Technical Notes
BCR/ABL translocation t (9; 22) for Minimal Residual Disease (MRD)
Clinical Significance:
A majority (90%) of patients with CML have a characteristic reciprocal translocation of DNA between chromosomes 9 and 22, termed the Philadelphia chromosome (Ph'), which can be reliably identified using molecular techniques. As the presence of BCR/ABL transcript correlates with the proliferative activity of the malignant clone, quantitation of the transcript can be utilized to predict relapse and MRD (1). The Real Time RT-PCR based assay provides quantitative data over a wide dynamic detection range of over five orders of magnitude and has a sensitivity of detecting 1 leukemic cell with translocation in 105 to 106 normal cells (2,3).The BCR/ABL gene is not exclusive to CML and is also present in a minority of some other oncohematological diseases, e.g. in about 25% of adult and 5% of children acute lymphoid leukemia (ALL), 1% acute myeloid leukemia (AML) and very rarely in lymphoma, myeloma or myelodysplastic syndromes. The presence of the BCR/ABL gene is a negative prognostic factor in these malignancies and the test can be used to identify patients that would benefit from allogenic BMT (4) or Gleevac (5, 6).
Methodology:
Minor groove binder (MGB) with Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) (2) has been utilized to develop a quantitative, Real Time RT-PCR based assay for the ultrasensitive detection and quantitation of BCR/ABL mRNA.References:
1) Hochhaus A., Lin F., Reiter A. et al (1996) 87, 1549.2) Kutyavin I.V., Afonina I.A., Mills A. et al (2000) Nuc. Acid Res. 28, 655.
3) Mensink E., van de Locht A., Schattenberg A et al (1998) Br. J. Haematol. 102, 768.
4) Battmer E.M., Kafert S., Stucki A. et al (1999) Leukemia 13 (9), 1383.
5) Paschka P., Schoch C., Lahaye T et al (2000) Blood 96, 734a.
6) Scheuring U.J., wassman H., Pfeiffer R et al (2000) ASH Conference, Dec 4, San Francisco.