PTEN抑癌基因在乳腺癌中的研究进展

乳腺癌是我国女性常见的一种恶性肿瘤,迄今其发生发展的分子机制还不完全清楚。PTEN基因是1997年发现并被克隆的第一个具有磷酸酶活性的抑癌基因,大量的研究表明,乳腺癌的发生常伴有PTEN蛋白的表达缺失或减弱,提示该基因的突变失活与乳腺癌的发生、发展及预后密切相关。本文就抑癌基因PTEN与乳腺癌的关系研究进展加以综述。     

PTEN抑癌基因在乳腺癌中的研究进展

乳腺癌是我国女性常见的一种恶性肿瘤，迄今其发生发展的分子机制还不完全清楚。PTEN基因是1997年发现并被克隆的第一个具有磷酸酶活性的抑癌基因，大量的研究表明，乳腺癌的发生常伴有PTEN蛋白的表达缺失或减弱，提示该基因的突变失活与乳腺癌的发生、发展及预后密切相关。本文就抑癌基因PTEN与乳腺癌的关系研究进展加以综述。     

PTEN基因的研究进展

PTEN基因是迄今发现的第一个具有双特异性磷酸酶活性的抑癌基因 ,该基因的突变失活与人类多数恶性肿瘤的发生发展密切相关 ,PTEN蛋白在细胞的生长发育、信号传导和细胞凋亡过程中起重要的作用     

PTEN基因的研究进展

PTEN基因是迄今发现的第一个具有双特异性磷酸酶活性的抑癌基因,该基因的突变失活怀人类多数恶性肿瘤的发生发展密切相关,PTEN蛋白在细胞的生长发育、信号传导和细胞凋亡过程中起重要的作用。     

PTEN基因与肿瘤

PTEN基因是迄今发现的第一个具有双特异性磷酸酶活性的抑癌基因,该基因的突变失活与人类多数恶性肿瘤的发生发展密切相关,PIEN蛋白在细胞的生长发育、信号转导和细胞凋亡过程中起重要作用.     

PTEN基因在泌尿系统肿瘤中的研究进展

PTEN基因是迄今为止发现的第一个具有双特异性磷酸酶活性的抑癌基因 ,该基因的突变失活与多种肿瘤的发生有密切的关系。PTEN基因突变失活在泌尿系统肿瘤发生、发展中起着重要的作用。     

PTEN与恶性肿瘤的关系

近年发现的抑癌基因PTEN的结构中存在着2个主要的结构功能域,即N-端功能区和-C端结构域。其具有双特异性脂酶性质,在多种进展期肿瘤组织中存在着不同程度的突变与丢失。PTEN通过复杂的信号转导网络(如PI3K/AKT信号通路、FAK和MAPK信号通路、P53/PTEN/Mdm2信号网络等)来抑制细胞周期、干预细胞凋亡、抑制肿瘤的侵袭和转移、抑制肿瘤血管形成等。PTEN的突变与丢失可导致其抑癌功能减弱甚至丧失,与肿瘤的发生发展密切相关。     

抑癌基因PTEN研究现状与展望

PTEN基因是由 Steck等在 1997年克隆到的一个候选的抑制基因 ,定位于 10 q2 3.3,该基因的突变与缺失与人类多种肿瘤的发生发展及预后有关。本文对 PTEN基因的结构与功能及其在肿瘤中突变和缺失的研究新进展进行了综述     

食管癌Rb蛋白表达与临床病理的关系

食管癌Ｒｂ蛋白表达与临床病理的关系李建民徐树明视网膜母细胞瘤基因（Ｒｂ基因）是人体第一个肿瘤抑制基因，迄今研究发现在正常人体组织中Ｒｂ基因有不同程度的表达，而且其突变或异常表达也被发现在许多人体肿瘤组织中。我们用免疫组织化学方法，研究食管癌Ｒｂ基因蛋...     

