Interleukin-7 enhances colony growth and induces CD20 antigen of a Ph+ acute lymphoblastic leukemia cell line, OM9;22

A newly established human leukemia cell line, OM9;22, is reported, with B-precursor immunophenotype (CD10+ CD19+ CD22+ HLA- DR+ C mu-) and CD13 antigen, originated from a 19-year-old female patient with Philadelphia (Ph) chromosome-positive acute lymphoblastic leukemia (ALL). The OM9;22 cells carry a Philadelphia (Ph) translocation and hybrid message detected by a minor-breakpoint cluster region (BCR) exon 1/ABL exon 2 junctional probe using reverse transcriptase polymerase chain reaction. The genetic alterations are consistent with those observed in the donor's leukemia cells, allowing us to conclude that this cell line is a minor-BCR rearranged Ph-positive ALL (Ph+ ALL). Colony formation of the OM9;22 cells in methylcellulose culture is enhanced by the addition of human interleukin 7 (IL-7). In liquid culture, more than 80% of IL-7-treated OM9;22 cells express CD20 antigen but fail to express surface immunoglobulins or cytoplasmic mu-chain, indicating that the cells have a potential of limited maturation by IL-7. By contrast, IL-4 suppresses the colony formation of the OM9;22 cells. These findings suggest that this cell line might be a model of B-precursor human leukemia with proliferative capability by IL-7.