A study of chromosomal changes associated with amplified dihydrofolate reductase genes in rat hepatoma cells and their dedifferentiated variants.

Fougère-Deschatrette, Catherine; Schimke, Robert T.; Weil, Dominique; Weiss, Mary C.

doi:10.1083/jcb.99.2.497

Cited by 23 publications

(5 citation statements)

References 27 publications

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“…Along these lines, involvement of chromosome 4 in the progression of established tumors to a more advanced state has also been reported in other systems. For example, the involvement of complex interchange between chromosomes 3 and 4 has been demonstrated to be associated with the progression of a chemically induced rat hepatoma [42]. Likewise the spontaneous transformation of a nontumorigenic rat myofibroblast line in vitro to a tumorigenic variant is associated with the development of trisomy of chromosomes 4 , 7 , 11, 19, and 20.…”

Section: Discussionmentioning

confidence: 99%

Nonrandom involvement of chromosome 4 in the progression of rat prostatic cancer

Lsaacs

Hukku

1988

The Prostate

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Owing to progression of the original spontaneous Dunning R-3327 rat prostatic cancer, a large series of transplantable prostatic tumors have been isolated that differ widely in their histological degree of differentiation, growth rate, androgen sensitivity, and metastatic ability. Using these parameters as criteria, the full spectrum of disease progression is represented within this Dunning system of rat prostatic cancers, ranging from slow-growing, well-differentiated, androgen-sensitive, nonmetastatic forms to fast-growing, anaplastic, androgen-independent, highly metastatic forms. Cytogenetic analysis of the two least progressionally advanced Dunning cancers (i.e., histologically well-differentiated, slow-growing, nonmetastatic variants) demonstrated no structural or numerical chromosomal aberration, suggesting that the initial development of prostatic cancer may not require detectable cytogenetic changes. In contrast, all 16 of the progressionally more advanced Dunning variants analyzed had a series of characteristic structural and/or numerical chromosomal aberrations that minimally involved chromosome 4. This nonrandom involvement of chromosome 4 was consistently observed regardless of whether the karyotype of the cancer was near-diploid or hyperaneuploid, suggesting that chromosome 4 aberrations are specifically involved in the progression of rat prostatic cancer. In addition, all four variants that were highly metastatic had, besides aberration of chromosome 4, structural aberrations involving chromosomes 1, 2, and 11. Of the 14 variants that did not have a high metastatic ability, only two had a similar aberrations involving chromosomes 1, 2, 4, and 11, suggesting that these specific chromosomal aberrations may be necessary, albeit not sufficient, for a high metastatic ability of rat prostatic cancers.

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Section: Discussionmentioning

confidence: 99%

Nonrandom involvement of chromosome 4 in the progression of rat prostatic cancer

Lsaacs

Hukku

1988

The Prostate

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“…In addition, if major regions of a chromosome are endoreduplicated and undergo chromatid pairing, a number of aberrant structures can be generated (so-called mitotic recombination events (28). Other chromosomes with amplified genes occur as dicentric chromosomes in which the fusion has occurred in the expanded region containing amplified genes (i.e., breakage-bridge fusion chromosomes) (29,30). In addition, karyological changes (e.g., translocations, expanded regions, ring chromosomes) that are not associated with DHFR gene amplification are often seen in MTX-resistant cell lines (30)(31)(32).…”

Section: The Model Of Overreplication Of Dna and Generation Of Chromomentioning

confidence: 99%

Overreplication and recombination of DNA in higher eukaryotes: potential consequences and biological implications.

Schimke¹,

Sherwood²,

Hill³

et al. 1986

Proc. Natl. Acad. Sci. U.S.A.

