抑癌基因PTEN与食管癌关系的研究进展

目的:总结抑癌基因PTEN在食管癌组织中遗传学及表观遗传学研究的历史、现状及面临的问题.方法:应用PubMed及CNKI期刊全文数据库检索系统,以“PTEN基因、食管癌、遗传学和表现遗传学”等为关键词,检索2000-01-2012-06的相关文献.纳入标准:1)PTEN基因在食管癌组织的表达;2)PTEN基因在食管癌中遗传学及表观遗传学改变;3)PTEN基因在食管癌发生和发展的机制;4)PTEN基因表达对食管癌的治疗及预后分析的意义.根据纳入标准符合分析文献36篇.结果:抑癌基因PTEN在食管癌中表达水平显著下调,并与食管癌TNM分期及预后存在相关性.PTEN基因点突变与食管癌的临床进展关系不明确.食管癌存在PTEN基因杂合性缺失及微卫星不稳定,但与食管癌的临床病理特征无关.PTEN基因多态性与PTEN蛋白质表达水平及食管癌危险因素的关系尚无定论.PTEN基因表观遗传学改变研究较少,对PTEN蛋白功能的影响及在食管癌的进展过程中的意义尚不明确.PTEN基因在食管癌低表达的确切机制有待进一步研究.结论:PTEN基因参与食管癌细胞生长、分化、凋亡及细胞信号传导,与食管癌的发生、发展、治疗及预后密切相关.     

PTEN与肿瘤的研究及基因治疗进展

 PTEN是迄今为止人类发现的第一个具有磷酸化酶功能的抑癌基因,PTEN功能的缺失与肿瘤的发生密切相关,该基因异常将导致蛋白表达下降从而失去抑癌作用。目前,有关PTEN 基因的研究已经涉及到了其治疗研究,主要是通过转基因技术将野生型PTEN 基因导入恶性肿瘤基因组中,替换肿瘤细胞中突变的 PTEN 基因,发挥正常 PTEN 基因的抑癌功能。文章就当前PTEN的发现、结构、作用机制与肿瘤的关系及其基因治疗的研究进行综述。     

星形细胞瘤中PTEN、p53及Ki-67的表达与肿瘤细胞增殖及分级的关系

 目的　探讨星形细胞瘤中PTEN、p53及Ki-67的表达水平及其与肿瘤细胞增殖及分级的关系。方法　采用免疫组织化学方法检测68例星形细胞瘤中PTEN、p53及Ki-67的表达水平。结果　星形细胞瘤中PTEN、p53及Ki-67的表达率分别是54.4 %、45.6 %及48.5 %,随着肿瘤级别增加,PTEN的表达率下降,而p53、Ki-67的表达率上升,Spearman等级相关分析显示PTEN的表达与星形细胞瘤的分级呈负相关,p53、Ki-67的表达与分级呈正相关。PTEN阳性表达的37例星形细胞瘤标本中,Ki-67的阳性率是24.3 %;而在PTEN阴性的31例标本中,Ki-67的阳性率是77.4 %,PTEN表达与Ki-67表达呈负相关。结论　PTEN的表达与星形细胞瘤的分级呈负相关,Ki-67、p53的表达与星形细胞瘤组织病理分级呈正相关。PTEN在一定程度上可以抑制肿瘤细胞的增殖。     

PTEN基因突变及蛋白表达与子宫内膜癌的相关性研究

目的:探讨子宫内膜癌组织中PTEN基因突变、蛋白表达异常,及其与子宫内膜癌发生、发展和临床病理特征的相关性.方法:应用PCR-SSCP方法检测52例子宫内膜癌组织和10例正常子宫内膜组织中PTEN基因突变情况,同时检测PTEN蛋白的表达并结合临床病理资料进行分析.结果:PTEN基因突变在正常子宫内膜组织中与子宫内膜癌组织中差异有显著性.正常子宫内膜组织中PETN蛋白阳性表达率与子宫内膜腺癌组织中蛋白表达率差异有显著性.子宫内膜癌组织中PTEN基因突变率与蛋白表达缺失率与子宫内膜癌的组织学分级,组织病理类型,肌层浸润深度密切相关,PTEN基因突变率与蛋白表达缺失率与是否绝经、孕产次、体重指数、有无糖尿病、高血压、无统计学关联.52例子宫内膜癌组织中35例PTEN蛋白表达缺失,表达缺失组织中18例发生PTEN基因突变.结论:PTEN基因突变及蛋白表达缺失与子宫内膜癌的发生和发展有一定相关性,与子宫内膜样腺癌的分化程度、肌层浸润深度有相关性,而与临床特征无相关性.子宫内膜癌中.PTEN基因突变是PTEN蛋白表达缺失的重要原因.     