抑癌基因PTEN研究现状与展望

PTEN基因是由Steck等在1997年克隆到的一个候选的抑制基因，定位于10q23.3，该基因的突变与缺陷失与与人类多种肿瘤的发生发展及预后后有关，本对PTEN基因的结构与功能及其在肿瘤中突变和缺失的研究新进展进行了综述。；     

胃癌中survivin、PTEN、cyclinD1和p53基因的表达及其相关性

目的　探讨survivin基因表达与胃癌生物学行为及PTEN、cyclinD1、p5 3和凋亡指数 (AI)的相关性。 方法　用免疫组化EnVision法检测 15 6例胃癌组织、4 6例正常胃黏膜和 4 6例癌旁不典型增生组织中survivin、PTEN、cyclinD1和 p5 3的表达以及AI。结果　survivin、PTEN、cyclinD1和p5 3的阳性检测率分别为 6 5 %、4 1%、6 1%和 5 8%。survivin未见核内表达。survivin、cyclinD1和 p5 3表达与胃癌的组织学类型相关 (P <0 0 1,P <0 0 5和P <0 0 1) ;survivin和cyclinD1表达与胃癌的浸润深度相关 (P <0 0 1和P <0 0 5 ) ;4种基因蛋白表达均与淋巴结转移相关 ,survivin的表达与p5 3和cyclin阳性表达呈正相关 ,与PTEN的阳性表达呈负相关 ;survivin、p5 3和cyclinD1高表达均有患者术后 <3年生存期相关 (P <0 0 5 ,P <0 0 1和P<0 0 1) ;survivin阳性组的平均AI为 0 6 1,明显低于survivin阴性组 (P <0 0 1) ;PTEN阳性组明显高于阴性组 (P <0 0 1)。结论　survivin、PTEN、p5 3和cyclinD1基因在胃癌的发生、发展中起着不同程度的作用 ,它们的检测对胃癌恶性度的判定、预后和进一步治疗提供有效的依据。survivin、p5 3和cyclinD1的过表达可作为判断肿瘤术后差的指标     

Molecular genetic alterations in endometrioid carcinomas of the ovary: similar frequency of beta-catenin abnormalities but lower rate of microsatellite instability and PTEN alterations than in uterine endometrioid carcinomas

Endometrioid carcinomas of the ovary closely resemble their uterine counterparts. It has been suggested that the former tumors have the same molecular alterations (microsatellite instability [MSI], PTEN, and beta-catenin) described in endometrioid carcinomas of the uterus. We analyzed 55 ovarian carcinomas, including 22 endometrioid, 18 clear cell, and 15 mixed types. MSI was detected in 5 of 39 cases (13%). MLH1 promoter hypermethylation was identified in 2 of the 5 MSI-positive tumors. PTEN was mutated in 5 of 54 cases (9%); of these, 3 had MSI and exhibited frameshift mutations in short-coding mononucleotide repeats. Beta-catenin nuclear expression was detected in 11 of 54 cases (20%) by immunostaining; of these, 7 exhibited CTNNB1 gene mutations. These alterations were found more frequently in endometrioid carcinomas than in tumors of the other 2 groups. Among the former tumors, MSI was detected in 3 of 17 cases (17.5%); PTEN mutations, in 3 of 21 (14%); and beta-catenin, in 8 of 21 (38%). The molecular alterations were found more often in tumors associated with endometriosis than in tumors without endometriosis. Six endometrioid tumors demonstrating matrix metalloproteinase-7 (MMP-7) immunoreactivity with nuclear accumulation of beta-catenin had good outcomes, in contrast to poor outcomes in 7 of 9 predominantly nonendometrioid tumors demonstrating expression of MMP-7 only. We found a similar frequency of beta-catenin abnormalities but lower rates of MSI and PTEN alterations than in uterine endometrioid carcinomas. Alterations in beta-catenin and PTEN genes, as well as MSI, are frequent in low-stage ovarian carcinomas of endometrioid type that have a favorable prognosis.     

