PDGFRA FISH, FIP1L1-PDGFRA FISH
This test would be arranged by a patient’s doctor before making decisions about the best choice of therapy.
This is a test for an abnormal gene which can occur in some forms of blood cancers i.e. leukaemia or lymphoma, most commonly chronic eosinophilic leukaemia. The gene is formed by the fusion of fragments of two other genes called PDGFRA and FIP1L1. This fusion gene then produces a fusion protein which is made up of parts of both the PDGFRA and FIP1L1 proteins.
The PDGFRA gene normally codes for a cell membrane receptor protein. To be turned on the PDGFRA receptor normally needs to bind to another protein called a ligand. However the PDGFRA-FIP1L1 fusion protein receptor no longer responds to ligand binding, it is permanently turned on. This results in continuous signalling to the cell nucleus and unregulated stimulation of cell proliferation, particularly of eosinophils, a type of white blood cell.
A cancer specialist will use many different tests to identify the treatment most likely to help a patient with a cancer of blood cells. This is just one of the tests that would be used.
Sometimes people develop resistance to imatinib even though the tyrosine kinase inhibitor is usually very effective for treating people with the PDGFRA-FIP1L1 fusion gene at low doses. For the rare individuals whose HE is resistant to imatinib, stem cell transplants have reversed the organ dysfunction caused by hypereosinophilia. However, health practitioners have limited experience with this treatment, so it is not used routinely. Chemotherapy has also been used with some success for people with the fusion gene who don't respond to treatment with imatinib. Some individuals with the fusion gene are also treated with corticosteroids to lower their eosinophil count and help control organ damage.
People with PDGFRA-FIP1L1- may also manifest as acute myeloid or lymphoblastic leukemia, though that is rare. PDGRA-FIP1L1 has also been found infrequently in other leukemias and successfully treated with imatinib.
Unlike some other genetic abnormalities, PDGFRA-FIP1L1 related change is very subtle and thus cannot be detected with routine karyotyping, which involves looking at chromosomes under a microscope.
Last Review Date: August 1, 2018