EphA3基因稳定表达细胞模型的建立与分析

目的：建立稳定表达外源EphA3基因的小鼠成纤维细胞株模型,初步探讨EphA3基因表达对肿瘤发生、发展的影响。方法：通过脂质体介导的方法,将真核表达载体pcDNA3.1（-）/myc-his-EphA3转染NIH3T3细胞,用Western印迹确定外源EphA3基因表达;通过MTT实验、软琼脂集落形成实验,观察EphA3基因表达对NIH3T3细胞生物学特性的影响。结果：建立了稳定转染EphA3基因的NIH3T3细胞株;EphA3基因表达的小鼠成纤维NIH3T3细胞生长速度没有明显变化,但在软琼脂上锚着非依赖生长的能力加强。结论：建立了稳定表达外源EphA3基因的NIH3T3细胞株,EphA3基因稳定表达具有诱导正常NIH3T3细胞发生恶性转化的重要生物功能。     

A stably transfected c-myc cat hybrid gene is not regulated by serum in NIH3T3 cells

A plasmid containing the CAT (chloramphenicolacetyltransferase) gene fused to the 5' adjacent sequences and first exon of the human c-myc gene was stably transfected into NIH3T3 cells. Single cell clones were grown and CAT activity was measured after serum starvation and stimulation. CAT activity of the hybrid construct remained unchanged in serum-deprived and serum-stimulated cells. In contrast the steady-state RNA level of the endogenous mouse c-myc gene was strongly elevated upon serum stimulation. The bona fide usage of the human c-myc promoter P1/P2 in mouse cells carrying the hybrid gene was revealed by S1 analysis.     

Fate and biological activity of exogenous DNA sequences during serial transfections in NIH/3T3 cells

The efficiency and accuracy of serial transfections in NIH/3T3 fibroblasts were investigated with two plasmids carrying a dominant gene. One plasmid carried the activated ras oncogene of human origin inducing morphological alteration and the oncogenic phenotype of NIH/3T3 cells. The second plasmid carried the bacterial neoR gene conferring resistance to the neomycine analogue G 418. We observed no correlation between the presence of biologically active DNAs in primary transfectants and the capacities of these DNAs to transmit the exogenous information in a second cycle of transfection. Cellular DNA of only two of 13 ras and only 1 of 3 neoR transformants could transform NIH/3T3 in a second cycle of transfections. About half of secondary transfectants, derived from those primary transfectants which did transmit the exogenous DNA, contained apparently complete exogenous sequences and transmitted it efficiently and even with the original site of integration in the host DNA in a third cycle of transfection. Exogenous DNA sequences were amplified in the majority of secondary transfectants but did not enhance biological activity in a third cycle of transfer. The exogenous DNA was found to undergo rearrangements in oncogenic transformants propagated in cell culture.     

Reduced induction of c-fos but not of c-myc expressions in a nontumorigenic revertant R1 of Ej-ras-transformed NIH/3T3 cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA)

It has been reported that both c-fos and c-myc mRNAs are induced in NIH/3T3 cells after 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment. We have studied the effect of TPA on the expression of c-fos and c-myc in EJ-ras-transformed NIH/3T3 and its nontumorigenic flat revertant R1 cells. Although TPA treatment induces c-myc mRNA, as in the case of NIH/3T3 cells, the induced level of c-fos mRNA is greatly reduced not only in slow-growing EJ-ras-transformed NIH/3T3 but also in quiescent R1 cells. In addition, serum-induced c-fos expression is also reduced in EJ-ras-transformed NIH/3T3 and R1 cells. These observations suggest that the pathway from TPA to c-fos gene is different from that to c-myc gene and that the former pathway is down-regulated in association not with the transformed phenotype, but with EJ-ras expression, and it is possible that this reduced induction of c-fos is not specific to TPA.     

