Regulation of survivin by PI3K/Akt/p70S6K1 pathway

PI3K activation is commonly observed in many human cancer cells. Survivin expression is elevated in cancer cells, and induced by some growth factors through PI3K activation. However, it is not clear whether PI3K activation is sufficient to induce survivin expression. To investigate the role of PI3K pathway in the regulation of survivin, we expressed an active form of PI3K, v-P3k in chicken embryonic fibroblast cells (CEF), and found that overexpression of PI3K-induced survivin mRNA expression. Forced expression of wild-type but not mutant tumor suppressor PTEN in CEF decreased survivin mRNA levels. PI3K regulates survivin expression through Akt activation. To further investigate downstream target of PI3K and Akt in regulating the expression of survivin mRNA, we found that PI3K and Akt-induced p70S6K1 activation and that overexpression of p70S6K1 alone was sufficient to induce survivin expression. The treatment of CEF cells by rapamycin decreased the survivin mRNA expression. This result demonstrated that p70S6K1 is an important target downstream of PI3K and Akt in regulating suvivin mRNA expression. The knockdown of survivin mRNA expression by its specific siRNA induced apoptosis of cancer cells when the cells were treated with LY294002 or taxol. Taken together, these results demonstrated that PI3K/Akt/p70S6K1 pathway is essential for regulating survivin mRNA expression.     

Knockdown of LASP2 inhibits the proliferation,migration, and invasion of cervical cancer cells

LIM and SH3 protein 2 (LASP2) belongs to nebulin family. It has been proven that LASP2 is involved in several cancers; however, its role in cervical cancer is unclear. Herein, we showed that LASP2 was highly expressed in cervical cancer tissues and cell lines. To knockdown LASP2 in cervical cancer cells, small interfering RNAs (siRNAs) targeting LASP2 (si-LASP2) were used. We found that cell proliferation, migration/invasion were markedly reduced after si-LASP2 transfection. A significant increase in E-cadherin expression, and decrease in N-cadherin and vimentin expressions were observed in si-LASP2 transfected cervical cancer cells. Knockdown of LASP2 caused significant inhibitory effect on the PI3K/Akt pathway. Treatment with the activator of the PI3K/Akt pathway, 740Y-P, abolished the effects of si-LASP2 transfection on cervical cancer cells. These findings suggested that LASP2 may be an oncogene through regulating the PI3K/Akt pathway in cervical cancer.     

KAI1/CD82 decreases Rac1 expression and cell proliferation through PI3K/Akt/mTOR pathway in H1299 lung carcinoma cells

Although the KAI1/CD82 protein has been reported to inhibit cell metastasis in many studies, its mechanism of action has not yet been fully elucidated. In the present study, we investigated the possible effects of KAI1/CD82 on the metastatic phenotype in H1299 lung carcinoma cells. These studies were based on the pivotal role that the acquisition of motile phenotype plays on the initial steps of metastasis. KAI1/CD82‐mediated morphological changes were observed using phase contrast microscopy. We report here, that a KAI1/CD82‐induced phenotypic change was involved in the decrease of Rac1 expression and GTPase activity. However, we found that KAI1/CD82 did not regulate Rac1 mRNA levels. This suggests the existence of another regulatory mechanism of Rac1 protein maturation or activation. To identify the signaling pathway of Rac1 regulation, we investigated the PI3K/Akt/mTOR pathway, since the PI3K/Akt pathway regulates Rac1 activation and mTOR is known to play a regulatory role in protein translation. H1299/CD82‐transfectants showed lower mTOR expression and cell growth than the control group. The data obtained from this study suggested that KAI1/CD82 decreased the metastatic phenotype of H1299 lung carcinoma cells by down‐regulating Rac1 expression through the PI3K/Akt/mTOR pathway. Copyright © 2008 John Wiley & Sons, Ltd.     

