Analysis of Breakpoints of bcr-abl Fusion Gene Using RT-PCR / 대한임상병리학회지

ABSTRACT

BACKGROUND: Three types of chimeric mRNA can be expressed as a result of fusion of abl gene on chromosome 9 and bcr gene on chromosome 22. These are b3a2, b2a2, and e1a2. Rearranged mRNA of bcr-abl fusion gene is found in majority of chronic myelogenous leukemia (CML) and in 20% of acute lymphoblastic leukemia (ALL) and in other hematologic malignancies. METHODS: We have examined the chimeric mRNA by reverse transcriptase-polymerase chain reaction (RT-PCR) since 1994. Positive results for the chimeric mRNA were 167 (118 patients) out of 714 examined cases. 94 patients with CML irrespective of the disease course, 49 with ALL, 120 with acute myelogenous leukemia, 11 with acute mixed leukemia, and 7 with myelodysplastic syndrome were included. RESULTS: 97.9% (92/94) of patients with CML, 40% (20/49) of ALL, 45% (5/11) of acute mixed leukemia, and 14% (1/7) of myelodysplastic syndrome were positive for bcr-abl rearrangement. In CML, positive cases were with b3a2 (64%), b2a2 (32.6%), and b3a2/b2a2 (2.2%). One patient with CML-like feature expressed e1a2 type mRNA. In adult ALL, 62.5% (10/16) expressed minor-bcr (e1a2). CONCLUSIONS: The bcr-abl fusion gene was positive in various hematologic diseases as well as CML and that fact indicates the dysfunction of primitive pleuripotent stem cells. Various expressions and changes of mRNA types in bcr-abl fusion gene might be due to alternative splicing mechanism and detection sensitivity of RT-PCR when two types were intermingled. We should be aware of these facts when interpretating the results.