Cross-lineage T cell receptor gene rearrangements occur in more than ninety percent of childhood precursor-B acute lymphoblastic leukemias: alternative PCR targets for detection of minimal residual disease
T. Szczepanski et al., Cross-lineage T cell receptor gene rearrangements occur in more than ninety percent of childhood precursor-B acute lymphoblastic leukemias: alternative PCR targets for detection of minimal residual disease, LEUKEMIA, 13(2), 1999, pp. 196-205
A large series of 202 childhood precursor-B cell acute lymphoblastic leukem
ia (ALL) patients was analyzed by Southern blotting (SB) for cross-lineage
rearrangements and/or deletions in the T cell receptor TCRB, TCRG and TCRD
loci. In 93% (187/201) of the precursor-B-ALL patients one or more genes we
re rearranged and/or deleted. TCRB gene rearrangements were found in 35% (6
9/196), TCRG gene rearrangements in 59% (113/192), TCRD gene rearrangements
in 55% (112/202), and isolated monoallelic or biallelic deletions of TCRD
loci in 34% (68/202) of the cases. TCRB gene rearrangements involved exclus
ively the J beta 2 locus with complete V(D)J beta 2 joinings in 53% of gene
rearrangements and incomplete D beta-J beta 2 gene rearrangements in 33%.
TCRG gene rearrangements frequently occurred on both alleles (65% of cases)
and in approximately 70% concerned rearrangements to J gamma 1 gene segmen
ts. Most rearranged TCRD alleles (80%) represented incomplete V delta 2-D d
elta 3 or D delta 2-D delta 3 gene rearrangements, while the remaining TCRD
gene rearrangements remained unidentified. Subsequently, we evaluated, whe
ther heteroduplex PCR analysis of rearranged TCRG and TCRD genes can be use
d for reliable identification of PCR targets for detection of minimal resid
ual disease (MRD). The concordance between SE and heteroduplex PCR analysis
for detection of the various types of clonal TCRG and TCRD gene rearrangem
ents ranged between 78% and 87%. The discrepancies could be assigned to the
presence of 'atypical' TCRD gene rearrangements or translocations only det
ectable by SB, but also to efficient PCR-based detection of rearrangements
derived from small subclones, which are difficult to detect with SB. Indica
tions for oligoclonality were observed in 38% and 30% of patients with TCRG
and TCRD gene rearrangements, respectively, which is comparable to the fre
quency of oligoclonality in IGH locus. Based on the combined data it was po
ssible to reduce the broad panel of six TCRD and 12 TCRG primer combination
s for MRD studies to two TCRD combinations (V delta 2-D delta 3 and D delta
2-D delta 3) and six TCRG combinations (V gamma I, V gamma II, V gamma IV
family-specific primers with J gamma 1.1/2.1 and J gamma 1.3/2.3 primers) r
esulting in the detection of 80% and 97% of all TCRD and TCRG gene rearrang
ements, respectively. Finally, the heteroduplex PCR data indicate that MRD
monitoring with TCRG and/or TCRD targets is possible in approximately 80% o
f childhood precursor-B-ALL patients; similar to 55% of patients even have
two TCRG and/or TCRD targets.