PI3K inhibition protects mice from NAFLD by down-regulating CMKLR1 and NLRP3 in Kupffer cells

Inflammation induced by high-fat diet (HFD) is of critical importance in the development of hepatic steatosis. The role of chemerin in the progress of nonalcoholic fatty liver disease (NAFLD) remains controversial. Here, we have evaluated the effects and mechanism of chemerin on insulin sensitivity and inflammation. An inhibitor (wortmannin) and agonist (insulin-like growth factor 1 (IGF-1) of phosphatidyl inositol 3-kinase (PI3K) were applied to Kupffer cells (KCs) after treatment with a concentration gradient of chemerin in vitro. Mice were subjected to both HFD and intra-peritoneal injections of wortmannin and IGF-1 for 12 weeks. Levels of cytokines were evaluated by enzyme-linked immunosorbent assays and the mRNA and protein levels in the KCs were tested by quantitative real-time polymerase chain reaction and western blotting, respectively. Our data suggested that levels of interleukin 1β (IL-1β) and IL-18 in the KCs and mice treated with wortmannin were significantly lower than that of IGF-1. Consistently, the expression of chemokine-like receptor 1 (CMKLR1) and nucleotide oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) was significantly lower in the KCs and mice treated with wortmannin than those treated with IGF-1. Consistently, liver function, insulin resistance, and hepatic steatosis were much more severe in mice treated with IGF-1 than those treated with wortmannin. In conclusions, PI3K inhibition attenuates hepatic steatosis an KC-mediated inflammation via down-regulation of CMKLR1 and NLRP3 in HFD mice

Dual-Blocking of PI3K and mTOR Improves Chemotherapeutic Effects on SW620 Human Colorectal Cancer Stem Cells by Inducing Differentiation

Cancer stem cells (CSCs) have tumor initiation, self-renewal, metastasis and chemo-resistance properties in various tumors including colorectal cancer. Targeting of CSCs may be essential to prevent relapse of tumors after chemotherapy. Phosphatidylinositol-3-kinase (PI3K) and mammalian target of rapamycin (mTOR) signals are central regulators of cell growth, proliferation, differentiation, and apoptosis. These pathways are related to colorectal tumorigenesis. This study focused on PI3K and mTOR pathways by inhibition which initiate differentiation of SW620 derived CSCs and investigated its effect on tumor progression. By using rapamycin, LY294002, and NVP-BEZ235, respectively, PI3K and mTOR signals were blocked independently or dually in colorectal CSCs. Colorectal CSCs gained their differentiation property and lost their stemness properties most significantly in dual-blocked CSCs. After treated with anti-cancer drug (paclitaxel) on the differentiated CSCs cell viability, self-renewal ability and differentiation status were analyzed. As a result dual-blocking group has most enhanced sensitivity for anti-cancer drug. Xenograft tumorigenesis assay by using immunodeficiency mice also shows that dual-inhibited group more effectively increased drug sensitivity and suppressed tumor growth compared to single-inhibited groups. Therefore it could have potent anti-cancer effects that dual-blocking of PI3K and mTOR induces differentiation and improves chemotherapeutic effects on SW620 human colorectal CSCs.

beta-TrCP1 degradation is a novel action mechanism of PI3K/mTOR inhibitors in triple-negative breast cancer cells

An F-box protein, beta-TrCP recognizes substrate proteins and destabilizes them through ubiquitin-dependent proteolysis. It regulates the stability of diverse proteins and functions as either a tumor suppressor or an oncogene. Although the regulation by beta-TrCP has been widely studied, the regulation of beta-TrCP itself is not well understood yet. In this study, we found that the level of beta-TrCP1 is downregulated by various protein kinase inhibitors in triple-negative breast cancer (TNBC) cells. A PI3K/mTOR inhibitor PI-103 reduced the level of beta-TrCP1 in a wide range of TNBC cells in a proteasome-dependent manner. Concomitantly, the levels of c-Myc and cyclin E were also downregulated by PI-103. PI-103 reduced the phosphorylation of beta-TrCP1 prior to its degradation. In addition, knockdown of beta-TrCP1 inhibited the proliferation of TNBC cells. We further identified that pharmacological inhibition of mTORC2 was sufficient to reduce the beta-TrCP1 and c-Myc levels. These results suggest that mTORC2 regulates the stability of beta-TrCP1 in TNBC cells and targeting beta-TrCP1 is a potential approach to treat human TNBC.

Resveratrol Inhibits Hypoxia-Induced Vascular Endothelial Growth Factor Expression and Pathological Neovascularization

PURPOSE: To investigate the effects of resveratrol on the expression of hypoxia-inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) in human adult retinal pigment epithelial (ARPE-19) cells, and on experimental choroidal neovascularization (CNV) in mice. MATERIALS AND METHODS: ARPE-19 cells were treated with different concentrations of resveratrol and then incubated under hypoxic conditions with subsequent evaluation of cell viability, expression of HIF-1alpha, and expression of VEGF. The effects of resveratrol on the synthesis and degradation of hypoxia-induced HIF-1alpha were evaluated using inhibitors of the PI3K/Akt/mTOR and the ubiquitin proteasome pathways. In animal studies, CNV lesions were induced in C57BL/6 mice by laser photocoagulation. After 7 days of oral administration of resveratrol or vehicle, which began one day after CNV induction, image analysis was used to measure CNV areas on choroidal flat mounts stained with isolectin IB4. RESULTS: In ARPE-19 cells, resveratrol significantly inhibited HIF-1alpha and VEGF in a dose-dependent manner, by blocking the PI3K/Akt/mTOR signaling pathway and by promoting proteasomal HIF-1alpha degradation. In mice experiments, orally administered resveratrol significantly inhibited CNV growth in a dose-dependent manner. CONCLUSION: Resveratrol may have therapeutic value in the management of diseases involving pathological neovascularization.

