Effect of phosphorylation of MAPK and Stat3 and expression of c-fos and c-jun proteins on hepatocarcinogenesis and their clinical significance

AIM To study the effect of phosphorylation ofMAPK and Stat3 and the expression of c-fos andc-jun proteins on hepatocellular carcinogenesisand their clinical significance.METHODS SP immunohistochemistry was usedto detect the expression of p42/44~(MAPK), p-Stat3,c-fos and c-jun proteins in 55 hepatocellularcarcinomas (HCC) and their surrounding livertissues.RESULTS The positive rates and expressionlevels of p42/44~(MAPK), p-Stat3, c-fos and c-junproteins in HCCs were significantly higher thanthose in pericarcinomatous liver tissues (PCLT).A positive correlation was observed between theexpression of p42/44~(MAPK) and c-fos proteins, andbetween p-Stat3 and c-jun, but there was nosignificant correlation between P42/44~(MAPK) and p-Stat3 in HCCs and their surrounding livertissues.CONCLUSION The abnormalities of Ras/Raf/MAPK and JAKs/ Stat3 cascade reaction maycontribute to malignant transformation ofhepatocytes. Hepatocytes which are positive forp42/ 44~(MAPK), c-fos or c-jun proteins may bepotential malignant pre-cancerous cells.Activation of MAPK and Stat3 proteins may be anearly event in hepatocellular carcinogenesis.     

食管癌组织中STAT3通路相关调控基因的表达及临床意义

目的探讨转录信号传导子与激活子-3(Stat3)及CyclinD1、p53、c-fos在食管癌发生发展过程中的作用及意义。方法采用免疫组化方法检测100份食管癌组织及60份正常食管黏膜组织中Stat3、CyclinD1、p53及c-fos蛋白的表达情况。结果 Stat3蛋白在正常食管黏膜、食管癌组织中的阳性表达率分别为6.7%、94.0%,P<0.05;食管癌组织CyclinD1、p53、c-fos蛋白均明显高于正常食管组织(P<0.05)。Stat3与CyclinD1、p53、c-fos表达呈正相关(P<0.05)。结论 Stat3过度表达在食管癌发生发展过程中起重要作用;CyclinD1、p53、c-fos蛋白在调控食管癌癌变过程中可能起协同作用。     

Expression and activity of mitogen activated protein kinases in human colorectal carcinoma

BACKGROUND: Mitogen activated protein kinases (MAPKs) play a central role in the regulation of both cell growth and differentiation. They are involved in signal transduction of oncogenes and growth factors. The role of MAPK in colonic carcinoma is unknown. AIMS: To establish whether the expression and activity of p42/44 MAPKs are altered in colorectal tumours as compared with normal mucosa. METHODS: The expression and activity of p42/p44 MAPK were investigated in 22 colorectal carcinomas, four adenomas, and the corresponding normal colorectal mucosa by the use of western blotting, immunoprecipitation, and in vitro kinase assays. RESULTS: After immunoprecipitation with an antibody specific for p42 MAPK, we found significant inactivation of p42 MAPK in colonic carcinomas as well as in adenomas, whereas most sample pairs showed only minor differences in p42 MAPK expression. Investigation of MAPK with an antibody capable of detecting both p42 and p44 MAPK showed a slight but significant decrease in p44 MAPK content in malignant tissues. With this antibody, only minor alterations in MAPK activity and no correlation with p42 MAPK activity were found. CONCLUSIONS: Inactivation of p42 MAPK could be associated with colonic carcinogenesis.     

Activation of the p38 mitogen-activated protein kinase pathway by gonadotropin-releasing hormone

Previous studies have shown that interaction of GnRH with its serpentine, G protein-coupled receptor results in activation of the extracellular signal regulated protein kinase (ERK) and the Jun N-terminal protein kinase (JNK) pathways in pituitary gonadotropes. In the present study, we examined GnRH-stimulated activation of an additional member of the mitogen-activated protein kinase (MAPK) superfamily, p38 MAPK GnRH treatment of alphaT3-1 cells resulted in tyrosine phosphorylation of several intracellular proteins. Separation of phosphorylated proteins by ion exchange chromatography suggested that GnRH receptor stimulation can activate the p38 MAPK pathway. Immunoprecipitation studies using a phospho-tyrosine antibody resulted in increased amounts of immunoprecipitable p38 MAPK from alphaT3-1 cells treated with GnRH. Immunoblot analysis of whole cell lysates using a phospho-specific antibody directed against dual phosphorylated p38 kinase revealed that GnRH-induced phosphorylation of p38 kinase was dose and time dependent and was correlated with increased p38 kinase activity in vitro. Activation of p38 kinase was blocked by chronic phorbol ester treatment, which depletes protein kinase C isozymes alpha and epsilon. Overexpression of p38 MAPK and an activated form of MAPK kinase 6 resulted in activation of c-jun and c-fos reporter genes, but did not alter the expression of the glycoprotein hormone alpha-subunit reporter. Inhibition of p38 activity with SB203580 resulted in attenuation of GnRH-induced c-fos reporter gene expression, but was not sufficient to reduce GnRH-induced c-jun or glycoprotein hormone alpha-subunit promoter activity. These studies provide evidence that the GnRH signaling pathway in alphaT3-1 cells includes protein kinase C-dependent activation of the p38 MAPK pathway. GnRH integration of c-fos promoter activity may include regulation by p38 MAPK.     

