Enzymatic and antisense effects of a specific anti-Ki-ras ribozyme in vitro and in cell culture.

Due to their mode of action, ribozymes show antisense effects in addition to their specific cleavage activity. In the present study we investigated whether a hammerhead ribozyme is capable of cleaving mutated Ki-ras mRNA in a pancreatic carcinoma cell line and whether antisense effects contribute to the activity of the ribozyme. A 2[prime]-O-allyl modified hammerhead ribozyme was designed to cleave specifically the mutated form of the Ki- ras mRNA (GUU motif in codon 12). The activity was monitored by RT-PCR on Ki- ras RNA expression by determination of the relative amount of wild type to mutant Ki-ras mRNA, by 5-bromo-2[prime]-deoxy-uridine incorporation on cell proliferation and by colony formation in soft agar on malignancy in the human pancreatic adenocarcinoma cell line CFPAC-1, which is heterozygous for the Ki-ras mutation. A catalytically inactive ribozyme was used as control to differentiate between antisense and cleavage activity and a ribozyme with random guide sequences as negative control. The catalytically active anti-Ki-ras ribozyme was at least 2-fold more potent in decreasing cellular Ki-ras mRNA levels, inhibiting cell proliferation and colony formation in soft agar than the catalytically inactive ribozyme. The catalytically active anti-Ki-ras ribozyme, but not the catalytically inactive or random ribozyme, increased the ratio of wild type to mutated Ki-ras mRNA in CFPAC-1 cells. In conclusion, both cleavage activity and antisense effects contribute to the activity of the catalytically active anti-Ki-ras hammerhead ribozyme. Specific ribozymes might be useful in the treatment of pancreatic carcinomas containing an oncogenic GTT mutation in codon 12 of the Ki-ras gene.     

Concurrent mutations in two different ras genes in acute myelocytic leukemias.

DNA transfection analyses (tumorigenicity assay) and hybridization to mutation specific oligonucleotide probes established point mutations in codon 61 of both, N-ras and Ki-ras genes in fresh leukemic cells of an AML patient. Concurrent activation of N-ras and Ki-ras sequences by point mutations in codons 12 were demonstrated for AML cell line Rc2a. Moreover, using a rapid and sensitive dot-blot screening procedure based on the combination of in vitro amplification of ras specific sequences and oligonucleotide hybridization we could show that ras gene activation was not present in primary leukemic cells of the patient this cell line had been derived from, but rather occurred during later passages of Rc2a.     

应用PCR及寡核苷酸探针研究人原发性肺癌中Ki-ras点突变

应用PCR及寡核苷酸探针杂交方法研究了50例人原发性肺癌石蜡切片标本 中Ki-ras 12(Val),Ki-ras 13(Cys)点突变,发现13例为点突变阳性,突变率为26％,其中3例同时兼有二种点突变(Val/Cys);Ki-ras 12位的点突变率(20％)比Ki-ras 13位的点突变率(12％)高。同时还发现Ki-ras基因的点突变存在于腺癌、鳞癌、小细胞肺癌以及各种分化程度的肺癌中。     

Oncogene alterations in in vitro transformed rat tracheal epithelial cells.

10 derivations of rat tracheal epithelial (RTE) cells, including normal cells, normal primary cultures, 7 tumorigenic cell lines and 1 nontumorigenic cell line transformed in vitro by treatment with 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BP) and/or 12-O-tetradecanoylphorbol-13-acetate (TPA) were examined for oncogene alterations. No abnormalities of Ha-ras or Ki-ras were seen that were suggestive of amplification, rearrangement or the presence of RFLPs. Analysis of specific-point mutations in Ha-ras using Pst I digestion (codon 12, GGA to GCA) or Ha-ras and Ki-ras using Xba I (codon 61, CAA to CTA) were negative. In one cell line derived by DMBA treatment, changes in the c-myc restriction digest pattern were seen after incubation with Bam HI and Hind III. Northern analysis revealed consistent differences between normal and transformed cells when probed with Ha-ras; c-myc expression was of low intensity, and the expression of Ki-ras could not be detected. Transfection of RTE cell DNAs into NIH/3T3 cells did not result in the appearance of morphologic transformants. The studies suggest that Ha-ras or Ki-ras codon 61 A to T transversions (CAA to CTA) are not associated with the immortal/tumorigenic phenotype in RTE cells transformed by DMBA or TPA, and are in contrast to results reported in some other biological systems.     

