Asparagine synthetase expression alone is sufficient to induce l-asparaginase resistance in MOLT-4 human leukaemia cells

Abstract

Childhood acute lymphoblastic leukaemia (ALL) is treated by combination chemotherapy with a number of drugs, always including the enzyme l-asparaginase (ASNase). Although the initial remission rate is quite high, relapse and associated drug resistance are a significant problem. In vitro studies have demonstrated increased asparagine synthetase (AS) expression in ASNase-resistant cells, which has led to the hypothesis that elevated AS activity permits drug-resistant survival. The data presented show that not only is elevated AS expression a property of ASNase-resistant MOLT-4 human leukaemia cells, but that short-term (12h) treatment of the cells with ASNase causes a relatively rapid induction of AS expression. The results also document that the elevated expression of AS in ASNase-resistant cells is not fully reversible, even 6 weeks after ASNase removal from the culture medium. Furthermore, ASNase resistance, assessed as both drug-insensitive cell growth rates and decreased drug-induced apoptosis, parallels this irreversible AS expression. Mimicking the elevated AS activity in ASNase-resistant cells by overexpression of the human AS protein by stable retroviral transformation of parental MOLT4 cells is sufficient to induce the ASNase-resistance phenotype. These data document that ASNase resistance in ALL cells is a consequence of elevated AS expression and that although other drug-induced metabolic changes occur, they are secondary to the increased asparagine biosynthetic rate.

A critical electrostatic interaction mediates inhibitor recognition by human asparagine synthetase

“…For example, in vitro studies with U937 cells demonstrated that ASNase-sensitive cells can be made resistant by persistent exposure to increasing levels of sublethal doses of the drug, and constitutive expression of ASNS in a human ALL cell line (MOLT-4) conferred ASNase-resistance onto sensitive parental cells. 14 Additional evidence has been provided from recent work by our group, which demonstrated that incubation of ASNase-resistant MOLT-4 cells with ASNase and the adenylated sulfoximine derivative 1 (Fig. 1) suppresses cell proliferation.…”

Effects of Naturally Occurring Polymethyoxyflavonoids on Cell Growth, P-Glycoprotein Function, Cell Cycle, and Apoptosis of Daunorubicin-Resistant T Lymphoblastoid Leukemia Cells

“…MOLT-4, a human T lymphoblastoid leukemia cell line, has been used extensively for studies of leukemia cell biology and anti-leukemia therapy (10,11). We have developed an MDR cell line MOLT-4/daunorubicin (DNR) from a T lymphoblastoid leukemia MOLT-4 cell line by exposing the parent cells to stepwise increasing concentrations of DNR over 3 months (12).…”

Genetic alterations determine chemotherapy resistance in childhood T‐ALL: modelling in stage‐specific cell lines and correlation with diagnostic patient samples

“…Experimentally induced drug resistance in several leukaemic cell lines through the sequential escalation of drug dosage has provided insights into the underlying mechanisms of treatment failure (Beck, 1983; Den Boer et al , 1998; Sonneveld, 2000; Aslanian et al , 2001; Liu et al , 2002; Efferth et al , 2006; Munteanu et al , 2006). Nevertheless, only the CCRF‐CEM, MOLT‐4 and Jurkat T‐ALL cell lines have been developed to show drug resistance to anthracyclines, vinca alkaloids, glucocorticoids, or l ‐asparaginase ( l ‐asp).…”