IOX-101 Reverses Drug Resistance Through Suppression of Akt/mTOR/NF-κB Signaling in Cancer Stem Cell-Like,Sphere-Forming NSCLC Cell

Drug discovery research to fight lung cancer is incessantly challenged by drug resistance. In this study, we used drug-resistant lung cancer stem like cells (A549-CS) to compare the efficacy of standard drugs like cisplatin (DDP) and gemcitabine (GEM) with a novel arylidene derivative IOX-101. A549-CS was derived from regular A549 cells by growing in special media. Resistance proteins were detected using Western blotting. Cell proliferations were assessed by MTT assay. Cytokine release was enumerated using enzyme-linked immunosorbent assay. The effect of drugs on apoptosis and cell cycle was studied with flow cytometry protocols. Apoptosis-related proteins, caspases, and other signaling protein expressions like Akt and mammalian target of rapamycin (mTOR) were assessed by Western blotting. Expression of CD133 and nuclear factor B (NF- B) phosphorylation was assessed using flow cytometry. A549-CS showed significant increase in CD133 expression in comparison with A549 cells. Expression of resistance markers like MDR-1, lung resistance protein (LRP), and GST-II were detected in A549-CS. While DDP and GEM had relatively lower efficacy in A549-CS, IOX-101 inhibited the proliferation of both A549 and A549-CS with GI₅₀ values of 268 and 296.5 nM, respectively. IOX-101 increased the sub-G₀ phase in the cell cycle of A549-CS and increased the percentage of apoptotic cells. Western blot analysis revealed activation of caspases, Bax, and reduction in Bcl-2 levels. Further mechanistic investigation revealed IOX-101 to deactivate Akt, mTOR, and NF- B signaling in A549-CS cells. Additionally, IOX-101 treatment to A549-CS also reversed MDR-1 and LRP expressions. Collectively, our results demonstrate efficacy of IOX-101 in A549-CS, which was resistant against the tested standard drugs. The activity was mediated by suppressing Akt/mTOR/NF- B signaling.     

雷帕霉素对肺癌细胞mTOR信号通路相关蛋白表达的作用

目的探讨mTOR信号通路的功能状态与肺癌对雷帕霉素敏感度的关系。方法Western blot检测mTOR信号通路中AKT、S6K1、eIF4E、4E-BP1、P-S6K1蛋白在4种人肺癌细胞株的表达;MTT法检测雷帕霉素对肺癌细胞增殖的抑制情况,将肺癌细胞分为雷帕霉素敏感组和不敏感组,找出与敏感度相关的差异蛋白,用En Vision法检测患者肺癌组织中差异蛋白的表达。结果AKT、S6K1、eIF4E、4E-BP1蛋白在4种肺癌细胞株中均有表达。而P-S6K1在不敏感株中未检测到, 在敏感株中呈高表达,为雷帕霉素差异蛋白。P-S6K1在正常肺组织中的阳性表达率为15％（3/20例),在肺癌组织中的阳性表达率为62%(62/100例),其中在小细胞肺癌组织中的阳性表达率(81.0%,17/21例)高于非小细胞肺癌组织（59%,45/79例)。结论在mTOR信号通路相关蛋白中,仅P-S6K1在一定程度上可预测肺癌细胞株对雷帕霉素的敏感度,为一种mTOR靶向抑制剂——雷帕霉素治疗肺癌的差异蛋白。P-S6K1在小细胞肺癌中表达较非小细胞肺癌高,提示在P-S6K1表达率高的小细胞未分化肺癌中应用mTOR靶向抑制剂——雷帕霉素的疗效可能更佳。     

Dual inhibition of phosphatidylinositol 3-kinase/Akt and mammalian target of rapamycin signaling in human nonsmall cell lung cancer cells by a dietary flavonoid fisetin

