上海地区妇女乳腺癌组织PIK3CA基因热点突变区域研究

目的:探讨乳腺癌组织中磷脂酰肌醇一3-激酶催化亚单位α(PIK3CA)基因2个热点突变区域第9和第20外显子的突变,以及该突变与乳腺癌临床病理特征之间的关系.方法:45例乳腺癌标本提取DNA后.对第9及第20外显子进行PCR扩增,产物纯化后测序.另取10例乳腺良性肿瘤组织标本作为对照.结果:在45例乳腺癌组织标本中共发现14例(31%)PIK3CA基因突变,其中第9外显子8例(57%),第20外显子6例(43%),在第9外显子突变中,1例为C1616G(P539R),1例为G1633A(E545K),6例为A1634C(E545A).第20外显子的6例突变均为A3140G(H1047R).10例良性肿瘤对照中均未发现突变.第9与第20外显子突变在浸润性导管癌和浸润性小叶癌中的分布差异无统计学意叉,P>0.05.PIK3CA基因突变与患者年龄、肿瘤大小、淋巴结状态、ER/PR状态、HER-2表达和p53表达之间无明显相关性,P>0.05.结论:PIK3CA基因可能与乳腺癌的发生、发展及预后相关.但PIK3CA基因突变与乳腺癌临床病理特征之间无明显相关性.     

乳腺癌PIK3CA基因热点突变的研究

目的:采用突变敏感性分子开关技术,检测乳腺癌组织中PIK3CA基因热点突变的突变频率,并分析乳腺癌PIK3CA基因热点突变与乳腺癌临床病理特征之间的关系.方法:用突变敏感性分子开关技术对90例乳腺癌组织和10例乳腺纤维腺瘤组织DNA进行检测,并利用基因测序进一步验证.结果:在90例乳腺癌患者中检测出18例PIK3CA基因热点突变(突变率20％,18/90),包含A3140G突变14例(突变率15.6％,14/90)、G1633A突变3例(突变率3.3％,3/90)、GI624A突变2例(突变率2.2％,2/90),其中1例患者同时发生A3140G和G1624A突变.10例乳腺纤维腺瘤中未发现以上热点突变.PIK3CA基因突变与HER-2表达有关(x2=4.119,P=0.048),过表达者中PIK3CA基因突变率低,而与年龄分布(x2 =0.238,P=0.602)、肿瘤大小(P=1.000)、淋巴结状态(x2=3.689,P＝0.056)及ER(x2=0.957,P=0.328)、PR(x2 =0.012,P=0.914)和EGFR(x2 =0.011,P=0.916)是否表达无相关性.结论:PIK3CA基因热点突变与患者的HER-2过表达呈负相关.     

A novel PIK3CA hotspot mutation in Isfahanian breast cancer patients

Somatic mutations of phosphatidylinositol 3-kinase (PI3K) catalytic subunit (PIK3CA) play an important role in tumorigenesis. Using PCR-SSCP, followed by sequencing, we examined the PIK3CA gene over the previously identified mutational hotspots in a panel of 50 breast cancer and 5 normal breast tissue, as well as 50 normal blood samples isolated from a population of Iranian patients. In the present study, the frequency of PIK3CA mutation was 14%. However, the previously identified hotspot mutations in exons 20 were completely absent in these breast cancer samples. Instead, we found a new hotspot mutation (3 of 50 samples) in exon 20.     

Mutational profiling reveals PIK3CA mutations in gallbladder carcinoma

Background  

The genetics of advanced biliary tract cancers (BTC), which encompass intra- and extra-hepatic cholangiocarcinomas as well as gallbladder carcinomas, are heterogeneous and remain to be fully defined.     

PIK3CA基因突变与乳腺癌的关系

近年来女性乳腺癌的发病率明显上升,并趋于年轻化,尽管手术治疗和术后多种辅助治疗对患者的预后有明显的改善,但仍有较高的复发率和死亡率[1]。肿瘤的发生是多因素、多阶段、多步骤、多基因改变的结果,包括原癌基因的激活和抑癌基因的失活。     

