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Results for “amplification”

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PubMed1985

Selective DNA-amplification induced by carcinogens (initiators): evidence for a role of proteases and DNA polymerase alpha.

Inhibitors of DNA polymerase alpha (aphidicolin, phosphonoacetic acid, phosphonoformic acid) efficiently inhibit initiator-induced amplification of SV40 DNA sequences in the SV40-transformed Chinese hamster cell line CO631. Amplification is also inhibited by various protease inhibitors (antipain, leupeptin, aprotinin, alpha-I-antitrypsin, epsilon-amino-caproic acid, soy-bean protease inhibitor), by the non-initiating but DNA-damaging agent caffeine, and by sodium butyrate, which inhibits DNA synthesis by histone modification. In contrast, an inhibitor of topoisomerase II, nalidixic acid, enhances amplification when applied simultaneously with initiating treatment. This latter compound does not induce amplification when applied without initiator. Cycloheximide induces DNA amplification in the same way as chemical and physical carcinogens. This amplification can still be observed when protein synthesis is completely blocked. The data suggest a complex mechanism of selective DNA amplification. The possible involvement of proteases leading to a functional modification of DNA polymerase alpha is discussed.

Animals↗

PubMed1992

c-myc amplification is an independent prognostic factor in postmenopausal breast cancer.

The c-myc proto-oncogene was analyzed in 311 cases of primary breast cancer, in 8% of which it was found to be amplified, usually at moderately increased copy number (2-5 copies). The adjacent pvt gene was co-amplified with c-myc in all tumors analyzed. C-myc amplification was significantly correlated to a high S-phase fraction and to amplification of the c-erbB-2 proto-oncogene. Weak relationships were found between c-myc amplification and the presence of lymph-node metastasis, advanced stage, DNA non-diploidy and premenopausal status, but not tumor size, estrogen receptor or progesterone receptor status, or int-2 amplification. C-myc amplification, and especially a high gene copy number (greater than 5 copies), was significantly related to early recurrence and death in breast cancer, a relationship seen in both the lymph-node-negative and node-positive subcategories. A particularly strong correlation with poor clinical outcome was seen in postmenopausal patients (p greater than 0.0005), an association which persisted in multivariate survival analysis. We conclude that the activation of c-myc is indeed associated with rapidly growing and progressive breast cancer. Gene amplification, on the other hand, is relatively infrequent and occurs mostly at low copy number, implying that tumors are heterogeneous with respect to cell clones harboring c-myc amplification. An immunohistochemical assessment would more accurately illustrate the importance of c-myc activation in human breast cancer. However, the obvious instability of the c-myc transcript and translate suggests that c-myc is not a suitable prognostic marker for routine purposes.

Adult↗

PubMed1993

Amplification of fgfr4 gene in human breast and gynecological cancers.

We have investigated gene amplification of fibroblast growth factor receptor-4 (FGFR4) gene in 30 primary breast tumor samples and 15 gynecological tumor samples. Ten percent of the breast tumors showed 2- to 4-fold amplification. Amplification was found more frequently in estrogen- and progesterone-receptor-positive tumors and in tumors with high lymph-node involvement. Breast tumor samples were also analyzed for the amplification of fgfr3 and erbB2 genes and the chromosome 11q13 located genes hst1/int2/bcl1/sea. erbB2 gene was amplified 2- to 13-fold in 13% of the cases, but no amplification of int2/hst1/bcl1/sea amplicon was found. Gynecological tumors were also analyzed for the amplification of fgfr4 and fgfr3 genes and for int2 and hst1 oncogenes. Eleven of the 15 gynecological tumors were ovarian neoplasms including 2 benign tumors; the remainder comprised 1 ovarian metastasis of breast cancer; 1 endometrial cancer; 1 uterine leiomyosarcoma and 1 carcinosarcoma of the fallopian tube. In gynecological tumors, fgfr4 gene was found to be amplified in 2 ovarian tumors. Amplification of hst1 was found in 1 benign ovarian tumor. Thus, the fgfr4 gene may be involved in breast and ovarian tumorigenesis.

