(A) RPMI8226, KMS-11 and OPM-2 cells were cultured at 37 or 43°C for the indicated time periods. After the heat treatment, the MM cells were further cultured at 37°C for 24 hours. The cells were stained with annexin V-FITC and propidium iodide (PI), and then analyzed by flow cytometry. (B) MM cell lines were cultured at 37, 41, 43 or 45°C for 10, 30 and 60 minutes. After the heat treatment, the MM cells were further cultured at 37°C for 24 hours. Cell viability was then analyzed by a WST-8 assay. (C) PBMCs from two normal donors were cultured at 37, 41, 43 or 45°C for 10, 30 and 60 minutes. Cell viability was then analyzed by a WST-8 assay.