抑制P13K／Akt通路提高肺腺癌细胞化疗的效果

摘要：目的探讨PI3K／Akt信号转导通路抑制剂LY294002对肺腺癌细胞株A549及裸鼠移植瘤化疗的增敏作用。方法采用MTT法及流式细胞仪检测LY294002、紫杉醇、LY294002联合紫杉醇对A549细胞增殖及凋亡的影响；通过裸鼠移植瘤模型检测LY294002、紫杉醇、LY294002联合紫杉醇对A549细胞成瘤性的影响。结果LY294002可增强紫杉醇对A549细胞的抑制作用，并且可提高其凋亡率。裸鼠移植瘤实验显示，LY294002与紫杉醇均可抑制移植瘤的生长，联用后抑瘤率增加。结论LY294002可增强紫杉醇对A549细胞、裸鼠移植瘤的化疗的敏感性，抑制PI3K／Akt信号转导通路可提高肺腺癌化疗的效果。     

通路抑制剂LY294002对子宫内膜癌裸鼠移植瘤的抑制作用

目的:观察磷脂酰肌醇3激酶通路抑制剂LY294002对子宫内膜癌裸鼠移植瘤细胞增殖、凋亡及p-AKT表达的影响.方法:体外培养人子宫内膜癌Ishikawa细胞,12只裸鼠皮下接种Ishikawa细胞后建立子宫内膜癌裸鼠移植瘤模型,随机分为2组,每组6只,分别给予腹腔注射生理盐水和LY294002干预,观察2组移植瘤的生长情况,绘制肿瘤生长曲线,计算移植瘤体积、抑瘤率等,观察药物对移植瘤的抑制作用,移植瘤组织标本进行HE染色镜下观察移植瘤的坏死程度、范围及细胞凋亡情况,并用免疫组织化学方法检测移植瘤组织内p-AKT的表达.结果:1)用药组裸鼠移植瘤体积增长相对缓慢(2 027.30±251.16)mm3,对照组肿瘤体积增长明显(3 110.60±599.66)mm3,差异有统计学意义(t=4.082,P=0.005),且抑瘤率为(32.49±16.39)%.2)HE染色见用药组较对照组移植瘤细胞凋亡及坏死面积显著增加;免疫组化结果显示用药组p-AKT的表达低于对照组(χ2=6.133,P<0.05).结论:PI3K通路抑制剂LY294002能够抑制子宫内膜癌裸鼠移植瘤的生长,促进其凋亡.     

双歧杆菌对实验性大肠癌化bcl-2及bax基因表达的影响

目的 通过观察大肠癌裸鼠移植瘤bcl-2及bax基因的蛋白表达水平,探讨双歧杆菌的抑瘤途径及机制.方法 采用免疫组化SP法检测了40只裸鼠大肠癌移植瘤bcl-2及bax基因的蛋白表达率及表达强度.结果 双歧杆菌注射组大肠癌移植瘤bcl-2蛋白表达率及阳性细胞密度均低于肿瘤对照组,bax基因的表达情况则相反.结论 双歧杆菌可使大肠癌裸鼠移植瘤的bcl-2基因表达下调,bax基因表达增强,最终诱导肿瘤细胞凋亡,实现其抗瘤目的.     

多西紫杉醇联合曲格列酮对人前列腺癌裸鼠移植瘤的抑制作用

目的:探讨多西紫杉醇联合曲格列酮(troglitazone,TGZ)对人前列腺癌裸鼠移植瘤的抑制作用,并初步探索其作用机制.方法:建立人前列腺癌裸鼠移植瘤模型,观察多西紫杉醇联合TGZ对移植瘤生长的抑制作用,FCM法检测移植瘤细胞的凋亡率,免疫组织化学法检测移植瘤组织中bcl-2和bax蛋白的表达情况.结果:与对照组比较, 多西紫杉醇联合TGZ可明显抑制人前列腺癌裸鼠移植瘤的生长,肿瘤体积和质量明显下降,细胞凋亡率明显上升;免疫组织化学法检测结果显示,移植瘤组织中bax蛋白的表达明显增强,bcl-2蛋白的表达明显减弱.结论:多西紫杉醇联合TGZ对前列腺癌有一定的抑制作用,其作用机制可能是通过上调促凋亡蛋白bax的表达及下调抗凋亡蛋白bcl-2的表达,导致肿瘤细胞加速凋亡而实现的.     

