title: Targeting MAGE-C1/CT7 expression increases cell sensitivity to the proteasome inhibitor bortezomib in multiple myeloma cell lines.
abstract: The MAGE-C1/CT7 encodes a cancer/testis antigen (CTA), is located on the chromosomal region Xq26-27 and is highly polymorphic in humans. MAGE-C1/CT7 is frequently expressed in multiple myeloma (MM) that may be a potential target for immunotherapy in this still incurable disease. MAGEC1/CT7 expression is restricted to malignant plasma cells and it has been suggested that MAGE-C1/CT7 might play a pathogenic role in MM; however, the exact function this protein in the pathophysiology of MM is not yet understood. Our objectives were (1) to clarify the role of MAGE-C1/CT7 in the control of cellular proliferation and cell cycle in myeloma and (2) to evaluate the impact of silencing MAGE-C1/CT7 on myeloma cells treated with bortezomib. Myeloma cell line SKO-007 was transduced for stable expression of shRNA-MAGE-C1/CT7. Downregulation of MAGE-C1/CT7 was confirmed by real time quantitative PCR and western blot. Functional assays included cell proliferation, cell invasion, cell cycle analysis and apoptosis. Western blot showed a 70-80% decrease in MAGE-C1/CT7 protein expression in inhibited cells (shRNA-MAGE-C1/CT7) when compared with controls. Functional assays did not indicate a difference in cell proliferation and DNA synthesis when inhibited cells were compared with controls. However, we found a decreased percentage of cells in the G2/M phase of the cell cycle among inhibited cells, but not in the controls (p<0.05). When myeloma cells were treated with bortezomib, we observed a 48% reduction of cells in the G2/M phase among inhibited cells while controls showed 13% (empty vector) and 9% (ineffective shRNA) reduction, respectively (p<0.01). Furthermore, inhibited cells treated with bortezomib showed an increased percentage of apoptotic cells (Annexin V+/PI-) in comparison with bortezomib-treated controls (p<0.001). We found that MAGE-C1/CT7 protects SKO-007 cells against bortezomib-induced apoptosis. Therefore, we could speculate that MAGE-C1/CT7 gene therapy could be a strategy for future therapies in MM, in particular in combination with proteasome inhibitors.
authors: Disciplina de Hematologia e Hemoterapia, Universidade Federal de São Paulo, São Paulo, Brazil. fcarvalho@unifesp.br
authors: Fabricio
authors: F
authors: de Carvalho
authors: Erico T
authors: ET
authors: Costa
authors: Anamaria A
authors: AA
authors: Camargo
authors: Juliana C
authors: JC
authors: Gregorio
authors: Cibele
authors: C
authors: Masotti
authors: Valeria C C
authors: VC
authors: Andrade
authors: Bryan E
authors: BE
authors: Strauss
authors: Otavia L
authors: OL
authors: Caballero
authors: Djordje
authors: D
authors: Atanackovic
authors: Gisele W B
authors: GW
authors: Colleoni
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D020868:Gene Silencing; D006801:Humans; D009101:Multiple Myeloma / Q000235:genetics / Q000473:pathology*; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000172:deficiency* / Q000235:genetics*; D011480:Protease Inhibitors / Q000494:pharmacology*; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D001897:Boronic Acids; C110905:MAGEC1 protein, human; D009363:Neoplasm Proteins; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D034741:RNA, Small Interfering; D000069286:Bortezomib