The insulin-like growth factor binding protein BP-25 is expressed by human breast cancer cells

Specific binding proteins are thought to modulate the effects of IGF-I. Previous work has demonstrated that media conditioned by human breast cancer cells contains IGF-I binding activity. Radiolabelled IGF-I incubated with serum-free conditioned media from the breast cancer cell line MDA-MB 231 eluted with an apparent M.W. of 35-40 kDa when analyzed by gel filtration chromatography at pH 7.4. The M.W. of this binding activity corresponded to that of BP-25, a binding protein cloned from the hepatocellular carcinoma cell line HepG2. Two breast cancer cell lines, MDA-MB 231 and Hs578T, were found to express BP-25 RNA. Specific BP-25 radioimmunoassay detected BP-25 production in the conditioned media of these two cell lines. Immunoprecipitation confirmed that metabolically labelled MDA-MB 231 released 30 kDa BP-25 into its medium. This study demonstrates that some breast cancer cells express the IGF-I binding protein, BP-25.     

Molecular cloning of the 25 kbp region upstream of exon 0 of the human Ki-ras oncogene and its conservation in transformed mouse NIH 3T3 cells

Human sequences associated with the Ki-ras oncogene of the mammary tumour cell line, H-466B have been cloned from a tertiary NIH3T3 mouse transfectant. These sequences are located 5' upstream of exon 0 of the Ki-ras oncogene, span over 25 kbp of DNA and are conserved in half of the primary transfectants obtained with the Ki-ras gene of different types of tumours. No gross alterations were observed in the sequences upstream of the Ki-ras gene. The partial or total deletion of these sequences in the other half of primary transformants argues that they are not absolutely required for the transforming activity of the Ki-ras oncogene. The even distribution of the human-mouse junction points in primary transformed mouse cells suggests the absence of a specific region of recombination in the 5' flanking region of Ki-ras.     

Artichoke polyphenols induce apoptosis and decrease the invasive potential of the human breast cancer cell line MDA-MB231

The human breast cancer cell line, estrogen receptor negative, MDA-MB231, was used to evaluate the antitumor effect of polyphenolic extracts from the edible part of artichokes (AEs). Treatment of cancer cells reduced cell viability and inhibited cell growth in a dose-dependent manner. Importantly, AEs did not have any effect on normal breast epithelial cell line, MCF10A. Chlorogenic acid (ChA), the most representative component of the polyphenolic fraction of artichoke, had no prominent effects on the cell death rate of MDA-MB231 cells. The addition of AEs to the cells, rather than ChA, triggered apoptosis via a mitochondrial and a death-receptor pathway, as shown by the activation of caspase-9 and caspase-8, respectively. Furthermore, an increase of the Bax:Bcl2 ratio and up-regulation of cyclin-dependent kinase inhibitor, p21(WAF1), crucial apoptotic players, were documented. According to our data on activation of caspase-9, a loss of mitochondrial transmembrane potential (Ψ(m)) was shown. Cell motility and invasion capabilities were remarkably inhibited by AEs-treatment in highly invasive MDA-MB231 cells. In addition, a significant decrease of proteolytic activity of metalloproteinase-2 protein (MMP-2), involved in degrading components of the extracellular matrix, was detected. Our findings indicate that AEs reduced cell viability, inhibited cell growth, triggered apoptotic mechanisms, and showed inhibitory properties against the invasive behavior of MDA-MB231 cancer cell line. Altogether, these data indicate the potential chemopreventive activity of artichoke polyphenolic extracts.     

