分泌型卷曲相关蛋白 1通过 MAPK/ERK信号通路抑制结直肠癌细胞的迁移侵袭

目的探讨分泌型卷曲相关蛋白 1(SFRP1)对结直肠癌细胞迁移和侵袭的影响机制。方法本研究起止时间 2018年 11月至 2019年 6月。运用实时荧光定量反转录聚合酶链反应( qRT-PCR)检测正常结肠上皮细胞 HCoEpiC、人结直肠癌细胞 HCT8、SW480、RKO中 SFRP1的 mRNA表达;将 pcDNA 3.1组(转染 pcDNA 3.1)pcDNA 3.1-SFRP1组(转染 pcDNA 3.1-SFRP1)、 pcDNA 3.1-SFRP1+DMSO组［转染 pcDNA 3.1-SFRP1,再用二甲基亚砜( DMSO)处、理］、 pcDNA 3.1-SFRP1+IGF组［转染 pcDNA 3.1-SFRP1,再用丝裂原活化蛋白激酶( MAPK)/细胞外信号调节激酶( ERK)信号通路激活剂( IGF1)处理］均用脂质体法转染至 HCT8细胞。蛋白质印迹法( Western blotting)检测细胞中 SFRP1、波形蛋白(Vimentin)、纤维黏连蛋白(FN)、,基质金属蛋白酶 9(MMP-9)、 N-钙黏蛋白( N-cadherin)、上皮钙黏蛋白( E-cadherin)、 MAPK/ERK信号通路关键基因( Ras)、雷帕霉素靶蛋白(mTOR)、细胞外信号调节激酶 1/2(ERK1/2)、磷酸化细胞外信号调节激酶 1/2(p-ERK1/2)、细胞外信号调节激酶( ERK)的蛋白表达;迁徙实验( Transwell)检测细胞的迁移侵袭。结果与正常结肠上皮细胞 HCoEpiC相比,人结直肠癌细胞 HCT8、SW480、 RKO中 SFRP1的表达显著降低［mRNA(1.00±0.06)比( 0.36±0.03)、(0.62±0.05)、(0.59±0.05);蛋白( 1.00±0.04)比( 0.24±0.02)、(0.48±0.04)、(0.47±0.04)均 P<0.05］。过表达 SFRP1可抑制 HCT8细胞的迁移( 120±11)比( 65±6)和侵袭( 98±8)比( 47±4)并下调Vimentin(0.96±0.05)比,(0.23±0.02)、FN(1.00±0.07)比(0.51±0.04)、MMP-9(0.98±0.08)比(0.35±0.03)、N-cadherin(1.01±0.09)比(0.43±0.04)上调 E-cadherin(0.99±0.06)比( 3.71±0.27)抑制 MAPK/ERK信号通路关键蛋白 Ras(0.97±0.07)比( 0.34±0.03)、mTOR(1.03±0.07)比(0.42±0.04)、 p-ERK1/2(0.98±0.08)比(0.29±0.03)和 ERK(1.01±0.06)比( 0.31±0.03)的表达。激活 MAPK/ERK信号通路可逆转过表达 SFRP1对结直肠癌细胞迁移和侵袭的抑制作用。结论 SFRP1可抑制结直肠癌细胞的迁移和侵袭,其机制可能与失活 MAPK/ERK信号通路相关,将可为 SFRP1用于结直肠癌的治疗提供依据。     

Adenosine dialdehyde suppresses MMP-9-mediated invasion of cancer cells by blocking the Ras/Raf-1/ERK/AP-1 signaling pathway

