Abnormalities of the Long Arm of Chromosome 6 in Childhood Acute Lymphoblastic Leukemia

To determine the biologic significance of the structural rearrangements of the long arm of chromosome 6(6q) in acute lymphoblastic leukemia (ALL) at diagnosis, we stud-ied 412 consecutive children whose leukemic cell chromo-somes had been completely banded and identified 45 (1 1 %) children with this abnormality. The 45 cases were divided into del(6q) only (n = 11 1, del(6q) and numerical abnormal-ities (n = 41, del(6q) and structural abnormalities (n = 23). and 6q translocations (n = 7). The breakpoints of del(6q) were subgrouped: del(6)(ql5q21) in 11 cases, del(6) (q13q21) in six, de1(6)(q21 q23) in four, del(6)(ql5) in four, de1(6)(q15q23) in three, and other deletions in 10 cases. Notably, all these deletions encompassed the 6q21 band, suggesting that this might be the locus of a recessive tumor suppressor gene, the absence of which contributes t