RESUMEN
The PTEN/Akt signal pathway plays an important role in tumorigenesis. Mutations or deletions of PTEN have been observed in up to 60% of melanoma cell lines, resulting in PI3K/Akt activation. The Forkhead family of transcription factors induce apoptosis in their unphosphorylated forms and were recently reported to be a substrate of Akt kinase. In the present study, an adenovirus expressing a triple mutant (TM) of FKHRL1, which cannot be phosphorylated by Akt, was assessed for its ability to induce apoptosis in melanoma cells. Marked overexpression of FKHRL1/TM was evident in the SK-MEL-2 cell line 24 hours after infection with Ad-FKHRL1/TM by Western blot analysis. The expression of FKHRL1/ TM was moderately delayed in SK-MEL-28 cells. Overexpression of FKHRL1/TM can efficiently inhibit melanoma cell growth and result in rapid loss of cell viability. Cell cycle analysis showed overexpression of FKHRL1/TM in both melanoma cell lines resulted in development of a Sub-G1 population, indicating apoptosis by Ad-FKHRL1/TM infection. Apoptosis was confirmed by morphologic inspection, poly-ADP-ribosepolymerase (PARP) cleavage assay, and annexin V-PE analysis. After Ad-FKHRL1/TM infection, the expression of Bax and Bak did not differ markedly, whereas Mcl-1 and Bcl-x(L) levels decreased markedly. Involvement of caspase 3 and 6 in FKHRL1/TM-mediated apoptosis was demonstrated by cleavage of caspase 3/CPP32 and PARP as well as fragmentation of the caspase 6 substrate lamin B in SK-MEL-2 cells as early as 24 hours after Ad-FKHRL1/ TM infection, but those events were delayed 72 hours in SK-MEL-28. In addition, we found that p27(kip1) was cleaved in SK-MEL-2 cells at 24 hours after treatment with Ad-FKHRL1/TM. This cleavage was observed in SK-MEL-28 cells until 72 hours after infection with Ad-FKHRL1/TM. Our data suggest that adenovirus expressing a FKHRL1 triple mutant could be a useful vector for gene therapy of cancers resistant to chemotherapy and radiotherapy induced by hyperactivity of PI3K/Akt.
Asunto(s)
Apoptosis , Factores de Transcripción Forkhead/genética , Terapia Genética/métodos , Melanoma/terapia , Neoplasias Cutáneas/terapia , Adenoviridae/genética , Apoptosis/genética , Caspasas/metabolismo , Ciclo Celular/genética , Línea Celular Tumoral , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/metabolismo , Proteína Forkhead Box O3 , Factores de Transcripción Forkhead/metabolismo , Técnicas de Transferencia de Gen , Humanos , Melanoma/metabolismo , Melanoma/patología , Mutación , Fosforilación , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/patología , Transducción GenéticaRESUMEN
OBJECTIVE: To investigate the mechanism of tetra-arsenic tetra-sulfide (As4S4) in inducing apoptosis of acute promyelocytic leukemia (APL) cells. METHODS: The gene expression patterns in NB4 cells pre- and post-treatment with As4S4 were analyzed by cDNA microarray, and differentially expressed genes related with apoptosis were identified. The mRNA expression levels of these apoptosis related genes in the peripheral blood of APL patients treated with As4S4 pre- and post-remission were examined by RT-PCR. RESULTS: Among the differentially expressed genes in NB4 cells pre- and post-treatment with As4S4, two genes were related with cellular apoptosis, which were Apaf-1 and PNAS-2. Apaf1 ratio between pre- and post- As4S4 in NB4 cells was 2.910, PNAS-2 ratio was 0.420. RT-PCR results showed that the expression ratios of Apaf-1, caspase-9 and PNAS-2 in APL patients pre- and post-remission were 2.31 and 3.21, 0.99 respectively. CONCLUSION: As4S4 induced cellular apoptosis in NB4 cells involves the expression changes of the two genes: the up-regulation of Apaf1 and down-regulation of PNAS-2. The increased expressions of Apaf1 and caspase-9 indicate that As4S4 induced apoptosis in APL cells is through mitochondrial pathway, but not the death-receptor pathway. The role played by PNAS-2 in cellular apoptosis needs to be clarified.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Apoptosis/efectos de los fármacos , Factor Apoptótico 1 Activador de Proteasas/genética , Arsenicales/farmacología , Sulfuros/farmacología , Apoptosis/genética , Arsénico/farmacología , Línea Celular Tumoral , Expresión Génica/efectos de los fármacos , Perfilación de la Expresión Génica , Humanos , Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/patología , Análisis de Secuencia por Matrices de Oligonucleótidos , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Sulfuros/químicaRESUMEN
In order to study the role of PML-RARalpha fusion gene and its expression product during apoptotic process in NB4 cells induced by arsenic trisulfide (As(2)S(3)), the apoptotic effects of NB4 cells were observed by cell morphology, flow cytometry and DNA electrophoresis. The change of PML-RARalpha fusion gene and its expression product were also assayed by chromosomal G banding, RT-PCR and Western blot. The results showed that arsenic trisulfide induced apoptosis of NB4 cells, during this process, PML-RARalpha fusion gene had no significant changes, but the expression of PML-RARalpha fusion protein and wild-type RARalpha were all reduced. It is concluded that arsenic trisulfide can induce apoptosis of NB4 cells, the degradation of PML-RARalpha fusion protein and wild-type RARalpha may play an important role during apoptotic process.