Adenosine dialdehyde (AdOx) inhibits transmethylation by the accumulation of S-adenosylhomocysteine (SAH), a negative feedback inhibitor of methylation, through the suppression of SAH hydrolase (SAHH). In this study, we aimed to determine the regulatory effect of AdOx on cancer invasion by using three different cell lines: MDA-MB-231, MCF-7, and U87. The invasive capacity of these cells in the presence (MCF-7) or absence (MDA-MB-231 and U87) of phorbal 12-myristate 13-acetate (PMA) was strongly decreased by AdOx treatment. Furthermore, the expression, secretion, and activation of matrix metalloproteinase (MMP)-9, a critical enzyme regulating cell invasion, in these cells were diminished by AdOx treatment. AdOx strongly suppressed AP-1-mediated luciferase activity and, in parallel, reduced the translocation of c-Fos and c-Jun into the nucleus. AdOx was shown to block a series of upstream AP-1 activation signaling complexes composed of extracellular signal-related kinase (ERK), mitogen-activated protein ERK kinase (MEK)1/2, Raf-1, and Ras, as assessed by measuring the levels of the phosphorylated and membrane-translocated forms. Furthermore, we found that suppression of SAHH by siRNA and 3-deazaadenosine, knock down of isoprenylcysteine carboxyl methyltransferase (ICMT), and treatment with SAH showed inhibitory patterns similar to those of AdOx. Therefore, our data suggest that AdOx is capable of targeting the methylation reaction regulated by SAHH and ICMT and subsequently downregulating MMP-9 expression and decreasing invasion of cancer cells through inhibition of the Ras/Raf-1/ERK/AP-1 pathway.     

Kaempferol induces chondrogenesis in ATDC5 cells through activation of ERK/BMP-2 signaling pathway

Endochondral bone formation occurs when mesenchymal cells condense to differentiate into chondrocytes, the primary cell types of cartilage. The aim of the present study was to identify novel factors regulating chondrogenesis. We investigated whether kaempferol induces chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Kaempferol treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. Kaempferol-treated ATDC5 cells stained more intensely with alcian blue staining than control cells, suggesting greater synthesis of matrix proteoglycans in the kaempferol-treated cells. Similarly, kaempferol induced greater activation of alkaline phosphatase activity than control cells, and it enhanced the expression of chondrogenic marker genes, such as collagen type I, collagen type X, OCN, Runx2, and Sox9. Kaempferol induced an acute activation of extracellular signal-regulated kinase (ERK) but not c-jun N-terminal kinase or p38 MAP kinase. PD98059, an inhibitor of MAPK/ERK, decreased in stained cells treated with kaempferol. Furthermore, kaempferol greatly expressed the protein and mRNA levels of BMP-2, suggesting chondrogenesis was stimulated via a BMP-2 pathway. Taken together, our results suggest that kaempferol has chondromodulating effects via an ERK/BMP-2 signaling pathway and could potentially be used as a therapeutic agent for bone growth disorders.     

Rapid activation of ERK1/2 and AKT in human breast cancer cells by cadmium

Cadmium (Cd), an endocrine disruptor, can induce a variety of signaling events including the activation of ERK1/2 and AKT. In this study, the involvement of estrogen receptors (ER) in these events was evaluated in three human breast cancer cell lines, MCF-7, MDA-MB-231, and SK-BR-3. The Cd-induced signal activation patterns in the three cell lines mimicked those exhibited in response to 17 beta-estradiol. Specifically, treatment of MCF-7 cells, that express ER alpha, ER beta and GPR30, to 0.5-10 microM Cd for only 2.5 min resulted in transient phosphorylation of ERK1/2. Cd also triggered a gradual increase and sustained activation of AKT during the 60 min treatment period. In SK-BR-3 cells, that express only GPR30, Cd also caused a transient activation of ERK1/2, but not of AKT. In contrast, in MDA-MB-231 cells, that express only ER beta, Cd was unable to cause rapid activation of either ERK1/2 or AKT. A transient phosphorylation of ER alpha was also observed within 2.5 min of Cd exposure in the MCF-7 cells. While the estrogen receptor antagonist, ICI 182,780, did not prevent the effect of Cd on these signals, specific siRNA against hER alpha significantly reduced Cd-induced activation of ERK1/2 and completely blocked the activation of AKT. It is concluded that Cd, like estradiol, can cause rapid activation of ERK1/2 and AKT and that these signaling events are mediated by possible interaction with membrane ER alpha and GPR30, but not ER beta.     

ERK1/2 activation attenuates TRAIL-induced apoptosis through the regulation of mitochondria-dependent pathway.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) functions as an extracellular signal, which triggers apoptosis in tumor cells. In order to characterize the molecular events involved in TRAIL cytotoxic signaling, we attempted to determine the role of extracellular signal-regulated kinase 1/2 (ERK1/2), as well as its downstream targets in TRAIL-treated HeLa cells. Here we demonstrate that TRAIL exposure resulted in the activation of ERK1/2, and the elevation of anti-apoptotic Bcl-2 protein levels. ERK1/2 inhibition with PD98059 promoted cell death via the down-regulation of Bcl-2 protein levels, together with increasing mitochondrial damage, including the collapse of mitochondrial membrane potential, the release of cytochrome c from mitochondria to cytoplasm and caspase activity. These results suggest that the ERK1/2 activation is a kind of survival mechanism to struggle against TRAIL-induced stress condition in early stage, via activating cellular defense mechanisms like as the up-regulation of the Bcl-2/Bax ratio, as well as several mitochondrial events.     

