Molecular analysis of interferon-induced suppression of Philadelphia chromosome in patients with chronic myeloid leukemia.

Treatment with recombinant human interferon alpha-A (Roferon-A) is associated with stable suppression of the population of cells that display the Philadelphia (Ph1) chromosome in some patients with chronic myelogenous leukemia (CML) as defined by cytogenetic analysis. Southern blot analyses employing a 3' breakpoint cluster region (bcr) probe (Pr-1) were performed to confirm a complete suppression of the Ph1+ chromosome-positive clone of cells at the DNA level. The complete disappearance of rearranged restriction fragments of the bcr gene, which were a characteristic of the disease prior to Roferon-A therapy, was accompanied by the restoration of normal bone marrow and achievement of durable ongoing complete remission for 9 and 6 months, respectively, in two patients with Philadelphia-positive (Ph1+) CML. Molecular analysis is a valuable probe for monitoring the clinical course of disease in patients with Ph1+ CML.