title: Blocking EZH2 methylation transferase activity by GSK126 decreases stem cell-like myeloma cells.
abstract: EZH2 is a critical epigenetic regulator that is deregulated in various types of cancers including multiple myeloma (MM). In the present study, we hypothesized that targeting EZH2 might induce apoptosis in myeloma cells including stem cell-like cells (CSCs). We investigated the effect of EZH2 inhibition on MM cells using a potent inhibitor (GSK126). The results showed that GSK126 effectively abrogated the methylated histone 3 (H3K27me3) level in MM.1S and LP1 cells, and inhibited the number of live cells and colony formation in soft agar of six MM cell lines. GSK126 induced massive apoptosis in MM.1S, LP1 and RPMI8226 cells. Progressive release of mitochondrial cytochrome c and AIF into the cytosol was detected in GSK126-treated MM cells. GSK126 treatment elicited caspase-3-dependent MCL-1 cleavage with accumulation of proapoptotic truncated MCL-1. These results suggested that GSK126 triggers the intrinsic mitochondrial apoptosis pathway. Enhanced apoptosis was observed in the combination of GSK126 with bortezomib. Using ALDH and side population (SP) assays to characterize CSCs, we found that GSK126 eliminated the stem-like myeloma cells by blocking the Wnt/β-catenin pathway. The in vivo anti-tumor effect of GSK126 was confirmed by using RPMI8226 cells in a xenograft mouse model. In conclusion, our findings suggest that EZH2 inactivation by GSK126 is effective in killing MM cells and CSCs as a single agent or in combination with bortezomib. Clinical trial of GSK126 in patients with MM may be warranted.
authors.affiliation: Jinan University Institute of Tumor Pharmacology, College of Pharmacy, Jinan University, Guangzhou, China.
authors.forename: Delong
authors.initials: D
authors.lastname: Zeng
authors.affiliation: Jinan University Institute of Tumor Pharmacology, College of Pharmacy, Jinan University, Guangzhou, China.
authors.forename: Maoxing
authors.initials: M
authors.lastname: Liu
authors.affiliation: Jinan University Institute of Tumor Pharmacology, College of Pharmacy, Jinan University, Guangzhou, China.
authors.forename: Jingxuan
authors.initials: J
authors.lastname: Pan
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D000069286:Bortezomib / Q000494:pharmacology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D004357:Drug Synergism; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009101:Multiple Myeloma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism*; D059748:Proteolysis; D011728:Pyridones / Q000494:pharmacology*; D060449:Wnt Signaling Pathway / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: C577920:GSK-2816126; D007211:Indoles; C579095:MCL1 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011728:Pyridones; D000069286:Bortezomib; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein
keywords: EZH2 inhibitor; GSK126; apoptosis; cancer stem cells; multiple myeloma