PI3K/AKT and ERK regulate retinoic acid-induced neuroblastoma cellular differentiation

Thymoquinone (TQ), a bioactive component of black caraway seed (Nigella sativa) oil, is reported to have antineoplastic properties. In this study we investigated the effect of TQ on a panel of human breast cancer cell lines. Cell viability assays showed that TQ killed T-47D, MDA-MB-231, and MDA-MB-468 cells via p53-independent induction of apoptosis; however, MCF-7 cells were refractory to the cytotoxic action of TQ. Western Blot analysis showed that MCF-7 cells expressed high levels of cytoprotective NADPH quinone oxidoreductase 1 (NQO1), which was responsible for TQ-resistance since inhibition of NQO1 with dicoumarol rendered MCF-7 cells TQ-sensitive. These findings may be clinically important when considering TQ as a possible adjunct treatment for breast cancer since a high percentage of breast tumors express NQO1.     

PI3K/PTEN/AKT signaling regulates prostate tumor angiogenesis

PI3K pathway exerts its function through its downstream molecule AKT in regulating various cell functions including cell proliferation, cell transformation, cell apoptosis, tumor growth and angiogenesis. PTEN is an inhibitor of PI3K, and its loss or mutation is common in human prostate cancer. But the direct role and mechanism of PI3K/PTEN signaling in regulating angiogenesis and tumor growth in vivo remain to be elucidated. In this study, by using chicken chorioallantoic membrane (CAM) and in nude mice models, we demonstrated that inhibition of PI3K activity by LY294002 decreased PC-3 cells-induced angiogenesis. Reconstitution of PTEN, the molecular inhibitor of PI3K in PC-3 cells inhibited angiogenesis and tumor growth. Immunohistochemical staining indicated that PTEN expression suppressed HIF-1, VEGF and PCNA expression in the tumor xenographs. Similarly, expression of AKT dominant negative mutant also inhibited angiogenesis and tumor growth, and decreased the expression of HIF-1 and VEGF in the tumor xenographs. These results suggest that inhibition of PI3K signaling pathway by PTEN inhibits tumor angiogenesis and tumor growth. In addition, we found that AKT is the downstream target of PI3K in controlling angiogenesis and tumor growth, and PTEN could inhibit angiogenesis by regulating the expression of HIF-1 and VEGF expression through AKT activation in PC-3 cells.     

PI3K/AKT signaling regulates bioenergetics in immortalized hepatocytes

Regulation of cellular bioenergetics by PI3K/AKT signaling was examined in isogenic hepatocyte cell lines lacking the major inhibitor of PI3K/AKT signaling, PTEN (phosphatase and tensin homolog deleted on chromosome 10). PI3K/AKT signaling was manipulated using the activator (IGF-1) and the inhibitor (LY 294002) of the PI3K/AKT pathway. Activation of PI3K/AKT signaling resulted in an enhanced anaerobic glycolysis and mitochondrial respiration. AKT, when phosphorylated and activated, translocated to mitochondria and localized within the membrane structure of mitochondria, where it phosphorylated a number of mitochondrial-resident proteins including the subunits α and β of ATP synthase. Inhibition of GSK3β by either phosphorylation by AKT or lithium chloride resulted in activation of pyruvate dehydrogenase, i.e., a decrease in its phosphorylated form. AKT-dependent phosphorylation of ATP synthase subunits α and β resulted in an increased complex activity. AKT translocation to mitochondria was associated with an increased expression and activity of complex I. These data suggest that the mitochondrial signaling pathway AKT/GSK3β/PDH, AKT-dependent phosphorylation of ATP synthase, and upregulation of mitochondrial complex I expression and activity are involved in the control of mitochondrial bioenergetics by increasing substrate availability and regulating the mitochondrial catalytic/energy-transducing capacity.     

Zinc ions negatively regulate proapoptotic signaling in cells expressing oncogenic mutant Ras

BioMetals - Mutational activation of the Ras family of proto-oncogenes promotes cell survival and proliferation. Studies using cells cultured in vitro have shown that ectopic expression of...     