霍奇金淋巴瘤R-S细胞PTEN基因的表达与意义

目的：研究PTEN基因在霍奇金淋巴瘤（Hodgkin＇s lymphoma,HL）R-S细胞中的表达和意义。方法：PCR检测HL R-S细胞PTEN基因的外显子以证明PTEN基因是否存在,用原位杂交和免疫组化染色方法检测HL R-S细胞PTEN的表达。结果：20例HL中,PCR均检测到PTEN基因的3、4、5外显子,75.0%（15/20）HL R-S细胞中表达PTEN mRNA较强,同样地,70.0%（14/20）HL R-S细胞中PTEN蛋白表达强,而周围小的淋巴细胞不表达或弱表达PTEN mRNA和PTEN蛋白。结论：PTEN的强表达与R-S细胞形成有密切的关系。     

PTEN和E-钙粘蛋白表达与胃癌浸润转移和预后的关系

目的探讨胃癌组织中PTEN和E-钙粘蛋白的表达、相互关系及意义。方法应用免疫组化SP技术检测80例胃癌组织中PTEN和E-钙粘蛋白的表达。结果胃癌组织中PTEN高表达率和E-钙粘蛋白正常表达率分别为43.8%(35/80)和41.3%(33/80),与肿瘤分化程度、浸润深度、淋巴结转移和肿瘤分期显著相关;PTEN与E-钙粘蛋白表达显著正相关,与病人预后相关,Kaplan-Meier生存曲线分析显示PTEN高表达和E-钙粘蛋白正常表达者术后累计生存率显著高于PTEN低表达和E-钙粘蛋白异常表达者,PTEN高表达和E-钙粘蛋白正常表达者术后3年、5年生存率高,Log-rank检验差异有显著性。结论胃癌组织中PTEN表达减少,E-钙粘蛋白表达异常,PTEN可能通过调控胃癌组织钙粘蛋白表达,抑制胃癌的浸润和转移,影响病人的预后。     

PTEN基因在宫颈癌中的表达及与预后的关系

[目的]探讨PTEN在宫颈癌中的表达及与宫颈癌预后的关系。[方法]选取该院1994～2003年间收治的79例宫颈鳞癌及1994～2004年间宫颈上皮内瘤样病变(CIN)切片79例,正常子宫颈切片16例。用免疫组化(S-P)的方法对其PTEN基因表达进行检测。比较PTEN在正常子宫颈、宫颈CIN及宫颈癌中表达的差异,分析PTEN与宫颈癌患者临床病理特点及预后的关系。[结果]正常宫颈PTEN表达阳性率为93.75%(15/16),CIN为58.23%(46/79),宫颈癌为37.97%(30/79),差异有显著性(P<0.05)。宫颈癌患者的淋巴转移与PTEN表达显著相关(P<0.05)。宫颈癌患者的年龄、分期、病理分级、预后与PTEN表达无显著相关性。多因素COX回归分析显示,PTEN并非独立的预后影响因素。[结论]PTEN基因在宫颈组织从癌前病变向宫颈癌演变的过程中有重要作用;PTEN基因表达与宫颈癌患者的淋巴转移显著相关,不是宫颈癌的独立预后影响因素。     

PTEN在肝癌中低表达的意义

目的探讨PTEN表达与肝细胞癌发生、发展的关系.方法检测PTEN在肝癌组织和肝癌细胞系中的表达情况,以观察该基因与肝癌病理分级、转移和预后的关系.结果肝癌中PTEN表达阴性率为30.16%（19/63）,显著高于正常肝组织0（0/8）和肝硬化组织7.15%（1/14）.随着恶性程度的增高,PTEN表达阴性率随之增加.PTEN表达阴性与是否转移及预后显著相关.PTEN在人肝癌细胞系HHCC中也不表达.结论抑癌基因PTEN低表达多见于肝细胞肝癌进展期,并与肝细胞肝癌分化程度、是否转移以及临床预后相关.     

