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。     

K-ras、PIK3CA基因突变与结直肠癌患者临床特征的关系及相关性分析

目的探讨K-ras、PIK3CA基因突变与结直肠癌患者临床特征的关系,分析K-ras、PIK3CA基因表达的相关性。方法选取110例结直肠癌患者,均接受了K-ras、PIK3CA基因突变检测。分析结直肠癌患者的K-ras、PIK3CA基因突变情况,并比较不同临床特征的结直肠癌患者K-ras、PIK3CA基因的突变率,分析K-ras、PIK3CA基因表达的相关性。结果结直肠癌患者K-ras基因突变率为37.27%,PIK3CA基因突变率为18.18%;肿瘤直径≥5cm、直肠癌和Ⅲ~Ⅳ期患者K-ras基因突变率分别明显高于肿瘤直径﹤5cm、结肠癌和Ⅰ~Ⅱ期的患者(P﹤0.01);Ⅲ~Ⅳ期患者的PIK3CA基因突变率明显高于Ⅰ~Ⅱ期的患者(P﹤0.01);K-ras基因与PIK3CA基因表达呈正相关(r=0.514,P﹤0.01)。结论K-ras、PIK3CA基因突变与结直肠癌患者的临床特征有关,K-ras、PIK3CA基因表达有一定的相关性。     

PIK3CA基因与结直肠癌发生发展的研究

 PIK3CA基因编码蛋白激酶PI3K的p100α亚单位,参与PI3K的合成,通过下游PI3K/AKT通路发挥其生物学效应。多种肿瘤组织中可检测到PIK3CA基因突变,突变的PIK3CA异常激活PI3K-AKT信号通路,导致细胞周期异常、细胞黏附性下降、细胞凋亡下调及新生血管形成等,促进肿瘤发生发展。研究表明PIK3CA与结直肠癌的发生、发展、分化、转移及耐药密切相关,有望在结直肠癌的早期诊断、基因筛查、治疗方案制定、复发随访等方面提供一定的临床证据。     

高通量测序分析PIK3CA突变型与野生型结直肠癌的肠道菌群特征

  目的  采用16S rDNA二代高通量测序技术,研究PIK3CA突变型与野生型结直肠癌患者中的肠道菌群特征。  方法  选取2016年12月至2017年12月华中科技大学同济医学院附属协和医院结直肠癌患者19例,采用 16S rDNA高通量测序技术分析PIK3CA突变型（n=4）和PIK3CA野生型（n=15）之间肿瘤组织中微生物多样性和组成差异。  结果  在门水平上,结直肠癌患者的肠道菌群主要由变形菌门、栖热菌门、放线菌门、厚壁菌门和拟杆菌门组成,占总群落的98%以上。Alpha多样性分析显示,PIK3CA突变型与野生型结直肠癌患者之间微生物多样性有显著性差异,且PIK3CA突变型患者中微生物多样性明显高于野生型。Beta多样性分析显示PIK3CA突变型与野生型结直肠癌患者的肿瘤微生物特征有显著性差异。Spearman关联网络分析结果显示,在PIK3CA野生型结直肠癌肿瘤组织中,双歧杆菌属与假单胞菌呈正相关。  结论  PIK3CA突变型与野生型结直肠癌患者肿瘤组织中的微生物群落结构有显著性差异,且PIK3CA突变患者中的肠道微生物多样性更丰富。      

