Alterations in chromatin modifications, such as histone methylation, have been suggested as mediating chemotherapy resistance in several cancer types; therefore, elucidation of the epigenetic mechanisms that underlie drug resistance may greatly contribute to the advancement of cancer therapies. In the present study, we identified histone H3–lysine 27 (H3K27) as a critical residue for epigenetic modification in multiple myeloma. We determined that abrogation of drug-induced H3K27 hypermethylation is associated with cell adhesion–mediated drug resistance (CAM-DR), which is the most important form of drug resistance, using a coculture system to evaluate stroma cell adhesion–dependent alterations in multiple myeloma cells. Cell adhesion counteracted anticancer drug–induced hypermethylation of H3K27 via inactivating phosphorylation of the transcription regulator EZH2 at serine 21, leading to the sustained expression of antiapoptotic genes, including
Jiro Kikuchi, Daisuke Koyama, Taeko Wada, Tohru Izumi, Peter O. Hofgaard, Bjarne Bogen, Yusuke Furukawa
The IGF-1R inhibitor OSI-906 overcomes CAM-DR in vitro.