Rubus idaeus extract suppresses migration and invasion of human oral cancer by inhibiting MMP‐2 through modulation of the Erk1/2 signaling pathway

Raspberries (Rubus idaeus L.) have been extensively studies worldwide because of their beneficial effects on health. Recently reports indicate that crude extracts of Rubus idaeus (RIE) have antioxidant and anticancer ability. The aim of this study was to evaluate the mechanism of its antimetastatic ability in oral cancer cells. In this study, SCC‐9 and SAS oral cancer cells were subjected to a treatment with RIE and then analyzed the effect of RIE on migration and invasion. The addition of RIE inhibited the migration and invasion ability of oral cancer cells. Real time PCR, western blot and zymography analysis demonstrated that mRNA, protein expression and enzyme activity of matrix metalloproteinases‐2 (MMP‐2) were down‐regulated by RIE. Moreover, the phosphorylation of Focal adhesion kinase (FAK), src, and extracellular signal‐regulated kinase (ERK) were inhibited after RIE treatment. In conclusion, these results demonstrated that RIE exerted an inhibitory effect of migration and invasion in oral cancer cells and alter metastasis by suppression of MMP‐2 expression through FAK/Scr/ERK signaling pathway. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1037–1046, 2017.     

凝血酶通过AP-1信号途径刺激人肾小球系膜细胞表达MMP-9 mRNA(英文)

目的:利用体外培养人肾小球系膜细胞观察凝血酶对系膜细胞表达MMP-9 mRNA的诱导作用及其可能的细胞内信号传导机制。方法:体外分离并培养人肾小球系膜细胞,以不同浓度凝血酶(500,1500和4500u/L)刺激后采用Northern杂交及凝胶阻滞试验(EMSA)分别观察MMP-9 mRNA表达水平及转录因子AP-1活性变化;同时观察了凝血酶特异性抑活物(水蛭素)、AP-1药理阻断剂(curcumin)和c-fos反义寡核苷酸对凝血酶上述作用的影响。结果:Northern分析表明凝血酶可以剂量依赖性地提高人系膜细胞表达MMP-9 mRNA,与对照组相比,分别提高1.1,3.3和4.8倍;EMSA实验结果发现凝血酶在促进MMP-9 mRNA表达的同时,系膜细胞AP-1的结合能力也相应地提高,与对照组相比分别增加2.5,4.9和6.1倍,与MMP-9 mRNA呈平行性变化;凝血酶抑活物水蛭素可明显地抑制凝血酶上调MMP-9mRNA及AP-1的DNA结合活性;同时AP-1药理阻断剂curcumin和c-fos反义寡核苷酸在有效抑制AP-1结合活性的同时,也明显地抑制MMP-9 mRNA表达水平。结论:凝血酶在体外培养的人肾小球系膜细胞具有上调MMP-9 mRNA表达的作用,转录因子AP-1介导了凝血酶的这一作用。     

Dopamine D2 receptor suppresses gastric cancer cell invasion and migration via inhibition of EGFR/AKT/MMP-13 pathway

Dopamine (DA), an important neurotransmitter, has been reported to play a negative role in tumor progression. DA acts its role via dopamine receptors (DRs), which can be divided into five receptor subtypes (D1R-D5R). Among these receptor subtypes, D2R has been found to inhibit IGF-I-induced gastric cancer cell growth. However, the functions of D2R in gastric cancer cell invasion remain elusive. Here, we found that D2R expression was decreased in gastric cancer cells. DA treatment dose-dependently inhibited EGF-mediated gastric cancer cell invasion and migration via D2R. Furthermore, D2R decreased EGF-mediated MMP-13 production, and attenuated EGFR and AKT activation. Together with the results that EGF promoted gastric cancer cell invasion and migration via EGFR/AKT pathway, these data indicate that DA treatment, acting via D2R, suppresses gastric cancer cell invasion and migration via inhibition of EGFR/AKT/MMP-13 pathway. Thus, our findings suggest that use of D2R agonist may have a potential therapeutic effect on gastric cancer.     