结直肠癌Ras、BRAF和PIK3CA基因突变分析及与临床病理特征的关系

目的 分析结直肠癌患者中Ras（K-Ras／N-Ras）、BRAF和PIK3CA基因突变情况及其与临床病理特征的关系。方法 回顾性分析2013年12月至2014年10月于北京大学肿瘤医院消化肿瘤内科接受诊治的200例结直肠癌患者的肿瘤组织标本,采用PCR扩增-直接测序法检测Ras,包括K-Ras（第2、3、4外显子）、N-Ras（第2、3、4外显子）、BRAF（第15外显子）及PIK3CA（第9、20外显子）基因的突变状态,分析其与结直肠癌临床病理特征的关系。结果 200例患者中存在Ras基因突变92例（46.0％）,其中K-Ras基因突变87例（43.5％）,主要发生在外显子2,N-Ras基因突变5例（2.5％）;其中1例患者存在K-Ras、N-Ras基因同时突变。存在BRAF基因突变15例（7.5％）,突变类型均为V600E,且与K-Ras突变存在排他性。存在PIK3CA基因突变9例（4.5％）,可与Ras或BRAF基因突变共存。Ras（K-Ras／N-Ras）基因在年龄≥65岁患者中的突变率明显高于＜65岁者（P＜0.05）,其表达与性别、原发部位、组织学类型、分化程度、TNM分期、区域淋巴结转移、远处转移、术后复发转移均无关（P均＞0.05）。BRAF、PIK3CA基因在原发部位为右半结肠患者中的突变率明显升高（P＜0.05）,但与年龄、性别、组织学类型、分化程度、TNM分期、区域淋巴结转移、远处转移、术后复发转移均无关（P＞0.05）。结论 N-Ras、PIK3CA基因在中国结直肠癌患者中的突变率较低。K-Ras、N-Ras基因突变与年龄相关,BRAF、PIK3CA基因与肿瘤原发部位相关;对结直肠癌患者进行Ras（K-Ras／N-Ras）、BRAF及PIK3CA基因的联合检测将会为提高临床靶向治疗的疗效提供更加可靠的依据。     

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.     

云南地区结直肠癌患者RAS/BRAF/PIK3CA基因突变状态及与临床病理特征的关系

目的:本研究主要对结直肠癌患者的KRAS/NRAS/BRAF V600E/PIK3CA基因突变情况及与临床病理特征的关系进行探究。方法:我们对2018年01月至2020年01月在我院分子诊断中心进行基因检测的结直肠癌患者的KRAS/NRAS/BRAF V600E/PIK3CA突变情况进行回顾性分析,共纳入209例具有完整临床信息的患者,所有患者的基因检测都是采用高通量测序方法获得的,并对患者的人口统计学和临床信息进行分析。结果:209例结直肠癌患者中,KRAS、NRAS、BRAF V600E、PIK3CA突变例数分别为98例、7例、10例和25例,突变率分别为46.9%、3.3%、4.8%和12.0%。KRAS 2号外显子突变最常见,其中又以G12D亚型突变高发,肿瘤原发部位在直肠的患者和微卫星稳定的CRC患者KRAS突变率明显高于原发部位在左右半结肠和微卫星不稳定的患者(P<0.05);BRAF V600E在MSI-H的CRC患者中突变率显著高于MSS的患者(P<0.05);男性患者、既往没有吸烟史、有淋巴结转移、临床分期较早以及MSI-H的CRC患者有更高的PIK3CA...     

消化道恶性肿瘤高通量基因测序的生物统计分析

目的:观察TP53、KRAS、KDR、APC、MLH1及PIK3CA等56个基因在消化道恶性肿瘤中的突变情况,探讨驱动基因的诊疗意义。方法:选择胃食管癌15例、结直肠癌21例患者组织石蜡标本,运用高通量基因测序技术检测56个肿瘤突变高频基因,并进行生物统计分析。结果:36例标本检出34例有已知基因突变,突变基因为TP53、KRAS、MLH1、PIK3CA、KDR、APC、SMARCB1、KIT、EGFR、NRAS、STK11、SMO、SMAD4、CDH1、ERBB2、JAK2和RET共17种。其突变率由高到低依次为:TP53（75.00%）,KRAS（33.33%）,MLH1、PIK3CA、KDR（均为13.89%）,APC（11.76%）,SMARCB1（8.82%）,KIT、EGFR及NRAS（均为2.78%）。KRAS在结直肠癌中的突变率（47.62%）显著高于在胃食管癌中的突变率（13.33%）。TP53的突变率明显高于其他突变基因。在结直肠癌中KRAS的突变率显著高于KDR、APC、MLH1,未发现有统计学关联。结论:消化道恶性肿瘤TP53突变率较高,可能与病理组织分化程度低及淋巴结转移有关。KRAS在结直肠癌中较在胃食管癌中更易发生突变,存在部位差异。同时KRAS与KDR、APC、MLH1,在结直肠癌患者中存在共突变现象,提示结直肠癌的酪氨酸激酶通路和血管内皮生长因子受体基因在致癌过程中可能存在协同作用,导致肿瘤在结直肠中更易发生发展,选择靶向药物治疗时需考虑协同作用,以便科学精准用药。     

