tal-1 deletions in T-cell acute lymphoblastic leukemia as PCR target for detection of minimal residual disease.
Polymerase chain reaction (PCR) techniques based on amplification and identification of leukemia-specific DNA sequences provide a sensitive diagnostic method for detection of minimal residual disease (MRD) with a detection limit of 10(-5) to 10(-6) (1-10 malignant cells in 10(6) normal cells). To date, the main leukemia-specific DNA sequences used as PCR targets in detection of MRD are breakpoint fusion regions of chromosome translocations and junctional regions of rearranged immunoglobulin (Ig) or T-cell receptor (TcR) genes. The recently identified tal-1 deletions involving the sil and tal-1 genes, provide a potential MRD-PCR target. tal-1 deletions are site-specific because they are mediated via recombination signal sequences homologous to Ig/TcR genes. In line with this homology, tal-1 deletions also show random insertion and deletion of nucleotides at their breakpoints, resulting in highly variable breakpoint fusion regions. The fusion region diversity can be applied to design patient-specific oligonucleotide probes. Our Southern blot analyses of a large series of 313 acute leukemias with a specific tal-1 deletion probe (SILDB) demonstrated that tal-1 deletions exclusively occur in T-cell acute lymphoblastic leukemia (T-ALL) and not in precursor B-ALL or acute non-lymphocytic leukemias. In addition, we did not detect tal-1 deletions in normal blood cells and normal thymocytes by PCR analysis. The diversity observed in tal-1 deletion fusion regions with an average insertion and deletion of approximately 7 and approximately 6 nucleotides, respectively, allowed us to design fusion-region-specific probes. The specificity of the fusion-region probes was proven and the detection limit of the MRD-PCR technique was tested in a series of dilution experiments. The observed detection limit of 10(-5) indicates that tal-1 deletions in T-ALL represent ideal leukemia-specific PCR targets for detection of MRD.
Breit
T M
TM
Department of Immunology, Erasmus University/University Hospital Dijkzigt, Rotterdam, The Netherlands.
Beishuizen
A
A
Ludwig
W D
WD
Mol
E J
EJ
Adriaansen
H J
HJ
van Wering
E R
ER
van Dongen
J J
JJ
D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D015139:Blotting, Southern; D004268:DNA-Binding Proteins / Q000235:genetics*; D017353:Gene Deletion; D006801:Humans; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000175:diagnosis* / Q000235:genetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011519:Proto-Oncogenes; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D011518:Proto-Oncogene Proteins; D000073942:T-Cell Acute Lymphocytic Leukemia Protein 1; D014157:Transcription Factors; C067143:TAL1 protein, human