Transcriptional activation of collagenase-3 by transforming growth factor-beta1 is via MAPK and Smad pathways in human breast cancer cells

Transforming growth factor (TGF)-beta1, a crucial molecule in metastatic bone cancer, stimulates collagenase-3 expression in the human breast cancer cell line, MDA-MB231. Cycloheximide inhibited this stimulation, indicating that de novo protein synthesis was essential for this response. We examined whether mitogen-activated protein kinase (MAPK) and/or Smad pathways are involved in TGF-beta1-stimulated collagenase-3 expression in MDA-MB231 cells. Biochemical blockade of extracellular regulated kinase-1/2 and p38 MAPK pathways partially abolished TGF-beta1-stimulated collagenase-3 mRNA expression; whereas overexpression of a dominant negative form of Smad3 completely blocked the TGF-beta1-response. These data indicate that TGF-beta1-induced MAPK and Smad pathways are involved in TGF-beta1-stimulated collagenase-3 expression in MDA-MB231 cells.     

沉默CXCL1基因抑制三阴性乳腺癌细胞MDA-MB-231的迁移、侵袭的研究

为探讨CXCL1基因对三阴性乳腺癌细胞MDA-MB-231的迁移、侵袭作用的影响,该研究设计针对CXCL1基因的小干扰RNA,用实时荧光定量PCR和酶联免疫吸附测定试验分别在RNA和蛋白质水平上检测干扰效率;采用流式细胞术学技术检测细胞的周期和凋亡情况;采用transwell迁移和侵袭试验分别检测细胞的迁移及侵袭能力。结果显示,与siRNA-NC组细胞相比,siCXCL1-1、siCXCL1-2、siCXCL1-3细胞中CXCL1基因的mRNA和蛋白表达均下调,且si CXCL1-3干扰效率最高,mRNA及蛋白表达水平分别降低了75%(p<0.01)和46%(p<0.01)。细胞凋亡试验和细胞周期试验结果显示,沉默CXCL1基因后对三阴性乳腺癌细胞系MDA-MB-231细胞的凋亡和周期无明显影响,差异无统计学意义(p>0.05)。transwell小室迁移和侵袭试验显示,沉默CXCL1基因能够显著抑制三阴性乳腺癌细胞MDA-MB-231的迁移和侵袭能力(p<0.01)。研究成果为临床乳腺癌中以CXCL1基因为靶点的分子治疗提供了理论依据。     

Point mutation of estrogen receptor (ER) in the ligand-binding domain changes the pharmacology of antiestrogens in ER-negative breast cancer cells stably expressing complementary DNAs for ER.

The antiestrogen tamoxifen is used in the treatment of hormone-responsive breast cancer. However, therapeutic failure has frequently been observed in both patients and animal models after long term treatment. We have studied the effect of a point mutation that leads to the substitution of Val for Gly at codon 400 in the ligand-binding domain of the estrogen receptor (ER) on estrogenic and antiestrogenic activities of 4-hydroxytamoxifen (4-OHT) and its derivatives. Stable ER transfectants derived from MDA-MB-231 CL10A, an ER-negative breast cancer cell line, have been used in these studies. 4-OHT and its fixed ring derivatives showed more estrogen-like activity in ER transfectants than in MCF-7, an ER-positive breast cancer cell line. In this study, 4-OHT was a partial agonist of cell growth in the transfectant S30 cells, which express the wild-type ER. However, it was a full agonist in the mutant ER transfectant ML alpha 2H, which expressed ER with Val at codon 400. The increased estrogenic activity of 4-OHT in ML alpha 2H cells was not due to the preferential isomerization of trans 4-OHT to cis 4-OHT, since the nonisomerizable fixed ring trans 4-OHT was a partial agonist for cell growth in S30 cells and was a full agonist in ML alpha 2H cells. Transient transfection using a reporter plasmid containing an estrogen response element demonstrated that fixed ring trans 4-OHT had estrogenic activity in ML alpha 2H cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