Transformation of NIH 3T3 cells by enhanced PAR expression

Prostate androgen regulated (PAR) is a 1038bp novel gene located on chromosome 1 in epidermal differentiation complex. The gene is ubiquitously expressed in normal tissues and is overexpressed in most of their malignant counterparts. PAR cellular function is unknown. Here we report the effect of increased PAR expression induced by transfection of PAR cDNA on NIH3T3 cell phenotype. PAR-NIH3T3 transfectants expressing 3- to 4-fold higher PAR levels compared to controls grew faster in tissue cultures, formed colonies in soft agar, and exhibited a shortening of G1 and S phases of cell cycle and formed tumors in SCID mice. Transfection of NIH3T3 cells with increased ectopic PAR expression with a 22 mer oligonucleotide in antisense orientation with PAR mRNA abrogated their ability to form colonies in soft agar. The data presented here along with our previously reported results on DU145 cells transfected with antisense PAR cDNA suggest that PAR gene behaves like a proto-oncogene.     

大鼠催乳素基因真核细胞可表达性质粒的构建及应用研究

７３５ｂｐ的ＰＲＬｃＤＮＡ片段从质粒ＰＲＬ－ＳＰ６５＃１中回收后,用粘性末端连接法将其重组到真核表达载体ｐｃＤＮＡ３上,筛选出正向连接重组体ｐｃＤＮＡ３－ＰＲＬＳ和反向连接重组体ｐｃＤＮＡ３－ＰＲＬＡＳ。将重组体ｐｃＤＮＡ３－ＰＲＬｓ和空载体ｐｃＤＮＡ３分别转入ＮＩＨ３Ｔ３细胞系,用Ｇ４１８筛选出阳性细胞后与未转染的ＮＩＨ３Ｔ３细胞在加Ｅ２和不加Ｅ２的情况下,用原位杂交的方法,分别用ＰＲＬｃＤＮＡ探针和原癌基因ｃ－Ｈ－ｒａｓｃＤＮＡ探针进行检测,未转染的ＮＩＨ３Ｔ３细胞在加Ｅ２和不加Ｅ２时都几乎无催乳素基因的表达,同样,转入空载体的ＮＩＨ３Ｔ３细胞也无ＰＲＬ的表达,而转入重组体ｐｃＤＮＡ３－ＰＲＬＳ的ＮＩＨ３Ｔ３细胞则有大量的ＰＲＬ基因的表达,与对照组相比有显著差异（Ｐ＜０．０１）。正常和转入空载体的ＮＩＨ３Ｔ３细胞有一定程度的原癌基因ｃ－Ｈ－ｒａｓ的表达,当分别加入Ｅ２和转入重组体ｐｃＤＮＡ３－ＰＲＬＳ后,ＮＩＨ３Ｔ３细胞中的ｃ－Ｈ－ｒａｓ基因表达水平都显著升高（Ｐ＜０．０５）。     

Human c-fgr induces a monocyte-specific enzyme in NIH 3T3 cells.

The mutant c-fgr protein (p58c-fgr/F523) containing Phe-523 instead of Tyr-523 exhibited transforming activity in NIH 3T3 cells like other protein-tyrosine kinases of the src family, but normal p58c-fgr (p58c-fgr/wt) did not. The mutant protein showed tyrosine kinase activity threefold higher than that of the normal protein in vitro. Surprisingly, transfection of the normal c-fgr gene into NIH 3T3 cells resulted in induction of sodium fluoride (NaF)-sensitive alpha-naphthyl butyrate esterase (alpha-NBE), a marker enzyme of cells of monocytic origin, which was not induced in v-src-, v-fgr-, or lyn-transfected NIH 3T3 cells. The NaF-sensitive alpha-NBE induced in c-fgr transfectants was shown by isoelectric focusing to have a pI of 5.2 to 5.4, a range which was the same as those for thioglycolate-induced murine peritoneal macrophages and 1 alpha,25-dihydroxyvitamin D3-treated WEHI-3B cells. Immunoblotting studies with antiphosphotyrosine antibodies revealed that 58-, 62-, 75-, 120-, 200-, and 230-kDa proteins were commonly phosphorylated at tyrosine residues in NIH 3T3 cells transfected with normal and mutated c-fgr, while 95-kDa protein was significantly phosphorylated at tyrosine residues in cells transfected with the mutated c-fgr. These findings suggest that tyrosine phosphorylation of specific cellular substrate proteins is important in induction of NaF-sensitive alpha-NBE and cell transformation by p58c-fgr.     