Adult↗

PubMed1995

Concurrent amplification of cyclin E and CDK2 genes in colorectal carcinomas.

The genetic changes of cyclin A, DI, E and CDK2 were examined in human colorectal carcinomas by Southern-blot analysis. Gene amplification of cyclin E was detected in 5 of 53 (9.4%) primary colorectal carcinoma tissues. Interestingly, in 3 of 5 tumors showing cyclin E gene amplification, the CDK2 gene was amplified simultaneously with rearrangements. No obvious correlation was detected between gene amplification and clinicopathological features of colorectal carcinomas. Out of 7 colon carcinoma cell lines, 2 showed gene amplification of cyclin E without gene amplification of CDK2. No amplification of cyclin A or DI gene was found in any of the colorectal carcinoma tissues or colon carcinoma cell lines. Our results suggest that the concurrent amplification of cyclin E and CDK2 genes may play a role in colorectal carcinogenesis.

Aged↗

PubMed1987

Amplification of the X-linked Drosophila chorion gene cluster requires a region upstream from the s38 chorion gene.

Genomic sequences controlling follicle cell-specific amplification of the X-linked Drosophila chorion gene cluster were mapped by P element-mediated transformation. Several DNA fragments containing the s38 gene and flanking sequences induced tissue-specific amplification, although replication levels were subject to position effects. Deletion analysis identified a 467-bp region upstream from the s38 transcription start site that contained sequences essential in cis for amplification. The essential region shared 32 bp of imperfect sequence homology with a previously identified region necessary for third chromosome chorion gene cluster amplification. This homologous segment contained a repetitive motif consisting of perfect and imperfect AATAC repeats; it was localized near the boundary of the essential domain since most, but not all, the repeats could be deleted without eliminating transposon-induced amplification. The repetitive region was not required for developmentally regulated s38 transcription, therefore our results identified at least one element required for amplification but not for chorion gene transcription. The homologous repetitive sequences within the amplification-essential regions may constitute part of the replication origins used to differentially replicate the two chorion domains during oogenesis.

Animals↗

PubMed1989

Amplification enhancers and replication origins in the autosomal chorion gene cluster of Drosophila.

Drosophila melanogaster follicle cells over-replicate the chromosomal domain containing the third chromosome chorion gene cluster. Multiple regions of this cluster are needed in cis for attainment of high levels of amplification. We have confirmed the importance of the proposed amplification control element (ACE3) and demonstrated that it can support low levels of follicular amplification in the absence of other elements, but that it lacks detectable activity as a DNA replication origin. We have also demonstrated the existence of additional amplification-enhancing regions (AERs), by analyzing the amplification levels of a series of in situ induced, nested deletions of the chorion cluster. These deletions were induced by P-transposase perturbation of a chorion transposon in a highly amplifying transformed line, and were not accompanied by re-transposition, making possible a quantitative analysis of amplification levels in the absence of chromosomal position effects. Analysis of endogenous replication intermediates in wild-type follicular DNA suggested that at least one of the AERs may be an origin of replication and that amplification uses at least one additional replication origin.

Animals↗

PubMed1990

Oncogene amplification correlates with dense lymphocyte infiltration in human breast cancers: a role for hematopoietic growth factor release by tumor cells?

One hundred six primary breast cancer samples were analysed for c-erbB2, int-2, and c-myc gene amplification. Surgically confirmed nodal involvement was observed in 42%. Level of gene amplification was studied by Southern and/or slot blot techniques. Amplified c-erbB2 gene sequences were present in 21.5% of all samples. Int-2 was amplified in 13.1% and c-myc was amplified in 10.3%. In a non-parametric test (Kruskal-Wallis) a strong negative association was found between high levels of c-erbB2 amplification and absence of estrogen receptor (ER) (P = .0009) or progesterone receptor (PR) (P = .011) expression. No correlations were found between all or high levels of amplification of each oncogene separately or combined with T, N, grade, multifocality of tumor, or associated carcinoma in situ. There was a trend approaching statistical significance for patients with c-erbB2 amplifications to have positive lymph nodes at surgery (P = 0.09). A somewhat surprising finding however was a very strong association between oncogene amplification and dense lymphocyte infiltration of the tumor (P = .05). This correlation is even stronger when only high levels of amplification are considered, either for each oncogene separately (P = .0048) or in combination (P = .0007). We propose that malignant cell cytokine production may help explain this observation.

