PI3K/Akt信号通路抑制剂对人胃癌细胞增殖及相关基因表达的影响

目的 研究磷脂酰肌醇-3-激酶/蛋白激酶B(PI3K/Akt)信号通路抑制剂渥曼青霉素对人胃癌细胞增殖、细胞周期与凋亡的影响以及相关基因蛋白激酶B(pAkt)、磷酸化腺苷酸活化蛋白激酶(pAMPK)、S期激酶相关蛋白2(Skp2)及P27kip1蛋白表达的影响.方法 分别用不同浓度渥曼青霉素处理处于对数生长阶段的BGC823细胞12、24、48 h,利用MTT实验检测其对胃癌细胞增殖的影响,胃癌细胞凋亡及细胞周期的检测采用流式细胞术,Western-blotting检测p-Akt、p-AMPK、Skp2及P27kip1蛋白的表达变化.结果 渥曼青霉素可明显抑制BGC823细胞的增殖,在一定范围内具有时间和浓度依赖性.20 mmol/L渥曼青霉素作用细胞24 h时,细胞生长周期阻滞于G0/G1期,细胞凋亡率为(44.44±3.17)％;Western blot检测显示,pAkt、pAMPK及Skp2蛋白表达随着药物浓度的增加而减少,P27kip1蛋白表达随着药物浓度增加而增加.结论 PI3K/Akt信号通路抑制剂渥曼青霉素能够明显下调胃癌细胞的增殖活性,导致胃癌细胞周期被阻滞于G0/G1期并诱导细胞发生凋亡,进一步研究证实PI3K/Akt信号通路介导的Skp2及P27kip1蛋白调控在凋亡过程中发挥重要作用.     

LY294002对多药耐药急性白血病细胞株HL60/VCR的凋亡及细胞周期的影响研究

目的:研究磷脂酰肌醇-3-激酶(PI3K)抑制剂LY294002对多药耐药急性白血病细胞株HL60/VCR凋亡与细胞周期的影响及可能机制。方法:取耐长春新碱(VCR)的HL60/VCR多药耐药急性白血病细胞株分为未加药的对照组及加入不同浓度的LY294002(其终浓度为1.0、2.5、5.0、10μmol.L-1)组,MTT法检测2种细胞的半数抑制浓度(IC50),流式细胞仪检测细胞凋亡及细胞周期分布,半定量逆转录-聚合酶链反应(RT-PCR)检测抗凋亡蛋白Bcl-2、细胞周期调控分子CyclinD1mRNA表达。结果:与对照组比较,LY294002可明显降低HL60/VCR对VCR的IC50(P<0.05),且与剂量相关;LY294002可显著增加HL60/VCR细胞凋亡率,阻滞细胞于G0/G1期,降低HL60/VCR细胞的Bcl-2、CyclinD1mRNA的表达(P均<0.05)。结论:LY294002可能是通过影响Bcl-2及CyclinD1基因的表达,从而促进HL60/VCR细胞凋亡及抑制细胞增殖。     

1,25二羟维生素D_3对卵巢癌细胞株HO8910增殖及Skp_2/p27蛋白表达的影响

目的:观察1,25二羟维生素D3[1,25(OH)2D3]对人卵巢癌细胞株HO8910增殖的影响,并且检测其作用下S期激酶相关蛋白(Skp2)、抑癌基因p27的蛋白表达情况,以探讨其作用机制。方法:选用人卵巢癌细胞株HO8910进行体外培养,用MTT比色法测定不同浓度D3[1,25(OH)2D3]对细胞株作用不同时间后细胞生长抑制率,流式细胞仪进行细胞周期分析,免疫细胞化学染色检测Skp2及p27蛋白表达情况。结果:1,25(OH)2D3在160×10-9mol/L以上时,对细胞有抑制作用(P<0.05),且呈浓度时间依赖性;1,25(OH)2D3能增加G0/G1期细胞比例,降低S、G2/M期细胞比例,从而降低细胞增殖指数(P<0.01);能降低Skp2表达,增加p27蛋白表达(P<0.01)。结论:1,25(OH)2D3对人卵巢癌细胞株HO8910有抑制作用,可能通过下调Skp2表达、上调p27蛋白表达,从而抑制癌细胞增殖。     

