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Y Wettergren

Publications and source records attributed to Y Wettergren.

10 recordsLinked to original sources
PubMed1999

Rapid method for relative gene expression determination in human tissues using automated capillary gel electrophoresis and multicolor detection.

The aim of this study was to evaluate a direct and automated post-polymerase chain reaction (PCR) detection system to simultaneously determine the relative gene expression levels of nine cancer-related human genes. Total RNA was prepared from flash-frozen biopsies derived from human colorectal tumors or normal mucosa and reverse-transcribed to cDNA which was PCR-amplified using primer pairs corresponding to the studied genes. In each reaction, the forward primer was labeled with a fluorescent dye. The PCR products were pooled and an internal size standard with a uniquely colored fluorescent dye was added. The samples were then subjected to automated capillary gel electrophoresis. Fragment analysis software was used to calculate the relative gene expression using beta-actin as the reference gene. We found that automated capillary gel electrophoresis with multicolor detection is a rapid, accurate and highly reproducible method for separation and quantification of PCR-amplified cDNA.

Autoanalysis↗
PubMed1995

Colcemid resistance in murine SEWA cells: non-Pgy gene amplification at low levels of resistance and preferential Pgy2 gene amplification at high levels of resistance.

Mammalian cell lines often become multidrug-resistant to cytotoxic drugs by amplification and/or overexpression of the P-glycoprotein (Pgy) genes. However, several malignant cell lines seem to acquire low levels of drug resistance by non-P-glycoprotein mediated mechanisms. We report here on cytogenetical signs of non-Pgy gene amplification in murine SEWA cells during the early steps of selection in Colcemid (COL). In line TC13COL0.01, rare cells exhibited a homogeneously staining region (HSR) distally in chromosome 16. As the COL-concentration was raised the HSR-chromosome was retained and, in addition, the cells developed numerous double minutes (DMs). The DMs, but not the HSR, contained amplified Pgy genes. The HSR may correspond to amplified heat shock protein 70 (Hsp70) genes, detected by Southern analysis. A second low-level COL-resistant line, TC13D70.01, contained DMs but showed no amplification of Pgy, Hsp70, Hsp90, alpha- or beta-tubulin genes. In higher COL-concentration, P-glycoprotein mediated drug resistance was induced. In contrast to actinomycin D-resistant SEWA cells, in which higher amplification levels of Pgy1 than of Pgy2 are regularly present, the COL-resistant lines showed a preference for Pgy2 gene amplification. These results are in line with the suggestion that the murine Pgy1 and Pgy2 genes have overlapping but distinct drug specificities.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

C-band-positive double minutes have kinetochore proteins.

Double minutes (DMs) have been shown generally to lack centromeres. In the present paper we report on C-band-positive DMs in Colcemid-resistant SEWA cells. These DMs were heavily labeled after in situ hybridization with mouse major satellite DNA and, furthermore, reacted positively with antikinetochore antibodies. Upon antikinetochore antibody labeling, the immunofluorescent signals of some DMs were strong, indicating that they had functional centromeres.

Animals↗
PubMed1994

Drug-specific rearrangements of chromosome 12 in hydroxyurea-resistant mouse SEWA cells: support for chromosomal breakage model of gene amplification.

In order to investigate whether specific, nonrandom chromosome rearrangements were involved in the induction of hydroxyurea (HU) resistance in mouse SEWA cells, we undertook detailed cytogenetic analyses of three independently selected lines during the long-term treatment with HU. We found that cells with trisomy 12 had selective advantage during early steps of HU treatment. Subsequently, numerous rearrangements of chromosome 12 took place in each of the HU-resistant cell lines. More specifically, the proximal end of chromosome 12 (band A3) was frequently involved in breaks and fusions generating multicentric marker chromosomes. In situ hybridization showed that the functional Rrm2 gene was located in this particular region of chromosome 12. Furthermore, amplification and rearrangements of the structural gene Rrm2 were detected both at the chromosomal and at the molecular level. As discussed, the results of the cytogenetic analyses support the chromosomal breakage model of gene amplification.

Animals↗
PubMed1993

Amplification and overexpression of the mouse mdr 1a gene in nine independently derived multidrug-resistant SEWA murine cell lines.