Lung cancer is one of the most commonly occurring malignancies. It has been reported that mammalian target of rapamycin (mTOR) is phosphorylated in lung cancer and its activation was more frequent in tumors with overexpression of phosphatidylinositol 3-kinase (PI3K)/Akt. Therefore, dual inhibitors of PI3K/Akt and mTOR signaling could be valuable agents for treating lung cancer. In the present study, we show that fisetin, a dietary tetrahydroxyflavone inhibits cell growth with the concomitant suppression of PI3K/Akt and mTOR signaling in human nonsmall cell lung cancer (NSCLC) cells. Using autodock 4, we found that fisetin physically interacts with the mTOR complex at two sites. Fisetin treatment was also found to reduce the formation of A549 cell colonies in a dose-dependent manner. Treatment of cells with fisetin caused decrease in the protein expression of PI3K (p85 and p110), inhibition of phosphorylation of Akt, mTOR, p70S6K1, eIF-4E and 4E-BP1. Fisetin-treated cells also exhibited dose-dependent inhibition of the constituents of mTOR signaling complex such as Rictor, Raptor, GβL and PRAS40. There was an increase in the phosphorylation of AMPKα and a decrease in the phosphorylation of TSC2 on treatment of cells with fisetin. We also found that treatment of cells with mTOR inhibitor rapamycin and mTOR-siRNA caused decrease in phosphorylation of mTOR and its target proteins which were further downregulated on treatment with fisetin, suggesting that these effects are mediated in part, through mTOR signaling. Our results show that fisetin suppressed PI3K/Akt and mTOR signaling in NSCLC cells and thus, could be developed as a chemotherapeutic agent against human lung cancer.     

β-elemene suppresses tumor metabolism and stem cell-like properties of non-small cell lung cancer cells by regulating PI3K/AKT/mTOR signaling

Multi-drug resistance remains a critical issue in cancer treatment that hinders the effective use of chemotherapeutic drugs. The active components of traditional Chinese medicine have been applied as adjuvants to accentuate the anticancer properties of conventional drugs such as cisplatin. However, their application requires further validation and optimization. This study explored the anticancer activity of β-elemene, a natural component of traditional Chinese medical formulations. The effect of β-elemene on the anticancer properties of cisplatin was evaluated in A549 and NCI-H1650 lung cancer cells. Cell apoptosis, stem-like properties, glucose metabolism, multi-drug resistance, and PI3K/AKT/mTOR activation were assessed via flow cytometry, tumorsphere formation, and western blotting. The target genes of β-elemene were predicted using bioinformatics tools and validated in both cell lines. A xenograft model of lung cancer was established in nude mice to evaluate the combined effects of β-elemene and cisplatin in vivo. We found that β-elemene acted synergistically with cisplatin against non-small cell lung cancer cells by promoting apoptosis and impairing glucose metabolism, multi-drug resistance, and stemness maintenance. These effects were mediated by the inhibition of PI3K/AKT/mTOR activation. Bioinformatics analysis revealed that RB1 and TP53 are common target genes associated with lung cancer and β-elemene. The anti-tumorigenic properties of β-elemene were confirmed in vivo, wherein β-elemene, along with cisplatin, significantly suppressed tumor growth in a mouse xenograft model of non-small cell lung cancer. As such, β-elemene acted as an inhibitor of PI3K/AKT/mTOR signaling and enhanced the anticancer effect of cisplatin by targeting tumor metabolism, chemoresistance, and stem-like behavior. Thus, β-elemene is an effective anticancer adjuvant agent with potential clinical applications.     

Activation of Akt and eIF4E survival pathways by rapamycin-mediated mammalian target of rapamycin inhibition

The mammalian target of rapamycin (mTOR) has emerged as an important cancer therapeutic target. Rapamycin and its derivatives that specifically inhibit mTOR are now being actively evaluated in clinical trials. Recently, the inhibition of mTOR has been shown to reverse Akt-dependent prostate intraepithelial neoplasia. However, many cancer cells are resistant to rapamycin and its derivatives. The mechanism of this resistance remains a subject of major therapeutic significance. Here we report that the inhibition of mTOR by rapamycin triggers the activation of two survival signaling pathways that may contribute to drug resistance. Treatment of human lung cancer cells with rapamycin suppressed the phosphorylation of p70S6 kinase and 4E-BP1, indicating an inhibition of mTOR signaling. Paradoxically, rapamycin also concurrently increased the phosphorylation of both Akt and eIF4E. The rapamycin-induced phosphorylation of Akt and eIF4E was suppressed by the phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002, suggesting the requirement of PI3K in this process. The activated Akt and eIF4E seem to attenuate rapamycin's growth-inhibitory effects, serving as a negative feedback mechanism. In support of this model, rapamycin combined with LY294002 exhibited enhanced inhibitory effects on the growth and colony formation of cancer cells. Thus, our study provides a mechanistic basis for enhancing mTOR-targeted cancer therapy by combining an mTOR inhibitor with a PI3K or Akt inhibitor.     