羟基红花黄色素A对氧化低密度脂蛋白诱导的血管平滑肌细胞增殖的抑制作用

目的探讨羟基红花黄色素A(HSYA)抑制氧化低密度脂蛋白(ox-LDL)诱导血管平滑肌细胞(VSMC)增殖与细胞外信号调节激酶1/2(ERK1/2)和丝裂原活化蛋白激酶磷酯酶-1(MKP-1)基因转录及蛋白表达之间的关系。方法 HSYA 10μmol.L-1和ox-LDL 35 mg.L-1与VSMC共培育48 h,MTT检测细胞存活率,流式细胞术检测细胞周期,逆转录PCR(RT-PCR)观察ERK1/2和MKP-1基因表达,Western印迹法观察ERK1/2和MKP-1蛋白表达。结果与ox-LDL 35 mg.L-1模型组比较,加入HSYA 10μmol.L-1组细胞存活率明显下降,G0/G1期细胞明显增多,ERK1 mRNA表达下降了42.2%(P<0.01),MKP-1 mRNA显著增加了86.9%(P<0.01),p-ERK1/2蛋白表达降低了39.9%(P<0.01),MKP-1蛋白表达增加了80.6%(P<0.01);加入PD98059 10μmol.L-1组,细胞存活率明显降低了58.3%(P<0.01),G0/G1期细胞明显增多(P<0.01),ERK1 mRNA表达下降了45.9%(P<0.01);p-ERK1/2蛋白表达下降了45.9%(P<0.01);PD98059 10μmol.L-1+HSYA 10μmol.L-1同时加入,细胞生存率下降了61.9%(P<0.01),G0/G1期细胞明显增多(P<0.01),ERK1 mRNA表达进一步减少(P<0.01),MKP-1 mRNA增加了110%(P<0.01),p-ERK1/2蛋白表达下降了51.2%(P<0.01),MKP-1蛋白表达增加了62.4%(P<0.01)。结论 HSYA通过增强MKP-1蛋白表达、降低p-ERK1/2蛋白活性和抑制细胞周期运转的机制抑制VSMC增殖。     

欧前胡素调节MAPK/mTOR/p70S6K信号通路对急性髓系白血病细胞恶性生物学行为的影响

目的 探讨欧前胡素(IMP)对急性髓系白血病(AML)细胞恶性生物学行为的影响以及对MAPK/mTOR/p70S6K信号通路的调节机制。方法 将人AML细胞HL-60进行培养传代,并分为对照组(未处理组),ERK抑制剂组(PD98059组),IMP低、中、高剂量组,IMP高剂量+ERK激活剂组(IMP高+Cearoin组),每组均设置6个重复。MTT法检测IMP对HL-60细胞的毒性;MTT法、软琼脂克隆形成实验检测HL-60细胞的增殖活性;流式细胞仪术检测HL-60细胞凋亡;Transwell小室检测HL-60细胞迁移和侵袭能力;ELISA检测HL-60细胞培养液中TNF-α、IL-1β、IL-6的水平;Western blot检测通路相关蛋白及Bcl-2、Beclin-1、LC3Ⅱ/Ⅰ蛋白的表达。结果 与未处理组比较,PD98059组和IMP低、中、高剂量组HL-60细胞的存活率、克隆形成数量、迁移和侵袭数量、促炎因子TNF-α、IL-1β、IL-6水平以及ERK1/2、mTOR、p70S6K磷酸化水平、Bcl-2表达显著降低(P<0.05),细胞凋亡率、自噬相关蛋白Becl...     