LY294002抑制PI3K/AKT信号通路对胃腺癌SGC-7901 细胞的影响

目的:观察应用PI3K抑制剂2-(4-吗啉基)-8-苯基-4氢-1-苯并吡喃-4酮(LY294002)对胃腺癌细胞株SGC-7901中磷脂酰肌酸3-激酶(PI3K)/丝氨酸苏氨酸激酶(AKT)信号通路的变化以及由此产生的细胞生长、侵袭及凋亡等方面的影响.方法:应用LY294002作用于胃腺癌细胞株SGC-7901,通过Western blot检测PI3K/AKT信号通路中相关蛋白质P-AKT、基质金属蛋白酶-2(MMP-2)、基质金属蛋白酶-9(MMP-9)、B细胞淋巴瘤/白血病-2(Bcl-2)、细胞周期素(CyclinD1)的表达情况.噻唑蓝比色法(MTT)和流式细胞法及Transwell等实验评价胃腺癌细胞增殖、侵袭、凋亡等变化.结果:与空白对照组和DMSO组相比,LY294002组能有效抑制P-AKT、MMP-2、MMP-9、Bcl-2及CyclinD1蛋白的表达.LY294002组自第2天起生存率明显下降(P<0.05).Transwell穿过细胞数结果分别为空白对照组(81.0±2.65)、DMSO组(81.3±1.52)、LY294002组(44.6±2.52),3组相比较差异具有统计学意义(F=255.1,P=0.000).LY294002组细胞周期被阻滞在G0/G1期,S期减少(P<0.05),早期凋亡的细胞数明显增多(F=149.66,P=0.000).结论:LY294002是一种对PI3K/AKT信号传导通路具有抑制作用的抑制剂,靶向PI3K的LY294002可以有效抑制胃腺癌SGC-7901细胞的PI3K/AKT信号通路中相关蛋白质的表达,在体外显著抑制细胞的增殖、侵袭,并促进细胞的凋亡,因此为临床肿瘤防治提供了新思路,针对信号传导通路的靶向治疗有望成为肿瘤治疗的新途径.     

人类端粒酶反转录酶C27多肽过表达对鼻咽癌裸鼠移植瘤生长的影响

目的 研究人类端粒酶反转录酶C27多肽（hTERTC27）过表达对鼻咽癌C666-1细胞移植瘤生长的影响。方法 利用稳定转染质粒pcDNA3.1（对照组）与pcDNA3.1-hTERTC27（hTERTC27组）的C666-1细胞株建立裸鼠鼻咽癌皮下移植瘤模型。观察肿瘤生长情况,绘制肿瘤生长曲线,处死后剥离肿瘤,进行HE染色观察组织形态学变化。采用Western blot法观察肿瘤组织中剪切后的Caspase-3、Caspase-9、PARP以及bax和bcl-2的表达。结果 小鼠荷瘤第8天后,hTERTC27组移植瘤的体积明显小于对照组（P＜0.05）,肿瘤的重量明显低于对照组（P＜0.05）,局部肌肉浸润现象较少。hTERTC27组移植瘤Caspase-3、Caspase-9、PARP、bax的表达量增加（P＜0.01）,而bcl-2的表达量降低（P＜0.01）。结论 hTERTC27减缓裸鼠鼻咽癌皮下移植瘤的生长速度并促进其凋亡,可能与其上调bax蛋白的表达和下调bcl-2蛋白的表达有关。     

