PIK3CA过表达对胃癌细胞侵袭力影响的探讨

目的:探讨PIK3CA过表达对胃癌细胞侵袭力的影响.方法:采用RT-PCR和蛋白质印迹法分别检测3种不同分化胃癌细胞HGC-27、BDC-823和SGC-7901中PIK3CA mRNA及蛋白表达水平.通过Transwell侵袭小室法检测其侵袭力,分析PTK3CA表达水平变化对胃癌细胞侵袭力的影响.结果:PIK3CAmRNA及蛋白在未分化HGC-27细胞中表达水平最高,细胞侵袭力最强(穿膜细胞数为45.24±3.16),在低分化BGC-823细胞(穿膜细胞数为22.28±1.65)及中等分化的SGC-7901细胞(穿膜细胞数为14.42±1.02)中分别次之(P<0.05).结论:PIK3CA mRNA及蛋白表达水平越高,细胞侵袭力越强,且后者随前者表达减少而减弱;PIK3CA过表达可能在胃癌细胞侵袭中起重要作用.     

Abrogation of PIK3CA or PIK3R1 reduces proliferation, migration, and invasion in glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is a highly invasive and deadly brain tumor. Tumor cell invasion makes complete surgical resection impossible and reduces the efficacy of other therapies. Genome-wide analyses of mutations, copy-number changes, and expression patterns have provided new insights into genetic abnormalities common in GBM. We analyzed published data and identified the invasion and motility pathways most frequently altered in GBM. These were most notably the focal adhesion and integrin signaling, and extracellular matrix interactions pathways. We mapped alterations in each of these pathways and found that they included the catalytic PIK3CA and regulatory PIK3R1 subunit genes of the class IA PI3K. Knockdown of either of these genes separately in GBM cell lines by lentiviral-mediated shRNA expression resulted in decreased proliferation, migration, and invasion in all lines tested. FAK activity was reduced by knockdown of either PIK3CA or PIK3R1, and MMP2 levels were reduced by knockdown of PIK3R1. We conclude that PIK3R1, like PIK3CA, is a potential therapeutic target in GBM and that it also influences tumor cell growth and motility.     

PIK3CA gene amplification in Japanese non-small cell lung cancer

We have investigated 92 non-small cell lung cancer tissues and found 11 PIK3CA amplification. PIK3CA amplification incidence was significantly higher in male, smoker and squamous cell carcinoma patients. Among 11 patients with PIK3CA amplification, two patients harbored a PIK3CA mutation. There was significant difference in survival between the patients with PIK3CA normal copy number and the patients with PIK3CA amplification.     

Functional analysis of PIK3CA gene mutations in human colorectal cancer

Mutations in the PIK3CA gene, which encodes the p110alpha catalytic subunit of phosphatidylinositol 3-kinase (PI3K), have been reported in human cancers, including colorectal cancer. Most of the mutations cluster at hotspots within the helical and kinase domains. Whereas H1047R, one of the hotspot mutants, is reported to have elevated lipid kinase activity, the functional consequences of other mutations have not been examined. In this study, we examined the effects of colon cancer-associated PIK3CA mutations on the lipid kinase activity in vitro, activation of the downstream targets Akt and p70S6K in vivo and NIH 3T3-transforming ability. Of eight mutations examined, all showed increased lipid kinase activity compared with wild-type p110alpha. All the mutants strongly activated Akt and p70S6K compared with wild-type p110alpha as determined by immunoblotting using phospho-specific antibodies. These mutants also induced morphologic changes, loss of contact inhibition, and anchorage-independent growth of NIH 3T3 cells. The hotspot mutations examined in this study, E542K, E545K, and H1047R, all had high enzymatic and transforming activities. These results show that almost all the colon cancer-associated PIK3CA mutations are functionally active so that they are likely to be involved in carcinogenesis.     

MicroRNA-10a targets CHL1 and promotes cell growth, migration and invasion in human cervical cancer cells

MicroRNAs (miRNAs) play an important role in cancer initiation, progression and metastasis by regulating their target genes. Here, we found microRNA-10a (miR-10a) is upregulated in human cervical cancer and promotes the colony formation activity, migration and invasion of HeLa and C33A cells. Subsequently, CHL1 is confirmed as a target of miR-10a and is negatively regulated by miR-10a at mRNA and protein levels. Furthermore, knockdown of CHL1 expression results in increased colony formation activity, migration and invasion. Finally, overexpression of CHL1 lacked the 3'UTR abolished the effects of miR-10a. Our results may provide a strategy for blocking tumor metastasis.     

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.     

PIK3CA基因与胃癌细胞分化及侵袭力相关性研究

目的 探讨PIK3CA mRNA表达水平与胃癌细胞分化及侵袭力相关性.方法 RT-PCR和Transwell侵袭小室法分别检测三种不同分化胃癌细胞中PIK3CA mRNA表达水平及侵袭力大小.结果 PIK3CA基因表达水平越高,细胞分化程度越低,细胞侵袭力越强.结论 PIK3CA mRNA 表达水平与胃癌细胞的分化程度、侵袭力密切相关;PIK3CA基因可能参与了胃癌的分化、浸润及转移,是较好的干预治疗的靶点.     

