(-)-Epigallocatechin 3-gallate inhibits invasion by inducing the expression of Raf kinase inhibitor protein in AsPC-1 human pancreatic adenocarcinoma cells through the modulation of histone deacetylase activity

The aim of the present study was to assess whether (-)-epigallocatechin 3-gallate (EGCG) via epigenetic modifications, regulates Raf kinase inhibitor protein (RKIP) expression and invasive metastatic activity in AsPC-1 pancreatic adenocarcinoma cells. Basal levels of RKIP were examined in various human pancreatic cancer cell lines and MTT assay was used to assess cell viability. AsPC-1 cells were treated with EGCG with/without trichostatin A (TSA), as the positive control, for 24 h. The levels of RKIP and histone H3 induction were analyzed by immunoblot analysis. In order to determine the role of RKIP induction in NF-kappa B translocation and invasive metastatic activity in AsPC-1 cells, we examined NF-kappa B translocation, invasive metastatic parameters by RT-PCR, metastasis-related proteins by western blot analysis and matrix metalloproteinase (MMP)-2 and -9 activity by gelatin zymography. To validate RKIP induction through the extracellular signal regulated kinase (ERK) pathway, the cells were treated with U0126, an ERK inhibitor. Our results showed that EGCG induced RKIP upregulation via the inhibition of histone cleacetylase (HDAC) activity which increased histone H3 expression and inhibited Snail expression, NF-kappa B nuclear translocation, MMP-2 and -9 activity and Matrigel invasion in AsPC-1 cells. The expression of E-cadherin in the cells was upregulated. The phosphorylation of ERK was decreased by RKIP induction following EGCG treatment. Furthermore, our results confirmed that U0126 treatment repressed ERK phosphorylation and induced RKIP expression. Taken together, our results strongly suggest that EGCG regulates RKIP/ERK/NF-kappa B and/or RKIP/NF-kappa B/Snail and inhibits invasive metastasis in the AsPC-1 human pancreatic adenocarcinoma cell line.