The Philadelphia chromosome is a specific finding in the genes of a person’s white blood cells—a finding that has implications for leukemia. It most commonly comes up in reference to “Philadelphia chromosome-positive leukemia.”
More specifically, a leukemia might be called “Philadelphia-chromosome-positive (Ph+)chronic myeloid leukemia” (CML) or “Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia” (ALL).
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Chromosome Refresher
Each chromosome has its own characteristic shape, and the location of specific genes can be found in relation to the shape of a chromosome. When all the genetic material in the cell of a human being gets packaged up, there are 23 pairs of chromosomes, for a total of 46 chromosomes in each cell. In fact, different species of plants and animals have differing set numbers of chromosomes. A fruit fly, for example, has four pairs of chromosomes, while a rice plant has 12 and a dog, 39.
Overview
The Philadelphia chromosome has a story and a setting, but for practical purposes, it can be defined as an abnormality of chromosome 22 in which part of chromosome 9 is transferred to it. In other words, a piece of chromosome 9 and a piece of chromosome 22 break off and trade places. When this trade takes place, it causes trouble in the genes—a gene called “BCR-abl” is formed on chromosome 22 where the piece of chromosome 9 attaches.The changed chromosome 22 is called the Philadelphia chromosome.
Bone marrow cells that contain the Philadelphia chromosome are often found in chronic myelogenousleukemiaand sometimes found inacute lymphocytic leukemia. Though the Philadelphia chromosome is often thought of in connection with CML and ALL, it can also come up in other contexts, such as “variant Philadelphia translocations,” and “Philadelphia chromosome-negative chronic myeloproliferative disease.”
How the Philadelphia Chromosome Identifies Cancer
The Philadelphia chromosome is only found in the affected blood cells. Because of the damage to the DNA, the Philadelphia chromosome results in the production of an abnormal enzyme called a tyrosine kinase. Along with other abnormalities, this enzyme causes the cancer cell to grow uncontrollably.
Doctors will look for the presence of this abnormality when they are examining samples from yourbone marrow aspiration and biopsyto help make a proper diagnosis.
The identification of the Philadelphia chromosome in the 1960s led to major advancements in the treatment of CML. This laid the foundation for a new era of CML therapy called “tyrosine kinase inhibitors,” such as Gleevac (imatinib mesylate), Sprycel (dasatinib) and Tasigna (nilotinib).
More recently, two other tyrosine kinase inhibitors, Iclusig (Ponatinib) and Bosulif (Bosutinib) were also approved to treat adults who have newly diagnosed Philadelphia chromosome–positive (Ph+) CML in chronic phase. A third drug Synribo (Omacetaxine mepesuccinate) is another non tyrosine kinase inhibitor agent that has demonstrated activity in patients with CML and is an approved for the treatment of chronic phase CML in adults with resistance or intolerance to two or more tyrosine kinase inhibitors.
1 SourceVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kang ZJ, Liu YF, Xu LZ, et al.The Philadelphia chromosome in leukemogenesis.Chin J Cancer. 2016;35:48. doi:10.1186/s40880-016-0108-0Additional ReadingAdamson PC.Improving the outcome for children with cancer: development of targeted new agents.CA Cancer J Clin. 2015;65(3):212-220.Goldman, J. and Daley, G. (2007). Chronic Myeloid Leukemia. In Melo, J., and Goldman, J. (Eds.)Myeloproliferative Disorders(pp.1-13). New York. Springer.
1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Kang ZJ, Liu YF, Xu LZ, et al.The Philadelphia chromosome in leukemogenesis.Chin J Cancer. 2016;35:48. doi:10.1186/s40880-016-0108-0Additional ReadingAdamson PC.Improving the outcome for children with cancer: development of targeted new agents.CA Cancer J Clin. 2015;65(3):212-220.Goldman, J. and Daley, G. (2007). Chronic Myeloid Leukemia. In Melo, J., and Goldman, J. (Eds.)Myeloproliferative Disorders(pp.1-13). New York. Springer.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Kang ZJ, Liu YF, Xu LZ, et al.The Philadelphia chromosome in leukemogenesis.Chin J Cancer. 2016;35:48. doi:10.1186/s40880-016-0108-0
Adamson PC.Improving the outcome for children with cancer: development of targeted new agents.CA Cancer J Clin. 2015;65(3):212-220.Goldman, J. and Daley, G. (2007). Chronic Myeloid Leukemia. In Melo, J., and Goldman, J. (Eds.)Myeloproliferative Disorders(pp.1-13). New York. Springer.
Adamson PC.Improving the outcome for children with cancer: development of targeted new agents.CA Cancer J Clin. 2015;65(3):212-220.
Goldman, J. and Daley, G. (2007). Chronic Myeloid Leukemia. In Melo, J., and Goldman, J. (Eds.)Myeloproliferative Disorders(pp.1-13). New York. Springer.
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