Figure S1. Bone marrow-derived macrophages enrich MM TICs. Figure S2. IL-1β promotes MM-TIC enrichment. Figure S3. Reduced survival in MM patients with high levels of M1 pro-inflammatory macrophages and TICs. Table S1: Patient characteristics and treatment description Table S2. Panel of antibodies and isotype conjugates used in CyTOF.
ARTICLE ABSTRACT
Multiple myeloma (MM) is a plasma cell neoplasia commonly treated with proteasome inhibitors such as bortezomib. Although bortezomib has demonstrated enhanced survival benefit, some patients relapse and subsequently develop resistance to such therapy. Here, we investigate the mechanisms underlying relapse and refractory MM following bortezomib treatment. We show that bortezomib-exposed proinflammatory macrophages promote an enrichment of MM-tumor-initiating cells (MM-TIC) both in vitro and in vivo. These effects are regulated in part by IL1β, as blocking the IL1β axis by a pharmacologic or genetic approach abolishes bortezomib-induced MM-TIC enrichment. In MM patients treated with bortezomib, high proinflammatory macrophages in the bone marrow negatively correlate with survival rates (HR, 1.722; 95% CI, 1.138–2.608). Furthermore, a positive correlation between proinflammatory macrophages and TICs in the bone marrow was also found. Overall, our results uncover a protumorigenic cross-talk involving proinflammatory macrophages and MM cells in response to bortezomib therapy, a process that enriches the MM-TIC population.
Our findings suggest that proinflammatory macrophages in bone marrow biopsies represent a potential prognostic biomarker for acquired MM resistance to bortezomib therapy.
