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 .

 

 

 

 
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