Presence of heterozygous ATM deletion may not be critical in the primary response of chronic lymphocytic leukemia cells to fludarabine.
OBJECTIVE
Abnormalities of the TP53 or ATM, cooperating tumor-suppressor genes, significantly worsen the treatment options for chronic lymphocytic leukemia (CLL) patients. Although the aberrations seem to be mutually exclusive in this leukemia, inactivation of the former gene leads to worse prognosis. We tested the in vitro sensitivity of the CLL samples with heterozygous ATM deletion to fludarabine and combination of fludarabine and rituximab; the responses were compared with the TP53-abnormal and wild-type (wt) cells to delimitate relative significance of ATM deletion.


METHODS
In vitro analysis was performed on fifty-nine characterized CLL samples using viability assay WST-1. Western blot and real-time RT-PCR were used to monitor the activation of the ATM/p53 pathway.


CONCLUSIONS
At the clinically relevant concentration of fludarabine, TP53-abnormal samples exhibited markedly higher resistance to fludarabine than the remaining CLL samples (P = 0.012); cohort with ATM deletion was not more resistant than wt cells. A similar induction of the p53 protein and its downstream target genes PUMA and BAX in ATM-deleted and wt cells confirmed that the former subgroup has preserved a critical pro-apoptotic response. Proportions of the samples, which had been sensitized to fludarabine by rituximab pretreatment, were insignificantly lower (P = 0.22) in the TP53-abnormal and ATM-deleted subgroups compared to the wt cases (30%; 29%; 50%, respectively). The presence of ATM (11q22-23) deletion in the CLL cells should not be considered an indication of resistance to fludarabine or its combination with rituximab.
Cejkova
Sona
S
Department of Internal Medicine - Hematooncology, University Hospital and Faculty of Medicine, Masaryk University, Brno, Czech Republic.
Rocnova
Ludmila
L
Potesil
David
D
Smardova
Jana
J
Novakova
Vera
V
Chumchalova
Jitka
J
Zezulkova
Dita
D
Borsky
Marek
M
Doubek
Michael
M
Brychtova
Yvona
Y
Pospisilova
Sarka
S
Klabusay
Martin
M
Mayer
Jiri
J
Trbusek
Martin
M
D000970:Antineoplastic Agents / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics*; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics*; D017353:Gene Deletion; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology
D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D014740:Vidarabine; C024352:fludarabine