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。     

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.     

Correlation of breast tumour aromatase activity and response to aromatase inhibition with aminoglutethimide

Tumour aromatase, oestrogen (E) and progesterone (P) receptor (R) measurements were carried out in biopsies from 29 patients with advanced or recurrent breast cancer. Patients were then treated with aminoglutethimide according to one of two dosage regimens: (a) aminoglutethimide 1000 mg/day + hydrocortisone 20 mg/day, and (b) aminoglutethimide 250 mg/day. Tumour aromatase values varied from 0.05 to 2.07 pmol ER produced/mg protein/h and ER and PR values from less than 1 to 249 and less than 1 to 132 fmol of steroid bound/mg protein, respectively. There was no correlation between aromatase values and either ER or PR and also no correlation between ER and PR and response to aminoglutethimide. Tumour aromatase values did however correlate with response to treatment. Mean aromatase levels for responders (1.18 +/- 0.64 pmol E produced/mg protein/h) were significantly higher than those of non-responders (0.34 +/- 0.27) (t = 5.20, DF 27; p less than 0.005). Ten out of fourteen patients with aromatase values greater than 0.5 pmol ER produced/mg protein/h responded, whereas 0 out of 15 patients with tumour aromatase values less than this responded. Responses were seen at both dosages of aminoglutethimide. It is concluded that tumour aromatisation will be a useful measurement in predicting response to aromatase inhibitors.     

PIK3CA cooperates with other phosphatidylinositol 3'-kinase pathway mutations to effect oncogenic transformation

Mutations in genes functioning in different pathways frequently occur together in the same cancer, whereas mutations in the same pathway tend to be mutually exclusive. However, the majority of colon, breast, and endometrial cancers that possess mutations in PIK3CA, the catalytic subunit p110alpha of phosphatidylinositol 3'-kinase (PI3K), also possess mutations or alterations in genes upstream of PI3K such as Ras, ERBB2/ERBB3, or PTEN. PIK3CA mutations occur almost exclusively in invasive tumors, whereas upstream mutations occur as frequently in early-stage and late-stage tumors, suggesting that PIK3CA mutation is a late-stage event that may augment earlier activation of the PI3K pathway. Consistent with this, we find that levels of p-AKT (Ser(473)) induced by mutant Ras or knockdown of PTEN were dramatically increased by addition of mutant PIK3CA. Soft agar assays revealed that anchorage-independent growth induced by mutant Ras was greatly increased in the presence of mutant PIK3CA. In breast, colon, and endometrial cancers in which the PI3K pathway is activated by a combination of mutant PIK3CA and alterations in Ras, ERBB2/3, or PTEN, signaling to downstream elements such as Akt was mediated exclusively by the p110alpha isoform, rather than a combination of different PI3K isoforms. Our data therefore suggest that in tumors with co-occurring mutations in multiple components of the PI3K pathway, selective inhibition of the alpha isoform of p110 is an attractive therapeutic strategy, especially for late-stage tumors.     

PIK3CA mutation in Chinese patients with lung squamous cell carcinoma

Objective

To investigate PIK3CA mutation in Chinese patients with lung squamous cell carcinoma (LSCC) and explore their relationship with clinicopathological profiles.

Methods

Tumor samples from 123 cases of LSCC were included in this study. PIK3CA mutations in exon 9 and 20 were screened by pyrosequencing and confirmed by clone sequencing or amplification refractory mutation system (ARMS). Denaturing performance liquid chromatography (DHPLC) was employed for evaluation of EGFR mutation in exon 19, 21 and KRAS mutation.

Results

PIK3CA mutations were found in 3 (2.4%) patients. The mutation type included E545K, E452Q and H1047R. Of these three patients, one coupled with EGFR mutation, and the other two coupled with PIK3CA amplification. All the three patients shared the same clinicopathologic characteristics: male, less than 60 years old, had smoke history, stage III and carried wild-type KRAS.

Conclusions

The frequency of PIK3CA mutation is low in Chinese patients with LSCC. The mutational status of PIK3CA is not mutually exclusive to EGFR mutation.Key Words: Lung squamous cell carcinoma (LSCC), PIK3CA mutation, EGFR mutation, KRAS mutation     

