Targeting the phosphatidylinositol-3 kinase/Akt pathway for the treatment of cancer

Phosphatidylinositol-3 kinase (PI3K)/Akt is overactivated in a wide range of tumor types, and this triggers a cascade of responses, from cell growth and proliferation to survival, motility, epithelial-mesenchymal transition and angiogenesis. Therefore, this pathway presents an exciting target for molecular therapeutics. In addition, ectopic expression of PI3K or Akt, especially constitutively activated PI3K (p110alpha) or Akt, is sufficient to induce the oncogenic transformation of cells and tumor formation in transgenic mice, as well as the development of chemoresistance. Inhibition of PI3K/Akt signaling induces apoptosis and inhibits the growth of tumor cells that have elevated Akt levels. The dependence of certain tumors on PI3K/Akt signaling for survival and growth has wide implications for cancer therapy, offering the potential for preferential tumor cell killing. In the past few years, a number of inhibitors of the Akt pathway have been identified by combinatorial chemistry, high-throughput and virtual screening, or traditional medicinal chemistry. This review focuses on ongoing translational efforts to therapeutically target the PI3K/Akt pathway.     

紫草素通过PI3K/Akt通路促进人乳腺癌MCF-7细胞自噬

目的研究紫草素(Shikonin)对人乳腺癌MCF-7细胞自噬的影响及其作用机制。方法 CCK-8法检测紫草素处理人乳腺癌MCF-7细胞24、48 h细胞的存活率,Western blot方法检测紫草素处理24 h和48 h时LC3、p62、PI3K、Akt、p-PI3K、p-Akt蛋白水平。结果 1μmol.L-1紫草素处理细胞48 h以及2.5、5μmol.L-1紫草素处理MCF-7细胞24 h和48 h时,MCF-7细胞的活力受到明显抑制,LC3-Ⅱ/LC3-Ⅰ值增加,p62表达减少,总PI3K、Akt、p-PI3K、p-Akt均减少。结论紫草素促进乳腺癌MCF-7细胞自噬,其作用机制可能与PI3K/Akt通路受到抑制有关。     

Multiple defects in negative regulation of the PKB/Akt pathway sensitise human cancer cells to the antiproliferative effect of non-steroidal anti-inflammatory drugs

Antitumorigenic effects of non-steroidal anti-inflammatory drugs (NSAIDs) are well established in several types of cancer disease. However, the mechanisms driving these processes are not understood in all details. In our study, we observed significant differences in sensitivity of cancer epithelial cell lines to COX-independent antiproliferative effects of NSAIDs. The prostate cancer cell line LNCaP, lacking both critical enzymes in the negative control of PKB/Akt activation, PTEN and SHIP2, was the most sensitive to these effects, as assessed by analysing the cell cycle profile and expression of cell cycle regulating proteins. We found that p53 protein and its signalling pathway is not involved in early antiproliferative action of the selected NSAID—indomethacin. RNAi provided evidence for the involvement of p21^Cip1/Waf1, but not GDF-15, in antiproliferative effects of indomethacin in LNCaP cells. Interestingly, we also found that indomethacin activated PKB/Akt and induced nuclear localisation of p21^Cip1/Waf1 and Akt2 isoform. Our results are in agreement with other studies and suggest that maintaining of the p21^Cip1/Waf1 level and its intracellular localisation might be influenced by Akt2. Knock-down of SHIP2 by RNAi in PTEN negative prostate and colon cancer cell lines resulted in higher sensitivity to antiproliferative effects of indomethacin. Our data suggest novel mechanisms of NSAIDs antiproliferative action in cancer epithelial cells, which depends on the status of negative regulation of the PKB/Akt pathway and the isoform-specific action of Akt2. Thus, unexpectedly, multiple defects in negative regulation of the PKB/Akt pathway may contribute to increased sensitivity to chemopreventive effects of these widely used drugs.     

