Cytotoxic effects of 15d-PGJ2 against osteosarcoma through ROS-mediated AKT and cell cycle inhibition

Polo-like kinase 1 (PLK1), a critical cell cycle regulator, has been identified as a potential target in osteosarcoma (OS). 15-deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2), a prostaglandin derivative, has shown its anti-tumor activity by inducing apoptosis through reactive oxygen species (ROS)-mediated inactivation of v-akt, a murine thymoma viral oncogene homolog, (AKT) in cancer cells. In the study analyzing its effects on arthritis, 15d-PGJ2 mediated shear-induced chondrocyte apoptosis via protein kinase A (PKA)-dependent regulation of PLK1. In this study, the cytotoxic effect and mechanism underlying 15d-PGJ2 effects against OS were explored using OS cell lines. 15d-PGJ2 induced significant G2/M arrest, and exerted time- and dose-dependent cytotoxic effects against all OS cell lines. Western blot analysis showed that both AKT and PKA-PLK1 were down-regulated in OS cell lines after treatment with 15d-PGJ2. In addition, transfection of constitutively active AKT or PLK1 partially rescued cells from 15d-PGJ2-induced apoptosis, suggesting crucial roles for both pathways in the anti-cancer effects of 15d-PGJ2. Moreover, ROS generation was found treatment with 15d-PGJ2, and its cytotoxic effect could be reversed with N-acetyl-l-cysteine. Furthermore, inhibition of JNK partially rescued 15d-PGJ2 cytotoxicity. Thus, ROS-mediated JNK activation may contribute to apoptosis through down-regulation of the p-Akt and PKA-PLK1 pathways. 15d-PGJ2 is a potential therapeutic agent for OS, exerting cytotoxicity mediated through both AKT and PKA-PLK1 inhibition, and these results form the basis for further analysis of its role in animal studies and clinical applications.     

Dual inhibition of (V600E)BRAF and the PI3K/AKT/mTOR pathway cooperates to induce apoptosis in melanoma cells through a MEK-independent mechanism

BRAF is a main oncogene in human melanomas. Here, we show that BRAF depletion by siRNA or inhibition of its activity by treatment with RAF inhibitor Sorafenib induces apoptosis in NPA melanoma cells expressing oncogenic ^V600EBRAF. This effect is mediated through a MEK/ERK-independent mechanism, since treatment with the MEK inhibitor U0126 does not exert any effect. Moreover, we demonstrate that inhibition of the PI3K/AKT/mTOR cascade alone does not increase apoptosis in these cells. However, the blockage of this pathway in cells lacking either BRAF expression or activity cooperates to induce higher levels of apoptosis than those achieved by inhibition of BRAF alone. Consistently, we demonstrate that abrogation of BRAF expression increases AKT and mTOR phosphorylation, suggesting the existence of a compensatory pro-survival mechanism after BRAF depletion. Together, our data provide a rationale for dual targeting of BRAF and PI3K/AKT/mTOR signalling to effectively control melanoma disease.     

ABT-737对顺铂诱导乳腺癌T47D细胞凋亡的增敏作用

目的 探讨Bcl-2抑制剂ABT-737联合顺铂对乳腺癌T47D细胞株凋亡的影响.方法 常规培养T47D细胞,采用四甲基偶氮唑蓝(MTT)法检测ABT-737联合顺铂对T47D细胞增殖的影响,采用Western blot法检测凋亡相关蛋白的表达,采用荧光染色法观察T47D细胞凋亡的形态学变化,采用流式细胞仪检测T47D细胞的凋亡率.结果 MTT法检测结果显示,ABT-737可明显降低顺铂在T47D细胞中的IC50[由顺铂单药的(26.00±1.41) μmol/L降为联合用药的(13.00±1.11)μmol/L].ABT-737增加顺铂对T47D细胞的抑制作用,并呈剂量依赖性,而ABT-737单药对T47D细胞的抑制作用不明显.Western blot检测多聚ADP核糖聚合酶(PARP)的剪切结果显示,ABT-737明显降低了顺铂诱导T47D细胞凋亡的浓度,加快了凋亡诱导时间,ABT-737对顺铂诱导T47D细胞凋亡的增敏作用呈剂量依赖性,单药对T47D细胞的作用不明显.与单药组相比,ABT-737与顺铂联合时T47D细胞中PARP和caspase3的剪切明显增加,而Bcl-2、Bcl-XL和Bax的表达无明显变化.荧光染色和流式细胞术检测结果均显示,ABT-737联合顺铂时,T47D细胞的凋亡率明显增加.结论 ABT-737可显著提高顺铂对乳腺癌T47D细胞的凋亡诱导作用.     

