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N C Popescu

Publications and source records attributed to N C Popescu.

At least 37 records · Page 2Linked to original sources
PubMed2000

Alterations of the FHIT gene in human hepatocellular carcinoma.

FHIT (fragile histidine triad), a candidate tumor suppressor gene, encompasses FRA3B, a region with the highest fragility in the human genome, and is altered in a large number of human cancers, particularly those of epithelial cell origin and associated with known carcinogenic agents. Human hepatocellular carcinoma (HCC), a major cancer worldwide, is closely related to carcinogenic agents such as hepatitis B and C virus infections, dietary aflatoxin, alcohol consumption, and exposure to chemical carcinogens. To assess the extent and the nature of the FHIT gene alterations and their implications in the development of HCC, several cell lines and primary tumors were cytologically and molecularly examined. The FHIT gene is expressed in normal hepatic cells and is not expressed or is abnormally expressed in cultured tumor cells derived from HCC. Down-regulation of the FHIT gene was detected by Northern blot analysis in 9 of 14 cell lines However, neither abnormal FHIT transcripts nor point mutations in DNA sequences of reverse transcription-PCR products (exons 2-9) were identified. Expression of FHIT protein was not detected by immunostaining in 5 of 10 primary tumors. Four cell lines showing mRNA down-regulation did not express FHIT protein as demonstrated by Western blot analysis. Allelic loss of intron 5 of the FHIT gene was detected in 10 of 34 informative samples from primary tumors. Structural alterations of chromosome 3p were identified in 8 of 13 HCC cell lines. Deletions or translocations involving region 3p14.2 were identified by fluorescence in situ hybridization with a YAC850A6 probe spanning the FHIT locus on chromosomes derived from cell lines with an abnormal FHIT gene expression. These combined results indicate that the FHIT gene is a frequent target and may be implicated in a subset of liver cancers.

Acid Anhydride Hydrolases↗
PubMed2000

Genomic structure and chromosome location of the mouse RelA p65 gene (Rela).

The RelA (p65) subunit of transcription factor NF-kappaB plays a critical role in development, and rela(-/-) knockout mice die in utero from massive liver apoptosis. Only partial sequences of the mouse Rela gene are available. We have determined the genomic structure of mouse Rela and promoter, and have mapped the gene to chromosome 19B1-3.

Animals↗
PubMed2000

Profile of genetic alterations and tumorigenicity of human breast cancer cells.

The profile of genetic alterations in four breast carcinoma cell lines, SK-BR-3, BT-474, MDA-MB361 and ZR-75-1 was examined by comparative genomic hybridization, G-band karyotyping, reverse chromosome painting and fluorescence in situ hybridization of single-copy genes. These lines are aneuploid with complex structural rearrangements and have DNA copy-number imbalances involving multiple sites that include amplification of ERBB-2 and MYC proto-oncogenes which are implicated in breast cancer pathogenesis. A novel site of high level amplification was mapped on chromosome 15. All lines were tumorigenic in nude mice, however, the latency and the incidence of tumor formation varied; SK-BR-3 and MDA-MB361 produced tumors in a shorter time and had a higher total number of genomic imbalances compared to BT-474 and ZR-75-1 cells. Tumor cell behavior in vivo was not reflected by the rate of in vitro cell proliferation. Underrepresentation on the long arm of chromosome 18 was the sole alteration that correlated with an increased tumorigenicity. Chromosome 18q is rich in tumor suppressor genes and its loss is prevalent in primary node-positive breast tumors. Cell lines with monoclonal populations preserve the genetic characteristics of the primary tumor and their use may facilitate the detection of specific alterations associated with breast cancer progression.

Animals↗
PubMed1999

Human FRAG1 encodes a novel membrane-spanning protein that localizes to chromosome 11p15.5, a region of frequent loss of heterozygosity in cancer.

