p53突变蛋白对人肺腺癌细胞中E-cadherin的表达调控及细胞迁移的影响

在人肺肿瘤细胞H1299中稳定表达含R273H点突变的p53蛋白(p53-R273H),观察到细胞中E-cadherin mRNA和蛋白水平下调,同时细胞迁移能力增强.免疫荧光方法检测发现p53-R273H显著降低E-cadherin在肿瘤细胞间的表达.这些结果表明p53-R273H突变蛋白具有下调E-cadherin基因的表达和促使肿瘤细胞迁移的新功能.     

组蛋白乙酰转移酶p300对人乳腺癌细胞迁移的影响

在人乳腺癌细胞MDA-MB-231中转染p300表达质粒过表达p300,及利用si RNA干扰技术下调p300的表达,以此研究组蛋白乙酰转移酶p300对肿瘤细胞迁移的影响.体外细胞划痕实验表明,过表达p300可以促进MDAMB-231细胞的迁移.RT-PCR和免疫印迹实验(Western blot)结果表明,过表达p300导致肿瘤迁移相关基因MYL9、CYR61和MYH9的m RNA和蛋白表达水平的上升.与过表达p300相反,干扰p300的表达引起肿瘤迁移相关基因MYL9、CYR61和MYH9的m RNA和蛋白表达水平的下调.     

CTCF通过抑制p53信号通路促进胆管癌细胞的生长、迁移和侵袭

为了探索CCCTC结合因子(CCCTC-binding factor, CTCF)对人胆管癌细胞的生长、迁移和侵袭能力的影响及其潜在的分子作用机制,利用慢病毒感染法获得稳定过表达或敲低CTCF的胆管癌细胞系,采用蛋白质免疫印迹法(Western blotting, Wb)检测CTCF蛋白表达水平,采用Cell Counting Kit-8(CCK-8)法和克隆形成实验检测细胞生长情况,采用Transwell小室实验检测细胞迁移和侵袭能力,采用GraphPad软件(v6)的Mann-Whitney U检验分析CTCF基因在癌和癌旁组织间的mRNA差异表达.结果显示:过表达CTCF可显著促进HCCC-9810和RBE胆管癌细胞的生长、迁移和侵袭能力;敲低CTCF呈现相反的表型.通过通路富集分析发现:CTCF的表达水平在胆管癌中与p53信号通路活性显著负相关,过表达CTCF可显著下调p53及其靶基因p21的mRNA和蛋白表达水平,而敲低CTCF则显著促进p53和p21的mRNA和蛋白表达水平.综上,本研究揭示CTCF可能通过抑制p53信号通路而促进胆管癌细胞生长、迁移和侵袭而发挥促癌基因的功能.     

茶溴香酰胺脂质体对黑色素瘤细胞生长和迁移的抑制作用

考察茶溴香酰胺脂质体(TBrC-L)对黑色素瘤B16细胞生长和迁移的抑制作用及其分子机制,为研发抗癌新药提供科学依据.采用MTT法和细胞划痕术探究TBrC-L对黑色素瘤B16细胞生长和迁移的影响; Hoechst 33258染色法观察药物作用下细胞凋亡形态的变化; Western Blotting检测TBrC-L对B16细胞生长、迁移和凋亡相关蛋白表达的影响.结果表明:TBrC-L能对B16细胞的生长和迁移产生显著性抑制作用,并且诱导其凋亡; TBrC-L可下调c-Met、HGF、Bcl-2、NF-κB和VEGFR2的表达,上调Caspase-3、E-cadherin、Bax、p53和Cytochrome c的表达,抑制HGF/Met/VEGFR2-NF-κB通路可能是TBrC-L抑制黑色素瘤B16细胞生长和迁移作用的重要分子机制.本研究结果提示,TBrC-L具有进一步开发为抗黑色素瘤药物的潜力.     