PIK3CA mutation status in Japanese lung cancer patients

Somatic mutations of the PIK3CA (phosphatidylinostitol 3-kinase catalytic subunit) gene have been found in human cancer patients. Previous reports suggested that about 4% of lung cancers harbored PIK3CA gene mutations. However, the clinico-pathological background for PIK3CA gene mutations has not yet been investigated in lung cancer. We have genotyped the PIK3CA gene in Japanese lung cancer patients. The study included 235 lung cancer cases surgically removed in Nagoya City University Hospital. The two PIK3CA mutation hot spots (exon 9 and exon 20) were analyzed by real time polymerase chain reaction (PCR)-based assay. The data were confirmed by direct sequencing. In exon 9, somatic mutation was found in eight patients (3.4%). The mutation included three E542K (G1624A), three E545K (G1633A), one E542Q (G1624C), and one Q546K (C1636A). However, in exon 20, there was no mutation in our lung cancer patients. PIK3CA mutations were not correlated with gender (women versus men, p=0.4162), age (< or =60 versus >60, p=0.8027), or smoking status of the lung cancers (never versus smoker, p=0.5666). PIK3CA mutation incidence was significantly lower in adenocarcinoma (2/135, 1.5%) than in squamous cell carcinoma (5/77, 6.5%, p=0.0495). Among eight patients with a PIK3CA mutation, three patients also harbored an EGFR somatic mutation. PIK3CA gene mutations were rare in lung cancer; rarer in adenocarcinoma. Further functional analyses of the PIK3CA mutations are warranted to study if they could be the target of therapy for the lung cancer.     

PIK3CA基因突变在结直肠癌中的研究进展

结直肠癌是较常见的恶性肿瘤,发病率在我国呈逐年上升趋势.肿瘤的发生是多因素、多阶段、多基因改变的结果,包括原癌基因的激活与抑癌基因的失活.PIK3 CA基因是近年发现的除KRAS突变之外的结直肠癌常见的突变基因,PI3K下游信号通路的异常活化在结直肠癌的发生过程中发挥着重要的作用.本文就PIK3CA基因的生物学作用,参与肿瘤不同阶段的发展,以及PIK3CA作为肿瘤标志物和分子靶点的潜在临床价值简要作一综述.     

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 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.     

Carcinogenesis of PIK3CA

PIK3CA is the most frequently mutated oncogene in human cancers. PIK3CA is phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha. It controls cell growth, proliferation, motility, survival, differentiation and intracellular trafficking. In most of human cancer alteration occurred frequently in the alpha isoform of phosphatidylinositol 3 kinase. PIK3CA mutations were most frequent in endometrial, ovarian, colorectal, breast, cervical, squamous cell cancer of the head and neck, chondroma, thyroid carcinoma and in cancer family syndrome. Inhibition of PI3K signaling can diminish cell proliferation, and in some circumstances, promote cell death. Consequently, components of this pathway present attractive targets for cancer therapeutics. A number of PI3K pathway inhibitors have been developed and used. PI3K inhibitors (both pan-PI3K and isoform-specific PI3K inhibitors), dual PI3K-mTOR inhibitors that are catalytic site inhibitors of the p110 isoforms and mTOR (the kinase component of both mTORC1 and mTORC2), mTOR catalytic site inhibitors, and AKT inhibitors are the most advanced in the clinic. They are approved for the treatment of several carcinomas.     

PIK3CA Mutation in Colorectal Cancer: Relationship with Genetic and Epigenetic Alterations

Somatic PIK3CA mutations are often present in colorectal cancer. Mutant PIK3CA activates AKT signaling, which up-regulates fatty acid synthase (FASN). Microsatellite instability (MSI) and CpG island methylator phenotype (CIMP) are important molecular classifiers in colorectal cancer. However, the relationship between PIK3CA mutation, MSI and CIMP remains uncertain. Using Pyrosequencing technology, we detected PIK3CA mutations in 91 (15%) of 590 population-based colorectal cancers. To determine CIMP status, we quantified DNA methylation in eight CIMP-specific promoters [CACNA1G, CDKN2A (p16), CRABP1, IGF2, MLH1, NEUROG1, RUNX3, and SOCS1] by real-time polymerase chain reaction (MethyLight). PIK3CA mutation was significantly associated with mucinous tumors [P = .0002; odds ratio (OR) = 2.44], KRAS mutation (P < .0001; OR = 2.68), CIMP-high (P = .03; OR = 2.08), phospho-ribosomal protein S6 expression (P = .002; OR = 2.19), and FASN expression (P = .02; OR = 1.85) and inversely with p53 expression (P = .01; OR = 0.54) and β-catenin (CTNNB1) alteration (P = .004; OR = 0.43). In addition, PIK3CA G-to-A mutations were associated with MGMT loss (P = .001; OR = 3.24) but not with MGMT promoter methylation. In conclusion, PIK3CA mutation is significantly associated with other key molecular events in colorectal cancer, and MGMT loss likely contributes to the development of PIK3CA G>A mutation. In addition, Pyrosequencing is useful in detecting PIK3CA mutation in archival paraffin tumor tissue. PIK3CA mutational data further emphasize heterogeneity of colorectal cancer at the molecular level.     

