma, and offer a mechanism by which AKT2 regulates the subcellular localization, and in turn, inhibits the tumor-suppressive function of Gli1 in neuroblastoma.

Phenethyl isothiocyanate suppresses EGF-stimulated SAS human oral squamous carcinoma cell invasion by targeting EGF receptor signaling

Phenethyl isothiocyanate (PEITC) is a natural compound that is involved in chemoprevention as well as inhibition of cell growth and induction of apoptosis in several types of cancer cells. Previous studies have revealed that PEITC suppresses the invasion of AGS gastric and HT-29 colorectal cancer cells. However, the effects of PEITC on the metastasis of SAS oral cancer cells remain to be determined. Our results showed that PEITC treatment inhibited the invasion of EGF-stimulated SAS cells in a concentration-dependent manner, but appeared not to affect the cell viability. The expression and enzymatic activities of matrix metalloprotease-2 (MMP-2) and matrix metalloprotease-9 (MMP-9) were suppressed by PEITC. Concomitantly, we observed an increase in the protein expression of both tissue inhibitor of metalloproteinase-1 (TIMP-1) and -2 (TIMP-2) in treated cells. Furthermore, PEITC treatments decreased the protein phosphorylation of epidermal growth factor receptor (EGFR) and downstream signaling proteins including PDK1, PI3K(p85), AKT, phosphorylated IKK and IκB to inactivate NF-κB for the suppression of MMP-2 and MMP-9 expression. In addition, PEITC can trigger the MAPK signaling pathway through the increase in phosphorylated p38, JNK and ERK in treated cells. Our data indicate that PEITC is able to inhibit the invasion of EGF-stimulated SAS oral cancer cells by targeting EGFR and its downstream signaling molecules and finally lead to the reduced expression and enzymatic activities of both MMP-2 and MMP-9. These results suggest that PEITC is promising for the therapy of oral cancer metastasis.

Overexpression of miR-126 promotes the differentiation of mesenchymal stem cells toward endothelial cells via activation of PI3K/Akt and MAPK/ERK pathways and release of paracrine factors

The endothelial cell (EC)-specific miRNA, miR-126, is known to promote angiogenesis in response to angiogenic factors by repressing negative regulators of signal transduction pathways; however, whether miR-126 might regulate the differentiation of stem cells toward endothelial lineage remains unknown. To answer this question, in this study mesenchymal stem cells (MSCs) harvested from C57BL/6 mouse bone marrow were transfected with miR-126 (MSCmiR-126) using recombinant lentiviral vectors. Results showed the para-secretion and the expression levels of phosphorylated PI3K p85, Akt, p38, ERK1 protein in the MSCmiR-126 group were dramatically increased when compared with the control group. With half culture medium refreshed every 3 days, a small number of 6-day-cultured MSCmiR-126 differentiated into endothelial-like cells and most of 9-day-cultured MSCmiR-126 formed a cobblestone-like structure. These differentiated cells evidently expressed EC-specific makers and possessed mature ECs function, while inhibition of paracrine factors suppressed the MSC-EC differentiation. Strikingly, the increased secretion of MSCmiR-126 and their endothelial-differentiated potential were deprived by using a PI3K or MEK chemical inhibitor. Our results suggest that overexpression of miR-126 agumenting the endothelial differentiation of MSCs might in part be attributable to the activation of PI3K/Akt and MAPK/ERK pathways and an increased release of paracrine factors.