DIFFERENTIAL CHEMOSENSITIVITY OF LEUKEMIC-CELLS IN THE MYELOID AND LYMPHOID PHASES OF STEM-CELL LEUKEMIA (A CASE-REPORT)

A five-year-old girl, initially diagnosed as having acute lymphoblasti c leukemia (ALL; FAB - L1) relapsed with ALL 4 months after completion of chemotherapy (BFM 83). The initial ALL presentation and subsequent ALL relapse were analyzed using conventional morphology, cytochemistr y, cytogenetics and immunophenotyping. The results were consistent wit h a diagnosis of B-lymphocyte precursor ALL. Bone marrow leukemic cell s revealed a 46, XX karyotype at diagnosis and a 46, XX, del(7) (q22; qter) when the girl first relapsed. The case was managed with a BFM RE Z-ALL 90 protocol. Upon completion of the first cycle of the protocol, severe myelosuppression developed. This was treated with GM-CSF. Thre e days later however, GM-CSF was stopped because the WBC reached 1.1 x 10(9) per liter with 60% of blasts in peripheral blood. Laboratory ch aracteristics were typical of AML. Cytogenetic analysis revealed 46, X X, del(7) (q22; qter) karyotype as before. The bcr-abl fusion gene was not detected. Myeloid blasts were placed in a culture and maintained at 37 degrees C and 7.5% CO2 for two weeks. During this period, format ion of hemopoietic colonies was observed and subsequently analyzed usi ng histology and electron microscopy. This showed that the colonies co nsisted of differentiating erythroid, megakaryocytic and myeloid cells . Further, the chemosensitivity of leukemic cells was examined in both ''lymphoid'' and ''myeloid'' relapse instances. While the ''lymphoid' ' phenotype was characterized by good sensitivity to corticosteroids, a typical feature of the ''myeloid'' phenotype was a high resistance t o corticosteroids with marginally increased sensitivity to ARA-C.