Maspin在肿瘤中的表达与反表达

Maspin（Mammary-serpin）是1994年Zon等使用消减杂交（sub—tractive hybridization）的方法在对正常乳腺和乳腺癌组织进行比较研究时发现的,它是丝氨酸蛋白酶抑制剂（serine protease inhibitor,serpin）超家族的成员。大量研究表明,Maspin基因是一种肿瘤抑制基因,在多种肿瘤如乳腺癌、前列腺癌中表达下调或缺失,其通过多种机制抑制肿瘤细胞的生长,诱导其凋亡,抑制肿瘤新生血管的生成等;但也有一些文献报道,Maspin在多种肿瘤中呈反表达,如在卵巢、胃的肿瘤中表达呈上调趋势。这两种截然相反的结论,使得人们对Maspin作为一种抑癌基因及其抑癌功能提出了质疑。总之,对Maspin基因表达机制和功能还有待进一步深入的探讨。     

Maspin、iNOS及VEGF与胃癌关系的研究现状

胃癌的发生和发展是一个多基因、多因素和多阶段的复杂演变过程,涉及多种癌基因和抑癌基因。胃部肿瘤新生血管的存在不但为肿瘤生长提供营养物质,转运代谢产物,还为肿瘤细胞的浸润及转移提供了通道。Maspin、VEGF和iNOS与肿瘤血管的生成密切相关。Maspin通过增加肿瘤细胞同质黏附,防止肿瘤细胞从原病灶脱落,抑制血管生成,诱导肿瘤细胞凋亡而抑制胃癌的发生发展。iNOS通过细胞增殖/凋亡失衡,刺激胃癌新生血管形成参与胃癌的发生。VEGF以自分泌及旁分泌形式刺激胃癌细胞的有丝分裂,诱导胃癌血管形成。Maspin在胃癌组织中的低表达和iNOS、VEGF在胃癌组织中的高表达在胃癌的发生、发展和浸润转移过程中起重要作用。     

Maspin基因与胃癌侵袭转移

Maspin基因是从乳腺上皮细胞中分离出的抑癌基因,属于丝氨酸蛋白酶抑制剂超家族的成员。Maspin基因在胃癌侵袭和转移过程中发挥重要作用。研究表明,Maspin基因主要通过诱导肿瘤细胞凋亡、抑制肿瘤血管生成、甲基化修饰作用以及通过促进同质黏附、抑制异质黏附等方式来抑制胃癌的发生、发展和转移。     

乳腺癌中蛋白酶抑制剂Maspin的研究进展

乳腺癌是危害妇女健康的主要恶性肿瘤,其死亡原因几乎都是远处转移所致。因此,了解与乳腺癌转移有关的基因对乳腺癌转移的研究意义重大。Maspin基因为一种新发现的丝氨酸蛋白酶抑制剂最初由Zou等[1]用消减杂交(subtractive hybridiza-tion)技术对正常乳腺组织和乳腺癌组织进行比较时发现的,具有肿瘤抑制活性。大量研究表明,Maspin基因是一种肿瘤抑制基因,在多种肿瘤比如乳腺癌、口腔鳞癌中,其表达下调或缺失,而且Maspin基因的缺失会导致肿瘤浸润转移能力的增强[2-4]。1Maspin基因的定位和结构特点Maspin基因是常染色体基因,位于18q21.3-q…     

胃癌组织中Maspin 蛋白与血管内皮生长因子-C的表达及其相关性

 目的 探讨胃癌组织中Maspin蛋白与血管内皮生长因子-C（VEGF-C）的表达及其相关性。方法 收集哈尔滨医科大学附属肿瘤医院2002年～2003年间手术切除的胃癌组织石蜡标本61例,采用免疫组化技术检测胃癌组织中Maspin蛋白与血管内皮生长因子-C（VEGF-C）的表达情况,结合临床病理特征进行分析,并探讨两者蛋白表达水平的相关性。结果 Maspin蛋白的阳性表达率为50.8%（31/61）。淋巴结转移阳性组织中Maspin蛋白的阳性表达率明显低于淋巴结转移阴性的组织（32.6%vs94.4%,P=0.000）。且Maspin蛋白在组织分化较低,TNM分期较晚,周围有肿瘤浸润的病例中表达率显著降低（P分别为0.018,0.011和0.028）。VEGF-C在胃癌组织中的阳性表达率为86.9%（53/61）。淋巴结转移阳性组织中VEGF-C蛋白的阳性表达率明显高于淋巴结转移阴性的组织（95.3%vs66.7%,P=0.006）。Maspin蛋白与VEGF-C在胃癌组织的表达存在负相关（Spearmanr=-0.429,P〈0.05）。结论 Maspin蛋白在胃癌组织中低表达,胃癌的浸润转移能力增强可能与Maspin蛋白表达下调、缺失相关;VEGF-C的高表达与肿瘤淋巴结转移关系密切;Maspin蛋白与VEGF-C在胃癌组织中的表达呈明显负相关。     