Image analysis of Feulgen-stained NIH/3T3 cells transformed with DNA of 4-nitroquinoline 1-oxide treated human breast epithelial cells.

The nuclear phenotypes of Feulgen-stained NIH/3T3 cells transformed with 4-nitroquinoline 1-oxide (4NQO) treated, human breast epithelial cell (HBEC) DNA were studied by scanning microspectrophotometry and image analysis and compared with data obtained for nontransformed cells and for NIH/3T3 cells under ras oncogene transfecting situations. The Feulgen-DNA content of the individual nuclei (NQ1, NQ2, and NQ3 phenotypes) of the transformed cells was found not to be deeply affected, although presence of chromatin structures resembling double minutes could be verified in part of the metaphases of the transformed cells. On the other hand, the chromatin supraorganization of these cells showed some changes involving increased (NQ2, NQ3) or decreased (NQ1) levels of condensation. The changes in chromatin packing states, however, were of small magnitude compared with those reported for NIH/3T3 cells transfected with a c-H-ras oncogene or an N-ras-containing MCF-7 cell DNA. It was assumed that the transformation of the NIH/3T3 cells is not always necessarily accompanied by high levels of chromatin condensation. The transformation of the NIH/3T3 cells induced by the 4NQO-treated HBEC DNA and particularly the changes in chromatin condensation in these transformed cells could not be attributed merely to a ras activation elicited by the carcinogen. It is suggested that a more complex transforming mechanism is involved, probably owing to the fact that a whole genomic DNA of the 4NQO-treated HBEC has been used for transfection.     

Use of a cloned multidrug resistance gene for coamplification and overproduction of major excreted protein, a transformation-regulated secreted acid protease.

Malignantly transformed mouse fibroblasts synthesize and secrete large amounts of major excreted protein (MEP), a 39,000-dalton precursor to an acid protease (cathepsin L). To evaluate the possible role of this protease in the transformed phenotype, we transfected cloned genes for mouse or human MEP into mouse NIH 3T3 cells with an expression vector for the dominant, selectable human multidrug resistance (MDR1) gene. The cotransfected MEP sequences were efficiently coamplified and transcribed during stepwise selection for multidrug resistance in colchicine. The transfected NIH 3T3 cell lines containing amplified MEP sequences synthesized as much MEP as did Kirsten sarcoma virus-transformed NIH 3T3 cells. The MEP synthesized by cells transfected with the cloned mouse and human MEP genes was also secreted. Elevated synthesis and secretion of MEP by NIH 3T3 cells did not change the nontransformed phenotype of these cells.     

Differential induction of cytolytic susceptibility by E1A, myc, and ras oncogenes in immortalized cells.

The E1A oncogene of adenovirus serotypes 2 and 5 induces susceptibility to the cytolytic effects of natural killer lymphocytes and activated macrophages when expressed in infected and transformed mammalian cells (cytolysis-susceptible phenotype). E1A and the oncogenes v-myc, long-terminal-repeat-promoted c-myc, and activated c-ras share the ability to immortalize transfected low-passage rodent cells. The cytolytic phenotypes of well-characterized rodent cell lines immortalized by these three oncogenes were defined. In contrast to target cells expressing the intact E1A gene, myc- and ras-expressing, immortalized primary transfectants were resistant to lysis by both types of killer cell populations. The same patterns of susceptibility (E1A) and resistance (myc and ras) to cytolysis were observed in oncogene-transfected continuous rat (REF52) and mouse (NIH 3T3) cell lines, indicating that differences in the cytolytic phenotypes associated with expression of these oncogenes are not due to cell selection during immortalization. The results suggest that the E1A oncogene may possess a functional domain that is different from those of other oncogenes, such as myc and ras, and that the activity linked to this postulated domain is dissociable from the process of immortalization.     