针对uPA的siRNA对人乳腺癌细胞侵袭的抑制作用

目的:通过RNA干涉的方法抑制乳腺癌细胞中uPA的表达,观察uPA的表达抑制后对肿瘤细胞的体外侵袭能力的影响。方法:(1)构建可以表达针对uPA的siRNA的干涉载体,转染高侵袭性人乳腺癌细胞系MDA-MB231,G418抗性筛选,挑选单克隆株;(2)分别通过RT-PCR和WesternBlot的方法检测uPA的表达;(3)平板克隆形成试验检测转染前后肿瘤细胞的克隆形成能力;4BovdenchamberAssay检测肿瘤细胞体外侵袭能力。结果:(1)可以稳定表达针对uPA的siRNA的单克隆株,uPA的表达水平显著下降;(2)转染了针对uPA的siRNA的单克隆株的克隆形成能力降低;(3)转染了针对uPA的siRNA的单克隆株体外侵袭能力与原代细胞MDA-MB231相比明显受到抑制。结论:uPA在人乳腺癌侵袭行为中发挥重要的作用,针对uPA的siRNA可以显著降低uPA的表达,从而抑制肿瘤细胞的侵袭,可望成为抗肿瘤侵袭治疗的一种有效手段。     

C-terminus of Hsc70-interacting protein regulates profilin1 and breast cancer cell migration

Profilin1 (Pfn1) is a key mediator of actin polymerization and regulates cell migration. Low expression of Pfn1 is implicated in tumorigenesis of various cancers, including breast cancer. The regulatory mechanism behind Pfn1 levels has not yet been elucidated. In the present study, we find that Pfn1 is poly-ubiquitinated in human cell lines, and a portion of poly-ubiquitinated Pfn1 is regulated in a proteasome-dependent manner. C-terminus of Hsc70-interacting protein (CHIP), a co-chaperone E3 ligase, interacts with and ubiquitinates Pfn1, targeting it for proteasome-dependent degradation. Depletion of CHIP stabilizes Pfn1, suggesting that CHIP functions as a major E3 ligase for Pfn1. Stable expression of wild-type CHIP in the breast cancer cell line MDA-MB231 yielded downregulation of Pfn1 and enhanced cell migration. Pfn1 overexpression in MDA-MB231 cells expressing wild-type CHIP suppressed the enhanced cell migration. Taken together, our results demonstrate that CHIP regulates Pfn1 levels as an E3 ligase, and possibly plays a role in cell migration and metastasis of breast cancer.     

Insights on the antitumor effects of kahweol on human breast cancer: Decreased survival and increased production of reactive oxygen species and cytotoxicity

The present study aims to identify the modulatory effects of kahweol, an antioxidant diterpene present in coffee beans, on a panel of human tumor cell lines. Kahweol inhibits tumor cell proliferation and clonogenicity and induces apoptosis in several kinds of human tumor cells. In the estrogen receptor-negative MDA-MB231 human breast cancer, the mentioned effects are accompanied by caspases 3/7 and 9 activation and cytochrome c release. On the other hand, kahweol increases the production of reactive oxygen species and their cytotoxicity in human breast cancer cells but not in normal cells. Taken together, our data suggest that kahweol is an antitumor compound with inhibitory effects on tumor cell growth and survival, especially against MDA-MB231 breast cancer cells.     