Oridonin-induced mitochondria-dependent apoptosis in esophageal cancer cells by inhibiting PI3K/AKT/mTOR and Ras/Raf pathways

Oridonin, an active diterpenoid isolated from Rabdosia rubescens, has been reported for its antitumor activity on several cancers. However, its effect on human esophageal cancer remains unclear. In this study, we demonstrated that oridonin could inhibit the growth of human esophageal cancer cells both in vitro and in vivo. Oridonin not only suppressed the proliferation, but also induced cell cycle arrest and mitochondrial-mediated apoptosis in KYSE-30, KYSE-150, and EC9706 cells with dose-dependent manner. Further mechanism studies revealed that oridonin led cell cycle arrest in esophageal cancer cells via downregulating cell cycle-related proteins, such as cyclin B1 and CDK2, while upregulating p53 and p21. Oridonin also increased proapoptotic protein Bax and reduced antiapoptotic protein Bcl-2, as well as the increased expression of cleaved caspase-3, -8, and -9. In addition, oridonin treatment could significantly inhibit the PI3K/Akt/mTOR and Ras/Raf signaling pathway. In vivo results further demonstrated that oridonin treatment markedly inhibited tumor growth in the esophageal cancer xenograft mice model. Taken together, these results suggest that oridonin may be a potential anticancer agent for the treatment of esophageal cancer.     

Role of PI3K/AKT/mTOR signaling in the cell cycle progression of human prostate cancer

Prostate cancer is one of the most common cancers among men. Recent studies demonstrated that PI3K signaling is an important intracellular mediator which is involved in multiple cellular functions including proliferation, differentiation, anti-apoptosis, tumorigenesis, and angiogenesis. In the present study, we demonstrate that the inhibition of PI3K activity by LY294002, inhibited prostate cancer cell proliferation and induced the G(1) cell cycle arrest. This effect was accompanied by the decreased expression of G(1)-associated proteins including cyclin D1, CDK4, and Rb phosphorylation at Ser780, Ser795, and Ser807/811, whereas expression of CDK6 and beta-actin was not affected by LY294002. The expression of cyclin kinase inhibitor, p21(CIP1/WAF1), was induced by LY294002, while levels of p16(INK4) were decreased in the same experiment. The inhibition of PI3K activity also inhibited the phosphorylation and p70(S6K), but not MAPK. PI3K regulates cell cycle through AKT, mTOR to p70(S6K). The mTOR inhibitor rapamycin has similar inhibitory effects on G(1) cell cycle progression and expression of cyclin D1, CDK4, and Rb phosphorylation. These results suggest that PI3K mediates G(1) cell cycle progression and cyclin expression through the activation of AKT/mTOR/p70(S6K) signaling pathway in the prostate cancer cells.     

Signalling transduction of O-GlcNAcylation and PI3K/AKT/mTOR-axis in prostate cancer

Hexosamine biosynthetic (HBP) and PI3K/AKT/mTOR pathways are found to predominate the proliferation and survival of prostate cancer cells. Both these pathways have their own specific intermediates to propagate the secondary signals in down-stream cascades and besides having their own structured network, also have shared interconnecting branches. These interconnections are either competitive or co-operative in nature depending on the microenvironmental conditions. Specifically, in prostate cancer HBP and mTOR pathways increases the expression and protein level of androgen receptor in order to support cancer cell proliferation, advancement and metastasis. Pharmacological inhibition of a single pathway is therefore insufficient to stop disease progression as the cancer cells manage to alter the signalling channel. This is one of the primary reasons for the therapeutic failure in prostate cancer and emergence of chemoresistance. Inhibition of these multiple pathways at their common junctures might prove to be of benefit in men suffering from an advanced disease state. Hence, a thorough understanding of these cellular intersecting points and their significance with respect to signal transduction mechanisms might assist in the rational designing of combinations for effective management of prostate cancer.     

