Polyamine depletion inhibits etoposide-induced NF-kappaB activation in transformed mouse fibroblasts.
ABSTRACT In a previous research, we have shown that adequate levels of polyamines are required in transformed mouse fibroblasts for the correlated activations of MAPK subtypes (ERK and JNK) and caspases induced by etoposide and leading to apoptosis. We report now that the treatment of fibroblasts with etoposide also elicited a progressive and sustained increase of NF-kappaB activation. The DNA binding activity of p65 NF-kappaB subunit was increased up to approximately 4-fold and was accompanied by enhancement of p65 phosphorylation. A two days pre-treatment of fibroblasts with alpha-difluoromethylornithine (DFMO), which caused polyamine depletion, provoked a slight activating effect when given alone, but markedly inhibited the etoposide-induced increases in p65 DNA binding and phosphorylation. The NF-kappaB inhibiting effect of DFMO was prevented by the addition of exogenous putrescine, which restored the intracellular content of polyamines. Selective inhibitors of the etoposide-stimulated MAPK subtypes also reduced NF-kappaB activation. Moreover, pharmacological NF-kappaB inhibition reduced the increase in caspase activity and cell death elicited by etoposide, suggesting that NF-kappaB is involved in signaling to apoptosis. The results of the present study, together with our previous findings, suggest that polyamines play a permissive role in the pathways triggered by etoposide and leading to cell death of fibroblasts, by supporting the activation of MAPKs, NF-kappaB and caspases.
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ABSTRACT: The presence of polyamines is required for the apoptotic program triggered by 2-deoxy-D-ribose (dRib) in HL-60 cells, but their oxidative metabolites does not appear to be involved in the oxidative stress caused by the sugar. The present study points to a relationship between spermidine-induced G1 to S phase transition and the onset of dRib-induced apoptosis. Conversely, the G1 block induced by alpha-difluoromethylornithine (DFMO) is associated with a protective effect against dRib-induced cell suicide. Replenishment of the intracellular spermidine pool by exogenous putrescine and spermidine induces cell cycle progression and restores apoptotic levels. The present data indicate that the induction of cell cycle progression by spermidine is a condition facilitating the activation of the apoptotic process by dRib.Biochemical and Biophysical Research Communications 05/1999; 257(2):460-5. · 2.41 Impact Factor
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ABSTRACT: The natural polyamines -putrescine, spermidine, and spermine- are essential for cell growth and differentiation. Polyamines are involved in several gene regulatory functions, although their mechanism(s) of action has not been elucidated. We investigated the role of polyamines in the function of NF-kappa B and estrogen receptor-alpha (ER alpha), two transcription factors implicated in breast cancer cell proliferation and cell survival, using MCF-7 breast cancer cells. We found that spermine facilitated the binding of ER alpha and NF-kappa B to estrogen response element (ERE)- and NF-kappa B response element (NRE), respectively, and enhanced ER alpha-mediated transcriptional activation in transient transfection experiments. We also found that the association of the co-regulatory protein CBP/p300 with ER alpha and NF-kappa B was increased by spermine treatment of MCF-7 cells. Spermine also increased the nuclear translocation of NF-kappa B compared to the control. In contrast, treatment of MCF-7 cells with polyamine analogs, BE-3-4-3 and BE-3-3-3, resulted in transcriptional inhibition of both ERE- and NRE-driven reporter plasmids. In addition, polyamine analogs inhibited the association of ER alpha and NF-kappa B with CBP/p300 and were unable to facilitate nuclear translocation of NF-kappa B. APO-BRDU assay demonstrated that polyamine analogs induced apoptosis, with a loss of the anti-apoptotic protein Bcl-2. These data show a gene regulatory function of polyamines involving transcriptional activation of ER alpha and NF-kappa B, potentially leading to the up-regulation of genes involved in breast cancer cell proliferation. Our results with BE-3-4-3 and BE-3-3-3 suggest that down-regulation of ER alpha- and NF-kappa B-regulated genes is a possible mechanism for the action of polyamine analogs in inducing apoptosis of breast cancer cells.Oncogene 04/2001; 20(14):1715-29. · 7.36 Impact Factor