engleski

Detection of BCR/ABL1 translocation in CML using FISH

Chronic myelogenous leukemia is characterized by translocation BCR/ABL1 resulting in production of BCR/ABL1 fusion protein – aberrant tyrosine kinase. This specificity allowed development of targeted therapy. In 1990s imatinib mesylate, specific tyrosine kinase inhibitor was produced and till today it is the first line of treatment for majority of patients with confirmed translocation. BCR/ABL1 is most commonly detected by standard karyotyping, while additional methods for its detection are PCR and FISH. Q-PCR is usually used for monitoring differences in amount of BCR/ABL1 transcript during the therapy and defining molecular response to treatment. In period between January 2007 and Jun 2010, nine patients with suspected CML were admitted to our hospital. All had histopatological diagnosis of MPD/CML. Karyotype and PCR were done in order to detect BCR/ABL1 translocation. When this data were taken together with clinical performance, six of them were finally diagnosed as CML positive for BCR/ABL1 and received imatinib mesylate. All six patients responded well to therapy. Those patients were included in subsequent studies where FISH for detection of BCR/ABL1 had to be performed on their FFPE bone marrow trephine samples. Two different probes were used: break-apart probe for BCR gene and fusion probe for BCR/ABL1 translocation. After double blind reading, with 100% concordance, results showed translocation of BCR gene in 3 of 6 cases (50%) and BCR/ABL1 translocation in 6 of 6 cases (100%). This data suggest that, although considered to be supplementary FISH probes for detection of BCR translocation, differently designed probes can not be used exclusively. We recommend usage of fusion probe for screening process in patients with suspected CML and careful evaluation of samples with at least two independent observers.

FISH; karyotype; PCR; BCR/ABL1

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