IRS1在藻蓝蛋白介导的H460细胞增殖和迁移调控中的作用

藻蓝蛋白来源于海洋藻类,是我国认可的食品着色剂和功能型食品．初期研究表明,藻蓝蛋白处理能抑制人类非小细胞肺癌系H460的体外增殖能力和迁移能力,使得其体外集落形成能力减弱．通过转录组学测序分析进一步探究具体作用机制,从藻蓝蛋白处理前后发生显著变化的基因中,筛选出了一个藻蓝蛋白处理后发生显著下调的基因,即胰岛素受体底物1（irs1）,并通过体外转染siRNA的方法抑制IRS1的表达,来研究其对非小细胞肺癌系H460的增殖和迁移能力的影响．采用MTT法检测细胞增殖,细胞划痕实验检测细胞迁移,克隆形成实验检测细胞集落形成能力,流式细胞术检测细胞周期分布．结果表明,下调IRS1的表达后,与对照组相比,细胞的生长速率降低,迁移能力、集落形成能力受到抑制,同时使细胞周期被阻滞到G1期．PI3K-AKT信号通路研究表明,藻蓝蛋白处理使得PI3K-AKT信号通路活性受到抑制,下调IRS1的表达使得PI3K-AKT信号通路部分蛋白表达也下调,通路活性受到一定程度抑制．本研究结果表明,藻蓝蛋白抑制非小细胞肺癌系H460体外活性功能的机制,可能与IRS1的表达和PI3K-AKT信号通路的活性有关,这为藻蓝蛋白的调控机制提供了有力的理论基础．      

抑癌基因p53与肿瘤发生及基因治疗的研究进展

概述了抑癌基因p53的结构和特性,以及p53的抑癌作用机理、基因治疗的研究进展.抑癌基因p53是人类细胞中非常重要的基因,野生型p53基因产物具有抑制肿瘤细胞增殖、诱导肿瘤细胞凋亡的作用.在p53基因发生突变或缺失时,可引起多种肿瘤.当人工将野生型p53基因与载体结合成重组DNA分子导入肿瘤患者体内后,有可能达到治疗恶性肿瘤的目的.     

山奈酚对人小细胞肺癌H446细胞凋亡的影响

研究山奈酚诱导人小细胞肺癌H446细胞凋亡的作用及可能的作用机制.采用MTT法检测山奈酚对小细胞肺癌H446细胞增殖的抑制作用;采用DAPI染色检测经山奈酚处理后细胞凋亡的形态变化;采用RT-PCR和Western-blot技术检测山奈酚处理前后H446细胞p53,bax,bcl-2 mRNA和蛋白的表达.结果显示,不同浓度的山奈酚能抑制人小细胞肺癌H446细胞生长,且随浓度增加抑制作用增强;H446细胞在山奈酚诱导下出现典型的凋亡形态;20μmol/L以上浓度的山奈酚处理后,p53,bax mRNA和相应蛋白表达均升高,而bcl-2 mRNA和蛋白表达降低.研究表明,山奈酚对H446细胞增殖有抑制作用,并能促进其凋亡.p53,bax和bcl-2在山奈酚诱导人小细胞肺癌H446细胞凋亡中起重要作用.     

MicroRNA-409-3p通过靶向ZEB1促进HCMV感染的胶质瘤细胞迁移的机制研究

近年来的临床研究显示人巨细胞病毒(HCMV)与神经胶质瘤关系密切,但HCMV促进胶质瘤进展的机制仍未阐明,而microRNA(miRNA)在神经胶质瘤中被检测到异常表达,因此提出潜伏感染的HCMV会通过调节宿主细胞miRNA从而影响神经胶质瘤发生发展的假设。首先通过转录组分析和细胞实验,证实miR-409-3p在HCMV感染后显著下调。生物信息学预测显示锌指结合蛋白1(ZEB1)为其下游靶基因。miR-409-3p过表达后的细胞划痕实验以及Transwell迁移实验证实,miR-409-3p的过表达会导致ZEB1下调并抑制胶质瘤U87细胞迁移,而外源性过表达ZEB1可恢复U87细胞迁移能力。研究结果表明,潜伏感染的HCMV能够通过下调宿主细胞中miR-409-3p,从而上调ZEB1表达,促进神经胶质瘤细胞迁移。     