PI3K/PTEN signaling in tumorigenesis and angiogenesis

The phosphatidyl inositol 3-kinase (PI3K) can be activated by a variety of extracellular signals and involved in a number of cellular processes including cell proliferation, survival, protein synthesis, and tumor growth. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is an antagonist of PI3K. The alterations of PI3K pathway such as activation of oncogenes, gene amplification, and inactivation of tumor suppressors, commonly occur in many human cancers. Angiogenesis is required for tumor growth and metastasis when the tumor reaches more than 1 mm in diameter. Recent studies have shown that PI3K and Akt play an important role in regulating tumor growth and angiogenesis through VEGF and HIF-1 expression. PI3K regulates the expression of these two proteins through HDM2 and p70S6K1 in human cancer cells. The frequent dysregulation of the PI3K/PTEN pathway in human cancer demonstrates that this pathway is an appropriate target for cancer therapeutics. In this review, we describe the recent advances in understanding the PI3K/PTEN pathway, the role and mechanism of PI3K in regulating tumor growth and angiogenesis, and the potential therapeutic opportunities for targeting this pathway for cancer treatment.     

Study of the pathways involved in apoptosis induced by PI3K inhibition in cerebellar granule neurons

In the present study we focused in the PI3K/Akt pathway which plays a key role in neuronal survival. Here we show that inhibition of PI3K/Akt by means of LY294002 induces apoptosis via a caspase-dependent and calpain-independent pathway in cerebellar granule neurons (CGNs). This finding was confirmed using zVAD-fmk, a widely caspase inhibitor that prevents apoptosis. For this purpose, we compared two models of apoptosis in CGNs, namely inhibition of PI3K/Akt, and serum potassium deprivation (S/K deprivation). In contrast to the S/K deprivation model, caspase-3 was not activated when PI3K is inhibited. Likewise, CDK5 activation was not involved in this apoptotic process, because calpain activation is responsible for the formation of CDK5/p25 neurotoxic form. However, S/K deprivation activated calpain, as it is shown by α-spectrin breakdown, and favoured the formation of CDK5/p25. Moreover, although PI3K/Akt inhibition enhanced pRbser780 phosphorylation, no increase in the expression of cell-cycle proteins, namely: cyclin D, cyclin E, CDK2 or CDK4, was detected. Furthermore, BrdU incorporation assay did not shown any increase in DNA synthesis. Likewise, PI3K/Akt inhibition increased GSK3β activity and c-Jun phosphorylation, which implicates these two pathways in this apoptotic route. Although previous reports suggest that apoptosis induced in CGNs by LY294002 and S/K deprivation causes PI3K inhibition and increases GSK3β activity and c-Jun phosphorylation activation, our results demonstrate substantial differences between them and point to a key role of GSK3β in the apoptosis induced in CGNs in the two models tested.     

The hVps34‐SGK3 pathway alleviates sustained PI3K/Akt inhibition by stimulating mTORC1 and tumour growth

We explore mechanisms that enable cancer cells to tolerate PI3K or Akt inhibitors. Prolonged treatment of breast cancer cells with PI3K or Akt inhibitors leads to increased expression and activation of a kinase termed SGK3 that is related to Akt. Under these conditions, SGK3 is controlled by hVps34 that generates PtdIns(3)P, which binds to the PX domain of SGK3 promoting phosphorylation and activation by its upstream PDK1 activator. Furthermore, under conditions of prolonged PI3K/Akt pathway inhibition, SGK3 substitutes for Akt by phosphorylating TSC2 to activate mTORC1. We characterise 14h, a compound that inhibits both SGK3 activity and activation in vivo, and show that a combination of Akt and SGK inhibitors induced marked regression of BT‐474 breast cancer cell‐derived tumours in a xenograft model. Finally, we present the kinome‐wide analysis of mRNA expression dynamics induced by PI3K/Akt inhibition. Our findings highlight the importance of the hVps34‐SGK3 pathway and suggest it represents a mechanism to counteract inhibition of PI3K/Akt signalling. The data support the potential of targeting both Akt and SGK as a cancer therapeutic.     