虎杖苷通过蛋白激酶 B信号通路影响胃癌细胞增殖凋亡

目的 研究虎杖苷对胃癌细胞SGC-7901增殖和凋亡的影响和机制.方法 虎杖苷处理胃癌细胞SGC-7901,MTT法检测增殖,平板克隆实验检测克隆形成能力,碘化丙啶(PI)单染法检测细胞周期分布,膜联蛋白V-异硫氰酸荧光素/碘化丙啶(Annexin V-FITC/PI)双染法检测细胞凋亡,蛋白质印迹法(Western blotting)检测细胞周期蛋白D1(cyclin D1)、周期蛋白依赖性激酶4(CDK4)、Bcl-2相关X(Bax)、剪切型胱天蛋白酶-3(Cleaved-caspase-3)、磷酸化-蛋白激酶B(p-Akt)蛋白表达.用蛋白激酶B(Akt)信号激活剂和虎杖苷联合处理胃癌细胞SGC-7901,检测细胞增殖、克隆、周期、凋亡变化.结果 虎杖苷处理以后的胃癌细胞SGC-7901增殖能力下降[(0.58±0.06)比(0.20±0.01)],细胞克隆形成数目减少[(118.54±10.65)个比(69.52±7.91)个],细胞凋亡增多[(2.97±0.32)％比(17.45±1.69)％],细胞G0/G1比例升高[(50.47±3.25)％比(67.13±3.84)％],cyclin D1、CDK4蛋白表达减少,Bax、Cleaved-caspase-3蛋白表达水平升高,p-Akt蛋白水平降低[(0.51±0.05)比(0.24±0.03)].Akt信号激活剂处理可以逆转虎杖苷对胃癌细胞SGC-7901增殖、克隆抑制和周期阻滞、凋亡促进作用.结论 虎杖苷通过抑制Akt信号通路阻碍胃癌细胞增殖并诱导细胞凋亡.     

The miR-21/PTEN/Akt signaling pathway is involved in the anti-tumoral effects of zoledronic acid in human breast cancer cell lines

Preclinical data indicate a direct anti-tumor effect of zoledronic acid (ZA) outside the skeleton, but its molecular mechanism is still not completely clarified. The aim of this study was to investigate the anti-cancer effects of ZA in human breast cancer cell lines, suggesting that they may in part be mediated via the miR-21/PTEN/Akt signaling pathway. The effect of ZA on cell viability was measured by MTT assay, and cell death induction was analyzed using either a double AO/EtBr staining and M30 ELISA assay. A Proteome Profiler Human Apoptosis Array was executed to evaluate the molecular basis of ZA-induced apoptosis. Cell cycle analysis was executed by flow cytometry. The effect of ZA on miR-21 expression was quantified by qRT-PCR, and the amount of PTEN protein and its targets were analyzed by Western blot. ZA inhibited cell growth in a concentration- and time-dependent manner, through the activation of cell death pathways and arrest of cell cycle progression. ZA downregulated the expression of miR-21, resulting in dephosphorilation of Akt and Bad and in a significant increase of p21 and p27 proteins expression. These results were observed also in MDA-MB-231 cells, commonly used as an experimental model of bone metastasis of breast cancer. This study revealed, for the first time, an involvement of the miR-21/PTEN/Akt signaling pathway in the mechanism of ZA anti-cancer actions in breast cancer cells. We would like to underline that this pathway is present both in the hormone responsive BC cell line (MCF-7) as well as in a triple negative cell line (MDA-MB-231). Taken together these results reinforce the use of ZA in clinical practice, suggesting the role of miR-21 as a possible mediator of its therapeutic efficacy.     

SPNS2 promotes the malignancy of colorectal cancer cells via regulating Akt and ERK pathway

Colorectal cancer (CRC) is a prevalent malignant tumour that causes considerable cancer‐related deaths globally. The sphingolipid transporter 2 (SPNS2), a sphingosine‐1‐phosphate (S1P) transporter, modulates multiple biological events including malignancy of cancer cells. In this study, the effects of SPNS2 on CRC progression were studied. We found that SPNS2 expression was significantly upregulated in CRC tissues compared to that in adjacent non‐tumour tissues. To assess the role of SPNS2 in CRC cells, we performed loss‐ and gain‐of‐function experiments in SW480 and HCT116 cells, respectively. The results demonstrated that SPNS2 promoted proliferation, migration and invasion, and inhibited apoptosis in CRC cells. Additionally, SPNS2 enhanced the release of intracellular S1P, and increased S1P receptor 1 (S1PR1) and S1PR3 expression. Moreover, SPNS2 activated the Akt and ERK pathways, and the biological behaviours of SPNS2 were attenuated by Akt or ERK inhibitor in HCT116 cells. In conclusion, our results demonstrated that SPNS2 promoted proliferation, migration and invasion, and inhibited apoptosis by regulating S1P/S1PR1/3 axis and activating Akt and ERK pathway in CRC cells.     

Genistein induces activation of the mitochondrial apoptosis pathway by inhibiting phosphorylation of Akt in colorectal cancer cells

Context: Genistein inhibits the proliferation and induces apoptosis of colorectal cancer cells; however, the underling molecular mechanisms remain to be determined.

