Contribution of MLPA to routine testing to detect the prognostic chromosomal abnormalities in chronic lymphocytic leukemia

Abstract

Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease and chromosomal abnormalities with prognostic impact are frequently detected in CLL patients. There are a variety of characterized chromosomal abnormalities detected by conventional cytogenetics in CLL. These abnormalities are valuable prognostic indicators and important key strategies for making treatment decisions. Deletions of 13q14, 11q22, and 17p13, and trisomy 12 are the most frequent chromosomal abnormalities in CLL. In this study, multiplex ligation probe amplification (MLPA) results using SALSA® MLPA kit P037-A2/P038-A2 were compared with results from conventional cytogenetics and fluorescence in-situ hybridization (FISH) and we assessed the suitability of MLPA technology as a method for detecting a variety of known chromosomal abnormalities in 41 CLL patients. DSP30+IL-2 combination was used as the mitotic stimulating agents because of the low mitotic index of CLL cells in conventional cytogenetics. Locus-specific probes for 11q22.3 (ATM), 13q14.3, and 17p13 (p53), and centromeric probe for chromosome 12 were used for FISH analysis.Informative results were obtained from 80.04% of peripheral blood and bone marrow cultures. Among the 13 positive patients for trisomy 12 by conventional cytogenetics and FISH, 5 patients were normal by MLPA. The 13q14 deletions were detected in 20 patients by FISH, however, of these, 6 patients were normal by MLPA. In contrast, the 17p13 and 13q14 deletions were detected by MLPA but not by conventional cytogenetics and FISH. In this study, we found that MLPA was not as sensitive as conventional cytogenetics and FISH at detecting mosaicisms below 25-30%. Although MLPA is a simple and cost-effective technique, it may give false negative results in patients with low level mosaicism for any abnormalities. We suggest that MLPA should be used with conventional cytogenetics and FISH in detection of chromosomal abnormalities with potential clinical significance in CLL.