大肠癌组织PIK3CA蛋白表达及其与大肠癌耐药相关性的研究

目的:观察PIK3CA蛋白在大肠癌的表达情况,并探讨其表达与大肠癌多药耐药(MDR)基因产物LRP、GST-π、Topo Ⅱ的相关性及临床意义.方法:应用免疫组织化学Max VisionTM法检测108例大肠癌组织中PIK3CA及多药耐药(MDR)基因产物LRP、GST-π、Topo Ⅱ的表达情况,并分析PIK3CA与大肠癌多药耐药的相关性.结果:1)PIK3CA蛋白的表达与大肠癌的分化、淋巴结转移及TNM分期有明显的相关性,P<0.05;2)PIK3CA蛋白的表达与GST-π、TopoⅡ具有相关性.结论:PIK3CA蛋白的表达与肿瘤的多药耐药具有相关性,检测PIK3CA蛋白对于大肠癌患者选择有效的化疗方法及判断预后具有重要的意义.     

肠道菌群失衡和结直肠癌关系的研究进展

结直肠癌是最常见的恶性肿瘤之一,发病率逐年上升.研究表明肠道菌群失衡在结直肠癌的发生中可能发挥重要作用,肠道菌群可能通过肠道黏膜屏障受损、慢性炎症反应、细菌酶和毒性代谢产物作用等多种机制促进肿瘤的发生.近年来通过无菌动物实验、基因敲除动物实验以及新一代的高通量测序使人们对肠道菌群和大肠癌间关系的认识不断深化,继而从不同角度提出肠道菌群失衡导致结直肠癌发病的作用模式,本文将结合相关作用模式从肠道菌群先后影响结直肠癌不同发病阶段的角度阐述结直肠癌发生、发展过程中的相关机制,为进一步认识结直肠癌的发病机制和结直肠癌的早期诊疗提供新的思路.     

Role of PIK3CA gene in colorectal cancer genesis and development

The PIK3CA gene codes p100α, the catalytic subunit of phosphatidylinositol 3-kinase (PI3K) and is involved in the initiating the PI3K/AKT pathway. PIK3CA plays its biological roles through.downstream PI3K pathway. PIK3CA gene mutants can be detected in many kinds of tumors. The mutant PIK3CA gene can abnormally activate PI3K pathway, leading to the abnormal cell cycle, decreased cell adhesion, down regulated apoptosis and neovascularization, and then promotes tumor genesis and development. Recent researches have found that mutant PIK3CA gene is closely correlated with the genesis, development, differentiation, metastasis and drug resistance of colorectal cancer. Research of PIK3CA in colorectal cancer may provide significant evidence for the early diagnosis, gene screen, therapeutic regimen making, recurrence and follow up.     