Sulindac induces apoptotic cell death in susceptible human breast cancer cells through, at least in part, inhibition of IKKβ

Sulindac is a non-steroidal anti-inflammatory agent with anti-tumor activities that include the induction of apoptosis in various cancer cells and the inhibition malignant transformation. However, the molecular mechanisms underlying these effects are unclear. Recently, it has been shown that sulindac can inhibit NF-κB activation. Here, we demonstrate that sulindac induces apoptotic cell death in susceptible human breast cancer cells through, at least in part, inhibition of IKKβ activity. More specifically, when we compared two different human breast cancer cell lines, Hs578T, which has relatively low basal IKKβ activity, and MDA-MB231, which has relatively high basal IKKβ activity, we found that MDA-MB231 was markedly more sensitive to sulindac-induced apoptosis than Hs578T. This was associated with greater caspase-3 and -9 activity in sulindac-treated MDA-MB231 cells. Using a combination of chemical kinase inhibitors and siRNA-mediated knockdown of specific kinases, we found that sulindac inhibits IKKβ, which, in turn, leads to the p38 MAPK-dependent activation of JNK1. Together, these findings suggest that sulindac induces apoptosis in susceptible human breast cancer cells through, at least in part, the inhibition of IKKβ and the subsequent p38 MAPK-dependent activation of JNK1. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. A-Mi Seo and Seoug-Woo Hong have contributed equally.     

Oxidative and reductive pathways of estrogens in hormone responsive and non-responsive human breast cancer cells in vitro

In order to measure the formation and degradation rates of estradiol by human breast cancer cells, after assessing the biochemical basis of hormone responsiveness and growth response to estrogens, we considered both responsive, estrogen receptor (ER) positive, and non-responsive, ER-negative, breast cancer cell lines, i.e. MCF7, ZR75-1 and MDA-MB231. To this end, we employed a novel “intact cell” approach which allows us, after 24 h incubation, to analyze several enzyme activities in sequence, concurrently with the monitoring of labeled precursor degradation. Our investigations led to the following evidence: (a) the reductive activity of the 17β-hydroxysteroid oxoreductase (17β-HSOR) appears to be higher than the oxidative only in responsive, ER-rich MCF7 and ZR75-1 cells, as also previously observed by others; (b) this activity is, on the contrary, much lower in MDA-MB231 cells and other unresponsive, ER-poor breast cancer cell lines; (c) conversely, the oxidative activity shows an opposite pattern, being limited in MCF7 and ZR75-1 cells and much higher in MDA-MB231 cells. Overall, a 17β-HSOR reductive pathway prevails in both MCF7 and ZR75-1 cells, whilst the oxidative pathway is prevalent in MDA-MB231 cells, leading to a large formation of estrone that is no further metabolized, at least in the experimental conditions used. Our results may provide a likely explanation of previous data on the different estrogen content of breast tumor tissues.     

Effects of α-zearalenol on the metabolome of two breast cancer cell lines by 1H-NMR approach

Introduction

Zearalenone (ZEN) is one of the most widely distributed toxins that contaminates many crops and foods. Its major metabolites are α-Zearalenol (α-zol) and β-Zearalenol. Previous studies showed that ZEN and α-zol have estrogenic properties and are able to induce growth promoting effect in breast tissues.

Objectivies

Considering that tumorigenesis is dependent on the reprogramming of cellular metabolism and that the evaluation of the cellular metabolome is useful to understand the metabolic changes that can occur during the cancer development and progression or after treatments, aim of our work is to study, for the first time, the effects of α-zol on the metabolomic profile of an estrogen positive breast cancer cell line, MCF-7, and of an estrogen negative breast cancer cell lines MDA-MB231.

Methods

Firstly, we tested the effects of α-zol on the cell viability after 24, 48 and 72 h of treatments with 10^?10, 10^?8 and 10^?6 M concentrations on breast cancer MCF-7 and MDA-MB231 cell lines in comparison to human non-cancerous breast MCF10A cell line. Then, we evaluated cell cycle progression, levels of reactive oxygen species (ROS) and the metabolomic profiling by ¹H-NMR approach on MCF-7 and MDA-MB231 before and after 72 h treatments. Principal component analysis was used to compare the obtained spectra.

