Wip1在肺癌细胞中的作用机制初探

目的: 检测Wip1及相关蛋白在肺癌细胞中的表达情况,探讨Wip1在肺癌发生中的作用机制。方法: Western blotting检测各种细胞(肺腺癌细胞A549、肺鳞癌细胞NCI-1299、大细胞肺癌细胞 NCI-H460和正常支气管上皮细胞HBE)中Wip1、 p53、p-p53、p38 MAPK和p-p38 MAPK蛋白的表达。结果: A549、NCI-1299和H460细胞中Wip1蛋白的表达均高于HBE细胞(P<0.05);各种肺癌细胞间Wip1蛋白的表达无明显差异(P>0.05);p-p53和p-p38 MAPK蛋白在肺癌细胞中的表达低于HBE细胞(P<0.05);肺癌细胞中Wip1表达增加,p-p38 MAPK和p-p53表达降低,存在着Wip1-p38 MAPK-p53信号通路的失衡。结论: 肺癌细胞(A549、NCI-1299、H460)中存在Wip1-p38 MAPK-p53信号通路的失衡。这可能是Wip1在肺癌中的致癌机制之一。     

PPM1D dephosphorylates Chk1 and p53 and abrogates cell cycle checkpoints

The ATM (ataxia-telangiectasia mutated) and ATR (ataxia-telangiectasia and Rad3-related) kinases respond to DNA damage by phosphorylating cellular target proteins that activate DNA repair pathways and cell cycle checkpoints in order to maintain genomic integrity. Here we show that the oncogenic p53-induced serine/threonine phosphatase, PPM1D (or Wip1), dephosphorylates two ATM/ATR targets, Chk1 and p53. PPM1D binds Chk1 and dephosphorylates the ATR-targeted phospho-Ser 345, leading to decreased Chk1 kinase activity. PPM1D also dephosphorylates p53 at phospho-Ser 15. PPM1D dephosphorylations are correlated with reduced cellular intra-S and G2/M checkpoint activity in response to DNA damage induced by ultraviolet and ionizing radiation. Thus, a primary function of PPM1D may be to reverse the p53 and Chk1-induced DNA damage and cell cycle checkpoint responses and return the cell to a homeostatic state following completion of DNA repair. These homeostatic functions may be partially responsible for the oncogenic effects of PPM1D when it is amplified and overexpressed in human tumors.     

Wip1基因沉默对结肠癌细胞化疗敏感性的影响

目的:观察靶向Wip1基因的特异性siRNA序列对结肠癌细胞Wip1基因的抑制效应,探讨Wip1基因沉默对结肠癌细胞化疗敏感性的影响。方法:将Wip1-811 siRNA转染入Wip1高表达的RKO结肠癌细胞株,采用real-time PCR法检测Wip1 mRNA的表达,采用Western blotting方法检测Wip1蛋白表达,采用MTS方法检测结肠癌细胞活力,流式细胞术检测细胞凋亡及细胞周期。结果:Wip1-811 siRNA明显抑制Wip1的表达。抑制Wip1基因表达后,转染组RKO结肠癌细胞对抗肿瘤药物的敏感性增加,5-氟尿嘧啶处理组RKO结肠癌细胞活力由(89.4±6.6)%降至(74.7±3.9)%(P0.05),奥沙利铂处理组细胞活力由(77.9±2.4)%降至(66.7±2.9)%(P0.05)。转染Wip1-811 siRNA后,5-氟尿嘧啶处理组细胞凋亡比例由(7.7±0.5)%升至(12.3±3.2)%(P0.05);奥沙利铂处理组细胞凋亡比例由(14.7±2.1)%升至(34.0±2.1)%(P0.05)。结论:沉默Wip1基因表达能增强结肠癌细胞的化疗敏感性。     

Exosomal miR-155-5p promotes proliferation and migration of gastric cancer cells by inhibiting TP53INP1 expression

Exosomal microRNA (miRNA) secreted by tumor cells plays an important biological role in tumorigenesis and development. We aimed to explore the effects of exosomal miR-155-5p in gastric cancer (GC) and understand its mechanism of action in GC progression. We isolated exosomes from the human gastric mucosal epithelial cell line GES-1 and gastric cancer cell line AGS, and then identified them according to their surface markers by flow cytometry. Later, we detected the miR-155-5p expression levels in tissues and isolated exosomes using RT-qPCR. Bioinformatics analysis showed that miR-155-5p directly binds to the 3' untranslated region (3'-UTR) of tumor protein p53-induced nuclear protein 1 (TP53INP1) mRNA. We also investigated whether the miR-155-5p-rich exosomes caused changes in cell cycle, proliferation, and migration in AGS cells. In this study, we found that the levels of miR-155-5p were significantly increased in GC tissues and AGS cells, and that the TP53INP1 protein level was downregulated in GC tissues using IHC and IFC. TP53INP1 was found to be directly regulated by miR-155-5p following a dual luciferase-based reporter assay. After co-culturing with the isolated miR-155-5p-rich exosomes, the proliferation and migration capabilities of AGS cells were enhanced. Thus, our results reveal that exosomal miR-155-5p acts as an oncogene by targeting TP53INP1 mRNA in human gastric cancer.     

