PP2A Inhibitors Repress Migration And Growth Of PANC-1Pancreatic Cancer Cells Through Inhibition Of The Wnt/β-catenin Pathway

Objective:Cantharidin is an active constituent of a traditional Chinese medicine, mylabris.Cantharidin is a potent and selective inhibitor of serine/threonine protein phosphatase2A(PP2A). PP2A is a multimeric serine/threonine phosphatase which can dephosphorylatemultiple kinases. It is thought to be a cancer suppresser, as inhibition of PP2A can inducephosphorylation and activation of substrate kinases, most of which can further accelerategrowth. Interestingly, previous reports have found that PP2A inhibitors, Cantharidin andOkadaic acid (OA), inhibited pancreatic cancer cell growth, but the effect on migration isstill unclear, the mechanisms involved in the anticancer effect of PP2A inhibitors have notbeen fully explored. The Wnt/-catenin pathway is involved in cell migration andproliferation, and participates in the progression of pancreatic cancer. If-catenin isphosphorylated and degraded, the Wnt/-catenin pathway is blocked. PP2Adephosphorylates-catenin and keeps the Wnt/-catenin pathway active. As activation ofWnt/-catenin pathway can trigger migration and proliferation in some circumstance, wetried to investigate whether PP2A inhibitors could repress migration in pancreatic cancercells through activation phosphorylation and degradation of-catenin.Methods:1．PANC-1pancreatic cancer cells were divided into four groups.2．Migration of PANC-1cells treatment with PP2A inhibitors was investigated usingwound-healing assay.3．Inhibition of Wnt/-catenin pathway by PP2A inhibitors was measured using Western blot.4． Migration and proliferation of PANC-1cells treatment with Wnt/-cateninpathway inhibitor were investigated by wound-healing assay and MTT.5. Microarray analyses and real-time PCR were performed to determine the mRNAexpression changes of138genes downstream of Wnt/-catenin pathway.Results:1. Cantharidin could repress PANC-1cells migration.2. PP2A inhibitors treatment induced phosphorylation and degradation of-catenin,which further resulted in the decreased nuclear translocation.3. The repression on the migration and growth of PANC-1pancreatic cancer cellscould be attenuated by pretreatment with FH535, a Wnt/-catenin pathway inhibitor.4. Microarray showed that PP2A inhibitors treatment induced expression changes ofgenes downstream of Wnt/-catenin pathway.5. RT-PCR further confirmed that FH535attenuated the expression changes inducedby PP2A inhibitors in6genes. All these6genes, VEGFB, DKK3, KRT8, NRP1, Cacnalgand WISP2, have been proved to participate in the migration and/or growth regulation inprevious studies.Conclusion:The degradation of-catenin and inhibition of Wnt/-catenin signal pathwayparticipate in the cytotoxicity of PP2A inhibitors. Our findings may shed lights on thetreatment of pancreatic cancer using a targeting PP2A strategy.