Overexpression of MYC and EZH2 cooperates to epigenetically silence MST1 expression.
Hippo-like MST1 protein kinase regulates cell growth, organ size, and carcinogenesis. Reduction or loss of MST1 expression is implicated in poor cancer prognosis. However, the mechanism leading to MST1 silencing remains elusive. Here, we report that both MYC and EZH2 function as potent suppressors of MST1 expression in human prostate cancer cells. We demonstrated that concurrent overexpression of MYC and EZH2 correlated with the reduction or loss of MST1 expression, as shown by RT-qPCR and immunoblotting. Methylation sensitive PCR and bisulfite genomic DNA sequencing showed that DNA methylation caused MST1 silencing. Pharmacologic and RNAi experiments revealed that MYC and EZH2 silenced MST1 expression by inhibiting its promoter activity, and that EZH2 was a mediator of the MYC-induced silencing of MST1. In addition, MYC contributed to MST1 silencing by partly inhibiting the expression of microRNA-26a/b, a negative regulator of EZH2. As shown by ChIP assays, EZH2-induced DNA methylation and H3K27me3 modification, which was accompanied by a reduced H3K4me3 mark and RNA polymerase II occupancy on the MST1 promoter CpG region, were the underlying cause of MST1 silencing. Moreover, potent pharmacologic inhibitors of MYC or EZH2 suppressed prostate cancer cell growth in vitro, and the knockdown of MST1 caused cells' resistance to MYC and EZH2 inhibitor-induced growth retardation. These findings indicate that MYC, in concert with EZH2, epigenetically attenuates MST1 expression and suggest that the loss of MST1/Hippo functions is critical for the MYC or EZH2 mediation of cancer cell survival.
Department of Medicine, Division of Hematology and Oncology; Biomedical Sciences, Division of Cancer Biology and Therapeutics; The Uro-Oncology Program; Samuel Oschin Comprehensive Cancer Institute; Cedars-Sinai Medical Center; Los Angeles, CA USA.
Gamze
G
Kuser-Abali
Department of Medicine, Division of Hematology and Oncology; Biomedical Sciences, Division of Cancer Biology and Therapeutics; The Uro-Oncology Program; Samuel Oschin Comprehensive Cancer Institute; Cedars-Sinai Medical Center; Los Angeles, CA USA.
Ahmet
A
Alptekin
Department of Medicine, Division of Hematology and Oncology; Biomedical Sciences, Division of Cancer Biology and Therapeutics; The Uro-Oncology Program; Samuel Oschin Comprehensive Cancer Institute; Cedars-Sinai Medical Center; Los Angeles, CA USA; Department of Medicine; David Geffen School of Medicine; University of California Los Angeles; Los Angeles, CA USA.
Bekir
B
Cinar
D045744:Cell Line, Tumor; D049109:Cell Proliferation; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008745:Methylation; D063151:Polycomb Repressive Complex 2 / Q000235:genetics* / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D000099317:Hippo Kinases
D000071221:Enhancer of Zeste Homolog 2 Protein; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D063151:Polycomb Repressive Complex 2; D017346:Protein Serine-Threonine Kinases; D016271:Proto-Oncogene Proteins c-myc; C498409:EZH2 protein, human; C095566:STK4 protein, human; D000099317:Hippo Kinases
DNA methylation; EZH2 and MST1/Hippo; H3K27me3; MYC; epigenetics