MAP17 inhibits Myc-induced apoptosis through PI3K/AKT pathway activation

MAP17 is a non-glycosylated membrane-associated protein that has been shown to be over-expressed in human carcinomas, suggesting a possible role of this protein in tumorigenesis. However, very little is known about the molecular mechanism mediating the possible tumor promoting properties of MAP17. To analyze the effect of MAP17 on cell survival, we used Rat1 fibroblasts model where Myc over-expression promotes apoptosis in low serum conditions. In the present work, we report that over-expression of MAP17 protects Rat1a fibroblasts from Myc-induced apoptosis through reactive oxygen species (ROS)-mediated activation of the PI3K/AKT signaling pathway. MAP17-mediated survival was associated with absence of Bax translocation to the mitochondria and reduced caspase-3 activation. We show that a fraction of PTEN undergoes oxidation in MAP17-over-expressing cells. Furthermore, activation of AKT by MAP17 as measured by Thr308 phosphorylation was independent of PI3K activity. Importantly, modulation of ROS by antioxidant treatment prevented activation of AKT, restoring the level of apoptosis in serum-starved Rat1/c-Myc fibroblasts. Finally, over-expression of a dominant-negative mutant of AKT in MAP17-expressing clones makes them sensitive to serum depletion. Our data indicate that MAP17 protein activates AKT through ROS and this is determinant to confer resistance to Myc-induced apoptosis in the absence of serum.     

PI3K/AKT pathway activation in bladder carcinogenesis

The PI3K/AKT pathway is considered to play a major role in bladder carcinogenesis, but its relationships with other molecular alterations observed in bladder cancer remain unknown. We investigated PI3K/AKT pathway activation in a series of human bladder urothelial carcinomas (UC) according to PTEN expression, PTEN deletions and FGFR3, PIK3CA, KRAS, HRAS, NRAS and TP53 gene mutations. The series included 6 normal bladder urothelial samples and 129 UC (Ta n = 25, T1 n = 34, T2–T3–T4 n = 70). Expression of phospho‐AKT (pAKT), phospho‐S6‐Ribosomal Protein (pS6) (one downstream effector of PI3K/AKT pathway) and PTEN was evaluated by reverse phase protein Array. Expression of miR‐21, miR‐19a and miR‐222, known to regulate PTEN expression, was also evaluated. pAKT expression levels were higher in tumors than in normal urothelium (p < 0.01), regardless of stage and showed a weak and positive correlation with pS6 (Spearman coefficient R_S = 0.26; p = 0.002). No association was observed between pAKT or pS6 expression and the gene mutations studied. PTEN expression was decreased in PTEN‐deleted tumors, and in T1 (p = 0.0089) and T2–T3–T4 (p < 0.001) tumors compared to Ta tumors; it was also negatively correlated with miR‐19a (R_S = ?0.50; p = 0.0088) and miR‐222 (R_S = ?0.48; p = 0.0132), but not miR‐21 (R_S = ?0.27; p = 0.18) expression. pAKT and PTEN expressions were not negatively correlated, and, on the opposite, a positive and moderate correlation was observed in Ta (R_S = 0.54; p = 0.0056) and T1 (R_S = 0.56; p = 0.0006) tumors. Our study suggests that PI3K/AKT pathway activation occurs in the entire spectrum of bladder UC regardless of stage or known most frequent molecular alterations, and independently of low PTEN expression.     

吉西他滨对肺癌细胞凋亡及PI3K/AKT信号通路的影响

目的探讨吉西他滨对肺癌细胞凋亡及PI3K/AKT信号通路的影响。方法选取对数生长期的肺癌NCI-H292细胞随机分为吉西他滨组、阿霉素组和对照组,分别采用7μmol/L的吉西他滨、阿霉素与生理盐水处理,采用CCK-8法检测细胞增殖,Transwell小室检测细胞迁移与侵袭,Annexin V-PI双标记法检测细胞凋亡,Western blot实验检测PI3K和AKT蛋白表达。结果细胞处理后24h和48h,吉西他滨组和阿霉素组的细胞增殖指数均低于对照组,吉西他滨组低于阿霉素组,差异均有统计学意义(均P <0.05)。细胞处理后24h和48h,吉西他滨组和阿霉素组的细胞迁移与侵袭指数均低于对照组,吉西他滨组低于阿霉素组,差异均有统计学意义(均P <0.05)。细胞处理后24h和48h,吉西他滨组和阿霉素组的细胞凋亡指数均高于对照组,吉西他滨组高于阿霉素组,差异均有统计学意义(均P <0.05)。细胞处理后24h和48h,吉西他滨组和阿霉素组PI3K和AKT蛋白表达水平均低于对照组,吉西他滨组低于阿霉素组,差异均有统计学意义(均P <0.05)。结论吉西他滨可促进肺癌...     