PIK3CA gene mutations in endometrial carcinoma: correlation with PTEN and K-RAS alterations

Alterations in the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway are common in endometrial carcinoma. Inactivation of the tumor suppressor gene PTEN leads to a constitutively active PI3K pathway, which plays a role in the early steps of endometrial tumorigenesis. Other alterations in the PI3K/AKT pathway are mutations in the PIK3CA gene, which encode the p110alpha catalytic subunit of PI3K. PIK3CA mutations cluster to the helical (exon 9) and the kinase (exon 20) domains of the gene. In endometrial carcinomas, PIK3CA mutations have been found to coexist frequently with PTEN mutations, but it is not clear whether they occur in cells with monoallelic or biallelic inactivation of PTEN. In the present study we have evaluated PIK3CA mutational status in a series of 33 endometrial carcinomas, previously screened for microsatellite instability and mutations in PTEN, K-RAS, and CTNNB-1. The tumors were also evaluated for loss of heterozygosity on 10q23 and hypermethylation of the promoter region of PTEN/psiPTEN to assess the monoallelic or biallelic inactivation status of PTEN. PIK3CA mutations were detected in 8 (24%) of the 33 cases. Seven mutations were located in exon 20 and 1 in exon 9. PTEN alterations were found in 19 cases (57%). Biallelic inactivation of PTEN was demonstrated in 11 tumors, whereas 8 tumors exhibited alteration in only 1 of the 2 alleles. PIK3CA mutations coexisted with monoallelic alterations of PTEN in 4 cases (2 mutations and 2 allelic imbalances), with biallelic PTEN inactivation in 1 case (mutation and promoter methylation), and 3 tumors showed PIK3CA mutations in association with wild-type PTEN. PIK3CA mutations did not correlate with microsatellite instability or mutations in CTNNB-1. However, PIK3CA and K-RAS mutations (8 cases) were mutually exclusive alterations. In summary, the results confirm that PIK3CA mutations are frequent in endometrial carcinoma and support the hypothesis that PIK3CA mutations may have an additive effect to PTEN monoallelic inactivation in endometrial carcinoma.     

PTEN mutational spectra,expression levels,and subcellular localization in microsatellite stable and unstable colorectal cancers

PTEN on 10q23.3 encodes a dual-specificity phosphatase that negatively regulates the phosphoinositol-3-kinase/Akt pathway and mediates cell-cycle arrest and apoptosis. Germline PTEN mutations cause Cowden syndrome and a range of several different hamartoma-tumor syndromes. Hereditary nonpolyposis colon cancer (HNPCC) syndrome is characterized by germline mutations in the mismatch repair (MMR) genes and by microsatellite instability (MSI) in component tumors. Although both colorectal carcinoma and endometrial carcinoma are the most frequent component cancers in HNPCC, only endometrial cancer has been shown to be a minor component of Cowden syndrome. We have demonstrated that somatic inactivation of PTEN is involved in both sporadic endometrial cancers and HNPCC-related endometrial cancers but with different mutational spectra and different relationships to MSI. In the current study, we sought to determine the relationship of PTEN mutation, 10q23 loss of heterozygosity, PTEN expression, and MSI status in colorectal cancers (CRCs). Among 11 HNPCC CRCs, 32 MSI+ sporadic cancers, and 39 MSI- tumors, loss of heterozygosity at 10q23.3 was found in 0%, 8%, and 19%, respectively. Somatic mutations were found in 18% (2 of 11) of the HNPCC CRCs and 13% (4 of 32) of the MSI+ sporadic tumors, but not in MSI- cancers (P = 0.015). All somatic mutations occurred in the two 6(A) coding mononucleotide tracts in PTEN, suggestive of the etiological role of the deficient MMR. Immunohistochemical analysis revealed 31% (14 of 45) of the HNPCC CRCs and 41% (9 of 22) of the MSI+ sporadic tumors with absent or depressed PTEN expression. Approximately 17% (4 of 23) of the MSI- CRCs had decreased PTEN expression, and no MSI- tumor had complete loss of PTEN expression. Among the five HNPCC or MSI+ sporadic CRCs carrying frameshift somatic mutations with immunohistochemistry data, three had lost all PTEN expression, one showed weak PTEN expression levels, and one had mixed tumor cell populations with weak and moderate expression levels. These results suggest that PTEN frameshift mutations in HNPCC and sporadic MSI+ tumors are a consequence of mismatch repair deficiency. Further, hemizygous deletions in MSI- CRCs lead to loss or reduction of PTEN protein levels and contribute to tumor progression. Finally, our data also suggest that epigenetic inactivation of PTEN, including differential subcellular compartmentalization, occurs in CRCs.     