We have previously identified a chromosomal rearrangement between fibroblast growth factor receptor 2 (FGFR2) and a novel gene, FRAG1, in a rodent model of osteosarcoma. To assess the potential role of FRAG1 in disease further, we have isolated cDNA and genomic clones of human FRAG1. Sequence analysis of the cDNA revealed the presence of an insertion not contained in the original FRAG1 sequence. This insertion in human FRAG1 encoded a region highly homologous to and immediately following the first 55 amino acids of the protein, indicating the presence of a repetitive domain within FRAG1, designated the FRAG1 homology (FH) domain. Analysis of FRAG1 gene structure revealed that the FH domains were encoded by tandem duplicated exons. Database searches identified several transmembrane proteins displaying homology to the FH domain of FRAG1. In addition, hydropathy analysis predicted FRAG1 to encode an integral membrane protein with multiple membrane-spanning segments. FRAG1 mRNA was ubiquitously expressed in human adult tissues and several tumor cell lines at varying levels of abundance. Human FRAG1 was mapped by fluorescence in situ hybridization and radiation hybrid analysis to chromosome 11 at band p15.5, a region implicated in Beckwith-Wiedemann syndrome and a region of frequent loss of heterozygosity in multiple tumor types. These results suggest that FRAG1 may be a useful candidate gene for genetic disorders associated with alterations at 11p15.5.

Adult↗
PubMed1999

Palmitoyl-protein thioesterase gene expression in the developing mouse brain and retina: implications for early loss of vision in infantile neuronal ceroid lipofuscinosis.

Mutations in the palmitoyl-protein thioesterase (PPT) gene cause infantile neuronal ceroid lipofuscinosis (INCL), the clinical manifestations of which include the early loss of vision followed by deterioration of brain functions. To gain insight into the temporal onset of these clinical manifestations, we isolated and characterized a murine PPT (mPPT)-cDNA, mapped the gene on distal chromosome 4, and studied its expression in the eye and in the brain during development. Our results show that both cDNA and protein sequences of the murine and human PPTs are virtually identical and that the mPPT expression in the retina and in the brain is temporally regulated during development. Furthermore, the retinal expression of mPPT occurs much earlier and at a higher level than in the brain at all developmental stages investigated. Since many retinal and brain proteins are highly palmitoylated and depalmitoylation by PPT is essential for their effective recycling in the lysosomes, our results raise the possibility that inactivating mutations of the PPT gene, as occur in INCL, are likely to cause cellular accumulation of lipid-modified proteins in the retina earlier than in the brain. Consequently, the loss of vision occurs before the deterioration of brain functions in this disease.

Amino Acid Sequence↗
PubMed1999

Novel recurrent genetic imbalances in human hepatocellular carcinoma cell lines identified by comparative genomic hybridization.

To search for recurrent and specific genomic alterations in human hepatocellular carcinoma (HCC), we examined 18 cell lines by comparative genomic hybridization (CGH), a molecular cytogenetic approach that allows positional identification of gains and losses of DNA sequences of the entire tumor genome. We report here a distinct pattern of multiple recurrent DNA copy-number gains and losses that include alterations frequently seen in other neoplasias as well as changes potentially specific for HCC. The most frequent gains were localized on 1p34.3-35, 1p33-34.1, 1q21-23, 1q31-32, 6p11-12, 7p21, 7q11.2, 8q24.1-24.2, 11q11-13, 12q11-13, 12q23, 17q11. 2-21, 17q23-24, and 20p11.1-q13.2. Recurrent losses were mapped on 3p12-14, 3q25, 4p12-14, 4q13-34, 5q21, 6q25-26, 8p11.2-23, 9p12-24, 11q23-24, 13q12-33, 14q12-13, 15q25-26, 18q11.2-22.2, and 21q21-22. Seventeen genomic imbalances are novel in HCC, thus extending significantly the map of genetic changes and providing a starting point for the isolation of new genes relevant in pathogenesis of liver neoplasia, as well as providing molecular probes for both diagnosis and monitoring treatment of the disease.

Carcinoma, Hepatocellular↗
PubMed1999

Nonrandom cytogenetic alterations in hepatocellular carcinoma from transgenic mice overexpressing c-Myc and transforming growth factor-alpha in the liver.

