Trisomy 21 is a recurrent secondary aberration in childhood acute lymphoblastic leukemia with TEL/AML1 gene fusion

✍ Scribed by Ivan F. Loncarevic; Barbara Roitzheim; Jutta Ritterbach; Susanne Viehmann; Arndt Borkhardt; Fritz Lampert; Jochen Harbott

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 140 KB
• Volume: 24
• Category: Article
• ISSN: 1045-2257
• DOI: 10.1002/(sici)1098-2264(199903)24:3<272::aid-gcc13>3.0.co;2-u

✦ Synopsis

TEL/AML1 gene fusion is the most frequent genetic lesion in pediatric acute lymphoblastic leukemia (ALL). It occurs as a consequence of the cryptic chromosomal translocation t(12;21)(p13;q22). In a cohort of 50 RT-PCR-positive TEL/AML1 patients, karyotype examination by GTG banding and fluorescence in situ hybridization (FISH) allowed us to identify chromosome anomalies in addition to the already existing t(12;21). Secondary aberrations were found in 29 out of 41 patients (71%) at initial diagnosis and in all 9 patients with relapse. Structural rearrangements affected chromosome arms 2p, 2q, 5q, 9p, 12p (n ϭ 2), 6q, 11p (n ϭ 3), and 21q (n ϭ 4). An extra chromosome 21 was found to be the most frequent anomaly. It was detected in 6 out of 41 patients at initial diagnosis (15%) and in 7 out of the 9 patients at relapse. No karyotype with trisomy 21 exceeded 47 chromosomes. Gain of chromosome 21 was the sole anomaly in GTG-banding analysis in 2/41 patients at initial diagnosis and in 4/9 at relapse. Notably, chromosome painting analysis performed in 11 out of the 13 patients with an extra chromosome 21 revealed duplication of the normal chromosome 21 in 8, and duplication of der(21)t(12;21) in 3 patients. Furthermore, gain of der(21)t(12;21) chromosome was confined exclusively to the relapse patients.