Ad-PTEN增强LY294002对人胶质瘤细胞系U251的生长抑制作用

目的在体外实验中,利用携带野生型PTEN基因的重组腺病毒（Ad—PTEN）和P13K的小分子抑制剂LY294002联合抑制P13K／AKT信号通路,观察两者联合对人胶质瘤细胞系U251生长有无正向协同作用及探讨产生这种作用的机制。方法15251细胞按处理方式不同分为4组：DMSO对照组、空载病毒对照组、LY294002组和联合组（LY294002＋Ad—PTEN组）。在U251细胞系中导入LY294002并转染Ad—PTEN病毒后,提取总蛋白,用Westernblotting检测PTEN表达状态及P13K、AKT表达情况;用MTT法检测Ad—PTEN和LY294002对U251生长抑制率、流式细胞仪检测细胞周期、AnnexinV法检测细胞凋亡,观察导人LY294002和转染Ad—PTEN后U251增殖能力的改变;用划痕实验、Transwell实验观察LY294002及Ad—PTEN对U251迁移和侵袭能力的影响;Westernblotting检测P13K／AKT信号通路下游相关蛋白表达水平变化。结果Westernblotting显示：与DMSO组和空载病毒组相比,LY294002组P13K、AKT蛋白表达水平明显降低,联合组（LY294002＋Ad—PTEN）的WEN蛋白明显上调,而P13K、AKT蛋白下降水平比LY294002组更为显著。联合组与LY294002组、空载病毒组、DMSO组相比细胞周期阻滞在G0／G1期;联合组凋亡率比其他三组明显增加;自培养第2天起,联合组细胞增殖速率呈下降趋势。联合组侵袭和迁移细胞的相对数少于LY294002组、空载病毒组和DMSO组。Westernblotting结果证明位于P13K／AKT下游的MMP-2、MMP-9、PCNA、Bcl-2、CyclinD1、NF—KB、FAK蛋白表达水平显著下调。结论小分子抑制剂LY294002能够有效抑制U251中P13K、AKT蛋白的表达,联合转染Ad—PTEN后不仅能提高PTEN蛋白的表达水平,对P13K、AKT的抑制更为显著。在体外实验中,联合Ad—PTEN和LY294002能够有效地通过阻滞细胞周期、减少细胞凋亡来抑制U251的增殖能力,并能够抑制细胞的侵袭和迁移能力,两者联合使用具有正向协同作用。联合Ad—PTEN和LY294002对U251的生长与侵袭的抑制作用与P13K／AKT下游的MMP-2、MMP-9、PCNA、Bcl-2、CyclinD1、NF—KB、FAK蛋白表达水平下调有关。联合腺病毒转染技术和小分子抑制剂调控P13K／AKT信号通路是治疗胶质瘤的新途径。     

四硫化四砷对人卵巢癌裸鼠皮下移植瘤抑瘤作用的研究

目的 探讨四硫化四砷(As₄S₄)对卵巢癌裸鼠皮下移植瘤的生长和瘤细胞凋亡的影响。方法 建立卵巢癌SKOV3裸鼠皮下移植瘤模型,观察As₄S₄对肿瘤生长的抑制情况;RT-PCR法检测As₄S₄对卵巢癌裸鼠皮下移植瘤组织中bcl-2和bax mRNA表达水平的影响;Western blot法检测As₄S₄对卵巢癌裸鼠皮下移植瘤组织中bcl-2和bax蛋白表达的影响。结果 As₄S₄作用于卵巢癌裸鼠皮下移植瘤后,肿瘤的体积和重量明显减小,而且随药物剂量的增加抑瘤率明显增加。As₄S₄作用后,RT-PCR可见bcl-2 mRNA表达强度减弱,bax mRNA表达强度增强;Western blot法可见bcl-2蛋白带变细,bax蛋白带增粗。结论 As₄S₄可以抑制卵巢癌裸鼠皮下移植瘤的生长,诱导肿瘤细胞凋亡,其作用机制可能与调节Bcl-2/Bax的表达有关。     

