ERK1/2信号通路与肿瘤关系的研究进展

胞外信号调节激酶(ERK)可以将细胞信号从受体传导至细胞核,是负责细胞外刺激的经典丝裂原活化蛋白激酶(MAPK)通路。相关研究表明ERK通路的激活与许多肿瘤的发生发展密切相关,许多作用于ERK通路上游的抑制剂都表现出抗肿瘤活性。ERK1和ERK2是MAPK/ERK通路最重要的分子,因具有同质性,统称为ERK1/2。ERK1/2可以磷酸化多种底物,参与细胞的增殖、分化、迁移、侵袭、凋亡、癌性转化等重要过程。本文就ERK1/2信号通路及其与肿瘤增殖、凋亡和迁移侵袭的相关性进行综述,以期更好的指导肿瘤治疗。     

活化蛋白C对重症急性胰腺炎大鼠丝裂原活化蛋白激酶信号通路的影响

丝裂原活化蛋白激酶（MAPK）信号通路对重症急性胰腺炎（SAP）继发严重并发症起早期关键介导作用，相应抑制剂可改善SAP的病情。活化蛋白C（APC）具有改善SAP病情的作用，其具体机制尚未阐明。目的：观察APC对SAP大鼠MAPK信号通路中主要激酶的影响以及后续炎症介质的变化，为临床用药提供理论依据。方法：Sprague．DawleY大鼠诱导SAP模型后即刻静脉注射APC10μg/kg或50μg/kg。以基因芯片检测胰腺组织MAPK信号通路相关基因。以实时定量聚合酶链反应（real-timePCR）和蛋白质印迹法检测胰腺组织该通路中p38MAPK、c-Jun氨基端激酶/应激活化蛋白激酶（JNK/SAPK）、细胞外信号调节激酶（ERK）1/2mRNA、蛋白和磷酸化蛋白水平的表达，同时检测肿瘤坏死因子（TNF）-α和白细胞介素（IL）-1β蛋白的表达。结果：与APC治疗组和正常对照组相比，SAP组胰腺组织p38MAPK和JNK2mRNA呈高表达。与SAP组相比，50Ixg/kgAPC治疗组p38MAPK、JNK/SAPK蛋白/磷酸化蛋白表达水平显著降低，ERK1/2蛋白/磷酸化蛋白表达水平显著升高，TNF-α和蛋白表达水平显著降低（P均〈0．05）。APC治疗组p38MAPK、磷酸化ERK1/2和TNF-α蛋白表达水平呈剂量依赖性（P均〈0．05）。结论：APC可抑制SAP大鼠胰腺组织MAPK信号通路内p38MAPK和JNK/SAPK的表达和活化，进而抑制TNF-α和IL-1β的释放，同时上调ERK1/2的表达和活化．从而减轻胰腺组织损伤。     

有丝分裂原活化蛋白激酶/细胞外调节信号激酶信号转导通路与肝纤维化逆转的相关性

近年发现，无论是消除致病因素或是应用有效抗纤维化药物，都可逆转患者及模型动物的肝纤维化。但具体机制尚不明确。南于有丝分裂原活化蛋白激酶（MAPK）／细胞外调节信号激酶（ERK）信号通路在多种损伤修复过程中发挥重要作用，我们在建立肝纤维化自发逆转动物模型的基础上，检测MAPK／ERK信号通路的活性，以揭示该通路与肝纤维化逆转的相关性。     

帕金森病与丝裂原活化蛋白激酶信号通路的相关性及中医药干预作用

帕金森病（PD）是一种进行性多系统神经退行性疾病，其中黑质多巴胺能神经元丧失是其重要的病理改变。丝裂原活化蛋白激酶（MAPK）信号通路能调节细胞的生长、分化、凋亡、炎症等多种生理病理过程，近年来其已成为PD机制研究的热点。本文主要综述了PD与MAPK亚家族[p38 MAPK、c-Jun氨基末端激酶（JNK）和细胞外信号调节激酶（ERK）]的相关性及中医药干预作用，以期为PD的诊疗提供新的思路。     

