Abstract
Introduction
Waldenstrom’s macroglobulinemia (WΜ) is an incurable disorder characterized by bone marrow infiltration from neoplastic lymphoplasmacytic B-lymphocytes and monoclonal IgM production. Recent data suggest a possible causal relationship of MYD88-L265P mutation with the pathogenesis of the disease (Treon Sp et al. N Eng J Med 2012;367:826-33). Additional studies have conformed that MYD88-L265P is characteristic of WΜ, but it is also rarely present in other chronic lymphoproliferative disorders (LPDs) (Jiménez C et al. Leukemia 2013,doi: 10.1038/leu.2013.62; Varettoni M et al. Blood 2013;121:2522-8). The purpose of this study was to analyse the prevalence of the aforementioned mutation in patients with WM and other LPDs, using a fast and reliable polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) protocol.
Methods
Genomic DNA was extracted from the bone marrow of 11 patients with WΜ, 12 patients with B-cell chronic lymphocytic leukemia (CLL), 8 with splenic lymphoma with villous lymphocytes (SLVL). Furthermore, consecutive samples of peripheral blood and bone marrow isolated CD19+ cells, derived from a patient with monoclonal IgM gammopathy of undetermined significance (MGUS-IgM), were also retrospectively analysed for the presence of MYD88-L265P defect. The detection of the mutation was performed by PCR amplification of the MYD88 exon 5 region, followed by RFLP analysis, since the presence of the mutation results in the generation of BsiEI restriction enzyme site. PCR-RFLP results were also confirmed by direct sequencing of purified CD19+cells.
Results
The MYD88-L265P mutation was detected in 10 patients with WΜ (90.9%), in 1 patient with SLVL with markers of lymphoplasmatocytoid differentiation (12.5%) and was absent in all CLL patients. Interestingly, our PCR-RFLP protocol exhibited a greater sensitivity than direct sequencing, when applied to total bone marrow cells (12.5% vs 25%). Moreover, the patient with MGUS-IgM displayed the MYD88-L265P mutation in isolated CD19+cells of both bone marrow and peripheral blood in all consecutive samples and remains in a stable condition for the last 7 years.
Conclusion
PCR-RFLP is a rapid, sensitive and reliable technique for the detection of MYD88-L265P mutation in patients with WM and lymphomas with lymphoplasmatocytoid differentiation. Additionally, the presence of MYD88-L265P mutation in MGUS-IgM in the absence of disease progression for many years, suggests that this genetic defect alone is not sufficient to lead to overt neoplastic disease.
Disclosures:
No relevant conflicts of interest to declare.
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