Protein phosphatase 2A inhibitors activate extrinsic apoptosis in pancreatic cancer cells through nuclear factor-κB dependent pathway

Abstract

Objective To investigate the apoptosis induction effect of protein phosphatase 2A (PP2A) inhibitors on human pancreatic cancer cell line (PANC-1).Methods Activity of nuclear factor-κB (NF-κB) pathway was tested by using luciferase reporter gene assay.Activities of Caspase 8 and 9 were determined by kits.The expression levels of genes downstream of the NF-κB pathway were tested by using reverse transcription-polymerase chain reaction (RT-PCR).Results Treatment with PP2A inhibitors,cantharidin and Okadaic acid,up-regulated the transcriptional activity of NF-κB by the folds of 10.11 ± 4.09,and 16.21 ± 5.75 respectively.Pretreatment with the NF-κB pathway inhibitor,Bay 11-7082,repressed the up-regulation of NF-κB transcriptional activity by (61.19 ±6.08)％ and (62.09 ± 12.38)％ respectively.Treatment with cantharidin or Okadaic acid activated extrinsic apoptosis pathway,and up-regulated the activity of Caspase 8 by the folds of 0.55 ±0.12,and 0.85 ±0.21 respectively.Pretreatment with Bay 11-7082 repressed the up-regulation of Caspase 8 activity by (20.99 ±7.13)％ and (29.07 ±7.98)％ respectively.Treatment with cantharidin or Okadaic acid also activated intrinsic apoptosis pathway,and up-regulated the activity of Caspase 9 by the folds of 1.35 ±0.20,and 1.18 ±0.19 respectively.However,pretreatment with Bay 11-7082 presented no significant effect on the up-regulation of Caspase 9 activity.Treatment with cantharidin or Okadaic acid up-regulated the expression of pro-apoptotic genes which could be repressed by the pretreatment with Bay 11-7082.Conclusion PP2A inhibitors triggered extrinsic apoptosis and up-regulated the expressions of pro-apoptotic genes in pancreatic cancer cells through NF-κB dependent pathway. Key words: Pancreatic cancer; Protein phosphatase 2A; Cantharidin; Nuclear factor-κB