Maspin在65例乳腺癌中的表达及其临床意义

[目的]研究乳腺癌中Maspin基因的表达情况及临床意义。[方法]应用免疫组化S-P法检测77例乳腺病变组织（12例良性病变,65例乳腺癌）Maspin表达情况,结合临床、病理形态学资料分析其临床意义。[结果]12例良性乳腺病变组织中Maspin蛋白阳性率100%,65例乳癌组织中Maspin蛋白阳性率30.8%（20/65）,差异有显著性（P〈0.01）。乳腺癌中Maspin的表达与ER、淋巴结转移、组织学类型和组织学分级有关（P〈0.05）。Spearman等级相关分析显示Maspin表达与腋淋巴结转移、临床分期、组织学分级呈负相关,Logistic多因素回归分析显示腋淋巴结转移、ER和组织学分级是Maspin蛋白阳性表达的影响因素（P〈0.05）。[结论]Maspin蛋白可作为乳腺癌内分泌治疗肿瘤恶性转化、转移和预后评估的一个重要指标。     

在CerbB-2表达不同的乳腺癌组织中Maspin的表达

目的　对CerbB 2表达不同的乳腺癌组织中肿瘤抑制基因Maspin的表达变化进行比较研究。方法　采用免疫组化SP染色法检测2 9例乳腺癌组织中Maspin蛋白的表达情况。结果　Maspin蛋白在CerbB 2阴性表达的乳腺癌组织中的高表达率为47% (7/15 ) ,在CerbB 2阳性表达的乳腺癌组织中的高表达率仅为7% (1/14 ) ,两者有显著性差异(P <0 .0 5 )。结论　在CerbB 2表达不同的乳腺癌组织中Maspin表达亦存在显著差异,Maspin也可作为判定乳腺癌恶性程度及预后的指标。     

鼻咽癌中Maspin和Bmi-1基因表达及其临床意义

目的 探讨鼻咽癌组织中Maspin和Bmi-1的表达及其与临床病理特征的关系。方法 应用免疫组织化学法检测Maspin和Bmi-1在60例鼻咽癌及40例正常鼻咽组织中的表达情况,探讨两者表达的相关性及与鼻咽癌临床病理特征的关系。结果 Maspin在鼻咽癌及正常鼻咽组织中的阳性表达率分别为45.0%（27/60）和90.0%（36/40）,差异有统计学意义（P＜0.05）。Bmi-1在鼻咽癌及正常鼻咽组织中的阳性表达率分别为75.0％（45／60）和25.0％（10／40）,差异有统计学意义（P＜0.05）。Maspin和Bmi-1表达与年龄无关（P＞0.05）,而与肿瘤分化程度、淋巴结转移及临床分期有关 （P＜0.05）。Maspin与Bmi 1在鼻咽癌组织中的表达呈负相关（r=-0.406,P＜0.05）。结论 Maspin和Bmi-1表达可能在鼻咽癌的发生、增殖和转移中起重要作用。     

外界刺激下肿瘤细胞中早反应基因5相关生物学功能的研究进展

早反应基因5（IER5）属于早期反应基因,因其在多种肿瘤细胞中均发挥着抑制肿瘤细胞增殖的作用而受到广泛关注。在受到外界刺激（热压力、血清、电离辐射等）时,肿瘤细胞内的IER5会过表达从而使细胞作出一系列应激性反应如G2期周期阻滞和凋亡等。在临床放化疗中IER5的表达量可以作为一种潜在的肿瘤放化疗后诱导细胞凋亡的生物标记物,并和肿瘤组织大小相关,对今后放化疗方案的改进具有重要的指导意义。     

增殖诱导配体及其在肿瘤发生发展中的作用

增殖诱导配体（APRIL）是近年来发现的肿瘤坏死因子（TNF）超家族成员。通过对APRIL的基因蛋白结构、组织表达、信号传导通路的研究，发现它在多种肿瘤细胞内表达，并对肿瘤细胞的增殖和抗凋亡发挥重要作用。抑制APRIL与其受体结合、阻断其信号传导通路可明显抑制肿瘤细胞的增殖从而为肿瘤的治疗提供新途径。     