PTEN mutations do not cause nuclear beta-catenin accumulation in endometrial carcinomas

PTEN: and beta-catenin mutations constitute the predominant genetic alterations in endometrioid carcinomas of the endometrium. PTEN encodes a dual-specificity phosphatase with lipid phosphatase and protein tyrosine phosphatase activities that regulate both apoptosis and interactions with the extracellular matrix. Recent studies have associated PTEN mutations with tumorigenesis of prostate carcinoma via the Wnt signaling pathway, leading to nuclear beta-catenin accumulation. To elucidate the potential interaction of PTEN and beta-catenin in endometrial cancer, we performed mutation analyses of the entire PTEN gene and of exon 3 of the beta-catenin gene that is most frequently targeted by mutations. A total of 82 endometrial carcinomas comprising 62 type I endometrioid carcinomas and 20 type II high-grade carcinomas were investigated. In addition in a subset of 22 carcinomas, the intracellular beta-catenin distribution was analyzed by immunohistochemistry. Overall, 20 (24.4%) of 82 tumors revealed mutations in the PTEN gene, and 16 (19.5%) of 82, in the beta-catenin gene. Six tumors (7.3%) showed mutations in both the PTEN and beta-catenin gene. Mutations were mainly detected in endometrioid carcinomas of the endometrium. As expected, a striking nuclear accumulation of beta-catenin could be shown in tumors with beta-catenin mutations. In the vast majority of tumors with PTEN mutations, a regular staining pattern of the cytoplasmic and membranous compartments was found. We therefore conclude that, in contrast to prostate cancer, mutations in the PTEN gene seem not to affect cellular distribution of the beta-catenin protein in endometrial carcinomas.     

Role of PTEN and MMP-7 expression in growth, invasion, metastasis and angiogenesis of gastric carcinoma

To investigate the role of PTEN and matrix metalloproteinase-7 (MMP-7) expression in tumorigenesis and progression of gastric carcinoma, their expression in 113 gastric carcinomas was studied by immunohistochemistry. Microvessel density (MVD) was counted using the anti-CD34 antibody. The expressions of PTEN and MMP-7, and MVD were compared with the clinicopathological parameters of tumors, and the relationship between PTEN and MMP-7 expression and MVD was analyzed. It was found that PTEN was expressed less frequently in primary gastric carcinoma cells than in adjacent epithelial cells (P < 0.05), whereas this was reversed for MMP-7 (P < 0.05). PTEN expression was negatively correlated with invasion, metastasis, growth pattern, Lauren's classification and histological classification (P < 0.05). Matrix metalloproteinase-7 expression was positively associated with tumor size, Borrmann's classification, invasive depth, metastasis and TNM staging (P < 0.05), but negative with PTEN expression (P < 0.05). A positive correlation of MVD with tumor size, invasive depth, metastasis and TNM staging was found (P < 0.05). Microvessel density depended on decreased PTEN expression and increased MMP-7 expression (P < 0.05). The results of the present study suggested that down-regulated PTEN expression and up-regulated MMP-7 expression were greatly implicated in tumorigenesis and progression of gastric carcinoma. Close correlation between PTEN on MMP-7 expression provided a novel insight into the regulatory effects of PTEN on MMP-7 expression in gastric carcinoma.     