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.     

Frequent mutation of the PIK3CA gene in ovarian and breast cancers.

PURPOSE: Activation of the phosphatidylinositol 3-kinase (PI3K)-AKT pathway, resulting in increased cell proliferation, survival, and motility, is believed to play an oncogenic role in many cancer types. The PIK3CA gene encodes the p110alpha catalytic subunit of PI3K, and is amplified in some ovarian cancers, whereas the AKT2 gene is amplified in some ovarian, breast, and pancreatic cancers. Recently, in a mutational screen of eight PI3K genes and eight PI3K-like genes, PIK3CA was found to be the only gene affected by somatic mutations, which were observed frequently in gastrointestinal and brain cancers. Here, we test whether PIK3CA is subject to mutation in ovarian and breast cancers.EXPERIMENTAL DESIGN: Exons 9 and 20, encoding the highly conserved helical and kinase domains of PIK3CA, were subjected to sequence analysis in 198 advanced stage epithelial ovarian carcinomas and 72 invasive breast carcinomas (48 of ductal histology and 24 of lobular histology).RESULTS: Somatic missense mutations were observed in 24 of 198 (12%) ovarian carcinomas, and in 13 of 72 (18%) breast carcinomas.CONCLUSIONS: These data indicate that mutations of PIK3CA play an oncogenic role in substantial fractions of ovarian and breast carcinomas, and in consideration of mutation of other components of the PI3K-AKT pathway in both tumor types, confirm the major oncogenic role of this pathway in ovarian and breast carcinomas.     

Mutant PIK3CA controls DUSP1-dependent ERK 1/2 activity to confer response to AKT target therapy

Background:

Alterations in the phosphoinositide 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) signalling pathway are frequent in urothelial bladder cancer (BLCA) and thus provide a potential target for novel therapeutic strategies. We investigated the efficacy of the AKT inhibitor MK-2206 in BLCA and the molecular determinants that predict therapy response.

Methods:

Biochemical and functional effects of the AKT inhibitor MK-2206 were analysed on a panel of 11 BLCA cell lines possessing different genetic alterations. Cell viability (CellTiter-Blue, cell counts), apoptosis (caspase 3/7 activity) and cell cycle progression (EdU incorporation) were analysed to determine effects on cell growth and proliferation. cDNA or siRNA transfections were used to manipulate the expression of specific proteins such as wild-type or mutant PIK3CA, DUSP1 or CREB. For in vivo analysis, the chicken chorioallantoic membrane model was utilised and tumours were characterised by weight and biochemically for the expression of Ki-67 and AKT phosphorylation.

Results:

Treatment with MK-2206 suppressed AKT and S6K1 but not 4E-BP1 phosphorylation in all cell lines. Functionally, only cell lines bearing mutations in the hotspot helical domain of PIK3CA were sensitive to the drug, independent of other genetic alterations in the PI3K or MAPK signalling pathway. Following MK-2206 treatment, the presence of mutant PIK3CA resulted in an increase in DUSP1 expression that induced a decrease in ERK 1/2 phosphorylation. Manipulating the expression of mutant or wild-type PIK3CA or DUSP1 confirmed that this mechanism is responsible for the induction of apoptosis and the inhibition of tumour proliferation in vitro and in vivo, to sensitise cells to AKT target therapy.

Conclusion or interpretation:

PIK3CA mutations confer sensitivity to AKT target therapy in BLCA by regulating DUSP1 expression and subsequent ERK1/2 dephosphorylation and can potentially serve as a stratifying biomarker for treatment.     

Hotspot mutations in PIK3CA associate with first-line treatment outcome for aromatase inhibitors but not for tamoxifen

