Anti-apoptotic effects of protein kinase C-delta and c-fos in cisplatin-treated thyroid cells.
OBJECTIVE
We showed previously that cisplatin inititates a signalling pathway mediated by PKC-delta/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-delta/ERK.


METHODS
Cells were treated with various pharmacological inhibitors of PKCs and ERK, or were depleted of c-fos, PKC-delta, PKC-epsilon and caspase-3 by small interfering RNA (siRNA), then incubated with cisplatin and cytotoxicity assessed.


RESULTS
Cisplatin provokes the induction of c-fos and the activation of conventional PKC-beta, and novel PKC-delta and -epsilon. The cisplatin-provoked c-fos induction was decreased by Gö6976, a PKC-beta inhibitor; by siRNA for PKC-delta- but not that for PKC-epsilon 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-delta-siRNA plus Gö6976. When c-fos expression was blocked by siRNA, cisplatin cytotoxicity was strongly enhanced with increased caspase-3 activation. In PKC-delta-depleted cells treated with cisplatin, caspase-3 activation was increased and cell viability decreased. In these PKC-delta-depleted cells, PD98059 did not affect caspase-3 activation.


CONCLUSIONS
In PC Cl3 cells, in the cell signalling pathways that lead to cisplatin resistance, PKC-delta controls ERK activity and, together with PKC-beta, 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.
Muscella
Antonella
A
Department of Biological and Environmental Sciences and Technologies (Di.S.Te.B.A.), Università del Salento, Lecce, Italy.
Urso
Loredana
L
Calabriso
Nadia
N
Vetrugno
Carla
C
Rochira
Alessio
A
Storelli
Carlo
C
Marsigliante
Santo
S
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002454:Cell Differentiation; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology; D051745:Protein Kinase C-delta / Q000378:metabolism / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D051381:Rats; D013961:Thyroid Gland / Q000166:cytology*
D000970:Antineoplastic Agents; D007527:Isoenzymes; D016760:Proto-Oncogene Proteins c-fos; D051745:Protein Kinase C-delta; D002945:Cisplatin