The Dreaded Philadelphia Chromosome

Until recently I had never heard the term “Philadelphia chromosome.” It wasn't until I was diagnosed with chronic myelogenous leukemia, earlier this year, that it became a part of my vocabulary; it has now taken temporary control of my life. This condition is not something that I was born with or something that I can, or will pass down to my children. It is not contagious; so you needn't run when you see me coming or wear garlic around your neck. It is my understanding that CML is just kind of a fluke. Lucky me!

There is some evidence that people treated with a high dose of radiation may have a small increase in risk, but most people treated with radiation do not develop CML and most people with CML were not exposed to high-dose radiation. So, go figure; sounds like they really just don’t know the cause.

Normal cells have pairs of chromosomes that are numbered 1 to 22, and a pair of sex chromosomes; XX for females and XY for males. Chromosomes are structures in the cells that contain genes. The genes give instruction to the cells.  This is “my” understanding of what the “Philadelphia chromosome” is; for some reason unbeknownst to all, a small piece of chromosome 22 breaks off and saunters its’ way over to chromosome 9. It then decides that it would like to stay there and hang out with chromosome 9. So it attaches itself there and sends a piece of chromosome 9 on over to keep chromosome 22 company.  

When Joe and I are teaching dance classes he is constantly saying “rotate” to the students. I told him that it must be his fault that I now have leukemia, because he said rotate just one too many times. I think that my chromosomes must have heard him and just decided to rotate!

  

The break on chromosome 9 involves a gene called Abl and the break on chromosome 22 involves a gene called Bcr. The Bcr and Abl genes combine to make the CML causing gene called the Bcr-Abl gene. There doesn’t seem to be any rhyme or reason as to why this occurs; it just does. This Bcr-Abl gene produces a dysfunctional protein called “BCR-ABL tyrosine kinase”; this leads to the abnormal regulation of cell growth and survival and is responsible for CML. Think of it as a faucet that is constantly in the on position. It is on and making immature white cells that are crowding out the good white cells as well as the red cells and platelets.