Upregulation of asparagine synthetase fails to avert cell cycle arrest induced by L-asparaginase in TEL/AML1-positive leukaemic cells.
L-Asparaginase is a standard component in chemotherapy of childhood acute lymphoblastic leukaemia (ALL). Leukaemic cells carrying TEL/AML1 fusion gene are more sensitive to treatment with L-asparaginase compared to other subtypes of ALL. We demonstrate in vitro the prolonged growth suppression of TEL/AML1[+] cells compared to TEL/AML1[-] leukaemic cells after L-asparaginase treatment simulating treatment protocol. Cell cycle analysis revealed TEL/AML1[+] cells to accumulate in G1/G0 phase (81-98%) compared to TEL/AML1[-] cells (47-60%). Quantitative analysis of asparagine synthetase (AsnS) expression showed the ability of TEL/AML1[+] cells to increase AsnS mRNA levels after L-asparaginase treatment to the same extent as TEL/AML1[-] leukaemic and nonleukaemic lymphoid cells. We hypothesise that TEL/AML1[+] cells are unable to progress into the S phase of cell cycle under nutrition stress caused by L-asparaginase, despite the ability of AsnS upregulation. Significantly higher expression of AsnS was found in untreated leukaemic cells from children with TEL/AML1[+] ALL (n=20) in comparison with the group of age-matched children with ALL bearing no known fusion gene (n=25; P=0.0043). Interestingly, none of the TEL/AML1[+] patients with high AsnS level relapsed, whereas 10/15 patients with AsnS below median relapsed (P=0.00028). Therefore, high AsnS levels in TEL/AML1[+] patients correlate with better prognosis, possibly reflecting the stretched metabolic demand of the lymphoblast.
Krejci
O
O
CLIP - Childhood Leukaemia Investigation Prague, Prague, Czech Republic. ondrej.krejci@lfmotol.cuni.cz
Starkova
J
J
Otova
B
B
Madzo
J
J
Kalinova
M
M
Hrusak
O
O
Trka
J
J
D001215:Asparaginase / Q000627:therapeutic use*; D001217:Aspartate-Ammonia Ligase / Q000378:metabolism*; D001853:Bone Marrow; D002453:Cell Cycle; D002648:Child; D002675:Child, Preschool; D050676:Core Binding Factor Alpha 2 Subunit; D006801:Humans; D009364:Neoplasm Recurrence, Local / Q000378:metabolism / Q000473:pathology; D015514:Oncogene Proteins, Fusion / Q000378:metabolism*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D000097764:ETS Translocation Variant 6 Protein
D001215:Asparaginase; D001217:Aspartate-Ammonia Ligase; D050676:Core Binding Factor Alpha 2 Subunit; D015514:Oncogene Proteins, Fusion; D012333:RNA, Messenger; D012334:RNA, Neoplasm; C102421:TEL-AML1 fusion protein; D000097764:ETS Translocation Variant 6 Protein