Translocations at chromosomal band Hq23 characterize most de novo
acute lymphoblastic leukemia* (ALL) of infants, acute myeloid leukemias
(AMD of infants and young children, and secondary AMLs following
epipodophyllotoxin exposure. The chromosomal breakpoints at Ilq23
have been cloned from isolated cases off/c novo ALL and AMI . Using an
859-base pair /¡«millfragment of human ALL-1 complementary DNA
that recognizes the genomic breakpoint region for de novo ALL and AML, we investigated two cases of secondary AML that followed etoposidetreated
primary B-lineage ALL. In the first case, the translocation oc
curred between chromosomes 9 and 11 and the breakpoint at Hq23 lo
calized to the same 9-kilobase region of the ALL-1 gene that is disrupted
in most of the de novo leukemias. In the second case the translocation was between chromosomes 11 and 19. The breakpoint occurred outside of the
ALL-1 breakpoint cluster region.