STK15的表达对NIH3T3细胞的影响

目的构建pcDNA3.1-STK15表达质粒,探讨STK15基因对小鼠成纤维细胞（NIH3T3）的影响。方法构建pcDNA3.1-STK15质粒,将其转染NIH3T3,应用RT-PCR、免疫细胞化学和Western印迹方法检测STK15的表达;MTT法检测细胞增殖能力;Transwell检测细胞侵袭能力。结果转染pcDNA3.1-STK15质粒的NIH3T3细胞在48 h有STK15的表达,而且该细胞的增殖速度和穿透Matrigel胶的细胞数均明显高于对照组（P〈0.05）。结论STK15基因具有增加细胞增殖和细胞侵袭力的功能,进而形成肿瘤。     

Drug-sensitivity pattern analysis for study of functional relationship between gene products

We have developed a method that we call 'drug-sensitivity pattern analysis', or DSPA, for analysis of protein function. Cells are transfected with cDNA of the test molecule, followed by analysis of the sensitivity of the transfected cells to multiple growth-inhibitory drugs. If two cDNA products have similar functions, their transfected cells should show similar drug-sensitivity patterns. The cDNAs of some signaling molecules were transfected into NIH3T3 or Ha-ras-transformed NIH3T3 (ras-NIH) cells and stable transfectants, which expressed high amounts of the gene product, were isolated. Chemosensitivity of the transfected clone was compared with the parental cells by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide method using more than 40 drugs. The chemosensitivity changes caused by the transfected gene were calculated and expressed numerically as 'drug chemosensitivity index' (DCI). When the DCI values were analyzed by regression analysis, a significant positive relationship between IkappaBalpha superrepressor and dominant-negative IKKbeta and an inverse relationship between p53 and Mdm2 were consistent with previous reports. Thus, the DSPA method is useful for identifying functional similarities between gene products.     

An optimum dose of c-H-ras is a prerequisite for hormone-dependent conversion of a cell between cancerous and normal states in tissue culture.

We have established a few cell lines which can be reversibly converted from cancerous to normal and vice versa by the addition to, or removal from the culture medium of glucocorticoid hormone. These cell lines were derived from mouse NIH 3T3 cells and possessed the integrated gene pairs on chromosomes, which are composed of human mutated c-H-ras fused with mouse mammary tumour virus long terminal repeat and E. coli xanthine-guanine phosphoribosyltransferase gene with the SV40 promoter. We have characterised these cell lines in order to elucidate an essential requirement for the conversion of the state of a cell. It was found that the presence of at least two to three copies of the gene pair per diploid genome are essential. An approximate threshold level of c-H-ras 1.6 kb RNA required for reversible conversion was estimated.     

Involvement of somatically acquired ecotropic viruses in the immunogenicity of nude-transplanted NIH/3T3 transformed cell lines.

Immunogenic tumor variants were previously derived after transplantation in vivo into nude mice of NIH/3T3-transformed cell lines. Nude-passaged cell lines were rejected by immunocompetent H-2q NIH mice, were recognized by specific CTL clones, and expressed new retroviral Ag. The aim of the present work was to investigate whether somatically acquired proviral sequences were present in the genome of nude-passaged cells and to test directly for a causative relationship between murine leukemia virus (MuLV) expression and immunogenicity. Southern blot analysis of PstI-digested DNA indicated that in contrast to the parental NIH/3T3 transformed cell lines (pT, T12N/5a, NS-1) all the nude-passaged immunogenic variants (pT-nude, T12N/5a-nude, NS-1-nude) contained newly acquired ecotropic-related proviruses. Immediately after in vitro establishment, these tumors displayed multiple integration sites as assessed by analysis of 3' proviral-cellular junctions. Long term in vitro culture of one of the cell lines (pT-nude) resulted in a cell line (pT-nude/vitro) that was clonal or oligo-clonal with respect to viral integration. Northern blot analysis established that the new proviruses were actively transcribed in all the immunogenic variants. To assess whether the somatically acquired ecotropic proviral sequences encode for target structures recognized by specific CTL, obtained after immunization of NIH mice with pT-nude, the parental cell line pT was transfected with plasmids containing the entire AKV MuLV genome, the cloned AKV gag or env genes. Screening of transfectants for their ability to stimulate the production of TNF by anti-pT-nude effectors indicated that cells transfected with the entire ecotropic virus or with MuLV-env gene products could be recognized by an NIH anti-pT-nude CTL line and NIH anti-pT-nude Kq-restricted CTL clones as well as the immunizing target pT-nude.     