PI3K/Akt/mTOR信号通路与自噬及肿瘤的关系

自噬是一种以胞质内出现双层膜结构包裹长寿命蛋白和细胞器的自噬体为特征的细胞“自我消化”过程,在维持细胞内稳态、发育、肿瘤发生和感染中发挥重要作用。近来,诸多研究表明,自噬作为一把“双刃剑”,对肿瘤的发生发展既有促进作用,也有抑制作用。PI3K/Akt/mTOR通路由PI3激酶(PI3K)、蛋白激酶B（PKB/Akt）和哺乳动物类雷帕霉素靶蛋白（mTOR）3个作用分子组成,是一个中心的调节机构,对肿瘤细胞的生长与增殖有促进作用,同时对自噬进行抑制。本文就PI3K/Akt/mTOR通路与自噬及肿瘤发生发展的关系作一综述。     

Effect of orthodontic force on the expression of PI3K,Akt, and P70S6 K in the human periodontal ligament during orthodontic loading

The mammalian target of rapamycin (mTOR) is an atypical serine/threonine protein kinases involved in the regulation of cell growth, proliferation, and differentiation through the PI3K/Akt/mTOR/P70S6 K signalling pathway. P70S6 K as a downstream molecule of mTOR is activated by phosphorylation and subsequently promotes the synthesis of ribosomal and translational proteins. In this study, we investigated the role of PI3K, Akt, and P70S6 K in human periodontal tissue remodelling during orthodontic loading. The prepared tissue specimens taken from 4 extracted premolars were processed for immunolabelling. The changes in the expression of PI3K, Akt, and P70S6 K in the periodontal tissues were detected by real‐time quantitative‐polymerase chain reaction and Western blot analysis. The results from real‐time quantitative‐polymerase chain reaction and Western blot both showed that the expression of PI3K, Akt, and P70S6 K in the experimental group began to increase at 3 days and increased significantly at 10 days, then decreased approaching the control group level at 28 days. Our findings showed that the expression of PI3K, Akt, and P70S6 K in human periodontal ligament demonstrated a variability during the orthodontic loading, which suggested that the PI3K/Akt/mTOR/P70S6 K signal pathway was involved in orthodontic tooth movement and played a role in the process of periodontium remodelling.     

Reciprocal regulation of Notch and PI3K/Akt signalling in T-ALL cells in vitro

Notch signalling plays an important role in hematopoiesis and in the pathogenesis of T-ALL. Notch is known to interact with Ras and PTEN/PI3K (phosphoinositide-3 kinase)/Akt pathways. We investigated the interaction of Notch with these pathways and the possible reciprocal regulation of these signalling systems in T-ALL cells in vitro. Our analyses indicate that the PI3K/Akt pathway is constitutively active in the four T-ALL cell lines tested. Akt phosphorylation was not altered by the sequestration of growth factors, that is, Akt activation seems to be less dependent on but not completely independent of growth factors, possibly being not subject to negative feedback regulation. PTEN expression was not detected in 3/4 cell lines tested, suggesting the loss of PTEN-mediated Akt activation. Inhibition of the PI3K/Akt pathway arrests growth and enhances apoptosis, but with no modulation of expression of Bax-alpha and Bcl-2 proteins. We analysed the relationship between Notch-1 and the PI3K/Akt signalling and show that inhibition of the Akt pathway changes Notch expression; Notch-1 protein decreased in all the cell lines upon treatment with the inhibitor. Our studies strongly suggest that Notch signalling interacts with PI3K/Akt signalling and further that this occurs in the absence of PTEN expression. The consequences of this to the signalling outcome are yet unclear, but we have uncovered a significant inverse relationship between Notch and PI3K/Akt pathway, which leads us to postulate the operation of a reciprocal regulatory loop between Notch and Ras-PI3K/Akt in the pathogenesis of T-ALL.     