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203

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We propose that a fundamental problem in the faithful replication of complex chromosomes of higher eukaryotes is the proper control of both the number and timing of the multiple initiations of replication on single chromosomes. When replication patterns are disrupted by any of a variety of agents, overreplication of DNA can occur. We propose a model that accounts for the generation of a wide variety of chromosomal aberrations-rearrangements, resulting from the various ways in which the overreplicated strands can undergo recombination. We also discuss certain implications of the generation of chromosomal alterations in higher eukaryotes as they may relate to cancer chemotherapy, cancer progression, aging, and rapid speciation-evolution.Previous studies in our laboratory have examined the process of gene amplification in cultured mammalian cells (for reviews, see refs. 1 and 2). The frequency of a spontaneous doubling of the dihydrofolate reductase (DHFR) gene is 1 x io-, per cell generation (3), and this frequency can be increased 10-fold or more by pretreatment of cells with agents such as hydroxyurea (4), UV light, and carcinogens (5). Mariani and Schimke (6) provided evidence that when DNA synthesis was inhibited during hour 2 of S phase in synchronized Chinese hamster ovary (CHO) cells, DNA synthesized before the hydroxyurea block was rereplicated once the hydroxyurea was removed. This overreplication resulted in an increase in the number of DHFR genes and led to enhanced resistance to methotrexate (MTX). This overreplication involves not only the DHFR gene, which is replicated early in S phase, but also a large proportion of the DNA replicated prior to the inhibition of DNA synthesis.More recently Hill and Schimke (7) have extended these studies to show that treatment of cells with hydroxyurea results in the generation of a wide variety of chromosomal aberrations-rearrangements observed in the first M phase following inhibition of DNA synthesis. The aberrations include normal chromosomes with extrachromosomal DNA, increased frequencies of sister chromatid exchange, polyploidization, breakage-bridge fusion chromosomes, and gapped-fragmented chromosomes. Most significant in their results is the observation that the cells in which the chromosomal alterations are observed are derived from that subset of the treated cells that contains more than the G2 content of DNA as studied with DNA fluorochromes and flow cytometric techniques.We observed additionally (S.W.S., A.B.H., and R.T.S., unpublished data) that the increased DNA content of cells previously treated with hydroxyurea (or aphidicolin) does not result from fusion of cells or uptake of DNA from killed cells. The finding that the chromosomal alterations occur only within the subset of cells with additional DNA leads us to propose that the chromosomal alterations are the consequence of recombination events involving the strands of overreplicated DNA, and not that the additional DNA occurs after the generation of the chromosomal aberrations. Thus, we p...

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“…Thus, in culture, a transport-defective cell variant would not survive multiple step selections without, in addition, DHFR gene amplification. We have, indeed, observed this type of phenomena with a rat hepatocyte cell line (30). We are currently interested in the type of mutational event(s) leading to defective transport, since various treatments of mouse and CHO cells that enhance the frequency of DHFR gene amplification (in first-step selection protocols) also enhance equally extensively the frequency of another resistance mechanism(s).…”

mentioning

confidence: 99%

Identification of methotrexate transport deficiency in mammalian cells using fluoresceinated methotrexate and flow cytometry.

Assaraf

Schimke

1987

Proc. Natl. Acad. Sci. U.S.A.

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We have studied the frequency of transport mutations in methotrexate-resistant Chinese hamster ovary cells using a rapid-flow cytometric technique. After saturating cells with fluoresceinated methotrexate, we examined the ability of hydrophilic and lipophilic antifolates to displace fluoresceinated methotrexate binding to dihydrofolate reductase. Cells with methotrexate transport deficiency are unable to take up methotrexate and thus retain the fluorescence, whereas the lipophilic antifolates displace fluoresceinated methotrexate equally well in sensitive and resistant cell lines. These resistant clones fail to take up methotrexate and occur with high frequencies upon single-step selections at methotrexate concentrations =7-fold the 50% killing concentration.

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A study of chromosomal changes associated with amplified dihydrofolate reductase genes in rat hepatoma cells and their dedifferentiated variants.

Cited by 23 publications

References 27 publications

Nonrandom involvement of chromosome 4 in the progression of rat prostatic cancer

Nonrandom involvement of chromosome 4 in the progression of rat prostatic cancer

Overreplication and recombination of DNA in higher eukaryotes: potential consequences and biological implications.

Identification of methotrexate transport deficiency in mammalian cells using fluoresceinated methotrexate and flow cytometry.

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