Regulation of endoplasmic reticulum chaperone glucose regulated protein 78 by methyl-CpG binding domain protein 1 affects pancreatic cancer invasion and metastasis

Objective To investigate the role of methyl-CpG binding domain protein 1 ( MBD1 ) and glucose regulated protein 78 ( GRP78 ) in the invasion and metastasis of pancreatic cancer and their interaction.Methods After treatment of pancreatic cancer cell line BxPC-3 with thapsigargin (Tg),quantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting were used to detect the expresion of GRP78 mRNA and protein.By using wound healing test,the changes in migration were evaluated.By using RNA interference technique,the MBD1-siRNA plasmid was transfected into BxPC-3 cells,quantitative RT-PCR and Western blotting were used to analyze MBD1 and GRP78 mRNA and protein expression after transfection,and Transwell invasion assay was used to measure cell migration.Immunohistochemically,the expression of MBD1 and GRP78 proteins was detected in 40 cases of pancreatic cancer and 15 cases of normal pancreatic tissue.Results After Tg treatment of BxPC-3 cells (Tg/BxPC-3),GRP78 mRNA and protein expression was significantly increased,and the number of migratory BxPC-3 was also increased.After MBD1-siRNA plasmid was transfected into Tg/BxPC-3,MBD1 and GRP78 mRNA and protein expression was simultaneously decreased,while the invasion ability of BxPC-3 diminished.The positive rate of MBD1 and GRP78 was 70.0％ ( 28 ) and 67.5％ (26) respectively out of 40 cases of pancreatic cancer specimens,significantly higher than that of the normal pancreatic tissue (P ＜0.05).There was a positive correlation between MBD1 and GRP78 protein expression ( r =0.594,P ＜0.01 ),and both MBD1 and GRP78 expression was associated with lymph node metastasis ( P ＜ 0.05 ).Conclusion Endoplasmic reticulum molecular chaperone GRP78 may act as an important target of MBD1 via methylation,which may have an impact on the characteristics of pancreatic cancer invasion and metastasis.The regulation of GRP78 expression by MBD1 may change the nature of pancreatic cancer invasion and metastasis,and improve the prognosis of pancreatic cancer. Key words: Pancreatic carcinoma; Endoplasmic reticulum stress; Glucose regulated protein