Ribosomal protein L22-like1 promotes prostate cancer progression by activating PI3K/Akt/mTOR signalling pathway

Prostate cancer (PCa) is one of the most common malignancies in men. Ribosomal protein L22-like1 (RPL22L1), a component of the ribosomal 60 S subunit, is associated with cancer progression, but the role and potential mechanism of RPL22L1 in PCa remain unclear. The aim of this study was to investigate the role of RPL22L1 in PCa progression and the mechanisms involved. Bioinformatics and immunohistochemistry analysis showed that the expression of RPL22L1 was significantly higher in PCa tissues than in normal prostate tissues. The cell function analysis revealed that RPL22L1 significantly promoted the proliferation, migration and invasion of PCa cells. The data of xenograft tumour assay suggested that the low expression of RPL22L1 inhibited the growth and invasion of PCa cells in vivo. Mechanistically, the results of Western blot proved that RPL22L1 activated PI3K/Akt/mTOR pathway in PCa cells. Additionally, LY294002, an inhibitor of PI3K/Akt pathway, was used to block this pathway. The results showed that LY294002 remarkably abrogated the oncogenic effect of RPL22L1 on PCa cell proliferation and invasion. Taken together, our study demonstrated that RPL22L1 is a key gene in PCa progression and promotes PCa cell proliferation and invasion via PI3K/Akt/mTOR pathway, thus potentially providing a new target for PCa therapy.     

Regulation of pancreatic duct cell differentiation by phosphatidylinositol-3 kinase

We have previously demonstrated that the phosphatidylinositol-3 kinase (PI3K)/Akt signaling is essential for pancreatic regeneration after partial pancreatectomy in mice. In the present study, we examined a role of PI3K/Akt signaling for pancreatic duct cell differentiation into insulin-producing cells. Epithelial-like cells were isolated from mouse pancreas and confirmed to be positive for a duct cell marker cytokeratin-20 (CK-20) but negative for insulin. Incubation of these cells with epidermal growth factor, exhibited a gradual increase in Akt phosphorylation and expression of pancreatic duodenal homeobox-1 (PDX-1), a regulator of β-cell differentiation. Three weeks later, these CK-20-positive cells were noted to express insulin as determined by immunofluorescent double-staining. Akt phosphorylation, PDX-1 expression, and insulin production were effectively reduced by blocking the PI3K/Akt pathway using siRNA to the p85α regulatory subunit of PI3K. Our results demonstrate that PI3K/Akt activation has a critical role for pancreatic duct cell differentiation into insulin-producing cells.     

FUT family mediates the multidrug resistance of human hepatocellular carcinoma via the PI3K/Akt signaling pathway

The fucosyltransferase (FUT) family is the key enzymes in cell-surface antigen synthesis during various biological processes such as tumor multidrug resistance (MDR). The aim of this work was to analyze the alteration of FUTs involved in MDR in human hepatocellular carcinoma (HCC) cell lines. Using mass spectrometry (MS) analysis, the composition profiling of fucosylated N-glycans differed between drug-resistant BEL7402/5-FU (BEL/FU) cells and the sensitive line BEL7402. Further analysis of the expressional profiles of the FUT family in three pairs of parental and chemoresistant human HCC cell lines showed that FUT4, FUT6 and FUT8 were predominant expressed in MDR cell lines. The altered levels of FUT4, FUT6 and FUT8 were responsible for changed drug-resistant phenotypes of BEL7402 and BEL/FU cells both in vitro and in vivo. In addition, regulating FUT4, FUT6 or FUT8 expression markedly modulated the activity of the phosphoinositide 3 kinase (PI3K)/Akt signaling pathway and MDR-related protein 1 (MRP1) expression. Inhibition of the PI3K/Akt pathway by its specific inhibitor wortmannin, or by Akt small interfering RNA (siRNA), resulted in decreased MDR of BEL/FU cells, partly through the downregulation of MRP1. Taken together, our results suggest that FUT4-, FUT6- or FUT8-mediated MDR in human HCC is associated with the activation of the PI3K/Akt pathway and the expression of MRP1, but not of P-gp, indicating a possible novel mechanism by which the FUT family regulates MDR in human HCC.     