Epigenetic silencing of maspin gene expression in human breast cancers

Maspin is a tumor suppressor whose expression is lost in many advanced breast cancers. Maspin has been shown to inhibit cell motility, invasion and metastasis; however, its precise role in normal mammary epithelium remains to be elucidated. Although expression of maspin mRNA is low or absent in most human breast cancer cells, the maspin gene is rarely re-arranged or deleted. We hypothesized that aberrant cytosine methylation and chromatin condensation of the maspin promoter participates in the silencing of maspin expression during neoplastic progression. To test this hypothesis, we compared cultured normal human mammary epithelial cells (HMECs) to 9 cultured human breast cancer cell lines. HMECs expressed maspin mRNA and displayed a completely non-methylated maspin gene promoter with an open chromatin structure. In contrast, 7 of 9 breast cancer cell lines had no detectable maspin expression and 6 of these 7 maspin-negative breast cancer cell lines also displayed an aberrant pattern of cytosine methylation of the maspin promoter. Interestingly, the maspin promoter was completely methylated in maspin-negative normal peripheral blood lymphocytes. This indicates that the maspin promoter is not a functional CpG island and that cytosine methylation of this region may contribute to normal tissue-restricted gene expression. Chromatin accessibility studies with MCF-7 cells, which lack maspin expression and have a methylated maspin promoter, showed a closed chromatin structure compared with HMECs. Moreover, maspin gene expression could be re-activated in MCF-7 cells by treatment with 5-aza-2;-deoxycytidine, a DNA demethylating agent. Thus, aberrant cytosine methylation and heterochromatinization of the maspin promoter may silence maspin gene expression, thereby contributing to the progression of human mammary cancer.     

Tissue microarray analysis of maspin expression and its reverse correlation with mutant p53 in various tumors

Maspin is a member of serpin family with tumor suppressing activity. Initially identified from normal mammary epithelial cells, maspin expression was down-regulated in breast tumor cells by both in vitro assay and by immunostaining of clinical specimen from breast cancer patients. Recently, maspin research has been advanced to clinical research aimed at correlating the tumor progression with the expression level of maspin in breast cancers. However, due to the variation and large sample sizes, no comparison study of maspin expression has been done using various normal and tumor samples. The tissue microarray is a technique recently developed for the standardization and high-throughput screening of clinical markers. We have used the tissue microarray to examine the maspin expression in various normal tissues and cancers. Our data indicated that maspin was expressed at different level in most of human tissues in the array. However, maspin expression was consistently down-regulated during tumor progression. There were no obvious correlation between maspin expression and tumor grades, nor was there any correlation with the age of patients. Since wild-type p53 was found to activate maspin promoter in vitro, we examined weather there was a connection between p53 level and maspin expression in vivo. Our data indicate that maspin expression inversely correlates with mutant p53 level in majority of cancer, suggesting maspin is likely a p53 target gene in vivo.     

Expression of the tumor suppressor gene Maspin in human pancreatic cancers.

The tumor suppressor gene maspin, a unique member of the serpin superfamily, inhibits cell motility, invasion, and metastasis in breast and prostate cancers. Maspin is expressed in normal human mammary and prostate epithelial cells but down-regulated during cancer progression. In this study, we analyzed the expression of maspin in various human cancer cells by means of Northern blot and immunohistochemistry. Maspin gene expression proved to be up-regulated in pancreatic cancer. Maspin expression was not detected in any of 6 gastric cancers, 4 melanomas, or 6 of 7 breast cancer cell lines examined. In contrast, 5 of 9 pancreatic cancer cell lines showed maspin expression, although maspin expression was not detected in normal pancreatic tissue. Furthermore, maspin was expressed in 23 of 24 tumor specimens obtained from pancreatic cancer patients as well as all high-grade precancerous lesions (PanIN3 and intraductal carcinoma extension). In contrast, no expression was observed in normal and low-grade precancerous lesions. Our results show that maspin is a new factor associated with pancreatic cancer. In addition, the detection of maspin in pancreatic tumor tissues and its lack of expression in all normal pancreatic tissues suggests that maspin may be a useful marker of primary human pancreatic cancer.     

Blocking tumor growth, invasion, and metastasis by maspin in a syngeneic breast cancer model

Maspin is a unique serine protease inhibitor of which the down-regulation is associated with the development of breast cancers. In vitro, recombinant maspin inhibits tumor cell migration and invasion. Overexpression of maspin in transgenic mice is protective against tumor progression. Additionally, maspin acts as an angiogenesis inhibitor in rat cornea model and in a xenograft tumor model. To additionally prove that maspin is directly involved in the suppression of tumor growth and metastasis, we tested maspin in a new syngeneic mammary tumor model, TM40D. This model involves the implantation of TM40D mammary tumor cells orthotopically to the mammary gland; tumors grew within the gland and then become invasive and metastatic to other organs. Here we demonstrate that TM40D cells in implanted mammary glands are highly invasive. Overall, a 75% rate of invasion and metastasis was observed in this model. However, both primary tumor growth and metastasis were significantly blocked in TM40D cells that overexpress maspin as a consequence of plasmid or retrovirus infection. Maspin-transfected tumors tended to have tumor encapsulation and less necrosis, which were associated with better prognosis and lower invasiveness. Thus, maspin can block primary tumor growth as well as invasion and metastasis. These data support the concept that maspin has a strong protective role against tumor progression.     

