p21和p27基因多态性与肿瘤的相关性

做为细胞周期依赖性蛋白激酶抑制剂，p21和p27被认为是侯选的抑癌基因，在细胞周期的调控中发挥重要作用。p21和p27基因的突变或多态性可能与人类多种肿瘤的发生发展有关。研究该二基因的多态性可能有助于判断肿瘤的发病风险、临床特征以及预后。     

肿瘤中p16基因的研究进展

ｐ１６基因是细胞周期蛋白依赖性激酶抑制因子,它作为一种细胞周期调节因子,通过参与细胞周期的调节,广泛的参与肿瘤的发生,本以ｐ１６基因在肿瘤研究中进展作一综述。     

沉默ClC-3氯通道基因对HeLa细胞周期分布的影响

目的:探讨沉默HeLa细胞的ClC-3氯通道基因后细胞周期分布的变化及其作用机制。方法:依照siRNA设计原则构建沉默ClC-3基因的ClC-3 siRNA并转染HeLa细胞;实验分为空白对照组(control组)、转染试剂对照组(Lipo组)、阴性对照组(negative siRNA组)和ClC-3 siRNA组。采用real-time PCR检测ClC-3 siRNA的沉默效率;流式细胞术检测细胞周期分布情况;Western blot检测ClC-3蛋白及相关细胞周期蛋白(cyclin)D1、细胞周期蛋白依赖激酶(cyclin-dependent kinase,CDK)4、CDK6、P21和P27等表达。结果:CIC-3 siRNA成功沉默HeLa细胞的ClC-3基因。和其它组相比,ClC-3 siRNA组的细胞周期被阻抑在G_0/G_1期。CIC-3 siRNA组的cyclin D1、CDK4和CDK6蛋白表达水平明显下降,P21和P27蛋白表达水平明显上升。结论:沉默HeLa细胞ClC-3氯通道基因可影响cyclin D1、CDK4、CDK6、P21和27蛋白的表达水平胆抑HeLa细胞周期停滞在G_0/G_1期。     

肿瘤中p16基因的研究进展

ｐ１６基因是细胞周期蛋白依赖性激酶抑制因子（ＣＤＫ４Ｉ）。它作为一种细胞周期调节因子,通过参与细胞周期的调节,广泛的参与肿瘤的发生。本文对ｐ１６基因在肿瘤研究中的进展作一综述。     

Skp2与肿瘤关系研究进展

Skp2蛋白属于F-box蛋白家族成员之一,在SCFSkp2 E3泛素连接酶复合体中负责对底物的识别。Skp2介导许多蛋白通过泛素化依赖的蛋白酶体途径进行降解,其中包括P27、P21等细胞周期负调控蛋白。研究发现Skp2的过表达与许多肿瘤的发生、发展和预后密切相关,其可能作为肿瘤治疗的一个新靶点。     

p16基因与人类肿瘤

p16基因位于人类染色体9P21，其编码蛋白特异性抑制CDK4和CDK6的活性．参与正常细胞周期的调控。在肿瘤中，p16基因存在广泛而频繁的缺失和突变，被认为是新的抑癌基因，成为当前肿瘤研究的一个热点。     

氯喹对人肺癌A549细胞周期阻滞及增殖抑制的机制

目的 探讨氯喹抑制人非小细胞肺癌A549细胞增殖、促进凋亡、阻滞细胞周期的作用及其分子机制。 方法 应用MTT法和流式细胞术分别检测氯喹对A549细胞增殖、细胞凋亡和细胞周期的影响;Western blotting检测氯喹对A549细胞周期蛋白(cyclin E1)和细胞周期蛋白依赖性激酶（CDK2）、肿瘤抑制蛋白PTEN以及细胞周期抑制蛋白P21、P27表达水平的影响。 结果 氯喹能够抑制A549细胞增殖,并且具有时间-剂量依赖性。氯喹可以诱导细胞凋亡,不同浓度的氯喹作用于A549细胞24h后,细胞凋亡率随着作用剂量的增加而升高。进一步的研究发现,氯喹还能够阻滞细胞周期于G₀/G₁期,降低cyclinE1和CDK2表达水平,明显提高PTEN、P21和P27的表达水平。 结论 氯喹具有抑制肺癌细胞增殖、促进其凋亡和阻滞细胞周期的作用,其机制可能与其抑制CyclinE1和CDK2表达,并且上调PTEN、P21和P27蛋白的表达有关。     