ERK1/2信号通路在角质细胞生长因子-2诱导角膜基质细胞增殖中的作用

目的观察角质细胞生长因子(keratinocyte growthfactor-2,KGF-2)对角膜基质细胞的增殖作用及ERK1/2信号在角膜基质细胞增殖中的调控作用,探讨KGF-2对角膜基质细胞增殖的可能机制。方法体外培养角膜基质细胞,MTT法检测细胞增殖,Western blot检测磷酸化ERK1/2表达水平。结果 KGF-2在1～100 mg·L-1对角膜基质细胞有明显的促进增殖作用且呈现剂量-效应关系;100 mg·L-1 KGF-2处理角膜基质细胞,5、15、30 min后ERK1/2磷酸化表达水平明显升高,60、90、120、180 min后ERK1/2磷酸化表达水平逐渐减弱;20μmol.L-1 ERK1/2抑制剂PD98059可抑制KGF-2对角膜基质细胞的促增殖作用。结论 KGF-2激活ERK1/2信号通路,提高细胞增殖率,可被抑制剂PD98059阻断;ERK1/2信号通路调控角膜基质细胞的增殖,在角膜基质细胞损伤中发挥作用。     

ERK1/2信号通路在3种骨肉瘤细胞中的作用和表达水平的研究

目的 观察细胞外调节蛋白激酶(ERK1/2)激动剂表皮生长因子(EGF)和抑制剂PD98059对3种骨肉瘤细胞株U2OS、MG63、UMR106的增殖影响以及ERK1/2基因和蛋白在3种细胞株中的表达水平，筛选出ERK1/2基因和蛋白表达最高的骨肉瘤细胞株用于后续实验研究。方法 采用细胞计数和CCK8法分别测定U2OS、MG63、UMR106细胞的生长情况，同时使用EGF和PD98059分别干预3种细胞株，观察其对3种骨肉瘤细胞增殖的影响；采用实时荧光定量PCR(RT-qPCR)检测3种细胞株中ERK1/2基因的表达；采用Western-blot检测3种细胞株中ERK1/2蛋白、p-ERK1/2蛋白的表达情况。结果 细胞计数和CCK8结果均显示，U2OS和UMR106在正常情况下培养48 h可达最佳生长状态，而MG63细胞的最佳生长状态时间为24 h; EGF在干预细胞24 h和48 h均能使U2OS、MG63、UMR106细胞增殖，而PD98059在干预细胞24 h和48 h均能使3种细胞的增殖受到抑制(P<0.05)。RT-qPCR结果显示在培养48 h后，U2OS细胞中的E...     

Endothelin—1 promoted proliferation of vascular smooth muscle cell through pathway of extracellular signal—regulated kinase and cyclin D1

目的:探讨内皮素-1是否通过细胞周期蛋白质D1与细胞外调节蛋白激酶通路促进人脐动脉平滑肌细胞增殖。方法:采用MTT法观察ET-1和PD98059对人脐动脉平滑肌细胞生长的作用;[~3H]TdR法观察对细胞DNA合成的作用;流式细胞仪法观察对细胞增殖周期的影响;蛋白质印迹法观察对细胞外调节蛋白激酶和细胞周期蛋白质D1表达的影响。结果:首先,同没有ET-1组和PD98059组比较,ET-1促进平滑肌细胞增殖(P<0.05)。PD98059抑制ET-1诱导的血管平滑肌细胞增殖。第二,与没有ET-1组比较,ET-1促进平滑肌细胞DNA合成(P<0.05)。第三,ET-1促进平滑肌细胞增殖周期从G_0/G_1期向S期的转变,与没有ET-1组比较,G_0/G_1期细胞百分比明显减少,S期细胞百分比明显增加(P<0.05)。第四,ET-1增加细胞外信号调节性激酶的磷酸化水平和细胞周期蛋白质D1的蛋白表达,ERK的抑制剂可以抑制细胞外信号调节性激酶的磷酸化水平和细胞周期蛋白质D1的蛋白表达,与没有ET-1组比较,磷酸化-ERK和细胞周期蛋白质D1表达明显增强,对非磷酸化ERK表达没有影响。结论:内皮素-1可以通过细胞周期调节素D1与细胞外信号调节性激酶通路促进平滑肌细胞增殖。     

