Distinct promoter usage of mdm2 gene in human breast cancer

Human breast cancers, especially estrogen receptor alpha (ER(alpha))-positive ones, often overexpress the oncoprotein MDM2 without mdm2 gene amplification. The mdm2 gene is transcribed into two different mRNAs, namely L-mdm2 and S-mdm2, which are generated from promoters P1 (constitutive) and P2 (regulated by tumor suppressor p53), respectively. To cast light on the mechanisms of MDM2 overexpression, we measured the expression levels of these mdm2 mRNAs using RT-PCR analysis in three human breast cancer cell lines and 15 breast cancer samples obtained from surgery. ER(alpha)-positive MCF-7 cells, which possess wild-type p53, displayed dominant expression of S-mdm2. In contrast, two other cell lines with mutant p53, T47-D (ER(alpha)-positive) and MDA-MB-231 (ER(alpha)-negative), showed almost equivalent expression of L-mdm2 and S-mdm2. Treatment of 17beta-estradiol (E2) significantly enhanced the expression of S-mdm2 but not that of L-mdm2 in MCF-7. Among 6 breast cancer samples regarded as ER(alpha)-positive with wild-type p53, 5 samples showed increased expression of S-mdm2. Expression of S-mdm2 was stimulated in 2 ER(alpha)-positive samples with mutant p53. In contrast, 4 of 5 samples which express mutant p53 without ER(alpha) showed poor expression of S-mdm2. There is a tendency that ER(alpha)-positive breast cancers with wild-type p53 preferably use P2 promoter for the expression of mdm2, possibly through E2-induced accumulation of p53. However, wild-type p53 and ER(alpha) are not necessarily enough for the utilization of S-mdm2. Tumors with mutant p53 also showed expression of S-mdm2 in some cases. These results strongly suggest that other factor(s) is also implicated in the promoter usage of mdm2 gene in human breast cancer tissues.     

乳腺癌组织MDM2和p53蛋白质的表达水平及其与病理指标的关系

研究乳腺癌组织ＭＤＭ２和ｐ５３蛋白质的定位、表达水平及其与肿瘤大小、病理分型、分类、分级、癌周浸润程度、纤维组织反应和淋巴细胞反应等临床病理指标的关系。方法应用单克隆抗体和链霉亲和素－生物素－过氧化物酶复合物（ＳＡＢＣ）免疫组织化学染色方法，检测１０６例乳腺癌组织石蜡切片标本ｍｄｍ２和ｐ５３蛋白质的定位和表达水平，比较其与各病理指标的关系。结果（１）乳腺癌组织ｍｄｍ２和ｐ５３蛋白质均明确定位于细胞核；（２）１０６例乳腺癌组织ｍｄｍ２表达阳性率为８１．１％，ｐ５３为７５．３％，ｍｄｍ２与ｐ５３蛋白质的表达水平呈正相关系；（３）乳腺癌组织ｍｄｍ２和ｐ５３蛋白质的表达水平与病理学分级、癌周浸润程度和纤维组织反应有关（Ｐ＜０．０５），而与肿瘤大小、病理分型、分类和淋巴细胞反应无关（Ｐ＞０．０５）。结论检测乳腺癌组织ｐ５３蛋白质和ｍｄｍ２的表达水平可作为判断细胞分级、分化和肿瘤生物学行为的指标之一。     

Prognostic value of simultaneous expression of p21 and mdm2 in breast carcinomas treated by adjuvant chemotherapy with antracyclin

One hundred and sixty-two breast carcinomas treated by adjuvant chemotherapy were investigated in immunohistochemistry for expression of p53 and two wild-type p53-regulated induced proteins, mdm2 and p21/waf1. p21 and mdm2 were expression stongly correlated with Ki67 but not with survival. The p53+/p21+, p53+/p21- and p53+/mdm2- phenotypes were associated with the worst prognosis. The p53+/p21+/ mdm2+ tumors were associated with a better outcome than the other phenotypes, they may be tumors expressing wild-type p53 and p21, and a form of mdm2 that might lead to the stabilization of p53. It is suggested that p21/mdm2 expression should be investigated in all cases of p53 positive breast cancer.     