Aim: The aim of this study was to investigate whether genistein reduces cell viability by suppressing the phosphorylation of AKT and activating the mitochondrial apoptosis pathway in colorectal cancer cells.

Materials and methods: The anti-proliferative effects of genistein (0, 25, 50, and 100?μM) on HCT-116 and LoVo cells were assessed using MTT assay. Genistein-induced apoptosis was measured by Hoechst 33258 staining and flow cytometry. The mRNA level of Bax was detected by real-time PCR. The protein levels of Bax, total Akt, and phosphorylated Akt were assessed by western blot.

Results: The IC₅₀ values of genistein were 690, 135, and 61?μM in HCT-116 cells and 204, 135, and 93?μM in LoVo cells after treatment for 24, 48, and 72?h, respectively. After treatment with different concentrations of genistein (0, 25, 50, and 100?μM) for 48?h, the early apoptotic cells in HCT-116 increased from 1.99%?±?0.55% to 6.78%?±?2.12%, 23.16%?±?3.87%, and 36.99%?±?3.76%, respectively. The same concentrations of genistein increased the early apoptotic cells in LoVo from 2.56%?±?1.42% to 3.21%?±?1.52%, 18.22%?±?3.56%, and 23.56%?±?3.02%, respectively. Moreover, genistein increased the mRNA and protein levels of Bax, while it inhibited the phosphorylation of Akt in HCT-116 cells.

Conclusion: Genistein inhibited cell proliferation and induced apoptosis of colorectal cancer cells. Genistein induced the mitochondrial pathway of apoptosis in HCT-116 cells by inhibiting phosphorylation of Akt.     

Exenatide modulates metalloproteinase expression in human cardiac smooth muscle cells via the inhibition of Akt signaling pathway

Background

Incretin analogue drugs, a FDA-approved treatment in diabetes, has been tested for its therapeutic properties as modulators of atherosclerosis. We investigated the effects of incretin drugs on the modulation of gene expression and protein levels of matrix metalloproteinases (MMPs) as well as their inhibitors ? tissue inhibitors of metalloproteinases (TIMPs) in coronary artery smooth muscle cells (hCASMC) in the context of atherosclerotic plaque formation and inflammation.

Rho-kinase inhibitor upregulates migration by altering focal adhesion formation via the Akt pathway in colon cancer cells

Although Rho-kinase is reportedly implicated in carcinogenesis and the progression of human cancers, its precise mechanism has not been fully elucidated. We recently reported that Rho-kinase negatively regulates epidermal growth factor (EGF)-stimulated cancer progression in SW480 colon cancer cells. In the present study, we investigated the effect of Rho-kinase on the migration of SW480 colon cancer cells and the mechanism underlying the involvement of Rho-kinase. Interestingly, (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide, 2HCl (Y27632), a specific inhibitor of Rho-kinase, dose-dependently enhanced cell migration. SW480 cells spontaneously release vascular endothelial growth factor (VEGF), however, Y27632 had little effect on its release. While Rho-kinase, which is generally phosphorylated in unstimulated cells, was clearly suppressed by Y27632, exogenous VEGF did not affect its phosphorylation. Immunofluorescence microscopy revealed that Y27632 caused a dramatic change in the localization of focal adhesion components, vinculin, phosphorylated caveolin-1 and tyrosine-phosphorylated proteins in SW480 cells. Furthermore, Akt inhibitor restored the loss of vinculin-stained focal adhesion formation induced by Y27632. We also observed similar effects for Y27632 on the migration and localization of focal adhesion components such as vinculin in another colon cancer cell line, HT29. Taken together, these results strongly suggest that Rho-kinase negatively regulates the migration of colon cancer cells by altering focal adhesion formation via the Akt pathway.     

Autophagy plays a protective role against apoptosis induced by toxicarioside N via the Akt/mTOR pathway in human gastric cancer SGC-7901 cells

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.     

Carnosic acid induces autophagic cell death through inhibition of the Akt/mTOR pathway in human hepatoma cells

The therapeutic goal of cancer treatment is now geared towards triggering tumour‐selective cell death with autophagic cell death being required for the chemotherapy of apoptosis‐resistant cancer. In this study, Carnosic acid (CA), a polyphenolic diterpene isolated from Rosemary (Rosemarinus officinalis), significantly induced autophagic cell death in HepG2 cells. Ca treatment caused the formation of autophagic vacuoles produced an increasing ratio of LC3‐II to LC3‐I in a time‐ and dose‐dependent manner but had no effect on the levels of autophagy‐related protein ATG6 and ATG13 expression. Autophagy inhibitors, 3‐methyladenine (3‐MA), chloroquine and bafilomycin A1, or ATG genes silencing in HepG2 cells significantly inhibited CA‐induced autophagic cell death. The CA treatment decreased the levels of phosphorylated Akt and mTOR without any effects on PI3K or PTEN. Most importantly, overexpression of Akt and knockdown of PTEN attenuated autophagy induction in CA‐treated cells. Taken together, our results indicated that CA induced autophagic cell death through inhibition of the Akt/mTOR pathway in human hepatoma cells. These findings suggest that CA has a great potential for the treatment of hepatoma via autophagic induction. Copyright © 2014 John Wiley & Sons, Ltd.     