茶氟香酰胺对人肝癌细胞生长和迁移的抑制作用

茶氟香酰胺(Ethyl 6-fluorocoumarin-3-carboxylyl L-theanine,TFC)是对茶氨酸进行结构优化后的产物,通过实验研究其对人肝癌细胞(SMMC7721)生长和迁移的抑制作用,并了解其作用机制.MTT和Transwell chamber法分别检测不同浓度的TFC对SMMC7721细胞生长和迁移的影响,流式细胞术分析不同浓度的TFC对SMMC7721细胞凋亡的影响,Western blotting检测不同浓度的TFC组对与SMMC7721细胞中与肿瘤细胞生长、迁移和凋亡密切相关蛋白表达的影响.实验结果显示,TFC能够显著抑制SMMC7721细胞生长、迁移并诱导癌细胞凋亡,TFC药物分子作用机制可能与下调SMMC7721细胞中血管内皮生长因子受体VEGFR1、磷酸化蛋白激酶B(phosphorylated protein kinase B,p AKT)、核转录因子NF-κB、抗凋亡蛋白(BCL2,apoptosis regulator,BCL2)、细胞周期蛋白(cyclin D1,CCND1)表达和上调促凋亡蛋白(BCL2 associated X,apoptosis regulator,BAX)、细胞色素c(cytochrome c,somatic,CYCS)、人体抑癌基因蛋白(tumor protein p53,TP53)、半胱天冬酶3(caspase,CASP3)和E-cadherin蛋白表达有关,TFC抑制人肝癌SMMC7721细胞生长和迁移作用的重要信号通路涉及到VEGFR/AKT/NF-κB.     

胃上皮内瘤和胃癌组织中p53蛋白表达的意义

探讨胃上皮内瘤和胃癌组织中P53蛋白的表达及其临床意义；应用免疫组化SP法对10例慢性胃炎组、30例胃上皮内瘤组及20例胃癌组中P53的表达进行检测；慢性胃炎中无p53表达，随着异型增生程度的增加，p53阳性表达也在增加，胃癌的阳性率最高；p53蛋白在胃上皮内瘤中即显示异常表达，其突变发生于胃粘膜癌变的早期阶段，提示p53基因的缺失、突变与细胞的异型性密切相关。     

The p53 tumour suppressor gene

The cell cycle is composed of a series of steps which can be negatively or positively regulated by various factors. Chief among the negative regulators is the p53 protein. Alteration or inactivation of p53 by mutation, or by its interactions with oncogene products of DNA tumour viruses, can lead to cancer. These mutations seem to be the most common genetic change in human cancers.     

Inactivation of the p53 pathway in retinoblastoma

Most human tumours have genetic mutations in their Rb and p53 pathways, but retinoblastoma is thought to be an exception. Studies suggest that retinoblastomas, which initiate with mutations in the gene retinoblastoma 1 (RB1), bypass the p53 pathway because they arise from intrinsically death-resistant cells during retinal development. In contrast to this prevailing theory, here we show that the tumour surveillance pathway mediated by Arf, MDM2, MDMX and p53 is activated after loss of RB1 during retinogenesis. RB1-deficient retinoblasts undergo p53-mediated apoptosis and exit the cell cycle. Subsequently, amplification of the MDMX gene and increased expression of MDMX protein are strongly selected for during tumour progression as a mechanism to suppress the p53 response in RB1-deficient retinal cells. Our data provide evidence that the p53 pathway is inactivated in retinoblastoma and that this cancer does not originate from intrinsically death-resistant cells as previously thought. In addition, they support the idea that MDMX is a specific chemotherapeutic target for treating retinoblastoma.     

Selective G to T mutations of p53 gene in hepatocellular carcinoma from southern Africa.

Hepatocellular carcinoma (HCC) is a prevalent cancer in sub-Saharan Africa and eastern Asia. Hepatitis B virus and aflatoxins are risk factors for HCC, but the molecular mechanism of human hepatocellular carcinogenesis is largely unknown. Abnormalities in the structure and expression of the tumour-suppressor gene p53 are frequent in HCC cell lines, and allelic losses from chromosome 17p have been found in HCCs from China and Japan. Here we report on allelic deletions from chromosome 17p and mutations of the p53 gene found in 50% of primary HCCs from southern Africa. Four of five mutations detected were G----T substitutions, with clustering at codon 249. This mutation specificity could reflect exposure to a specific carcinogen, one candidate being aflatoxin B1 (ref. 7), a food contaminant in Africa, which is both a mutagen that induces G to T substitution and a liver-specific carcinogen.     

