TEL deletion analysis supports a novel view of relapse in childhood acute lymphoblastic leukemia.
OBJECTIVE
TEL (ETV6)-AML1 (RUNX1) chimeric gene fusions are frequent genetic abnormalities in childhood acute lymphoblastic leukemia (ALL). They often arise prenatally as early events or initiating events and are complemented by secondary postnatal genetic events of which deletion of the non-rearranged, second TEL allele is the most common. This consistent sequence of molecular pathogenesis facilitates an analysis of the clonal origins of relapse in this leukemia, which has some unusual clinical features.


METHODS
We compared the boundaries, by microsatellite mapping, of TEL deletions at relapse versus diagnosis in 15 informative patients. Moreover, we compared the relatedness of diagnostic and relapse clones using immunoglobulin and T-cell receptor genes rearrangements and clonotypic TEL-AML1 genomic fusion.


RESULTS
Five patients retained the apparent same size TEL deletion, seven had larger deletions, and three had smaller deletions at relapse. In all of the cases evaluated, the clonal relatedness of diagnostic and relapse cells was confirmed by the retention of clonotypic TEL-AML1 genomic sequence and/or at least one identical immunoreceptor gene rearrangement.


CONCLUSIONS
These data provide further evidence that TEL deletions are secondary to TEL-AML1 fusions in ALL. They are compatible with the novel idea that in at least some cases of childhood ALL, remission occurs with persistence of a preleukemic "fetal" clone, and subsequent relapse reflects the emergence of a new subclone from this reservoir after an independent "second hit," i.e., independent TEL deletion. To our knowledge, the study is the most extensive and comprehensive analysis of the relationship between diagnostic and relapse clones in childhood ALL presented thus far.
Leukemia Research Fund Centre for Cell and Molecular Biology, Institute of Cancer Research, London, United Kingdom. jan.zuna@lfmotol.cuni.cz
Jan
J
Zuna
Anthony M
AM
Ford
Martina
M
Peham
Naina
N
Patel
Vaskar
V
Saha
Cornelia
C
Eckert
Joachim
J
Köchling
Renate
R
Panzer-Grümayer
Jan
J
Trka
Mel
M
Greaves
D019677:Artificial Gene Fusion; D002648:Child; D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins / Q000235:genetics*; D030541:Databases, Genetic; D015329:Gene Rearrangement, T-Lymphocyte; D006801:Humans; D018895:Microsatellite Repeats; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D050783:Proto-Oncogene Proteins c-ets; D012008:Recurrence; D012097:Repressor Proteins / Q000235:genetics*; D017384:Sequence Deletion; D014157:Transcription Factors / Q000235:genetics*; D000097764:ETS Translocation Variant 6 Protein
D050676:Core Binding Factor Alpha 2 Subunit; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D012097:Repressor Proteins; D014157:Transcription Factors; D000097764:ETS Translocation Variant 6 Protein; C493728:RUNX1 protein, human