Expression of p21/waf1 in oral squamous cell carcinomas--correlation with p53 and mdm2 and cellular proliferation index

The cyclin-dependent kinase inhibitor p21/waf1 is regulated by p53-dependent and p53-independent pathways. In addition, mdm2 is an oncogene which forms an auto-regulatory loop with the normal p53 protein and its role has been implicated in oncogenesis. To determine whether a correlation exists between the expression of these gene products, tumor differentiation, tumor staging and radiation therapy, we investigated the expression of p21, p53 and mdm2, and cellular proliferation by Ki-67 (MIB1) labeling index using immunohistochemistry in 88 human oral squamous cell carcinoma (SCC) samples from 56 patients. Tumor expression of all nuclear proteins was scored according to the percentage of positive cancer nuclei, both with the cancer tissue as a whole as well as in different epithelial compartments of differentiation. Positive p21, p53, mdm2 and MIB1 staining was present in 82.4, 67.8, 25.9 and 98.8% of the SCC samples. The staining in different epithelial compartments of differentiation varied: those of p21 and mdm2 present predominantly in suprabasal and upper regions of the tumors: those of p53 and MIB1 in basal and suprabasal regions. Higher levels of p21 expression were seen in actively proliferating tumors (P = 0.025). p21 expression positively correlated with mdm2 expression but not with p53 expression. Moreover, the level of p21 expression was higher in older patients (P = 0.024) and female patients (P = 0.008). There was no significant association among p53, mdm2 and MIB1. Expression of p53 was higher in tumors with poorer cellular differentiation and in younger patients (P = 0.038 and 0.028). There was no association between tumor stage by TNM classification and the expression of any of these gene products or proliferation index. Radiation therapy did not alter the expression of any of these. To conclude, p21 protein was overexpressed in oral SCCs, and this overexpression was related to cell proliferation index and mdm2 expression but independent of p53 protein alteration. Overexpression of p21 alone appeared to be insufficient to suppress tumor progression.     

Overexpression of MDM2 in MCF-7 promotes both growth advantage and p53 accumulation in response to estradiol.

The overexpression of the oncogene product MDM2 is often observed in human breast cancer cells, especially in estrogen receptor (ER)-positive ones. To study the role of MDM2 protein in ER-positive breast cancer, we have established cell lines derived from MCF-7 which stably express increased and decreased levels of MDM2 by transfection of a mammalian expression vector containing human mdm2 cDNA in sense and antisense orientations, respectively. Interestingly, MDM2 overexpression in MCF-7 cells afforded a remarkable growth advantage under estradiol (E2)-supplemented condition. Then, we analyzed the expression of p53, which is an important regulator of growth and the cell cycle. Unexpectedly, the p53 accumulation induced by E2 was remarkably higher in MCF-7 cells stably overexpressing MDM2 than in the parent MCF-7 cells. On the other hand, reduction of MDM2 suppressed the E2-induced increase in p53 protein. Moreover, mdm2 antisense oligonucleotides prevented E2-induced accumulation of p53. In the steady state, the cellular levels of p53 were also correlated with those of MDM2. These interactions are not consistent with the well-known role of MDM2, which acts as a negative regulator for p53 by inhibiting its function and promoting its rapid degradation. These results suggest that MDM2 may regulate the expression of p53 in the steady state and in response to E2 in breast cancer cells, and imply a novel and important role of MDM2 during breast carcinogenesis.     

以任何方法剪接:Mdm2位于肿瘤监视的十字路口

鼠双微基因2(Mdm2)是p53最重要的调节基因,同时也是对各种类型细胞应激(包DNA损害和致癌损伤)的主要应答者.尽管已有文章描述了Mdm2基因的替代产物的异常拼接产物,但是关于该变异体的起源、功能和影响,现在尚不清楚.最近发现了一种新的mdm2基因的剪接形式.在该剪接体中,108bp的基因内序列合并到成熟的Mdm2 mRNA中.编码框内终止密码子的额外序列可使Mdm2蛋白明显缩短.最有趣的现象是,阿霉素和放线菌素D能诱导产生一种交替剪接形式,即成熟的Mdm2 108,而其他的DNA损伤剂没有这种诱导作用.Mdm2 108基因可诱导p53的大量快速聚集,证明该交替剪接事件的作用是形成p53的肿瘤监视途径,同时抑制细胞的增殖(该细胞为被有效的遗传毒性化合物所破坏的细胞).     