大黄酸调控Rac1/LIMK1/cofilin信号通路抑制卵巢癌细胞运动与侵袭

目的探讨大黄酸对卵巢癌淋巴结高转移SKOV3-PM4细胞运动和侵袭能力的影响,揭示大黄酸调控Rac1/LIMK1/cofilin信号通路与抑制卵巢癌细胞运动侵袭作用的机制。方法划痕实验观察大黄酸对卵巢癌细胞运动的影响,Matrigel-Transwell方法检测细胞侵袭能力,激光共聚焦扫描显微镜和扫描电镜观察大黄酸对卵巢癌细胞形态和细胞骨架超微结构的影响,Western blot分别检测Rac1/LIMK1/cofilin通路上Rac1、LIMK1、PAK1、cofilin蛋白的表达。结果与空白对照组相比,大黄酸能抑制SKOV3-PM4细胞侵袭和迁移能力,浓度为8.8、17.60、26.40μmol·L~(-1)的大黄酸处理24 h后,细胞体外迁移和侵袭能力均明显下降(P<0.05);细胞出现伪足减少,细胞内微丝断裂、分布紊乱,质膜凹凸不平、细胞间的间隙变宽等超微结构改变;Western blot结果表明大黄酸能明显下调Rac1蛋白的表达水平,并呈浓度依赖性。卵巢癌细胞经大黄酸及Rac1抑制剂处理后,磷酸化LIMK1、cofilin、PAK1蛋白水平与空白对照组比较明显下降,且大黄酸联合Rac1抑制剂处理后的磷酸化蛋白下调更为明显(P<0.05);而Rac1激活剂联合大黄酸组比大黄酸组磷酸化蛋白上调明显(P<0.05)。结论大黄酸为潜在的Rac1小分子抑制剂,其作用机制可能是调控Rac1/LIMK1/cofilin信号通路,抑制卵巢癌淋巴结转移细胞运动和侵袭的能力。     

Fisetin induces apoptosis in human cervical cancer HeLa cells through ERK1/2-mediated activation of caspase-8-/caspase-3-dependent pathway

Fisetin is a naturally occurring flavonoid that has been reported to inhibit the proliferation and to induce apoptotic cell death in several tumor cells. However, the apoptosis-inducing effect of fisetin on tumor cell lines was investigated besides HeLa cells. In this study, we found that fisetin induced apoptosis of HeLa cells in a dose- and time-dependent manner, as evidenced by nuclear staining of 4′-6-Diamidino-2-phenylindole (DAPI), flow cytometry assay, and Annexin-V/PI double-labeling. In addition, fisetin triggered the activations of caspases-3 and -8 and the cleavages of poly (ADP-ribose) polymerase, resulting in apoptosis induction. Moreover, treatment of HeLa cells with fisetin induced a sustained activation of the phosphorylation of ERK1/2, and inhibition of ERK1/2 by PD98059 (MEK1/2 inhibitor) or transfection with the mutant ERK1/2 expression vector significantly abolished the fisetin-induced apoptosis through the activation of caspase-8/-3 pathway. The in vivo xenograft mice experiments revealed that fisetin significantly reduced tumor growth in mice with HeLa tumor xenografts. In conclusion, our results indicated that fisetin exhibited anti-cancer effect and induced apoptosis in HeLa cell lines both in vitro and in vivo.     

Kaempferol suppresses cell migration through the activation of the ERK signaling pathways in ARPE‐19 cells

Kaempferol is a flavonoid with anticancer and anti‐metastasis activity in different cancer‐cell lines. However, the underlying mechanisms by which kaempferol acts on human retinal pigment epithelial (ARPE‐19) cells remain unclear. In this study, we demonstrated that kaempferol inhibited migration and invasion in ARPE‐19 cells at non‐toxic dosages. We discovered that kaempferol obviously reduced the enzyme activity and protein expression of matrix metalloproteinase‐2 by increasing the phosphorylated levels of extracellular signal‐regulated kinases 1/2 (ERK1/2) signaling pathways. Additionally, ERK1/2‐specific inhibitor PD98059 significantly reversed kaempferol's inhibitory effects on migration and expression of MMP‐2 in ARPE‐19 cells. Overall, our results are the first to demonstrate that kaempferol is capable of inhibiting cell migration by targeting ERK1/2 signaling in human retinal pigment epithelial cells.     