ERK1/2信号转导通路在宫颈癌发病中的作用

细胞外信号调节激酶（ERK）是丝裂原活化蛋白激酶（MAPK）家族成员之一,该酶被激活后,在细胞生长、发育、分裂、死亡及恶性转化等过程中发挥作用。由E RK1/2介导的信号转导通路接受来自细胞内外的各种丝裂原刺激和应激,激活ERK1/2底物,调控细胞增殖、凋亡与侵袭。为了揭示宫颈癌发生发展的分子学机制，探讨宫颈癌的有效防治方法，研究者从ERK1／2信号转导通路途径对宫颈癌做了大量研究。     

细胞外信号调节激酶在肝病治疗中的研究进展

细胞外信号调节激酶(ERK)是MAPK信号转导通路的重要成员之一。多种细胞生理过程如增殖、凋亡及分化都涉及到ERK信号转导通路的调节。ERK与慢性肝病的发生发展密切相关,抑制ERK表达或信号转导可用于治疗肝纤维化和肝癌。     

慢性支气管哮喘模型大鼠气道中细胞外信号调节激酶1/2表达及活性变化的研究

细胞外信号调节激酶（ERK）属于有丝分裂原激活蛋白激酶（MAPK）家族，它是细胞内重要的信号传递分子，并有多种亚型，在平滑肌中主要有ERK1、ERK2（ERK1/2）两种，该通道在支气管哮喘（简称哮喘）病理生理发生和发展过程中的作用得到越来越多的关注。     

p38丝裂原活化蛋白激酶在心血管疾病中的作用

丝裂原活化蛋白激酶（mitogen activated protein kinase，MAPKs）是细胞内的主要信息传递系统，可将细胞外信息传递至细胞核中，从而介导细胞产生各种反应。MAPK通路主要有4条途径：细胞外调节蛋白激酶（Ras／ERK）、c-jun氨基末端激酶（JNK）／应激激活的蛋白激酶（SAPK）、p38、ERK5，其中p38信号途径是MAPK家族中的重要组成部分，参与了多种细胞的胞内信号传递，现将在许多疾病的发生、发展过程中具有明显的调控作用。p38MAPK在心血管疾病中的作用论述如下。     

ERK信号通路与肺纤维化中细胞因子相互关系的研究

丝裂素活化蛋白激酶(MAPK)是信号从细胞表面转导到细胞内部的重要传递，包括ERK、JNK、P38及ERK5亚族。MAPK家族在调控细胞生长、发育、分裂及细胞间功能的同步性等多种生理功能中起着重要作用。细胞外调节蛋白激酶(ERK)通路是迄今研究最为透彻的一条MAPK信号转导通路，它的激活同许多细胞因子密切相关。     

MAPK信号通路在力学刺激对MG-63成骨样细胞护骨素表达中的作用

目的观察力学刺激对MG-63成骨样细胞护骨素(osteoprotegrin,OPG)表达及丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)信号通路的影响,以及探讨MAPK信号通路在OPG表达中的作用。方法将不同作用时间的机械应变分别作用于MG-63成骨样细胞,采用免疫印迹(Western blot)法检测OPG蛋白、磷酸化的细胞外信号调节激酶1/2 (p-ERK1/2)、p38MAPK (p-p38MAPK)、JNK (p-JNK)表达,采用RT-PCR方法检测OPG mRNA的表达,同时应用信号通路阻断剂观察MAPK各信号通路在OPG表达中的作用。结果机械力学刺激明显促进了MG-63成骨样细胞OPG蛋白及mRNA的表达,加力1、3、6、12 h后OPG蛋白表达分别是对照组的2. 3、4. 2、5. 9、6. 6倍(P<0. 05),加力3、6、12 h后OPG mRNA表达分别是对照组的4. 8、6. 8、7. 5倍(P<0. 05),加力12 h组作用最明显。力学刺激能够激活ERK1/2信号通路,加力60 min后激活最显著,p-ERK1/2表达是对照组的3. 2倍(P <0. 05)。力学刺激也能激活JNK信号通路,加力10 min后开始活化,加力30 min后最显著,加力10、15、30 min后p-JNK表达分别是对照组的2. 9、4. 3、5. 1倍(P<0. 05)。但力学刺激不能激活p38MAPK信号通路。分别应用ERK1/2、JNK的信号通路阻断剂后,发现当抑制ERK1/2信号通路时,OPG蛋白表达也受到了抑制,差异有统计学意义(P<0. 05)。结论机械力学刺激上调了MG-63成骨样细胞OPG蛋白及mRNA的表达,ERK1/2信号通路可能参与了此过程。     