Involvement of p38 mitogen-activated protein kinase signaling in transformed growth of a cholangiocarcinoma cell line

Although mitogen-activated protein kinase (MAPK) pathways play a key role in cell growth, their role in mediating the altered growth phenotype of transformed cells remains unclear. The p44/p42 MAPK signaling cascades are activated by mitogenic stimulation of human cholangiocytes. In contrast, the p38 MAPK pathway is activated by mitogen stimulation of malignant, but not nonmalignant cholangiocytes. Thus, our aims were to determine the role of p38 MAPK signaling in mediating the growth phenotype of transformed cholangiocytes. KMCH-1 malignant human cholangiocytes required the presence of serum for proliferation, but were able to grow in reduced serum conditions. Inhibition of p38 MAPK decreased serum-dependent proliferation of KMCH-1 cells. Furthermore, inhibition of p38 MAPK, but not of p44/p42 MAPK, reduced anchorage-independent growth of KMCH-1 cells. Although both p38 and p44/p42 MAPK are activated in response to mitogens, they have divergent effects on anchorage-independent growth. Inhibition of p38 MAPK, but not of p44/p42 MAPK signaling, decreased cell cycle progression and increased expression of the cyclin-dependent kinase inhibitor p21(WAF1/CIPl). However, expression of p27(KIP1) or p16(INK4A) was not altered by either pathway. Thus, mitogen activation of p38 MAPK decreases expression of p21(WAF1/CIP1) and mediates growth independent of anchorage signals, whereas mitogen activation of p44/p42 MAPK mediates an anchorage signal-dependent growth pathway. These data provide a link between aberrant stress-activated cell signaling and the altered growth phenotype of transformed cells that may be important for the development of therapies to limit transformed cell growth.     

针对STAT3的siRNA抑制HepG2细胞增殖和p44/42MAPK蛋白的表达

目的研究STAT3信号传导通路对HepG2细胞p44/42MAPK蛋白表达和细胞生长的影响。方法将针对STAT3的siRNA转染入HepG2细胞以沉默STAT3基因的表达,采用MTT法检测细胞生长,采用Western blot法检测STAT3和p44/42MAPK蛋白的表达。结果对照组和lipofectamineTM2000处理组细胞生长无明显差异(q=0.97,P0.05),而siRNA处理组细胞生长被明显抑制(q=9.36,P0.05);SiRNA转染后24h、48h、72h和96h,细胞抑制率分别为33.2%、39.6%4、3.1%和33.9%s,iRNA在96h后抑制作用减弱,细胞开始重新繁殖;转染细胞72h和96h后,可见STAT3蛋白表达均被抑制(t=14.12,P0.05),p44/42MAPK蛋白表达未被抑制(F=3.99,P0.05),而p-p44/42MAPK蛋白表达增加(t=16.30,P0.05)。结论 STAT3信号传导通路可以影响细胞生长及p44/42MAPK蛋白质的磷酸化,而p-p44/42MAPK的表达增加可能代偿了沉默STAT3引起的细胞生长抑制,使细胞重新繁殖。     

Interaction between resistin and adiponectin in the proliferation of rat vascular smooth muscle cells

We investigated the effect between resistin and adiponectin on the proliferation of vascular smooth muscle cells (VSMCs). We confirmed that resistin significantly increases the number of rat VSMCs as well as thymidine incorporation with them, whereas adiponectin diminishes resistin-induced cell proliferation. Resistin significantly increased p42/44 mitogen-activated protein kinase (MAPK) phosphorylation within rat VSMCs, whereas adiponectin inhibited resistin-induced MAPK phosphorylation. Moreover, resistin significantly increased c-fos expression, whereas adiponectin suppressed resistin-induced c-fos expression. Cell cycle progression is a tightly controlled event that is negatively regulated by cyclin-dependent kinases inhibitors (CDKIs) such as p53, p21, and p27. Resistin significantly decreased the expression of these CDKIs, whereas adiponectin restored the resistin-induced decrease in CDKIs expression. These effects were abolished in the MAPK inhibitors.     

