PI3K/Akt signalling pathway and cancer

Phosphatidylinositol-3 kinases, PI3Ks, constitute a lipid kinase family characterized by their ability to phosphorylate inositol ring 3'-OH group in inositol phospholipids to generate the second messenger phosphatidylinositol-3,4,5-trisphosphate (PI-3,4,5-P(3)). RPTK activation results in PI(3,4,5)P(3) and PI(3,4)P(2) production by PI3K at the inner side of the plasma membrane. Akt interacts with these phospholipids, causing its translocation to the inner membrane, where it is phosphorylated and activated by PDK1 and PDK2. Activated Akt modulates the function of numerous substrates involved in the regulation of cell survival, cell cycle progression and cellular growth. In recent years, it has been shown that PI3K/Akt signalling pathway components are frequently altered in human cancers. Cancer treatment by chemotherapy and gamma-irradiation kills target cells primarily by the induction of apoptosis. However, the development of resistance to therapy is an important clinical problem. Failure to activate the apoptotic programme represents an important mode of drug resistance in tumor cells. Survival signals induced by several receptors are mediated mainly by PI3K/Akt, hence this pathway may decisively contribute to the resistant phenotype. Many of the signalling pathways involved in cellular transformation have been elucidated and efforts are underway to develop treatment strategies that target these specific signalling molecules or their downstream effectors. The PI3K/Akt pathway is involved in many of the mechanisms targeted by these new drugs, thus a better understanding of this crossroad can help to fully exploit the potential benefits of these new agents.     

Chemoresistance in breast cancer: PI3K/Akt pathway inhibitors vs the current chemotherapy

Breast cancer is the most prevalent type of cancer among women. Several types of drugs, targeting the specific proteins expressed on the breast cancer cell surface (such as receptor tyrosine kinases and immune checkpoint regulators) and proteins involved in cell cycle and motility (including cyclin-dependent kinases, DNA stabilisers, and cytoskeleton modulators) are approved for different subtypes of breast cancer. However, breast cancer also has a poor response to conventional chemotherapy due to intrinsic and acquired resistance, and an Akt fingerprint is detectable in most drug-resistant cases. Overactivation of Akt and its upstream and downstream regulators in resistant breast cancer cells is considered a major potential target for novel anti-cancer therapies, suggesting that Akt signalling acts as a cellular mechanism against chemotherapy. The present review has shown that sustained activation of Akt results in resistance to different types of chemotherapy. Akt signalling plays a cellular defence role against chemotherapy and (1) enhances multi-drug resistance, (2) increases reactive oxygen species at breast tumor microenvironment, (3) enhances anaerobic metabolism, (4) inhibits the tricarboxylic cycle, (5) promotes PD-L1 upregulation, (6) inhibits apoptosis, (7) increases glucose uptake, and more importantly (8) recruits and interconnects the plasma membrane, nucleus, endoplasmic reticulum, and mitochondria to hijack breast cancer cells and rescue these cells from chemotherapy. Therefore, Akt signalling is considered a cellular defence mechanism employed against chemotherapeutic effects. In addition, interfering roles of PI3K/Akt signalling on the current cytotoxic and molecularly targeted therapy as well as immunotherapy of breast cancer are discussed with a clinical approach. Although, alpelisib, a PIK3CA inhibitor, is the only PI3K/Akt pathway inhibitor approved for breast cancer, we also highlight well-evaluated inhibitors of PI3K/Akt signalling based on different subtypes of breast cancer, which are under clinical trials whether as monotherapy or in combination with other types of chemotherapy.     

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。     

ICAM-3-induced cancer cell proliferation through the PI3K/Akt pathway

ICAM-3 interacts with LFA1, and is involved in the intercellular adhesion of leukocytes as well as in the mainenance of cell survival. It has also been suggested to induce cancer cell proliferation but the precise signaling pathway is unclear. The aim of this study was to determine the ICAM-3-activated downstream pathway in H1299 lung cancer cells. The level of ICAM-3-induced cell growth was examined using BrdU incorporation, which is a colony-forming assay, FACS analysis, and cell counting. The results showed that ICAM-3 expression induces cancer cell proliferation. In addition, FAK, Akt, PDK1, GSK-3beta, BAD, and PTEN were phosphorylated by ICAM-3-overexpression, resulting in enhanced cell proliferation. In conclusion, ICAM-3 expression induces cancer cell proliferation, and an increase in ICAM-3 expression can contribute to cancer progression.     