Abamectin induces apoptosis and autophagy by inhibiting reactive oxygen species‐mediated PI3K/AKT signaling in MGC803 cells

Abamectin (ABA) is one of the most widely used compounds in agriculture and veterinary medicine. However, the cytotoxicity of ABA in human gastric cells is utterly unknown. In this study, ABA suppressed the proliferation of MGC803 cells by arresting the cell cycle at the G0/G1‐phase. Moreover, ABA induced mitochondrial‐mediated apoptosis by inducing the loss of mitochondrial membrane potential, upregulation of Bax/Bcl‐2, and activation of caspase‐3. ABA significantly improved the LC3‐II/LC3‐I ratio and reduced P62 protein expression in a dose‐dependent manner. Through detection of the reactive oxygen species (ROS) levels, we found ABA induced the accumulation of intracellular ROS and then reduced PI3K/AKT signaling activation related to MGC803 cell apoptosis and autophagy. Our results indicate that ABA exerts cytotoxic effects on human MGC803 cells through apoptosis and autophagy by inhibiting ROS‐mediated PI3K/AKT signaling. Furthermore, ABA may be a potential risk to human gastric health.     

Mollugin induces tumor cell apoptosis and autophagy via the PI3K/AKT/mTOR/p70S6K and ERK signaling pathways

Mollugin, a bioactive phytochemical isolated from Rubia cordifolia L., has shown preclinical anticancer efficacy in various cancer models. However the effects of mollugin in regulating cancer cell survival and death remains undefined. In the present study we found that mollugin exhibited cytotoxicity on various cancer models. The suppression of cell viability was due to the induction of mitochondria apoptosis. In addition, the presence of autophagic hallmarks was observed in mollugin-treated cells. Notably, blockade of autophagy by a chemical inhibitor or RNA interference enhanced the cytotoxicity of mollugin. Further experiments demonstrated that phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) and extracellular regulated protein kinases (ERK) signaling pathways participated in mollugin-induced autophagy and apoptosis. Together, these findings support further studies of mollugin as candidate for treatment of human cancer cells.     

Speedy/RINGO protein interacts with ERK/MAPK and PI3K/AKT pathways in SH-SY5Y neuroblastoma cells

Molecular and Cellular Biochemistry - Pro-inflammatory cytokines prevent bone regeneration in vivo and activation of nuclear factor-κB (NF-κB) signaling has been proposed to lead to...     

Rab11a通过PI3K/AKT和Ras/MEK/ERK信号通路调节胰腺癌细胞凋亡和侵袭

目的:探究Rab11a在胰腺癌中的表达模式及其对肿瘤生长和转移的影响.方法:通过免疫组织化学法、RT-PCR和Western blot检测60例胰腺癌患者的癌组织和癌旁组织中Rab11a的表达.通过对人胰腺癌细胞系PANC1转染靶向Rab11a的小干扰RNA或过表达Rab11a的pcDNA3.1质粒考察Rab11a对细...     

Resveratrol suppresses the epithelial-to-mesenchymal transition in PC-3 cells by down-regulating the PI3K/AKT signaling pathway

Resveratrol possesses a wide spectrum of pharmacological properties and has been an ideal alternative drug for the treatment of different cancers, including prostate cancer. However, the mechanisms by which resveratrol inhibits the growth of prostate cancer are still not fully elucidated. To understand the effect of resveratrol on the apoptosis and the epithelial-to-mesenchymal transition (EMT) of prostate cancer as well as its related mechanism, we investigated the potential use of resveratrol in PC-3 prostate cancer cells in vitro using real-time PCR, fluorescence-activated cell sorting, Western blotting, etc. Resveratrol suppresses the PC-3 prostate cancer cell growth and induces apoptosis. Resveratrol also influences the expression of EMT-related proteins (increased E-cadherin and decreased Vimentin expression). Finally, resveratrol also suppressed Akt phosphorylation in PC-3 cells. This study indicates that resveratrol may be a potential anti-cancer treatment for prostate cancer; moreover, it provides new evidence that resveratrol suppresses prostate cancer growth and metastasis.     