Chk2/hCds1 functions as a DNA damage checkpoint in G(1) by stabilizing p53

Chk2/hcds1, the human homolog of the Saccharomyces cerevisiae RAD53/SPK1 and Schizosaccharomyces pombe cds1 DNA damage checkpoint genes, encodes a protein kinase that is post-translationally modified after DNA damage. Like its yeast homologs, the Chk2/hCds1 protein phosphorylates Cdc25C in vitro, suggesting that it arrests cells in G(2) in response to DNA damage. We expressed Chk2/hCds1 in human cells and analyzed their cell cycle profile. Wild-type, but not catalytically inactive, Chk2/hCds1 led to G(1) arrest after DNA damage. The arrest was inhibited by cotransfection of a dominant-negative p53 mutant, indicating that Chk2/hCds1 acted upstream of p53. In vitro, Chk2/hCds1 phosphorylated p53 on Ser-20 and dissociated preformed complexes of p53 with Mdm2, a protein that targets p53 for degradation. In vivo, ectopic expression of wild-type Chk2/hCds1 led to increased p53 stabilization after DNA damage, whereas expression of a dominant-negative Chk2/hCds1 mutant abrogated both phosphorylation of p53 on Ser-20 and p53 stabilization. Thus, in response to DNA damage, Chk2/hCds1 stabilizes the p53 tumor suppressor protein leading to cell cycle arrest in G(1).     

原癌基因Wip1在室管膜瘤中表达增加并与P53相关

目的 探讨野生型P53-诱导的蛋白磷酸酶1(Wip1)在室管膜瘤中的表达及其与P53相关性.方法 用免疫组织化学、反转录聚合酶链反应(RT-PCa)和Western blot 方法检测31例室管膜瘤及10例正常脑组织中Wip1mRNA、蛋白表达.并用免疫组化检测P53.同时,回顾性分析临床病理因素与Wipl表达之间的相...     

二烯丙基二硫化物对人胃癌MGC803细胞G2/M期检查点激酶Chk1/2的影响

目的： 观察二烯丙基二硫化物（DADS）对人胃癌MGC803细胞的细胞周期检查点激酶1（Chkl）和细胞周期检查点激酶2(Chk2)的影响。方法：RT-PCR检测MGC803细胞的Chk1和Chk2激酶在mRNA水平的改变;Western blotting 检测Chk1、Chk2的表达和Chk1、Chk2的磷酸化程度,免疫共沉淀检测Chk1、Chk2与细胞分裂周期蛋白25C（Cdc25C）结合情况。结果：RT-PCR检测显示,Chkl和Chk2 mRNA水平在处理组与未处理组之间无明显差异（P>0.05）。Western blotting 检测显示,MGC803细胞分别受30 mg·L-1 DADS刺激1 h和2 h后,与未处理组相比,总Chk1和Chk2蛋白表达在细胞处理前后均无明显改变（P>0.05）;但处理组细胞Chk1磷酸化程度明显增加,并呈时间依赖性（P<0.01）,而Chk2在处理组与未处理组间磷酸化程度无明显差异（P>0.05）。免疫共沉淀分析表明,MGC803细胞中DADS能促进Chk1与Cdc25C结合,而对Chk2与Cdc25C结合无影响。结论：DADS可能是通过激活Chk1引起人胃癌MGC803细胞G2/M期阻滞。     

Wip1在非小细胞肺癌组织及细胞中的表达

目的： 检测肺癌组织和3种肺癌细胞中Wip1的表达水平,探讨肺癌中Wip1的表达水平与其各种临床病理特征之间的关系。方法: 利用实时荧光定量PCR检测44例肺癌及相应正常肺组织中Wip1 mRNA的表达,分析Wip1 mRNA表达与各临床病理参数之间的关系;利用实时荧光定量PCR的方法检测人肺腺癌细胞A549、人鳞癌细胞NCI-1299、人大细胞肺癌细胞NCI-H460和人正常支气管上皮细胞HBE中Wip1 mRNA的表达量,进行相对定量分析。结果: 44例非小细胞肺癌及相应正常肺组织均有Wip1 mRNA的表达,其中17例肺癌中Wip1 mRNA高表达,占38.6%,两者表达差异显著(ratio=2.1644±1.3940,P＜0.05);分化程度低的肿瘤细胞Wip1 mRNA表达量显著高于分化程度高者（P<0.05）。3种肺癌细胞中的Wip1 mRNA表达量显著高于正常支气管上皮细胞,差异显著(均P＜0.05)。结论: Wip1mRNA在非小细胞肺癌中过表达,可能与肿瘤发生有关,有望成为非小细胞肺癌基因治疗的新靶点。Wip1 mRNA在非小细胞肺癌中的表达与肿瘤细胞分化程度有关,可能成为确定肿瘤恶性程度的分子生物学参考指标。     