HS3ST1对肺癌细胞增殖、迁移、侵袭及顺铂耐药的作用机制研究

目的:研究HS3ST1对肺癌细胞A549增殖、迁移、侵袭及顺铂耐药的影响.方法:利用慢病毒感染并构建HS3ST1过表达细胞株;利用Western blot、RT-PCT检测HS3ST1的表达;利用CCK8实验、Transwell迁移实验和细胞毒性实验检测HS3ST1对A549细胞增殖、迁移、侵袭和顺铂耐药的影响;利用W...     

PI3K independent activation of mTORC1 as a target in lapatinib-resistant ERBB2+ breast cancer cells

Therapies targeting the ERBB2 receptor, including the kinase inhibitor lapatinib (Tykerb, GlaxoSmithKline), have improved clinical outcome for women with ERBB2-amplified breast cancer. However, acquired resistance to lapatinib remains a significant clinical problem, and the mechanisms governing resistance remain poorly understood. We sought to define molecular alterations that confer an acquired lapatinib resistance phenotype in ER?/ERBB2+ human breast cancer cells. ERBB2-amplified SKBR3 breast cancer cells were rendered resistant to lapatinib via culture in increasing concentrations of the drug, and molecular changes associated with a resistant phenotype were interrogated using a collaborative enzyme-enhanced immunoassay platform and immunoblotting techniques for detection of phosphorylated signaling cascade proteins. Interestingly, despite apparent inactivation of the PI3K/AKT signaling pathway, resistant cells exhibited constitutive activation of mammalian target of rapamycin complex 1 (mTORC1) and were highly sensitive to mTOR inhibition with rapamycin and the dual PI3K/mTOR inhibitor NVP-BEZ235. These data demonstrate a role for downstream activation of mTORC1 in the absence of molecular alterations leading to PI3K/AKT hyperactivation as a potential mechanism of lapatinib resistance in this model of ERBB2+ breast cancer and support the rationale of combination or sequential therapy using ERBB2 and mTOR-targeting molecules to prevent or target resistance to lapatinib. Moreover, our data suggest that assessment of mTOR substrate phosphorylation (i.e., S6) may serve as a more robust biomarker to predict sensitivity to mTOR inhibitors in the context of lapatinib resistance than PI3K mutations, loss of PTEN and p-AKT levels.     

IL-6 signaling contributes to cisplatin resistance in non-small cell lung cancer via the up-regulation of anti-apoptotic and dna repair associated molecules

Cisplatin-based chemotherapy is currently the most effective treatment regimen for non-small cell lung cancer (NSCLC), but eventually tumor resistance develops which limits its success. The potential implication of IL-6 signaling in the cisplatin resistance of NSCLC was explored by testing whether NSCLC cells with different levels of intracellular IL-6 show different responses to the cytotoxic treatment of cisplatin. When the cisplatin cytotoxicity of the IL-6 knocked down human NSCLC cells (A549IL-6si and H157IL-6si) were compared with their corresponding scramble control cells (A549sc and H157sc), higher cisplatin cytotoxicity was found in IL-6 si cells than sc cells. Subcutaneous xenograft mouse models were developed using a pair of A549sc and A549IL-6si cells. When the tumor grew to about 400 mm², mice were treated with cisplatin and tumor regression was monitored. Higher tumor regression was detected in the A549IL-6si xenografts compared to A549sc xenografts following cisplatin treatment. Immunostaining study results from tumor tissues also supported this finding. Expression of anti-apoptotic proteins Bcl-2 and Mcl-1 and DNA repair associated molecules ATM, CHK1, TP73, p53, and ERCC1 were significantly up regulated in cisplatin-treated A549sc and H157sc cells, but no increase was detected in A549IL-6si and H157IL-6si cells. Further inhibitor studies revealed that up regulation of these molecules by IL-6 may be through activation of IL-6 downstream signaling pathways like Akt, MAPK, Stat3, and Erk. These results provide potential for combining cisplatin and inhibitors of IL-6 signaling or its downstream signaling pathway as a future therapeutic approach in preventing development of cisplatin resistant NSCLC tumors.     