乳腺癌组织中PI3K/AKT信号通路相关蛋白表达

目的研究PI3K/AKT信号传导通路中Her-2、PI3K、AKT以及bcl-2在乳腺癌中的表达及其与临床特征、预后的相关性。方法用免疫组化SP法检测31例乳腺癌和癌旁组织中Her-2、PI3K、AKT以及bcl-2的表达。结果 Her-2、PI3K、AKT在乳腺癌中的表达率分别为45.2%、90.3%、67.7%,均明显高于癌旁组织(P<0.05),而bcl-2在乳腺癌中的表达率为58.1%,在癌旁组织中的表达率为83.9%,(P<0.05);乳腺癌组织中,Her-2、PI3K、AKT、bcl-2的表达均与年龄无相关性(P>0.05);Her-2、AKT在乳腺癌中的表达和组织学分级呈正相关(P<0.05),bcl-2的表达和组织学分级呈负相关(P<0.05),PI3K的表达与组织学分级无明显相关性(P>0.05);AKT的表达在有淋巴结转移时表达率较高,与无淋巴结转移组相比差异有显著性(P<0.05),bcl-2的表达在有淋巴结转移时表达率较低,与无淋巴结转移组相比差异有显著性(P<0.05),Her-2、PI3K的表达与淋巴结转移无明显相关性(P>0.05)。结论 Her-2、AKT的过表达和bcl-2的低表达和乳腺癌的形成和进展有关,检测Her-2、AKT以及bcl-2的表达可用于判定乳腺癌的恶性程度,并可作为判断预后的指标。     

Hydrogen sulfide attenuates uranium-induced kidney cells pyroptosis via upregulation of PI3K/AKT/mTOR signaling

We have identified that hydrogen sulfide (H₂S), a gaseous mediator, plays a crucial role in antioxidative, anti-inflammatory, and cytoprotective effects on uranium (U)-triggered rat nephrotoxicity. Pyroptosis is a special mode of inflammation and programmed cell death involved in the activation of inflammasome and Caspase-1 and the release of inflammatory cytokines. This study aims to confirm whether H₂S can alleviate U-induced rat NRK-52^E cell pyroptosis and to investigate the H₂S underlying regulatory mechanism. Our results indicate that pretreatment with NaHS (an H₂S donor) significantly inhibited U-increased reactive oxygen species level, NLRP3, apoptosis-related speck-like protein consisting of a caspase recruitment domain (ASC), and cleaved Caspase-1 proteins expression, gasdermin D messenger RNA (GSDMD mRNA) expression, interleukin (IL)−1β and IL-18 contents, lactate dehydrogenase leakage, and numbers of double-positive dying kidney cells. NaHS application evidently augmented phosphorylated PI3K, AKT, and mTOR expression as well as ratios of their respective phosphorylation to the corresponding total proteins which were downregulated by U treatment. But, LY294002 (a PI3K inhibitor) administration effectively abrogated the consequences of NaHS on the levels of p-PI3K, cleaved Caspase-1, ASC and NLRP3 proteins, GSDMD mRNA expression, and (IL)-1β and IL-18 contents. Simultaneously, LY294002 significantly reversed the effects of NaHS on U-induced pyroptosis rate and cytotoxicity. Taken together, these results indicate that H₂S ameliorated U-triggered NRK-52^E cells pyroptosis via upregulation of PI3K/AKT/mTOR pathway, suggesting a novel role for H₂S in the management of nephrotoxicity caused by U exposure.     