MEK抑制剂联合三氧化二砷对髓系白血病细胞凋亡的研究

目的:研究MEK抑制剂PD98059联合三氧化二砷(As2O3)对髓系白血病细胞凋亡的影响及其作用机制。方法:将PD98059、As2O3单独或联合作用于髓系白血病细胞系HL-60、K562细胞,用AnnexinV-FITC法检测细胞凋亡,用流式细胞术检测Bcl-2、Caspapse-3表达。结果:联合组与单用组相比,细胞凋亡率明显增高。Bcl-2在HL-60、K562细胞均高水平表达。As2O3明显抑制HL-60细胞Bcl-2表达,对K562细胞Bcl-2无明显抑制作用。单用PD98059、As2O3及两药合用在诱导HL-60、K562细胞凋亡过程中,活化caspapse-3均明显上升,两药合用较单用PD98059或As2O3活化caspapse-3明显升高。结论:PD98059联合As2O3同时抑制ERK/MAPK和Bcl-2,激活Caspase酶,对HL-60细胞有协同促凋亡效应。两药联合同时靶向作用ERK/MAPK和BCR/ABL,活化Caspase酶,协同诱导K562细胞凋亡。PD98059可增强As2O3对髓系白血病细胞的凋亡诱导作用。     

PD98059联合紫杉醇对人胃印戒细胞癌细胞增殖和凋亡的影响

目的:探讨丝裂原激活蛋白激酶激酶/细胞外信号调节激酶(MEK/ERK)通路特异性抑制剂PD98059联合紫杉醇对人胃印戒细胞癌细胞增殖和凋亡的影响。方法:以人胃印戒细胞癌KATOⅢ细胞为对象,采用CCK-8法检测紫杉醇、PD98059以及两药联合作用48 h后的细胞增殖情况,并计算增殖抑制率;采用流式细胞术、Western blotting、Transwell法分别检测紫杉醇、PD98059以及两药联合作用48 h或24 h后的细胞凋亡、凋亡相关蛋白[分裂型胱天蛋白酶3(Cleaved-caspase-3)]表达和细胞迁移情况。结果:经紫杉醇(1μg/mL)、PD98059(5、20、40μmol/L)以及两药(1μg/mL+5、20、40μmol/L)联合作用后,各给药组细胞的增殖抑制率均显著升高,且联用组显著高于紫杉醇、PD98059同剂量单用组(P<0.05)。经紫杉醇(1μg/mL)、PD98059(40μmol/L)以及两药(1μg/mL+40μmol/L)联合作用后,紫杉醇组和两药联用组细胞的早期、晚期凋亡率以及Cleave-caspased-3蛋白的表达量均显著升高,且联用组显著高于紫杉醇、PD98059单用组(P<0.05);各给药组的细胞迁移数均显著减少,且联用组显著少于紫杉醇、PD98059单用组(P<0.05)。结论:紫杉醇、PD98059均可抑制人胃印戒细胞癌KATOⅢ细胞的增殖和迁移,且紫杉醇还可促进该细胞的凋亡及凋亡相关蛋白的表达,上述作用可能与抑制MEK/ERK通路有关。两药联用的效果优于紫杉醇或PD98059单用。     

Magnolol elicits activation of the extracellular signal-regulated kinase pathway by inducing p27KIP1-mediated G2/M-phase cell cycle arrest in human urinary bladder cancer 5637 cells

