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N C Popescu

Publications and source records attributed to N C Popescu.

At least 109 records · Page 6Linked to original sources
PubMed1990

HSV-2-induced tumorigenicity in HPV16-immortalized human genital keratinocytes.

A subgenomic region of HSV-2, BglII N, is capable of converting immortal genital epithelial cells containing integrated HPV16 sequences into tumorigenic squamous cell carcinoma cells. Moreover, tumor-derived cultured cells and immortal cells that had been transfected with HSV-2/Bg/II N and kept in continuous culture subsequently lost the HSV-2 sequences. The HSV-2/Bg/II N sequence was ineffective on normal cells. Thus, HSV-2/Bg/II N may act as a cofactor in the genesis of a carcinoma but is not required to maintain the transformed phenotype. Although papillomaviruses (HPVs) are currently receiving much attention because of their association with cervical squamous carcinomas, ample reasons exist to suggest a multifactorial etiology in which additional factors are necessary to convert dysplastic lesions to carcinomas. The hypothesis that specific HPV types may be necessary but not sufficient to cause cancer is reinforced. Thus, HSV-2-transforming sequences have a potential role in the etiology of human cervical cancer.

Carcinoma, Squamous Cell↗
PubMed1990

A cluster of hematopoietic serine protease genes is found on the same chromosomal band as the human alpha/delta T-cell receptor locus.

The chymotrypsin-like family of serine protease genes includes several members that are expressed exclusively in subsets of hematopoietic cells. For example, human neutrophil elastase and cathepsin G are expressed only in myelomonocytic precursors, and cytotoxic-T-cell serine proteases are found only in cytotoxic lymphocytes. We have used a cathepsin G cDNA probe to clone two cathepsin G-like genes (designated CGL-1 and CGL-2) from a human genomic library. We have determined that CGL-1 is identical to a previously identified gene (known as CCPI, CTLA I, or cytotoxic serine protease B) that is expressed only in activated cytotoxic T lymphocytes. We show here that cathepsin G, CGL-1, and CGL-2 are linked on an approximately 50-kilobase locus found on human chromosome 14 at band q11.2. This gene cluster maps to the same chromosomal band as the alpha and delta T-cell receptor genes; this region is involved in most chromosomal translocations and inversions that are specifically associated with T-cell malignancies.

Blotting, Southern↗
PubMed1990

Oncogene expression and immunoglobulin synthesis in a North American Burkitt (NAB-2) lymphoma cell line with a 8;22 chromosome translocation.

A Burkitt's lymphoma (BL) cell line, (NAB-2) deriving from a North American patient, exhibited a 8;22 (q22;q11-12) translocation involving the c-myc gene and lambda immunoglobulin genes. In addition, NAB-2 cells have two other consistent translocations: a 1;5 (p22;q23) and a 3;7 (p25;q22), with breakpoints close to the location of N-ras, fms, and raf-1 protooncogenes, respectively. In situ hybridization with myc, N-ras, and raf-1 radiolabeled DNA probes to NAB-2 chromosomes showed that none of these genes was relocated as a result of translocation. However, by Northern blot analysis, the myc mRNA was represented by two transcripts, one approximately 2.4 kb and the other considerably larger (74 kb). The raf-1 gene transcript was also detected in NAB-2 cells; however, its size and level were similar to those seen in two other BL lines. On the other hand, the N-ras, fms, and fgr genes, which are frequently activated in BL, were not actively transcribed. NAB-2 cells also have a chromatid defect visible as an achromatic region on the short arm of chromosome 2 near the locus of the kappa immunoglobulin gene. This alteration, which is a viral modification site caused by the Epstein-Barr virus or viral products, had no influence on immunoglobulin synthesis, as NAB-2 cells concordant to the 8;22 translocation were positive for cytoplasmic and surface lambda light chains. Although NAB-2 cells exhibit several chromosomal abnormalities, only translocation, 8;22 was associated with gene alterations relevant to the neoplastic development of this malignancy.

Adolescent↗
PubMed1989

Preferential sites for viral integration on mammalian genome.

Chromosomal localization of human papillomavirus (HPV) 16 and 18 on human cervical carcinomas and epithelial cell lines obtained after HPV transfection has uncovered a nonrandom association of viral integration and specific genome sites. Fragile sites appear to be preferential targets for viral integration because of their structural and functional characteristics through which chromosomal anomalies, alterations in protooncogene activity, and gene amplification can occur. Individually or in association, such changes lead to the acquisition of an unlimited cell growth potential but not tumorigenicity. Genetic instability and uncontrolled cell division resulting from HPV integration increase the cell's susceptibility to other exogenous carcinogenic factors that may complete the process of neoplastic development.