Overexpression of MDM2 in MCF-7 Promotes Both Growth Advantage and p53 Accumulation in Response to Estradiol

The overexpression of the oncogene product MDM2 is often observed in human breast cancer cells, especially in estrogen receptor (ER)-positive ones. To study the role of MDM2 protein in ER-positive breast cancer, we have established cell lines derived from MCF-7 which stably express increased and decreased levels of MDM2 by transfection of a mammalian expression vector containing human mdm2 cDNA in sense and antisense orientations, respectively. Interestingly, MDM2 overexpression in MCF-7 cells afforded a remarkable growth advantage under estradiol (E2)-sup-plemented condition. Then, we analyzed the expression of p53, which is an important regulator of growth and the cell cycle. Unexpectedly, the p53 accumulation induced by E2 was remarkably higher in MCF-7 cells stably overexpressing MDM2 than in the parent MCF-7 cells. On the other hand, reduction of MDM2 suppressed the E2-induced increase in p53 protein. Moreover, mdm2 antisense oligonucleotides prevented E₂-induced accumulation of p53. In the steady state, the cellular levels of p53 were also correlated with those of MDM2. These interactions are not consistent with the well-known role of MDM2, which acts as a negative regulator for p53 by inhibiting its function and promoting its rapid degradation. These results suggest that MDM2 may regulate the expression of p53 in the steady state and in response to E2 in breast cancer cells, and imply a novel and important role of MDM2 during breast carcinogenesis.     

肝细胞肝癌中VEGF、p53、mdm2蛋白表达及其相互关系

目的　研究肝细胞肝癌 (HCC) VEGF、p5 3、m dm2蛋白表达及其相互关系。方法　用免疫组化 S- P法或SAP法检测 HCC组织 VEGF、mdm2和 p5 3蛋白表达 ,计数微血管密度 (MVD) ,并与临床病理指标比较分析。结果　 72例 HCC中 VEGF、p5 3、mdm2蛋白阳性表达分别为 6 2 .5 %、4 1.6 %和 33.3% ;VEGF和 p5 3,VEGF和 m dm2 ,mdm2和 p5 3蛋白表达有相关性 (P<0 .0 5 )。 2 5例癌旁组织中 VEGF蛋白阳性表达为 2 0 .0 % ,m dm2蛋白阳性表达为 8.0 % ,p5 3蛋白阳性表达为 8.0 %。肝癌组织和癌旁组织 VEGF、m dm2和 p5 3蛋白表达差异有显著性 (P<0 .0 5 )。 10例正常肝组织无 VEGF、mdm2和 p5 3蛋白表达。 HCC组织中 VEGF、p5 3、mdm2蛋白阳性表达以及高MVD与血管侵犯和转移倾向明显相关 (P<0 .0 5 )。结论　 HCC组织中 VEGF、p5 3、mdm2蛋白过表达。p5 3突变和mdm2蛋白过表达 ,是 VEGF表达上调的原因之一 ,并与 HCC组织中血管侵犯和转移倾向有关     

A modified p53 overcomes mdm2-mediated oncogenic transformation: a potential cancer therapeutic agent

The antiproliferative activities of wild-type (wt) p53 are inhibited by mdm2 (murine double minute2) oncogene product. We tested growth suppression activity of p53 14/19, an engineered p53 variant, which does not bind mdm2 and is completely resistant to the inhibition by mdm2. p53 14/19, unlike wt p53, suppressed the growth of cancer cells that contain amplified mdm2 oncogene efficiently by direct DNA transfection or adenovirus-mediated gene transfer. In addition, p53 14/19 also inhibited the growth of several different cancer cell lines expressing low levels of mdm2 oncogene product as efficiently as wt p53. We further examined the antioncogenic potencies of p53 14/19 in the rat embryo fibroblast cotransformation assay. Addition of wt p53 failed to cause any significant decrease in ras plus mdm2 foci counts. In contrast, cotransfection of p53 14/19 with ras and mdm2 significantly reduced foci number. In similar experiments, cotransfection of wt p53 or 14/19 p53 resulted in significant inhibition of oncogenic transformation in rat embryo fibroblast mediated by an activated ras plus c-myc, adenovirus E1A, or human papillomavirus E7 oncogenes. Therefore, these results suggest that p53 14/19 modified tumor suppressor gene may be a promising therapeutic agent for human cancers that express abnormally high levels of mdm2 oncogene product.     

