Chronic myelogenous leukemia and genetic events at 9q34.

Assessment of cytogenetic patterns associated with chronic myelogenous leukemia (CML) suggests that genetic events at band q34 of chromosome nine are critical in the conversion of benign to malignant hematopoiesis. A break at this band is identified in almost all cases of Philadelphia chromosome (Ph1) positive CML, is also noted in some cases of Ph1 negative CML and cannot be excluded in the remaining cases. The human cellular homolog of the Abelson retrovirus oncogene (c-abl) is situated at band 9q34 and is translocated with the genetic sequences distal to the break point at this site in Ph1 positive disease. This oncogene has been shown experimentally to transform pre-B cells and it is expressed in primitive cells of the granulocytic series which are involved in CML. Although the break in CML chromosomes at 9q34 and the location of c-abl at 9q34 could be unrelated, it seems more likely that the two genetic events are associated with evolution of malignant hematopoiesis of man.