Breast Neoplasms↗

PubMed2004

Evaluation of MDM2 and CDK4 amplification by real-time PCR on paraffin wax-embedded material: a potential tool for the diagnosis of atypical lipomatous tumours/well-differentiated liposarcomas.

Atypical lipomatous tumours/well-differentiated liposarcomas and dedifferentiated liposarcomas are characterized by 12q13-15 region amplification. In contrast, this molecular event has not been reported in benign lipomas. Within the 12q13-15 chromosomal region, the MDM2, SAS, HMGA2, and CDK4 genes are the most frequent targets of amplification. A series of lipomas (36 cases) and liposarcomas (48 cases) was analysed for MDM2 and CDK4 gene amplification by real-time PCR. MDM2 and CDK4 gene amplification was detected in 2.8% and 5.6% of lipomas and 98.2% and 82.4% of liposarcomas, respectively. Moreover, co-amplification of the two genes as well as a higher-level amplification was observed more frequently in dedifferentiated liposarcomas than in atypical lipomatous tumours/well-differentiated liposarcomas. Real-time PCR proved to be a fast and reliable method to characterize lipomas and liposarcomas by quantification of MDM2 and CDK4 gene amplification. It is applicable to paraffin wax-embedded tissues and could be useful when histological diagnosis is difficult.

Abdominal Neoplasms↗

PubMed1994

Specific A+T-rich repetitive DNA sequences in maxicircles from wildtype Leishmania mexicana amazonensis and variants with DNA amplification.

To explain the low cross-hybridization between kinetoplast DNA maxicircles of Leishmania parasites that show DNA amplification and those of parasites without DNA amplification, we isolated and cloned two maxicircle fragments, one specific to each group of parasites. The cloned fragment from wildtype L. m. amazonensis (MbpW94) and that from an arsenite-resistant variant with DNA amplification (MpbA29) hybridized only to maxicircles from parasites of the group from which the fragment was originally derived. Both fragments were A+T-rich, tandemly repeated, and lacked long conserved open reading frames and transcriptional products. MpbW94 (685 bp) was harbored in a segment of roughly 12 kb in maxicircles of wildtype parasites and of an arsenite-resistant variant without DNA amplification, while MbpA29 (1121 bp) occupied a 6- to 7-kb segment of maxicircle DNA in arsenite- and tunicamycin-resistant variants with DNA amplification. These maxicircle DNA segments appear to resemble previously described maxicircle divergent regions of other kinetoplastids. The presence of these specific sequences allows differentiation between maxicircles of drug-resistant L. m. amazonensis with DNA amplification and those of parasites without DNA amplification and helps explain the low cross-hybridization between maxicircles of the two parasite groups. Furthermore, these sequences allow the study of the kinetics of the changeover of A+T-rich regions of maxicircles during the transition period from one maxicircle type to the other.

Animals↗

PubMed1998

Amplification of DNA sequences from chromosome 19q13.1 in human pancreatic cell lines.

