Meis1-mediated apoptosis is caspase dependent and can be suppressed by coexpression of HoxA9 in murine and human cell lines.
Coexpression of the homeodomain protein Meis1 and either HoxA7 or HoxA9 is characteristic of many acute myelogenous leukemias. Although Meis1 can be overexpressed in bone marrow long-term repopulating cells, it is incapable of mediating their transformation. Although overexpressing HoxA9 alone transforms murine bone marrow cells, concurrent Meis1 overexpression greatly accelerates oncogenesis. Meis1-HoxA9 cooperation suppresses several myeloid differentiation pathways. We now report that Meis1 overexpression strongly induces apoptosis in a variety of cell types in vitro through a caspase-dependent process. Meis1 requires a functional homeodomain and Pbx-interaction motif to induce apoptosis. Coexpressing HoxA9 with Meis1 suppresses this apoptosis and provides protection from several apoptosis inducers. Pbx1, another Meis1 cofactor, also induces apoptosis; however, coexpressing HoxA9 is incapable of rescuing Pbx-mediated apoptosis. This resistance to apoptotic stimuli, coupled with the previously reported ability to suppress multiple myeloid differentiation pathways, would provide a strong selective advantage to Meis1-HoxA9 coexpressing cells in vivo, leading to leukemogenesis.
Department of Microbiology and Immunology, Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University, 233 S 10th St, Philadelphia, PA 19107-5541, USA.
Peter J
PJ
Wermuth
Arthur M
AM
Buchberg
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007951:Leukemia, Myeloid; D051379:Mice; D008954:Models, Biological; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000502:physiology*; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
D015853:Cysteine Proteinase Inhibitors; D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; C000616392:Meis1 protein, mouse; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D011994:Recombinant Proteins; C097899:homeobox protein HOXA9; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases