Downregulation of Apurinic/Apyrimidinic Endonuclease 1/Redox Factor-1 Enhances the Sensitivity of Human Pancreatic Cancer Cells to Radiotherapy In Vitro

Background: Radiotherapy is an important treatment for the patients with advanced pancreatic cancer. Emerging studies determined apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) might associate with the resistance of human pancreatic cancer cells to radiotherapy. Aims: To investigate whether downregulation of APE1/Ref-1 expression by ribonucleic acid interference would increase the sensitivity of chromic-P32 phosphate to pancreatic cancer cells. Methods: The plasmids containing APE-specific and unspecific short hairpin were transfected into Patu-8898 cells. Stable cell clones were selected by G418. The mRNA expression of APE1/Ref-1 was detected by semi-quantitative reverse transcription-polymerase chain reaction and the protein expression of APE1/Ref-1 was detected by Western blot analysis; cell proliferation was studied by 3-(4, 5-dimethylthiazol-2-yl)-2, 5diphenyltetrazolium bromide (MTT) and colony formation assay; apoptosis was detected by flow cytometry. Results: After 24 hours irradiation, APE1/Ref-1 mRNA and protein expression were upregulated, in a concentration-dependent manner. Suppression of APE1/Ref-1 by siRNA increased the pancreatic cancer cells hypersensitive to P-32-CP. In the combination of P-32-CP and siRNA group, MTT assay showed that the cell inhibition increased to (74.33%+/- 9.02%), the surviving fraction in the colony formation assay was only 25.00%, and the apoptosis rate was up to (16.77%+/- 0.98%). Conclusions: Knockdown APE1/Ref-1 gene expression may significantly sensitize the Patu-8988 cells to radiotherapy, which may be a useful target for modifying radiation resistance of pancreatic cancer cells to irradiation.