Chromosome Banding↗
PubMed1989

Genomic organization and chromosomal localization of the human cathepsin G gene.

Cathepsin G is a 26,000-Da serine protease that is found in the azurophil granules of neutrophils and monocytes. The cathepsin G gene is expressed at high levels in U937 promonocytic cells, but is down-regulated with phorbol-induced differentiation. To characterize the genomic sequences responsible for the regulated expression of this gene, we screened a human genomic fibroblast library using cathepsin G cDNA, and obtained two lambda clones that contained the cathepsin G locus. The cathepsin G gene spans 2.7 kilobase pairs of genomic DNA and consists of 5 exons and 4 introns. The genomic organization of cathepsin G is similar to that of human neutrophil elastase, rat mast cell protease II, murine adipsin, and murine cytotoxic T-cell serine proteases, with protease catalytic residues located near the borders of exons 2, 3, and 5. Using in situ hybridization techniques, we localized cathepsin G to chromosome 14q11.2, a site that is near the alpha/delta T-cell receptor complex. Cathepsin G transcription is abolished in U937 nuclei with 2 micrograms/ml alpha-amanitin, indicating that this gene is probably transcribed by RNA polymerase II. The 5' end of the cathepsin G gene was defined by primer extension and S1 nuclease protection assays. A TATA box is found at position -29, and a CAAT box is found at -69 with respect to the transcription initiation site. Having defined the genomic structure and chromosomal location of cathepsin G, we are now attempting to identify the DNA elements in or near this gene that mediate its tissue and development-specific pattern of expression.

Amino Acid Sequence↗
PubMed1989

Amplification of the integrated viral transforming genes of human papillomavirus 18 and its 5'-flanking cellular sequence located near the myc protooncogene in HeLa cells.

The human papillomavirus type 18 integrated in the HeLa cell genome is amplified on chromosome 8. E6, E7, and E1 open reading frames are amplified 5-fold, and the late viral DNA region, the viral long control region, and cellular flanking sequences are amplified 15-fold. The common 5'-flanking cellular DNA was localized by in situ hybridization of normal and HeLa cells only on chromosome 8 band q24. This flanking probe is included in the amplification unit of Colo320 cells, but in the case of HeLa the amplified region does not include the myc gene which is structurally conserved. Viral integration on chromosome 8 represents an independent event and not a rearrangement of viral DNA located on other chromosomes. The amplification of HPV-18 E6 and E7 open reading frames and the constitutive expression of the myc protooncogene may contribute to immortalization and/or proliferative capacity of HeLa cells.

Base Sequence↗
PubMed1989

Two type II keratin genes are localized on human chromosome 12.

Human genomic DNA containing two type II keratin genes, one coding for keratin 1 (K1, a 68-kD basic protein) and another closely linked type II gene 10-15 kb upstream (K?, gene product unknown), was isolated on a single cosmid clone. EcoRI restriction fragments of the cosmid were subcloned into pGEM-3Z, and specific probes comprising the C-terminal coding and 3' noncoding regions of the two genes were constructed. The type II keratin genes were localized by in situ hybridization of the subcloned probes to normal human lymphocyte chromosomes. In a total of 70 chromosome spreads hybridized with the K? probe (gHK?-3', PstI, 800 bp), 36 of the 105 grains observed were on chromosome 12, and 32 of these were clustered on the long arm near the centromere (12q11-13). In 100 labeled metaphases hybridized with the K1 probe (gHK1-3', BamHI-PstI, 2100 bp), 53 grains localized to chromosome 12 and 46 of these were found in the same region (q11-13). Therefore, both the gene for human keratin 1, a specific marker for terminal differentiation in mammalian epidermis, and another closely linked unknown type II keratin gene (K?, 10-15 kb upstream of K1) are on the long arm (q11-13) of human chromosome 12.

Cells, Cultured↗
PubMed1989

Chromosomal localization of DBL oncogene sequences.

The DBL oncogene was generated by rearrangements involving three discontinuous regions of the human genome. Analyses of panels of human X rodent somatic cell hybrids demonstrated that the DBL proto-oncogene located on the X chromosome (just proximal or distal to bands q26-27.2) underwent recombination at its 5' and 3' ends with sequences derived from chromosomes 3 (p13q-ter) and 16 (p13-q22), respectively. DBL was localized to chromosome Xq27-q28 by in situ hybridization. Another oncogene, MCF2, was previously shown to contain sequences derived from Xq27 as well. Comparison of the restriction maps and nucleotide sequences of genomic and cDNA clones representing the chromosome X-specific sequences of the DBL oncogene and MCF2, taken together with their chromosomal localization, indicates that these oncogenes were derived from the same genetic locus.

