Purpose: In multiple myeloma (MM), therapy-induced clonal evolution is associated with treatment resistance and is one of the most important hindrances toward a cure for MM. To further understand the molecular mechanisms controlling the clonal evolution of MM, we applied single-cell RNA-sequencing (scRNA-seq) to paired diagnostic and post-treatment bone marrow (BM) samples. Experimental Design: scRNA-seq was performed on 38 BM samples from patients with monoclonal gammopathy of undetermined significance (MGUS) (n = 1), MM patients at diagnosis (n = 19), MM post-treatment (n = 17), and one healthy donor. The single-cell transcriptome data of malignant plasma cells and the surrounding immune microenvironment were analyzed. Results: Profiling by scRNA-seq data revealed three primary trajectories of transcriptional evolution after treatment: clonal elimination in patients with undetectable minimal residual disease (MRD-), as well as clonal stabilization and clonal selection in detectable MRD (MRD+) patients. We noted a metabolic shift towards fatty acid oxidation in cycling-resistant plasma cells (PCs), while selective PCs favored the NF-κB pathway. Intriguingly, when comparing the genetic and transcriptional dynamics, we found a significant correlation between genetic and non-genetic factors in driving the clonal evolution. Furthermore, we identified variations in cellular interactions between malignant plasma cells and the tumor microenvironment (TME). Selective PCs showed the most robust cellular interactions with the TME. Conclusions: These data suggest that MM cells could rapidly adapt to induction treatment through transcriptional adaptation, metabolic adaptation, and specialized immune evasion. Targeting therapy-induced resistance mechanisms may help to avert refractory disease in multiple myeloma.

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