The reciprocal chromosomal translocation t (9;22), which can be observed in mitotic cells as a typical cytogenetic abnormality - Philadelphia chromosome (Ph1) - has been found in about 90 percent of patients with chronic myelogenous leukemia (CML), 20 percent of adult acute lymphoblastic leukemia, and 2 percent of acute myelogenous leukemia. Ph1 positive CML is characterized by a consistent set of molecular perturbations: breaks within a bcr region on chromosome 22, transfer of the c-abl proto-oncogene from chromosome 9q34 to 22q11, and expression of a novel chimeric 210 kilodalton protein. Ph1 positive acute leukemia takes two molecular forms: molecular abnormalities identical to those found in CML are present in a half of the patients; they may represent the end stage of subclinical CML. In the other half of patients a unique aberrant protein p 190 is detected, corresponding to the different juxtaposition of bcr and c-abl genes.
Philadephia chromosome after 30 years