Animals↗
PubMed1989

Localization of the human erbB-2 gene on normal and rearranged chromosomes 17 to bands q12-21.32.

Through the use of a cDNA probe, the human erbB-2 gene was localized by in situ hybridization of normal human chromosomes at 17q11-q21. In situ hybridization of chromosomes derived from fibroblasts carrying a constitutional 15;17t(q22.3;q11.21) translocation showed that the erbB-2 gene was relocated on the rearranged chromosome 15. These results as well as grain localization on prophase chromosomes locate the erbB-2 gene at 17q12-q21.32. This localization may facilitate the search for human malignancies with chromosome changes involving the erbB-2 gene.

Base Sequence↗
PubMed1989

Isolation and characterization of ERBB3, a third member of the ERBB/epidermal growth factor receptor family: evidence for overexpression in a subset of human mammary tumors.

A related DNA fragment distinct from the epidermal growth factor receptor and ERBB2 genes was detected by reduced stringency hybridization of v-erbB to normal genomic human DNA. Characterization of the cloned DNA fragment mapped the region of v-erbB homology to three exons with closest identity of 64% and 67% to a contiguous region within the tyrosine kinase domains of the epidermal growth factor receptor and ERBB2 proteins, respectively. cDNA cloning revealed a predicted 148-kDa transmembrane polypeptide with structural features identifying it as a member of the ERBB gene family, prompting us to designate the gene as ERBB3. It was mapped to human chromosome 12q13 and was shown to be expressed as a 6.2-kilobase transcript in a variety of normal tissues of epithelial origin. Markedly elevated ERBB3 mRNA levels were demonstrated in certain human mammary tumor cell lines. These findings suggest that increased ERBB3 expression, as in the case of epidermal growth factor receptor and ERBB2, may play a role in some human malignancies.

Amino Acid Sequence↗
PubMed1989

Induction of sister chromatid exchanges by tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in human and hamster cells.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a nicotine derived N-nitrosamine, is a carcinogen that induces tumors in mice, rats and hamsters. To assess the ability of NNK to interact with the cellular DNA as an essential step in carcinogenesis, the induction of sister chromatid exchange (SCE) was examined in cultured normal human lymphocytes (HL) and Chinese hamster V79 cells. SCE formation is a sensitive indicator of carcinogen-DNA interaction that correlates with the induction of mutation and neoplastic cell transformation. HL and V79 cells were treated for 2 h with 20, 50, 100 and 200 micrograms/ml of NNK with and without application of metabolic activation S-9 mixture, and subsequently incubated for two rounds of replication in the presence of 5-bromodeoxyuridine required for SCE visualization. In V79 cells NNK produced a dose-dependent increase in SCE only with metabolic activation. In HL NNK induced a small but statistically significant increase in SCE with or without metabolic activation. These data provide the first evidence that NNK and/or its metabolic derivatives are able to induce DNA damage leading to SCE formation both in hamster and human cells. The differences in response between the two cell types suggests the existence of a difference in susceptibility associated with NNK metabolism and its interaction with cellular DNA.

Animals↗
PubMed1989

Induction of human cervical squamous cell carcinoma by sequential transfection with human papillomavirus 16 DNA and viral Harvey ras.

Clinical and epidemiological data are consistent with the hypothesis that human papillomaviruses (HPVs) are a factor in genital, particularly cervical cancer. Although HPV16 and 18 are found primarily in cervical malignancy, the transfection of HPV16 or 18 DNA into cervical cells results in immortalization but not tumorigenicity. The addition of activated Ha-ras, an oncogene found in some cervical cancers expressing HPV16 or 18, to HPV16-immortalized human cervical cells results in malignancy as proven by the formation of cystic squamous cell carcinomas by HPV16-Ha-ras cells in nude mice. This two-stage model utilizing relevant human cells demonstrates that HPVs play a critical role in cervical malignancy and provides a system for elucidating critical cellular changes associated with progression to malignancy.

Animals↗
PubMed1988

Chromosome alterations in Syrian hamster cells transformed in vitro by sodium bisulfite, a nonclastogenic carcinogen.