Targeted expression of maspin in tumor vasculatures induces endothelial cell apoptosis

Angiogenesis, the formation of new blood vessels, is required for normal tissue development and pathological conditions such as tumorigenesis. Most solid tumors can not grow beyond a few millimeters without the recruitment of neovessels since cancer cells require access to blood vessels for nutrients and to escape the local environment and metastasize to other tissue and organ sites. Targeting tumor vessel endothelium therefore should serve as an effective therapy for cancers. Maspin is a serpin that exhibits antiangiogenic properties. In this report, we show that when maspin overexpression is targeted in vivo to endothelial cells, it actively induces endothelial cell apoptosis. Intravascular administration of adenovirus-maspin to mice bearing mammary tumors disrupts tumor-induced angiogenesis. Interestingly, tumor neovessels become leaky after maspin treatment, whereas normal mature vessels are not affected by maspin treatment. We further demonstrate that maspin directly induces endothelial cell apoptosis in vitro, and this effect is maspin specific. The induction of apoptosis is accompanied by changes in the expression of Bcl-2 family genes and is blocked by caspase inhibitors. In addition, the apoptotic effect is mediated by intracellular maspin and is dependent on the RSL region of maspin. Furthermore, we have shown that transient overexpression of Bcl-2 protected the HUVECs from maspin-mediated apoptosis, and the presence of both maspin and Bax accelerated the apoptosis process. These findings demonstrate that neovascular endothelial cells are highly sensitive to maspin level inside the cells. This property can be used for targeted therapy against tumor angiogenesis and metastasis.     

Aberrant maspin expression is involved in early carcinogenesis of gallbladder cancer

Mammary serine protease inhibitor (maspin, SERPIN-B5) is expressed in normal human mammary epithelial cells and is known to be down-regulated during cancer progression. Aberrant maspin expression has been reported in a number of cancers, including pancreatic and ovarian cancer. Recently, we identified several genes that may be tumor markers for gallbladder (GB) cancer using a DNA microarray method. There are no published data regarding maspin expression in GB cancer. The aims of this study were to determine maspin expression in normal mucosa, adenoma, dysplasia and carcinoma of GB, and to compare the pattern of maspin expression in early and advanced GB cancers. One hundred one patients with primary GB cancer who underwent resection between March 1999 and May 2008 were included. Twenty-five adenomas and 10 normal GB specimens were also included. We performed tissue microarray construction and immunohistochemical staining to evaluate maspin expression. The immunostaining results were estimated semiquantitatively by one pathologist. The positive rate of maspin expression was 59.4% (60/101) in GB cancer, whereas no maspin was expressed in adenomas and normal mucosa of GB. In case of positive maspin expression, it was gradually increased from dysplasia to carcinoma. No significant difference in the positive rate of maspin expression between early and advanced cancer was detected (49% versus 60%; P?=?0.731). This result suggests that maspin expression may be involved in dysplasia–carcinoma sequence and the early steps of GB carcinogenesis.     

Maspin regulates hypoxia-mediated stimulation of uPA/uPAR complex in invasive breast cancer cells

Maspin, a unique serine proteinase inhibitor (serpin), plays a key role in mammary gland development and is silenced during breast cancer progression. Maspin has been shown to inhibit tumor cell motility and invasion in cell culture, as well as growth and metastasis in animal models. In this study, we investigated the effect of maspin on the regulation of hypoxia-induced expression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR), with respect to invasive potential in metastatic breast cells MDA-MB-231. We hypothesized that maspin can neutralize or mitigate hypoxia-induced expression of uPA/uPAR in metastatic breast cancer cells, resulting in suppression of their invasive potential. To test our hypothesis, we employed the highly invasive MDA-MB-231 breast cancer cells that are devoid of maspin, and transfected them with the maspin gene, and then determined the effect of hypoxia on uPA/uPAR expression. Normal mammary epithelial cells 1436N1 were used as a control. Our findings demonstrate that maspin downregulated the basal and hypoxia-induced uPA/uPAR expression and reduced the stimulatory effect of hypoxia on the in vitro invasive ability of MDA-MB-231-cells. In addition, maspin also inhibited the enzymatic activity of secreted and cell associated uPA in MDA-MB-231 cells. These results indicate that maspin inhibits hypoxia-induced invasion of metastatic breast cancer cells by blocking the uPA system, thus illuminating an important molecular pathway for therapeutic consideration.