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.