A new bisphosphonate derivative,CP, induces gastric cancer cell apoptosis via activation of the ERK1/2 signaling pathway

Aim： To investigate the effects of a new derivative of bisphosphonates, [2-（6-aminopurine-9-yl）-l-hydroxy-phosphine acyl ethyl] phosphonic acid （CP）, on human gastric cancer. Methods： Human gastric cancer cell lines （SGC-7901, BGC-823, MKN-45, and MKN-28） and human colon carcinoma cell lines （LoVo and HT-29） were tested. Cell growth was determined using the MTT assay. Flow cytometry, Western blot, caspase activity assay and siRNA transfection were used to examine the mechanisms of anticancer action. Female BALB/c nude mice were implanted with SGC- 7901 cells. From d6 after inoculation, the animals were injected with CP （200 pg/kg, ip） or vehicle daily for 24 d. Results： CP suppressed the growth of the 6 human cancer cell lines with similar IC5o values （3239 pmol/L）. In SGC-7901 cells, CP arrested cell cycle progression at the G2/M phase. The compound activated caspase-9, increased the expression of pro-apoptotic proteins Bax and Bad, decreased the expression of anti-apoptotic protein Bcl-2. Furthermore, the compound selectively activated ERK1/2 without affecting JNK and p38 in SGC-7901 cells. Treatment of SGC-7901 cells with the specific ERK1/2 inhibitor PD98059 or ERK1/2 siRNA hampered CP-mediated apoptosis. In the human gastric cancer xenograft nude mouse model, chronic administration of CP significantly retarded the tumor growth. Conclusion： CP is a broad-spectrum inhibitor of human carcinoma cells in vitro, and it also exerts significant inhibition on gastric cancer cell growth in vivo. CP induces human gastric cancer apoptosis via activation of the ERK1/2 signaling pathway.     

A new bisphosphonate derivative,CP, induces gastric cancer cell apoptosis via activation of the ERK1/2 signaling pathway

Aim:

To investigate the effects of a new derivative of bisphosphonates, [2-(6-aminopurine-9-yl)-1-hydroxy-phosphine acyl ethyl] phosphonic acid (CP), on human gastric cancer.

Methods:

Human gastric cancer cell lines (SGC-7901, BGC-823, MKN-45, and MKN-28) and human colon carcinoma cell lines (LoVo and HT-29) were tested. Cell growth was determined using the MTT assay. Flow cytometry, Western blot, caspase activity assay and siRNA transfection were used to examine the mechanisms of anticancer action. Female BALB/c nude mice were implanted with SGC-7901 cells. From d6 after inoculation, the animals were injected with CP (200 μg/kg, ip) or vehicle daily for 24 d.

Results:

CP suppressed the growth of the 6 human cancer cell lines with similar IC₅₀ values (3239 μmol/L). In SGC-7901 cells, CP arrested cell cycle progression at the G₂/M phase. The compound activated caspase-9, increased the expression of pro-apoptotic proteins Bax and Bad, decreased the expression of anti-apoptotic protein Bcl-2. Furthermore, the compound selectively activated ERK1/2 without affecting JNK and p38 in SGC-7901 cells. Treatment of SGC-7901 cells with the specific ERK1/2 inhibitor PD98059 or ERK1/2 siRNA hampered CP-mediated apoptosis. In the human gastric cancer xenograft nude mouse model, chronic administration of CP significantly retarded the tumor growth.

Conclusion:

CP is a broad-spectrum inhibitor of human carcinoma cells in vitro, and it also exerts significant inhibition on gastric cancer cell growth in vivo. CP induces human gastric cancer apoptosis via activation of the ERK1/2 signaling pathway.     