结直肠癌中PTEN蛋白的表达

目的探讨结直肠癌中PTEN蛋白的表达及其与侵袭和转移的关系。方法应用免疫组化SP法检测67例结直肠癌中PTEN、Ecad、MMP2的表达情况,5例正常大肠黏膜作对照。结果PTEN蛋白表达定位于细胞质。与正常大肠黏膜相比,癌组织中PTEN表达明显降低,并随分化程度降低呈递减趋势;淋巴结转移组明显低于无淋巴结转移组;与浸润深度呈负相关。结直肠癌中PTEN表达与Ecad呈正相关,与MMP2呈负相关;淋巴结转移组PTEN、Ecad低表达且MMP2高表达的人数明显高于无淋巴结转移组。结论PTEN、Ecad低表达,MMP2高表达在结直肠癌的侵袭和转移过程中可能起协同作用,联合检测可为结直肠癌生物学行为判定和进一步的研究和治疗提供有效病理学依据。     

FTEN在肝癌中表达缺失的意义及其体外转染对人肝癌细胞系的作用

目的探讨PTEN表达与肝细胞癌发生、发展的关系,观察体外转染外源性PTEN对肝癌细胞的生长、细胞周期和超微结构的影响.方法检测PTEN在肝癌组织和肝癌细胞系中的表达缺失情况,以观察该基因与肝癌病理分级、转移和预后的关系.将含PTEN的反转录病毒载体及空载体转入人肝癌细胞系HHCC,观察转染前后细胞的生长、超微结构、细胞周期及裸鼠致瘤能力改变情况.结果肝癌中PTEN表达缺失率为30.16%(19/63),显著高于正常肝组织0(0/8)和肝硬化组织7.15%(1/14).随着恶性程度的增高,PTEN表达缺失率随之增加.PTEN表达缺失与转移及预后显著相关.PTEN在人肝癌细胞系hHCC中也不表达.将抑癌基因PTEN转入后,hH-CC细胞生长明显受到抑制,细胞超微结构失去部分恶性表型特征,细胞周期由G1→S0期受抑制,并出现凋亡峰,体外成瘤能力下降.结论抑癌基因PTEN失表达多见于肝细胞肝癌进展期,并与肝细胞肝癌分化程度、是否转移以及临床预后相关;体外PTEN的转入可以明显地抑制HHCC生长、体外成瘤能力.     

Reduced expression of PTEN protein and its prognostic implications in invasive ductal carcinoma of the breast

OBJECTIVE: The PTEN tumor suppressor gene has been demonstrated to be inactivated in a variety of human tumors. In breast cancer, the PTEN gene mutation is not commonly found whereas loss of heterozygosity affecting the PTEN locus is frequently found. The aim of this study was to analyze PTEN protein expression in breast cancer and to evaluate the prognostic significance of PTEN protein expression. METHODS: Paraffin-embedded sections ofinvasive ductal carcinoma of the breast were immunohistochemically stained for PTEN protein expression in 236 breast cancers. The immunohistochemical expression of breast cancer cells was judged to be either normal or reduced compared with the PTEN protein expression of the normal mammary gland. Results: The expression of PTEN protein was found to have decreased in 67 (28%) of 236 breast cancers. The reduced expression correlated with lymph node metastasis (p = 0.0371), but not with tumor size, nuclear grade, MIB-1 counts or p53 protein expression. Univariate analysis indicated that patients with a reduced PTEN expression had a shorter disease-free survival (DFS) than those with a normal PTEN expression (p = 0.0174). Univariate analyses also determined tumor size, lymph node metastases, nuclear grade, MIB-1 counts, p53 protein as well as PTEN protein expression to be significant factors for DFS, while multivariate analysis determined lymph node metastases and the MIB-1 counts to be independent significant factors for DFS. CONCLUSIONS: The inactivation of PTEN, demonstrated by a reduced expression of PTEN protein by immunohistochemistry, was found in about one third of all breast cancers. The reduced expression of PTEN protein correlated with lymph node metastases and a worse prognosis in the patients with breast cancer.     

The biochemical and clinical implications of phosphatase and tensin homolog deleted on chromosome ten in different cancers

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) is widely known as a tumor suppressor gene. It is located on chromosome 10q23 with 200 kb, and has dual activity of both protein and lipid phosphatase. In addition, as a targeted gene in multiple pathways, PTEN has a variety of physiological activities, such as those regulating the cell cycle, inducing cell apoptosis, and inhibiting cell invasion, etc. The PTEN gene have been identified in many kinds of cancers due to its mutations, deletions and inactivation, such as lung cancer, liver cancer, and breast cancer, and they are closely connected with the genesis and progression of cancers. To a large extent, the tumor suppressive function of PTEN is realized through its inhibition of the PI3K/AKT signaling pathway which controls cells apoptosis and development. In addition, PTEN loss has been associated with the prognosis of many cancers, such as lung cancer, liver cancer, and breast cancer. PTEN gene is related to many cancers and their pathological development. On the basis of a large number of related studies, this study describes in detail the structure, regulation, function and classical signal pathways of PTEN, as well as the relationship between various tumors related to PTEN. In addition, some drug studies targeting PTEN/PI3K/AKT/mTOR are also introduced in order to provide some directions for experimental research and clinical treatment of tumors.     

