Suppression of cell proliferation and the expression of a bcr-abl fusion gene and apoptotic cell death in a new human chronic myelogenous leukemia cell line, KT-1, by interferon-alpha.

A new human leukemia cell line, KT-1, was established from a patient in the blastic crisis phase of chronic myelogenous leukemia (CML). This cell line had a positive reaction for intracytoplasmic myeloperoxidase and two Philadelphia chromosomes (Ph1) [t(9;22)(q34;q11)] and lacked normal copies of chromosomes 9 and 22. Molecular characterization of the breakpoint in the t(9;22)(q34;q11) showed that KT-1 had a bcr-2/abl-2 splice junction. When the KT-1 cells were cultured with interferon (IFN)-alpha or IFN-gamma, the growth of the cells were dose-dependently suppressed. IFN-alpha and IFN-gamma exerted synergistic suppressive effects on the growth of KT-1 cells. Furthermore, IFN-alpha suppressed the expression of the bcr-abl fusion gene in KT-1 cells, and induced G1 cell-cycle arrest and apoptotic cell death. The KT-1 cell line should be a valuable tool for studying the molecular mechanism of the suppression of Ph1 clone cells from CML by IFN.