Identification of specific and primary chromosomal alterations during the course of neoplastic development is an essential part of defining the genetic basis of cancer. We have developed a transgenic mouse model for liver neoplasia in which chromosomal lesions associated with both the initial stages of the neoplastic process and the acquisition of malignancy can be analyzed. Here we analyze chromosomal alterations in 11 hepatocellular carcinomas from the c-myc/TGF-alpha double-transgenic mice by fluorescent in situ hybridization with whole chromosome probes, single-copy genes, and 4'-6-diamidino-2-phenylindole (DAPI-) and G-banded chromosomes and report nonrandom cytogenetic alterations associated with the tumor development. All tumors were aneuploid and exhibited nonrandom structural and numerical alterations. A balanced translocation t(5:6)(G1;F2) was identified by two-color fluorescent in situ hybridization in all tumors, and, using a genomic probe, the c-myc transgene was localized near the breakpoint on derivative chromosome der 6. Partial or complete loss of chromosome 4 was observed in all tumors with nonrandom breakage in band C2. Deletions of chromosome 1 were observed in 80% of the tumors, with the most frequent deletion at the border of bands C4 and C5. An entire copy of chromosome 7 was lost in 80% of the tumors cells. Eighty-five percent of the tumor cells had lost one copy of chromosome 12, and the most common breakpoint on chromosome 12 occurred at band D3 (28%). A copy of chromosome 14 was lost in 72%, and band 14E1 was deleted in 32% of the tumor cells. The X chromosome was lost in the majority of the tumor cells. The most frequent deletion on the X chromosome involved band F1. We have previously shown that breakages of chromosomes 1, 6, 7, and 12 were observed before the appearance of morphologically distinct neoplastic liver lesions in this transgenic mouse model. Thus breakpoints on chromosome 4, 9, 14, and X appear to be later events in this model of liver neoplasia. This is the first study to demonstrate that specific sites of chromosomal breakage observed during a period of chromosomal instability in early stages of carcinogenesis are later involved in stable rearrangements in solid tumors. The identification of the 5;6 translocation in all of the tumors has a special significance, being the first balanced translocation reported in human and mouse hepatocellular carcinoma and having the breakpoint near a tumor susceptibility gene and myc transgene site of integration. Moreover, its early occurrence indicates that this is a primary and relevant alteration to the initiation of the neoplastic process. In addition, the concordance between the breakpoints observed during the early dysplastic stage of hepatocarcinogenesis and the stable deletions of chromosomes 1, 4, 6, 7, 9, and 12 in the tumors provides evidence for preferential site of genetic changes in hepatocarcinogenesis.

Age Factors↗
PubMed1999

Nonrandom breakpoints of unbalanced chromosome translocations in human hepatocellular carcinoma cell lines.

In the search for specific chromosomal alterations in human hepatocellular carcinomas (HCC), we analyzed two new HCC cell lines and identified nonrandom changes by combined G-banding and fluorescence in situ hybridization (FISH). Cell line 7703 was established from an HCC deriving from a patient in the Qidong region of China, where the incidence of HCC is very high and is associated with hepatitis-B virus infection and exposure to aflatoxin. This line has a highly rearranged karyotype eliciting complex rearrangements involving the majority of chromosomes. The second line, SK-Hep-1, derived from a liver adenocarcinoma, is less heterogeneous, having few altered chromosomes. We have characterized the majority of structural and numerical alterations and identified in both lines unbalanced translocations with the breakpoints nonrandomly involving regions 1p36 and 3p14 and gain of chromosome 6p and 8q. While gain of 6p and 8q are recurrent in HCC, translocations of 1p and 3p are described for the first time. Damage and recombination at the breakpoint sites on chromosomes 1 and 3 might have resulted in activation of proto-oncogene, formation of new oncogenic chimeric genes, or loss of tumor suppressor genes.

Carcinoma, Hepatocellular↗
PubMed1999

Sister chromatid exchange formation in mammalian cells is modulated by deoxyribonucleotide pool imbalance.

The formation of sister chromatid exchanges (SEC) is closely related to DNA replication which is dependent on the proper balance of deoxyribonucleic triphosphates. Since DNA precursor imbalances can influence DNA metabolism, the relationship between 5-bromodeoxyuridine (BrdUrd)-induction of SCE and nucleotide pool imbalance was examined in Syrian hamster fetal cells (HFC) and mouse 3T6 cell line. In exponentially growing HFC, deoxyadenosine and deoxyguanosine stimulated the formation of SCE, while deoxycytidine (dCyd) prevented the dose dependent increase of SCE caused by BrdUrd. Cell growth inhibition produced by amino acid deprivation resulted in a significant increase in SCE as compared to exponentially growing cultures. This SCE enhancement was reduced by dCyd in HFC and did not occur in mouse 3T6 clone deficient in deoxycytidine deaminase. The modulation of SCE by DNA precursors is consistent with the induction of BrdUrd mutagenesis in mammalian cells and raises the possibility that common DNA changes are responsible for the induction of SCE and mutation in mammalian cells.