抑癌基因P16,P15与泌尿系肿瘤

P16、P16是近年来发现新的抑癌基因 ,在很多人类原发性肿瘤和细胞株中有高频率的缺失突变。基蛋白产物通过特异性抑制细胞周期依赖激酶 ,而参与多数恶性肿瘤的发生过程。所以 ,P16 / 15基因已成为分子生物学 ,分子遗传学 ,临床医学等各领域专家研究的热点之一。1　 P16和 P15基因的发现与结构1993年 Serrano等发现了特异抑制细胞周期蛋白依赖性激酶 4( cyclin dependent kinase4,CDK4)的 P16蛋白 ,并克隆了 P16的 c DNA。 1994年美国的 Beach研究小组用 P16的 c DNA为探针 ,从 TGF-β阻断的 Ha Ca T细胞 c DNA文库中克隆出 P16…     

p27^kip1的功能研究及其与肿瘤的关系

p2 7kip1是细胞周期蛋白依赖性激酶抑制剂 ,具有多种生物学功能。它参与调控细胞周期 ,调节细胞凋亡 ,增强细胞间的粘附 ,诱导细胞分化等。p2 7kip1基因被认为是候选的肿瘤抑制基因 ,其表达下降与肿瘤的发生、侵袭密切相关 ,可作为某些肿瘤预后的独立判定指标。     

鼻咽癌患者p16基因表达分析

p16是位于 9p2 1的多重肿瘤抑制基因 ,编码一个由 148个氨基酸组成、分子量为 16 kb的蛋白质 ,其对细胞的生长起负性调控作用[1 ] 。 p16的缺失或突变与恶性肿瘤的发生、发展关系是目前肿瘤的研究热点。据报道 ,人类 75 %的癌细胞株有 p16基因的缺失或突变 ,超过了 p5 3基因 5 0 %的突变率。其翻译产物 P16蛋白与 P5 3蛋白也不同 ,它是直接作用于细胞周期的抑癌细胞 ,将细胞周期控制和癌基因这两个曾经独立研究领域连接在一起 ,可能成为癌症基因治疗的新的目的基因 [2 ] 。近年来 ,在基因水平上对 p16基因的研究和对 p16基因产物 P16蛋白…     

Aberrant DNA methylation of cyclin D2 and p27 genes in rodent pituitary tumor cell lines correlates with specific gene expression

We previously reported that increased DNA methylation was an important mechanism of silencing the p27 gene in some pituitary tumor cell lines [1]. DNA methylation correlated inversely with p27 gene expression. The p27 and cyclin D2 genes are located in the same region of mouse chromosome 6, rat chromosome 4, and human chromosome 12p13. Because both genes are located in the same gene cluster, we investigated whether methylation was a principal mechanism regulating cyclin D2 as well as p27 expression in rodent pituitary cell lines. Bisulfite genomic sequencing showed that the normally unmethylated cytosines of the p27 gene in normal pituitary (NP) were extensively methylated in GH3 and GHRH-CL1 cells, but not in AtT 20, αT₃-1 and LβT₂ cells; but cyclin D2 was extensively inactivated in various pituitary tumor cell lines by increased DNA methylation. These abnormalities of methylation in p27 and cyclin D2 genes occurred with different frequencies in five pituitary tumor cell lines with 100% (5/5) methylation of the cyclin D2 gene and 40% (2/5) methylation of the p27 gene. Treatment with the methyl transferase inhibitor 5′-aza-2′-deoxycytidine (AZAdC) increased expression of cyclin D2 and p27 in GH3 and GHRH-CL1 pituitary tumor cells. There was a correlation between hypermethylation and gene expression. GH₃ tumors implanted into Wistar-Furth rats in vivo did not change the methylation status of the p27 and cyclin D2 genes. These data indicate a coordinately reduced expression of these two linked genes in most rodent pituitary tumor cell lines and suggest that methylation of cyclin D2 and p27 might occur in a “hot spot” in this gene-rich cluster. Supported in part by NIH CA 37231 and CA 42951     

p27kip1: a multifunctional cyclin-dependent kinase inhibitor with prognostic significance in human cancers

p27kip1 (p27) is a member of the universal cyclin-dependent kinase inhibitor (CDKI) family. p27 expression is regulated by cell contact inhibition and by specific growth factors, such as transforming growth factor (TGF)-beta. Since the cloning of the p27 gene in 1994, a host of other functions have been associated with this cell cycle protein. In addition to its role as a CDKI, p27 is a putative tumor suppressor gene, regulator of drug resistance in solid tumors, and promoter of apoptosis; acts as a safeguard against inflammatory injury; and has a role in cell differentiation. The level of p27 protein expression decreases during tumor development and progression in some epithelial, lymphoid, and endocrine tissues. This decrease occurs mainly at the post-translational level with protein degradation by the ubiquitin-proteasome pathway. A large number of studies have characterized p27 as an independent prognostic factor in various human cancers, including breast, colon, and prostate adenocarcinomas. Here we review the role of p27 in the regulation of the cell cycle and other cell functions and as a diagnostic and prognostic marker in human neoplasms. We also review studies indicating the increasingly important roles of p27, other CDKIs, and cyclins in endocrine cell hyperplasia and tumor development.     