中国人群结直肠癌中PIK3CA基因突变分析

目的:PIK3CA基因编码ⅠA型磷脂酰肌醇-3-激酶(PI3Ks)的p110催化亚基,致癌性的PIK3CA突变可通过激活P13K通路参与结直肠癌的发生发展。PIK3CA在西方结直肠癌患者中有较高的突变频率,但其在中国人结直肠癌中的突变情况尚不明确。本研究旨在探讨中国人结直肠癌中PIK3CA基因的突变频率、分布特点及其与结直肠癌的关系。方法:采用PCR产物直接测序法,对79例中国结直肠癌患者肿瘤标本中PIK3CA基因外显子9和外显子20中的突变进行检测分析。结果:在79例肿瘤标本中检出PIK3CA基因突变率为8.9%(7/79),其中外显子9突变率为6.3%(5/79),外显子20突变率为2.5%(2/79),其突变热点分布与既往文献报道基本相符。结论:中国人结直肠癌中存在一个PIK3CA基因突变的亚群,其E542K、E545K和H1047R突变,与以往报道的该基因的致癌性突变相一致,可能是这部分结直肠癌中PI3K信号通路激活的原因。     

Mutation of the PIK3CA gene in ovarian and breast cancer

Phosphatidylinositol 3'-kinases are lipid kinases with important roles in neoplasia. Recently, a very high frequency of somatic mutations in PIK3CA has been reported among a large series of colorectal cancers. However, the relevance of PIK3CA mutation in other cancer types remains unclear because of the limited number of tumors investigated. We have screened a total of 284 primary human tumors for mutations in all coding exons of PIK3CA using a combination of single stranded conformational polymorphism and denaturing high-performance liquid chromatography analysis. Among 70 primary breast cancers, 40% (28 of 70) harbored mutations in PIK3CA, making it the most common mutation described to date in this cancer type. Mutations were not associated with histologic subtype, estrogen receptor status, grade or presence of tumor in lymph nodes. Among the primary epithelial ovarian cancers only 11 of 167 (6.6%) contain somatic mutations, but there was a clear histologic subtype bias in their distribution. Only 2 of 88 (2.3%) of serous carcinomas had PIK3CA mutations compared with 8 of 40 (20.0%) endometrioid and clear cell cancers, which was highly significant (P = 0.001). In contrast, PIK3CA gene amplification (>7-fold) was common among all histologic subtypes (24.5%) and was inversely associated with the presence of mutations. Overall, PIK3CA mutation or gene amplification was detected in 30.5% of all ovarian cancers and 45% of the endometrioid and clear cell subtypes. Our study is the first direct evidence that PIK3CA is an oncogene in ovarian cancer and greatly extends recent findings in breast cancer.     

Absence of PIK3CA hotspot mutations in hepatocellular carcinoma in Japanese patients

A recent study revealed that the p110alpha (PIK3CA), catalytic subunit of phosphatidylinositol 3-kinase (PI3K), is somatically mutated in many types of cancer. For example, PIK3CA is mutated in an estimated 35.6% of hepatocellular carcinoma (HCC) cases. To measure the frequency of PIK3CA hotspot mutations in Japanese HCC patients, exons 9 and 20 of the PIK3CA gene were sequenced in 47 clinical HCC samples. Contrary to expectations, no hotspot mutations were found any of the HCC samples. In addition, we found abnormally migrating waves near the end of exon 9 in the PCR chromatograms from 13 of the 47 samples. PCR amplification and subsequent cloning and sequencing revealed that these chromatograms contained two distinct sequences, the wild-type p110alpha sequence and a different sequence found on human chromosome 22q11.2, the Cat Eye Syndrome region, which contains a putative pseudogene of PIK3CA. These abnormally migrating waves were also found in noncancerous liver tissue, indicating that this was not a result of HCC-associated mutations. Therefore, it is likely that the percentage of hotspot mutations in the PIK3CA gene of Japanese HCC patients is lower than was previously reported.     

PIK3CA expression in invasive breast cancer: a biomarker of poor prognosis

The implications of Phosphatidylinositol 3-kinase (PIK3CA) mutations and its aberrant protein expression in breast cancer (BC) different molecular subtypes and patients’ outcome remain controversial. The aims of this study were to assess the prevalence and clinical significance of PIK3CA protein expression in BC and to determine its association with its different molecular classes. PIK3CA protein expression was assessed in a well-characterized series of early stage BC (n = 1,394) with long-term follow-up, using tissue microarrays and immunohistochemistry. Associations between PIK3CA expression and clinicopathological variables, molecular classes, and patients’ outcome were investigated. Positive PIK3CA expression was associated with poor prognostic variables including higher grade, larger size, nodal involvement, vascular invasion, and higher proliferative fraction (P < 0.001). Increased PIK3CA expression was associated with the basal-like breast cancer (BLBC) and HER2-positive classes as well as triple negative non-basal (TNnon-B) tumors (P < 0.001). The luminal class showed reduced PIK3CA expression relative to other classes. Patients with PIK3CA positive tumors had shorter BC specific and disease free survival, independent of other prognostic factors except grade. Similar associations with outcome were found when the analysis was restricted to the large luminal class of tumors. PIK3CA is an oncogenic biomarker associated with poor prognosis in BC. Although, PIK3CA over-expression was more prevalent in BLBC and HER2-positive tumors it appeared to be a marker of poor differentiation rather than of a particular subtype. Thus, targeting of PIK3CA using specific inhibitors could potentially be beneficial, particularly for patients with more aggressive poorly differentiated tumors, irrespective of their molecular subtype.     