三七皂苷R1调控PI3K/AKT/mTOR信号通路诱导人下咽鳞状细胞癌FaDu细胞凋亡和自噬北大核心

目的:探讨三七皂苷R1(notoginsenoside R1,NGR1)对人下咽鳞状细胞癌(hypopharyngeal squamous cell carcinoma,HSCC)FaDu细胞凋亡以及自噬的影响,并对其涉及的信号通路进行研究。方法:75μmol/L、150μmol/L、300μmol/L NGR1作用于FaDu细胞24 h后,采用MTT检测细胞增殖能力;流式细胞术检测细胞凋亡;自噬双标腺病毒检测自噬流;Western blot检测自噬相关蛋白LC3Ⅱ/LC3Ⅰ以及PI3K/AKT/mTOR信号通路相关蛋白表达水平。结果:NGR1能够抑制FaDu细胞的增殖并促进细胞凋亡;NGR1可诱导FaDu细胞自噬,并呈一定浓度依赖性;Western blot结果显示,NGR1作用于Fa Du细胞24 h后,LC3Ⅱ表达明显增加,而p-PI3K、p-AKT、p-m TOR表达相较于Control组明显下降。结论:NGR1可抑制Fa Du细胞增殖,诱导细胞凋亡与自噬,其机制可能与抑制PI3K/AKT/m TOR信号通路有关。     

Down-regulation of uPAR and uPA activates caspase-mediated apoptosis and inhibits the PI3K/AKT pathway

Urokinase plasminogen activator (uPA) and its receptor (uPAR) play a major role in invasion and proliferation. A growing body of evidence has suggested that the uPA system promotes tumor metastasis by several different mechanisms, and not just solely by breaking down the ECM. In this study we have used RNAi-mediated simultaneous down-regulation of uPAR and uPA to determine the signaling pathway molecules and caspase-mediated apoptosis. From our in vitro experiments, we have observed that plasmid-based RNAi-mediated down-regulation of uPAR and uPA in SNB19 human glioma cells caused a decrease in the levels of uPAR protein and uPA enzyme activities. In addition, we observed a decrease in the phosphorylation of the Ras-activated pathway molecules such as FAK, p38MAPK, JNK and ERK1/2, as well as the MEK-activated phosphatidylinositol 3-kinase (PI3k) pathway, and also retarded the dephosphorylation of p-AKTser473 and p-mTORser2448, indicative of a feedback signaling mechanism of the uPAR-uPA system. Activation of caspase 8 accompanied by the release of cytochrome c and cleavage of PARP was also observed and indicative of Fas-mediated apoptosis. The use of FMK-VAD-FAK peptides coupled with FITC indicated activation of polycaspases, which was accompanied by the presence of fragmented nuclei. Our studies provide evidence for the presence of a feedback response of the uPAR-uPA system indicative of the multifaceted role of uPAR, and also the therapeutic potential of simultaneously targeting uPAR and uPA in cancer patients.     

Lebectin increases N-cadherin-mediated adhesion through PI3K/AKT pathway

Cell adhesion molecules, including cadherins and integrins, play an essential role during tumor progression and represent potential targets for the development of new therapeutic agents. We previously showed that lebectin, a C-type lectin protein (CLP) issued from Macrovipera lebectina snake venom, inhibits integrin-mediated migration of IGR39 melanoma cells. Here we assessed whether lebectin modulates cell–cell adhesion. We demonstrated that lebectin promotes N-cadherin/catenin complex reorganization at cell–cell contacts, inducing a strengthening of intercellular adhesion. This reorganization is associated to phosphorylation of β-catenin on tyrosine 142 residue. Interestingly, lebectin acts on N-cadherin-mediated cell–cell contacts through PI3K/Akt pathway. This effect could contribute to the blockage of tumor cell migration previously observed.     

Osthole induces G2/M arrest and apoptosis in lung cancer A549 cells by modulating PI3K/Akt pathway

Background

To explore the effects of Osthole on the proliferation, cell cycle and apoptosis of human lung cancer A549 cells.

