RESUMO
Cell division cycle 25A (Cdc25A) was shown to colocalise both with nuclear and cytoplasmic proteins. Recently, we have demonstrated that overexpressed Cdc25A promoted the survival of rat 423 cells through indirect activation of PKB-protein kinase B. Using a Cdc25A:ER fusion protein, which can be shuttled from the cytoplasm into the nucleus, the present investigation evidences that the antiapoptotic effect of Cdc25A was restricted to its cytoplasmic localisation in rat 423 cells. In contrast, nuclear Cdc25A overexpression caused dephosphorylation and nuclear retention of the proapoptotic transcription factor Forkhead in rhabdomyosarcoma-like 1 (FKHRL1) in human N.1 ovarian carcinoma cells. This resulted in the increased constitutive expression of the FKHRL1 targets Fas ligand and Bim, and promoted apoptosis. Thus, the Cdc25A oncogene, which was found to be frequently overexpressed in certain human cancers, can increase or decrease the susceptibility to apoptosis depending on the cell-type-specific subcellular distribution.
Assuntos
Apoptose/fisiologia , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas Recombinantes/metabolismo , Fatores de Transcrição/metabolismo , Fosfatases cdc25/metabolismo , Animais , Apoptose/efeitos dos fármacos , Fusão Gênica Artificial , Compartimento Celular , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Proteína Forkhead Box O1 , Proteína Forkhead Box O3 , Fatores de Transcrição Forkhead , Vetores Genéticos , Humanos , Proteínas do Tecido Nervoso , Ratos , Receptores de Estrogênio/genética , Receptores de Estrogênio/metabolismo , Proteínas Recombinantes/genética , Transformação Genética , Fator de Necrose Tumoral alfa/farmacologia , Fosfatases cdc25/genéticaAssuntos
Transformação Celular Neoplásica/genética , Proteínas Nucleares/genética , Proteínas Tirosina Quinases/genética , Receptores Proteína Tirosina Quinases/genética , Quinase do Linfoma Anaplásico , Animais , Divisão Celular , Genes ras , Linfoma Anaplásico de Células Grandes/genética , Proteínas Nucleares/metabolismo , Nucleofosmina , Fragmentos de Peptídeos , Ratos , Receptores Proteína Tirosina Quinases/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismoRESUMO
Trimidox (3,4,5-trihydroxybenzohydroxamidoxime), a recently synthesized inhibitor of ribonucleotide reductase (RR), was shown to exert anti-proliferative activities in HL-60 and K562 human leukemia cell lines and to prolong the life span of mice inoculated with L1210 mouse leukemia cells. Here we test whether trimidox also exhibits anti-neoplastic properties in ovarian carcinoma cells. Since the mode of action of trimidox on cell fate has not been investigated so far, we addressed this unresolved item and find that this polyhydroxybenzoic acid derivative induces apoptosis of N.1 human ovarian carcinoma cells when tested in growth factor deprived medium. Utilizing an improved analysis, based on Hoechst 33258/propidium iodide double staining, apoptosis is quantified and discriminated from necrosis. Trimidox induces c-myc expression, which is indispensible for apoptosis of N.1 cells, and expression of plasminogen activator/urokinase type (upa), which supports the apoptotic process under more physiological conditions. Surprisingly, trimidox does not block dNTP synthesis in N.1 cells at the concentrations tested and, therefore, trimidox induces apoptosis independent of RR-inhibition. Like TNFalpha or benzamide riboside, which are also inducers of apoptosis of N.1 cells, trimidox also down-regulates the G1 cell cycle phosphatase cdc25A, whereas cyclin D1 becomes up-regulated. This report shows that trimidox destroys human ovarian carcinoma cells by inducing them to undergo apoptosis as well as corroborating previous investigations which demonstrated that apoptosis of these cells depends on c-myc over-expression when survival factors are withdrawn.