PI3K/AKT信号通路阻断药联合小檗碱对前列腺癌DU145细胞生长的抑制作用

目的 探讨采用磷脂酰肌醇3-激酶(PI3K)抑制药——LY294002抑制磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶(PI3K/AKT)信号通路联合小檗碱对前列腺癌DU145细胞生长的抑制作用.方法 采用MTT法检测细胞增殖情况;采用流式细胞仪检测细胞凋亡率和细胞周期分布情况;采用Western blot检测细胞中PI3K、p-AKT、cyclin D1、bcl-2、BAX蛋白表达情况.结果 随着小檗碱作用浓度的增加,DU145细胞的增殖率逐渐降低;不同浓度小檗碱与LY294002联合处理对DU145细胞增殖的抑制作用均较相同浓度小檗碱单独处理增强(P﹤0.05).与空白对照组相比,小檗碱组DU145细胞的凋亡率增高(P﹤0.05),G0/G1期细胞所占比例增高(P﹤0.05),PI3K、p-AKT、cyclin D1、bcl-2蛋白表达水平均下调(P﹤0.05),BAX蛋白表达水平上调(P﹤0.05).与小檗碱组和空白对照组相比,小檗碱+LY294002组DU145细胞的凋亡率增高(P﹤0.05),G0/G1期细胞所占比例增高(P﹤0.05),PI3K、p-AKT、cyclin D1、bcl-2蛋白表达水平均下调(P﹤0.05),BAX蛋白表达水平上调(P﹤0.05).结论 小檗碱能够抑制DU145细胞增殖,并促进细胞凋亡和细胞周期阻滞,采用LY294002阻断PI3K/AKT信号通路能够明显增强小檗碱对前列腺癌DU145细胞生长的抑制作用.     

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。     

Inhibition of phosphatidylinositol 3'-kinase increases efficacy of paclitaxel in in vitro and in vivo ovarian cancer models

Phosphatidylinositol 3'-kinase (PI3k) is implicated in a wide array of biological and pathophysiological responses. Thus, inhibiting molecules involved in its signal transduction pathway is a possible means of treating cancer. Our previous studies demonstrated that LY294002, a potent and selective PI3k inhibitor, decreases growth of ovarian carcinoma and ascites formation in an athymic mouse xenogeneic transplant model of ovarian cancer. However, the dose of LY294002 used to decrease tumor growth resulted in significant dermatological toxicity. We demonstrate herein that introduction of an active catalytic subunit of PI3k into an ovarian cancer cell line, and thus activation of the PI3k/AKT pathway, confers resistance to the effects of paclitaxel, one of the major drugs used in ovarian cancer therapy. The resistance to paclitaxel can be reversed in vitro by inhibition of PI3k. Therefore, we evaluated whether combined therapy with paclitaxel and LY294002 would result in increased efficacy and allow utilization of doses of LY294002 that do not induce dermatological toxicity. Two weeks after i.p. inoculation with OVCAR-3 ovarian cancer cells, mice were treated i.p. with LY294002 plus paclitaxel, each three times weekly on alternate days, for 4 weeks. Tumor burden in the LY294002 + paclitaxel, LY 294002 alone, and paclitaxel alone groups was reduced by 80% (P < 0.01), 38% (P < 0.05), and 51% (P < 0.05), respectively, compared with controls. Virtually no ascites developed in the combined treatment group; mean volume of ascites in the controls was 3.7 ml. Treatment with LY294002 alone reduced ascites by 70% (P < 0.01), whereas paclitaxel alone reduced ascites slightly but not significantly. No dermatological lesions or weight loss were observed in any treatment group. In vivo and in vitro morphological studies demonstrated that inhibition of PI3k enhanced paclitaxel-induced apoptosis in the human ovarian cancers. Our data suggest that a combination of a PI3k inhibitor and conventional chemotherapy may provide an effective approach to inhibiting tumor growth and ascites production in ovarian cancer with acceptable side effects.     