HCC和HepG2细胞表达HCV C蛋白、p14ARF、p21WAF1的意义探讨

目的检测HCVC蛋白、p14、p21在HCC和表达野生p53HepG2中的表达，初步探讨C蛋白在HCC和HepG2中对p14-p53-p21凋亡通路的作用。方法收集42例HCC石蜡组织，采用免疫组织化学EnVision法检测HCC组织中核心蛋白、p14和p21的表达，用统计学方法及临床联系分析它们之间的关系；用细胞化学EnVision法和免疫荧光法检测核心蛋白、p53、p14和p21在HepG2细胞中的表达。结果C蛋白、p14和p21的阳性表达主要定位于细胞核膜和细胞核中；HCC组织中C蛋白、p14和p21阳性率分别为40．5％、45．24％、19．05％；3组间的Kruskal-Wallis检验P=0．03，差异显著；C蛋白与p14、p21间及p14与D21间蛋白阳性强度相关性分析显示，P值分别为0．000、0．43、-0．34，相关系数rs分别为0．64、-0．29、-0．33。HepG2细胞有较高的C蛋白和p53表达及少量的p14、p21蛋白表达。结论在C蛋白阳性的HCC中p14的表达与C蛋白有关，HCC中D21表达缺陷是十分常见的；C蛋白在HCC中可能影响p53通路，下调p21的表达，阻止其凋亡作用；HepG2细胞永生化特性可能与HCV或HCVC蛋白有关。     

信号转导子和激活子3通路调控大鼠血管平滑肌细胞增殖迁移机制研究

目的研究转录信号转导子和激活子3（stat3）通路与大鼠血管平滑肌细胞（VSMCs）增殖迁移的关系,明确VSMCs增殖的信号转导过程。方法应用脂质体转染Stat3反义寡核苷酸作用于大鼠VSMCs,应用酶联免疫法（ELISA）检测Stat3水平变化及MTF法检测细胞增殖状态,蛋白免疫印迹法（Western blot）检测stat3、磷酸化stat3及其靶基因产物Cyclin D1、Bcl—XL的表达。结果转染Stat3反义寡核苷酸后,大鼠VSMCs中Stat3水平明显下降（P〈0．01）,同时其增殖水平降低,而相应空白对照组、脂质体组、转染正义寡核苷酸组变化不明显。转染Stat3反义寡核苷酸的VSMCs中stat3、p-Stat 3、Cyclin D1蛋白表达水平随作用时间延长而下降（P〈0．01）,而Bcl—xL水平无明显变化。结论癌基因stat3信号通路与大鼠VSMCs增殖高度相关,可能通过其下游靶基因Cyclin D1影响其增殖,而阻断此通路则可抑制VSMCs的增殖。     

Alpha-fetoprotein stimulated the expression of some oncogenes in human hepatocellular carcinoma Bel 7402 cells

AIM: To investigate the molecular mechanism of alpha-fetoprotein (AFP) on regulating the proliferation of human hepatocellular carcinoma cells. METHODS: Alpha-fetoprotein purified from human umbilical blood was added to cultured human hepatocellular carcinoma Bel 7402 cells in vitro for various treatment periods. The expression of c-fos, c-jun, and N-ras mRNA involved in proliferation and differentiation of cells was analyzed by Northern blot, and the expression of mutative p53 and p21(ras) proteins was determined by Western blot. RESULTS: The results showed that AFP (20 mg/L) stimulated mRNA expression of these oncogenes in Bel 7402 cells. The expression of c-fos mRNA increased by 51.1%, 60.9%, 96.0%, and 25.5% at 2, 6, 12, and 24 h, respectively. The expression of c-jun and N-ras mRNA reached to the maximum which increased by 81.3% and 59.9% as compared with the control after 6 h and 24 h incubation with AFP, respectively. Western blot assay also demonstrated that AFP promoted the expression of mutative p53 and p21(ras) proteins, and the increased rate of those proteins was 13.0%, 39.9%, and 70.9%, as well as 35.2%, 102.6%, and 46.8% at 6, 12, and 24 h, respectively, as compared with the control. Both human serum albumin (the same dosage as AFP) and monoclonal anti-AFP antibody failed to stimulate the expression of these oncogenes, but anti-AFP antibody could block the functions of AFP. CONCLUSION: The data indicate that AFP can stimulate the expression of some oncogenes to enhance the proliferation of human hepatocellular carcinoma Bel 7402 cells.     