Retracted: Upregulated microRNA-15b alleviates ovarian cancer through inhitbition of the PI3K/Akt pathway by targeting LPAR3

Ovarian cancer characterizes as the fourth leading consequence of death associated with cancer for women. Accumulating evidence underscores the vital roles of microRNAs (miRNAs) in preventing ovarian cancer development. Besides, induction of the phosphatidylinositol-3 kinase/serine/threonine kinase (PI3K/Akt) pathway associated with the ovarian cancer cell migration and invasion. The study aims to examine the effects of miR-15b on the proliferation, apoptosis, and senescence of human ovarian cancer cells by binding to lysophosphatidic acid receptor 3 (LPAR3) with the involvement of the PI3K/Akt pathway. The positive expression of LPAR3 protein was detected by immunohistochemistry. Then the interaction between miR-15b and LPAR3 was examined. The possible role of miR-15b in ovarian cancer was explored using gain- and loss-of-function experiments. Subsequently, the functions of miR-15b on PI3K/Akt pathway, proliferation, migration, invasion, senescence and apoptosis of ovarian cancer cells were assessed. Furthermore, in vivo tumorigenicity assay in nude mice was performed. LPAR3 was overexpressed, whereas miR-15b was poorly expressed in ovarian cancer tissues. LPAR3 is a direct target of miR-15b. Restored miR-15b promoted Bax expression, apoptosis, and senescence, inhibited expression of LPAR3 and Bcl-2, the extent of PI3K and Akt phosphorylation, as well as ovarian cancer cell proliferation, migration, and invasion. Further, tumor growth was observed to be prevented by miR-15b overexpression. Collectively, our study demonstrates that miR-15b represses the proliferation and drives the senescence and apoptosis of ovarian cancer cells through the suppression of LPAR3 and the PI3K/Akt pathway, highlighting an antitumorigenic role of miR-15b.     

低浓度哇巴因对负鼠肾小管上皮细胞增殖的影响

目的:用低血清培养液来模拟肾脏供血不足的营养不良状态,研究低浓度哇巴因对低血清培养下OK细胞(负鼠肾小管上皮细胞)增殖的影响。方法:用低浓度哇巴因(1-30n M)处理0.2%血清培养下OK细胞,MTT实验和Brdu掺入法检测哇巴因对OK细胞增殖的影响;Western blot检测Akt和ERK1/2的磷酸化水平;用LY294002和PD98059分别抑制PI3K/Akt和ERK1/2蛋白激酶活性,观察抑制PI3K/Akt和ERK1/2对哇巴因促进OK细胞增殖的影响。结果:低浓度哇巴因(1-30n M)促进OK细胞的增值,上调OK细胞中Akt和ERK1/2磷酸化水平。用LY294002和PD98059特异抑制Akt和ERK1/2的活化能够抑制哇巴因的促增殖作用。结论:低浓度哇巴因(1-10n M)能够促进OK细胞的增值,PI3K/Akt和ERK1/2信号通路参与哇巴因对OK细胞促增殖作用的调节。     

Acquisition of epithelial–mesenchymal transition and cancer stem cell phenotypes is associated with activation of the PI3K/Akt/mTOR pathway in prostate cancer radioresistance

Radioresistance is a major challenge in prostate cancer (CaP) radiotherapy (RT). In this study, we investigated the role and association of epithelial–mesenchymal transition (EMT), cancer stem cells (CSCs) and the PI3K/Akt/mTOR signaling pathway in CaP radioresistance. We developed three novel CaP radioresistant (RR) cell lines (PC-3RR, DU145RR and LNCaPRR) by radiation treatment and confirmed their radioresistance using a clonogenic survival assay. Compared with untreated CaP-control cells, the CaP-RR cells had increased colony formation, invasion ability and spheroid formation capability (P<0.05). In addition, enhanced EMT/CSC phenotypes and activation of the checkpoint proteins (Chk1 and Chk2) and the PI3K/Akt/mTOR signaling pathway proteins were also found in CaP-RR cells using immunofluorescence, western blotting and quantitative real-time PCR (qRT-PCR). Furthermore, combination of a dual PI3K/mTOR inhibitor (BEZ235) with RT effectively increased radiosensitivity and induced more apoptosis in CaP-RR cells, concomitantly correlated with the reduced expression of EMT/CSC markers and the PI3K/Akt/mTOR signaling pathway proteins compared with RT alone. Our findings indicate that CaP radioresistance is associated with EMT and enhanced CSC phenotypes via activation of the PI3K/Akt/mTOR signaling pathway, and that the combination of BEZ235 with RT is a promising modality to overcome radioresistance in the treatment of CaP. This combination approach warrants future in vivo animal study and clinical trials.     