Hepatitis C virus core protein activates the MAPK/ERK cascade synergistically with tumor promoter TPA, but not with epidermal growth factor or transforming growth factor alpha

Persistent hepatitis C virus (HCV) infection is associated with the development of human hepatocellular carcinoma (HCC), although the mechanism of HCV-related hepatocarcinogenesis remains unclear. Recently, however, the close relationships between the development of HCC and the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated protein kinase (ERK) cascade have been described. In the present study, we investigated the effects of HCV core protein on this MAPK/ERK cascade. HCV core protein significantly activated the MAPK/ERK cascade, including Elk1. We also examined whether HCV core protein acted synergistically along with hepatocyte mitogen-mediated MAPK/ERK activation. Interestingly, Elk-1 activities were further enhanced by the tumor promoter, 12-O-tetradecanoyl phorbol 13-acetate (TPA), but not by hepatocyte mitogens (epidermal growth factor [EGF] and transforming growth factor alpha [TGF-alpha]) in NIH3T3 cells and HepG2 cells expressing HCV core protein. Moreover, the MAPK/ERK activation by HCV core protein was blocked in the presence of the specific MEK1 inhibitor, PD98059. These results indicate that ERK activation by HCV core protein may be independent of hepatocyte mitogen-mediated signaling but synergistic with TPA, and HCV core protein may function at MEK1 or farther upstream of that component.     

Loss of Raf kinase inhibitor protein promotes cell proliferation and migration of human hepatoma cells

BACKGROUND & AIMS: The Raf kinase inhibitor protein (RKIP) has been identified as a suppressor of the mitogen-activated protein kinase (MAPK) pathway. Loss of RKIP function promotes tumor metastasis in prostate cancer and melanoma. The insulin-like growth factor I (IGF-I)-mediated MAPK cascade is often activated in hepatocellular carcinoma (HCC), but the role of RKIP in the molecular pathogenesis of these tumors is unknown. This study was performed to evaluate the role of RKIP in the development of HCC. METHODS: The levels of RKIP expression in HCC tumor and corresponding peritumoral tissues were determined by immunohistochemistry and Western blot analysis. The underlying mechanisms of RKIP were assessed with immunoblot analysis, Raf kinase activity assay, cell proliferation, and migration assays after either overexpression or knockdown of RKIP expression in HCC cell lines. RESULTS: RKIP expression is down-regulated in human HCC compared with adjacent peritumoral tissues. Low RKIP levels were correlated with enhanced extracellular signal-regulated-kinase (ERK)/MAPK pathway activation. Reconstitution experiments antagonized IGF-I-mediated MAPK pathway activation, resulting in reduced nuclear accumulation of phospho-ERK. In contrast, knockdown of RKIP expression using small interfering RNA induced activation of the ERK/MAPK pathway. Ectopic expression of RKIP altered HCC cell proliferation and migration. CONCLUSIONS: Our findings indicate that down-regulation of RKIP expression is a major factor in activation of the IGF-I/ERK/MAPK pathway during human hepatocarcinogenesis.     

