Prometastatic overexpression of microtubule destabilizing protein Stathmin is regulated by DNA methylation in human pancreatic cancer

Abstract

Objective To investigate the role of Stathmin in pancreatic cancer invasion and metastasis and its relationship with DNA methylation. Methods Immunohistochemical detection of MBDI and Stathmin protein expression in 40 cases of pancreatic cancer and 15 cases ot normal pancreatic tissue were performed,followed by analysis of their clinical and pathological relationship with pancreatic cancer; Human pancreatic cancer cell line BxPC-3 was treated with 5-Aza-2-dC (AZA).Both qRT-PCR and Western blot analysis of Stathmin expression were used before and after AZA treatment; Stathmin-siRNA transfected BxPC-3 cells were divided into the Stathmi-siRNA group and the empty vector control group.Transwell chamber invasion assay and animal experiment were performed to measure the changes in cell invasion and metastatic capability. Results lmmunohistochemistry showed positive MBDI and Stathmin expressions in 28 (70％) and 24 (60％) out of 40 cases of pancreatic cancer,respectively,which were significantly higher than that in the normal pancreatic tissue (P＜ 0.05); MBDI and Stathmin protein expressions were positively correlated (r =0.356,P =0.037),so were MBDI expression and lymph node metastasis (P=0.023).Stathmin expression was significantly correlated with clinical staging and lymph node metastasis (P =0.002,and P =0.001,respectively).After AZA treatment,both Stathmin mRNA and protein expression in BxPC-3 were significantly decreased.Transwell chamber invasion assay showed that compared with the control group,the cell invasion capability of the Stathmin-siRNA group was significantly decreased (P＜0.05).Animal experiment showed that the incidence of liver metastasis was significantly lower in the Stathmin-siRNA transfected group than the empty vector control group (P＜0.05).Conclusion Demethylation may contribute to the reduction of Stathmin expression in pancreatic cancer and further improve the prognosis of pancreatic cancer patients. Key words: Pancreatic neoplasms; DNA methylation; Neoplasm metastasis; Microtubule proteins