Project description:Multiple Myeloma (MM) is a plasma cell tumor localized to the bone marrow (BM). Despite current progress in improving patient outcome, MM remains largely incurable. Disease clonal and interpatient heterogeneity has hampered identification of a common underlying mechanism for disease establishment and have slowed the development of novel targeted therapies. Epigenetic aberrations are now emerging as increasingly important in tumorigenesis, thus selective targeting of crucial epigenetic enzymes may provide new therapeutic potential in cancer including MM. Recently, we and others suggested the histone methyltransferase enhancer of zeste homolog 2 (EZH2), to be a potential therapeutic target in MM. Now we show that pharmacological inhibition of EZH2 suppresses the MM cell growth through downregulation of MM-associated oncogenes; IRF-4, XBP-1, PRDM1/BLIMP-1and c-MYC. We also show that downregulation of these genes is mediated via reactivated expression of microRNAs with tumor suppressor functions; primarily miR125a-3p and miR320c. Using chromatin immunoprecipitation (ChIP) we demonstrate that miR125a-3p and miR320c are targets of EZH2 and H3K27me3 in MM cell lines and primary MM cells. Our results further highlight the importance of polycomb-mediated silencing in MM to include microRNAs with tumor suppressor activity. This novel role further strengthens the oncogenic features of EZH2 and its potential as a therapeutic target in MM.
Project description:Multiple Myeloma (MM) is a plasma cell tumor localized to the bone marrow (BM). Despite current progress in improving patient outcome, MM remains largely incurable. Disease clonal and interpatient heterogeneity has hampered identification of a common underlying mechanism for disease establishment and have slowed the development of novel targeted therapies. Epigenetic aberrations are now emerging as increasingly important in tumorigenesis, thus selective targeting of crucial epigenetic enzymes may provide new therapeutic potential in cancer including MM. Recently, we and others suggested the histone methyltransferase enhancer of zeste homolog 2 (EZH2), to be a potential therapeutic target in MM. Now we show that pharmacological inhibition of EZH2 suppresses the MM cell growth through downregulation of MM-associated oncogenes; IRF-4, XBP-1, PRDM1/BLIMP-1and c-MYC. We also show that downregulation of these genes is mediated via reactivated expression of microRNAs with tumor suppressor functions; primarily miR125a-3p and miR320c. Using chromatin immunoprecipitation (ChIP) we demonstrate that miR125a-3p and miR320c are targets of EZH2 and H3K27me3 in MM cell lines and primary MM cells. Our results further highlight the importance of polycomb-mediated silencing in MM to include microRNAs with tumor suppressor activity. This novel role further strengthens the oncogenic features of EZH2 and its potential as a therapeutic target in MM.
Project description:Epigenetic mechanisms including histone modifications play key roles in the pathogenesis of multiple myeloma (MM). We have previously shown that a histone H3 lysine 27 (H3K27) methyltransferase EZH2 and a H3K9 methyltransferase G9a are potential therapeutic targets in MM. Recent studies suggested that EZH2 and G9a cooperate to regulate gene expression. We thus aimed to evaluate the anti-tumor effect by dual targeting of EZH2 and G9a in MM. A combination of an EZH2 inhibitor and a G9a inhibitor strongly suppressed myeloma cell proliferation through inducing cell cycle arrest and apoptosis in vitro. Dual inhibition of EZH2 and G9a also repressed xenograft formation by myeloma cells in vivo. Higher expression levels of EZH2 and EHMT2, which encodes G9a, are significantly associated with poorer prognosis in MM patients, respectively. Microarray analysis revealed that EZH2/G9a inhibition significantly upregulated interferon (IFN)-stimulated genes and suppressed IRF4-MYC axis genes in myeloma cells. Notably, we found increased expression and reduced H3K27/H3K9 methylation levels of endogenous retrovirus (ERV) genes in myeloma cells with the dual inhibition, suggesting that activation of the ERV genes may cause the IFN response. These results suggest that dual targeting of EZH2 and G9a may be a novel therapeutic strategy in MM.
Project description:MicroRNAs may act as oncogenes or tumour suppressor genes, which make these small molecules potential diagnostic/prognostic factors and targets for anticancer therapies. On account of this, we performed large-scale profiling of microRNA expression in canine mammary cancer.
Project description:Osteolytic destruction is a hallmark of multiple myeloma, resulting from activation of osteoclast mediated bone resorption and reduction of osteoblast-mediated bone formation. However, the molecular mechanism underlying the differentiation and activity of osteoclasts and osteoblasts within a myelomatous microenvironment remains unclear. Here, we demonstrate that the osteocyte-expressed major histocompatibility complex class II transactivator (CIITA) contributes to myeloma-induced bone lesions. CIITA upregulates the secretion of osteolytic cytokines from osteocytes through acetylation at histone 3 lysine 14 in the promoter of TNFSF11 (encoding RANKL) and SOST (encoding sclerostin), leading to enhanced osteoclastogenesis and decreased osteoblastogenesis. In turn, myeloma cell–secreted 2-deoxy-D-ribose, the product of thymidine catalyzed by the function of thymidine phosphorylase, upregulates CIITA expression in osteocytes through the STAT1/IRF1 signaling pathway. Our work thus broadens the understanding of myeloma-induced osteolysis and indicates a potential strategy for disrupting tumor-osteocyte interaction to prevent, or treat patients with, myeloma bone disease.
