Co-amplification of rRNA genes with CAD genes in N-(phosphonacetyl)-L-aspartate-resistant Syrian hamster cells.

Wahl, Geoffrey M.; Vitto, L; Rubnitz, J

doi:10.1128/mcb.3.11.2066

Cited by 44 publications

(31 citation statements)

References 22 publications

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“…Gene amplification is often accompanied by coamplification of very large stretches of flanking DNA (10,36,38). To investigate whether some or all genes reside on the same amplified unit, we digested the DNA from resistant cells with restriction enzymes that cut infrequently in mammalian DNA and size fractionated the resulting fragments by pulsed field gradient gel electrophoresis (34), which allows separation of very large (100 to 1,000 kb) DNA fragments.…”

mentioning

confidence: 99%

Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line.

Bliek¹,

Velde-Koerts²,

Ling³

et al. 1986

Mol. Cell. Biol.

246

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(25,26). Their overproduction depends on the drug used for selection, however. In addition, the putative mouse homolog (21 kDa) of V19 has recently been reported to disappear after prolonged culture, even though multidrug resistance was retained (24). The loss of proteins (72 and 75 kDa) has also been found in a multidrug-resistant cell line (27), completing the spectrum of altered protein levels which have been associated with * Corresponding author. multidrug resistance. How each of these proteins contributes to the ability of the cell to maintain a low intracellular drug concentration is unknown.The overproduction of proteins, and in particular those involved in drug resistance in mammalian cells, is often the result of gene amplification (see references 7, 14, 21, 33, 36). Homogeneously staining regions or double minute chromosomes, both known to carry amplified DNA, have been observed in a variety of multidrug-resistant cell lines (3,5,12,29). The degree of amplification, reflected by the size of the homogeneously staining region or the number of double minute chromosomes, can be correlated with the level of P-glycoprotein overproduction (5,29,31). Recently, a cDNA clone encoding part of the P-glycoprotein has been isolated from an expression library (29). This clone hybridizes to a homogeneously staining region, and, in line with the cytological observations, the degree of amplification corresponds to the level of resistance. Although overproduction of the 170-kDa P-glycoprotein remains the most consistent feature, homogeneously staining regions have also been observed in multidrug-resistant cell lines without an apparent overproduction of the P-glycoprotein (24).The disparity in altered protein levels and gene amplification suggests that several proteins contribute to the multidrug-resistant phenotype. To identify genes encoding proteins involved in multidrug resistance, we constructed a cDNA library from the resistant chinese hamster ovary (CHO) cell line CH"C5 and isolated cDNA clones derived from overexpressed transcripts by differential hybridization. In this paper we describe the initial characterization of cDNAs corresponding to at least five genes that are overexpressed and amplified in the resistant cell line.MATERIALS AND METHODS Cell culture. The CHO cell lines AUXB1 and CHRC5 were cultured as described previously (22) without colchicine.

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confidence: 99%

Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line.

Bliek¹,

Velde-Koerts²,

Ling³

et al. 1986

Mol. Cell. Biol.

246

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“…Indeed, we have found that the majority of TUNEL positive micronuclei are lamin negative ( Figure 3). As nuclear lamins are substrates for the caspases that initiate apoptosis (21,22,23), the data suggest that there is a class of micronuclei that undergoes apoptosis under conditions where the main nucleus has its lamina intact and shows no chromatin condensation or other indications of apoptosis. These preliminary data suggest a new mechanism for localized degradation of nuclear DNA in the cytoplasm that is contained in a defective nuclear membrane.…”

Section: Specific Aim 5 Determining Whether Micronuclei Serve As Tramentioning

confidence: 99%

“…If DMs in tumours encode genes that are rate limiting for cell growth in vivo, as they appear to be in v/'fro 13 "' 3,18 , then their elimination would provide a chemotherapeutic strategy targeted at a specific molecular defect uniquely found in cancer cells 19 ' 20 . This is an attractive possibility as DMs occur frequently in clinically important neoplasms including those of the breast 21 , lung 22 , ovary 23 , and colon 24 . Only a fraction of DMs or HSRs have been shown to contain known oncogenes.…”