钙激活的氯离子通道 A4通过抑制 JAK激酶 2/信号转导及转录激活蛋白 3信号通路对食管癌细胞增殖、迁移及侵袭的影响

目的 探讨钙激活的氯离子通道A4(CLCA4)对食管癌细胞增殖、迁移、侵袭及JAK激酶2/信号转导及转录激活蛋白3(JAK2/STAT3)信号通路的影响.方法 实时荧光定量逆转录聚合酶链反应(qRT-PCR)与蛋白质印迹法(Western blotting)分别检测正常人食管鳞状上皮细胞与人食管癌细胞中CLCA4的表达;将合成的CLCA4过表达载体及其对照分别转染至食管癌细胞Eca109,分别记作CLCA4过表达(pcDNA-CLCA4)组、CLCA4阴性对照(pcDNA-NC)组,并将未转染的细胞作为阴性对照(NC)组.四甲基偶氮唑盐微量酶反应比色法(MTT法)检测细胞增殖能力;细胞迁移实验(Transwell)检测细胞迁移及侵袭能力.JAK2/STAT3信号通路激活剂p-JAK2多肽对细胞增殖、迁移及侵袭的影响.Western blotting检测细胞周期蛋白D1(Cy-clinD1)、依赖性激酶抑制因子(P21)、基质金属蛋白酶2(MMP-2)、基质金属蛋白酶9(MMP-9)、JAK2、STAT3、磷酸化JAK激酶2(p-JAK2)、磷酸化信号转导及转录激活蛋白3(p-STAT3)的表达水平.结果 与Het-1A相比,人食管癌细胞KYSE170、Eca109、TE10中CLCA4 mRNA及蛋白表达水平降低(P<0.05);与pcDNA-NC组比较,pcDNA-CLCA4组细胞存活率显著降低[(52.16±11.41)％比(99.57±13.49)％,P<0.05],迁移细胞数[(56.47±10.03)％比(112.49±13.52)％]与侵袭细胞数[(63.43±9.87)％比(123.47±16.58)％]减少(P<0.05),CyclinD1、MMP-2、MMP-9、p-JAK2、p-STAT3的表达水平降低(P<0.05),P21的表达水平升高(P<0.05);激活JAK2/STAT3信号通路可逆转CLCA4过表达对Eca109细胞增殖、迁移及侵袭的抑制作用.结论 CL-CA4过表达可抑制食管癌细胞增殖、迁移及侵袭,其作用机制可能与抑制JAK2/STAT3信号通路活化有关.     

细胞外信号调节激酶1/2信号通路对B淋巴细胞的影响

丝裂原活化蛋白激酶(mitogen activated proteinkinase,MAPK)普遍存在于低等原核细胞和高等哺乳类细胞内,且具有生物进化的高度保守性。MAPK信号通路能将细胞外刺激信号转导至细胞及其核内,并引起细胞多种生物学反应。目前已发现多条并行的MAPK信号通路,其中细胞外信号调节激酶     

Ouabain facilitates cardiac differentiation of mouse embryonic stem cells through ERK1/2 pathway

Aim:To investigate the effects of the cardiotonic steroid, ouabain, on cardiac differentiation of murine embyronic stem cells (mESCs).Methods:Cardiac differentiation of murine ESCs was enhanced by standard hanging drop method in the presence of ouabain (20 μmol/L) for 7 d. The dissociated ES derived cardiomyocytes were examined by flow cytometry, RT-PCR and confocal calcium imaging.Results:Compared with control, mESCs treated with ouabain (20 μmol/L) yielded a significantly higher percentage of cardiomyocytes, and significantly increased expression of a panel of cardiac markers including Nkx 2.5, α-MHC, and β-MHC. The α1 and 2- isoforms Na(+)/K(+)-ATPase, on which ouabain acted, were also increased in mESCs during differentiation. Among the three MAPKs involved in the cardiac hypertrophy pathway, ouabain enhanced ERK1/2 activation. Blockage of the Erk1/2 pathway by U0126 (10 μmol/L) inhibited cardiac differentiation while ouabain (20 μmol/L) rescued the effect. Interestingly, the expression of calcium handling proteins, including ryanodine receptor (RyR2) and sacroplasmic recticulum Ca(2+) ATPase (SERCA2a) was also upregulated in ouabain-treated mESCs. ESC-derived cardiomyocyes (CM) treated with ouabain appeared to have more mature calcium handling. As demonstrated by confocal Ca(2+) imaging, cardiomyocytes isolated from ouabain-treated mESCs exhibited higher maximum upstroke velocity (P<0.01) and maximum decay velocity (P<0.05), as well as a higher amplitude of caffeine induced Ca(2+) transient (P<0.05), suggesting more mature sarcoplasmic reticulum (SR).Conclusion:Ouabain induces cardiac differentiation and maturation of mESC-derived cardiomyocytes via activation of Erk1/2 and more mature SR for calcium handling.