JAK/STAT, Raf/MEK/ERK, PI3K/Akt and BCR-ABL in cell cycle progression and leukemogenesis.

The roles of the JAK/STAT, Raf/MEK/ERK and PI3K/Akt signal transduction pathways and the BCR-ABL oncoprotein in leukemogenesis and their importance in the regulation of cell cycle progression and apoptosis are discussed in this review. These pathways have evolved regulatory proteins, which serve to limit their proliferative and antiapoptotic effects. Small molecular weight cell membrane-permeable drugs that target these pathways have been developed for leukemia therapy. One such example is imatinib mesylate, which targets the BCR-ABL kinase as well as a few structurally related kinases. This drug has proven to be effective in the treatment of CML patients. However, leukemic cells have evolved mechanisms to become resistant to this drug. A means to combat drug resistance is to target other prominent signaling components involved in the pathway or to inhibit BCR-ABL by other mechanisms. Treatment of imatinib-resistant leukemia cells with drugs that target Ras (farnysyl transferase inhibitors) or with the protein destabilizer geldanamycin has proven to be a means to inhibit the growth of resistant cells. This review will tie together three important signal transduction pathways involved in the regulation of hematopoietic cell growth and indicate how their expression is dysregulated by the BCR-ABL oncoprotein.     

CUEDC2通过活化 PI3K／Akt 信号通路促进乳腺癌细胞的生长

目的：探讨 CUE 结构域2（CUE domain －containing 2,CUEDC2）蛋白在人乳腺癌细胞中的生物学作用。方法：人乳腺肿瘤细胞 MCF －7转染的 Myc －CUEDC2真核表达载体,提取转染细胞的总蛋白检测磷酸化 Akt 和总 Akt 的表达变化。利用 CCK －8检测过表达 CUEDC2后 MCF －7细胞的生长。结果：CUEDC2能够活化 Akt,使磷酸化 Akt 表达增加,能够促进人乳腺癌细胞生长。结论：当乳腺癌中 CUEDC2表达增高时,能够引起 PI3K／Akt 信号通路活化,促进肿瘤细胞生长。     

PI3K/Akt and apoptosis: size matters

Recent research has examined Akt and Akt-related serine-threonine kinases in signaling cascades that regulate cell survival and are important in the pathogenesis of degenerative diseases and in cancer. We seek to recapitulate the research that has helped to define the current understanding of the role of the Akt pathway under normal and pathologic conditions, also in view of genetic models of Akt function. In particular, we will evaluate the mechanisms of Akt regulation and the role of Akt substrates in Akt-dependent biologic responses in the decisions of cell death and cell survival. Here, we hope to establish the mechanisms of apoptosis suppression by Akt kinase as a framework for a more general understanding of growth factor-dependent regulation of cell survival.     

硼替佐米对胰腺癌细胞增殖、凋亡及PI3K/Akt通路的影响

目的:探讨硼替佐米（BTZ）对胰腺癌细胞增殖、凋亡及PI3K/Akt通路的影响。方法:体外培养人胰腺癌细胞株PANC-1细胞,分别给予硼替佐米（0,2,10,50,250 nmol/L）作用24 h,采用MTT法检测PANC-1细胞活力,采用Annexin V/PI双染法检测细胞凋亡情况,采用流式细胞术检测细胞周期,采用Western blot检测细胞凋亡及PI3K/Akt通路相关蛋白表达情况。结果:与0 nmol/L硼替佐米相比,不同浓度硼替佐米处理后,PANC-1细胞生长抑制率均显著升高（P＜0.05）,G0/G1期细胞比例均显著升高（P＜0.05）,细胞凋亡率显著升高（P＜0.05）,细胞中cleaved-caspase-3、Bax蛋白表达增高（P＜0.05）,Bcl-2、PI3K、p-Akt蛋白表达降低（P＜0.05）,且呈剂量依赖性;裸鼠成瘤实验中,不同浓度硼替佐米作用后,肿瘤瘤体质量显著降低（P＜0.05）,且呈剂量依赖性。结论:硼替佐米能抑制胰腺癌细胞PANC-1增殖,诱导其凋亡,推测硼替佐米可能通过调节PI3K/Akt通路,激活凋亡蛋白基因表达,抑制抗凋亡蛋白基因的表达,诱导PANC-1细胞凋亡。     