Rapamycin suppresses ROS-dependent apoptosis caused by selenomethionine in A549 lung carcinoma cells

Purpose

Although selenium compounds possess chemotherapeutic features by inducing apoptosis in cancer cells with trivial side effects on normal cells, the mechanisms underlying its anti-cancer activity are insufficiently understood at the present. In this study, we investigated the effects of rapamycin on apoptosis induced by seleno-L-methionine (SeMet) or selenite in A549 cells.

Methods

The effects of Se compounds, SeMet and selenite, on cell proliferation, apoptosis and its signaling pathway were investigated in established human adenocarcinoma cell line (A549). Cancer cells were treated with each Se during different periods. Cell apoptosis and signaling molecules were analyzed by flow cytometry (TUNEL method) or immunoblotting, respectively.

Results

SeMet induces reactive oxygen species generation associated with the induction of apoptosis, because pretreatment of cells with N-acetyl-L-cysteine completely blocked SeMet-induced apoptosis. We also found that rapamycin completely suppressed the apoptosis of cells treated by SeMet, but not selenite. SeMet-induced apoptosis is significantly downregulated in combination with PI3?K family inhibitors (LY294002, wortmannin, PI-103, and 3-methyladenine). In addition, ROS generation was included in downstream signaling events associated with the phosphorylation of mTOR, because pretreatment of cells with rapamycin inhibited ROS generation.

Conclusion

These results suggest that SeMet-induced apoptosis is affected by the Akt/mTOR/ROS pathway in A549 cells. Akt serves an anti-survival function in the system of SeMet-treated lung cancer cells, but autophagic signaling remained unsolved.     

Inhibition of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin pathway but not the MEK/ERK pathway attenuates laminin-mediated small cell lung cancer cellular survival and resistance to imatinib mesylate or chemotherapy

The fact that small cell lung cancer (SCLC) is commonly incurable despite being initially responsive to chemotherapy, combined with disappointing results from a recent SCLC clinical trial with imatinib, has intensified efforts to identify mechanisms of SCLC resistance. Adhesion to extracellular matrix (ECM) is one mechanism that can increase therapeutic resistance in SCLC cells. To address whether adhesion to ECM increases resistance through modulation of signaling pathways, a series of SCLC cell lines were plated on various ECM components, and activation of two signaling pathways that promote cellular survival, the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway and the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) pathway, was assessed. Although differential activation was observed, adhesion to laminin increased Akt activation, increased cellular survival after serum starvation, and caused the cells to assume a flattened, epithelial morphology. Inhibitors of the PI3K/Akt/mTOR pathway (LY294002, rapamycin) but not the MEK/ERK pathway (U0126) abrogated laminin-mediated survival. SCLC cells plated on laminin were not only resistant to serum starvation-induced apoptosis but were also resistant to apoptosis caused by imatinib. Combining imatinib with LY294002 or rapamycin but not U0126 caused greater than additive increases in apoptosis compared with apoptosis caused by the inhibitor or imatinib alone. Similar results were observed when adenoviruses expressing mutant Akt were combined with imatinib, or when LY294002 was combined with cisplatin or etoposide. These studies identify laminin-mediated activation of the PI3K/Akt/mTOR pathway as a mechanism of cellular survival and therapeutic resistance in SCLC cells and suggest that inhibition of the PI3K/Akt/mTOR pathway is one strategy to overcome SCLC resistance mediated by ECM.     