PTEN、PIK3CA在培美曲塞耐药的胰腺癌细胞株Patu8988中的表达及其意义的初步探讨

目的 探索胰腺癌细胞株Patu8988对培美曲塞产生获得性耐药的机制,分析PTEN、PIK3CA在获得耐药前后mRNA及蛋白水平变化及其对细胞迁移及侵袭能力的影响。方法 通过RT-PCR及Western blot技术分别检测正常胰腺癌细胞株Patu8988及培美曲塞耐药的胰腺癌细胞株Patu8988中PTEN及PIK3CA的mRNA及其蛋白产物表达水平变化。应用迁移及侵袭实验分别检测正常胰腺癌细胞株和耐药的胰腺癌细胞株不同生物学行为。结果 RT-PCR发现与正常胰腺癌细胞株Patu8988相比,培美曲塞耐药的胰腺癌细胞株Patu8988中,PTEN和PIK3CA在mRNA水平表达均显著增高;Western blot发现培美曲塞耐药的胰腺癌细胞株Patu8988中PTEN、PIK3CA在蛋白水平同样表达升高,PTEN和PIK3CA在耐药的胰腺癌细胞株中的表达较正常胰腺癌细胞株分别上升89%和76%;迁移及侵袭实验的结果显示,培美曲塞耐药的胰腺癌细胞株Patu8988迁移及侵袭能力较正常胰腺癌细胞株Patu8988均显著下降(P＜0.05)。结论 PTEN、PIK3CA在对培美曲塞耐药的胰腺癌细胞株Patu8988中表达均异常升高,而同时高表达PTEN和PIK3CA的胰腺癌耐药细胞株的迁移及侵袭能力较正常胰腺癌细胞株显著降低,提示PTEN和PIK3CA共同参与胰腺癌细胞对培美曲塞产生获得性耐药过程,且有可能改变细胞的生物学行为。     

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.     

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).     

Co-activation of PIK3CA and Yap promotes development of hepatocellular and cholangiocellular tumors in mouse and human liver

Activation of the PI3K and Yes-associated protein (Yap) signaling pathways has been independently reported in human hepatocellular carcinoma (HCC). However, the oncogenic interactions between these two cascades in hepatocarcinogenesis remain undetermined. To assess the consequences of the crosstalk between the PI3K and Yap pathways along liver carcinogenesis, we generated a mouse model characterized by combined overexpression of activated mutant forms of PIK3CA (PIK3CAH1047R) and Yap (YapS127A) in the mouse liver using hydrodynamic transfection (PIK3CA/Yap). In addition, suppression of PI3K and Yap pathways was conducted in human HCC and cholangiocarcinoma (CCA) cell lines. We found that concomitant activation of PI3K and Yap pathways triggered rapid liver tumor development in mice. Histologically, tumors were pure HCC, CCA, or mixed HCC/CCA. At the molecular level, PIK3CA/Yap tumors were characterized by activation of the mTORC1/2, ERK/MAPK, and Notch pathways. Simultaneous activation of PI3K and Yap pathways frequently occurred in human liver tumor specimens and their combined suppression was highly detrimental for the growth of HCC and CCA cell lines. In conclusion, our study demonstrates the oncogenic cooperation between PI3K and Yap pathways along liver carcinogenesis. The PIK3CA/Yap mouse represents an important preclinical liver tumor model for the development of novel therapeutics against this malignancy.     

Mutant PIK3CA-bearing colon cancer cells display increased metastasis in an orthotopic model

Mutations in the PIK3CA gene are common in human cancers, including colon cancer. We compared two pairs of colon cancer cells (HCT116 and DLD1) bearing only the wild-type (WT) or mutant (MUT) PIK3CA allele for their survival capacity under stress conditions in vitro as well as their metastatic properties in an in vivo orthotopic model. When subjected to growth factor deprivation stress (GFDS), the MUT PIK3CA cells displayed resistance to GFDS-induced apoptosis relative to the WT cells. Phosphatidylinositol 3-kinase (PI3K) and its downstream effector AKT were constitutively activated during stress conditions in the MUT PIK3CA cells but not in the WT cells. The MUT cells showed hypersensitivity to PI3K inhibition. Moreover, the proapoptotic protein Bax was expressed at a very high level in the WT PIK3CA cells, whereas it was almost undetectable in the MUT cells. Inhibition of Bax expression by small interfering RNA protected the WT PIK3CA cells from GFDS-induced apoptosis, suggesting an important role of Bax in GFDS-induced apoptosis. These results indicated that the MUT PI3K confers resistance to GFDS-induced apoptosis and that the MUT cells are more dependent on the PI3K pathway for survival. In vivo studies showed that the MUT PIK3CA-bearing cells were more metastatic than the WT cells in an orthotopic model of colon cancer. Taken together, these results suggest that MUT PI3K imparts a more aggressive phenotype in colon cancer cells and could be a potential therapeutic target for treatment of colon cancer patients bearing PIK3CA mutations.     

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。     

Insulin-like growth factor binding protein 2 promotes ovarian cancer cell invasion

Background  

Insulin-like growth factor binding protein 2 (IGFBP2) is overexpressed in ovarian malignant tissues and in the serum and cystic fluid of ovarian cancer patients, suggesting an important role of IGFBP2 in the biology of ovarian cancer. The purpose of this study was to assess the role of increased IGFBP2 in ovarian cancer cells.     

Mutation of the PIK3CA oncogene in human cancers

It is now well established that cancer is a genetic disease and that somatic mutations of oncogenes and tumour suppressor genes are the initiators of the carcinogenic process. The phosphatidylinositol 3-kinase signalling pathway has previously been implicated in tumorigenesis, and evidence over the past year suggests a pivotal role for the phosphatidylinositol 3-kinase catalytic subunit, PIK3CA, in human cancers. In this review, we analyse recent reports describing PIK3CA mutations in a variety of human malignancies, and discuss their possible implications for diagnosis and therapy.     

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.