Blockade of VEGF-A suppresses tumor growth via inhibition of autocrine signaling through FAK and AKT

Blockade of VEGF signaling using RNA interferences, a neutralizing antibody, an antagonizing soluble VEGF receptor, and a receptor tyrosine kinase inhibitor induced anti-tumor effects in human astrocytoma U251-MG and fibrosarcoma HT-1080 in vitro in a dose-dependent manner. Furthermore, blockade of VEGF-A using the doxycycline-inducible VEGF-A RNA interference system showed a significant anti-tumor effect in a murine HT-1080-xenograft model. Anti-tumor effect through the blockade of VEGF signaling was mediated by FAK and AKT pathway in vitro and in vivo. These results collectively indicate that VEGF-A and its receptors can act as key inducer of tumor growth as well as angiogenesis.     

TRPM7通过PI3K/AKT/ERK信号途径影响脑胶质瘤细胞增殖、上皮-间质转化

目的 探讨沉默M型顺时受体电位通道7(melastatin transient receptor potential channel 7,TRPM7)对脑胶质瘤细胞增殖、上皮-间质转化的影响及其作用机制.方法 采用qRT-PCR和Western blot检测TRPM7在人正常星形胶质HA1800细胞株以及脑胶质瘤细胞株...     

悬浮培养GLC-82肺肿瘤细胞积聚体与蛋白激酶FAK、AKT、ERK和SRC活化的关系

背景与目的:蛋白激酶FAK部分介导肿瘤细胞在悬浮培养下细胞积聚体的形成,从而阻止细胞发生凋亡和促进细胞增殖,但是参与细胞积聚体形成的FAK下游通路尚不清楚。本研究旨在研究蛋白激酶FAK及其可能的下游分子ERK、AKT和SRC活化在悬浮状态肺癌GLC-82细胞积聚中的作用。方法:用polyHEMA悬浮培养观察肺正常细胞HBE和肿瘤细胞GLC-82积聚体形态;细胞凋亡用DNA琼脂糖凝胶电泳检测梯状DNA分析;细胞转化能力用软琼脂糖集落形成实验分析;磷酸化蛋白激酶水平用免疫印迹实验检测;RNA干扰实验降低FAK蛋白水平的表达。结果:GLC-82肺腺癌细胞在polyHEMA悬浮状态下能够存活和形成积聚体,肺正常细胞HBE在polyHEMA悬浮状态下发生凋亡和不形成积聚体。磷酸化FAK、ERK、AKT和SRC的水平和GLC-82积聚体有关。沉默FAK蛋白的表达,能够部分地阻断肿瘤细胞积聚体的形成,降低磷酸化ERK和AKT水平,以及降低软琼脂集落形成能力。FAKRNA干扰前后的GLC-82细胞软琼脂集落形成率分别为(12.2±1.1)%和(3.6±0.7)%(P=0.001)。结论:GLC-82肺癌细胞积聚体的形成部分由FAK信号通路介导,ERK和AKT是FAK的下游通路蛋白。     

Simvastatin interacts synergistically with tipifarnib to induce apoptosis in leukemia cells through the disruption of RAS membrane localization and ERK pathway inhibition

