Single-cell RNA sequencing defines distinct disease subtypes and reveals hypo-responsiveness to interferon in asymptomatic Waldenstrom’s Macroglobulinemia

Waldenstrom’s Macroglobulinemia (WM) is an IgM-secreting bone marrow (BM) lymphoma that is preceded by an asymptomatic state (AWM). To dissect tumor-intrinsic and immune mechanisms of progression, we perform single-cell RNA-sequencing on 294,206 BM tumor and immune cells from 30 patients with AWM/WM, 26 patients with Smoldering Myeloma, and 23 healthy donors. Despite their early stage, patients with AWM present extensive immune dysregulation, including in normal B cells, with disease-specific immune hallmarks. Patient T and NK cells show systemic hypo-responsiveness to interferon, which improves with interferon administration and may represent a therapeutic vulnerability. MYD88-mutant tumors show transcriptional heterogeneity, which can be distilled in a molecular classification, including a DUSP22/CD9-positive subtype, and progression signatures which differentiate IgM MGUS from overt WM and can help advance WM research and clinical practice. The impact of tumor intrinsic and immune alterations on disease progression in patients with Waldenstrom’s Macroglobulinemia (WM) remains to be characterized. Here, the authors perform single-cell RNA-sequencing and identify distinct tumor subtypes, tumour microenvironment features and potential therapeutic vulnerabilities in patients with WM.