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ONCOLOGY REQUISITION
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Synonyms: C-KIT exons 8 and 17
The human proto-oncogen C-KIT is located on chromosome 4q12. KIT is minimally expressed in normal peripheral blood cells except for mast cells, but it is commonly expressed in acute myeloid leukemias (AML), in which a spectrum of gain of function mutations has been identified, especially in the core binding factor variants characterized by t(8;21) or inv16(p13q22). Insertions/deletions affecting residue Tyr418 and/or Asp419 in exon 8 disrupt the inhibitory effect exerted by the juxtamembrane region on the kinase domain, leading to hyperactivation of KIT. Asp816Val/Tyr are point mutations affecting exon 17 in the second kinase domain, destabilizing the inactive conformation and hence promoting ligand-independent activation. These two sets of mutations in CBF-AML increase the relapse rate and might confer a poor prognosis.
C-KIT is expressed in 70%-90% of AML patients, thus the mRNA transcript is a suitable template. The methodology employs the following steps. After isolating RNA from the patient sample, reverse-transcription converts the sample RNA to cDNA. Two sets of primers then amplify exon 8 and exon 17, which is followed by sequence analysis.
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