Methods

Human lung cancer A549 cells were treated with Osthole at different concentrations. Cell proliferation was measured using the MTT assay. Cell cycle was evaluated using DNA flow cytometry analysis. Induction of apoptosis was determined by flow cytometry and fluorescent microscopy. The expressions of Cyclin B1, p-Cdc2, Bcl-2, Bax, t-Akt and p-Akt were evaluated by Western blotting.

Results

Osthole inhibited the growth of human lung cancer A549 cells by inducing G2/M arrest and apoptosis. Western blotting demonstrated that Osthole down-regulated the expressions of Cyclin B1, p-Cdc2 and Bcl-2 and up-regulated the expressions of Bax in A549 cells. Inhibition of PI3K/Akt signaling pathway was also observed after treating A549 cells with Osthole.

Conclusions

Our findings suggest that Osthole may have a therapeutic application in the treatment of human lung cancer.     

PI3K／Akt／mTOR在表阿霉素抑制Jurkat细胞增殖和诱导凋亡中的作用

目的 探讨PI3K／Akt／mTOR信号通路在表阿霉素抑制人T细胞淋巴瘤细胞株Jurkat细胞增殖和诱导凋亡中的作用。方法 用0、1.25、2.5、5、10μmol／L表阿霉素和0、0.25、0.5、1、2μmol／L PI3K／mTOR双重抑制剂（NVP-BEZ235）对Jurkat细胞作用48h后,CCK-8试剂盒检测Jurkat细胞株增殖抑制情况;采用AnnexinⅤ／PE双染法流式细胞术检测上述药物作用Jurkat细胞48h的凋亡率以及5μmol／L表阿霉素和2μmol／L NVP BEZ235单独及联合作用Jurkat细胞0、12、24、36、48h的凋亡率;Western blotting法检测5、10μmol/L的表阿霉素作用Jurkat细胞0、6、12、24、48h,以及5μmol/L表阿霉素与2μmol/L NVP BEZ235单独及联合作用Jurkat细胞24、48h的PI3K／Akt／mTOR信号通路中Akt、mTOR、p70s6k等表达变化。结果 表阿霉素能够抑制Jurkat细胞增殖并诱导其凋亡,且凋亡作用呈浓度依赖性,5μmol／L表阿霉素作用Jurkat细胞48h的凋亡率为57.72％。在表阿霉素诱导Jurkat细胞凋亡过程中伴随Akt、mTOR、p70s6k的表达变化, NVP-BEZ235能够降低Jurkat细胞Akt、p70s6k的磷酸化水平,显著提高表阿霉素诱导Jurkat细胞凋亡的作用,5μmol／L表阿霉素和2μmol／L NVP-BEZ235联合作用Jurkat细胞48h的凋亡率达78.31％,明显高于5μmol／L表阿霉素的57.72％。结论 表阿霉素抑制Jurkat细胞增殖和诱导凋亡与PI3K／Akt／mTOR信号通路有关,当该通路抑制剂与表阿霉素联用时,Jurkat细胞对于表阿霉素敏感性有一定程度的提高。     

Strategies for co-targeting the PI3K/AKT/mTOR pathway in NSCLC

The PI3K/AKT/mTOR pathway regulates cell growth and proliferation and is often dysregulated in cancer due to mutation, amplification, deletion, methylation and post-translational modifications. We and others have shown that activation of this pathway in non-small cell lung cancer (NSCLC) leads to a more aggressive disease which correlates to poor prognosis for patients. A multitude of selective inhibitors are in development which target key regulators in this pathway, however the success of PI3K targeted inhibition has been hampered by a high rate of innate and acquired resistance. Response to PI3K inhibition may be improved by co-targeting potential mediators of resistance, such as related cell surface receptors or other intracellular signaling pathways which cross-talk with the PI3K pathway. Inhibition of the PI3K pathway may also overcome radioresistance, chemoresistance and immune evasion in NSCLC. The identification of appropriate patient cohorts who will benefit from PI3K co-targeted inhibition strategies will be key to the success of these inhibitors.     