ＰＩ３Ｋ／Ａｋｔ信号传导通路及其在结直肠癌中的研究进展

结直肠癌是常见的恶性肿瘤之一,近十年来,结直肠癌在我国的发病率呈逐年上升的趋势。已有研究表明,ＰＩ３Ｋ／Ａｋｔ信号传导通路是与细胞增殖和细胞凋亡关系最密切的信号传导通路之一。随着ＰＩ３Ｋ／ＡＫｔ信号通路在结直肠癌发生、发展中的研究不断深入,该通路对结直肠癌发生、发展及治疗药物的研发具有十分重要的价值。本文就ＰＩ３Ｋ／Ａｋｔ信号传导通路在结直肠癌发生、发展和治疗中的作用以及机制的研究进展作一综述。     

醉茄素A对非小细胞肺癌A549细胞增殖、凋亡及PI3K／Akt信号通路的影响

目的 探讨醉茄素A（WFA） 对非小细胞肺癌（NSCLC）A549细胞增殖、凋亡及PI3K／Akt信号通路的影响。方法 采用0、2.5、5.0、10.0、20.0μmol／L WFA 处理A549细胞,采用四甲基偶氮唑盐（MTT）比色法检测上述浓度处理24、48、72和96h的细胞增殖抑制率,Hoechst染色和磷酯酰丝氨酸结合蛋白 异硫氢酸荧光素／碘化丙啶双染法（Annexin V-FITC／PI）检测各浓度组48h的细胞凋亡情况,流式细胞仪检测各浓度组48h的细胞周期分布情况,免疫印迹检测各浓度组48h凋亡相关基因（Bcl-2、Bax和Cleaved caspase-3）和PI3K／Akt信号通路重要蛋白Akt及其磷酸化形式p-Akt的蛋白水平。结果 WFA 可抑制细胞增殖,并呈剂量和时间依赖性（P＜0.05）;0、2.5、5.0、10.0、20.0μmol／L WFA作用48h后A549细胞的凋亡指数分别为2.75±0.64、4.61±1.36、9.75±2.78、12.92±3.42和18.68±4.31,组间差异有统计学意义（P＜0.05）。除2.5μmol／L外,其余浓度组的早、晚期凋亡率、凋亡促进基因（Bax和Cleaved caspase-3）水平及G0／G1期细胞比例均高于0μmol／L,凋亡抑制基因Bcl-2水平及S期和G2／M期细胞比例均低于0μmol／L（P＜0.05）; 2.5、5.0、10.0、20.0μmol／L的组间差异有统计学意义（P＜0.05）。随着浓度升高,p-Akt／Akt值呈降低趋势,差异有统计学意义（P＜0.05）。结论 WFA能够抑制A549细胞的增殖及凋亡,可能通过抑制PI3K／Akt通路激活实现。     

PI3K/Akt通路与肿瘤治疗

磷酸肌醇3激酶/蛋白激酶B (phosphoinositide 3kinase /protein kinase B,PI3K/Akt)信号通路参与很多重要生物学过程的调控，但其过度激活可导致肿瘤的发生。在正常组织中PI3K/Akt信号转导途径处于活化状态，但是该通路如果被过度激活则可通过下调肿瘤抑制蛋白p53、刺激蛋     