沉默脂肪细胞增强子结合蛋白2通过PI3K/Akt途径抑制肝癌细胞增殖和迁移

脂肪细胞增强子结合蛋白2(AEBP2)作为多梳抑制复合物2(PRC2)的组成蛋白质,参与多种肿瘤细胞的增殖和迁移,然而其在肝癌中的作用尚不清楚。本研究基于UALCAN和Kaplan-Meier Plotter数据库分析发现,AEBP2在肝癌组织中高表达,并且与患者的不良预后呈正相关。实时荧光定量PCR和蛋白质印迹结果证实,AEBP2在肝癌细胞中的表达高于正常肝细胞。在HepG2和Huh-7细胞中转染AEBP2 siRNA,平板克隆、CCK-8、流式细胞术、划痕愈合和Transwell结果显示,沉默AEBP2可以抑制肝癌细胞增殖、迁移和侵袭,并促进细胞凋亡(P＜0.05)。免疫荧光检测和蛋白质印迹结果显示,沉默AEBP2能够抑制肝癌细胞上皮-间质转化(EMT)(P＜0.05)。生物信息学分析结果表明,AEBP2参与调控PI3K/Akt信号通路。蛋白质印迹结果证实,沉默AEBP2能下调PI3K、p-AKT (S473)、mTOR、MMP-2和MMP-9的蛋白质表达水平(P＜0.05)。此外,沉默AEBP2对HepG2细胞迁移和侵袭的影响可被PI3K/Akt通路激动剂胰岛素样生长因子1(IGF-1)部分逆转(P＜0.01)。综上所述,AEBP2可能通过调节PI3K/Akt途径促进肝癌细胞增殖和迁移。本研究为AEBP2在肝癌中的作用提供理论依据。     

Erianin induces triple-negative breast cancer cells apoptosis by activating PI3K/Akt pathway

Background: Triple-negative breast cancer (TNBC) is a refractory subtype of breast cancer, 25–30% of which have dysregulation in the PI3K/AKT pathway. The present study investigated the anticancer effect of erianin on TNBC cell line and its underlying mechanism.Methods: After treatment with erianin, MTT assay was employed to determine the MDA-MB-231 and EFM-192A cell proliferation, the nucleus morphological changes were observed by DAPI staining. The cell cycle and apoptotic proportion were detected by flow cytometry. Western blot was performed to determine the cell cycle and apoptosis-related protein expression and PI3K pathways. Finally, the antiproliferative activity of erianin was further confirmed by adding or not adding PI3K agonists SC79.Results: Erianin inhibited the proliferation of MDA-MB-231 and EFM-192A cells in a dose-dependent manner, the IC₅₀ were 70.96 and 78.58 nM, respectively. Erianin could cause cell cycle arrest at the G₂/M phase, and the expressions of p21 and p27 were up-regulated, while the expressions of CDK1 and Cyclin B1 were down-regulated. Erianin also induced apoptosis via the mitochondrial pathway, with the up-regulation of the expression of Cyto C, PARP, Bax, active form of Caspase-3, and Caspase-9. Furthermore, p-PI3K and p-Akt expression were down-regulated by erianin. After co-incubation with SC79, the cell inhibition rate of erianin was decreased, which further confirmed that the attenuated PI3K/Akt pathway was relevant to the pro-apoptotic effect of erianin.Conclusions: Erianin can inhibit the proliferation of TNBC cells and induce cell cycle arrest and apoptosis, which may ascribe to the abolish the activation of the PI3K/Akt pathway.