Animals↗
PubMed1999

Flavone acetic acid induces a G2/M cell cycle arrest in mammary carcinoma cells.

Flavone acetic acid (FAA) is a synthetic flavonoid that demonstrated extraordinary anti-tumour properties in murine models but was not effective in clinical trials. In an effort to better understand the molecular mechanisms by which FAA asserts its tumouricidal activities, we have examined the effect of FAA on the cell cycle. We observed FAA-mediated G2/M cell cycle arrest in mammary carcinoma cells at a concentration previously demonstrated to have anti-tumour effects in rodent models. The cell cycle arrest was accompanied by an increase in the P34cdc2 (cdc2) cyclin-dependent kinase activity. Morphological cytogenetic analysis demonstrated a colcemid-like effect of FAA on cytokinesis by causing accumulation of condensed C-metaphases of a sustained mitotic block. The cell cycle effect was blocked by the antioxidants ADPC and ascorbate, the superoxide scavenger Tiron, and the sphingosine kinase inhibitor L-cycloserine, but not by inhibitors of nitric oxide synthase. Based on these data, we propose that FAA may induce cell cycle arrest by stimulating the activity of acidic sphingomyelinase leading to the generation of reactive oxygen species.

Animals↗
PubMed1999

Recurrent alterations of the short arm of chromosome 3 define a tumor suppressor region in rat mammary tumor cells.

Cytogenetic alterations associated with different stages in carcinogenesis can be distinguished in cultured human or rodent cells transformed by carcinogenic agents. Three tumorigenic rat mammary epithelial cell lines transformed in vitro with 7,12, -dimethylbenz[a]anthracene alone or in combination with 12-O-tetradecanoylphorbol-13-acetate were examined cytogenetically. Non-random alterations consisting of translocations involving the short arm of chromosome 3 and trisomy of chromosomes 14 and X were identified in all three lines. Deletion and inversion of chromosome 1 with the breakpoint at band 1q22 and a duplication 1q 32-43 and trisomy of chromosome 2 were observed in two cell lines. The accumulation of structural alterations and chromosome imbalances during the process of cell immortalization and acquisition of tumorigenicity are required for normal rat mammary cells to become malignant. Unbalanced translocations of chromosome 3 resulting in loss of the short arm had the breakpoint at 3p11. This site is a hotspot of breakage and recombination in various rat tumors and may represent a region of tumor suppressor gene critical to the development of rat mammary tumors, as well as other types of tumors.

Animals↗
PubMed1998

Natural melatonin 'knockdown' in C57BL/6J mice: rare mechanism truncates serotonin N-acetyltransferase.

Pineal melatonin synthesis (serotonin --> N-acetylserotonin --> melatonin) is severely compromised in most inbred strains of mice, in many cases because serotonin is not acetylated by serotonin N-acetyltransferase (arylalkylamine N-acetyltransferase, AANAT). We have found that in the C57BL/6J strain, AANAT mRNA encodes a severely truncated AANAT protein, because a pseudo-exon containing a stop codon is spliced in. This is the first identification of a natural mutation which knocks down melatonin synthesis. The decrease in melatonin signaling may have been a selective factor in the development of laboratory strains of mice because melatonin can inhibit reproduction and modify circadian rhythmicity.

Animals↗
PubMed1998

Identification of mammaglobin B, a novel member of the uteroglobin gene family.

In this report, we have identified, sequenced, and characterized the expression pattern of a novel human gene, mammaglobin B. Mammaglobin B (MGB2) is highly homologous to mammaglobin (MGB1), a previously characterized human gene whose expression is limited to the mammary epithelium and frequently up-regulated in human breast cancer cells. Based upon amino acid sequence similarities, both mammaglobin and mammaglobin B may be considered members of a larger, mammalian multigene family that includes rabbit uteroglobin, human Clara Cell 10-kDa protein (CC10), and the multimeric rat prostatein protein. Together with the human CC10 gene, mammaglobin and mammaglobin B are closely linked on human chromosome 11q13. However, despite their primary sequence similarity and close chromosomal proximity, the expression of mammaglobin and mammaglobin B is nonconcordant in both nonmalignant and neoplastic tissue.

Amino Acid Sequence↗