Constitutive Activation of Extracellular Signal-Regulated Kinase and p38 Mitogen-Activated Protein Kinase in B-Cell Lymphoproliferative Disorders

Signaling molecules such as p21(ras) (Ras), mitogen-activated protein kinase (MAPK), and Akt kinase play pivotal roles in the proliferation and survival of lymphoid cells in response to many kinds of stimulation. It is not fully understood, however, how these molecules participate in the growth of malignant lymphoid cells. We determined whether Ras, MAPKs such as extracellular signal-regulated kinase (ERK), c-Jun amino-terminal kinase (JNK), and p38 MAPK, and Akt kinase are activated in B-cell tumors, including acute lymphoblastic leukemia, chronic lymphocytic leukemia, Burkitt-like lymphoma, diffuse large B-cell lymphoma, and plasma cell leukemia. We found that Lyn protein tyrosine kinase was constitutively phosphorylated on tyrosine, and that ERK and p38 MAPK were constitutively active in all cases of the B-cell tumor. In contrast, activation of Ras and Akt kinase was found in limited cases, and JNK kinase activity was not observed in any case. These results suggest that ERK and p38 play roles in the oncogenesis of B-cell tumors.     

Human neutrophils utilize a Rac/Cdc42-dependent MAPK pathway to direct intracellular granule mobilization toward ingested microbial pathogens

Elevated levels of mitogen-activated protein kinase/extracellular regulatory kinase (MAPK/ERK) activity are frequently found in some cancer cells. In efforts to reduce tumor growth, attempts have been made to develop cancer therapeutic agents targeting the MAPK. Here, by use of biologic, biochemical, and gene manipulation methods in human polymorphonuclear neutrophils (PMNs), we have identified a key pathway important in normal cell function involving MAPK/ERK in PMNs for growth inhibition of Candida albicans. Contact with C albicans triggered MAPK/ERK activation in PMNs within 5 minutes, and blocking of MAPK/ERK activation, either by the pharmacologic reagent PD098059 or by dominant-negative MAPK kinase (MEK) expression via vaccinia viral delivery, suppressed antimicrobial activity. Rac and Cdc42, but not Ras or Rho, were responsible for this MAPK/ERK activation. Expression of dominant-negative Rac (N17Rac) or Cdc42 (N17Cdc42) eliminated not only C albicans- mediated ERK phosphorylation but also phagocytosis and granule migration toward the ingested microbes, whereas dominant-negative Ras (N17Ras) and Rho (N19Rho) did not. PAK1 (p21-activated kinase 1) activation is induced by C albicans, suggesting that PAK1 may also be involved in the Rac1 activation of MAPK/ERK. We conclude from these data that Rac/Cdc42-dependent activation of MAPK/ERK is a critical event in the immediate phagocytic response of PMNs to microbial challenge. Therefore, use of MAPK pharmacologic inhibitors for the treatment of cancer may result in the interruption of normal neutrophil function. A balance between therapeutic outcome and undesirable side effects must be attained to achieve successful and safe anticancer therapy.     

MEK/ERK pathway is aberrantly active in Hodgkin disease: a signaling pathway shared by CD30, CD40, and RANK that regulates cell proliferation and survival

The mitogen-activated protein kinase (MAPK) (also called extracellular signal-regulated kinase [ERK]) pathway has been implicated in malignant transformation and in the regulation of cellular growth and proliferation of several tumor types, but its expression and function in Hodgkin disease (HD) are unknown. We report here that the active phosphorylated form of MAPK/ERK is aberrantly expressed in cultured and primary HD cells. Inhibition of the upstream MAPK kinase (also called MEK) by the small molecule UO126 inhibited the phosphorylation of ERK and demonstrated a dose- and time-dependent antiproliferative activity in HD cell lines. UO126 modulated the levels of several intracellular proteins including B-cell lymphoma protein 2 (Bcl-2), myeloid cell leukemia-1 (Mcl-1) and caspase 8 homolog FLICE-inhibitory protein (cFLIP), and induced G2M cell-cycle arrest or apoptosis. Furthermore, UO126 potentiated the activity of apoliprotein 2/tumor necrosis factor-related apoptosis-inducing ligand (APO2L/TRAIL) and chemotherapy-induced cell death. Activation of CD30, CD40, and receptor activator of nuclear kappabeta (RANK) receptors in HD cells by their respective ligands increased ERK phosphorylation above the basal level and promoted HD cell survival. UO126 inhibited basal and ligand-induced ERK phosphorylation, and inhibited ligand-induced cell survival of HD cell lines. These findings provide a proof-of-principle that inhibition of the MEK/ERK pathway may have therapeutic value in HD.     

