Methotrexate resistance in NIH3T3 cells expressing polyoma virus oncogenes

Wani, Maqsood A.; Snapka, Robert M.

doi:10.1002/tcm.1770090605

Cited by 1 publication

(3 citation statements)

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“…The methotrexate-resistant subclones were obtained in single-step in-vitro selections for resistance to 100 n M methotrexate (Wani & Snapka 1989). The measurement of dhfr gene amplification in methotrexate-resistant cell lines is relative to the dhfr gene dosage of methotrexate-sensitive parental lines which, by definition, have a dhfr gene dosage of 1X.…”

Section: A T E R I a L S A N D M E T H O D Smentioning

confidence: 99%

“…CCI -derived methotrexate-resistant suhc1oiie.s CC1 cells are a polyclonal population of NIH 3T3 cells carrying the retroviral vector pzIPNeoSV(X)l without an expressed gcne. The methotrexate-resistant subclones were obtained in single-step in-vitro selections for resistance to 100 n M methotrexate (Wani & Snapka 1989). The cells in this series are: CCl (parental, polyclonal, methotrexate-sensitive, dhfr gene dosage IX), CCl(1) a methotrexatc-sensitive subclone of CCI which shows much higher levels of DNA and RNA per cell, C C l R l (dhfr gcne dosage lox), CClR2 (dhfr gene dosage 12X), CClR3 (dhfr gene dosage 14X), CClRS (dhfr gene dosage 10X).…”

Section: Cell Lines and Selections For Methotrexate Resistancementioning

confidence: 99%

“…To confirm the relationship between unbalanced growth and gene amplification, another series of cell lines selected for methotrexate-resistance was studied. The parental CC1 cells and their methotrexate-resistant subclones have been previously described (Wani & Snapka 1989). All of the methotrexate-resistant CC1 subclones represent different single-step dhj?…”

Section: Cc1 Seriesmentioning

confidence: 99%

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Unbalanced growth in mouse cells with amplified dhfr genes

et al. 1997

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When grown in the absence of methotrexate, cells carrying unstably amplified dihydrofolate reductase (dhfr) genes have a growth disadvantage that is a function of their level of gene amplification. Although this growth disadvantage is thought to drive the loss of unstably amplified dhfr genes in the absence of methotrexate, its mechanism is not understood. The present studies of murine cell lines with different levels of dhfr gene amplification demonstrate that such cells experience increased unbalanced growth (excess RNA and protein content relative to DNA content) with increased levels of dhfr gene amplification. Stathmokinetic analysis of a cell line with unstably amplified dhfr genes showed that the unbalanced growth was associated with a very low rate of G1/S transit, which suggests that amplified DNA sequences may activate a cell cycle checkpoint at the G1/S boundary. Hydroxyurea, which is known to induce rapid elimination of amplified genes at sub-cytotoxic concentrations, also inhibits the cell cycle at the G1/S transition and causes unbalanced growth. Earlier work has shown that hydroxyurea selectively targets those cells within the heterogeneous drug resistant cell populations which have the highest amplified gene dosage. The finding that unstable gene amplification and hydroxyurea have similar effects on the cell suggests that hydroxyurea may achieve this selective targeting by pushing those cells with the highest levels of gene amplification over a critical stress threshold to cause growth arrest or cell death.

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Section: A T E R I a L S A N D M E T H O D Smentioning

confidence: 99%

Section: Cell Lines and Selections For Methotrexate Resistancementioning

confidence: 99%

Section: Cc1 Seriesmentioning

confidence: 99%

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