Establishment of a novel acute monoblastic leukemia cell line (YK-M2) having a near-triploid karyotype

The YK-M2 cell line was established from the peripheral blood of a patient with acute monoblastic leukemia in whom an anterior mediastinal tumor preceded the peripheral blood manifestation. The established cells grew in a single cell suspension with a doubling time of 60 h and consisted of primitive monoblastic cells. The cells were 52% positive for peroxidase staining and manifested strongly positive activity of alpha-naphthyl acetate esterase, which was completely inhibited by sodium fluoride. The cells showed strong expression of Fc gamma receptors and phagocytosed sensitized ox erythrocytes. When the cells were incubated with 1 alpha,25-dihydroxy-vitamin D3, they were induced to differentiate into mature monocyte-macrophage-like cells, which reduced the nitroblue tetrazolium dye and released a small amount of the superoxide anion. Cytogenetic studies revealed that the cells had a near-triploid karyotype with a modal chromosome number of 68, and the short arm of one No. 17 chromosome was deleted [del(17)(p11)]. The YK-M2 cell line is particularly unique in that the cells retained the polyploid karyotype that may be an initial cytogenetic change in the malignant transformation of the parent leukemia cells.