The reno-protective effect of a phosphoinositide 3-kinase inhibitor wortmannin on streptozotocin-induced proteinuric renal disease rats

Diabetic nephropathy (DN) is a progressive kidney disease that is caused by injury to kidney glomeruli. Podocytes are glomerular epithelial cells and play critical roles in the glomerular filtration barrier. Recent studies have shown the importance of regulating the podocyte actin cytoskeleton in early DN. The phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin, simultaneously regulates Rac1 and Cdc42, which destabilize the podocyte actin cytoskeleton during early DN. In this study, in order to evaluate the reno-protective effects of wortmannin in early DN by regulating Rac1 and Cdc42, streptozotocin (STZ)-induced proteinuric renal disease (SPRD) rats were treated with wortmannin. The albuminuria value of the SPRD group was 3.55 +/- 0.56 mg/day, whereas wortmannin group was 1.77 +/- 0.48 mg/day. Also, the albumin to creatinine ratio (ACR) value of the SPRD group was 53.08 +/- 10.82 mg/g, whereas wortmannin group was 20.27 +/- 6.41 mg/g. Changes in the expression level of nephrin, podocin and Rac1/Cdc42, which is related to actin cytoskeleton in podocytes, by wortmannin administration were confirmed by Western blotting. The expression levels of nephrin (79.66 +/- 0.02), podocin (87.81 +/- 0.03) and Rac1/Cdc42 (86.12 +/- 0.02) in the wortmannin group were higher than the expression levels of nephrin (55.32 +/- 0.03), podocin (53.40 +/- 0.06) and Rac1/Cdc42 (54.05 +/- 0.04) in the SPRD group. In addition, expression and localization of nephrin, podocin and desmin were confirmed by immunofluorescence. In summary, we found for the first time that wortmannin has a reno-protective effect on SPRD rats during the early DN. The beneficial effects of wortmannin in SPRD rats indicate that this compound could be used to delay the progression of the disease during the early DN stage.

Targeted therapy of metastatic breast cancer

Breast cancer is a heterogeneous disease characterised by a dysregulation of multiple pathways related to cell differentiation, cell cycle control, apoptosis, angiogenesis and development of metastasis. Acting against these pathways provides therapeutic targets for new targeted biologic therapies, which, in the future, might constitute a key for fighting cancer. The development of molecular technology in recent years has allowed a further comprehension of these mutations and dysregulated pathways leading to oncogenesis. New targeted biologic therapies will block essential functions of cancer cells and tumour stroma. A growing number of therapy options, alone or in combination with background treatments (chemotherapy, hormone therapy, radiotherapy), will allow oncologists a better adaptation of treatment to patients and disease characteristics. Examples of approved targeted agents in breast cancer include agents targeting the human epidermal growth factor receptor 2 (HER2), such as trastuzumab, lapatinib and the anti-VEGF bevacizumab. In addition, there are other therapy classes under evaluation, including novel antiEGFR or antiHER2 therapies; agents fighting other tyrosine kinases, including the Src and the insulinlike growth factor receptor; agents interfering critically relevant pathways, such as PI3K/AKT/mTOR inhibitors; and agents promoting apoptosis, such as PARP inhibitors (for particular breast cancer subtypes, such as basal-like, or breast cancer with BRCA mutations) and others. The better selectivity against malignant cells of these therapies, when compared to conventional chemotherapy, gives, a priori, at least two advantages to biologic treatments: fewer side effects and a more individualised treatment of cancer depending on the tumour's molecular characteristics. The ability to identify patients' subgroups and response predicting factors will be crucial in obtaining the greatest benefit with minimal toxicity levels. Unsolved questions remain, such as appropriate patient selection based on the expression of the therapeutic target in the tumour, the study of the efficacy of the drug in not so extensively pretreated populations and with a greater chance of response, the use of new pharmacodynamic models to help to define new response predicting factors for a specific new biologic therapy, the combined and rational use of different biologic therapies having different molecular targets and fighting the same target through a complementary mechanism of action that might improve clinical efficacy (AU)

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Inhibiting PI3K as a therapeutic strategy against cancer

Class I PI3K is composed of heterodimeric lipid kinases regulating essential cellular functions including proliferation, apoptosis and metabolism. Class I PI3K isoforms are commonly amplified in different cancer types and the PI3Kalpha catalytic subunit, PIK3CA, has been found mutated in a variable proportion of tumours of different origin. Furthermore, PI3K has been shown to mediate oncogenic signalling induced by several oncogenes such as HER2 or Ras. These facts suggest that PI3K might be a good target for anticancer drug discovery. Today, the rise of PI3K inhibitors and their first in vivo results have cleared much of the path for the development of PI3K inhibitors for anticancer therapy. Here we will review the PI3K pathway and the pharmacological results of PI3K inhibition (AU)