Discovery of an oncogenic activity in p27Kip1 that causes stem cell expansion and a multiple tumor phenotype

The cell cycle inhibitor p27Kip1 also has cyclin-cyclin-dependent kinase (CDK)-independent functions. To investigate the significance of these functions in vivo, we generated a knock-in mouse in which four amino acid substitutions in the cdkn1b gene product prevent its interaction with cyclins and CDKs (p27CK-). In striking contrast to complete deletion of the cdkn1b gene, which causes spontaneous tumorigenesis only in the pituitary, the p27CK- protein dominantly caused hyperplastic lesions and tumors in multiple organs, including the lung, retina, pituitary, ovary, adrenals, spleen, and lymphomas. Moreover, the high incidence of spontaneous tumors in the lung and retina was associated with amplification of stem/progenitor cell populations. Therefore, independently of its role as a CDK inhibitor, p27Kip1 promoted stem cell expansion and functioned as a dominant oncogene in vivo. Thus, the p27CK- mouse unveils a dual role for p27 during tumorigenesis: It is a tumor suppressor by virtue of its cyclin-CDK regulatory function, and also an oncogene through a cyclin-CDK-independent function. This may explain why the cdkn1b gene is rarely inactivated in human tumors, and the p27CK- mouse in which the tumor suppressor function is lost but the cyclin-CDK-independent-oncogenic-function is maintained may represent a more faithful model for the widespread role of p27 misregulation in human cancers than the p27 null.     

PTEN及p27Kip1在子宫内膜癌中的研究进展

肿瘤抑制基因PTEN被称为子宫内膜的看家基因,许多学者提出PTEN基因在子宫内膜癌发生发展中起重要作用。另一个肿瘤抑制基因p27在子宫内膜癌的预后中具有重要的作用。现就PTEN 、p27基因在子宫内膜癌中的表达及其与子宫内膜癌发生、发展的关系以及在治疗和预后方面的研究进展进行综述。     

Skp2 expression is associated with down-regulation of p27 protein and cell proliferation in salivary adenoid cystic carcinoma

Adenoid cystic carcinoma (ACC) is a malignant salivary gland tumor, which shows frequent recurrence and metastasis, ultimately with a poor outcome. We previously demonstrated that p27 down-regulation is frequently found and is due to an enhancement of its degradation in ACC. In this study, we transfected nondegradable p27 mutant (T187A) and wild-type gene into ACC cell line. Transfection of T187A mutant gene was more effective on inhibition of cell growth of ACC cells, suggesting that aberration of p27 degradation may be present in ACC. As F-box protein S-phase kinase-associated protein 2 (Skp2), which is necessary for ubiquitin-mediated degradation of p27, is involved in p27 down-regulation in various cancers, we examined the Skp2 expression and its association with p27 expression in 50 ACC cases. We found Skp2 expression in 36% of ACC cases and inverse association between the expression of Skp2 and p27. Moreover, Skp2 small interfering ribonucleic acid (siRNA) transfection decreased Skp2 protein and accumulation of p27 protein and inhibited the cell growth of ACC cells in vitro. These findings, overall, suggest that Skp2 may play an important role in ACC development through the down-regulation of p27 and that Skp2 siRNA can be a novel modality of cancer gene therapy for suppression of p27 down-regulation in ACC.     

Down-Regulation of p27 Is Associated with Development of Colorectal Adenocarcinoma Metastases

The cyclin-dependent kinase inhibitor p27 is a negative regulator of the cell cycle and a potential tumor suppressor gene. Because we had previously demonstrated that loss of p27 protein is associated with aggressive behavior in colorectal adenocarcinomas, we used immunohistochemistry and in situ hybridization to evaluate the potential role of alterations in p27 expression in primary and metastatic colorectal adenocarcinomas. Parallel immunostaining was performed for Ki-67 and p53. We evaluated 13 cases of metachronous and 23 cases of synchronous primary and metastatic colorectal tumor pairs. In the synchronous subgroup (Stage IV tumors), 57% of the primary tumor and metastases pairs did not express p27 protein and the remainder were low expressors. In the metachronous subgroup, 54% of the primary tumors were low expressors and the remainder high expressors of p27 protein. There was a significant reduction in the expression of p27 in the metachronous metastases (mean positive cells: 14.5%) when compared to the corresponding primary tumors (mean positive cells: 41.8%), P = 0.0023. All the primary and metastatic tumors in the metachronous subgroup showed high levels of p27 mRNA expression. There was no association between loss of p27 and either Ki-67 count or p53 expression. Because p27 is known to be up-regulated when epithelial cells are grown in suspension, the down-regulation of p27 in circulating tumor cells may confer the ability to grow in an environment of altered extracellular matrix or intercellular adhesion properties, two situations which may facilitate metastases.     

