However, loss of ABL-BCR expression also occurred without an overt deletion, suggesting the existence of other mechanisms by which ABL-BCR transcription can be abolished.     ///    "First, we demonstrate that all derivative chromosome 9 deletions detected by fluorescence in situ hybridization were associated with an absence of ABL-BCR expression. "    ///    "Derivative chromosome 9 deletions in chronic myeloid leukemia: poor prognosis is not associated with loss of ABL-BCR expression, elevated BCR-ABL levels, or karyotypic instability.. "    ///    "Furthermore, analysis of survival in 160 patients demonstrated that loss of ABL-BCR expression, in contrast to deletion status, was not an indicator of poor prognosis. "