Germline PTEN mutations are rare and highly penetrant

Cowden syndrome (multiple hamartoma syndrome, MIM 158350) is an early onset syndrome characterized by multiple hamartomas in the skin, mucous membranes, breast, thyroid and endometrium. Patients with Cowden syndrome have increased risk of breast cancer, thyroid cancer and endometrial cancer. In 1997 germline mutations in PTEN were demonstrated to cause Cowden syndrome. We report the results of diagnostic and predictive testing in all families with Cowden syndrome or suspected Cowden syndrome registered at the Norwegian cancer family clinics. PTEN mutations were found in all six families meeting the clinical criteria for Cowden syndrome, in none of the two families assumed to have Cowden syndrome but not fulfilling the criteria, and in none of the eight families selected in our computerized medical files to have a combination of breast and thyroid cancers. Age-related penetrances for the various neoplasms are given. All families but one were small and de novo mutations were found.     

PTEN基因单核苷酸多态性与乳腺癌的关系

目的:研究PTEN基因-9C/G单核苷酸多态性与中国汉族女性人群乳腺癌之间的相关性。方法:采用基于人群的病例-对照研究,以聚合酶链反应-限制性片段长度多态性(PCR-RFLP)方法进行基因分型,检测210例中国汉族女性乳腺癌患者和210例健康女性的PTEN基因-9C/G多态性。结果:PTEN基因-9C/G位点(rs11202592)多态性基因型分布频率在两组间比较无显著性差异(P=0.862)。PTEN基因-9C/G单核甘酸多态性不同基因型间在ER、Her-2表达上无显著性差异(P>0.05)。结论:PTEN基因-9C/G位点多态性与中国汉族女性乳腺癌易感性无明显关联,ER、HER-2表达同此位点多态性也无明显关联。     

PPARγ蛋白与PTEN蛋白表达及其相关性在人乳腺癌中的研究

目的：探讨人乳腺癌组织中过氧化物酶体增殖因子激活受体（peroxisomeproliferators—activatedre—ceptorgmma,PPARY）和第十染色体同源丢失性磷酸酶一张力蛋白基因（phosphataseandtensinhomologydele—tedonchromosometen,PTEN）蛋白表达的相关性。方法：采用免疫组化S—P法,检测20例人乳腺癌组织、癌旁组织中PTEN与PPARγ的表达情况。结果：PPARγ和PTEN的表达与乳腺癌患者年龄、肿瘤直径大小、TNM分期、病理学类型、孕激素受体（PR）及Her-2表达情况无显著相关性（P〉0．05）;肿瘤组织高分化组患者的PPARγ蛋白表达阳性率显著高于低分化组（P〈0．05）;腋窝淋巴结转移阴性者PTEN的表达显著高于≥4个淋巴结转移者（P〈0．0125）;雌激素受体（ER）阳性者PTEN的表达显著高于ER阴性者（P〈0．05）;癌旁组织PPARγ和PTEN的表达显著高于癌肿组织（P〈0．01）;PPARγ与PTEN蛋白在乳腺癌的表达成显著正相关（P〈0．01）。结论：人乳腺癌中PPARγ与PTEN蛋白表达相关联,并可能参与乳腺癌的发生、发展、浸润与转移。     

Metformin and erlotinib synergize to inhibit basal breast cancer

Basal-like breast cancers (BBCs) are enriched for increased EGFR expression and decreased expression of PTEN. We found that treatment with metformin and erlotinib synergistically induced apoptosis in a subset of BBC cell lines. The drug combination led to enhanced reduction of EGFR, AKT, S6 and 4EBP1 phosphorylation, as well as prevented colony formation and inhibited mammosphere outgrowth. Our data with other compounds suggested that biguanides combined with EGFR inhibitors have the potential to outperform other targeted drug combinations and could be employed in other breast cancer subtypes, as well as other tumor types, with activated EGFR and PI3K signaling. Analysis of BBC cell line alterations led to the hypothesis that loss of PTEN sensitized cells to the drug combination which was confirmed using isogenic cell line models with and without PTEN expression. Combined metformin and erlotinib led to partial regression of PTEN-null and EGFR-amplified xenografted MDA-MB-468 BBC tumors with evidence of significant apoptosis, reduction of EGFR and AKT signaling, and lack of altered plasma insulin levels. Combined treatment also inhibited xenografted PTEN null HCC-70 BBC cells. Measurement of trough plasma drug levels in xenografted mice and a separately performed pharmacokinetics modeling study support possible clinical translation.     