Tipifarnib, a farnesyltransferase inhibitor (FTI), was initially designed to disrupt RAS farnesylation and membrane localization necessary for RAS function. However, alternative geranylgeranylation has been postulated as an escape mechanism by which RAS bypasses the effect of FTI treatment. In this study, we demonstrate that simvastatin, an HMG-CoA reductase inhibitor, augments the cytotoxic effect of tipifarnib by blocking the alternative geranylgeranylation of RAS. Notably, this effect was accompanied by disruption of RAS membrane localization and ERK downregulation. In addition, the apoptotic effect of this combination was associated with downregulation of the antiapoptotic Mcl-1 protein and activation of the caspase cascade. These findings demonstrate that combining tipifarnib and simvastatin was successful in targeting RAS/ERK signaling and inducing apoptosis in leukemia cells. Both simvastatin and tipifarnib were used at clinically achievable doses, which make the combination promising for future clinical studies.     

ERK和SAPK/JNK通路在神经酰胺致HT-29细胞凋亡中的作用

目的： 探讨ERK和SAPK/JNK信号途径在C2-神经酰胺诱导人结肠癌HT-29细胞凋亡中的作用。方法：分别用不同剂量C2-神经酰胺 (0、12.5、25.0和50.0 μmol/L)处理HT-29细胞24 h,分别采用AO/EB染色法观察HT-29细胞凋亡的形态学变化,计算细胞凋亡率;Western Blotting法检测ERK、p-ERK蛋白表达。再分别用不同剂量C2-神经酰胺 (0、12.5、25.0和50.0 μmol/L)处理HT-29细胞24 h,并选择50.0 μmol/L C2-神经酰胺作用3、6、12、24 h后,用SAPK/JNK检测试剂盒结合Western Blotting方法检测phospho-c-Jun蛋白的表达。结果：与溶剂对照组比较,随着C2-神经酰胺剂量的增加,各剂量组HT-29细胞的凋亡率增加 (P＜0.05),ERK总蛋白和p-ERK的表达呈现下降趋势,存在剂量-效应关系 (P＜0.05)。不同浓度和不同时间的C2-神经酰胺作用下,HT-29细胞中phospho-c-jun的表达无明显变化 (P＞0.05)。结论：C2-神经酰胺能够直接诱导人结肠癌HT-29细胞发生凋亡,在此过程中SAPK/JNK活性无显著变化,抑制ERK信号转导通路可能是其诱导凋亡的机制。     

MicroRNA-21 suppresses PTEN and hSulf-1 expression and promotes hepatocellular carcinoma progression through AKT/ERK pathways

MicroRNAs (miRNAs) have been believed to associate with malignant progression including cancer cell proliferation, apoptosis, differentiation, angiogenesis, invasion and metastasis. However, the functions of miRNAs are intricate, one miRNA can directly or indirectly target multiple genes and function as oncogene or tumor suppressor gene. In this study, we found that miR-21 inhibits PTEN and human sulfatase-1 (hSulf-1) expression in hepatocellular carcinoma (HCC) cells. The hSulf-1 is a heparin-degrading endosulfatase, which can inhibit the heparin binding growth factor-mediated signaling transduction into cells. Therefore, miR-21-mediated suppression of both hSulf-1 and PTEN led to activation of AKT/ERK pathways and epithelial–mesenchymal transition (EMT) in HCC cells, and finally enhance the activity of HCC cell proliferation and movement and promote HCC xenograft tumor growth in mouse models. These findings may provide candidate targets for prevention and treatment of HCC.     