PI3K/AKT/mTOR信号通路抑制剂在淋巴瘤中的研究进展*

磷脂酰肌醇-3 激酶（phosphatidylinositol 3-kinase,PI 3K）- 蛋白激酶B（protein kinaseB ,PKB ,又称AKT ）- 雷帕霉素靶蛋白（mammalian target of  rapamycin,mTOR）信号通路与细胞的生长、增殖、分化、凋亡、代谢等密切相关,在多种实体肿瘤中已发现该信号通路的异常。近年来,以抑制该通路特定位点的靶向治疗已成为抗肿瘤的研究热点。许多该位点新型抑制剂也已进入淋巴瘤的临床试验中,本文就该通路在淋巴瘤中的活化状态及各个分子靶点抑制剂的研究进展做一综述。     

PI3K/AKT/mTOR通路抑制剂在膀胱癌中的研究进展

磷脂酰肌醇3-激酶(PI3K)/AKT/哺乳动物雷帕霉素靶标(mTOR)通路在人类肿瘤的恶性转化及其随后的生长、增殖和转移中起重要作用。临床前研究表明,PI3K/AKT/mTOR通路在膀胱癌中经常被激活。因此,这一通路被认为是膀胱癌治疗干预的候选通路,针对该通路不同成分的抑制剂正处于临床开发的不同阶段。在这里,重点介绍我们对PI3K/AKT/mTOR通路的最新研究进展,并讨论以该通路为靶点的治疗药物作为膀胱癌治疗药物的发展障碍及发展潜力。     

Targeting the PI3K/AKT/mTOR pathway in estrogen receptor-positive breast cancer

Approximately 70−75% of breast cancers express the estrogen receptor (ER), indicating a level of dependence on estrogen for growth. Endocrine therapy is an important class of target-directed therapy that blocks the growth-promoting effects of estrogen via ER. Although endocrine therapy continues to be the cornerstone of effective treatment of ER-positive (ER+) breast cancer, many patients with advanced ER+ breast cancer encounter de novo or acquired resistance and require more aggressive treatment such as chemotherapy. Novel approaches are needed to augment the benefit of existing endocrine therapies by prolonging time to disease progression, preventing or overcoming resistance, and delaying the use of chemotherapy.     

RICTOR involvement in the PI3K/AKT pathway regulation in melanocytes and melanoma

Several studies have highlighted the importance of the PI3K pathway in melanocytes and its frequent over-activation in melanoma. However, little is known about regulation of the PI3K pathway in melanocytic cells. We showed that normal human melanocytes are less sensitive to selective PI3K or mTOR inhibitors than to dual PI3K/mTOR inhibitors. The resistance to PI3K inhibitor was due to a rapid AKT reactivation limiting the inhibitor effect on proliferation. Reactivation of AKT was linked to a feedback mechanism involving the mTORC2 complex and in particular its scaffold protein RICTOR. RICTOR overexpression in melanocytes disrupted the negative feedback, activated the AKT pathway and stimulated clonogenicity highlighting the importance of this feedback to restrict melanocyte proliferation. We found that the RICTOR locus is frequently amplified and overexpressed in melanoma and that RICTOR over-expression in NRAS-transformed melanocytes stimulates their clonogenicity, demonstrating that RICTOR amplification can cooperate with NRAS mutation to stimulate melanoma proliferation. These results show that RICTOR plays a central role in PI3K pathway negative feedback in melanocytes and that its deregulation could be involved in melanoma development.     

低表达DJ-1调控PI3K/AKT通路对肺癌细胞增殖、凋亡的影响

目的:探讨低表达DJ-1对肺癌细胞增殖凋亡及PI3K/AKT通路的影响。方法:采用Western blot检测肺癌细胞系中DJ-1蛋白的表达;以脂质体法转染干扰SK-MES-1细胞中DJ-1蛋白的表达后,MTT法检测细胞的增殖变化,流式细胞仪检测细胞的凋亡情况,Western blot检测细胞中p-AKT和AKT蛋白的表达水平;将PI3K/AKT通路抑制剂LY294002处理SK-MES-1细胞48 h后,MTT法和流式细胞仪分别检测细胞的增殖和凋亡情况,Western blot检测细胞中p-AKT和AKT蛋白的表达。结果:与正常肺上皮BEAS-2B细胞相比,肺腺癌A549细胞和肺鳞癌SK-MES-1细胞中DJ-1蛋白的相对表达量均显著升高,且SK-MES-1细胞中DJ-1蛋白的表达量高于A549细胞,差异均有统计学意义（P＜0.05）。转染后siRNA DJ-1组细胞中DJ-1蛋白的表达量明显低于对照组（P＜0.05）;与对照组相比,转染24 h后siRNA DJ-1组细胞的吸光值（OD值）变化不显著（P＞0.05）,而转染48 h和72 h后细胞的OD值明显降低（P＜0.05）;转染48 h后,与对照组相比,siRNA DJ-1组细胞的凋亡率显著升高（P＜0.05）,p-AKT/AKT值显著降低（P＜0.05）。SK-MES-1细胞经抑制剂LY294002处理48 h后,细胞的增殖凋亡趋势与下调DJ-1表达的结果相一致。结论:DJ-1在肺癌细胞中高表达,下调其表达能够抑制细胞增殖,促进细胞凋亡,其作用机制可能与PI3K/AKT信号通路有关。     

