ESTABLISHMENT AND CHARACTERIZATION OF A MEGAKARYOBLAST CELL-LINE WITHAMPLIFICATION OF MLL

A new cell line with megakaryoblastic features, designated UoC-M1, was established from the malignant cells of a 68-year-old patient with ac ute myeloid leukemia. The patient's leukemic cells reacted with cu-nap hthyl acetate esterase and acid phosphatase and expressed CD7, CD24, C D34, CD38, CD45, HLA-DR and CD61. Cytogenetic analysis of the patient' s malignant cells (and of the UoC-M1 cells) showed a human, male hypod iploid karyotype with many chromosome rearrangements and marker chromo somes. Spectral karyotyping (SKY) analysis complemented the G-banded k aryotyping and clarified several chromosomal translocations and identi fied the marker chromosomes. Fluorescence in site hybridization (FISH) and SKY analysis demonstrated that one marker chromosome contained th ree segments of chromosome 9 interspersed with three segments of chrom osome 11, as well as a portion of chromosome 19. FISH analysis with a probe for MLL revealed that the UoC-M1 cells contained four copies of the MLL gene. Southern blot analysis determined that the MLL gene had a germline profile while Northern and Western analyses showed that the MLL mRNAs and protein were of the appropriate sizes. This is the firs t report of amplification of the MLL gene which may be an additional m echanism of leukemogenesis or disease progression.