PIK3CA and PTEN Genes Expressions in Breast Cancer

Background: The phosphatidylinositol-3 kinase (PI3K) intracellular signaling pathway plays an importantrole in breast cancer. The current study aimed to evaluate the expressions of two main regulators of PI3K pathway;phosphatidylinositol-3- kinase catalytic subunit alpha as activator (PIK3CA), and phosphatase and tensin-homologas inhibitor (PTEN), in breast carcinoma tissue, and compare with their expressions in adjacent normal breast tissue.Methods: A total of fifty female patients with breast carcinoma from surgical oncology unit of Alexandria-MainUniversity Hospital were included in this study. The Quantitative Real Time PCR was used to quantify expressions ofPIK3CA and PTEN. Results: PIK3CA mRNA expression was significantly increased in breast cancer tissues comparedto normal breast tissues (P<0.001, Z=5.700), also PTEN mRNA expression was significantly higher in breast carcinomatissue compared to normal breast tissue (P<0.001, Z=5.362). Conclusion: Increased the expressions of PIK3CA andPTEN mRNA in breast cancer tissue compared to normal breast tissue.     

PTEN在乳腺癌及癌前病变中的表达及意义

目的：探讨人第10号染色体缺失的磷酸酶（phosphatase and tensin homolog deleted on chromosometen, PTEN）在乳腺导管上皮不典型增生（ atypical ductal hyperplasia,ADH）、导管内癌（ ductal carcinoma in situ, DCIS）、浸润性导管癌（invasiveductal carcinoma,IDC）三组病变组织中的表达及意义。方法：收集 ADH 60例、DCIS 100例、IDC 165例,利用 Real - time RT - PCR 检测 ADH、DCIS、IDC 病变组织中 PTEN 基因在 mRNA 水平的表达情况;利用 Western - Blot 方法和免疫组织化学技术检测 ADH、DCIS、IDC 病变组织中 PTEN 蛋白的表达情况。结果：Real - time RT - PCR 技术结果显示,ADH 组 PTEN mRNA 表达水平最高,DCIS 组次之,IDC组最低差异具有统计学意义（t =26.661,P <0.05）。Western - Blot 技术检测 PTEN 蛋白在 ADH、DCIS、IDC 三组病变组织中的表达呈逐渐下降趋势,差异具有统计学意义（t =9.355,P <0.05）。免疫组织化学检测 PTEN蛋白在 ADH、DCIS、IDC 三组病变组织中的阳性表达率分别为91.9%、51.0%、36.9%,差异有统计学意义（χ2=54.734,P <0.05）。分析 PTEN 蛋白表达水平与乳腺癌患者临床资料的相关性,结果显示其与患者年龄无相关性（P >0.05）,而与患者的肿瘤分化程度、临床分级及转移有相关性,且差异有统计学意义（χ2=15.8,P <0.05）。结论：无论是在蛋白水平还是 mRNA 水平,PTEN 基因的表达从 ADH 到 DCIS 再到 IDC 呈下降趋势,提示 PTEN 可能参与了乳腺癌发生发展的过程,为日后治疗提供靶点理论依据。     

Reduced PTEN expression in breast cancer cells confers susceptibility to inhibitors of the PI3 kinase/Akt pathway.

The PTEN protein is a lipid phosphatase with putative tumor suppressing abilities, including inhibition of the PI3K/Akt signaling pathway. Inactivating mutations or deletions of the PTEN gene, which result in hyper-activation of the PI3K/Akt signaling pathway, are increasingly being reported in human malignancies, including breast cancer, and have been related to features of poor prognosis and resistance to chemotherapy and hormone therapy. Prior studies in different tumor models have shown that, under conditions of PTEN deficiency, the PI3K/Akt signaling pathway becomes a fundamental proliferative and survival pathway, and that pharmacological inhibition of this pathway results in tumor growth inhibition. This study aimed to explore further this hypothesis in breast cancer cells. To this end, we have determined the growth response to inhibition of the PI3K/Akt signaling pathway in a series of breast cancer cell lines with different PTEN levels. The PTEN-negative cell line displayed greater sensitivity to the growth inhibitory effects of the PI3K inhibitor, LY294002 and rapamycin, an inhibitor of the PI3K/Akt downstream mediator mTOR, compared with the PTEN-positive cell lines. To determine whether or not these differences in response are specifically due to effects of PTEN, we developed a series of cell lines with reduced PTEN protein expression compared with the parental cell line. These reduced PTEN cells demonstrated an increased sensitivity to the anti-proliferative effects induced by LY294002 and rapamycin compared with the parental cells, which corresponded to alterations in cell cycle response. These findings indicate that inhibitors of mTOR, some of which are already in clinical development (CCI-779, an ester of rapamycin), have the potential to be effective in the treatment of breast cancer patients with PTEN-negative tumors and should be evaluated in this setting.     

