IMMUNOGLOBULIN (IG) AND T-CELL RECEPTOR (TCR) GENE
REARRANGEMENTS AS STABLE PCR TARGETS FOR DETECTION OF MINIMAL RESIDUAL
DISEASE (MRD) IN PEDIATRIC PRECURSOR-B-ALL
Szczepański T1, 2,
Willemse MJ1, Van der Velden VHJ1, and Van Dongen JJM
1
1Department
of Immunology, Erasmus University Medical Center, Rotterdam, The
Netherlands and 2Department of Pediatric Hematology and
Chemotherapy, Silesian Medical Academy, Zabrze, Poland
Objective:
Precursor-B acute lymphoblastic leukemias (ALL) are clonal proliferations
assumed to be counterparts of normal BM precursor-B-cells. Therefore,
clonal Ig and TCR gene rearrangements are "fingerprint-like"
markers of each leukemia.
Study group and methods: We
studied the configuration of the Ig and TCR genes in 233 pediatric
precursor-B-ALL patients with Southern blot analysis (employing multiple
DNA probes for Ig and TCR genes) and heteroduplex PCR analysis (employing
multiple primer sets for IGH, IGK, TCRG, and TCRD). 91
children were subjected to detailed comparative analysis of Ig/TCR gene
configuration at diagnosis and at relapse of ALL.
Results: We were able to characterize in detail Ig and
TCR gene rearrangement patterns in pediatric precursor-B-ALL. The
frequencies of particular gene rearrangements and their stability at
relapse are summarized in the table.
Gene
|
Rearrangement type
|
Frequency
|
Stability (mono /
oligoclonal)
|
IGH
|
Vh-Jh
|
93%
|
88% / 47%
|
|
Dh-Jh
|
20%
|
57% / 38%
|
|
total IGH
|
98%
|
85% / 44%
|
IGK
|
Vk-Kde
|
45%
|
95% / 40%
|
|
intron RSS-Kde
|
25%
|
86% / 0%
|
|
total Kde
|
50%
|
95% / 40%
|
TCRG
|
Vg-Jg
|
55%
|
75%
|
TCRD
|
Vd2-Dd3 or
Dd2-Dd3
|
40%
|
86% / 26%
|
Conclusion: With
combined Southern blot and PCR analyses it is possible to identify Ig/ TCR
gene rearrangements as MRD-PCR targets in virtually all pediatric
precursor-B-ALL. Moreover, most clonal Ig and TCR gene rearrangements are
preserved at relapse. Never-theless, our data show that reliable MRD
monitoring needs at least two PCR targets, preferably monoclonal, end-stage
rearrangements, which have a high stability. We propose a stepwise strategy for MRD monitoring (monoclonal targets
® TCRG ® oligoclonal IGH), which
would enable successful detection of relapse in the vast majority (93%) of
precursor-B-ALL .