Characteristics of Waldenstrom Macroglobulinemia in Korean Patients According to Mutational Status of MYD88 and CXCR4: Analysis Using Ultra-Deep Sequencing

The frequencies of myeloid differentiation factor 88 (MYD88)/C-X-C chemokine receptor type 4 (CXCR4) mutations and the corresponding clinical characteristics in 31 Korean patients with Waldenstrom macroglobulinemia were assessed. Ultra-deep sequencing (for CXCR4) and several polymerase chain reaction-based methods (for MYD88) revealed that the frequencies of MYD88/CXCR4 mutations in these Korean patients were similar to reported frequencies for Caucasian individuals. Immunoglobulin M levels and tumor burden were highest in MYD88(L265P)CXCR4-mutation patients. Background: Little is known about the mutational frequency of myeloid differentiation factor 88 (MYD88) and C-X-C chemokine receptor type 4 (CXCR4) and the corresponding characteristics in Asian individuals 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 (muts) were detected using ultra-deep sequencing using target capture. Mutational burden of MYD88 was assessed using realtime polymerase chain reaction. Single-cell sequencing for MYD88 was performed on lymphocytes, plasmacytoid lymphocytes, plasma cells, and neutrophils using laser microdissection. Results: Among 31 patients, the frequencies of MYD88/CXCR4 muts were as follows: MYD88 wild type (WT) CXCR4(WT) (6 patients, 19.4%), MYD88(L265P)CXCR4(WT) (19 patients, 61.4%), MYD88(L265P)CXCR4(mut) (6 patients, 19.4%; 1 frameshift and 5 nonsense muts). Immunoglobulin M levels of MYD88(L265)CXCR4(WT) patients were significantly higher than those of MYD88(WT)CXCR4(WT) patients (P = .024). Tumor burden in BM was highest in patients with MYD88(L265)PCXCR4(mut) (82.0%), followed by MYD88(L265P)CXCR4(WT) (52.8%) and MYD88(WT)CXCR4(WT) (14.2%) (P <.001). The quantity of MYD88-mutated DNA tended to correlate with tumor burden in BM (correlation coefficient 0.647; P = .009). MYD88(L265P) was detected in plasma cells, plasmacytoid lymphocytes, and lymphocytes but not neutrophils. Conclusion: The frequency of MYD88/CXCR4 muts in Korean and Caucasian patients with WM was similar, however 5 of the 6 CXCR4 muts were nonsense-a proportion higher than reported frequencies in Caucasian individuals. Ultra-deep sequencing was capable of detecting CXCR4 muts not detectable using Sanger sequencing, suggesting a possible replacement of the B-cell sorting. (C) 2019 The Authors. Published by Elsevier Inc.