Single-cell profiles reveal tumor cell heterogeneity and immunosuppressive microenvironment in Waldenström macroglobulinemia

Abstract

Background Waldenström macroglobulinemia (WM) is a rare and incurable indolent B-cell malignancy. The molecular pathogenesis and the role of immunosuppressive microenvironment in WM development are still incompletely understood. Methods The multicellular ecosystem in bone marrow (BM) of WM were delineated by single-cell RNA-sequencing (scRNA-seq) and investigated the underlying molecular characteristics. Results Our data uncovered the heterogeneity of malignant cells in WM, and investigated the kinetic co-evolution of WM and immune cells, which played pivotal roles in disease development and progression. Two novel subpopulations of malignant cells, CD19+CD3+ and CD138+CD3+, co-expressing T-cell marker genes were identified at single-cell resolution. Pseudotime-ordered analysis elucidated that CD19+CD3+ malignant cells presented at an early stage of WM-B cell differentiation. Colony formation assay further identified that CD19+CD3+ malignant cells acted as potential WM precursors. Based on the findings of T cell marker aberrant expressed on WM tumor cells, we speculate the long-time activation of tumor antigen-induced immunosuppressive microenvironment that is involved in the pathogenesis of WM. Therefore, our study further investigated the possible molecular mechanism of immune cell dysfunction. A precursor exhausted CD8-T cells and functional deletion of NK cells were identified in WM, and CD47 would be a potential therapeutic target to reverse the dysfunction of immune cells. Conclusions Our study facilitates further understanding of the biological heterogeneity of tumor cells and immunosuppressive microenvironment in WM. These data may have implications for the development of novel immunotherapies, such as targeting pre-exhausted CD8-T cells in WM.

B-cell specific expression of the murineMyd88L252Pmutation correlates with the establishment of an immunosuppressive microenvironnement in Waldenström macroglobulinemia lymphoplasmacytic lymphoma

“…Moreover, similar to the observations made in WM patients, we demonstrated in our mouse model an increase in the population of Tregs in splenic tumours [25]. Tregs are immunosuppressive cells, and deregulation of their functions is known to be involved in many cancers.…”

“…In parallel, we also demonstrated the existence of a T-cell exhaustion with an overexpression of the four main immune checkpoint molecules PD-1, CTLA-4, TIM-3 and LAG-3, associated with an increase in TNFα and d’IL-10 secretion. In our mouse model, we confirmed what was suspected in WM patients: the presence of the constitutively active mutated MYD88 protein seems to induce the emergence of an immunosuppressive tumour phenotype responsible for T-cell exhaustion with age [25], [27]. Furthermore, it would be particularly interesting to determine exactly which antigens are recognized by the exhausted T cells in our model, as this would perhaps enable us to draw up a list of antigens favouring T-cell exhaustion and tumour escape.…”

“…In the first, Kaushal A. et al combined mass cytometry with the CITE-seq technique to demonstrate that a tumour clone-specific T immune response was established very early in the MGUS phase, and that throughout disease development T lymphocytes will progressively acquire an exhausted phenotype with loss of the naive T compartment and desensitization to IFNγ [24]. A little later, Sun H. et al performed a high-throughput study of the WM microenvironment by analysing bone marrow samples in single cell RNAseq, and demonstrated a loss of NK cell cytotoxic activity [25]. In addition, he observed the presence of depleted CD4 and CD8 expressing T cells with loss of the naive compartment and increase in Regulatory T cells (Tregs) [25].…”

“…A little later, Sun H. et al performed a high-throughput study of the WM microenvironment by analysing bone marrow samples in single cell RNAseq, and demonstrated a loss of NK cell cytotoxic activity [25]. In addition, he observed the presence of depleted CD4 and CD8 expressing T cells with loss of the naive compartment and increase in Regulatory T cells (Tregs) [25]. These recent studies demonstrate that immune escape seems to take place during the development of WM, leading to T-cell exhaustion and inactivity.…”

Single‐cell analysis of MYD88L265P and MYD88WT Waldenström macroglobulinemia patients

“…To the best of our knowledge, few studies have performed single-cell transcriptome analysis in WM patients; however, this is the first study to focus on the transcriptome of MYD88 WT and MYD88 MUT patients at the single-cell level. 36,37 Most importantly the characterization of MYD88 WT WM, an infrequent subtype of WM, is particularly interesting as it has been shown to be associated with increased risk for disease transformation and relative resistance to ibrutinib. Hence understanding the molecularly driven underlying mechanisms of these distinct genetic subtypes of WM patients is critical for developing informed criteria for patients who would benefit from alternative therapies and frequent monitoring.…”