title: Tumor-associated antigen preferentially expressed antigen of melanoma (PRAME) induces caspase-independent cell death in vitro and reduces tumorigenicity in vivo.
abstract: Preferentially expressed antigen of melanoma (PRAME) is expressed in a wide variety of tumors, but in contrast with most other tumor associated antigens, it is also expressed in leukemias. The physiologic role of PRAME remains elusive. Interestingly, PRAME expression is correlated with a favorable prognosis in childhood acute leukemias. Moreover, a high expression of PRAME seems to be predominantly found in acute leukemias carrying a favorable prognosis. On these clinical observations, we assumed that PRAME could be involved in the regulation of cell death or cell cycle. In this study, we show that transient overexpression of PRAME induces a caspase-independent cell death in cultured cell lines (CHO-K1 and HeLa). Cells stably transfected with PRAME also exhibit a decreased proliferation rate due, at least partially, to an elevated basal rate of cell death. Immunocytochemistry of a FLAG-tagged PRAME, in vivo imaging of an enhanced green fluorescent protein-tagged PRAME, and Western blotting after cell fractionation reveal a nuclear localization of the protein. Using a microarray-based approach, we show that KG-1 leukemic cells stably transfected with PRAME present a significant decrease of expression of the heat-shock protein Hsp27, the cyclin-dependent kinase inhibitor p21, and the calcium-binding protein S100A4. The expression of these three proteins is known to inhibit apoptosis and has been associated with an unfavorable prognosis in a series of cancers. Finally, repression of PRAME expression by a short interfering RNA strategy increases tumorigenicity of K562 leukemic cells in nude mice. We suggest that all these observations might explain the favorable prognosis of the leukemias expressing high levels of PRAME.
authors.affiliation: Laboratory of Cell Physiology, Center for Human Genetics, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Tajeddine
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Gala
authors.forename: Magali
authors.initials: M
authors.lastname: Louis
authors.forename: Monique
authors.initials: M
authors.lastname: Van Schoor
authors.forename: Bertrand
authors.initials: B
authors.lastname: Tombal
authors.forename: Philippe
authors.initials: P
authors.lastname: Gailly
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017209:Apoptosis / Q000502:physiology*; D016466:CHO Cells; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D048708:Cell Growth Processes / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D006224:Cricetinae; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015536:Down-Regulation; D055551:HSP27 Heat-Shock Proteins; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D020014:K562 Cells; D051379:Mice; D008819:Mice, Nude; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection
chemical_list: D000951:Antigens, Neoplasm; C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; C404944:PRAME protein, human; D011993:Recombinant Fusion Proteins; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C470944:S100a4 protein, mouse; C077591:S100A4 protein, human; D020169:Caspases