MOLECULAR HETEROGENEITY OF VARIANT PHILADELPHIA TRANSLOCATIONS IN CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA

In acute lymphoblastic leukemia (ALL), it is unclear whether variant P hiladelphia (Ph) translocations have the same molecular and clinical i mplications as the classical translocation. Two children with Ph+ ALL with variant translocations are described. One, in whom cytogenetic re mission was not achieved, had evidence of translocation of c-abl to ch romosome 22, rearrangement of minor breakpoint cluster region (mBCR) a nd expression of hybrid bcr/abl transcripts. In the other case, no gen e rearrangement was found and complete remission was achieved. Variant Ph translocations in childhood ALL are heterogeneous at the molecular level. Molecular studies coupled with observations of clinical outcom e are needed in larger numbers of such children to determine whether p oor clinical response correlates with bcr/abl involvement and to allow planning of appropriate therapeutic strategies.