Insights into the genomic landscape of MYD88 wild-type Waldenstrom macroglobulinemia

Activating MYD88 mutations are present in 95% of Waldenstrom macroglobulinemia (WM) patients, and trigger NF-kappa B through BTK and IRAK. The BTK inhibitor ibrutinib is active in MYD88-mutated (MYD88(MUT)) WM patients, but shows lower activity in MYD88 wild-type (MYD88(WT)) disease. MYD88(WT) patients also show shorter overall survival, and increased risk of disease transformation in some series. The genomic basis for these findings remains to be clarified. We performed whole exome and transcriptome sequencing of sorted tumor samples from 18 MYD88(WT) patients and compared findings with WM patients with MYD88(MUT) disease. We identified somatic mutations predicted to activate NF-kappa B (TBL1XR1, PTPN13, MALT1, BCL10, NFKB2, NFKBIB, NFKBIZ, and UDRL1F), impart epigenomic dysregulation (KMT2D, KMT2C, and KDM6A), or impair DNA damage repair (TP53, ATM, and TRRAP). Predicted NF-kB activating mutations were downstream of BTK and IRAK, and many overlapped with somatic mutations found in diffuse large B-cell lymphoma. A distinctive transcriptional profile in MYD88(WT) WM was identified, although most differentially expressed genes overlapped with MYD88(MUT) WM consistent with the many clinical and morphological characteristics that are shared by these WM subgroups. Overall survival was adversely affected by mutations in DNA damage response in MYD88(WT) WM patients. The findings depict genomic and transcriptional events associated with MYD88(WT) WM and provide mechanistic insights for disease transformation, decreased ibrutinib activity, and novel drug approaches for this population.