白花丹醌通过CXCL8/PI3K/AKT糖酵解通路抑制结肠癌细胞增殖、促进凋亡

目的:观察白花丹醌对结肠癌细胞Caco-2增殖、凋亡的影响,探究其潜在的作用机制。方法:运用CCK8法、流式细胞术检测不同浓度白花丹醌（4、8、12 μmol/L）处理的Caco-2细胞的增殖抑制率、凋亡率。不做任何处理的Caco-2细胞设为Control;脂质体法将si-NC组（转染si-NC）、si-CXCL8组（转染si-CXCL8）转染至Caco-2细胞;8 μmol/L的白花丹醌与0.5%DMSO处理的Caco-2细胞设为8 μmol/L+DMSO组;8 μmol/L的白花丹醌分别与z-VAD-FMK、740Y-P处理的Caco-2细胞设为8 μmol/L+z-VAD-FMK组、8 μmol/L+740Y-P组。RT-qPCR、Western blot实验检测细胞中CXCL8的mRNA、蛋白表达,CXCL8、M2-型丙酮酸激酶（M2 pyruvate kinase, PKM2）、L-乳酸脱氢酶A（lactate dehydrogenase A,LDHA）、人α-烯醇化酶(apha-enolase,ENO1)、葡萄糖磷酸异构酶（glucose phosphate isomerase,GPI）、磷酸化磷脂酰肌醇3激酶（phosphorylated phosphatidylinositol 3 kinase,p-PI3K）、磷酸化蛋白激酶B（phosphorylated protein kinase B,p-AKT）的蛋白表达。结果:与Control组相比,白花丹醌（4、8、12 μmol/L）呈浓度依赖性促进Caco-2细胞增殖抑制率、凋亡率升高,抑制CXCL8的mRNA和蛋白表达。与8 μmol/L+DMSO组相比,8 μmol/L+z-VAD-FMK组细胞的增殖抑制率、凋亡率明显降低,CXCL8的mRNA和蛋白表达明显升高（P＜0.05）。白花丹醌（4、8、12 μmol/L）呈浓度依赖性抑制PKM2、LDHA、p-PI3K、p-AKT的蛋白表达。si-CXCL8组PKM2、LDHA、p-PI3K、p-AKT的蛋白表达明显低于si-NC组。740Y-P明显减弱白花丹醌对Caco-2细胞增殖抑制率和凋亡率的促进作用。结论:白花丹醌抑制结肠癌细胞增殖,促进凋亡,其潜在的作用机制与CXCL8/PI3K/AKT糖酵解通路有关。     

大黄素诱导裸鼠体内白血病K562细胞凋亡过程中PI3K/AKT通路相关分子表达的变化

目的:观察大黄素作用后裸鼠体内白血病K562细胞PI3K/AKT信号通路的分子变化,以探讨大黄素是否依赖PI3K/AKT信号通路参与K562细胞凋亡发生。方法:建立裸鼠K562细胞皮下移植瘤模型,腹腔连续给药12d后,处死裸鼠,称取瘤体质量,计算抑瘤率。采用HE染色和透射电子显微镜观察肿瘤细胞的凋亡情况。应用RT-PCR法检测肿瘤组织中PI3K、AKT和FoxO3a的mRNA表达水平。蛋白质印迹法检测肿瘤组织中PI3K、AKT和FoxO3a蛋白的表达水平。结果:低、中、高剂量组大黄素作用后肿瘤相对体积(V/V0)分别为8.90±0.24、5.62±0.17和2.06±0.31,与0.9%氯化钠溶液对照组(V/V0为11.83±0.47)相比,大黄素处理组的肿瘤体积明显缩小,差异具有统计学意义(P<0.01)。光学显微镜和电子显微镜观察发现,大黄素能够诱导K562细胞发生明显的凋亡。RT-PCR结果表明,不同剂量的大黄素能够引起PI3K和AKT mRNA的表达下调,而FoxO3a mRNA表达上调,且有剂量依赖性。蛋白质印迹法结果表明,大黄素处理组移植瘤组织中PI3K、AKT蛋白表达水平明显降低,而FoxO3a蛋白水平明显升高。结论:大黄素能够明显抑制人白血病K562细胞裸鼠移植瘤的生长,其机制可能与其抑制PI3K/AKT信号转导通路有关。