PDK／Akt通路与肿瘤治疗

磷酸肌醇-3激酶／蛋白激酶B（phosphoinositide 3-kinase／protein kinaseB，P13K／Akt）信号通路参与很多重要生物学过程的调控，但其过度激活可导致肿瘤的发生。在正常组织中P13K／Akt信号转导途径处于活化状态，但是该通路如果被过度激活则可通过下调肿瘤抑制蛋白p53、刺激蛋白质合成、抑制细胞凋亡等导致肿瘤细胞的无限增殖，成为肿瘤预后不好的标志，因此抑制该通路的激活有利于肿瘤治疗。目前已发现肿瘤抑制基因PTEN、PHLPP和蛋白磷酸酶2A等均可通过不同的机制抑制该通路的激活。同时，针对该通路的抑制剂作为抗肿瘤药物得到了广泛研究并在临床上取得了预期的进展，如wtPTEN的转基因研究、P13K抑制剂LY294002和渥曼青霉素、PDK-1抑制剂星孢菌素和塞来昔布、Akt抑制剂哌立福新、雷帕霉素靶蛋白（mTOR）抑制剂西罗莫司等，期望这些抑制剂能达到靶向治疗肿瘤的目的。     

芹菜素通过 PI3K/Akt 信号通路诱导 Hela 细胞凋亡

目的：初探芹菜素（Apigenin）对人宫颈癌细胞 Hela 的抑制机制。方法：MTT 法检测 Apigenin 对 Hela细胞的增殖抑制作用,实时无标记细胞分析技术测量 Apigenin 对 Hela 细胞生长曲线的影响。Western blot 检测 Apigenin 对 Hela 细胞中 PI3K/ Akt 信号通路的影响。结果：与阴性对照组相比,Apigenin 能显著抑制 Hela细胞的增殖（P <0.01）,当药物浓度为20μmol/ L 时抑制率达到（80.5±5.3）%,IC50值为（6.8±0.8）μmol/ L。细胞生长曲线反映,Apigenin 减缓了 Hela 细胞的增殖,对数期细胞经20μmol/ L Apigenin 处理后,细胞数量迅速下降。Western blot 结果显示,Apigenin 能显著抵抗 IGF -1引起的 Akt 激活但并不能降低 PI3K 的磷酸化水平。同时 Apigenin 还能降低 Bcl -2/ Bax 比例,提高 Caspase -3活性,启动细胞线粒体凋亡。结论：Apigenin可以通过 PI3K/ Akt 信号通路促进 Hela 细胞的凋亡。     

红花多糖抑制PI3K/Akt信号通路诱导人胃癌细胞凋亡的研究

目的 探讨红花多糖通过抑制PI3K/Akt信号通路调控胃癌细胞凋亡的机制。方法 MTT比色法观察SPS对人胃癌SGC-7901细胞体外增殖的抑制作用,流式细胞仪(FCM)分析细胞凋亡,实时荧光定量RT-PCR法和Western Blot法检测蛋白激酶B(Akt)基因及蛋白的表达情况。结果 红花多糖在一定范围内以剂量依赖方式和时间依赖方式抑制SGC-7901胃癌细胞生长。流式细胞仪检测,SGC-7901细胞经红花多糖处理24 h,其早期凋亡率、细胞坏死或晚期凋亡率显著增加,呈现明显的剂量依赖性。Real-time PCR和Western Blot检测发现,SPS处理的细胞Akt基因及蛋白表达量明显下降。结论 红花多糖对人胃癌SGC-7901细胞体外增殖具有明显的抑制作用,该抑制作用具有一定的时间依赖性和剂量依赖性;红花多糖能够下调Akt mRNA表达,降低Akt和p-Akt蛋白的表达量,抑制Akt通路发挥抗肿瘤作用。     

Effects of AFP-activated PI3K/Akt signaling pathway on cell proliferation of liver cancer