Angiogenin interacts with ribonuclease inhibitor regulating PI3K/AKT/mTOR signaling pathway in bladder cancer cells

Angiogenin (ANG), a member of RNase A superfamily, is the only angiogenic factor that possesses ribonucleolytic activity. Recent studies showed that the expression of ANG was elevated in various types of cancers. Accumulating evidence indicates that ANG plays an essential role in cancer progression by stimulating both cancer cell proliferation and tumor angiogenesis. Human ribonuclease inhibitor (RI), a cytoplasmic protein, is constructed almost entirely of leucine rich repeats (LRRs), which are present in a large family of proteins that are distinguished by their display of vast surface areas to foster protein–protein interactions. RI might be involved in unknown biological effects except inhibiting RNase A activity. The experiment demonstrated that RI also could suppress activity of angiogenin (ANG) through closely combining with it in vitro. PI3K/AKT/mTOR signaling pathway exerts a key role in cell growth, survival, proliferation, apoptosis and angiogenesis. We recently reported that up-regulating RI inhibited the growth and induced apoptosis of murine melanoma cells through repression of angiogenin and PI3K/AKT signaling pathway. However, ANG receptors have not yet been identified to date, its related signal transduction pathways are not fully clear and underlying interacting mechanisms between RI and ANG remain largely unknown. Therefore, we hypothesize that RI might combine with intracellular ANG to block its nuclear translocation and regulate PI3K/AKT/mTOR signaling pathway to inhibit biological functions of ANG. Here, we reported for the first time that ANG could interact with RI endogenously and exogenously by using co-immunoprecipitation (Co-IP) and GST pull-down. Furthermore, we observed the colocalization of ANG and RI in cells with immunofluorescence staining under laser confocal microscope. Moreover, through fluorescence resonance energy transfer (FRET) assay, we further confirmed that these two proteins have a physical interaction in living cells. Subsequently, we demonstrated that up-regulating ANG including ANG His37Ala mutant obviously decreased RI expression and activated phosphorylation of key downstream target molecules of PI3K/AKT/mTOR signaling pathway. Finally, up-regulating ANG led to the promotion of tumor angiogenesis, tumorigenesis and metastasis in vivo. Taken together, our data provided a novel mechanism of ANG in regulating PI3K/AKT/mTOR signaling pathway via RI, which suggested a new therapeutic target for cancer therapy.     

Crosstalk Between MAPK/ERK and PI3K/AKT Signal Pathways During Brain Ischemia/Reperfusion

The epidermal growth factor receptor (EGFR) is linked to the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Raf/mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK_1/2) signaling pathways. During brain ischemia/reperfusion, EGFR could be transactivated, which stimulates these intracellular signaling cascades that either protect cells or potentiate cell injury. In the present study, we investigated the activation of EGFR, PI3K/AKT, and Raf/MAPK/ERK_1/2 during ischemia or reperfusion of the brain using the middle cerebral artery occlusion model. We found that EGFR was phosphorylated and transactivated during both ischemia and reperfusion periods. During ischemia, the activity of PI3K/AKT pathway was significantly increased, as judged from the strong phosphorylation of AKT; this activation was suppressed by the inhibitors of EGFR and Zn-dependent metalloproteinase. Ischemia, however, did not induce ERK_1/2 phosphorylation, which was dependent on reperfusion. Coimmunoprecipitation of Son of sevenless 1 (SOS1) with EGFR showed increased association between the receptor and SOS1 in ischemia, indicating the inhibitory node downstream of SOS1. The inhibitory phosphorylation site of Raf-1 at Ser259, but not its stimulatory phosphorylation site at Ser338, was phosphorylated during ischemia. Furthermore, ischemia prompted the interaction between Raf-1 and AKT, while both the inhibitors of PI3K and AKT not only abolished AKT phosphorylation but also restored ERK_1/2 phosphorylation. All these findings suggest that Raf/MAPK/ERK_1/2 signal pathway is inhibited by AKT via direct phosphorylation and inhibition at Raf-1 node during ischemia. During reperfusion, we observed a significant increase of ERK_1/2 phosphorylation but no change in AKT phosphorylation. Inhibitors of reactive oxygen species and phosphatase and tensin homolog restored AKT phosphorylation but abolished ERK_1/2 phosphorylation, suggesting that the reactive oxygen species-dependent increase in phosphatase and tensin homolog activity in reperfusion period relieves ERK_1/2 from inhibition of AKT.     

