Background and purpose: We showed previously that cisplatin inititates a signalling pathway mediated by PKC-δ/extracellular signal-regulated kinase (ERK), important for maintaining viability in PC Cl3 thyroid cells. The studies described herein examined whether c-fos was associated with cisplatin resistance and the signalling link between c-fos and PKC-δ/ERK. Experimental approach: Cells were treated with various pharmacological inhibitors of PKCs and ERK, or were depleted of c-fos, PKC-δ, PKC-η and caspase-3 by small interfering RNA (siRNA), then incubated with cisplatin and cytotoxicity assessed. Key results: Cisplatin provokes the induction of c-fos and the activation of conventional PKC-β, and novel PKC-δ and -η. The cisplatin-provoked c-fos induction was decreased by Gö6976, a PKC-β inhibitor; by siRNA for PKC-δ- but not that for PKC-η or by PD98059, a mitogen-activated protein kinase/ERK kinase inhibitor. Expression of c-fos was abolished by GF109203X, an inhibitor of all PKC isoforms, or by PD98059 plus Gö6976 or by PKC-δ-siRNA plus Gö6976. When c-fos expression was blocked by siRNA, cisplatin cytotoxicity was strongly enhanced with increased caspase-3 activation. In PKC-δ-depleted cells treated with cisplatin, caspase-3 activation was increased and cell viability decreased. In these PKC-δ-depleted cells, PD98059 did not affect caspase-3 activation. Conclusions and implications: In PC Cl3 cells, in the cell signalling pathways that lead to cisplatin resistance, PKC-δ controls ERK activity and, together with PKC-β, also the induction of c-fos. Hence, the protective role of c-fos in thyroid cells has the potential to provide new opportunities for therapeutic intervention. © 2009 The British Pharmacological Society.
Anti-apoptotic effects of protein kinase C-δ and c-fos in cisplatin-treated thyroid cells
Urso L.;
2009
Abstract
Background and purpose: We showed previously that cisplatin inititates a signalling pathway mediated by PKC-δ/extracellular signal-regulated kinase (ERK), important for maintaining viability in PC Cl3 thyroid cells. The studies described herein examined whether c-fos was associated with cisplatin resistance and the signalling link between c-fos and PKC-δ/ERK. Experimental approach: Cells were treated with various pharmacological inhibitors of PKCs and ERK, or were depleted of c-fos, PKC-δ, PKC-η and caspase-3 by small interfering RNA (siRNA), then incubated with cisplatin and cytotoxicity assessed. Key results: Cisplatin provokes the induction of c-fos and the activation of conventional PKC-β, and novel PKC-δ and -η. The cisplatin-provoked c-fos induction was decreased by Gö6976, a PKC-β inhibitor; by siRNA for PKC-δ- but not that for PKC-η or by PD98059, a mitogen-activated protein kinase/ERK kinase inhibitor. Expression of c-fos was abolished by GF109203X, an inhibitor of all PKC isoforms, or by PD98059 plus Gö6976 or by PKC-δ-siRNA plus Gö6976. When c-fos expression was blocked by siRNA, cisplatin cytotoxicity was strongly enhanced with increased caspase-3 activation. In PKC-δ-depleted cells treated with cisplatin, caspase-3 activation was increased and cell viability decreased. In these PKC-δ-depleted cells, PD98059 did not affect caspase-3 activation. Conclusions and implications: In PC Cl3 cells, in the cell signalling pathways that lead to cisplatin resistance, PKC-δ controls ERK activity and, together with PKC-β, also the induction of c-fos. Hence, the protective role of c-fos in thyroid cells has the potential to provide new opportunities for therapeutic intervention. © 2009 The British Pharmacological Society.
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