Project description:Light chain amyloidosis (AL) is a life-threatening plasma cell dyscrasia manifested by irreversible damage of multiple organs caused by monoclonal immunoglobulin light chain, production of pathogenic bone marrow plasma cells (BMPCs). Although AL is featured by both misfolding of monoclonal protein and plasma cell proliferation, the functional subclones and molecular mechanism of BMPCs in AL remain elusive. Also, inter-individual heterogeneities of AL determine the chemotherapy response and organ tropism of light chains, which require well-defined molecular subtypes. To address these, we conducted single-cell RNA sequencing (scRNA-seq) of BMPCs donated by patients with AL, patients with monoclonal gammopathy of undetermined significance (MGUS), and healthy controls. Single-cell transcriptome revealed a continuity of bone marrow plasma cell (BMPC) functional subclones, delineating DNA repair, cell proliferation, immunoglobulin production, etc., with the gradient of signaling entropy and immunoglobulin production. The amyloidosis-associated genes, such as the amyloid-beta binding Apolipoprotein E (APOE), Cystatin 3 (CST3), and Complement C1q A Chain (C1QA), were up-regulated in a subclone enriched in AL. The speculated light chain-producing subclones in AL up-regulated neutrophil degranulation pathways, transport to and modifications in Golgi apparatus, and asparagine N-linked protein glycosylation. Cyclin D1 (CCND1)hi AL, consisted of larger main subclones which highly expressed Bcl-2 complex and B-cell differentiation genes, was sensitive to venetoclax that targets Bcl-2. A major subset of CCND1low AL harbored larger carbohydrate-synthesizing subclone and up-regulated CCND2 and the amyloidosis-associated genes. Collectively, our results provided frontier insights into the functional subclones and molecular mechanism of BMPCs in AL, associated with amyloidosis, light chain production and venetoclax sensitivity, as knowledge for the future research on AL pathogenesis, AL subtypes and AL-specific therapies.

Project description:Amyloid light chain amyloidosis (AL) is an incurable protein misfolding disorder characterized by the production of amyloidogenic immunoglobulin light chains by clonal populations of plasma cells. These abnormal light chains accumulate as amyloid fibrils in vital organs and cause multi-organ dysfunction that can be rapidly fatal. Current treatment regimens, which include proteasome inhibitors, were developed for the treatment of the more common plasma cell disease multiple myeloma and have demonstrated efficacy in AL amyloidosis. However, use of these agents is frequently limited due to multi-organ dysfunction at presentation, resulting in a median survival of 2-3 years and underscoring the need for novel therapies. By analyzing bone marrow-derived plasma cells from 44 patients with AL amyloidosis, we find that clonal plasma cells are highly primed to undergo apoptosis and exhibit strong dependencies on pro-survival BCL-2 family proteins that can potentially be targeted by recently-developed BH3 mimetics. In particular, we find that clonal plasma cells are highly dependent on the pro-survival MCL-1 and undergo apoptosis in response to single-agent treatment with an MCL-1 inhibitor. Notably, this MCL-1 dependency is indirectly targeted by the proteasome inhibitor bortezomib, which is currently the standard of care for this disease, via the stabilization of Noxa and its direct inhibitory binding to MCL-1. BCL-2 inhibition with the FDA-approved inhibitor venetoclax (ABT-199) sensitizes plasma cells to bortezomib treatment and other front-line therapies, which can be observed in vitro and in vivo. Mass spectrometry-based proteomic analysis reveals changes in signaling pathways regulating apoptosis, proliferation and mitochondrial metabolism between isogenic AL amyloidosis and multiple myeloma cells that divergently alter their sensitivity to therapy. Overall, our results indicate that BH3 mimetics may be highly effective therapies for AL amyloidosis that exploit inherent and induced dependencies on pro-survival proteins.

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Homo sapiens

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