PIK3CA mutations occur frequently in breast cancer, predominantly in exons 9 and 20. The aim of this retrospective study is to evaluate the PIK3CA mutation status for its relationship with prognosis and first-line endocrine therapy outcome. PIK3CA exon 9 and 20 were evaluated for mutations in 1,352 primary breast cancer specimens by SnaPshot multiplex analyses. The mutation status was studied for their relationship with metastasis-free survival (MFS) in 342 untreated lymph node-negative (LNN) patients and to time to progression (TTP) in estrogen receptor (ER)-positive patients with metastatic disease treated with first-line tamoxifen (N = 447) or aromatase inhibitors (AIs; N = 84). We detected in 423 patients hotspot mutations for PIK3CA (31 %). Mutations in exon 20 were detected in 251 patients (59 %), with H1047L and H1047R mutations in 37 (15 %) and 214 (85 %) cases, respectively. Mutations in PIK3CA exon 9 were discovered in 173 patients (41 %), with E542K and E545K mutations in 57 (32 %) and 104 (60 %) cases as most prevalent ones. Evaluation of the untreated LNN patients for prognosis showed no relationship between MFS and PIK3CA mutations, neither for exon 9 [HR = 1.04 (95 % CI 0.57–1.89), P = 0.90] nor for exon 20 [HR = 0.98 (95 % CI 0.63–1.54); P = 0.94] when compared to wild-type. The PIK3CA mutation status was also not associated with treatment outcome after first-line tamoxifen. On the other hand, patients treated with first-line AIs showed a longer TTP when having a PIK3CA mutation in exon 9 [HR = 0.40 (95 % CI 0.17–0.95); P = 0.038] or exon 20 [HR = 0.50 (95 % CI 0.27–0.91); P = 0.024] compared to wild-types, both significant in uni- and multivariate analysis including traditional predictive factors. All results remained when only HER2-negative patients were evaluated for each cohort. PIK3CA mutations in ER-positive tumors were significantly associated with a favorable outcome after first-line AIs, which needs further confirmation in other datasets. Mutations were not associated with prognosis in untreated LNN patients nor predictive outcome after first-line tamoxifen therapy in advanced disease patients.     

胃癌患者错配修复缺陷和PIK3CA基因突变与临床病理特征的关系

目的:分析胃癌中错配修复缺陷(dMMR)和PIK3CA基因突变分别与临床病理特征的关联,以及两者之间的相关性。方法:选取本中心554例胃癌肿瘤组织标本,收集临床病理参数。免疫组化检测错配修复蛋白MSH2、MSH6、MLH1和PMS2,评判是否为dMMR。ARMS-PCR检测PIK3CA基因突变。应用统计学方法,分析dMMR和PIK3CA突变与临床病理特征的关系,以及dMMR与PIK3CA突变的关联。结果:554例胃癌患者中,dMMR 30例(5.4%)。其中,MLH1和PMS2双缺失27例(90.0%),MSH2和MSH6双缺失2例(6.7%),PMS2缺失1例（3.3%）。PIK3CA突变34例（6.1%）,其中15例E545 K (44.1%), 7例E542 K (20.1%),1例E545D(2.9%),6例H1047R(17.6%),4例H1047L(11.8%),1例E545K和E542K双突变（2.9%）。9号外显子突变24例（70.6%）,20号外显子突变10例（29.4%）。单因素分析发现,dMMR与女性,年龄> 65岁,肿瘤直径> 5 cm,肿瘤未侵及浆...     

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 mutation/PTEN expression status predicts response of colon cancer cells to the epidermal growth factor receptor inhibitor cetuximab

Cetuximab is a monoclonal antibody that targets the human epidermal growth factor receptor (EGFR). Although approved for use in EGFR-overexpressing advanced colorectal cancer, recent studies have shown a lack of association between EGFR overexpression and cetuximab response, requiring the identification of novel biomarkers predictive of response to this agent. To do so, 22 colon cancer cell lines were screened for cetuximab response in vitro and sensitive and resistant lines were identified. In sensitive cell lines, cetuximab induced a G(0)-G(1) arrest without inducing apoptosis. Notably, cetuximab-sensitive but not cetuximab-resistant cell lines were preferentially responsive to EGF-stimulated growth. Whereas neither EGFR protein/mRNA expression nor gene copy number correlated with cetuximab response, examination of the mutation status of signaling components downstream of EGFR showed that cell lines with activating PIK3CA mutations or loss of PTEN expression (PTEN null) were more resistant to cetuximab than PIK3CA wild type (WT)/PTEN-expressing cell lines (14 +/- 5.0% versus 38.5 +/- 6.4% growth inhibition, mean +/- SE; P = 0.008). Consistently, PIK3CA mutant isogenic HCT116 cells showed increased resistance to cetuximab compared with PIK3CA WT controls. Furthermore, cell lines that were PIK3CA mutant/PTEN null and Ras/BRAF mutant were highly resistant to cetuximab compared with those without dual mutations/PTEN loss (10.8 +/- 4.3% versus 38.8 +/- 5.9% growth inhibition, respectively; P = 0.002), indicating that constitutive and simultaneous activation of the Ras and PIK3CA pathways confers maximal resistance to this agent. A priori screening of colon tumors for PTEN expression status and PIK3CA and Ras/BRAF mutation status could help stratify patients likely to benefit from this therapy.