Conventional cytogenetics and comparative genomic hybridization (CGH) were utilized to identify recurrent chromosomal imbalances in 12 pancreatic adenocarcinoma cell lines. Multiple deletions and gains were observed in all cell lines. Losses affecting chromosomes or chromosome arms 9p, 13, 18q, 8p, 4, and 10p and gains involving chromosome arms or bands 19q13.1, 20q, 5p, 7p, 11q, 3q25-qter, 8q24, and 10q were commonly observed. Interestingly, 19 distinct sites of high-level amplification were found by CGH. Recurrent sites involved 19q13.1 (6 cases), 5p (3 cases), and 12p and 16p (2 cases). Amplification of KRAS2 was demonstrated in 2 cell lines and that of ERBB2 in another. To define the occurrence of chromosome 19 amplification further, two-dimensional analysis of NotI genomic restriction digests and fluorescence in situ hybridization using probes from band 19q13.1 were utilized. High-level amplification of overlapping sets of chromosome 19 NotI fragments was exhibited in 3 cell lines of which 2 showed amplification of both OZF and AKT2 genes and 1 that of AKT2 alone. In these 3 cell lines, amplification of chromosome 19 sequences was associated with the presence of a homogeneously staining region. Our results provide evidence of heterogeneity in the extent of chromosome 19 amplification and suggest the existence of yet unknown amplified genes that may play a role in pancreatic carcinogenesis.

Chromosome Aberrations↗

PubMed1995

Gene amplifications in advanced-stage human prostate cancer.

Gene amplification is a model of proto-oncogene alterations occasionally observed in human tumors. This amplification can, in some cases, have prognostic value (N-myc in neuroblastoma, c-erbB2 and int-2 in breast cancer, etc.). Amplifications of the proto-oncogenes c-myc, c-erbB2 and int-2 have not yet been report in prostate adenocarcinoma, which, like breast cancer, is hormone dependent. We sought amplifications of these three proto-oncogenes by means of Southern blotting in 15 human prostate adenocarcinoma specimens, most of which were advanced (7 stage C and 6 stage D1 or D2). We confirmed the lack of c-myc and c-erbB2 amplification, regardless of the stage, in contrast to the case of breast cancer. Int-2 amplification was observed in one advanced tumor with bone metastases, out of a total of six stage D tumors. The precise frequency of int-2 amplification and its role in prostate carcinogenesis remain to be determined.

Adenocarcinoma↗

PubMed1992

Frequent amplification of the c-met gene in scirrhous type stomach cancer.

Amplification of the c-met gene, that encodes hepatocyte growth factor receptor, was examined on human esophageal, gastric and colorectal carcinomas. Six (55%) of the 11 gastric carcinoma cell lines and 15 (23%) of the 64 advanced gastric carcinomas showed the c-met gene amplification. Among them, c-met amplification was detected in 5 gastric cancer cell lines, derived from scirrhous gastric carcinoma and in 5 (38%) of 13 scirrhous gastric carcinoma tissues. Furthermore, patients of gastric carcinoma with c-met amplification showed significantly advanced tumor stage and poorer prognosis than those without the amplification. Conversely, no amplification was detected in any of the esophageal and colorectal carcinoma cell lines as well as carcinoma tissues except one colonic carcinoma. These results overall suggest that amplification of the c-met gene might participate in carcinogenesis and progression of stomach cancer, especially scirrhous type stomach carcinoma.

Adenocarcinoma, Scirrhous↗

PubMed1987

Amplification of a chorion gene cluster in Drosophila is subject to multiple cis-regulatory elements and to long-range position effects.

We have used P-element transformation to study cis-acting elements involved in the control of amplification of the third chromosome chorion gene cluster (66D12-15) in Drosophila melanogaster. To reduce position effects large fragments (5.7 to 12 kb; kb = 10(3) bases) of chorion DNA and the 7.2 kb ry+ fragment were used to "buffer" these putative elements from sequences at the insertion site. Nevertheless, even the longest constructs were profoundly affected by the insertion sites and showed amplification levels ranging from undetectable to higher than in the endogenous locus. Any amplification was tissue and temporally correct and extended into the neighboring ry+ sequences. Analysis of amplification levels at various points along two constructs bearing the same 10 kb chorion insert in opposite orientations showed maximal levels occurring at one end of the chorion fragment, irrespective of whether that end was buffered at the middle of the transposon or exposed close to the insertion site. The maximally amplifying region encompasses the amplification control element (ACE), which has been shown to be necessary for amplification, in agreement with its putative role as a replication origin. We have additionally identified amplification-enhancing elements present elsewhere in the 10 kb chorion fragment, which are needed for attainment of high copy number. These elements, distinct from the ACE, have been only coarsely localized within two 2.25 to 2.3 kb regions. Some interesting sequence similarities between these two regions and the ACE element are pointed out.