Differential methylation of the c-H-ras gene in normal mouse cells and during skin tumour progression.

We have previously shown that the mouse c-H-ras gene acquires transforming activity in chemically induced skin tumours. We have now investigated the pattern of DNA methylation at HpaII and XhoI sites around the c-H-ras locus in various tissues and stages of epidermal tumour progression. The results of this study suggest a correlation between the methylation state of the c-H-ras gene and its susceptibility to oncogenic conversion by a point-mutation. The locus is substantially undermethylated in normal epidermis in comparison with NIH/3T3 fibroblasts. Intermediate levels of methylation were observed in the other tissues investigated. The undermethylation at HpaII sites in epidermal DNA persists through the morphologically distinct phases of hyperplasia, benign papilloma and malignant carcinoma. Methylation at a specific XhoI site close to the c-H-ras gene is significantly reduced with respect to normal epidermis in some, but not all epidermal tumours. The methylation state of the c-H-ras locus in specific tumours is stably maintained following transfection of these DNAs into NIH/3T3 cells and selection of transformed foci. Demethylation of the locus is not essential in vitro for the transforming activity of DNA from epidermal tumours. The significance of changes in the methylation pattern of the c-H-ras gene in different tissues and during tumour progression is discussed.     

Effect of transfection with a gene coding for the fibronectin FNIII/10 fragment upon contact inhibition of C3H10T1/2 fibroblasts

The density-dependent growth inhibition of non-transformed cells may be associated with inefficient transduction of the proliferative signal from cell adhesion molecules. To verify this concept, the C3H10T1/2 fibroblasts were stably transfected with the gene coding for the fibronectin fragment III/10 (FNIII/10). This resulted in differences in gene's expression between original C3H10T1/2 cells and their FNIII/10 transfectants. No significant differences in growth properties were observed in the original or in the transfected cells. C3H10T1/2 cells and their transfectants, when co-cultured, displayed more cells at confluence than the cells cultured alone. Moreover, co-cultured C3H10T1/2 cells and their transfectants showed elevated levels of phospho-ERK1/2 compared to homogenous cultures. Results obtained indicate that cellular homogeneity is responsible for density-dependent growth inhibition.     

稳定表达小鼠CD40L的NIH3T3细胞系的建立及其在B细胞培养和激活中的应用

该研究构建小鼠CD40L真核表达重组质粒pcDNA3.1-mCD40L,通过电转法将重组质粒转至NIH3T3细胞中。利用G418对转染后细胞进行压力筛选,获得稳定转染细胞株。提取稳定转染细胞株RNA,通过RT-PCR法检测Neo基因的mRNA表达情况。分离稳定转染细胞上清,利用ELISA法检测小鼠CD40L蛋白水平的表达情况。RT-PCR结果显示,Neo基因能够在稳定转染细胞中表达,ELISA结果显示,获得的稳定转染细胞株NIH3T3-mCD40L细胞上清中CD40L的表达量高达1.286 ng/mL。进一步活性研究表明,该细胞系能够在体外与IL-2和IL-21共同作用培养B细胞至14天,并刺激B细胞产生特异性抗体。该细胞系的成功构建,为利用体外B细胞分离培养和活化法分离特异性单克隆抗体奠定了良好的基础。     