Role of HER3 expression and PTEN loss in patients with HER2-overexpressing metastatic breast cancer (MBC) who received taxane plus trastuzumab treatment

Background:

The aim of this study was to investigate the role of human epidermal growth factor receptor (HER3) and PTEN expression in patients with HER2-overexpressing metastatic breast cancer (MBC).

Methods:

One hundred twenty-five MBC patients who were treated with taxane plus trastuzumab chemotherapy as first-line therapy were included in this analysis. Immunohistochemical (IHC) staining with HER3 and PTEN antibodies were conducted retrospectively.

Results:

Patients who had negative HER3 staining (62.4%) had a better progression-free survival (PFS) than did those who had positive HER3 staining (P=0.001; median PFS, 21 vs 11 months). Patients who had a PTEN score >20 (78.1%) showed longer PFS than did those with a PTEN score ⩽20 (P=0.006; median PFS, 13 vs 9 months). Patients who had a PTEN score >20 exhibited a longer overall survival (OS) than did those with a PTEN score ⩽20 (P=0.005; median OS, 48 vs 25 months). HER3 negativity and PTEN loss were identified as independent risk factors for PFS. PTEN loss was identified as an independent risk factor for OS.

Conclusion:

HER3 and PTEN expressions may be predictive markers, and PTEN expression may be a predictive and prognostic biomarker for trastuzumab treatment in HER2-positive MBCs.     

Genetic changes in the PTEN gene and their association with breast cancer in Pakistan

The PTEN gene, a candidate tumor suppressor, is one of the more commonly inactivated and extensively studied genes in cancer. However, few data are available about the role of germ line mutations of this gene in sporadic breast cancer cases. The purpose of this study was to determine extent of involvement of this gene in breast cancer in Pakistan. To test the hypothesis that genetic variations of PTEN play a role in the etiology of breast cancer, a population based case-control study was conducted in 350 breast cancer patients along 400 healthy controls. After extracting DNA from blood, the whole coding sequence of PTEN along with intron/exon boundaries was genotyped by polymerase chain reaction-single stranded conformational polymorphism. Sequencing analysis revealed nineteen different types of mutations in different regions of PTEN (in exon 2, 4, 5, 6, 7 and splicing sites of intron 2 and 4 and also in the 3' UTR region), including 3 silent, 8 missense, 2 frame shift and 6 splice site variations. Among the observed variations in this study, three missense mutations have already been reported i.e. 319G>A (Asp106Asn), 389G>A (Arg129Gln) and 482G>A (Arg160Lys) in different populations. The present results suggest that a wide range of germline PTEN mutations may play a role in the pathogenesis of breast cancer.     

PTEN Genetic and Epigenetic Alterations Define Distinct Subgroups in North Indian Breast Cancer Patients

Background: Breast cancer is a heterogeneous disease that can be subdivided on the basis of histopathologicalfeatures, genetic alterations, and gene-expression profiles. PTEN gene is considered an established tumor suppressor genein different types of cancer including breast cancer. However, the role of PTEN alterations in north Indian breast cancerhas not been explored especially in defining a group with distinct histological factors. Methodology: 181 sporadic breastcancer and their adjacent normal tissues were included in the present study. We analyzed methylation and LOH throughMS-PCR and microsatellite markers respectively. While, for PTEN protein expression, we used immunohistochemistry.All the molecular findings were correlated with the clinicopathological parameters of the patients to underline clinicalrelevance. Results: We found that LOH and methylation of the PTEN promoter were significantly associated withloss of PTEN protein expression, while, PTEN mutation was a rare event. Furthermore, out of 46 double hit cases (i.e.,having both methylation and LOH), 70% (32/46) cases showed complete loss of PTEN expression (P= 0.0249). BothLOH and PTEN promoter methylation were associated significantly with age and clinical stage, while, methylationand loss of PTEN expression were associated with high grade and Her-2 negativity. In addition, a quadruple (ER/PR/Her-2 and PTEN) negative group with distinct features was found. Conclusion: The pattern of PTEN expression andits correlation with the clinical parameters indicates that loss of PTEN expression defines a clinical group with distinctfeatures. Hence, PTEN expression provides differential therapeutic strategies for north Indian breast cancer.     