Mutation distributions and clinical correlations of PIK3CA gene mutations in breast cancer

Breast cancer (BCa) is the most common cancer and the second cause of death among women. Phosphoinositide 3-kinase (PI3K) signaling pathway has a crucial role in the cellular processes such as cell survival, growth, division, and motility. Moreover, oncogenic mutations in the PI3K pathway generally involve the activation phosphatidylinositol-4,5-bisphosphate 3-kinase-catalytic subunit alpha (PIK3CA) mutation which has been identified in numerous BCa subtypes. In this review, correlations between PIK3CA mutations and their clinicopathological parameters on BCa will be described. It is reported that PIK3CA mutations which have been localized mostly on exon 9 and 20 hot spots are detected 25–40 % in BCa. This relatively high frequency can offer an advantage for choosing the best treatment options for BCa. PIK3CA mutations may be used as biomarkers and have been major focus of drug development in cancer with the first clinical trials of PI3K pathway inhibitors currently in progress. Screening of PIK3CA gene mutations might be useful genetic tests for targeted therapeutics or diagnosis. Increasing data about PIK3CA mutations and its clinical correlations with BCa will help to introduce new clinical applications in the near future.     

Somatic mutation and gain of copy number of PIK3CA in human breast cancer

Introduction

Phosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases that regulate signaling pathways involved in cell proliferation, adhesion, survival, and motility. Even though PIK3CA amplification and somatic mutation have been reported previously in various kinds of human cancers, the genetic change in PIK3CA in human breast cancer has not been clearly identified.

Methods

Fifteen breast cancer cell lines and 92 primary breast tumors (33 with matched normal tissue) were used to check somatic mutation and gene copy number of PIK3CA. For the somatic mutation study, we specifically checked exons 1, 9, and 20, which have been reported to be hot spots in colon cancer. For the analysis of the gene copy number, we used quantitative real-time PCR and fluorescence in situ hybridization. We also treated several breast cancer cells with the PIK3CA inhibitor LY294002 and compared the apoptosis status in cells with and without PIK3CA mutation.

Results

We identified a 20.6% (19 of 92) and 33.3% (5 of 15) PIK3CA somatic mutation frequency in primary breast tumors and cell lines, respectively. We also found that 8.7% (8 of 92) of the tumors harbored a gain of PIK3CA gene copy number. Only four cases in this study contained both an increase in the gene copy number and a somatic mutation. In addition, mutation of PIK3CA correlated with the status of Akt phosphorylation in some breast cancer cells and inhibition of PIK3CA-induced increased apoptosis in breast cancer cells with PIK3CA mutation.

Conclusion

Somatic mutation rather than a gain of gene copy number of PIK3CA is the frequent genetic alteration that contributes to human breast cancer progression. The frequent and clustered mutations within PIK3CA make it an attractive molecular marker for early detection and a promising therapeutic target in breast cancer.     

PIK3CA as an oncogene in cervical cancer

Amplification of chromosome arm 3q is the most consistent aberration in cervical cancer, and is implicated in the progression of dysplastic uterine cervical cells into invasive cancer. The present study employed the 'positional candidate gene' strategy to determine the contribution of PIK3CA, which is located in 3q26.3, in cervical tumorigenesis. PIK3CA is known to be involved in the PI 3-kinase/AKT signaling pathway, which plays an important role in regulating cell growth and apoptosis. The results of comparative genomic hybridization show that the 3q26.3 amplification was the most consistent chromosomal aberration in primary tissues of cervical carcinoma, and a positive correlation between an increased copy number of PIK3CA (detected by competitive PCR) and 3q26.3 amplification was found in tumor tissues and in cervical cancer cell lines. In cervical cancer cell lines harboring amplified PIK3CA, the expression of gene product (p110alpha) of PIK3CA was increased, and was subsequently associated with high kinase activity. In addition, transformation phenotypes in these lines, including increased cell growth and decreased apoptosis, were found to be significantly affected by the treatment of specific PI 3-kinase inhibitor, suggesting that increased expression of PIK3CA in cervical cancer may result in promoting cell proliferation and reducing apoptosis. These evidences support that PIK3CA is an oncogene in cervical cancer and PIK3CA amplification may be linked to cervical tumorigenesis. Oncogene (2000).     