Angiotensin II-induced cardiac hypertrophy is associated with different mitogen-activated protein kinase activation in normotensive and hypertensive mice

OBJECTIVE: In addition to its haemodynamic effects, angiotensin II (AngII) is thought to contribute to the development of cardiac hypertrophy via its growth factor properties. The activation of mitogen-activated protein kinases (MAPK) is crucial for stimulating cardiac growth. Therefore, the present study aimed to determine whether the trophic effects of AngII and the AngII-induced haemodynamic load were associated with specific cardiac MAPK pathways during the development of hypertrophy. Methods The activation of the extracellular-signal-regulated kinase (ERK), the c-jun N-terminal kinase (JNK) and the p38 kinase was followed in the heart of normotensive and hypertensive transgenic mice with AngII-mediated cardiac hypertrophy. Secondly, we used physiological models of AngII-dependent and AngII-independent renovascular hypertension to study the activation of cardiac MAPK pathways during the development of hypertrophy. RESULTS: In normotensive transgenic animals with AngII-induced cardiac hypertrophy, p38 activation is associated with the development of hypertrophy while ERK and JNK are modestly stimulated. In hypertensive transgenic mice, further activation of ERK and JNK is observed. Moreover, in the AngII-independent model of renovascular hypertension and cardiac hypertrophy, p38 is not activated while ERK and JNK are strongly stimulated. In contrast, in the AngII-dependent model, all three kinases are stimulated. CONCLUSIONS: These data suggest that p38 activation is preferentially associated with the direct effects of AngII on cardiac cells, whereas stimulation of ERK and JNK occurs in association with AngII-induced mechanical stress.     

Constitutive Activation of the Mitogen-Activated Protein Kinase Signaling Pathway in Acral Melanomas

One of the most attractive clinical targets for melanoma is the mitogen-activated protein kinase (MAPK) signaling pathway. In this study, we examined MAPK signaling activation in a total of 28 acral melanoma samples, consisting of 13 primary tumors and 15 metastases. In line with the previous reports, NRAS/BRAF mutations were rare; only one metastatic tumor had an NRAS E61R mutation, and one primary tumor and two metastases harbored BRAF V599E mutations. Western blot analyses, however, revealed phosphorylated extracellular signal-regulated kinase (ERK)1/2 proteins in 11 of 14 (78.5%) of the acral melanoma tumors. Furthermore, fluorescence in situ hybridization analyses revealed the prominent amplification of the cyclin D1 ( CCND1 ) gene, which is an important down-stream effecter of the MAPK pathway, in 5 of 21 (23.8%) tumors examined. Interestingly, two of three tumors that were negative for phosphorylated ERK proteins according to western blot harbored CCND1 amplifications, suggesting that the increased gene dosage of CCND1 may exert effects similar to phosphorylated ERK proteins in cell growth. We conclude that, despite the low frequency of BRAF/NRAS mutations, the MAPK signaling pathway is constitutively activated in the majority of acral melanomas. This provides a rational basis to include acral melanomas into the clinical trials with MAPK inhibitors.     