人sTNFR1基因的克隆以及在NIH3T3细胞中的稳定表达

以He1a细胞的总RNA为模板,用RT—PCR方法扩增sTNFR1全编码区基因片段,构建含有目的片段的T载体克隆及真核表达载体pcDNA3．1（-）重组质粒亚克隆,将重组质粒和脂质体共同转染NIH3T3细胞系,G418筛选稳定转染细胞株．经核苷酸序列测序和酶切鉴定,成功构建了pcDNA3．1（-）-sTNFR1真核表达质粒,脂质体法建立了高效表达sTNFRI的稳定转染细胞系,并经RT—PCR和Western Blotting鉴定．人sTNFR1基因能在NIH3T3细胞系中稳定表达,为今后的研究打下了基础．     

Secretion of apolipoprotein A-I in lipoprotein particles following transfection of the human apolipoprotein A-I gene into 3T3 cells

Apolipoprotein A-I (apoA-I) is the major protein constituent of plasma high density lipoproteins (HDL). To examine apoA-I processing and secretion, the human apoA-I gene (2.2-kilobase PstI-PstI fragment) linked to the mouse metallothionein promoter was transfected by electroporation into NIH 3T3 fibroblasts along with the plasmid pSV2 neo, which confers neomycin resistance. Transfected cells were selected for neomycin resistance and screened for the ability to produce apoA-I by enzyme-linked immunosorbent assay. In the absence of lipids in the medium, selected 3T3 cells secreted apoA-I, mainly in the proprotein form, at density greater than 1.25 g/ml. Following incubation of cells with lipids, and subsequent washing with lipid-free medium, apoA-I was recovered in the HDL region (1.063-1.21 g/ml) as well as in the 1.21 g/ml infranatant. Examination of the HDL fraction by electron microscopy revealed round particles, 10-21 nm in diameter. These data indicate that human apoA-I secreted by transfected 3T3 fibroblasts can assemble into lipoprotein particles under the appropriate conditions.     

pcDNA3.1/myc-His-DJ-1^M26I重组载体构建及其对NIH3T3细胞增殖和凋亡研究

目的构建pcDNA3.1/myc-His-DJ-1和pcDNA3.1/myc-His-DJ-1M26I重组表达载体,为研究DJ-1M26I突变与细胞增殖、凋亡的关系及建立转基因动物模型奠定基础。方法采用突变试剂盒将DJ-1蛋白第26位氨基酸进行突变,分别构建pcDNA3.1/myc-His-DJ-1和pcDNA3.1/myc-His-DJ-1M26I重组表达载体,并采用脂质体介导的方法分别将其转染入NIH3T3细胞,500μg/mL G418压力筛选稳定克隆,对2种转染细胞在DNA水平、RNA水平和蛋白质水平进行鉴定,采用MTT染色方法和AnnexinV-FITC试剂盒进行转染阳性克隆细胞的细胞活力与细胞凋亡检测。结果 pcDNA3.1/myc-His-DJ-1和pcDNA3.1/myc-His-DJ-1M26I重组质粒转染NIH3T3细胞经G418筛选后,PCR方法检测分别获得1个和3个阳性细胞克隆,RT-PCR及western blot方法进行DJ-1-His基因表达检测,结果均证明外源插入基因的表达,MTT实验结果初步证明转染DJ-1M26I基因的NIH3T3阳性细胞组细胞增殖速率低于正常NIH3T3细胞组（P〈0.05）,转染DJ-1基因的NIH3T3阳性细胞组细胞增殖速率与正常NIH3T3细胞相比无明显差别;细胞凋亡检测表明转染DJ-1M26I基因的NIH3T3阳性细胞组细胞凋亡率高于正常NIH3T3细胞,转染DJ-1基因的NIH3T3阳性细胞组细胞凋亡率低于正常NIH3T3细胞（P〈0.05）。结论成功构建pcDNA3.1/myc-His-DJ-1和pcDNA3.1/myc-His-DJ-1 M26I重组表达载体,成功筛选出稳定表达人DJ-1及DJ-1 M26I的NIH3T3细胞。DJ-1 M26I基因突变更易导致NIH3T3细胞的凋亡。