ACTIVATION OF P65 NF-KAPPA-B PROTEIN BY P210(BCR-ABL) IN MYELOID CELL-LINE (P210(BCR-ABL) ACTIVATES P65 NF-KAPPA-B)

The chimeric tyrosine kinase p210(BCR-ABL) is involved in the pathogen esis of chronic myelogenous leukemia. It transforms immature hematopoi etic cells in vitro and abrogates IL-3-dependent growth. The mechanism s by which p210(BCR-ABL) mediates its oncogenicity are not well elucid ated. Identifying transcription factors targeted by the chimeric prote in may help to clarify these mechanisms. We have analysed the effect o f p210(BCR-ABL) expression on NF-kappa B activity in DA1 cells (an IL- 3-dependent murine myeloid progenitor cell line). A specific stimulati on of NF-kappa B activity by kinase-active wild-type p210(BCR-ABL) has been evidenced by transcriptional activation assays. Electrophoretic mobility supershift assays revealed the presence of p65 protein (RelA) DNA binding activity in p210(BCR-ABL) transformed DA1 cells but not i n parental DA1 cells. Activation of RelA in transformed DA1 cells may occur by protein stabilization. Experiments using oligonucleotides ant isense to RelA showed that p210(BCR-ABL) transfected cells failed to s urvive after IL-3 removal. Moreover, inhibition of cellular growth was shown following treatment of p210(BCR-ABL) transformed DA1 cells by p 65 antisense oligonucleotides. This study suggests that p65 NF-kappa B may be an effector for p210(BCR-ABL) and probably contributes to its induced transformation process.