Convergence of redox-sensitive and mitogen-activated protein kinase signaling pathways in tumor necrosis factor-alpha-mediated monocyte chemoattractant protein-1 induction in vascular smooth muscle cells

Monocyte chemoattractant protein-1 (MCP-1) is an important component of the inflammatory response of the vessel wall and has been shown to be regulated by cytokines, such as tumor necrosis factor-alpha (TNF-alpha). However, the precise signaling pathways leading to MCP-1 induction have not been fully elucidated in vascular smooth muscle cells (VSMCs). Cytokine signal transduction involves protein kinases as well as reactive oxygen species (ROS). The relation between these 2 factors is not clear. In this study, we show that TNF-alpha induces a parallel phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (p38MAPK) and increases MCP-1 mRNA expression in cultured VSMCs. Inhibition of ERK1/2 but not p38MAPK caused a partial attenuation of MCP-1 induction (43+/-10% inhibition). Incubation of VSMCs with multiple antioxidants (diphenylene iodonium, liposomal superoxide dismutase, catalase, N-acetylcysteine, dimethylthiourea, and pyrrolidine dithiocarbamate) had no effect on TNF-alpha-mediated MCP-1 upregulation. However, simultaneous blockade of the ERK1/2 and ROS pathways by using PD098059 combined with diphenylene iodonium or N-acetylcysteine potently enhanced the ability of MAPK kinase inhibitors to abrogate MCP-1 mRNA expression (100+/-2% inhibition). Thus, parallel ROS-dependent and ERK1/2-dependent pathways converge to regulate TNF-alpha-induced MCP-1 gene expression in VSMCs. These data unmask a complex but organized integration of ROS and protein kinases that mediates cytokine-induced vascular inflammatory gene expression.     

Chylomicron remnants upregulate CD40 expression via the ERK pathway and a redox-sensitive mechanism in THP-1 cells

CD40 is a 48kDa phosphorylated transmembrane glycoprotein that belongs to the tumor necrosis factor receptor superfamily and may play a role in formation of atherosclerotic plaques. Here, we investigated the effect of chylomicron remnants on CD40 expression in the human premonocytic cell line, THP-1 cells. Chylomicron remnants upregulated the expression of CD40 protein and mRNA in a dose- and time-dependent manner. Further, chylomicron remnants increased the generation of reactive oxygen species as determined by an increasing level of 2',7'-dichlorofluorescein. Pretreatment with the antioxidant, N-acetylcysteine, inhibited chylomicron remnant-induced CD40 protein expression by 60%. On the other hand, chylomicron remnants transiently increased the phosphorylation of extracellular signal-regulated kinase (ERK 1/2) and p38 mitogen-activated protein kinase (MAPK). Pretreatment with the MAPK kinase inhibitor, U0126, completely inhibited chylomicron remnants-induced CD40 protein expression, whereas the p38 MAPK inhibitor, SB203580, had no effect. Pretreatment with N-acetylcysteine had no effect on chylomicron remnant-induced ERK 1/2 phosphorylation. These data suggest that CD40 expression stimulated by chylomicron remnants in THP-1 cells is dependent on ERK 1/2-mediated pathway, which is followed by redox-sensitive mechanism-dependent and independent pathway. Thus, chylomicron remnants may contribute to the formation of atherosclerotic plaques via their immunological and proinflammatory effects.     

Activation of Extracellular Signal-Regulated Kinase through B-Cell Antigen Receptor in B-Cell Chronic Lymphocytic Leukemia

B-cell chronic lymphocytic leukemia (B-CLL) cells express on their surface membranes immunoglobulin (Ig) M or IgD, both of which normally function as B-cell antigen receptors (BCRs). However, in contrast to normal B-cells, in B-CLL cells several important signaling pathways, such as the activation of protein tyrosine kinase via BCR, are defective. We have examined whether the activities of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), p38 MAPK, and Akt kinase, are functional in B-CLL cells, because these kinases play critical roles in activation in response to BCR stimulation, tumor cell growth, and survival. In B-CLL cells, BCR cross-linking neither induced activation nor enhanced the activities of Lyn, Syk, p21ras, JNK, p38 MAPK, or Akt kinases, whereas p38 MAPK and Akt were constitutively active. In contrast, BCR cross-linking resulted in ERK activation, although the activation in quiescent cells was case dependent. These results suggest that some signaling pathways, such as the activation of ERK through BCR, are functional in B-CLL cells despite the extensive impairment of signaling pathways.