Section: Fluorescence Microscopymentioning

confidence: 99%

“…A retroviral vector was constructed to enable the efficient transfer and expression of H2B-GFP in a broad range of host cells. We used a vesicular stomatitis virus G glycoprotein (VSV-G) pseudotyped retroviral vector to obtain high viral titers [23]. COLO320DM cells harboring DMs containing an amplified c-mycgcne [24,25] were infected with the H2B-GFP retrovirus, and two days later over 90% of the cells ^expressed H2B-GFP protein.…”

Section: Visualization Of Dms In Living Cellsmentioning

confidence: 99%

“…Several clones were selected and expanded into cell lines for further analyses. Production of VSV-G pseudotyped retrovirus [23] was performed by co-transfection of pCLNC-H2BG and pMD.G (the plasmid encoding the envelope protein VSV-G) into 293gp/bsr cells as described [40]. COLO320DM cells [24] were grown in RPMI1640 medium supplemented with 10% FCS.…”

Section: Cell Lines and Transfectionmentioning

confidence: 99%

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Amplified Genes in Breast Cancer: Molecular Targets for Investigation and Therapy

Wahl¹

1999

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Multidrug resistance in ovarian cancer

Fojo

Hamilton

Young

et al. 1987

Cancer

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The development of acquired resistance has limited the effectiveness of chemotherapy in the treatment of ovarian cancer. Experimental model systems were developed to study the mechanisms associated with primary resistance to chemotherapeutic agents and broad cross-resistance (multidrug resistance) which is characteristic of human ovarian cancer. Doxorubicin-resistant cell lines developed in vitro by exposure of a sensitive cell line to increasing concentrations of doxorubicin develop resistance on the basis of a decrease in drug accumulation and have increased expression of the mdr-1 gene. This gene encodes for a membrane glycoprotein and leads to a decreased drug accumulation in drug resistant cell lines. Cell lines established from patients refractory to doxorubicin-containing combinations, however, do not demonstrate a decrease in drug accumulation. Studies are in progress on the measurement of mdr-1 levels in tumors of patients undergoing treatment to determine whether agents, such as verapamil may be useful in the treatment of drug resistant gynecologic cancers. Human ovarian cancer cell lines from drug resistant patients also has been demonstrated to increase levels of glutathione. Lowering of glutathione levels with buthionine sulfoximine (BSO), which irreversibly inhibits the enzyme gammaglutamyl cysteine synthetase, leads to a marked potentiation of the cytotoxicity of melphalan both in vitro and in vivo in a nude mouse model of human ovarian cancer. Based on those studies, BSO is undergoing toxicologic evaluation before initiation of clinical trials in drug resistant patients. Our studies demonstrate that drug resistance in human ovarian cancer is likely due to interaction of multiple factors. However, biochemical intervention in some of the key steps leading to drug resistance has been demonstrated experimentally feasible and indicates that pharmacologic reversal of drug resistance is a clinical possibility.Cancer 602075-2080, 1987.HEMOTHERAPY has continued to have an increas-C ingly important role in the effective treatment of gynecologic malignancies, in particular, ovarian cancer. Cisplatin-based combination chemotherapy regimens produce complete remissions in 60-80% of patients with advanced-stage (FIG0 Stages I11 and IV) ovarian cancer. ' Many of these patients remain continuously disease free. However, a significant fraction of patients with advanced ovarian cancer will not achieve a complete response to therapy or will relapse from a complete remission. The development of acquired resistance to individual antineoplastic drugs in ovarian cancer is frequently associated with a broad cross-resistance to structurally dissimilar drugs, resulting in only a 6% to 10% response rate to salvage chemotherapy. The identification of the

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Co-amplification of rRNA genes with CAD genes in N-(phosphonacetyl)-L-aspartate-resistant Syrian hamster cells.

Cited by 44 publications

References 22 publications

Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line.

Overexpression and amplification of five genes in a multidrug-resistant Chinese hamster ovary cell line.

Amplified Genes in Breast Cancer: Molecular Targets for Investigation and Therapy

Multidrug resistance in ovarian cancer

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