HIV-1 gp120 induces the activation of both c-fos and c-jun immediate-early genes in HEL megakaryocytic cells

We have previously demonstrated that the addition in culture of recombinant HIV-1 IIIB envelope gp120 affects the survival/growth of pluripotent haemopoietic progenitors, and, in particular, of those committed towards the megakaryocytic lineage. To characterize some of the molecular mechanisms involved in this phenomenon, we investigated the expression of members of the activating protein-1 (AP-1) complex in the HEL megakaryoblastic cell line. Following the treatment of HEL cells with recombinant IIIB envelope gp120, we noticed: (i) increased levels of endogenous c-fos and c-jun mRNA and proteins, (ii) activation of both c-fos and c-jun promoters, and (iii) a very rapid stimulation of a MAPK/ERK pathway.     

缬沙坦对血管平滑肌细胞迁移及丝裂原活化蛋白激酶的影响

目的观察缬沙坦（Val）对血管紧张素Ⅱ（AngⅡ）刺激下大鼠血管平滑肌细胞（VsMC）迁移及磷酸化42／44丝裂原活化蛋白激酶（p42／44MAPK）表达的影响。方法组织贴块法培养大鼠胸主动脉平滑肌细胞,tran-sweⅡ小室检测细胞的迁移能力,免疫印迹法检测p42／44MAPK蛋白表达的水平。结果（1）AngⅡ能明显促进VSMC迁移,该作用可被Val和MAPK激酶的特异性抑制剂PD98059所抑制。（2）AngⅡ刺激VSMC5min时,p42／44MAPK的表达量最大,该作用可被Val和PD98059所抑制。（3）Val单独作用于VSMC时,对细胞的迁移及p42／44MAPK的表达均无明显影响。结论Val抑制AngⅡ诱导的VSMC迁移与其抑制AngⅡ诱导的p42／44MAPK的表达相关。     

Epidermal growth factor and insulin-induced deoxyribonucleic acid synthesis in primary rat hepatocytes is phosphatidylinositol 3-kinase dependent and dissociated from protooncogene induction

The mitogenic response to insulin and epidermal growth factor (EGF) was studied in subconfluent and confluent cultures of primary rat hepatocytes. In subconfluent cultures, wortmannin, LY294002, and rapamycin reversed insulin- and EGF-induced [3H]thymidine incorporation into DNA. The mitogen-activated protein kinase (MAPK) kinase 1 (MEK1) inhibitor PD98059 was without significant effect on either insulin- or EGF-induced [3H]thymidine incorporation. Insulin treatment did not alter levels of messenger RNAs (mRNAs) for c-fos, c-jun, and c-myc. EGF induced an increase in c-myc, but not c-fos or c-jun, mRNA levels in subconfluent hepatocyte cultures. This increase in c-myc mRNA was abolished by PD98059. In confluent cells that could not be induced to synthesize DNA, EGF treatment also promoted an increase in c-myc mRNA to levels seen in subconfluent cultures. This increase was also abrogated by PD98059. These data indicate that in primary rat hepatocyte cultures, 1) the phosphoinositol 3-kinase pathway, perhaps through p70s6k activation, regulates DNA synthesis in response to insulin and EGF; 2) the MAPKpathway is not involved in insulin- and EGF-induced DNA synthesis; and 3) p44/42 MAPKs are involved the induction of c-myc mRNA levels, although this induction is not required for DNA synthesis. These studies define two distinct signal transduction pathways that independently mediate growth-related responses in a physiologically relevant, normal cell system.     

Immunohistochemical analysis of p53, cyclinD1, RB1, c-fos and N-ras gene expression in hepatocellular carcinoma in Iran

AIM： TO study the effect of some genes especially those involved in cell cycle regulation on hepatocellular carcinoma.
METHODS： Paraffin-embedded tissue samples of 25 patients （18 males and 7 females） with hepatocellular carcinoma were collected from 22 pathology centers in Tehran during 2000-2001, and stained using immunohistochemistry method （avidin-biotin-peroxidase） for detection of p53, cyclinD1, RB1, c-los and N-ras proteins. RESULTS： Six （24%）, 5 （20%）, 12 （48%） and 2 samples （8%） were positive for p53, cyclinDl, C-los and N-ras expression, respectively. Twenty-two （88%） samples had alterations in the （31 cell-cycle checkpoint protein expression （RBI or cyclinD1）. P53 positive samples showed a higher （9 times） risk of being positive for RBI protein than p53 negative samples. Loss of expression of RBI in association with p53 over-expression was observed in 4 （66.7%） of 6 samples. Loss of expression of RBI was seen in all cyclinD1 positive, 20 （90.9%） N-ras negative, and ii （50%） C-fos positive samples, respectively. CyclinD1 positive samples showed a higher （2.85 and 4.75 times） risk of being positive for c-los and N-ras expression than cyclinD1 negative samples.
CONCLUSION： The expression of p53, RB1 and c-los genes appears to have a key role in the pathogenesis of hepatocellular carcinoma in Iran. Simultaneous overexpression of these genes is significantly associated with their loss of expression during development of hepatocellular carcinoma.