Activation of the DNA damage checkpoint and genomic instability in human precancerous lesions

DNA damage checkpoint genes, such as p53, are frequently mutated in human cancer, but the selective pressure for their inactivation remains elusive. We analysed a panel of human lung hyperplasias, all of which retained wild-type p53 genes and had no signs of gross chromosomal instability, and found signs of a DNA damage response, including histone H2AX and Chk2 phosphorylation, p53 accumulation, focal staining of p53 binding protein 1 (53BP1) and apoptosis. Progression to carcinoma was associated with p53 or 53BP1 inactivation and decreased apoptosis. A DNA damage response was also observed in dysplastic nevi and in human skin xenografts, in which hyperplasia was induced by overexpression of growth factors. Both lung and experimentally-induced skin hyperplasias showed allelic imbalance at loci that are prone to DNA double-strand break formation when DNA replication is compromised (common fragile sites). We propose that, from its earliest stages, cancer development is associated with DNA replication stress, which leads to DNA double-strand breaks, genomic instability and selective pressure for p53 mutations.     

Stage-specific sensitivity to p53 restoration during lung cancer progression

Tumorigenesis is a multistep process that results from the sequential accumulation of mutations in key oncogene and tumour suppressor pathways. Personalized cancer therapy that is based on targeting these underlying genetic abnormalities presupposes that sustained inactivation of tumour suppressors and activation of oncogenes is essential in advanced cancers. Mutations in the p53 tumour-suppressor pathway are common in human cancer and significant efforts towards pharmaceutical reactivation of defective p53 pathways are underway. Here we show that restoration of p53 in established murine lung tumours leads to significant but incomplete tumour cell loss specifically in malignant adenocarcinomas, but not in adenomas. We define amplification of MAPK signalling as a critical determinant of malignant progression and also a stimulator of Arf tumour-suppressor expression. The response to p53 restoration in this context is critically dependent on the expression of Arf. We propose that p53 not only limits malignant progression by suppressing the acquisition of alterations that lead to tumour progression, but also, in the context of p53 restoration, responds to increased oncogenic signalling to mediate tumour regression. Our observations also underscore that the p53 pathway is not engaged by low levels of oncogene activity that are sufficient for early stages of lung tumour development. These data suggest that restoration of pathways important in tumour progression, as opposed to initiation, may lead to incomplete tumour regression due to the stage-heterogeneity of tumour cell populations.     

High frequency of p53 intronic point mutations in laryngeal squamous cell carcinoma

Intronic point mutations are rare and totally unknown for human laryngeal squamous cell carcinoma (LSCC). To explore the relationship of p53 gene intronic mutation to the development of human LSCC, DNA was extracted from both tumor tissues and matched normal tissues of 55 patients with LSCC in northeast of China. Polymerase chain reaction amplification-single strand conformational polymorphism (PCR-SSCP) combined with silver staining and DNA direct sequencing were used to detect mutations in exons 7～8 (p53E7 and p53E8) and introns 7～8 (p53I7 and p53I8) of p53 gene. The p53E7 mutation was detected in 17 out of 55 patients, and the p53I7 mutation in 21 patients. No mutation was found at p53E8 or p53I8 site. The difference between tumor group and paired normal group on the rates of both p53E7 and p53I7 mutations was statistically significant. The rate of p53I7 mutations in tumor tissue was higher than that of normal tissue, and so was that of p53E7. Sequence analysis revealed that most p53I7 mutations were at the nucleotides in the branch point sequence or the polypyrimidine tract in the 3′-splice acceptor site of the intron 7. The high incidence of p53 gene intronic mutation in LSCC indicates that genetic changes within the noncoding region of the p53 gene may serve as an alternative mechanism of activating the pathogenesis of human laryngeal squamous cell carcinoma. Mutations in the noncoding region of this gene should be further studied.     

