RASSF4 functions as a tumor suppressor in Multiple Myeloma

Autor: E. De Smedt, Dirk Hose, Eline Menu, L.A. van Grunsven, Stefaan Verhulst, E. De Bruyne, E Van Valckenborgh, Ken Maes, Jérôme Moreaux, Carlo Heirman, Karine Breckpot
Přispěvatelé: Basic (bio-) Medical Sciences, Liver Cell Biology, Laboratory of Molecullar and Cellular Therapy, Faculty of Medicine and Pharmacy, Translational Liver Cell Biology, Hematology
Rok vydání: 2015
Předmět:
Zdroj: Clinical Lymphoma Myeloma and Leukemia. 15:e227
ISSN: 2152-2650
DOI: 10.1016/j.clml.2015.07.486
Popis: Despite the enormous advances that have been made in the treatment of the plasma cell malignancy multiple myeloma (MM) this disease remains most often fatal. RAS, a family of GTPase genes, is frequently mutated in MM patients (20-45%). It has been shown that RAS oncoproteins, next to their classical roles in stimulating growth and survival, also have tumor suppressive effects. These effects are partially mediated through the Ras-Association Domain Family (RASSF), a group of 10 proteins and numerous isoforms. These tumor suppressors are often silenced in cancer cells due to methylation of the promotor. So far, however, no data about RASSF proteins is available in MM. Here, we investigated the expression and role of RASSF4 in MM. Using gene expression profiling data of 2 independent patient cohorts, we found that RASSF4 expression is significantly downregulated in MM cells compared to healthy bone marrow plasma cells and that a low expression at time of diagnosis associates with a bad prognosis. In addition, treatment with the histone deacetylase inhibitor quisinostat and/or the DNA methyltransferase inhibitor decitabine significantly increased RASSF4 expression both in vitro and in vivo, thus indicating that epigenetic modifications are involved in this silencing. Next, to elucidate the biological role of RASSF4 in MM we used a conditional lentiviral delivery system. Tree human myeloma cell lines (HMCL), namely AMO1, JJN3 and the IL-6 dependent cell line XG7, were transduced with either the empty pLenti 6.3 vector (control) or pLenti6.3 huRASSF4. Overexpression of RASSF4 in the HMCL revealed that RASSF4 has a strong negative effect on MM cell viability and potently induces apoptosis. This induction of apoptosis was found to be caspase-3 mediated. In addition, RASSF4 was found to inhibit the clonogenic capacity of the HMCL. Mechanistically, immunofluorescence stainingfor RASSF4 showed that RASSF4 is co-localized with the centrosome. In addition, RASSF4 overexpression was found to downregulate the expression of the anti-apoptotic protein Bcl-2. In conclusion, we have identified RASSF4 as a target for epigenetic silencing in MM and demonstrated its tumor suppressive function in MM cells. Further insights into the molecular mechanisms of RASSF4 in MM will continue to be explored both in vitro and in vivo.
Databáze: OpenAIRE
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