The activation of ERK1/2 via a tyrosine kinase pathway attenuates trail-induced apoptosis in HeLa cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves as an extracellular signal that triggers apoptosis in tumor cells. To characterize the molecular events involved in TRAIL-induced apoptotic signaling, we investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) in HeLa cell death. Here we show that TRAIL-activated ERK1/2 through a tyrosine kinase-dependent pathway, subsequently elevated anti-apoptotic Bcl-2 protein levels. ERK1/2 inhibition with PD98059 promoted apoptotic cell death through the downregulation of ERK1/2 activity and Bcl-2 protein levels. Moreover, tyrosine kinase inhibition with Genistein in TRAIL-induced apoptosis effectively attenuated ERK1/2 activity and enhanced apoptotic cell death. Taken together, our results indicate that ERK1/2 activation via tyrosine kinase pathway plays a protective role as the cellular defense mechanism through the upregulation of Bcl-2 protein levels in TRAIL-induced apoptosis.     

MicroRNA-31 inhibits cisplatin-induced apoptosis in non-small cell lung cancer cells by regulating the drug transporter ABCB9

Alterations in microRNA (miRNA) expression have been found to be involved in tumor growth and response to chemotherapy. However, the possible role of miR-31 in cisplatin (DDP) resistance in non-small cell lung cancer (NSCLC) remains unclear. In this study, we identified a DDP-sensitive and a DDP-resistant cell line from four candidate human NSCLC cell lines. Notably, we found that miR-31 was significantly upregulated in the DDP-resistant cell line compared with its level in the DDP-sensitive cell line. As a result, miR-31 overexpression induced DDP resistance in the DDP-sensitive cell line, and miR-31 knockdown rescued DDP sensitivity in the DDP-resistant cell line. Interestingly, miR-31 was inversely correlated with the expression of the drug resistance gene ABCB9. The luciferase activity assay showed that miR-31 directly targets the 3′UTR of ABCB9, which is known to play a crucial role in drug resistance. Mechanistically, we showed that miR-31 confers DDP-induced apoptosis and that inhibition of ABCB9 is required for DDP resistance. The data demonstrate that miR-31 exerts an anti-apoptotic effect most likely through the inhibition of ABCB9 and thus provide a novel strategy involving the use of miR-31 as a potential target in NSCLC chemotherapy.     

PM2.5对HK-2细胞氧化损伤和凋亡的影响

目的：探讨深圳和太原市PM_2.5对人肾上皮细胞（HK-2）氧化损伤和凋亡的影响。方法：用中流量采样器分别采集太原某大学校园和深圳市疾病预防控制中心楼顶空气,将吸附有PM_2.5的滤膜洗脱后制备PM_2.5混悬液。设置阴性对照组、50 μg/mL深圳PM_2.5样品组、50 μg/mL太原PM_2.5样品组和10 μmol/L Cr⁶⁺阳性对照组,分别处理HK-2细胞24 h,测定4组细胞氧化损伤指标丙二醛（MDA）、超氧化物歧化酶（SOD）、还原型谷胱甘肽（GSH）、谷胱甘肽过氧化物酶（GSH-PX）的变化,并应用流式细胞术检测细胞凋亡水平。结果：与阴性对照组相比,深圳PM_2.5样品组、太原PM_2.5样品组和阳性对照组中MDA含量分别升高8.16%、34.51%和72.23%;SOD活性分别降低7.49%、19.67%和29.55%;GSH含量分别降低10.43%、16.39%和37.43%。太原PM_2.5样品组与阴性对照组的差异均有统计学意义（P < 0.05或P < 0.01）。GSH-PX活性分别降低42.70%、61.62%和60.98%,细胞凋亡率分别升高197.25%、301.22%和399.08%,上述3组与阴性对照组间的差异均有统计学意义（P < 0.05或P < 0.01）。结论：深圳和太原市PM_2.5均可引起HK-2细胞发生氧化损伤和细胞凋亡率增加,且太原市PM_2.5的作用更为明显。     