P27Kip1 expression and survival in NO gastric carcinoma

p27Kip1, a cyclin-dependent kinase inhibitor, is considered to be a tumor suppressor gene. Absent or reduced expression of the p27Kip1 protein has been reported being a negative prognostic marker in primary lung, breast, colon, bladder, and prostate carcinomas. p27Kip1 protein expression was evaluated in a series of 96 gastric carcinomas with no lymph node involvement (NO) to verify any impact on the clinical outcome. The analysis also considered the classic clinico-pathological parameters, such as age, sex, and depth of tumor invasion (pT). The most widely used classification systems for gastric carcinoma were adopted. The expression of p27pKip1 was related neither to the pT category nor to tumor histology. Kaplan-Meier analysis documented a significant impact of an advanced pT category (p < 0.0001) and p27Kip1-reduced expression (p < 0.0002) on survival. Multivariate analysis confirmed that the reduced p27Kip1 protein expression was a strong independent predictor of poor outcome, ranking second to the pT category only (p < 0.006 and p < 0.004 respectively). As reported for other neoplasms, the expression of p27Kip1 appears to be associated with the clinical outcome of gastric carcinoma.     

p27Kip1 localization depends on the tumor suppressor protein tuberin

p27(Kip1) plays an important role in cell cycle regulation by inhibiting cyclin-CDK complex activity in the nucleus. p27(Kip1) is regulated by its concentration as well as by its subcellular localization. Tuberin, encoded by the tuberous sclerosis tumor suppressor gene TSC2, is a potent negative cell cycle regulator. We show herein, that tuberin induces nuclear p27 localization by inhibiting its 14-3-3-mediated cytoplasmic retention. Tuberin interferes with 14-3-3's counteracting effects on p27-mediated cell cycle arrest. Akt-mediated phosphorylation of p27, but not of tuberin, negatively regulates tuberin's potential to trigger p27 nuclear localization. In G0 cells, tuberin binds p27 triggering downregulation of p27's binding to 14-3-3 and of its cytoplasmic retention. At transition to S phase p27 is phosphorylated by Akt, tuberin/p27 complex levels are downregulated and binding of p27 to 14-3-3 increases triggering cytoplasmic retention of p27. These findings demonstrate p27 localization during the mammalian cell cycle to be under the control of the tumor suppressor tuberin.     

Methylation analysis of cyclin-dependent kinase inhibitor genes in primary gastrointestinal lymphomas.

The CIP/KIP family of cyclin-dependent kinase inhibitors may act as tumor suppressors. To assess promoter hypermethylation as a potential underlying mechanism for loss of expression, methylation-specific polymerase chain reaction for p21 and p27 genes was performed in 13 gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphomas, 13 gastric high-grade B-cell lymphomas, and 14 intestinal diffuse large B-cell lymphomas. p21 and p27 genes were unmethylated in normal Peyer's patch and tonsillar tissues. Promoter hypermethylation of p21 gene was detected only in some gastric low-grade MALT lymphomas (4/13, 31%). All gastric and intestinal high-grade lymphomas revealed unmethylated status of p21 gene. p27 gene was unmethylated in all cases of low- and high-grade gastrointestinal lymphomas. These results suggest that p21 promoter methylation is involved in some low-grade MALT lymphomagenesis in stomach and seems to be an early event in the gastric lymphomagenesis. And promoter methylation is not the underlying mechanism for loss of p27 protein expression in the malignant lymphomas of the stomach and intestine.     

p27 Expression, a cyclin dependent kinase inhibitor in breast carcinoma

p27 KIP1 is a cyclin dependent kinase inhibitor, which may act as a potential suppressor gene. Several lines of evidence support the hypothesis that reduced p27 KIP1 expression is related to uncontrolled cell proliferation and tumorigenesis. Low immunohistochemical expression of p27 KIP1 in human neoplasm seems related to tumor progression and poor prognosis. In breast cancer, low p27 is associated with high tumour grade and loss of oestrogen receptor, and it has been suggested that low p27 KIP1 is a powerful and independent prognostic marker of poor clinical outcome. There are however some discrepant results: a few studies, some of which conducted on large series of patients, do not support an independent role of p27 KIP1 as a prognostic marker. We are indeed faced with an intriguing hypothesis, but many more studies are needed to evaluate the real value of p27 KIP1 as a prognostic marker.