PI3K/Akt信号转导通路在非小细胞肺癌中的作用

肺癌是当今世界严重威胁人类健康和生命的疾病,其中85%是非小细胞肺癌(NSCLC)。PI3K/Akt通路在NSCLC的发生、发展中具有重要的作用,可以调控细胞存活、增殖、抗凋亡、血管生成等影响肿瘤的发生发展,而且某些蛋白的表达还是NSCLC不良预后的标志。在此我们对PI3K/Akt通路在NSCLC中的分子机制进行总结,并进一步讨论NSCLC的多靶点治疗。     

PI3K/Akt/mTOR pathway as a target for cancer therapy

The PI3K/Akt/mTOR pathway regulates several normal cellular functions that are also critical for tumorigenesis, including cellular proliferation, growth, survival and mobility. Components of this pathway are frequently abnormal in a variety of tumors, making them an attractive target for anti-cancer therapy. Inhibition of mTOR in patients with cancer became more feasible after the development of rapamycin analogs with improved pharmacologic properties. The promising activity of these agents in early clinical trials has led to the development of ongoing phase III trials in renal cell carcinoma and breast cancer. Future studies are needed to identify the patients most likely to benefit from this form of therapy, and to define its role in combination with chemotherapy, hormones and growth factor inhibitors.     

蒲公英根水提物通过磷脂酰肌醇-3-激酶-蛋白激酶B途径调控人舌癌细胞Tca-8113凋亡 迁移

目的制备蒲公英根水提物,研究其对人舌癌细胞Tca-8113凋亡、迁移的影响。方法水溶法制备蒲公英根水提物,并按一定浓度加至正常培养的人舌癌细胞Tca-8113中。流式细胞术用于分析蒲公英根水提物对Tca-8113细胞凋亡的作用,Transwell实验检测其对癌细胞迁移的影响,蛋白质印迹法检测各组癌细胞中磷脂酰肌醇-3-激酶-蛋白激酶B(PI3K/Akt)途径中关键分子p-Akt、Bcl-2等蛋白的表达差异。结果 10 g/L,20 g/L的蒲公英根水提物明显抑制癌细胞的增殖,进一步证实蒲公英根水提物可诱导Tca-8113细胞凋亡;蒲公英根水提物降低p-Akt、Bcl-2的蛋白表达并呈浓度依赖性。结论蒲公英根水提物通过降低p-Akt、Bcl-2表达促进人舌癌细胞Tca-8113细胞凋亡,并降低其迁移能力。     

Targeting Akt in cancer therapy

In an effort to improve therapeutic options in cancer, many investigational drugs are being developed to inhibit signaling pathways that promote the survival of cancer cells. The prototypic pathway that promotes cellular survival is the phosphoinositide 3'-kinase/Akt/mammalian target of rapamycin pathway, which is constitutively activated in many types of cancers. Mechanisms for activation of the serine/threonine kinase, Akt, include loss of tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) function, amplification or mutation of phosphoinositide 3'-kinase, amplification of Akt, activation of growth factor receptors and exposure to carcinogens. Activation of Akt promotes cellular survival as well as resistance to treatment with chemotherapy and/or radiation therapy. Immunohistochemical analyses have shown that Akt is activated in many types of cancers and preneoplastic lesions, and Akt activation is a poor prognostic factor in various cancers. Taken together, these data demonstrate that Akt is a valid target for inhibition. This review will focus on published data using different approaches to inhibit Akt. We will also consider how the complex regulation of the phosphoinositide 3'-kinase/Akt/mammalian target of rapamycin pathway poses practical issues concerning the design of clinical trials, potential toxicities and the likelihood of finding a therapeutic index when targeting such a critical cellular pathway.     