Magnolol has been reported to play a role in antitumor activity. However, the relevant pathway integrating cell cycle regulation and signaling pathways involved in growth inhibition in cancer cells remains to be identified. In the present study, magnolol treatment of these cells resulted in significant dose-dependent growth inhibition together with apoptosis, G1- and G2/M-phase cell cycle arrest at a 60 microM (IC50) dose in 5637 bladder cancer cells. In addition, magnolol treatment strongly induced p27KIP1 expression, and down-regulated expression of cyclin-dependent kinases (CDKs) and cyclins. Moreover, treatment with magnolol-induced phosphorylation of ERK, p38 MAP kinase, and JNK. Among the pathway inhibitors examined, only PD98059, an ERK-specific inhibitor, blocked magnolol-dependent p27KIP1 expression. Blockade of ERK function consistently reversed magnolol-mediated inhibition of cell proliferation and decreased G2/M cell cycle proteins, but not G1 cell cycle proteins. Furthermore, magnolol treatment increased both Ras and Raf activation. Transfection of cells with dominant negative Ras (RasN17) and Raf (RafS621A) mutant genes suppressed magnolol-induced ERK activity and p27KIP1 expression. Finally, the magnolol-induced reduction in cell proliferation and G2/M cell cycle proteins was also abolished in the presence of RasN17 and RafS621A mutant genes. These data demonstrate that the Ras/Raf/ERK pathway participates in p27KIP1 induction, leading to a decrease in the levels of cyclin B1/Cdc2 complexes and magnolol-dependent inhibition of cell growth. Overall, these novel findings concerning the molecular mechanisms of magnolol in 5637 bladder cancer cells provide a theoretical basis for therapeutic treatment of malignancies.     

Euphol from Euphorbia tirucalli selectively inhibits human gastric cancer cell growth through the induction of ERK1/2-mediated apoptosis

Gastric cancer is one of the most common malignancies worldwide, and the main cause of cancer-related death in Asia. The present study assessed the anticancer effects of euphol, a triterpene alcohol with anti-inflammatory and antiviral activities on human gastric cancer cells. Euphol showed higher cytotoxicity activity against human gastric CS12 cancer cells than against noncancer CSN cells. In addition, it up-regulated the pro-apoptotic protein BAX and down-regulated the prosurvival protein Bcl-2, causing mitochondrial dysfunction, possibly by caspase-3 activation. The anti-proliferative effects of euphol were associated with the increased p27^kip1 levels and decreased cyclin B1 levels. Inhibition of ERK1/2 activation by PD98059 reversed euphol-induced pro-apoptotic protein expression and cell death. Taken together, these findings suggest that euphol selectively induced gastric cancer cells apoptosis by modulation of ERK signaling, and could thus be of value for cancer therapy.     

Implication of NAG-1 in synergistic induction of apoptosis by combined treatment of sodium salicylate and PI3K/MEK1/2 inhibitors in A549 human lung adenocarcinoma cells

Aspirin is used as chemopreventive agents in a variety of human cancer cells including those of colon, lung, breast, and leukemia. Sodium salicylate (NaSal, the natural deacetylated form of aspirin) induced cell cycle arrest and apoptosis in a dose-dependent manner in A549 cells; high dose (20mM) of NaSal-induced apoptosis, whereas low dose (2-10mM) induced cell cycle arrest. We found that NaSal-activated Akt/PKB, ERK1/2, and p38MAPK signal cascades. Twenty micromolar of NaSal-induced apoptotic response of A549 cells was enhanced by the PI3K inhibitors (LY294002 and wortmannin) and in a less extent by the MEK1/2 inhibitors (U0126 and PD98059), whereas it was suppressed by the p38MAPK inhibitor (SB203580). Furthermore, simultaneous inhibition of the Akt/PKB and ERK1/2 signal cascades could lower the dose of NaSal to induce apoptosis to 2mM in A549 lung cancer cells. Similar enhancement was observed in cells treated with 2mM NaSal and 100muM genistein, an inhibitor of receptor tyrosine kinases (RTKs) that are upstream of PI3K and MEK1/2 signaling. We further demonstrated that NAG-1 plays a key role in apoptosis by NaSal-based combined treatment. Collectively, our findings indicate that inhibition of the pro-survival Akt/PKB and ERK1/2 signaling may increase the chemopreventive effects of NaSal and combined treatment of two natural compounds (NaSal and genistein) results in a highly synergistic induction of apoptosis, thereby increasing the chemopreventive effects of NaSal against cancer.     

