ObjectiveTo investigate the effects of protein phosphatase 2A (PP2A) inhibitors on the viability of pancreatic cancer cell line PANC-1 and its mechanism.MethodsPANC-1 cells were treated with PP2A inhibitors Cantharidin or Okadiac acid.The activity degree of NF-κB pathway was tested by Western blot.NF-κB pathway was blocked from all sectors by PP2Acα plamid transfection,NF-κB inhibition of protein kinase α (IKKα) and NF-κB inhibitor α (IκBα) dominant negative mutant and p65 interfering plasmid.Cell viability was determined by MTT.ResultsPP2A inhibitors could induce phosphorylation of IKKα,further phosphorylation of IκBα and degradation and followed by the release of p65 into nucleus.When PP2Acα,IKKα dominant negative mutant and IκBα dominant negative mutant were overexpressed,or p65 was interfered,the inhibition rate of Cantharidin on cell viability decreased (31.85±13.37) ％,(23.48±8.98)％,(22.63±5.81)％ and (20.88±3.24)％respectively,and the inhibition rate of Okadiac acid on cell viability decreased (40.17 ± 11.65)％,(27.34±14.28)％,(24.85±3.39)％ and (27.08±3.81)％ respectively.ConclusionsPP2Ainhibitors play a role in preventing pancreatic cancer through PP2Acα/IKKα/IκBα/p65 pathway.

Objective To investigate the effects of AFP enhancer/pgk promoter driven expression of the dominant negative form of the PP2A catalytic subunit α (DN-PP2Acα) in vivo.Methods The previously constructed AFpg promoter-driven DN-PP2Acα was recombined into an adenovirus,and the expression of PP2Ac was tested using Western blot.Cell growth was tested using the MTT and flat plate clone formation assays.In vivo studies were performed in tumor xenograft models.Results AFpg promoter-driven expression of DN-PP2Acα exerted cytotoxic effects against the AFP-positive human hepatoma cell line HepG2,but did not affect AFP-negative human hepatoma cells (SKHEP-1) or normal human liver cells (L-02).Moreover,AFP enhancer/pgk promoter driven expression of DN-PP2Acα inhibited the growth of AFP-positive HepG2 tumors in nude mice bearing solid tumor xenografts,but did not affect AFP-negative SK-HEP-1 tumors.Conclusion The recombinant AFP enhancer/pgk promoter-driven DN-PP2Acα expression adenovirus presented selective cytotoxicity against AFP-positive hepatoma cells and provides a useful gene therapy strategy to selectively target hepatocellular carcinoma.

Objective To investigate the apoptosis induction effect of Cantharidin on pancreatic cancer cell line PANC1 and CFPAC-1 and possible mechanism. Methods PANC1 and CFPAC-1 was treated with Cantharidin. Cell growth was determined by MTT. Apoptosis was measured by flow cytometry. Caspase activity was measured by using enzyme chemical method. Apoptosis-related gene expressions were determined by using RT-PCR and Western blotting. Results Cantharidin significantly inhibited the growth of pancreatic cancer cells PANC1, CFPAC-1 and induced apoptosis in a dose-dependent manner. Seventy-two hours after 10 μmol/L Cantharidin treatment, the inhibitory rates of PANC1, CFPAC-1 were (52.95 ± 6.34)％ and (71.21 ±6.30)％. Twenty-four hours after treatment, the early and later period apoptotic cell of PANC1 was increased from 7.35％ to 24.89％, from 6.36％ to 17.73％. The early and later period apoptotic cell of CFPAC was increased from 6.39％ to 24.70％, from 9.21％ to 12.58％ (P＜0.01). Activity of caspase 8 and caspase 9 in PANC1 cells was (155.8 + 11.5)％ and (194.6 ± 14.7)％ when compared with that of control group. Activity of caspase 8 and caspase 9 in CFPAC- 1 was ( 182.5 ± 24.3 ) ％ and ( 215.8 ± 12.2) ％when compared with that of control group ( P ＜ 0. 01 ). The expression of pro-apoptotic genes, TNF-α,TRAILR1, TRAILR2, Bad, Bak and Bid was elevated, the expression of anti-apoptotic Bcl-2 gene was decreased. Conclusions Cantharidin can induce apoptosis in pancreatic cancer cell lines by activating caspase,up-regulating the expression of pro-apoptotic genes and down-regulating the expression of anti-apoptotic genes.