Dual blockade of phosphatidylinositol 3′-kinase and mitogen-activated protein kinase pathways overcomes paclitaxel-resistance in colorectal cancer

Paclitaxel, one of key drugs to treat a wide range of malignancies, exhibits relative low sensitivity for colorectal cancer. The present study was to examine whether and how phosphatidylinositol 3′-kinase (PI3K) signals affect the sensitivity of colorectal cancer to paclitaxel. Four colorectal cancer cell lines were exposed to paclitaxel in the presence of PI3K signal inhibitors, such as LY294002, siRNA for Akt, or rapamycicn, with or without MAPK inhibitor, PD98059. Cell viability and apoptosis were determined by MTT assay, cell cycle analysis in flow cytometer and Hoechst nuclear staining. To analyze the PI3K activity, the expression in phosphorylated Akt and downstream effectors of p70S6 kinase (S6K) were evaluated by Western blot analysis. Paclitaxel alone (5–10 nM) did not induce the apoptosis in all four cell lines. Although LY294002 alone did not affect the cell viability, it suppressed the Akt and S6K activities and induced the sub-G1 arrest/apoptosis when paclitaxel was co-administered, as well as the Akt siRNA and rapamycin did. Simultaneous blockade of PI3K and MAPK pathways more suppressed the S6K activity and further increased the apoptosis. In conclusion, PI3K is involved in low susceptibility of colorectal cancer to paclitaxel and dual PI3K/MAPK targeting agents may evolve a new paclitaxel-based chemotherapy for colorectal cancer.     

PI3K特异性抑制剂LY294002对卵巢癌紫杉醇耐药细胞株逆转作用的研究

  目的  研究磷脂酰肌醇-3-激酶（PI3K）特异性抑制剂LY294002对卵巢癌紫杉醇耐药细胞株（A2780/Taxol）多药耐药逆转的影响。  方法  将PI3K特异性抑制剂LY294002处理卵巢癌紫杉醇耐药细胞24 h后, 用CCK-8（Cell Counting Kit-8）法检测细胞的增殖速度、对紫杉醇敏感性的分析; 采用流式细胞技术检测细胞周期和凋亡。应用Western blot检测细胞中P-glycoprotein（P-gp）、Akt和p-Akt蛋白的表达情况。  结果  用LY294002处理A2780/Taxol细胞后细胞增殖速度变慢、对紫杉醇的半数抑制浓度（IC₅₀）降低。实验组和对照组细胞的凋亡率分别是（2.64±0.90）%和（10.98±1.16）%（P < 0.05）。LY294002处理后的G₀/G₁期细胞增加, S期明显减少, 差异有统计学意义（P < 0.05）。LY294002处理后的细胞与对照组相比P-gp和p-Akt的蛋白表达降低。  结论  LY294002能够有效的逆转卵巢癌紫杉醇耐药细胞A2780/Taxol产生的多药耐药。      

抑制PI3 K/ Akt 通路提高肺腺癌细胞化疗的 效果

 目的　探讨PI3 K/ Akt 信号转导通路抑制剂L Y294002 对肺腺癌细胞株A549 及裸鼠移植瘤化 疗的增敏作用。方法　采用MTT 法及流式细胞仪检测L Y294002 、紫杉醇、L Y294002 联合紫杉醇对 A549 细胞增殖及凋亡的影响;通过裸鼠移植瘤模型检测L Y294002 、紫杉醇、L Y294002 联合紫杉醇对 A549 细胞成瘤性的影响。结果　L Y294002 可增强紫杉醇对A549 细胞的抑制作用,并且可提高其凋亡 率。裸鼠移植瘤实验显示,L Y294002 与紫杉醇均可抑制移植瘤的生长,联用后抑瘤率增加。结论　 L Y294002 可增强紫杉醇对A549 细胞、裸鼠移植瘤的化疗的敏感性,抑制PI3 K/ Akt 信号转导通路可提 高肺腺癌化疗的效果。     

Radiation sensitization of human cancer cells in vivo by inhibiting the activity of PI3K using LY294002