PTEN activity could be a predictive marker of trastuzumab efficacy in the treatment of ErbB2-overexpressing breast cancer

Trastuzumab is the only HER2/neu-directed therapy to have received Food and Drug Administration approval for the treatment of patients with metastatic breast cancer. The efficacy of trastuzumab depends on the HER2/neu status of the tumour and the patient's prior treatment, but even when patients are selected on the basis of HER2/neu gene amplification, the single-agent response rate ranges from 12 to 30% and few patients respond to trastuzumab monotherapy. Here, we propose PTEN as a predictive biomarker for trastuzumab efficacy. Human breast cancer SKBR3 and drug-resistant SKBR3/R cells were investigated. We also examined clinical samples from patients who had been treated with trastuzumab and analysed the relationship between trastuzumab efficacy and PTEN level. The PI3K/Akt signalling pathway was observed to be highly active in the drug-resistant cells, and their level of PTEN was low. Delivery of antisense PTEN duplex siRNA significantly decreased the trastuzumab chemosensitivity of parental SKBR3 cells, and marked activation of Akt signalling pathway was also recognised. Moreover, immunohistochemical investigation revealed that trastuzumab treatment was remarkably successful in cells with elevated PTEN expression. Along with the immune-system-associated cytotoxic mechanism, several mechanisms have been proposed for the effect of trastuzumab. PTEN activity might play an important and major role in its HER2/PI3K/Akt-mediated antitumour effect, and could be a useful biomarker for predicting the efficacy of trastuzumab in the treatment of breast cancer.     

Dysregulated PTEN-PKB and negative receptor status in human breast cancer

Recent studies demonstrate that abnormalities in PTEN may be one of the most frequent genetic events observed in human cancers. PTEN dysfunction leads to tumorigenesis through unopposed survival signals mediated via activated protein kinase B (PKB), which may also be associated with hormone-independence. We therefore investigated the relationship between PTEN-PKB and receptor status in human breast cancer. Several molecular variables, including immunohistochemical staining for PTEN, PKB (phosphorylated on ser473), p53 and p21 were evaluated. The p53 gene was sequenced from exons 2-11. Seventy-eight participants in a randomised breast cancer trial served as the cohort for our study. Twenty-eight of 77 (36%) patients' tumours demonstrated absent or reduced PTEN expression; 17 of 78 (22%) tumours over-expressed P-PKB. A significant inverse relationship was observed between reduced PTEN and increased P-PKB expression. Reduced PTEN also correlated with reduced ER or PR expression. None of the molecular variables correlated with survival. ER and PR negative tumours, however, experienced a significantly inferior disease-free survival than other ER/PR status tumours. Immunohistochemical analyses of ER expression in mammary carcinomas arising in PTEN heterozygous knockout mice did not demonstrate a reduction in ER immunoreactivity, in comparison to wild-type mice. Our data demonstrate that the PTEN-PKB pathway is abnormal in approximately 1/3 of lymph node negative breast cancer. Dysregulated PTEN-PKB was also associated with reduced ER/PR expression, but this does not appear to be a simple direct causal relationship. These observations support the contention that dysregulation in PTEN-PKB contributes to disease progression and hormone resistance of human breast cancer.     

PI3K/AKT信号通路相关蛋白在乳腺癌中的表达及其临床意义

目的：研究PI3K/AKT信号转导通路中PTEN、PI3K、AKT蛋白在乳腺癌中的表达及其与疾病发生发展、预后的关系。方法用免疫组化SP法检测45例乳腺癌患者病理组织（观察组）和其中15例患者癌旁正常组织（对照组）中PTEN、PI3K、AKT表达情况,采用单因素回归分析对PTEN、PI3K、AKT蛋白在乳腺癌组织中阳性表达的相关因素进行分析。结果 PI3K、AKT在乳腺癌中的表达率分别为73.3%、75.5%,高于癌旁正常乳腺组织的33.3%、40%,差异具有统计学意义（P﹤0.05）;PTEN在乳腺癌中表达率为22.2%,低于癌旁正常乳腺组织的53.3%,但差异无统计学意义（P﹥0.05）;单因素回归分析结果显示,患者发病年龄对PTEN、PI3K、AKT在乳腺癌组织中阳性表达无关（P﹥0.05）;组织学分级、临床分期、存在淋巴结转移是PTEN、PI3K、AKT在乳腺癌组织中的阳性表达的相关因素（P﹤0.05）。结论 PI3K/AKT信号通路可能参与了乳腺癌的发生与发展,PTEN蛋白表达缺失导致AKT、PI3K蛋白的过度表达,PI3K、PTEN、AKT蛋白表达的检测可能有助于预测乳腺癌的预后。     