Inhibition of ERK and activation of p38 are involved in diallyl disulfide induced apoptosis of leukemia HL-60 cells

We investigated the effects of diallyl disulfide (DADS) on the induction of apoptosis in human Leukemia cell line HL-60 and explored the roles of mitogen-activated protein kinase (ERK and p38 MAPK) pathways in the growth inhibition and apoptosis induced by DADS. MTT assay was used to determine the DADS induced cell growth inhibition in HL-60 cells. Flow cytometry and DNA fragmentation were used to examine the roles of apoptosis in DADS-mediated cell death. Western blot analysis of the expression of phospho-MAPKs (ERK and p38) was employed to elucidate the possible mechanisms of DADS induced apoptosis. We found that growth inhibition of HL-60 cells treated with DADS exhibited a dose-dependent response (P<0.05) and DADS induced significant apoptosis. DADS at the concentration of 10 mg/L persistently activated p38 and simultaneously reduced ERK activity. PD98059, an inhibitor of ERK upstream activators MAPK kinase MKK1 and MKK2, promoted cytotoxicity and apoptosis in HL-60 cells treated with DADS. In contrast, SB203580, an inhibitor of p38, decreased cytotoxicity and apoptosis induced by DADS. Therefore, DADS can effectively inhibit the proliferation and induce apoptosis of human leukemia cell line HL-60. Inhibition of ERK signaling pathways and activation of p38 signaling pathways are likely involved in DADS induced apoptosis in HL-60 cells.     

Fluoride-induced apoptosis in epithelial lung cells involves activation of MAP kinases p38 and possibly JNK.

Exposure to fluorides can induce inflammatory reactions, cell cycle arrest, and apoptosis in different experimental systems. Fluorides are known G-protein activators, but less is known about fluoride effects downstream of G-protein activation. The aim of this study was to elucidate whether the induction of apoptosis by fluorides and inhibition of proliferation is mediated by MAP kinases in primary rat lung, alveolar type 2 cells and the human epithelial lung cell line A549. Sodium fluoride (NaF) induced apoptosis in both cell types but at different concentrations, with the primary cells being more sensitive to NAF: Proliferation of the type 2 cells and A549 cells was inhibited in the presence of NAF: NaF induced a prolonged activation of MAP kinase ERK. NaF also activated p38 and JNK in A549 cells for several hours (maximally 6-fold and 3-fold increase, respectively). Inhibition of ERK with the MEK1,2 inhibitor PD98059 increased apoptosis 2-fold, whereas the inhibitor of p38, SB202190, decreased the level of apoptotic cells by approximately 40%. SB202190 also inhibited apoptosis by almost 40% when ERK activity was reduced in the presence of PD98059. Neither PD98059 nor SB202190 did affect the NaF-induced inhibition of proliferation. These observations indicate that activation of MAP kinases p38 and possibly JNK are involved in NaF-induced apoptosis of epithelial lung cells, whereas ERK activation seems to counteract apoptosis in epithelial lung cells. In contrast, activation of ERK and p38 are not involved in NaF-induced inhibition of cell proliferation.     

Contribution of extracellular signal-regulated kinases to the IL-1-induced growth inhibition of human melanoma cells A375