Many different drugs may be used in selecting cells for multidrug resistance (MDR). Enhanced expression and/or gene amplification is known to cause overproduction of membrane-bound 170,000 P-glycoproteins, responsible for the MDR. In rodents, the P-glycoproteins are encoded by a small gene family: mdr 1a, mdr 1b, and mdr 2. To evaluate the relationship between the pattern of MDR and the selecting drug, nine MDR sublines were independently selected from a sensitive mouse tumor cell line, SEWATC13K, using three different drugs. Each MDR subline displayed amplification of one or more of the three mdr genes, but only one, mdr 1a, was consistently overexpressed. Thus, our results indicate that the pattern of mdr gene amplification and overexpression is independent of the selective agent. Furthermore, in four of the MDR sublines, where all three mdr genes had been originally amplified, pulsed field gel electrophoresis (PFGE) revealed that amplification of mdr 1a, only, was a second step of gene amplification. In addition, the gene for the calcium-binding protein, sorcin, was coamplified in eight of the nine MDR sublines. The sorcin gene was overexpressed in seven of these eight sublines. Finally, hybridizations with a probe homologous with a putative region of RFLP (restriction fragment length polymorphism), indicated that the amplified sequences originate from one or the other of the two homologous chromosomes with no preference.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
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↗
PubMed1992

Amplicon structure in multidrug-resistant murine cells: a nonrearranged region of genomic DNA corresponding to large circular DNA.

Multidrug resistance (MDR) in tumor cell lines is frequently correlated with amplification of one or more mdr genes. Usually the amplified domain also includes several neighboring genes. Using pulsed-field gel electrophoresis, we have established a restriction map covering approximately 2,200 kb in the drug-sensitive mouse tumor cell line TC13K. The mapped region is located on mouse chromosome 5 and includes the three mdr genes, the gene for the calcium-binding sorcin protein, and a gene with unknown function designated class 5. Long-range maps of the amplified DNA sequences in five of six MDR sublines that had been independently derived from TC13K generally displayed the same pattern as did the parental cell line. All six MDR sublines exhibited numerous double minutes, and one of them displayed a homogeneously staining region in a subpopulation. Large circular molecules, most likely identical to one chromatid of the double minutes, were detected in four of the sublines by linearization with gamma irradiation. The size of the circles was about 2,500 kb, which correlated to a single unit of the amplified domain. We therefore propose that in four independent instances of MDR development, a single unit of about 2,500 kb has been amplified in the form of circular DNA molecules. The restriction enzyme map of the amplified unit is unchanged compared with that of the parental cell line, whereas the joining sites of the circular DNA molecules are not identical but are in the same region.

Animals↗
PubMed1985

Pleiotropic drug resistance and gene amplification in a SEWA mouse tumor cell line. Complex relations revealed by drug uptake data, and lipid and protein analysis.

SEWA mouse lines resistant to actinomycin D (AMD) or vincristine (VCR) exhibit the pleiotropic drug resistance (PDR) phenotype, and express a low-MW protein (p21) and numerous double minutes (DM). In drug uptake studies these lines were compared with the non-resistant parental line and with a methotrexate (MTX)-resistant line, not exhibiting PDR. On treatment with labelled AMD or VCR the two PDR lines displayed a highly reduced intracellular content of drug, whereas uptake of MTX was unchanged. Uptake of AMD was shown to be temperature-dependent. The MTX-resistant line did not exhibit any significant change in AMD or VCR uptake. Other workers have emphasized the role of a high-MW glycoprotein in the development of PDR. A search for a similar glycoprotein in our cells was unsuccessful. Since all indications point to membrane factors being important in the development of PDR, the lines were also subjected to lipid analysis. Compared with control cells distinct differences were detected in the lipid composition of all resistant lines (including the MTX-resistant line). In the course of our experiments, the DM in our most AMD-resistant line were replaced by two homogeneously staining regions (HSR). Simultaneously, the overproduction of p21 ceased, but the PDR phenotype persisted. This event tends to implicate a minor role for the p21 protein in PDR, but similar transitions from DM to HSR in other AMD-resistant SEWA lines were not accompanied by a decrease in p21 over-production. Our data point to a complex genetic control of multi-drug resistance.

Animals↗
PubMedDate not supplied

Chromatin bodies in multidrug resistant hybrid cells have centromeres and originate from homogeneously staining regions.

Antikinetochore antibodies from patients with the CREST syndrome of scleroderma were used as probes to study homogeneously staining regions (HSRs) in multidrug resistant (MDR) mouse tumor cells, and chromatin bodies (CBs) in MDR mouse-hamster hybrid cells. In one mouse tumor line the C-band positive HSR showed antigenic properties and displayed many weekly fluorescent spots, i.e. it contained kinetochore proteins. The immunofluorescence pattern of the HSR could also be observed in interphase nuclei. The C-band positive CBs of the hybrid cells had active centromeres, as shown by double kinetochore spots. These results support our hypothesis that CBs originate from C-band positive HSRs.

Animals↗