PTEN，P—AKT，P—ERK蛋白在胃癌组织中的表达及意义

目的：检测PTEN和P—AKT，P—ERK蛋白在胃癌中的表达，并探讨其相互关系。方法：应用免疫组织化学方法检测65例胃癌及癌旁组织中PTEN和P—AKT，P—ERK蛋白的表达情况。结果：PTEN蛋白在胃癌中表达的阳性率（58．46％）明显低于相应正常组织（100％）（P〈0．01），其表达水平与组织分化程度、浸润深度、淋巴结转移及TNM分期有关（P〈0．05）。P—AKT蛋白在胃癌中表达的阳性率（67．69％）明显高于相应正常组织（26．15％）（P〈0．01），其表达与淋巴结转移有关（P〈0．01），与浸润深度、分化程度和TNM分期无关（P〉0．05）。P—ERK蛋白在胃癌中表达的阳性率（86．15％）明显高于相应正常组织（16．92％）（P〈0．01），其表达水平与浸润深度、淋巴结转移及TNM分期有关（P〈0．05），与分化程度无关（P〉0．05）。胃癌组织中PTEN和P—AKT、PTEN和P—ERK蛋白表达之间呈明显负相关（P〈0．01）。结论：PTEN的低表达或失表达，可能与P—AKT、P—ERK的异常激活有一定联系，从而对胃癌的发生、发展起重要作用。     

Isoalantolactone induces apoptosis through ROS-mediated ER stress and inhibition of STAT3 in prostate cancer cells

Background

Prostate cancer is one of the most commonly diagnosed cancers in men worldwide. Currently available therapies for metastatic prostate cancer are only marginally effective. Therefore, new therapeutic agents are urgently needed to improve patient outcome. Isoalantolactone (IATL), an active sesquiterpene naturally present in many vegetables and medicinal plants, is known to induce cell death and apoptosis in various cancer cell lines. Nevertheless, antitumor mechanisms initiated by IATL in cancer cells have not been fully defined.

Methods

Cell apoptosis and cellular ROS levels were analyzed by flow cytometry. Western blot and qRT-PCR were used to analyze the protein and mRNA levels of indicated molecules, respectively. Nude mice xenograft model was used to test the effects of IATL on prostate cancer cell growth in vivo.

Results

In this study, we found that IATL dose-dependently inhibited cancer cell growth and induced apoptosis in PC-3 and DU145 cells. Mechanistically, our data found that IATL induced reactive oxygen species (ROS) production, resulting in the activation of endoplasmic reticulum stress pathway and eventually cell apoptosis in prostate cancer cells. IATL also decreased the protein expression levels of p-STAT3 and STAT3, and the effects of IATL were reversed by pretreatment with N-acetyl-L-cysteine (NAC). In vivo, we found that IATL inhibited the growth of prostate cancer xenografts without exhibiting toxicity. Treatment of mice bearing human prostate cancer xenografts with IATL was also associated with induction of ER stress and inhibtion of STAT3.

Conclusion

In summary, our results unveil a previously unrecognized mechanism underlying the biological activity of IATL, and provide a novel anti-cancer candidate for the treatment of prostate cancer.

     

Growth-stimulatory activity of TIMP-2 is mediated through c-Src activation followed by activation of FAK,PI3-kinase/AKT,and ERK1/2 independent of MMP inhibition in lung adenocarcinoma cells

Tissue inhibitors of metalloproteinases (TIMPs) control extracellular matrix (ECM) homeostasis by inhibiting the activity of matrix metalloproteinases (MMPs), which are associated with ECM turnover. Recent studies have revealed that TIMPs are implicated in tumorigenesis in both MMP-dependent and MMP-independent manners. We examined a mechanism by which TIMP-2 stimulated lung adenocarcinoma cell proliferation, independent of MMP inhibition. The stimulation of growth by TIMP-2 in A549 cells required c-Src kinase activation. c-Src kinase activity, induced by TIMP-2, concomitantly increased FAK, phosphoinositide 3-kinase (PI3-kinase)/AKT, and ERK1/2 activation. Selective knockdown of integrin α3β1, known as a TIMP-2 receptor, did not significantly change TIMP-2 growth promoting activity. Furthermore, we showed that high TIMP-2 expression in lung adenocarcinomas is associated with a worse prognosis from multiple cohorts, especially for stage I lung adenocarcinoma. Through integrated analysis of The Cancer Genome Atlas data, TIMP-2 expression was significantly associated with the alteration of driving genes, c-Src activation, and PI3-kinase/AKT pathway activation. Taken together, our results demonstrate that TIMP-2 stimulates lung adenocarcinoma cell proliferation through c-Src, FAK, PI3-kinase/AKT, and ERK1/2 pathway activation in an MMP-independent manner.     