PDGF-BB-induced MT1-MMP expression regulates proliferation and invasion of mesenchymal stem cells in 3-dimensional collagen via MEK/ERK1/2 and PI3K/AKT signaling

Mesenchymal stem cells (MSCs) mobilize membrane type-1 matrix metalloproteinase (MT1-MMP) to traffic through both 3-dimensional (3D) collagen as well as basement membrane barriers, but factors capable of regulating the expression and activity of the protease remain unidentified. Herein, we report that the MT1-MMP-dependent invasive activities of rat MSCs are controlled by PDGF-BB. Furthermore, PDGF-BB also stimulates MSC proliferation in 3D type I collagen via an MT1-MMP-dependent process that is linked to pericellular collagen degradation. PDGF-BB stimulates MT1-MMP expression at both the mRNA and protein levels in concert with ERK1/2 and PI3K/AKT activation. Inhibition of ERK1/2 or PI3K/AKT activity potently suppresses both MT1-MMP-dependent invasive and proliferative activities. Basement membrane invasion is likewise stimulated by PDGF-BB in an MT1-MMP-dependent manner via ERK1/2 and PI3K/AKT signaling. Taken together, these data serve to identify PDGF-BB as an important MSC agonist that controls invasive and proliferative activities via MT1-MMP-dependent processes that are regulated by the ERK1/2 and PI3K/AKT signaling pathways.     

Down-regulation of MEK/ERK signaling by E-cadherin-dependent PI3K/Akt pathway in differentiating intestinal epithelial cells

In vitro experiments have shown that the establishment of cell-cell contacts in intestinal epithelial cell cultures is a critical step in initiating ERK inhibition, cell cycle arrest, and induction of the differentiation process. Herein, we determined the mechanisms through which E-cadherin-mediated cell-cell contacts modulate the ERK pathway in intestinal epithelial cells. We report that: (1) removal of calcium from the culture medium of newly confluent Caco-2/15 cells (30 min, 4 mM EGTA) results in the disruption of both adherens and tight junctions and clearly decreases Akt phosphorylation while increasing MEK and ERK activities. Akt, MEK, and ERK activation levels return to control levels 60 min after calcium restoration; (2) the use of E-cadherin blocking antibodies efficiently prevents Akt phosphorylation and MEK-ERK inhibition after 70 min of calcium restoration; (3) using the PI3K inhibitor LY294002 (15 microM) in calcium switch experiments, we demonstrate that the assembly of adherens junctions activates Akt activity and triggers the inhibition of ERK1/2 activities in a PI3K-dependent manner; (4) adenoviral infection of confluent Caco-2/15 cells with a constitutively active mutant of Akt1 strongly represses ERK1/2 activities; (5) inhibition of PI3K abolishes Akt activity but leads to a rapid and sustained activation of the MEK-ERK1/2 in confluent differentiating Caco-2/15 cells, but not in undifferentiated growing Caco-2/15 cells. Our data suggest that E-cadherin engagement leads to MEK/ERK inhibition in a PI3K/Akt-dependent pathway. This mechanism may account for the role of E-cadherin in proliferation/differentiation transition along the crypt-villus axis of the human intestinal epithelium.     

miR-137 effects on gastric carcinogenesis are mediated by targeting Cox-2-activated PI3K/AKT signaling pathway

The discovery of microRNAs (miRNAs) provided a new avenue for early diagnosis and treatment of GC. MiR-137 has been reported to be under-expressed and involved in various cell processes. However, the role of miR-137 in GC is less known. In this study, we show that miR-137 is under-expressed in GC and functions as a tumor suppressor through targeting Cyclooxygenase-2 (Cox-2), which subsequently suppresses the activation of PI3K/AKT signaling pathway both in vitro and in vivo. Moreover, restored Cox-2 expression partially abolished the tumor suppressive effects of miR-137 in GC cells, suggesting miR-137 may suppress GC carcinogenesis by targeting Cox-2.