RESUMO
While ß-catenin has been demonstrated as an essential molecule and therapeutic target for various cancer stem cells (CSCs) including those driven by MLL fusions, here we show that transcriptional memory from cells of origin predicts AML patient survival and allows ß-catenin-independent transformation in MLL-CSCs derived from hematopoietic stem cell (HSC)-enriched LSK population but not myeloid-granulocyte progenitors. Mechanistically, ß-catenin regulates expression of downstream targets of a key transcriptional memory gene, Hoxa9 that is highly enriched in LSK-derived MLL-CSCs and helps sustain leukemic self-renewal. Suppression of Hoxa9 sensitizes LSK-derived MLL-CSCs to ß-catenin inhibition resulting in abolishment of CSC transcriptional program and transformation ability. In addition, further molecular and functional analyses identified Prmt1 as a key common downstream mediator for ß-catenin/Hoxa9 functions in LSK-derived MLL-CSCs. Together, these findings not only uncover an unexpectedly important role of cells of origin transcriptional memory in regulating CSC self-renewal, but also reveal a novel molecular network mediated by ß-catenin/Hoxa9/Prmt1 in governing leukemic self-renewal.
Assuntos
Regulação Leucêmica da Expressão Gênica , Proteínas de Homeodomínio/genética , Leucemia Mieloide Aguda/genética , Células-Tronco Neoplásicas/metabolismo , Transcrição Gênica , beta Catenina/genética , Animais , Antígenos Ly/genética , Antígenos Ly/metabolismo , Proliferação de Células , Sobrevivência Celular , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/patologia , Proteínas de Homeodomínio/antagonistas & inibidores , Proteínas de Homeodomínio/metabolismo , Humanos , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/mortalidade , Leucemia Mieloide Aguda/patologia , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neoplásicas/patologia , Proteína-Arginina N-Metiltransferases/genética , Proteína-Arginina N-Metiltransferases/metabolismo , Proteínas Proto-Oncogênicas c-kit/genética , Proteínas Proto-Oncogênicas c-kit/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Transdução de Sinais , Análise de Sobrevida , beta Catenina/metabolismoRESUMO
AIMS: FK506-binding protein (FKBP) 12 is an inhibitor of transforming growth factor (TGF)-beta type I receptors. Several lines of evidence support the view that TGF-beta stimulates vascular smooth muscle cell (VSMC) proliferation and matrix accumulation. We investigated the effect of FK506, also known as tacrolimus, on cellular proliferation and on matrix protein production in human VSMCs. METHODS AND RESULTS: We measured cell proliferation with flow cytometry using BrdU incorporation and fluorimetrically by measuring DNA concentration with Hoechst 33258. Western blot assay of whole-cell lysates was used to measure the levels of signalling proteins involved in proliferative pathways, in particular beta-catenin, pErk, pAkt, pmTOR, and cyclin D1. Collagen synthesis was also investigated by Western blotting. The TGF-beta signal was studied by both Western blotting and confocal microscopy. We used the SiRNA technique for FKBP12 gene silencing. Our results show that FK506 stimulates VSMC proliferation and collagen type I production. FK506 enhanced beta-catenin levels and activated the extracellular signal-regulated kinase, Akt, and mammalian target of rapamycin kinase, which are important effectors of proliferation. Accordingly, cyclin D1 expression was increased. We also demonstrate that FK506 activates the TGF-beta signal in VSMCs and that, through this mechanism, it stimulates cell proliferation. CONCLUSION: FK506 can act as a growth factor for VSMCs.
Assuntos
Fármacos Cardiovasculares/farmacologia , Proliferação de Células/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Miócitos de Músculo Liso/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Tacrolimo/farmacologia , Fator de Crescimento Transformador beta1/metabolismo , Receptores de Ativinas/antagonistas & inibidores , Receptores de Ativinas/metabolismo , Benzamidas/farmacologia , Células Cultivadas , Colágeno Tipo I/metabolismo , Replicação do DNA/efeitos dos fármacos , Dioxóis/farmacologia , Relação Dose-Resposta a Droga , Humanos , Músculo Liso Vascular/metabolismo , Miócitos de Músculo Liso/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Serina-Treonina Quinases TOR , Proteína 1A de Ligação a Tacrolimo/metabolismo , Fatores de Tempo , beta Catenina/metabolismoRESUMO
BACKGROUND: Loss of response to transforming growth factor-beta (TGF-beta ) is thought to contribute to the progression of chronic lymphocytic leukemia. Recent findings of over-activation of the TGF-beta signal in FKBP12-knockout mouse prompted us to investigate whether FK506, the canonical ligand of FKBP, can activate the TGF-beta signal in chronic lymphocytic leukemia. DESIGN AND METHODS: We studied 62 chronic lymphocytic leukemia samples from patients with Rai/Binet stage 0 to 4 disease. The TGF-beta signal was investigated by western blotting and flow cytometry. The levels of Bcl2-family members and death-associated-protein kinase were also investigated by western blotting, whereas apoptosis was studied in flow cytometry. Down-modulation of FKBP12 was obtained by gene silencing with short interfering RNA. RESULTS: Twenty-two out of 62 chronic lymphocytic leukemia samples were sensitive to TGF-beta-induced apoptosis. All but two of the responsive samples underwent apoptosis also when cultured with FK506, but not with cyclosporine. Thirteen samples that were not sensitive to TGF-beta were sensitive to FK506. Overall, response to FK506 occurred in 33 samples. FK506 induced Smad2 phosphorylation and nuclear translocation. Accordingly, death-associated-protein kinase, a transcriptional target of Smad, was induced. At the same time, Bcl-2 and Bcl-xL levels decreased whereas the levels of Bim and Bmf increased. A loss of mitochondrial membrane potential preceded caspase activation and cell death. FK506 removed FKBP12 from its binding to the TGF-beta-receptor. FKBP12 release activated the receptor-kinase activity as suggested by the enhanced levels of phospho-Smad found in cells depleted of FKBP12. CONCLUSIONS: Our study shows that most chronic lymphocytic leukemia cells escape the homeostatic control of TGF-beta and that FK506 restores the TGF-beta signal in a proportion of non-responsive samples. We demonstrated that FK506 activates TGF-beta receptor I kinase activity in chronic lymphocytic leukemia, which transduces apoptosis by a mitochondrial-dependent pathway.