RESUMO
BACKGROUND & AIMS: Overexpression of FoxM1 correlates with poor prognosis in hepatocellular carcinoma (HCC). Moreover, the Ras-signaling pathway is found to be ubiquitously activated in HCC through epigenetic silencing of the Ras-regulators. We investigated the roles of FoxM1 in Ras-driven HCC, and on HCC cells with stem-like features. METHODS: We employed a transgenic mouse model that expresses the oncogenic Ras in the liver. That strain was crossed with a strain that harbor floxed alleles of FoxM1 and the MxCre gene that allows conditional deletion of FoxM1. FoxM1 alleles were deleted after development of HCC, and the effects on the tumors were analyzed. Also, FoxM1 siRNA was used in human HCC cell lines to determine its role in the survival of the HCC cells with stem cell features. RESULTS: Ras-driven tumors overexpress FoxM1. Deletion of FoxM1 inhibits HCC progression. There was increased accumulation of reactive oxygen species (ROS) in the FoxM1 deleted HCC cells. Moreover, FoxM1 deletion caused a disproportionate loss of the CD44+ and EpCAM+ HCC cells in the tumors. We show that FoxM1 directly activates expression of CD44 in human HCC cells. Moreover, the human HCC cells with stem cell features are addicted to FoxM1 for ROS-regulation and survival. CONCLUSION: Our results provide genetic evidence for an essential role of FoxM1 in the progression of Ras-driven HCC. In addition, FoxM1 is required for the expression of CD44 in HCC cells. Moreover, FoxM1 plays a critical role in the survival of the HCC cells with stem cell features by regulating ROS.
Assuntos
Carcinogênese/genética , Carcinoma Hepatocelular/genética , Fatores de Transcrição Forkhead/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias Hepáticas/genética , Células-Tronco/patologia , Proteínas ras/genética , Animais , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Linhagem Celular Tumoral , Proliferação de Células , Progressão da Doença , Proteína Forkhead Box M1 , Fatores de Transcrição Forkhead/biossíntese , Humanos , Imuno-Histoquímica , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Prognóstico , Transdução de Sinais , Células-Tronco/metabolismo , Proteínas ras/biossínteseRESUMO
The forkhead box transcription factor FOXM1 is considered to be a promising target for cancer therapy. However, the significance of FOXM1 in tumors harboring mutation in p53, which is very common, is unclear. In this study, we investigated the efficacy of FoxM1 targeting in spontaneous p53-null tumors using genetic ablation as well as using a peptide inhibitor of FOXM1. We show that conditional deletion of FoxM1 inhibits growth of the p53-null thymic lymphoma and sarcoma cells. In addition, deletion of FoxM1 induces apoptotic cell death of the p53-null tumors, accompanied by reduced expression of the FOXM1 target genes survivin and Bmi1. An ARF-derived peptide that inhibits the activity of FOXM1, by targeting it to the nucleolus, also induces apoptosis in the p53-null sarcoma and lymphoma, leading to a strong inhibition of their metastatic colonization. Together, our observations suggest that FOXM1 is critical for survival and growth of the p53-null lymphoma and sarcoma and provide proof-of-principle that FOXM1 is an effective therapeutic target for sarcoma and lymphoma carrying loss of function mutation in p53.
Assuntos
Fatores de Transcrição Forkhead/antagonistas & inibidores , Linfoma/genética , Linfoma/metabolismo , Sarcoma/genética , Sarcoma/metabolismo , Proteína Supressora de Tumor p53/genética , Aloenxertos , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Inibidor p16 de Quinase Dependente de Ciclina/química , Modelos Animais de Doenças , Proteína Forkhead Box M1 , Fatores de Transcrição Forkhead/genética , Regulação Neoplásica da Expressão Gênica , Proteínas Inibidoras de Apoptose/genética , Proteínas Inibidoras de Apoptose/metabolismo , Camundongos , Camundongos Knockout , Peptídeos/farmacologia , Complexo Repressor Polycomb 1/genética , Complexo Repressor Polycomb 1/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Survivina , Neoplasias do Timo/genética , Neoplasias do Timo/metabolismoRESUMO
Elevated expression of FoxM1 in breast cancer correlates with an undifferentiated tumor phenotype and a negative clinical outcome. However, a role for FoxM1 in regulating mammary differentiation was not known. Here, we identify another function of FoxM1, the ability to act as a transcriptional repressor, which plays an important role in regulating the differentiation of luminal epithelial progenitors. Regeneration of mammary glands with elevated levels of FoxM1 leads to aberrant ductal morphology and expansion of the luminal progenitor pool. Conversely, knockdown of FoxM1 results in a shift toward the differentiated state. FoxM1 mediates these effects by repressing the key regulator of luminal differentiation, GATA-3. Through association with DNMT3b, FoxM1 promotes methylation of the GATA-3 promoter in an Rb-dependent manner. This study identifies FoxM1 as a critical regulator of mammary differentiation with significant implications for the development of aggressive breast cancers.
Assuntos
Linhagem da Célula , Fatores de Transcrição Forkhead/metabolismo , Glândulas Mamárias Animais/metabolismo , Glândulas Mamárias Animais/patologia , Glândulas Mamárias Humanas/metabolismo , Glândulas Mamárias Humanas/patologia , Animais , Sequência de Bases , Sítios de Ligação , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Diferenciação Celular , Linhagem Celular Tumoral , Proliferação de Células , DNA (Citosina-5-)-Metiltransferases , Metilação de DNA/genética , Feminino , Proteína Forkhead Box M1 , Fator de Transcrição GATA3/metabolismo , Técnicas de Silenciamento de Genes , Humanos , Glândulas Mamárias Animais/crescimento & desenvolvimento , Glândulas Mamárias Humanas/crescimento & desenvolvimento , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Gravidez , Regiões Promotoras Genéticas/genética , Proteína do Retinoblastoma/metabolismo , Transcrição Gênica , DNA Metiltransferase 3BRESUMO
Inherent and acquired therapeutic resistance in breast cancer remains a major clinical challenge. In human breast cancer samples, overexpression of the oncogenic transcription factor FoxM1 has been suggested to be a marker of poor prognosis. In this study, we report that FoxM1 overexpression confers resistance to the human epidermal growth factor receptor 2 monoclonal antibody Herceptin and microtubule-stabilizing drug paclitaxel, both as single agents and in combination. FoxM1 altered microtubule dynamics to protect tumor cells from paclitaxel-induced apoptosis. Mechanistic investigations revealed that the tubulin-destabilizing protein Stathmin, whose expression also confers resistance to paclitaxel, is a direct transcriptional target of FoxM1. Significantly, attenuating FoxM1 expression by small interfering RNA or an alternate reading frame (ARF)-derived peptide inhibitor increased therapeutic sensitivity. Our findings indicate that targeting FoxM1 could relieve therapeutic resistance in breast cancer.