Mutations of the PIK3CA gene in hereditary colorectal cancers

Somatic mutations of the PIK3CA gene have recently been detected in various human cancers, including sporadic colorectal cancer. However, mutations of the PIK3CA gene in hereditary colorectal cancers have not been clarified. To elucidate the mutation status in familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC), which are the most common hereditary colorectal cancers, we investigated PIK3CA mutations in 163 colorectal tumors, including adenomas, intramucosal carcinomas and invasive carcinomas. For comparison, we also analyzed mutations of the same gene in 160 sporadic colorectal tumors at various histopathological stages. Analysis at exons 1, 7, 9 and 20 of the PIK3CA gene revealed somatic mutations in 21% (8 of 39) of FAP invasive carcinomas, 21% (7 of 34) of HNPCC invasive carcinomas, 15% (8 of 52) of sporadic invasive carcinomas, and 14% (7 of 50) of sporadic colorectal metastases in the liver. Mutations in FAP and HNPCC carcinomas predominantly occurred in the kinase domain (exon 20), while the majority of mutations in sporadic cases occurred in the helical domain (exon 9). Adenomas and intramucosal carcinomas from all patients exhibited no mutations (0 of 148). Our data suggest that PIK3CA mutations contribute to the invasion step from intramucosal carcinoma to invasive carcinoma in colorectal carcinogenesis in FAP and HNPCC patients at a similar extent to that seen in sporadic patients.     

PIK3CA mutation is predictive of poor survival in patients with colorectal cancer

The PI3K-AKT pathway is activated in a variety of human cancers, resulting in disturbance of cell growth, proliferation and survival. Among the factors affecting the pathway, the K-Ras mutation and PIK3CA mutation are the most common oncogenic alterations in colorectal cancer. We hypothesized that these two mutations are important in activation of the PI3K pathway and colorectal carcinogenesis. In this study, we aimed to examine the influence of PIK3CA mutation and K-Ras mutation on AKT activation, and to clarify whether PIK3CA mutation, K-Ras mutation and p-AKT expression may be used as parameters for predicting prognosis in colorectal cancer. Tissue samples from 158 colorectal cancer patients who underwent surgical resection were examined. The sequences of exon 1 of K-Ras and exons 9 and 20 of PIK3CA were determined by direct sequencing using genomic DNA extracted from paraffin-embedded blocks. Activation status of AKT was evaluated by immunohistochemical staining using phospho-specific AKT antibody (Ser473). Correlation between these factors and clinicopathologic findings/patient survival were examined. As a result, PIK3CA mutation was significantly associated with shorter relapse-free survival (RFS) in stage II/III patients (p = 0.0216) and shorter disease-specific survival in all patients (p = 0.0357). In the multivariate analysis, PIK3CA mutation was the only independent and significant prognostic factor for RFS in stage II/III patients (p = 0.0433, HR 2.478). This study revealed the prognostic value of PIK3CA mutation in colorectal cancer patients. Patients with PIK3CA mutation should be followed up carefully. Moreover, our result suggests that inhibition of PIK3CA mutant may be a new molecular target therapy.     

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.     

The favorable impact of PIK3CA mutations on survival: an analysis of 2587 patients with breast cancer

The phosphatidylinositol-3 kinase(PI3K) pathway regulates a number of cellular processes, including cell survival, cell growth, and cell cycle progression. Consequently, this pathway is commonly deregulated in cancer. In particular, mutations in the gene PIK3CA that encodes the p110α catalytic subunit of the PI3K enzymes result in cell proliferation and resistance to apoptosis in vitro and induce breast tumors in transgenic mice. These data underscore the role of this pathway during oncogenesis. Thus, an ongoing, large-scale effort is underway to develop clinically active drugs that target elements of the PI3K pathway. However, conflicting data suggest that gain-of-function PIK3CA mutations may be associated with either a favorable or a poor clinical outcome, compared with the wild-type PIK3CA gene. In the current study, we performed a systematic review of breast cancer clinical studies. Upon evaluation of 2587 breast cancer cases from 12 independent studies, we showed that patients with tumors harboring a PIK3CA mutation have a better clinical outcome than those with a wild-type PIK3CA gene. Importantly, this improved prognosis may pertain only to patients with mutations in the kinase domain of p110α and to postmenopausal women with estrogen receptor-positive breast cancer. We propose three potential explanations for this paradoxical observation. First, PIK3CA mutations may interfere with the metastasis process or may induce senescence, which results in a better outcome for patients with mutated tumors. Secondly, we speculate that PIK3CA mutations may increase early tumor diagnosis by modification of the actin cytoskeleton in tumor cells. Lastly, we propose that PIK3CA mutations may be a favorable predictive factor for response to hormonal therapy, giving a therapeutic advantage to these patients. Ultimately, an improved understanding of the clinical impact of PIK3CA mutations is critical for the development of optimally personalized therapeutics against breast cancer and other solid tumors. This effort will be important to prevent or explain therapeutic failures and select patients who are most likely to respond to new therapies that inhibit the PI3K pathway.     