Lapatinib antitumor activity is not dependent upon phosphatase and tensin homologue deleted on chromosome 10 in ErbB2-overexpressing breast cancers

Trastuzumab antitumor activity in ErbB2-overexpressing breast cancers seems to be dependent upon the presence of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), a phosphatase that dampens phosphatidylinositol 3-kinase-Akt signaling. Consequently, PTEN deficiency, which occurs in 50% of breast cancers, predicts for resistance to trastuzumab monotherapy. Here, we show that lapatinib, a small-molecule inhibitor of ErbB1 and ErbB2 tyrosine kinases, exerts its antitumor activity in a PTEN-independent manner. Steady-state phosphorylated ErbB2 (p-ErbB2) and p-Akt (S473) protein levels were inhibited within 30 min following lapatinib but not in response to trastuzumab in BT474 and Au565 cells (two ErbB2-overexpressing breast cancer cell lines that are sensitive to the proapoptotic effects of lapatinib). Whereas trastuzumab reportedly inhibits SRC phosphorylation (Y416), which in turn reduced SRC-ErbB2 protein interactions, lapatinib had no effect on either variable. To assess the potential functional role that PTEN might play in lapatinib antitumor activity, we selectively knocked down PTEN in BT474 and Au565 cells using small interfering RNA transfection. Loss of PTEN did not affect induction of tumor cell apoptosis by lapatinib in either cell line. In addition, lapatinib inhibited Akt phosphorylation in MDA-MB-468 cells, an ErbB1-expressing/ErbB2 non-overexpressing breast cancer line, despite their PTEN-null status. Moreover, patients with ErbB2-overexpressing inflammatory breast cancers responded to lapatinib monotherapy regardless of PTEN status. Thus, lapatinib seems to exert its antitumor activity in ErbB2-overexpressing breast cancers in a PTEN-independent manner. These data emphasize the importance of assessing PTEN status in tumors when selecting ErbB2-targeted therapies in patients with breast cancer.     

腋淋巴结阴性乳腺癌中基因表达PTEN和微血管密度的关系及意义

目的:研究腋淋巴结阴性(ph node negative,LN N)乳腺癌中PTEN蛋白的表达,探讨与微血管密度lym(VD)及患者预后的关系。方法:应用免疫组化S-P法检测81例LN N乳腺癌及20例癌旁乳腺组织中PTEN和MCD34蛋白的表达,分析与各临床病理因素和预后的关系。结果:32.6%的患者PTEN蛋白表达减低或完全阴性表达,PTEN与乳腺癌病理分级,ER状态和复发转移显著相关;PTEN阳性表达组的5年生存率(83.7%)明显高于阴性表达组(66.7%)(P<0.05);PTEN的表达与M VD呈显著的负相关关系(r=-0.552,P<0.01)。结论:PTEN缺失是乳腺癌发生过程中的多发事件,并有抑制血管生成的作用,PTEN缺失和高M V D的LNN乳腺癌患者5年生存率低,两者的检测有助于提高评估LN N乳腺癌患者术后生存的准确性。     

PTEN suppresses breast cancer cell growth by phosphatase activity-dependent G1 arrest followed by cell death