鼻咽癌组织中PIK3GA基因热点突变区的突变筛查

背景与目的:近期研究发现磷脂酰肌醇激酶-3催化亚单位α基因(phosphatidylinositol 3-kinase catalytic alpha polypeptide gene,PIK3CA)在多种肿瘤中存在高频的体细胞突变,并且突变常发生在PIK3CA的第9外显子和20外显子两个热点突变区.对这两个热点突变的研究表明,这些突变能增强该酶的活性、有助于肿瘤细胞的侵袭、对抗凋亡等.因此提示PIK3CA基因是与多种肿瘤发生、发展相关的癌基因.本研究旨在检测鼻咽癌组织中PIK3CA两个热点突变区的突变,以及该基因的变异与鼻咽癌发病的关系.方法:在鼻咽癌组织及患者外周血中筛查PIK3CA的突变热点区第9外显子和第20外显子.对46例散发性鼻咽癌组织标本采用PCR产物克隆测序,对与之匹配的46例鼻咽癌患者外周血标本和3个鼻咽癌细胞系(CNE1,CNE2,SUNE1),则将PCR产物直接测序.结果:在46例鼻咽癌组织标本中在PIK3CA热点突变区第9号外显子检出2例突变(4.3%):1例为T1563G(521Asn→Lys);另1例为A1646G(549Asp→Gly).在46例鼻咽癌标本第9外显子中18例检出A1634C-G1658C-del 1659T"复合突变",进一步研究表明该"复合突变"可能为22号染色体上同源区域的序列.在对PIK3CA另外一个突变热点区第20外显子的检测中,46例鼻咽癌组织标本中都没检测到突变.另外,在3个鼻咽癌细胞系和46例鼻咽癌匹配外周血DNA标本用PCR-直接测序法均未检测到第9外显子和第20外显子突变.结论:PIK3CA基因第9外显子与第20外显子鼻咽癌中较少发生突变;克隆测序检测体细胞突变具有更高的敏感性,通过该方法在第9外显子发现的"复合突变"可能是22q11.2的Cat Eye Syndrome region高度同源区域的序列而非PIK3CA基因座的变异.     

Mutation analysis of PIK3CA and PIK3CB in esophageal cancer and Barrett's esophagus

Mutation of PIK3CA, the gene coding for the p110alpha catalytic subunit of phosphoinositide 3-kinase (PI3K), has been reported in a limited range of human tumors. We now report that PIK3CA is also mutated in esophageal tumors. Single-strand conformational polymorphism (SSCP) and denaturing high-performance liquid chromatography (DHPLC) were used to screen all 20 exons of PIK3CA in 101 samples from 95 individuals with esophageal cancer and/or Barrett's esophagus. Somatic mutation of PIK3CA was detected in 4 of 35 (11.8%) of esophageal squamous cell carcinomas (SCC) and 3 of 50 (6%) adenocarcinomas. No mutations were detected in any of 17 samples of Barrett's esophagus. For PIK3CB, we screened exons 11 and 22, which code for the regions corresponding to the exon 9 and 20 mutational 'hotspots' of PIK3CA. No somatic changes were detected in PIK3CB This study extends previous observations in other tumor types by demonstrating the presence of somatic PIK3CA mutations in both SCC and adenocarcinoma of the esophagus, thus implicating the PI3K pathway in the initiation and/or progression of esophageal cancers.     

Spectrum of PIK3CA/AKT mutations across molecular subtypes of triple-negative breast cancer

Breast Cancer Research and Treatment - The heterogeneity of triple-negative breast cancer (TNBC) confers variable response to chemotherapy that results in poor outcome and relapse. Due to lack of...     

PIK3CA基因突变与乳腺癌的关系

PIK3CA基因在细胞生长、凋亡及肿瘤的形成过程中起重要的作用.功能及遗传学研究显示,PIK3CA基因是一个癌基因.近期研究显示在多种人类实体瘤中存在PIK3CA基因的突变.乳腺癌中PIK3CA基因突变的频率约为8%～40%.其突变80%～90%聚集在该基因的第9外显子和第20外显子.研究表明,PIK3CA基因突变与乳腺癌生物学特性及临床预后等有关.