Animals↗

PubMed1990

c-myc amplification in ovarian cancer.

The c-myc oncogene codes for a DNA binding protein that appears to play an important role in the regulation of cell growth. c-myc gene amplification has been documented to occur in both hematopoietic and solid neoplasms and often indicates more biologically aggressive tumors. Southern hybridization analysis was performed on high-molecular-weight DNA isolated from primary ovarian carcinomas. Major structural rearrangements of c-myc were not detected. Five of seventeen (29.4%) tumor samples demonstrated amplification of the myc oncogene. The 5 patients with ovarian carcinomas associated with c-myc amplification exhibited a median survival of 17 months. Of the 12 patients without evidence of tumor-associated c-myc amplification, 5 have exhibited disease-free survival for an average of 36.8 months and are currently alive. The remaining 7 patients, the majority of whom had advanced-stage, poorly differentiated lesions with a normal c-myc copy number, exhibited a median survival of 9 months. There was no apparent relationship between c-myc amplification, grade of tumor differentiation, and response to platinol-based chemotherapy. These data do not suggest a prognostic role for c-myc amplification in primary ovarian cancer. However, c-myc amplification is a common finding in advanced-stage ovarian cancer.

Adult↗

PubMed1992

Regularities of karyotypic evolution during stepwise amplification of genes determining drug resistance.

Analysis of chromosomal alterations during stepwise development of mdr1, dhfr, or CAD gene amplifications in a large number of independently selected Djungarian hamster DM-15 and murine P388 sublines revealed typical patterns of karyotypic evolution, specific for multiplication of each of these genes in each cell type. Some principal similarities of karyotypic evolution were noted in at least two different systems. They include: (i) appearance at the first selection step of a new chromosomal arm bearing the resident gene copy followed at the next selection steps by the formation in these specific chromosomal arms of amplified DNA tandem arrays; (ii) translocations of amplified DNA from its initial site to other, also non-random, chromosomal sites; and (iii) emergence in the cell variants with high degrees of gene amplification of multiple extra-chromosomal elements. The most prominent distinctions among the systems were as follows: (i) different structures, evidently containing amplified DNAs, appeared at the initial steps of amplification of different genes--additional heterogeneously staining regions in specific chromosomal segments in the case of amplification of dhfr or CAD genes in DM-15 cells, and mini-chromosomes in the case of mdr1 gene amplification in both DM-15 and P380 cells; (ii) distinct patterns of location of the amplified mdr1 gene copies are characteristic of Djungarian hamster DM-15 and murine P388 cell derivatives after subsequent steps of selection--at the site of resident gene localization or in some other, also non-random, chromosomal sites in DM-15 sublines, and predominantly extra-chromosomal in P388 sublines. We propose that different mechanisms are responsible for the initial steps of amplification of dhfr and CAD genes on the one hand and the mdr1 gene on the other: non-equal sister-chromatid exchanges and autonomous replication of the extra-chromosomal elements. It seems, however, that both mechanisms may be involved in further rounds of amplification of each of these three genes.

Animals↗

PubMed1992

Gene amplification in the murine SEWA system.