Statin-induced apoptosis via the suppression of ERK1/2 and Akt activation by inhibition of the geranylgeranyl-pyrophosphate biosynthesis in glioblastoma

Background

Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. The inhibition of this key enzyme in the mevalonate pathway leads to suppression of cell proliferation and induction of apoptosis. However, the molecular mechanism of apoptosis induction by statins is not well understood in glioblastoma. In the present study, we attempted to elucidate the mechanism by which statins induce apoptosis in C6 glioma cells.

Methods

The cytotoxicity of statins toward the C6 glioma cells were evaluated using a cell viability assay. The enzyme activity of caspase-3 was determined using activity assay kits. The effects of statins on signal transduction molecules were determined by western blot analyses.

Results

We found that statins inhibited cell proliferation and induced apoptosis in these cells. We also observed an increase in caspase-3 activity. The apoptosis induced by statins was not inhibited by the addition of farnesyl pyrophosphate, squalene, ubiquinone, and isopentenyladenine, but by geranylgeranyl-pyrophosphate (GGPP). Furthermore, statins decreased the levels of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt.

Conclusions

These results suggest that statins induce apoptosis when GGPP biosynthesis is inhibited and consequently decreases the level of phosphorylated ERK1/2 and Akt. The results of this study also indicate that statins could be used as anticancer agents in glioblastoma.     

ERK参与裸鼠体内辛伐他汀诱导K 562细胞凋亡的调控作用

目的：探讨辛伐他汀（simvastatin）作用于裸鼠体内K562细胞后Ras-MAPK信号转导通路胞外信号调节激酶（extracellular signal—regulated protein kinase，ERK）分子水平的变化，以说明ERK参与裸鼠体内辛伐他汀诱导K562细胞凋亡的调控作用。方法：体外培养慢性髓细胞白血病（CML）细胞株K562细胞，构建BALB／c-nu／nu裸鼠的K562细胞移植瘤模型。流式细胞术（FCM）检测对照组和两个辛伐他汀处理组的K562细胞周期变化，TUNEL法检测K562细胞晚期凋亡情况。采用RT-PCR检测K562细胞中Ras-MAPK信号通路N-Ras、ERK1mRNA的差异表达。免疫组织化学标记葡聚糖聚合物（labbled dextran polymer，LDP）法检测P-ERK蛋白水平变化。结果：辛伐他汀能够明显抑制裸鼠K562移植瘤组织的增长，随着辛伐他汀剂量的增加，K562细胞移植瘤体积和质量明显减小（P〈0．05，P〈0．01）。每次注射0．05mg的辛伐他汀能够诱导裸鼠体内K562细胞发生明显的G0／G1期停滞，不同剂量的辛伐他汀能够诱导K562细胞发生明显的凋亡，并随剂量的增加，凋亡率逐渐增高（P〈0．01）；不同剂量的辛伐他汀能够引起N-Ras、ERK1mRNA的表达下调（P〈0．01）。与对照组相比，两个处理组的p-ERK蛋白分别出现表达下调（P=0．01，P〈0．01）。结论：辛伐他汀在体内可能依赖Ras—MAPK信号转导通路ERK基因和蛋白水平的表达下调诱导K562细胞凋亡发生。