Frequent deletions at 12q14.3 chromosomal locus in adult acute lymphoblastic leukemia

Cytogenetic abnormalities at the 12q12-q14 chromosomal locus are rarely detected in acute lymphoblastic leukemia (ALL). To examine submicroscopic deletions at this locus, we analyzed 78 adult precursor B- and T-cell ALL cases [27 with Philadelphia chromosome (Ph)-negative B-cell ALL, 20 with Ph-negative B-cell ALL with expression of one or two myeloid markers, 18 with Ph-positive B-cell ALL, and 13 with T-cell ALL] using a panel of 13 microsatellite (MST) markers that span the 12q12-q14.3 region. The status of MST markers was evaluated by use of polymerase chain reaction performed with fluorescence-labeled primers and automated fragment analysis. The MST marker analyses showed submicroscopic deletions at the 12q14.3 locus in 20 of the 78 ALL cases (26%). The frequency of deletions was highest in Ph-negative B-cell ALL ( 13 of 27, 48%) compared with that in Ph-negative B-cell ALL with expression of myeloid markers (4 of 20, 20%), Ph-positive B-cell ALL (2 of 18, 11%), and T-cell ALL (1 of 13, 8%). Deletion frequencies of MST markers along the 12q12-q14.3 locus suggest that the targeted gene of deletion is located within a 170-kb region bordered by the markers D12S1504 (approximately 65 kb upstream of HMGA2) and D12S1509 (in intron 3 of HMGA2) at the 12q14.3 locus. These submicroscopic deletions at the 12q14.3 locus may play a role in the pathogenesis of ALL, particularly in Ph-negative precursor B-cell ALL.