[Recent advances in molecular cytogenetics of leukemia]

Recent advances in molecular cytogenetics of leukemia is reported with special reference to the pathogenesis, diagnosis, prognosis, and potential gene therapy. Regarding leukemogenesis, we found that neocarzinostatin induced a variety of deletions and reciprocal translocations. Among these random chromosome abnormalities, two reciprocal translocations which were specific for certain leukemias could be observed; t(11;14)(q13;q32) and t(7;11)(p15p13). This fact suggests that a translocation carrying oncogene rearrangement may be of potential relevance to the leukemogenesis. The success in making a subgroup (FAB classification) identified a number of subtype-specific translocations in leukemias. It has been suggested that an initiation or progression-associated event is mediated through a gross chromosomal change. The molecular characterization of chromosomal rearrangement leads to the identification of genes involved in leukemia. Our recent works in molecular cytogenetics of chronic myelogenous leukemia (CML), acute lymphoblastic leukemia (ALL), FAB-M3 and -M4 were shown in this article. Since rearrangement of relevant genes were cloned, PCR made it feasible to detect minimal residual disease at 10(-6) level after intensive treatment or bone marrow transplantation for CML, Ph-positive ALL, M3 and approximately half of childhood leukemia. Recently developed fluorescent in situ hybridization (FISH) using specific probes can visualize certain chromosomes or chromosomal segments. Ph translocation, for instance, is now demonstrated as three spot-signals in interphase nuclei using YAC (yeast artificial chromosome)-BCR clone. Lastly, the use of antisense oligonucleotides for the BCR-ABL junctions should result in the inhibition of growth of CML clone. The strategy using antisense molecules may be very powerful tool in the gene-targeting therapy for human neoplasms.