PTEN/MMAC1/TEP1, a tumor suppressor gene, is frequently mutated in a variety of human cancers. Germ-line mutations of phosphatase and tensin homolog, deleted on chromosome ten (PTEN) are found in two inherited hamartoma tumor syndromes: Cowden syndrome, which has a high risk of breast, thyroid, and other cancers; and Bannayan-Zonana syndrome, a related disorder. PTEN encodes a phosphatase that recognizes both protein substrates and phosphatidylinositol-3,4,5-triphosphate. The lipid phosphatase activity of PTEN seems to be important for growth suppression through inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. We established clones with stable PTEN expression controlled by a tetracycline-inducible system to examine the consequences of increased levels of wild-type and mutant PTEN expression in a well-characterized breast cancer line, MCF-7. When we overexpressed PTEN in MCF-7, growth suppression was observed, but only if PTEN phosphatase activity is preserved. The initial growth suppression was attributable to G1 cell cycle arrest, whereas subsequent growth suppression was attributable to a combination of G1 arrest and cell death. Of note, the decrease in Akt phosphorylation preceded the onset-of suppression of cell growth. Treatment of MCF-7 cells with wortmannin, a PI3K inhibitor, caused cell growth inhibition in a way similar to the effects of overexpression of PTEN in this cell. In general, the inverse correlation between PTEN protein level and Akt phosphorylation was found in a panel of breast cancer cell lines. Therefore, PTEN appears to suppress breast cancer growth through down-regulating PI3K signaling, which leads to the blockage of cell cycle progression and the induction of cell death, in a sequential manner.     

The impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen treatment in breast cancer patients

Tamoxifen is a standard therapeutical treatment in patients with estrogen receptor positive breast carcinoma. However, less than 50% of estrogen receptor positive breast cancers do not respond to tamoxifen treatment whereas 40% of tumors that initially respond to treatment develop resistance over time. The underlying mechanisms for tamoxifen resistance are probably multifactorial but remain largely unknown. The primary aim of this study was to investigate the impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen by analyzing loss of heterozygosity (LOH) and immunohystochemical expression of PTEN in 49 primary breast carcinomas of patients treated with tamoxifen as the only adjuvant therapy. The effect of PTEN inactivation on breast cancer progression and disease outcome was also analyzed. Reduced or completely lost PTEN expression was observed in 55.1% of samples, while 63.3% of samples displayed LOH of PTEN gene. Inactivation of PTEN immunoexpression significantly correlated with the PTEN loss of heterozygosity, suggesting LOH as the most important genetic mechanism for the reduction or complete loss of PTEN expression in primary breast carcinoma. Most importantly, LOH of PTEN and consequential reduction of its immunoexpression showed significant correlation with the recurrence of the disease. Besides, our study revealed that LOH of PTEN tumor suppressor was significantly associated with shorter disease free survival, breast cancer specific survival and overall survival. In summary, our results imply that LOH of PTEN could be used as a good prognostic characteristic for the outcome of breast cancer patients treated with tamoxifen.     

PTEN loss in the continuum of common cancers, rare syndromes and mouse models

PTEN is among the most frequently inactivated tumour suppressor genes in sporadic cancer. PTEN has dual protein and lipid phosphatase activity, and its tumour suppressor activity is dependent on its lipid phosphatase activity, which negatively regulates the PI3K-AKT-mTOR pathway. Germline mutations in PTEN have been described in a variety of rare syndromes that are collectively known as the PTEN hamartoma tumour syndromes (PHTS). Cowden syndrome is the best-described syndrome within PHTS, with approximately 80% of patients having germline PTEN mutations. Patients with Cowden syndrome have an increased incidence of cancers of the breast, thyroid and endometrium, which correspond to sporadic tumour types that commonly exhibit somatic PTEN inactivation. Pten deletion in mice leads to Cowden syndrome-like phenotypes, and tissue-specific Pten deletion has provided clues to the role of PTEN mutation and loss in specific tumour types. Studying PTEN in the continuum of rare syndromes, common cancers and mouse models provides insight into the role of PTEN in tumorigenesis and will inform targeted drug development.     

PTEN activation contributes to tumor inhibition by trastuzumab, and loss of PTEN predicts trastuzumab resistance in patients

The ErbB2-targeting antibody, trastuzumab (Herceptin), has remarkable therapeutic efficacy in certain patients with ErbB2-overexpressing tumors. The overall trastuzumab response rate, however, is limited and what determines trastuzumab response is poorly understood. Here we report that PTEN activation contributes to trastuzumab's antitumor activity. Trastuzumab treatment quickly increased PTEN membrane localization and phosphatase activity by reducing PTEN tyrosine phosphorylation via Src inhibition. Reducing PTEN in breast cancer cells by antisense oligonucleotides conferred trastuzumab resistance in vitro and in vivo. Patients with PTEN-deficient breast cancers had significantly poorer responses to trastuzumab-based therapy than those with normal PTEN. Thus, PTEN deficiency is a powerful predictor for trastuzumab resistance. Additionally, PI3K inhibitors rescued PTEN loss-induced trastuzumab resistance, suggesting that PI3K-targeting therapies could overcome this resistance.