Multiple genetic alterations such as in Ras or EGFR can result in sustained signaling through PI3K. Our previous experiments have shown that resistance to radiation results from PI3K activity in cells in culture. Here we examined whether inhibition of PI3K in vivo would sensitize tumors to radiation.The human bladder cancer cell line T24 has amplified and mutated H-Ras resulting in sustained PI3K activity and phosphorylation of the downstream target of PI3K, Akt. Nude mice bearing T24 tumor cell xenografts were randomly assigned to one of four groups: control, radiation alone, the PI3K inhibitor LY294002 alone, or combined LY294002 and radiation. The LY294002 was delivered intraperitoneally to the mice. Downregulation of Akt was documented by Western blot analysis of tumor lysates. In vivo sensitization was measured using clonogenic assays or regrowth assays.A dose of 100 mg/kg of LY294002, but not 50 mg/kg, consistently eliminated the phosphorylation of Akt. This inhibition was transient, and Akt activity returned after 30 min. This dose resulted in severe respiratory depression and lethargy resolving without lethality. It is not possible to tell whether these side effects of LY294002 were mechanism-based or idiosyncratic. The PI3K inhibitor LY294002 by itself had minimal antitumor effect. The combination of LY294002 and radiation resulted in significant and synergistic reduction in clonogenicity and growth delay.Inhibition of PI3K by LY294002 can synergistically enhance radiation efficacy. This acts as a proof of principle that inhibition of the Ras to PI3K pathway could be useful clinically.     

PI3K/Akt抑制剂LY294002对大肠癌细胞化疗增敏作用的探讨

目的 探讨PI3K/Akt特异性抑制剂LY294002与化疗药物联合使用对大肠癌细胞(HCT-8)化疗效果的影响.方法 将LY294002联合化疗药物作用于大肠癌细胞系HCT-8,MTT法检测单独使用5-Fu、奥沙利铂及联合PI3K抑制剂LY294002,对体外培养的大肠癌细胞系HCT-8增殖的抑制作用,流式细胞术检测HCT-8的凋亡率.结果 联合LY294002作用后,5-Fu、奥沙利铂对大肠癌细胞系HCT-8增殖的抑制作用明显增强(P<0.05),且能提高其凋亡率(P<0.05).结论 LY294002能有效提高化疗药物5-Fu、奥沙利铂体外对HCT-8细胞抑制作用的敏感性,抑制PI3K介导的信号转导通路,可明显提高大肠癌的化疗效果.     

Phosphatidylinositol 3-kinase mediates angiogenesis and vascular permeability associated with ovarian carcinoma.

PURPOSE: To assess the role of phosphatidylinositol-3 kinase (PI3K) inhibition in vascular permeability, angiogenesis, and vascular remodeling in tumor vessels and peritoneal lining in an athymic mouse model of i.p. human ovarian carcinoma. EXPERIMENTAL DESIGN: Mice were inoculated i.p. with cells from the human ovarian cancer cell line, OVCAR-3. Fourteen days after inoculation, mice were treated with or without the PI3K inhibitor LY294002, 3 days weekly for 4 weeks. At the end of the experiment, some mice were anesthetized and injected via the tail vein with FITC-labeled lycopersicon lectin and perfused through the aorta before sacrifice. The peritoneal wall and tumor from all mice were removed and embedded in 10% agarose. Tumor sections were visualized by fluorescence microscopy. RESULTS: Ascites in the LY294002-treated group (0.69 +/- 0.27 mL) was reduced by 72.4% compared with the control group (2.5 +/- 1.2 mL). Tumor burden in the LY294002-treated group (0.62 +/- 0.32 g) was reduced by 47.3% compared with the control group (1.18 +/- 0.41 g). LY294002 inhibited peritoneal and tumor vascularization resulting in numerous leaky, irregular, tortuous vessels in scant, straight, relatively impermeable vessels. CONCLUSIONS: The data indicate that LY294002 inhibits ascites formation in our mouse model of human ovarian cancer by inhibiting tumor and peritoneal neovascularization as well as vascular permeability. The data also show that LY294002 directly inhibits vascular endothelial growth factor (VEGF) protein expression and release from ovarian carcinoma and suggest that LY294002 blocks the VEGF signaling pathway involved in angiogenesis and vascular permeability.     