木犀草素逆转宫颈癌细胞对阿霉素耐药性的机制研究

目的 探讨木犀草素（Lut）逆转宫颈癌对阿霉素（Dox）耐药性的效应及其机制。方法 建立Dox耐药的宫颈癌HeLa/Dox细胞株,利用Dox、Lut单独或联合作用于细胞,分为control组、Dox组、Lut组、Dox＋Lut组,检测各组细胞存活率及凋亡率。构建小鼠移植瘤模型,经腹腔注射3 mg·kg^-1 Dox和/或5 mg·kg^-1 Lut,检测小鼠肿瘤生长情况及肿瘤中相关蛋白的表达。结果 （1） CCK-8检测结果显示,Dox+Lut组细胞的生长活性明显受到抑制,存活率显著低于Dox组和Lut组（P<0.01）。细胞克隆形成实验显示出与CCK-8实验相似的细胞生长趋势。流式细胞术检测结果显示,Dox单药对HeLa/Dox细胞的凋亡无明显促进作用,而Lut单药可显著诱导HeLa/Dox细胞凋亡。（2） Dox单药对HeLa/Dox细胞迁移的影响较小（P<0.05）,而Lut单药处理的HeLa/Dox细胞迁移数目明显减少,Dox与Lut联合应用对HeLa/Dox细胞迁移能力的抑制作用最强（P<0.01）。（3）与对照组相比,Dox组、Lut组、Dox+Lut组HeLa/Dox细胞中PI3K、Cleaved caspase-3蛋白表达均显著上调,p-Akt、p-mTOR、p70S6K蛋白表达显著下调（P<0.05）,且Dox+Lut组蛋白表达水平变化最为显著。（4）对照组、Dox组、Lut组、Dox+Lut组小鼠肿瘤体积分别为（1265.8±123.3）mm³、（456.4±68.7）mm³、（479.9±57.2）mm³、（108.1±14.0）mm³,差异具有统计学意义（P＜0.05）。联合应用Dox和Lut后,肿瘤组织中PI3K和Cleaved caspase-3的表达显著上调（P<0.01）,而p70S6K和Ki-67的表达显著下调（P<0.01）。结论 Lut可通过调节PI3K/Akt信号通路的活性逆转宫颈癌细胞对阿霉素的耐药性,从而抑制肿瘤细胞的增殖和转移,并促进其凋亡。     

Inhibitors beta-amyloid-induced toxicity by modulating the Akt signaling pathway

The Akt signaling pathway plays a crucial role in neuronal survival, leading to inhibition of apoptosis. Many stimulants including neurotrophins are reported to activate this pathway in preclinical studies; however, there are no drugs for neurodegenerative diseases adopting such a concept on the market so far. Among neurodegenerative diseases, Alzheimer's disease is the most common and characterized by senile plaques and neurofibrillary tangles, which consist of beta-amyloid and hyperphosphorylated tau, respectively. Recent studies suggest that activation of Akt inhibits toxicity of beta-amyloid and formation of neurofibrillary tangles, leading to protection of neurons against apoptosis. This review discusses the possibility of treatment of Alzheimer's disease by activating the Akt signaling pathway.     

蓝萼乙素通过Akt/BAD通路对宫颈癌裸鼠移植瘤生长的影响

目的 探究蓝萼乙素通过蛋白激酶B（Akt）/B细胞淋巴瘤-2（Bcl-2）相关死亡启动因子（BAD）通路对宫颈癌裸鼠移植瘤生长的影响和机制。方法 将48只SPF级雌性Balb/c-nu裸鼠随机分为模型、蓝萼乙素（56、112 mg/kg）和蓝萼乙素＋SC79（112 mg/kg＋10 mg/kg）组,每组12只。将HeLa细胞种植在裸鼠右大腿根部背侧皮下,建立皮下移植瘤模型,观察肿瘤体积、质量和一般情况的变化。苏木精–伊红（HE）染色观察肿瘤组织的组织学变化。TUNEL实验检测肿瘤组织细胞凋亡情况。Western blotting法检测移植瘤组织中p-Akt、Akt、p-BAD、BAD、磷酸酯酶与张力蛋白同源物（PTEN）蛋白表达水平。结果 与模型组相比,蓝萼乙素组第22、25、28天裸鼠肿瘤体积、肿瘤质量、肿瘤组织Akt、BAD磷酸化水平显著降低（P＜0.05）,肿瘤细胞凋亡率、肿瘤组织PTEN蛋白水平显著升高（P＜0.05）;SC79可减弱蓝萼乙素对宫颈癌裸鼠移植瘤生长的抑制作用。结论 蓝萼乙素对宫颈癌裸鼠移植瘤生长起到抑制作用,其作用机制与抑制Akt/BAD信号通路有关。