Characteristics of Waldenström Macroglobulinemia in Koreans According to Mutational Status of MYD88 and CXCR4: Analysis by Ultra-Deep Sequencing

Abstract Background Little is known about the mutational frequency of MYD88 and CXCR4 and the corresponding characteristics in Asians afflicted with Waldenstrom Macroglobulinemia (WM). We investigated the characteristics of WM according to mutational status of MYD88 / CXCR4 , and attempted to determine the lineage commitment among hematopoietic cells by MYD88 L265P single cell sequencing on bone marrow (BM) smear slides. Materials and methods CXCR4 mutations were detected using ultra-deep sequencing by target capture. Mutational burden of MYD88 was assessed by real-time polymerase chain reaction. Single cell sequencing for MYD88 was performed on lymphocytes, plasmacytoid lymphocytes, plasma cells, and neutrophils by laser microdissection. Results Among 31 patients, the frequencies of MYD88 / CXCR4 mutations were as follows: MYD88 WT CXCR4 WT (19.4%), MYD88 L265P CXCR4 WT (61.4%), MYD88 L265P CXCR4 mut (19.4%; 1 frameshift and 5 nonsense mutations). IgM levels of MYD88 L265 CXCR4 WT patients were significantly higher than those of MYD88 WT CXCR4 WT patients ( P =0.024). Tumor burden in BM was highest in those patients with MYD88 L265P CXCR4 mut (82.0%), followed by MYD88 L265P CXCR4 WT (52.8%) and MYD88 WT CXCR4 WT (14.2%) ( P MYD88 -mutated DNA tended to correlate with tumor burden in BM (correlation coefficient 0.647, P =0.009). MYD88 L265P was detected in plasma cells, plasmacytoid lymphocytes, and lymphocytes but not neutrophils. Conclusions The frequency of MYD88 / CXCR4 mutations in Korean and Caucasian patients with WM was similar, however 5 out of the 6 CXCR4 mutations were nonsense—a proportion higher than reported frequencies in Caucasians. Ultra-deep sequencing was capable of detecting CXCR4 mutations not detectable by Sanger sequencing, suggesting a possible replacement of the B-cell sorting.