Allelic loss of the PTEN region (10q23) in breast carcinomas of poor pathophenotype

Loss of heterozygosity (LOH) in loci of the 10q23 region that harbor the PTEN gene and mutations in the sequence of this gene have been found in several primary human tumors including breast carcinomas, suggesting that this gene could be implicated in their pathogenesis. We investigated allelic losses in microsatellites of the 10q23 region, and their correlations with nine pathologic parameters in 105 breast carcinomas. The LOH analysis was performcd by amplifying DNA by PCR, using five markers of the 10q23 region (D10S1687, D10S541, D10S2491, D10S583 and D10S571). LOH in at least one marker of the PTEN region was found in 29.5% of tumors. The statistical comparison between carcinomas with and without LOH in terms of the pathologic parameters showed significant differences in age (p=0.03), lymph node metastases (p=0.02), and higher histological grade (p=0.02); a trend toward significance was found for progesterone receptors (p=0.05). LOH in an individual marker and statistically significant relationships to tumor characteristics were observed at locus D10S541 for lymph node metastases (p=0.04), at D10S2491 (intragenic to the PTEN gene) for lymph node metastases (p=0.02), and at D10S583 for progesterone receptors (p=0.01) and for high grade (p=0.03). These results suggest the PTEN gene, or other genes of the 10q23 region, could be functionally related to breast cancer, probably influencing the development of histological features associated with poor prognosis.     

Mutation analysis of the putative tumor suppression gene PTEN/MMAC1 in sporadic breast cancer

PTEN/MMAC1, a potential human tumor suppressor gene, has been found to have inactivating mutations in several types of cancer, including breast cancer. The incidence of breast cancer in Chinese is quite low in comparison with Caucasians, and genetic factors may play some roles. To further determine the role of PTEN/MMAC1 in breast cancer in Chinese, we used loss of heterozygosity (LOH), single strand conformation polymorphism (SSCP) with direct sequencing of variant bands, and Southern blot analysis methods to analyze mutations in PTEN/MMAC1 in 52 cases of breast cancer. None had LOH at chromosome 10q23.3. One mutation was identified, a somatic 3base deletion, in one case. Our results suggest PTEN/MMAC1 does not play a major role in the development of sporadic breast cancer.     

乳腺癌细胞株MDA-MB-231获得性放疗抵抗机制探讨

目的探讨乳腺癌细胞株MDA-MB-231产生获得性放疗抵抗的可能机制。方法采用CCK8及流式细胞术检测产生乳腺癌细胞株MDA-MB-231获得放疗抵抗能力后细胞增殖及细胞周期的变化,采用蛋白质印迹法检测放疗抵抗后相关信号通路蛋白的变化,初步探讨乳腺癌细胞产生放疗抵抗的可能机制。结果 CCK8法检测结果显示,第1天实验组吸光度值为0.305 7±0.013 1,明显高于对照组的0.277 8±0.011 8,差异无统计学意义,F=7.571,P=0.051;第2天实验组为0.401 7±0.048 0,明显高于对照组的0.289 0±0.020 9,差异有统计学意义,F=13.907,P=0.020;第4天实验组为0.635 7±0.026 1,明显高于对照组的0.434 2±0.080 6,差异有统计学意义,F=16.994,P=0.015;第6天实验组为1.5347±0.0391,显著高于对照组的1.075 7±0.036 8,差异有统计学意义,F=218.953,P〈0.001。提示231/RR10细胞株在获得放疗抵抗能力的同时,增殖能力也增强,差异有统计学意义,P〈0.05。流式细胞术检测结果显示,放疗抵抗细胞株中,G0-G1及S期的细胞比例减少,但差异无统计学意义,P值分别为0.083和0.165;G2-M期的细胞比例明显增加,差异有统计学意义,P值分别为0.002和〈0.01。蛋白质印迹法检测结果显示,抑癌基因PTEN的表达明显减少,表皮生长因子的活化状态pEGFR的表达明显增加,AKT蛋白的表达水平无变化,而AKT磷酸化蛋白的表达明显增加。结论乳腺癌细胞株MDA-MB-231中EGFR/AKT信号通路激活,促进细胞生长和生存,从而导致放疗抵抗的产生。这一信号通路可能由抑癌基因PTEN负性调控。