(A) OPM-2 cells were cultured at 37 or 43°C for the indicated time periods. The cells were then cultured at 37°C for another 24 hours. Bortezomib (BTZ) was added at 10 nM as indicated. The protein levels of CHOP, IRF4, Pim-2, c-Myc and Mcl-1 were analyzed by Western blotting. (B) RPMI8226 and OPM-2 cells were cultured at 37 or 43°C for 30 minutes. The cells were further cultured at 37°C for 48 hours. BTZ was added at 10 nM as indicated. Cell viability was analyzed by a WST-8 assay. *p < 0.05. (C) KMS-11 and OPM-2 cells were cultured at 37 or 43°C for 30 minutes. The cells were further cultured at 37°C for 24 hours. The Pim inhibitor SMI-16a was added at 50 μM as indicated. The protein levels of CHOP, IRF4 and c-Myc were analyzed by Western blotting. (D) KMS-11 and OPM-2 cells were cultured at 37 or 43°C for 30 minutes. The cells were further cultured at 37°C for 48 hours. The Pim inhibitor SMI-16a was added at 50 μM as indicated. Cell viability was analyzed by WST-8 assay. *p < 0.05. HT, heat treatment.