Considerable work with DNA amplification has been carried out in the murine SEWA ascites tumor cell system. In SEWA cells there is 'spontaneous' amplification of the c-myc oncogene, and transitions between different cytogenetic expressions of gene amplification such as DM (double minutes), CM (C-bandless chromosomes) and HSR (homogeneously staining regions) of the amplified DNA have been recorded during serial in vivo transplantations. In SEWA cells it has also been shown that the c-myc-containing DM will he lost under in vitro conditions, but are rapidly recovered if the cells are reinjected into animals. Additional gene amplification has been superimposed on the c-myc amplification in SEWA cells by stepwise selection in vitro, leading to resistance to different drugs, such as methotrexate, actinomycin D, colcemid and vincristine. Cytogenetically, DNA amplification is multifaceted and, in addition to the structures mentioned, it may also take the form of CB (chromatin bodies), which have been shown to be the carriers of resistance genes in hybrids between multidrug-resistant SEWA cells and Chinese hamster CHO cells. In most instances, DM are noncentromeric and distributed by a 'hitch-hiking' mechanism at mitosis; in one colcemid-resistant SEWA line, however, we have shown that the DM carry active centromeres. The molecular mechanism behind DNA amplification appears to be complex. We have shown that in four independently derived multidrug-resistant SEWA sublines the amplicons resided on circular molecules which were about 2500 kb long and carried at least five genes, including the three mouse mdr genes. Within the circles the DNA was unrearranged compared to the organization of the DNA in sensitive cells.

Animals↗

PubMed1990

Cathepsin D assay in primary breast cancer and lymph nodes: relationship with c-myc, c-erb-B-2 and int-2 oncogene amplification and node invasiveness.

In breast cancer, axillary lymph node invasiveness is the major prognostic factor in predicting relapse and metastasis. Nevertheless, since 30% of node-negative tumors also relapse, it is necessary to develop other independent prognostic factors. Oncogene amplification and the level of cathepsin D (cath-D), an acidic lysosomal protease produced and secreted in excess by breast cancer cells, have been proposed as additional prognostic factors. We have compared the cytosolic cath-D level and the amplification of three oncogenes: c-myc, neu-erb-B-2 and int-2 in 140 primary breast carcinomas and 64 axillary lymph nodes collected in 1987 and 1988 at the Cancer Center of Montpellier (Centre Paul Lamarque). None of the patients had previously received hormonal or chemotherapy. The cath-D concentration was measured with an immunoradiometric assay using monoclonal antibodies. DNA purified from the same samples was analyzed by a standard Southern blotting technique to estimate oncogene amplification. No correlation was found between the level of cath-D in the tumor and node invasiveness. Using a cut-off level of 60 pmol/mg protein, the status of cath-D was not correlated with neu-erb-B-2 and int-2 amplification and only correlated with c-myc amplification (P = 0.011). Both c-myc and cath-D are associated with cell proliferation, induced by estrogens in ER+ breast cancer, and constitutively produced in ER- breast cancer. The level of cath-D was significantly higher in the invaded lymph nodes (P = 0.04) than in the histologically non-invaded ones. Nevertheless, some non-invaded lymph nodes contained a high level of cath-D, as confirmed by immunoperoxidase staining. In conclusion, in breast cancer, a high cytosolic cath-D concentration is more frequent in tumors with c-myc amplification but is dissociated from neu-erb-B-2 or int-2 amplification, suggesting that the determination of these three markers will have an additional prognostic value.

Axilla↗

PubMed1992

Association between chromosome 11q13 amplification and prognosis of patients with oesophageal carcinomas.

Ninety pairs of normal and tumour tissue DNAs were isolated from paraffin-embedded blocks of advanced oesophageal carcinoma cases and examined for gene amplification at chromosome 11q13 by dot-blot hybridisation using the int-2 gene as a probe. 22 of 90 carcinomas (24%) showed more than two times amplification. Although no significant correlation was observed between gene amplification and histological type or metastasis to lymph node, a tendency for deeper invasion to be associated with more frequent amplification was observed. In relation to prognosis, patients with amplification had a lower survival rate than those without amplification. This tendency was evident both in the group with well differentiated type carcinoma and in the group which had no metastasis to lymph node. Thus, gene amplification of the int-2 locus may be a useful prognostic factor.

Chromosomes, Human, Pair 11↗