Wip1相关研究进展

正Fiscella等~([1])首次通过γ射线或UV射线诱导发现了野生型p53诱导的磷酸酶1(wild-type p53-induced phosphatase 1,Wip1),并且证实Wip1的表达依赖于p53。编码Wip1蛋白的基因称为PPM1D,定位于人染色体17q23和小鼠第11号染色体上,PPM1D编码的mRNA在很多器官组织包括睾丸和     

STC1在胃癌组织与外周血液中表达的意义

目的：研究外周血液与胃癌组织中斯钙素1 (STC1)的表达情况。方法: 分别在I-IV型的胃癌74例患者中，应用RT-PCR法检测外周血和肿瘤组织中STC1 mRNA表达情况，应用免疫组化法检测肿瘤组织中STC1蛋白表达情况。结果: 74例胃癌患者，48例外周血液中STC1 mRNA阳性；肿瘤组织STC1 mRNA与STC1蛋白全部表达。外周血中STC1 mRNA与肿瘤淋巴结转移数、肿瘤大小和病理TNM分期有(r分别为0.637、0.519、0.541, P<0.05、P<0.01、P<0.05)显著正相关。结论: STC1在胃癌的发生发展过程中具有抑制免疫系统功能等重要作用；外周血中STC1 mRNA检测可试用作为肿瘤微转移的1个新指标。     

原癌基因Wip1的研究进展

细胞DNA总是受到来自环境和内源性致突变因素攻击.为保持基因组的完整性和抑制肿瘤发生,细胞在长期检查点机制.     

Prognostic implications of cyclin B1, p34cdc2, p27(Kip1) and p53 expression in gastric cancer

PURPOSE: Cell cycle progression is regulated by interactions of specific cyclins and cyclin dependent kinases (CDKs) at the G1-S and G2-M checkpoints and cell cycle deregulation plays a major role in carcinogenesis of human cancers. PATIENTS AND METHODS: To investigate the role of cell cycle regulators in the pathogenesis and progression of human gastric cancers, 23 cases of gastric carcinomas were examined for the expression of cyclin B1, p34cdc2, p27(Kip1) and p53 by immunohistochemical methods, and gene expression was correlated with various clinicopathologic findings. RESULTS: Out of 23 cases studied, cyclin B1 was diffusely expressed in 20 cases (87.0%), p34cdc2 in 14 cases (60.9%) and p53 in 12 cases (52.2%), whereas in normal gastric tissues, cyclin B1 and p34cdc2 were weakly expressed and p53 was not expressed. In contrast, p27(Kip1) was expressed in only 8.7% of gastric carcinomas compared with 78.3% of normal gastric tissues. There was correlation between the expression of cyclin B1 and expression of p34cdc2 (p=0.002), between the expression of cyclin B1 and loss of p27(Kip1) (p=0.025), and between the expression of p34cdc2 and loss of p27(Kip1) (p=0.065). In addition, expression of cyclin B1 was correlated with regional lymph node metastasis (p=0.032). CONCLUSION: Our results indicate that cyclin B1 and p34cdc2 are involved in the genesis or progression of gastric cancers. Furthermore, overexpression of cyclin B1 may play an important role in lymph node metastatic potential of gastric cancer. Thus, abnormal expression of cyclin B1 and CDKs, overexpression of p53 and loss of p27(Kip1) expression may play important roles in human gastric carcinogenesis.     