Mutations in the p53 gene occur in diverse human tumour types

The p53 gene has been a constant source of fascination since its discovery nearly a decade ago. Originally considered to be an oncogene, several convergent lines of research have indicated that the wild-type gene product actually functions as a tumour suppressor gene. For example, expression of the neoplastic phenotype is inhibited, rather than promoted, when rat cells are transfected with the murine wild-type p53 gene together with mutant p53 genes and/or other oncogenes. Moreover, in human tumours, the short arm of chromosome 17 is often deleted. In colorectal cancers, the smallest common region of deletion is centred at 17p13.1; this region harbours the p53 gene, and in two tumours examined in detail, the remaining (non-deleted) p53 alleles were found to contain mutations. This result was provocative because allelic deletion coupled with mutation of the remaining allele is a theoretical hallmark of tumour-suppressor genes. In the present report, we have attempted to determine the generality of this observation; that is, whether tumours with allelic deletions of chromosome 17p contain mutant p53 genes in the allele that is retained. Our results suggest that (1) most tumours with such allelic deletions contain p53 point mutations resulting in amino-acid substitutions, (2) such mutations are not confined to tumours with allelic deletion, but also occur in at least some tumours that have retained both parental 17p alleles, and (3) p53 gene mutations are clustered in four 'hot-spots' which exactly coincide with the four most highly conserved regions of the gene. These results suggest that p53 mutations play a role in the development of many common human malignancies.     

Restoration of p53 function leads to tumour regression in vivo

Tumorigenesis is a multi-step process that requires activation of oncogenes and inactivation of tumour suppressor genes. Mouse models of human cancers have recently demonstrated that continuous expression of a dominantly acting oncogene (for example, Hras, Kras and Myc) is often required for tumour maintenance; this phenotype is referred to as oncogene addiction. This concept has received clinical validation by the development of active anticancer drugs that specifically inhibit the function of oncoproteins such as BCR-ABL, c-KIT and EGFR. Identifying additional gene mutations that are required for tumour maintenance may therefore yield clinically useful targets for new cancer therapies. Although loss of p53 function is a common feature of human cancers, it is not known whether sustained inactivation of this or other tumour suppressor pathways is required for tumour maintenance. To explore this issue, we developed a Cre-loxP-based strategy to temporally control tumour suppressor gene expression in vivo. Here we show that restoring endogenous p53 expression leads to regression of autochthonous lymphomas and sarcomas in mice without affecting normal tissues. The mechanism responsible for tumour regression is dependent on the tumour type, with the main consequence of p53 restoration being apoptosis in lymphomas and suppression of cell growth with features of cellular senescence in sarcomas. These results support efforts to treat human cancers by way of pharmacological reactivation of p53.     

Germ-line transmission of a mutated p53 gene in a cancer-prone family with Li-Fraumeni syndrome

Tumour suppressor genes, whose usual function seems to be controlling normal cell proliferation, have been implicated in many inherited and sporadic forms of malignancies Much evidence supports the concept of tumour formation by loss-of-function mutations in suppressor genes, as predicted by the two-hit model of Knudson and DeMars. The suppressor gene, p53, is affected in such a manner by numerous mutations, which occur in a variety of human tumours. These mutations usually represent the loss of one allele and the substitution of a single base in the other. We have now analysed the p53 gene in a family affected by Li-Fraumeni syndrome, a rare autosomal dominant syndrome characterized by the occurrence of diverse mesenchymal and epithelial neoplasms at multiple sites. In some instances the neoplasms seem to be related to exposure to carcinogens, including ionizing radiation. The Li-Fraumeni family that we studied had noncancerous skin fibroblasts (NSF) with an unusual radiation-resistant phenotype. DNA derived from the NSF cells of four family members, spanning two generations, had the same point mutation in codon 245 (GGC----GAC) of the p53 gene. This mutation leads to substitution of aspartic acid for glycine in one of the regions identified as a frequent target of point mutations in p53. The NSF cell lines with the mutation also retained the normal p53 allele. This inherited p53 mutation may predispose the members of this family to increased susceptibility to cancer.