WHAT IS THE PHILADELPHIA CHROMOSOME, BCR-ABL?
BCR-ABL stands for the name given to an abnormal gene that is the result of a fusion of material from 2 chromosomes (22 and 9). In fact, this has everything to do with CML and the Philadelphia chromosome. This Philadelphia (PH) chromosome is an abnormal chromosome that results from an exchange of material (DNA) between the normal chromosomes 22 and 9. It is present in over 90% of CML cases. In chromosome 9, there is a gene called c-abl (from “Abelson”). A break occurs beside this gene, and it is translocated to a place in chromosome 22, called bcr (breakpoint cluster region). What happens then is the fusion of these two pieces of DNA, that gives rise to a fusion gene (bcr-abl). This fusion gene is involved in the pathogenesis of CML and possibly other leukemias (e.g. ALL). Also, it serves as a molecular marker of PH-positive cells, and is currently screened by PCR in the post-BMT period. Very interestingly, bcr-abl might prove useful as a target for specific treatment with antibodies d