扶正抑瘤汤通过PI3K/Akt/mTOR信号通路抑制非小细胞肺癌增殖、凋亡及自噬

目的 探讨扶正抑瘤汤对非小细胞肺癌细胞增殖、侵袭、迁移、凋亡、自噬以及PI3K/Akt/mTOR信号通路的影响。方法 采用不同浓度（12.5 mg/mL、25 mg/mL、50 mg/mL、100 mg/mL、200 mg/mL、400 mg/mL）扶正抑瘤汤体外培养非小细胞肺癌A549细胞, CCK-8法测定细胞增殖抑制率;Transwell小室侵袭实验检测细胞侵袭能力;划痕实验检测细胞迁移能力;流式细胞仪检测细胞凋亡率;Western blot检测细胞自噬相关蛋白以及PI3K/Akt/mTOR信号通路相关蛋白的表达水平;透射电镜下观察自噬溶酶体形成情况。结果 200 mg/mL和400 mg/mL扶正抑瘤汤作用后A549细胞增殖抑制率增加（均P<0.05）。200 mg/mL扶正抑瘤汤作用后A549细胞侵袭和迁移能力降低（均P<0.05）;细胞凋亡率增加（P<0.05）;Beclin-1、LC3Ⅱ/Ⅰ蛋白的表达水平升高（均P<0.05）,P62蛋白的表达水平降低（P<0.05）;A549细胞自噬溶酶体数量增加;p-PI3K/PI3K、p-Akt/Akt和p-mTOR/mTOR蛋白的表达降低（均P<0.05）。结论 扶正抑瘤汤可以抑制A549细胞增殖,并促进细胞凋亡和自噬,可能与PI3K/Akt/mTOR信号通路失活有关,是治疗非小细胞肺癌的潜在药物。     

Remarkable inhibition of mTOR signaling by the combination of rapamycin and 1,4-phenylenebis(methylene)selenocyanate in human prostate cancer cells

Preclinical studies and clinical analyses have implicated the mammalian target of rapamycin (mTOR) pathway in the progression of prostate cancer, suggesting mTOR as a potential target for new therapies. mTOR, a serine/threonine kinase, belongs to two distinct signaling complexes: mTORC1 and mTORC2. We previously showed that the synthetic organoselenium compound, p-XSC, effectively inhibits viability and critical signaling molecules (e.g., androgen receptor, Akt) in androgen responsive (AR) and androgen independent (AI) human prostate cancer cells. On the basis of its inhibition of Akt, we hypothesized that p-XSC modulates mTORC2, an upstream regulator of the kinase. We further hypothesized that combining p-XSC with rapamycin, an mTORC1 inhibitor, would be an effective combinatory strategy for the inhibition of prostate cancer. The effects of p-XSC and rapamycin, alone or in combination, on viability and mTOR signaling were examined in AR LNCaP prostate cancer cells and AI C4-2 and DU145 cells. Phosphorylation of downstream targets of mTORC1 and mTORC2 was analyzed by immunoblotting. The interaction of mTORC1- and mTORC2-specific proteins with mTOR was probed through immunoprecipitation and immunoblotting. p-XSC inhibited phosphorylation of mTORC2 downstream targets, Akt and PCKα, and decreased the levels of rictor, an mTORC2-specific protein, coimmunoprecipitated with mTOR in C4-2 cells. The combination of p-XSC and rapamycin more effectively inhibited viability and mTOR signaling in C4-2, LNCaP and DU145 cells than either agent individually.     

The Akt/mammalian target of rapamycin signal transduction pathway is activated in high-risk myelodysplastic syndromes and influences cell survival and proliferation