白花蛇舌草通过PI3K/Akt信号通路抑制人非霍奇金淋巴瘤Raji细胞增殖

目的:探讨白花蛇舌草对人非霍奇金淋巴瘤Raji细胞增殖及PI3K/Akt信号通路的影响。方法:将人非霍奇金淋巴瘤细胞Raji分为对照组、白花蛇舌草组、LY294002组、白花蛇舌草+LY294002组，采用CCK-8法检测各组Raji细胞培养12 h、24 h、48 h、72 h时细胞增殖情况，流式细胞仪检测各组细胞周期分布情况，Western blot检测培养48 h时各组细胞CyclinD1、CyclinD3、CDK4、PAK2、p-PI3K、p-Akt蛋白水平。结果:白花蛇舌草组、LY294002组、白花蛇舌草+LY294002组Raji细胞增殖抑制率随着处理时间延长而增加，在相同时间点时，白花蛇舌草+LY294002组Raji细胞增殖抑制率均高于白花蛇舌草组、LY294002组（P＜0.05）；细胞周期检测结果显示:与对照组相比，白花蛇舌草组、LY294002组、白花蛇舌草+LY294002组G0/G1期细胞比例增多、S期细胞比例降低（P＜0.05），而白花蛇舌草组、LY294002组G0/G1期、S期细胞比较差异无统计学意义（P＞0.05），白花蛇舌草+LY294002组G0/G1期、S期细胞均低于白花蛇舌草组、LY294002组（P＜0.05）；Western blot检测结果显示:白花蛇舌草组、LY294002组、白花蛇舌草+LY294002组CyclinD1、CyclinD3、CDK4、PAK2、p-PI3K、p-Akt蛋白水平均低于对照组（P＜0.05），白花蛇舌草+LY294002组CyclinD1、CyclinD3、CDK4、PAK2、p-PI3K、p-Akt蛋白水平均低于白花蛇舌草组、LY294002组（P＜0.05），白花蛇舌草组、LY294002组各种蛋白水平比较差异无统计学意义（P＞0.05）。结论:白花蛇舌草对Raji细胞增殖有抑制作用，可能与抑制PI3K/Akt信号通路活化有关。     

The PI3K/Akt inhibitor LY294002 reverses BCRP-mediated drug resistance without affecting BCRP translocation

Cellular responses toward cytotoxic drugs are influenced by crosstalk between oncogenic signals and resistance mechanisms. Inhibition of the PI3K/Akt pathway is effective in sensitizing cancer cells of various organs, although the mechanisms largely remain to be elucidated. Breast cancer resistance protein (BCRP)/ABCG2, a drug efflux pump, confers resistance to multiple anticancer agents such as SN-38 and topotecan. Previous studies reported that inhibition of the PI3K/Akt pathway, by gene knockout or PI3K inhibitors, modulated BCRP-mediated drug transport via BCRP translocation in hematopoietic stem cells, renal polarized cells and glioma stem-like cells of mammals. In this study, we assessed the effects of PI3K inhibitors, LY294002 and wortmannin, on BCRP-mediated anticancer drug resistance of human cancer MCF-7 and A431 cells. LY294002, but not wortmannin, reversed the BCRP-mediated SN-38 and topotecan resistance. LY294002 treatment did not affect total or cell surface BCRP levels as determined by western blotting and flow cytometry but blocked BCRP-mediated topotecan efflux in a dose-dependent manner. Immunohistochemical analyses also demonstrated unchanged cellular BCRP distribution. BCRP overexpression in MCF-7 and A431 cells did not confer LY294002 resistance, suggesting that LY294002 is not a transported substrate of BCRP. LY294002 is a derivative of quercetin, a member of flavonoids. Taken together, these results suggest that LY294002 inhibits BCRP-mediated drug transport not by BCRP translocation through the PI3K/Akt signal but putatively as a competitive inhibitor in a major subset of cancer cells. Due to its dual effects, LY294002 could be a lead compound for developing more effective and tolerable reagents for cancer treatment.