Amplification of AML1 gene is present in childhood acute lymphoblastic leukemia but not in adult, and is not associated with AML1 gene mutation

Abstract

The AML1/CBFA2/RUNX1 gene is the target of many recurrent translocations seen in different leukemia subtypes. The t(12;21)(p13;q22) is the most frequent translocation observed in childhood B acute lymphoblastic leukemia (ALL), occurring in 20% to 25% of cases. In adult ALL this rearrangement is scarce. Another route of AML1 deregulation could be point mutations in the runt domain. We now report on AML1 amplification in two cases of childhood ALL, found in a series of 107 consecutive children with B-lineage ALL analyzed by fluorescence in situ hybridization (FISH). A parallel analysis of 42 adult B-ALL failed to detect any AML1 rearrangement by FISH. The two patients with AML1 amplification were further analyzed using molecular techniques. SSCP analysis did not detect any mutation. Furthermore, direct sequencing of the cDNA did not reveal any mutation. In conclusion, AML1 amplification seems to be observed only in childhood ALL and is not associated with AML1 gene mutation. Other mechanisms, such as gene dosage effects could be hypothesized.

Amplification or duplication of chromosome band 21q22 with multiple copies of the AML1 gene and mutation of the TP53 gene in therapy-related MDS and AML

“…Patient A had a 734G-A base change resulting in a G245D aminoacid substitution, patient B had a IVS5-2 A-C base change resulting in disruption of a splice site, and patient C had a 731G-T base change resulting in a G245V amino-acid substitution (Table 1). Similar to what has been reported in childhood ALL, 19 point mutations of AML1 were not detected in any of the three patients.…”

“…It is of interest that mutations of TP53 and complex karyotypes are also very common in many solid tumors. (19), and two AML1 signals on the der(21).…”

“…Patient III disclosed four apparently normal copies of AML1 on different chromosome arms: One copy was on the normal chromosome 21, another was located on a der (19) to which a segment of 21q was translocated, and two copies were located on a der(21) to which material from chromosome 19 was inserted between two segments of 21q each containing a copy of AML1 (Figure 1e and f). In addition, five copies of AML1 were detected in a large proportion of interphase cells.…”

New mechanisms of AML1 gene alteration in hematological malignancies

“…cDNA was synthesized from 1 g of total RNA in a 20 l reaction mixture as previously described. 34 Three PCR amplifications were performed in parallel; each containing 2 l of cDNA (corresponding to 100 ng of total RNA), 1× TaqGold reaction buffer (Applied Biosystems), 1.5 mM MgCl 2 , 250 M each dATP, dCTP, dGTP, dTTP (Pharmacia), 0.5 U of AmpliTaq Gold polymerase (Applied Biosystems) and 50 pmol of each primer. Thermocycling conditions used were 12 min at 94°C followed by 35 cycles of denaturation at 94°C for 1 min, annealing at 60°C for 1 min, extension at 72°C for 1 minute and a final extension step of 5 min at 72°C.…”

“…The coding sequence of the AML1 cDNA was sequenced as previously reported. 34 Briefly, total RNA was extracted from frozen aliquots of 10 7 bone marrow cells with Trizol reagent (Invitrogen, Life Technologies, Karlsruhe, Germany) according to the manufacturer's instruction. RNA pellets were resuspended in 10 l of RNAse-free water and quantity was estimated by ultraviolet spectrofluorometry.…”