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  • Title: Biochemical characterization of U937 cells resistant to L-asparaginase: the role of asparagine synthetase.
    Author: Kiriyama Y, Kubota M, Takimoto T, Kitoh T, Tanizawa A, Akiyama Y, Mikawa H.
    Journal: Leukemia; 1989 Apr; 3(4):294-7. PubMed ID: 2564453.
    Abstract:
    A human histiocytic lymphoma cell line, U937, is highly sensitive to L-asparaginase with an ID50 of about 0.0001 U/ml after 72 hr of culture. When U937 cells were made resistant to either L-asparaginase (1 U/ml) or asparagine deprivation, the activity of asparagine synthetase increased to 80- or 7-fold of the wild type, respectively. The phenotype of the resistance to L-asparaginase turned out to be stable under nonselective conditions for over several months. The hybrids between L-asparaginase sensitive (Molt4) and resistant (HL-60) cell lines revealed the latter phenotype in terms of L-asparaginase sensitivity and the activity of asparagine synthetase. Furthermore, U937 cells resistant to L-asparaginase could survive in glutamine-free media with 1.5-fold elevation of glutamine synthetase activity. These results altogether clarify the role of asparagine synthetase in L-asparaginase toxicity and have a good implication for the clinical use of L-asparaginase.
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