肾细胞癌中抑癌基因PTEN的表达及生物学意义

目的 :研究抑癌基因PTEN在肾细胞癌的表达及其生物学意义。方法 :应用免疫组织化学S P法检测 5例正常肾组织、18例癌旁肾组织和 40例肾细胞癌组织中抑癌基因PTEN的表达。结果 :5例正常肾组织和 18例癌旁肾组织均有较强的PTEN蛋白的表达 ,二者PTEN蛋白的表达强度、阳性细胞的分布形式无差异。抑癌基因PTEN在肾细胞癌中的表达不同于正常肾组织和癌旁肾组织 ,12 5 %的肾细胞癌呈PTEN蛋白阴性 ;17 5 %的肾细胞癌PTEN蛋白呈弱阳性 ;70 %的肾细胞癌PTEN蛋白呈阳性或强阳性 ,与癌旁组织PTEN蛋白的染色强度无差异。PTEN蛋白阴性的肾细胞癌 ,肾门淋巴结转移率为80 % ;PTEN蛋白阳性的肾细胞癌 ,肾门淋巴结转移率为 2 0 %。PTEN蛋白阴性肾细胞癌的肾门淋巴结转移率与PTEN阳性肾细胞癌的肾门淋巴结转移率比较 ,差异有显著性 (P <0 0 5 )。结论 :肾细胞癌中存在着抑癌基因PTEN的表达缺失和异常 ;抑癌基因PTEN的表达异常可能与肾细胞癌的发生、发展有关 ,抑癌基因PTEN是肾细胞癌的一种新的相关基因。     

Reduced PTEN expression is associated with poor outcome and angiogenesis in invasive ductal carcinoma of the breast.

Loss of PTEN expression has been associated with advanced stages of tumor. Tumor angiogenesis is involved in tumor progression. In breast cancer, a high frequency of mutations of the PTEN locus has been reported. However, the prognostic importance of PTEN expression and its correlation with angiogenesis in breast cancer have not been well established. Formalin-fixed, paraffin-embedded tissues from 99 women with a primary diagnosis of invasive ductal carcinoma were evaluated for PTEN expression by immunohistochemical methods. The microvessel density (MVD) was also studied by immunohistochemical labeling of endothelial cells with CD34 antibody. Computerized image analysis was used to evaluate MVD. Reduced PTEN expression was seen in 27.3% of invasive ductal carcinoma. The MVD ranged from 22.0 to 197.0, with a median value of 58.5 (65.4 +/- 27.9). Reduced PTEN expression correlated with lymph node status (P < 0.01), tumor grade (P < 0.05), and tumor-node-metastasis (TNM) stage (P < 0.05). There was a statistically significant correlation between reduced PTEN expression and increased MVD (P < 0.05). The mean MVD was higher in reduced PTEN-expressive tumors, irrespective of stage, compared with normal PTEN-expressive tumors with the same stage. On multivariate analysis, only TNM stage and reduced PTEN expression correlated with survival. Our results suggest that reduced PTEN expression may be an independent prognostic indicator in patients with invasive ductal carcinoma. PTEN loss may be associated with increased tumor angiogenesis.     

Molecular characterization of uterine clear cell carcinoma.

Clinicopathological studies support a broad classification of endometrial carcinoma into two major types, designated as type I and type II, which correlate with their biological behavior. More recently, molecular studies have provided further insights into this classification scheme by elucidating the genetic events involved in the development and progression of endometrial carcinoma. Microsatellite instability and mutations in the PTEN gene have been widely associated with type I (endometrioid) endometrial carcinoma, while p53 mutations have been identified in the majority of type II endometrial carcinoma, of which uterine serous carcinoma is the prototype. Uterine clear cell carcinoma (UCC) is an uncommon variant of endometrial carcinoma, and clinicopathological studies have produced conflicting results regarding its biological behavior with 5-year survival ranging from 21 to 75%. The molecular characteristics of endometrioid and serous carcinoma have been studied extensively; however, there have been few molecular genetic studies of the clear cell subtype. In this study, we evaluated 16 UCCs (11 pure and 5 mixed) for mutations in the p53 gene, PTEN gene and for microsatellite instability. Although we found that these alterations were uncommon in pure clear cell carcinomas, all three were identified. In addition, two cases of mixed serous and clear cell carcinoma showed an identical mutation of the p53 gene in the histologically distinct components and one case of mixed clear cell and endometrioid carcinoma had identical mutations in the PTEN and p53 genes, and microsatellite instability in both components. Our data suggest that UCC represent a heterogeneous group of tumors that arise via different pathogenetic pathways. Additional molecular studies of pure clear cell carcinoma are required to further elucidate the genetic pathways involved in its development and progression.