Results

α-zol is resulted able to induce: (i) an increase of the cell viability on MCF-7 cells mainly after 72 h treatment, (ii) a slight decrease of the cell viability on MDA-MB231 cells, and (iii) an increase of cells in S phase of the cell cycle and of ROS only in MCF-7 cells. Moreover, the evaluation of metabolomics profile evidenced that after treatment with α-zol the levels of some metabolites increased in MCF-7 cells whereas decreased slightly in MDA-MB231 cells.

Conclusions

Our results showed that α-zol was able to increase the protein biosynthesis as well as the lipid metabolism in MCF-7 cells, and, hence, to induce an estrogen positive breast cancer progression.

     

A human gastric carcinoma contains a single mutated and an amplified normal allele of the Ki-ras oncogene.

The DNA from various human tumors and tumor cell lines was screened for the presence of mutated ras oncogenes with synthetic oligonucleotide probes, as well as with the NIH/3T3 cell transfection assay. Among the various mutations found we discovered two novel Ki-ras mutations in codon 12: gly to ala and gly to ser. A gastric carcinoma was found to possess a single mutated Ki-ras allele (gly-12 to ser), as well as a 30-50 fold amplified normal allele. This implies that two activating steps must have occurred in this malignancy.     

miR-148a通过靶向调节己糖激酶2基因抑制乳腺癌细胞糖酵解和细胞增殖能力

为了探讨miR-148a及己糖激酶2（hexokinase 2,HK2）基因对人乳腺癌细胞糖酵解代谢途径的影响和可能机制,利用实时荧光定量PCR（real-time fluorescent quantitative PCR,qRT-PCR）检测多种乳腺癌细胞系中miR-148a的表达量,从中筛选miR-148a表达量相对较低的乳腺癌细胞系作为研究对象。再通过观察miR-148a表达量的变化对乳腺癌细胞葡萄糖摄取量、乳酸生成量和细胞增殖指标的影响,以探究miR-148a对乳腺癌细胞糖代谢能力的影响。随后,通过TargetScan在线数据库预测miR-148a和HK2基因的靶向关系,再通过双荧光素酶报告实验、Western免疫印迹以及基因回复实验进行验证,以进一步明确miR-148a和HK2在乳腺癌细胞的糖酵解代谢途径中的作用机制。通过qRT-PCR发现miR-148a在多种乳腺癌细胞系表达降低,尤其是在乳腺癌细胞系MDA-MB231中表达量显著降低（P<0.000 1）。过表达miR-148a使MDA-MB231细胞的葡萄糖摄取量、乳酸生成量、细胞增殖指标均显著下降（P<0.01）;而抑制miR-148a表达使MDA-MB231细胞葡萄糖摄取量、乳酸生成量、细胞增殖指标均显著上升（P<0.01）。通过TargetScan在线数据库预测得出,miR-148a与HK2基因3′非编码区（3′-untranslated region,3′-UTR）具有部分结合位点;而双荧光素酶报告实验发现miR-148a与野生型HK2基因的3′-UTR荧光素酶报告载体结合,不与突变型HK2基因的3′-UTR结合。Western免疫印迹检测结果表明,过表达miR-148a使MDA-MB231细胞中HK2蛋白表达量显著下降（P＜0.000 1）,而抑制miR-148a表达则促进HK2蛋白表达量显著上升（P<0.05）。基因回复实验显示,过表达HK2基因使MDA-MB231乳腺癌细胞的葡萄糖摄取量、乳酸生成量、细胞增殖指标显著上升（P＜0.01）;将过表达miR-148a载体与过表达HK2载体共转染MDA-MB231细胞,miR-148a逆转了HK2所致的葡萄糖摄取量增加和乳酸生成量上升,并抑制细胞增殖。因此,研究提示,miR-148a可通过靶向抑制HK2基因表达而抑制乳腺癌细胞MDA-MB231糖酵解代谢和细胞增殖。