1α,25（OH）2D3通过阻滞细胞周期抑制胃癌细胞系增殖简

 目的 研究1α,25(OH) 2D3对胃癌细胞增殖和细胞周期的影响,并探讨其相关的作用机制。方法 BGC-823和SGC-7901胃癌细胞株分别给予终浓度为10-10~10-7mol/L的1α,25(OH) 2D3处理72h,用MTT法检测细胞抑制率;用流式细胞仪检测细胞周期;用RT-qPCR技术检测细胞周期相关基因P21、cyclinD1、cyclinE1和CDK6 mRNA表达。 结果1α,25(OH) 2D3对胃癌细胞的增殖抑制率具有浓度依赖性, 1α,25(OH) 2D3干预导致BGC-823和SGC-7901细胞株G1期细胞比例升高,S期细胞比例降低 (P<0.05); 1α,25(OH) 2D3干预后,BGC-823和SGC-7901胃癌细胞P21 mRNA表达升高(P<0.01),而cyclinD1、cyclinE1和CDK6 mRNA表达降低(P<0.01)。结论 1α,25(OH) 2D3抑制胃癌细胞增殖,诱导细胞周期阻滞,可能与上调P21,下调cyclinD1、cyclinE1和CDK6的表达有关。     

Expression of DNA damage checkpoint 53BP1 is correlated with prognosis,cell proliferation and apoptosis in colorectal cancer

53BP1, an important mediator of DNA damage checkpoint, plays an essential role in maintaining the cell genome stability, and the aberrant expression of 53BP1 was found to contribute to tumor occurrence and development. In this study, we explored the clinical significance of 53BP1 expression in colorectal cancer and investigated the effects of 53BP1 expression on tumor cell proliferation and apoptosis and its possible mechanisms. Immunohistochemical analysis was performed to detect the expression of 53BP1 in 95 cases of tumor tissues. After establishment of shRNA-mediated knockdown stable HCT-116 cell lines, cell proliferation, apoptosis and cell cycle distribution were detected by MTT and flow cytometry, and expression of up-and down-steam related proteins as γ-H2AX, CHK2 and P53 were tested by Western blot. 53BP1 intensity was found to be associated with tumor location (P < 0.05), and the low expression of 53BP1 revealed decreased survival time compared with high expression in subgroups as male, tumor size > 5 cm, tumor located at right side, T stage as T3-T4, N0, clinical stage as I-II (P < 0.05). In vitro, shRNA-mediated loss of 53BP1 obviously inhibited HCT-116 tumor cell apoptosis, promoted cell proliferation and increased accumulation of cells in S phase. Meanwhile, the expression of γ-H2AX, CHK2 and P53 was significantly reduced (P < 0.05). Our findings suggest 53BP1 may serve as a candidate biomarker for predicting prognosis and disease development in colorectal cancer.     

Tissue-specific regulation of Chk1 expression by p53

The regulation of Chk1, a critical protein kinase involved in G(2) phase arrest, has been a subject of recent research. Chk1 phosphorylates tumor suppressor p53 at multiple sites, while p53 has been shown to downregulate Chk1 expression under stress conditions in vitro, suggesting negative feedback between the two checkpoint proteins. Using the p53 knockout mouse model, we demonstrate by Western blot and immunohistochemistry that mChk1 expression is induced in spleen, thymus, and dermal fibroblasts and is reduced in lung and testis in p53(-/-) mice compared to p53(+/+) controls. The mChk1 protein was undetectable in heart, kidney, and skin, whereas abundant expression was observed in brain and liver in both p53(+/+) and p53(-/-) mice. These data indicate that p53 regulates Chk1 expression in a tissue-specific manner.     

Membrane-type 1 matrix metalloproteinase enhances lymph node metastasis of gastric cancer

The mechanisms of the lymph node metastasis remain unclear. We demonstrate the role of MT1-MMP on the lymph node metastasis using in vivo experimental model of lymph node metastasis by orthotopic implantation of MT1-MMP transfected gastric cancer cell line in the stomach of nude rats. TMK-1 cell line without expression of MT1-MMP was transfected with the pcDNA3 plasmid containing a 3.4-kb MT1-MMP cDNA fragment by calcium phosphate method, and the transfected cell line was designated as TMK-MT. Western blot and RT-PCR analyses showed the specific bands corresponding to MT1-MMP in the TMK-MT cells. By gelatin zymography, the activated form (62-kDa) of MMP-2 was identified in the medium of TMK-MT cell line, but was not detected in TMK-1 cells. Six weeks after orthotopic implantation of TMK-1 and TMK-MT xenografts of nude mouse-subcutaneus tumor into the stomach of nude rats, gastric tumors were found in all the animals. Histologically, the lymphatic invasion was found in the submucosa of the TMK-MT gastric tumors. Lymph node metastasis was not detected in nude rats bearing TMK-1 gastric tumor (0/8). In contrast, lymph node metastasis was detected in five out of 8 rats, bearing TMK-MT gastric tumor. MT1-MMP immunoreactivity was found on the cell membrane and cytoplasm of TMK-MT cells not only in the lymph node metastasis but also in the stomach tumor. These results suggest that MT1-MMP overexpression induced by transfection of its gene may promote lymph node metastasis of transformed cells. This revised version was published online in July 2006 with corrections to the Cover Date.