Novel mutant-enriched sequencing identified high frequency of PIK3CA mutations in pharyngeal cancer

We previously reported 4 PIK3CA mutations in 38 head and neck cancer samples, 3 of which were identified in 6 pharyngeal cancer samples. To determine the mutation frequency of PIK3CA in pharyngeal cancer, we studied 24 additional cases of pharyngeal squamous cell carcinoma in this study. Using both direct genomic DNA sequencing and novel mutant-enriched sequencing methods developed specifically for the 3 hot-spot mutations (H1047R, E545K and E452K) of PIK3CA, we detected 5 mutations of PIK3CA in the 24 pharyngeal cancers (20.8%). Three of the 5 mutations had been missed by the conventional sequencing method and were subsequently detected by novel mutant-enriched sequencing methods. We showed that the mutant-enriched sequencing method for the H1047R hot-spot mutation can identify the mutation in a mixed population of mutant and wild-type DNA sequences at 1:360 ratios. These novel mutant-enriched sequencing methods allow the detection of the PIK3CA hot-spot mutations in clinical specimens which often contain limited tumor tissues (i.e., biopsy specimens). The data further support that oncogenic PIK3CA may play a critical role in pharyngeal carcinogenesis, and the mutant-enriched sequencing methods for PIK3CA are sensitive and reliable ways to detect PIK3CA mutations in clinical samples. Because PIK3CA and its pathway are potential targets for chemotherapy and radiation therapy, and frequent somatic mutation of PIK3CA has been identified in many human cancer types (e.g., breast cancer, colorectal cancer), the abilities to detect PIK3CA mutations with enhanced sensitivities have great potential impacts on target therapies for many cancer types.     

Clinicopathological analysis of colorectal cancers with PIK3CA mutations in Middle Eastern population

Activation of the phosphatidylinositol 3'-kinase (PI3K)/AKT pathway results in an increase in cell proliferation and survival. Somatic mutations within the PI3K catalytic subunit, PIK3CA are common cause of increasing PI3K activity and are believed to be oncogenic in many cancer types. Few reports addressed the association between PIK3CA mutations and tumor progression specifically in microsatellite instable (MSI) colorectal cancer (CRC). In the present study, we have evaluated PIK3CA mutational status in a series of 410 Middle Eastern CRC and 13 colon cell lines to study the prevalence of PIK3CA mutations in MSI cases, PTEN expression in CRC and possibility of therapeutic targeting of this set of patients. PIK3CA mutations were found in four of the cell lines tested and 51 colorectal carcinomas (12.2%). Three of these four mutated cell lines were MSI. PTEN was inactivated in 66.1% of the CRC. Furthermore, we observed a strong association between PIK3CA mutations and MSI status (P=0.0046) while PTEN loss was more frequent in microsatellite stable (MSS) CRC (P=0.043). A high prevalence of genetic alterations in PI3K/AKT pathway in Saudi cohort of CRC, predominance of PIK3CA mutations in the MSI subgroup and their possible involvement in development/progression of this subset of CRC are some of the significant findings of our study.