Lower FA uptake promotes proliferation, whereas higher FA uptake results in lipotoxicity through a ferroptosis pathway. (A) AA concentration (nanograms per milliliter) in BM supernatant of patients with MGUS (n = 14), SMM (n = 12), NDMM (n = 22), and RRMM (n = 17) and healthy controls (HD) (n = 7) measured by using an enzyme-linked immunosorbent assay. (B) Dose-dependent effect of AA on cell proliferation in myeloma cell line 5TGM1 quantified by CyQUANT assay after 72 hours of treatment. (C) Effect of AA on cell viability in myeloma cell line 5TGM1 assessed by CellTiter-Glo Assay after 72 hours of treatment. (D) Cell viability of 5TGM1 cells in the presence of linoleic acid assessed by Cell Titer Glow assay after 72 hours of treatment. (E) Effect of AA on human (H929, MM1S, and U266) MM cell proliferation at higher concentrations after 72 hours of treatment. (F) Flow cytometric analysis of lipid peroxidation measured by BODIPY-11C fluorescence in MM.1S after exposure to 100 μM AA for 24 hours. (G) Tumor plasmacytoma model in SCID mice was generated. MM1S (2.5 × 10⁶) cells were injected subcutaneously in the intra-scapular region of mice (n = 10 per group), and the tumor treated with AA (500 μg/g). Tumor growth kinetics is represented for a period of 41 days. PBS was used as vehicle and control. (H) Expression of proliferation marker Ki67 in tumor tissues was determined by immunohistochemistry for groups treated with vehicle and AA (500 μg/g). (I) Apoptosis-inducing AA-signaling pathways in MM cells were investigated. Inhibition of different AA metabolic pathways in MM.1S cells were investigated by using ibuprofen, baicalein, BW B70C, 1-aminobenzotriazole, and ferrostatin; relative cell viability was measured by using an MTT assay. (J) Flow cytometric panel representation of GPX-4 and Lipid ROX modulation by AA and relative recovery by ferrostatin. Data are presented as mean ± standard error of the mean. *P < .05. DMSO, dimethyl sulfoxide.