The Akt/mammalian target of rapamycin (mTOR) signaling pathway is important for both cell growth and survival. In particular, an impaired regulation of the Akt/mTOR axis has been strongly implicated in mechanisms related to neoplastic transformation, through enhancement of cell proliferation and survival. Myelodysplastic syndromes (MDS) are a group of heterogeneous hematopoietic stem cell disorders characterized by ineffective hematopoiesis and by a high risk of evolution into acute myelogenous leukemia (AML). The pathogenesis of the MDS evolution into AML is still unclear, although some recent studies indicate that aberrant activation of survival signaling pathways could be involved. In this investigation, done by means of immunofluorescent staining, we report an activation of the Akt/mTOR pathway in high-risk MDS patients. Interestingly, not only mTOR was activated but also its downstream targets, 4E-binding protein 1 and p70 ribosomal S6 kinase. Treatment with the selective mTOR inhibitor, rapamycin, significantly increased apoptotic cell death of CD33(+) (but not CD33(-)) cells from high-risk MDS patients. Rapamycin was ineffective in cells from healthy donors or low-risk MDS. Moreover, incubation of high-risk MDS patient CD34(+) cells with rapamycin decreased the in vitro clonogenic capability of these cells. In contrast, the phosphoinositide 3-kinase inhibitor, LY294002, did not significantly affect the clonogenic activity of high-risk MDS cells. Taken together, our results indicate that the Akt/mTOR pathway is critical for cell survival and proliferation in high-risk MDS patients. Therefore, this signaling network could become an interesting therapeutic target for treating more advanced MDS cases.     

苯丁酸调控对顺铂抑制人肺腺癌A549/DDP耐药细胞株增殖与侵袭协同作用研究

目的肺癌已成为威胁人类生存的重要杀手,且随着环境恶化,其发病率和死亡率有逐年升高趋势。本研究分析4-苯丁酸对顺铂作用下人肺腺癌耐药细胞株A549/DDP细胞增殖和侵袭影响,为临床治疗提供参考。方法体外培养人肺腺癌耐药细胞株A549/DDP至生长状态良好,分析顺铂及4-苯丁酸联合顺铂对A549/DDP细胞株增殖作用,酶联免疫吸附测定法分析细胞凋亡相关蛋白表达变化,Transwell实验分析细胞侵袭力变化,蛋白质印迹法和免疫细胞化学分析细胞中JAK/STAT信号通路蛋白表达变化。结果随着时间延长,各组对A549/DDP细胞株增殖抑制率呈上升趋势,且高剂量4-苯丁酸联合顺铂组对A549/DDP细胞株增殖抑制率较高,差异有统计学意义,F药物=110.342,P<0.001;F时间=34.527,P<0.001;F药物×时间=58.321,P<0.001。与对照组相比,低剂量4-苯丁酸联合顺铂组和高剂量4-苯丁酸联合顺铂组细胞凋亡蛋白Bcl-2水平降低,Bax、Caspase-3和Caspase-6水平升高,均P<0.001。对照组、顺铂组、低剂量4-苯丁酸联合顺铂组和高剂量4-苯丁酸联合顺铂组细胞侵袭力分别为423.3±35.6、389.3±24.7、375.6±35.2和285.6±23.9,F=44.458,P<0.001;蛋白质印迹法检测发现对照组、顺铂组、低剂量4-苯丁酸联合顺铂组和高剂量4-苯丁酸联合顺铂组JAK2水平分别为1.32±0.26、1.01±0.24、0.90±0.12和0.74±0.13,F=18.633,P<0.001;STAT2水平分别为0.78±0.13、0.70±0.15、0.62±0.09和0.54±0.09,F=18.996,P<0.001;STAT3水平分别为1.01±0.23、0.89±0.14、0.74±0.10和0.40±0.10,F=19.687,P<0.001。免疫细胞化学法检测发现对照组、顺铂组、低剂量4-苯丁酸联合顺铂组和高剂量4-苯丁酸联合顺铂组JAK2水平分别为0.85±0.14、0.78±0.11、0.62±0.17和0.52±0.09,F=21.854,P<0.001;STAT2水平分别为0.85±0.20、0.77±0.14、0.69±0.08和0.52±0.13,F=17.852,P<0.001;STAT3水平分别为0.63±0.14、0.57±0.11、0.50±0.09和0.42±0.08,F=29.754,P<0.001。结论4-苯丁酸调控对顺铂作用下人肺腺癌耐药细胞株A549/DDP细胞增殖、侵袭有明显抑制作用,且其作用可能与影响JAK/STAT信号通路蛋白表达有关。