In HRP2-depleted LP-1 cells that were bortezomib resistant, administration of an inhibitor of tazemetostat, an inhibitor of the H3K27me3-catalyzing enzyme EZH2, failed to kill MM cells even at a very high dosage; however, it markedly improved the anti-MM effects of bortezomib (Figure 7A), and the combination effect was synergistic (Figure 7B). The gene discussed is HDGFL2; the disease is Miyoshi myopathy.