Single-cell sequencing reveals transcriptional and metabolic divergence of bone-involved multiple myeloma

Abstract Multiple myeloma (MM) presents with heterogeneous clinical symptoms, commonly categorized as CRAB features—hypercalcemia, renal failure, anemia, and bone injuries. Notably, myeloma bone disease (MBD) is observed in up to 80% of newly diagnosed MM (NDMM) patients, highlighting its significant clinical burden. This study aims to systematically dissect the transcriptional, immunological, and metabolic distinctions between MM patients with and without bone involvement. We collected bone marrow specimens, bone marrow aspirates, and peripheral blood mononuclear cells (PBMCs) from 14 MM patients. According to their presenting symptoms at diagnosis, patients were classified into four groups: G1 (n = 4) with anemia, G2 (n = 4) with bone injuries, G3 (n = 2) with renal failure, and G4 (n = 4) presenting with all four CRAB features. Cellular subtypes were identified through clustering, followed by BCR sequencing, pseudotime analysis, inferCNV, and metabolic profiling to assess clonal evolution, immune dynamics, and transcriptional/metabolic heterogeneity across CRAB groups. Distinct immune microenvironment alterations were observed across CRAB groups. Notably, bone disease groups (G2 and G4) displayed expanded monocyte populations, reduced T/NK cell proportions. B cell clonal diversity was markedly elevated in G2, with enriched unswitched memory B cells and disrupted differentiation trajectories. G4 showed enrichment of terminally differentiated subsets with upregulation of immunoglobulin-related genes, while G2 exhibited downregulation of bone remodeling pathways. Stage-specific expression of AHNAK, AREG, and BTG1 was observed along with cell differentiation. Plasma cells from G4 exhibited terminal differentiation and aggressive phenotypes, while those from G1 and G2 remained in earlier states. CNV analysis confirmed high genomic instability in malignant plasma cells, particularly in G3 and G4. Metabolically, each group demonstrated unique signatures: G2 showed glycation-related dysregulation linked to bone pathology, G3 featured enhanced TCA and BCAA metabolism. Our findings reveal symptom-specific transcriptional, immunological, and metabolic landscapes in MM. Bone injury groups are marked by immune suppression, clonal complexity, and metabolic reprogramming. Further research is needed to validate these findings.