Expression patterns of the p53 tumor suppressor gene and the mdm2 proto-oncogene in human meningiomas

Meningiomas represent a common class of tumors of the central nervous system. However, the molecular events underlying theirformation are poorly understood. Because altered expression ofthe p53 tumor suppressor gene and the mdm2 proto-oncogene havebeen demonstrated in a wide variety of tumors, we carried out studies to assess the possible involvement of these two genes in meningiomatumorigenesis. We used Western blot analysis to examine the levelof expression of the mdm2 and p53 proteins in a seriesof sixteen primary meningiomas and four meningioma cell lines. The data obtained from these studies suggest that elevated expression of the p53 or mdm2 protein products does not representa common event in the development of human meningiomas.     

mdm2、p53在胶质瘤中的表达意义及与临床病理特征的关系

目的:分析mdm2、p53在胶质瘤中的表达意义及与临床病理特征的关系。方法:选取我院2012年4月至2013年4月期间存档的54例胶质瘤石蜡标本以及相应瘤旁正常组织标本作为研究对象，将胶质瘤石蜡标本作为观察组，将瘤旁正常组织标本作为对照组。采用LSAB免疫组化法测量两组样本中mdm2、p53蛋白表达水平，分析上述蛋白在胶质瘤患者疾病发生及发展中的具体意义。结果:胶质瘤石蜡标本中mdm2、p53阳性表达率显著高于相应瘤周正常组织标本（P＜0.05）；Ⅲ、Ⅳ期胶质瘤患者p53、mdm2阳性表达率及“+++”表达率显著高于Ⅰ、Ⅱ期患者（P＜0.05）；p53、mdm2高表达患者术后生存时间均显著低于p53、mdm2低表达患者（P＜0.05）；p53、mdm2阳性表达率均与疾病分期以及淋巴结转移有明显相关性（P＜0.05）；mdm2、p53蛋白在胶质瘤中呈正相关（r=0.713，P＜0.05）。结论:mdm2通过调节p53蛋白的表达对胶质瘤发生发展起调控作用，Ⅲ、Ⅳ期疾病分期及淋巴结转移等因素均对mdm2、p53在肿瘤细胞中的异常表达有相关性，临床中可针对上述指标阳性表达程度预测患者病情发展，并为后续治疗方案的制定及改善提供相应的数据支持。     

mdm2和p53基因在急性白血病细胞中的表达及意义

目的：探讨人急性髓细胞性白血病（ａｃｕｔｅ ｍｙｅｌｏｉｄ ｌｅｕｋｅｍｉａ．ＡＭＬ）细胞ｍｄｍ２及ｐ５３基因蛋白表达水平,相互关系及与临床预后的关系。方法：用免疫组化方法测定ｍｄｍ２及ｐ５３蛋白表达,ＨＰＩＡＳ－１０００高清晰度病理图像细胞测定系统分析结果。结果：７５％的ＡＭＬ患者表达不同程度的ｍｄｍ２蛋白,且在各种分型中均有ｍｄｍ２蛋白过度表达者：１８．７５％的ＡＭＬ患者表达ｐ５３蛋白;在ＡＭ     

mdm2／p53通路相关的乳腺癌差异表达基因分析

目的比较乳腺癌和正常乳腺组织的基因表达差异，探讨与mdm2／p53通路相关的差异表达基因。方法提取11例乳腺癌和将5例正常乳腺组织等比例混合的组织总RNA进行芯片杂交，用SAM软件筛选差异表达基因，用GoMiner软件检索差异表达基因的功能，挑选参与细胞周期和凋亡的基因，通过Pathway分析方法检索与mdm2／p53通路相关的差异基因；用免疫组化方法验证差异基因cyclin A2及其相关基因CDK2在乳腺癌（38例）和正常乳腺组织（16例）中的表达。结果乳腺癌与正常乳腺组织的差异表达基因共548个，其中参与细胞周期的基因有35个，参与凋亡的基因有23个；与mdm2／p53通路相关的差异基因有4个，分别是cyclin A2，cyclin B1，PCNA，YWHAZ；经免疫组化验证的38例乳腺癌和16例正常乳腺组织的cyclin A2表达阳性率分别为42．1％（16／38，和6．25％（1／16）；CDK2表达阳性率分别为47．3％（18／38）和6．25％（1／16），两者均有统计学差异（P〈0．05）；在乳腺癌中cyclin A2与CDK2的表达呈正相关，特别值得一提的是如果以≥2^＋为阳性在乳腺癌cyclin A2为26．3％，CDK2为31．5％，而在正常组几乎看不到≥2^＋的表达。结论乳腺癌组织与正常乳腺组织相比存在着差异表达基因，与mdm2／p53通路相关的差异基因的异常高表达促进细胞增殖，与乳腺癌的发生密切相关，而cyclin A2和CDK2在乳腺癌共表达并明显高于正常组织其意义还不清楚。