What question did this study set out to answer?

Determine the biochemical mechanisms driving acquired resistance to amethopterin in cultured mammalian tumor cells.

March 1, 1961Journal of Biological ChemistryOpen Access

Relation of Folic Acid Reductase to Amethopterin Resistance in Cultured Mammalian Cells

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Authors

MHMaire HakalaOulu University Hospital SZSigmund F. ZakrzewskiClarendon College CNCharles A. NicholRoswell Park Comprehensive Cancer Center

Discussion

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Implication

Cell culture study demonstrates marked folic acid reductase overproduction in amethopterin-resistant Sarcoma 180 lines, indicating increased enzyme quantity underlies drug resistance.

Key Points

Determine the biochemical mechanisms driving acquired resistance to amethopterin in cultured mammalian tumor cells.
Cultured Sarcoma 180 cells in hypoxanthine-supplemented medium (AH cells) or thymidine-supplemented medium (AT cells) to establish amethopterin-resistant lines.
Assessed stability of resistance over time, growth response to folic and folinic acid, and cross-resistance to other antimetabolites.
Quantified folic acid reductase enzyme levels and measured kinetic properties, including the Michaelis constant (Km) for folic acid.
Amethopterin resistance reached 67-fold in AH cells and 174-fold in AT cells, which correlated with a 65-fold and 155-fold increase in folic acid reductase levels, respectively.
Enzyme kinetics remained unchanged across lines, with the Michaelis constant (Km) for folic acid staying between 1.1 × 10⁻⁵ M and 1.25 × 10⁻⁵ M, showing that elevated enzyme quantity rather than altered affinity drove resistance.
Resistant lines retained baseline growth requirements for folate precursors and showed unchanged sensitivity to 6-mercaptopurine, 6-diazo-5-oxo-L-norleucine, and 5-fluorodeoxyuridine.

Cite This Study

Hakala et al. (1961) studied this question.

synapsesocial.com/papers/6a866d3f0e354d9fd799ade8 https://doi.org/10.1016/s0021-9258(18)64337-6

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March 1, 1961Journal of Biological ChemistryOpen Access

Relation of Folic Acid Reductase to Amethopterin Resistance in Cultured Mammalian Cells

View Full Paper

Ask AI

Bookmark

Authors

MHMaire HakalaOulu University Hospital SZSigmund F. ZakrzewskiClarendon College CNCharles A. NicholRoswell Park Comprehensive Cancer Center

Discussion

Member takes

Implication

Cell culture study demonstrates marked folic acid reductase overproduction in amethopterin-resistant Sarcoma 180 lines, indicating increased enzyme quantity underlies drug resistance.

Key Points

Determine the biochemical mechanisms driving acquired resistance to amethopterin in cultured mammalian tumor cells.
Cultured Sarcoma 180 cells in hypoxanthine-supplemented medium (AH cells) or thymidine-supplemented medium (AT cells) to establish amethopterin-resistant lines.
Assessed stability of resistance over time, growth response to folic and folinic acid, and cross-resistance to other antimetabolites.
Quantified folic acid reductase enzyme levels and measured kinetic properties, including the Michaelis constant (Km) for folic acid.
Amethopterin resistance reached 67-fold in AH cells and 174-fold in AT cells, which correlated with a 65-fold and 155-fold increase in folic acid reductase levels, respectively.
Enzyme kinetics remained unchanged across lines, with the Michaelis constant (Km) for folic acid staying between 1.1 × 10⁻⁵ M and 1.25 × 10⁻⁵ M, showing that elevated enzyme quantity rather than altered affinity drove resistance.
Resistant lines retained baseline growth requirements for folate precursors and showed unchanged sensitivity to 6-mercaptopurine, 6-diazo-5-oxo-L-norleucine, and 5-fluorodeoxyuridine.

Cite This Study

Hakala et al. (1961) studied this question.

synapsesocial.com/papers/6a866d3f0e354d9fd799ade8 https://doi.org/10.1016/s0021-9258(18)64337-6

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