Sodium bisulfite, a nonmutagen at neutral pH, induces neoplastic transformation of cultured Syrian hamster fetal cells. Morphologically transformed fibroblast colonies were isolated, and derived cell lines formed anchorage-independent colonies in agarose and progressively growing s.c. fibrosarcomas in nu/nu mice. Five tumorigenic cell lines analyzed by G- and C-banding were chromosomally abnormal with numerical deviations and structural alterations. Three tumors that developed in nude mice had the chromosome constitution of the inoculated transformed cell as well as secondary changes associated with tumor progression. Transformed cell lines had either a predominantly near-diploid or a near-tetraploid population with consistent chromosome gain and loss. Monosomy of the chromosome 13 observed in three cell lines was a nonrandom numerical alteration. Four lines had abnormal chromosomes resulting from deletions, unbalanced translocations, or centric fusions, and one cell line had a chromosome with a homogeneously staining region. Changes of chromosomes 1 and X were observed in three lines. The breakpoints on X chromosome nonrandomly involved the region qa5 which is frequently affected in hamster cells transformed by other carcinogens and may result in loss of genes essential for the maintenance of a normal phenotype. The formation of abnormal chromosomes cannot be directly attributed to the initial DNA damage as bisulfite concentrations effective in causing neoplastic transformation induced a significant but minimal increase in sister chromatid exchanges and failed to cause chromosome aberrations. Bisulfite inhibition of DNA replication might be a contributing factor in the occurrence of abnormal chromosomes. This cytogenetic analysis provides the first evidence that neoplastically transformed cells by a nonclastogenic carcinogen exhibit persistent chromosome rearrangements, a genetic alteration essential to the process of malignant transformation.

Animals↗
PubMed1988

Nonrandom chromosome alterations in human malignant mesothelioma.

Malignant mesothelioma (MM) is a neoplasm closely associated with asbestos exposure, which has been implicated in 70-80% of the cases. In this study, nine MM (two fresh surgical specimens, two permanent cell lines, and five xenografts in nude mice) were examined cytogenetically. Six patients had a known history of asbestos exposure. Seven MM were chromosomally abnormal, the majority having complex structural alterations affecting different chromosomes, whereas two fresh surgical specimens had a normal chromosome constitution. Alterations of chromosome 3 were detected in seven cases and changes involving chromosomes 1 and 7 were observed in six cases. The breakpoints of translocations and deletions on chromosome 1 involved several bands; however, 50% of the breakpoints were near the locations of Blym, L-myc, and ski protooncogenes. Forty % of the breaks on chromosome 7 involved bands q11.1-11.2 and 20% were at q22, the location of the met protooncogene. Nonrandom changes on chromosome 3 were interstitial or terminal deletions, and translocations involving the region p14-21. The deleted 3p segment was identifiable as part of a chromosome translocation in one MM and was apparently lost in the other six. The deletions involving 3p are either spontaneous or asbestos-induced lesions at vulnerable genomic sites and are the most common and nonrandom chromosome alterations observed. Possibly 3p abnormalities are causally related to the development of this malignancy.

Adult↗
PubMed1988

Chromosomal localization of the gene for a human thyroid hormone-binding protein.

A cDNA for the gene that encodes for a human cellular thyroid hormone-binding protein (p55) has recently been isolated and sequenced. The sequence of p55 indicates that it is identical to the protein disulfide isomerase and the beta-subunit of prolyl 4-hydroxylase. By in situ hybridization, the gene for p55 was localized on chromosome 17 at band q25. This localization shows that the p55 gene is not linked to either erbA1 or erbA2; two other thyroid hormone-binding protein genes are located at 17q 11-21 and 3p21-pter, respectively. The localization of p55 gene will permit the evaluation of the possible effects of chromosome changes on the structure and activity of the p55 gene in chromosome syndromes or neoplasms.

Carrier Proteins↗
PubMed1987

Overexpression of the EGF receptor-related proto-oncogene erbB-2 in human mammary tumor cell lines by different molecular mechanisms.

Amplification of the erbB/EGF receptor and a structurally related gene, designated erbB-2, have previously been detected in a variety of human tumors. In a series of human mammary tumor cell lines, analysis of transcripts of these genes revealed elevated levels of one or the other in more than 60% of tumors analyzed. Eight cell lines demonstrated erbB-2 mRNA levels ranging from 4- to 128-fold above those of normal controls. erbB-2 expression was evaluated in comparison to the expression level of actin observed in these cell lines. There was no evidence of an aberrantly sized erbB-2 transcript in any of these lines. Immunoblot analysis indicated elevation in levels of the 185-kd product of the erbB-2 gene expressed by these cells. In four lines erbB-2 gene amplification in the absence of an apparent gene rearrangement was demonstrated. In a representative cell line of this type, SK-BR-3, the amplified erbB-2 gene copies were located in an aberrant chromosomal location. Four additional cell lines, which demonstrated 4- to 8-fold overexpression of erbB-2 mRNA, did not exhibit gene amplification. In a representative cell line of this type ZR-75-1, an apparently normal chromosomal location was found for the erbB-2 gene. Our findings indicate that overexpression of the erbB-2 gene in mammary tumor cell lines is frequent and associated with different genetic abnormalities.

Breast Neoplasms↗