The role of ERK1/2 in the IL-1-induced growth inhibition was investigated using human melanoma A375-6 cells. A selective inhibitor of ERK1/2 pathway, PD98059 and a selective inhibitor of p38MAPK, SB203580 each alone significantly reversed the IL-1-induced growth inhibition of A375-6 cells. Co-treatment with PD98059 and SB203580 completely reversed the IL-1-induced growth inhibition. ERK1/2 was constitutively activated in A375-6 cells, and IL-1 further augmented ERK activation. Antiproliferative effect of IL-1 was attenuated by the expression of dominant negative form of ERK2. IL-1 induced cell cycle arrest in G(0)/G(1) phase, expression of p21 and p27 proteins, and down-regulation of cyclin D/cyclin-dependent kinase (CDK) 2 and CDK4 activities. These effects of IL-1 were reversed by PD98059. PD98059 also reversed the IL-1-induced hypophosphorylation of RB protein (pRB) and down-regulation of E2F activity. These findings demonstrate that ERK1/2 contribute to the IL-1-induced growth inhibition through induction of CDK inhibitors, down-regulation of CDK activity, pRB phosphorylation and E2F activity.     

PINK1/Parkin-mediated mitophagy is involved in NaAsO2-induced apoptosis of human hepatic cells through activation of ERK signaling

Mitochondrial dysfunction has been demonstrated as one key event in arsenic-induced hepatic cell damage though the exact molecular target remains unknown. Here we examined NaAsO₂-induced mitochondrial damage in the L-02 cell led to mitochondrial depolarization and cytochrome c release, mitophagy, apoptosis in a dose response manner. Mitophagy was measured by analysis of PINK1, Parkin, LC3-II and p62 protein. Apoptosis was assessed by measuring Annexin V. Using the mitophagy inhibitor cyclosporine A (CsA) or ERK inhibitor (PD98059), the balance between mitophagy and apoptosis were further explored. When CsA was used prior to cell exposure to NaAsO₂, it was found that the levels of mitophagy were decreased as expected and apoptosis was increased in response. CsA alone had no effect on the apoptosis rate. When the ERK signaling inhibitor PD98059 was used, there was a similar result that mitophagy was reduced though in contrast with CsA the apoptosis rate was also decreased compared with NaAsO₂ alone. This result, along with the increased levels of ERK measured here in response to NaAsO₂, indicates that ERK activation is a second key molecular response to NaAsO₂ through the activation of both apoptosis and mitophagy. Thus the results with CsA indicate that the likely key biological event in NaAsO₂ toxicity is at the level of the mitochondria leading to cytochrome c release and apoptosis. Mitophagy is increased in response to a secondary effect of NaAsO₂ on ERK signaling that activates both mitophagy and apoptosis. The activation of mitophagy allows the cell to avoid some apoptosis. When ERK signaling is inhibited by PD98059 both the levels of apoptosis and mitophagy are decreased compared with the response produced by NaAsO₂ alone in comparison to the inhibition of mitophagy by CsA that reduced mitophagy but dramatically increased apoptosis in response.     

PD98059 triggers G1 arrest and apoptosis in human leukemic U937 cells through downregulation of Akt signal pathway

MEK/ERK pathways are frequently activated in acute myelogenous leukemia, and this signal pathway's inhibitor has made it an interesting candidate for cancer chemotherapy. Little is known, however, about the effects of cellular and molecular mechanisms on human leukemic U937 cells. In the present study, we found that treatment with PD98059 significantly arrests the G1 phase through up-regulation of cyclin-dependent kinase (Cdk) inhibitor, and produces morphological features of apoptosis in U937 cells, which were associated with poly(ADP-ribose)polymerase (PARP) cleavage and PLC-gamma1 degradation. PD98059 also decreased the Cdk-2, Cdk-4, cyclin D1, and cyclin E expression, and increased high levels of the mitotic inhibitors p16(INIa), p21(Waf1), and p27(Kip1). Also, Bcl-2's overexpression and a caspase-3 inhibitor z-DEVD-fmk significantly attenuated PD98059-induced apoptosis through the down-regulation of caspase-3 activity, but did not attenuate G1 phase arrest. Moreover, PD98059 down-regulated Akt phosphorylation and produced a synergy effect of apoptosis with LY294002 co-treatment. Thus, our results imply that PD98059-induced apoptosis is significantly involved in down-regulation of Bcl-2, caspase-3 activity, the Akt pathway, and some of the biological functions in U937 cells.