This study aims to investigate effects of alpha-fetoprotein (AFP)-activated phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway on hepatocellular carcinoma cell proliferation. Active cirrhosis patients after hepatitis B infection (n?=?20) and viral hepatitis patients with hepatocellular carcinoma (HCC) (n?=?20) were selected as the subjects of the present study. Another 20 healthy subjects were selected as the control group. The serum AFP expression and liver tissue PI3K and Akt gene mRNA expression were detected. The hepatoma cell model HepG2 which had a stable expression of AFP gene was used. Real-time quantitative PCR and Western blot and other methods were used to analyze the intracellular PI3K and Akt protein levels. Compared with control group and cirrhosis group, the serum AFP levels in HCC group significantly increased, and the tissue PI3K and Akt mRNA expression also significantly increased. HepG2 cells were intervened using AFP, in which the PIK and Akt protein expression significantly increased. After intervention by use of AFP monoclonal antibodies or LY294002 inhibitor, the PIK and Akt protein expression in HepG2 cell was significantly decreased (P?<?0.05). AFP can promote the proliferation of hepatoma cells via activation of PI3K/Akt signaling pathway.     

Drug discovery approaches targeting the PI3K/Akt pathway in cancer

The abnormal activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway has been validated by epidemiological and experimental studies as an essential step toward the initiation and maintenance of human tumors. Notable in this regard are the prevalent somatic genetic alterations leading to the inactivation of the tumor suppressor gene PTEN and gain-of-function mutations targeting PIK3CA--the gene encoding the catalytic phosphosinositide-3 kinase subunit p110 alpha. A number of the intracellular components of this pathway have been targeted as anticancer drug discovery activities leading to the current panoply of clinical trials of inhibitors of PI3K, Akt and HSP90 in man. This review summarizes current preclinical knowledge of modulators of the PI3K/Akt pathway in which drug discovery and development activities have been advanced focusing on both the relevant clinical stage inhibitors and other disclosed tool compounds targeting PI3K, PDK1, Akt and HSP90.     

磷脂酰肌醇3激酶-蛋白质丝氨酸苏氨酸激酶途径与肿瘤的关系

磷脂酰肌醇3激酶（PI3K）-蛋白质丝氨酸苏氨酸激酶（Akt）途径是细胞内重要的信号传导途径,在细胞增殖分化中起重要作用。PI3K-Akt途径的失调控对于多种肿瘤的发生是一种刺激信号,途径中任何激酶表达的异常都可能诱导肿瘤的发生。现综述PI3K-Akt途径中PI3K、Akt、磷脂酰肌醇依赖性蛋白激酶（PDK）、与张力蛋白同源的第10号染色体上丢失的磷酸酶基因（PTEN）在肿瘤发生发展中的作用。     

Melittin对非小细胞肺癌增殖、凋亡及PI3K／Akt信号通路的影响

目的 探讨Melittin对非小细胞肺癌（NSCLC）细胞增殖、凋亡及PI3K／Akt信号通路的影响。方法 分别采用0、10、20、50、100 μmol／L Melittin处理NSCLC细胞株A549、SPC-A1及人肺上皮细胞株16HBE 24、48、72和96 h后,采用四甲基偶氮唑盐（MTT）比色法检测各细胞株的增殖抑制率变化,同时采用流式细胞术Annexin-FITC／PI双染法及PI单染法检测不同浓度Melittin 处理24、48 h后的A549细胞凋亡及细胞周期情况,Western blotting检测不同浓度Melittin处理48 h后的A549细胞中PI3K／Akt信号通路相关蛋白（Akt和PTEN）及凋亡促进基因（caspase-9）的表达情况。结果 在10～100 μmol／L范围内,Melittin可呈剂量和时间依赖的方式提高A549、SPC-A1细胞的增殖抑制率,差异均有统计学意义（P＜0.05）,但对16HBE无细胞毒性作用（P＞0.05）;与0 μmol／L比较,除10 μmol／L Melittin处理24 h后的晚期凋亡率和G2／M期细胞比例无统计学差异（P＞0.05）,10～100 μmol／L的早、晚期凋亡率、G0／G1期细胞比例及PTEN和caspase-9蛋白水平均升高,S期、G2／M期细胞比例及Akt水平均降低,以上差异有统计学意义（P＜0.05）,且10～100 μmol／L范围内各浓度间的差异均有统计学意义（P＜0.05）。结论 Melittin可对NSCLC细胞有毒性作用,但对正常肺上皮细胞无影响,且可诱导A549细胞凋亡及细胞周期阻滞并抑制PI3K／Akt信号通路的激活。