Abnormal Expression Of Gene S100A2 In Human Pancreatic Cancer Radioresistant Sublines

Background : Pancreatic cancer remains a common and lethal cancer with a median survival ofapproximately 6 months. Surgical resection of the primary tumour is only possible in about10% of cases as many patients have locally advanced or metastatic disease at the time ofpresentation.Only 20% of the patients are candidates for curative resection at diagnosis. For themajority of patients,treatment outcomes continue to be poor, joint treatment is important,including surgical treatments or chemotherapy, radiotherapy or interventional radiologicaltechniques. Radiation therapy is one of the important adjuvant treatments. However, clinicaltrials showed that radiotherapy response varies individually, and there were clinical reports ofradiation resistance. Our study planned to investigate different expression and significance ofgenes between parental pancreatic cancer cell lines and radioresistant sublines, to predict theclinical effectiveness of radiotherapy and to use it in intervention of radioresistant pancreaticcancer. We have successfully established radioresistant human pancreatic cancer celllines( radioresistant subline , SW1990—R). Using oligonucleotide microarrays , we haveidentified up-regulated genes and down-regulated genes to radioresistant sublines,in whichgene S100A2 were down-regulated..In this study, we determine to relate changes in the geneS100A2 expression to radio biological responses of pancreatic cancer cell lines.OBJECTIVE: The purpose of this study was to discover whether S100A2 expression changesis associated with second radioresistanc of pancreatic cell line.METHODS:①Test S100A2 mRNA and S100A2 protein in human pancreatic cell line(SW1990 and radioresistant subline, SW1990-R).②Radioresistant subline SW1990-Rcells were treated with 0.1, 1.0, 6.25, 12.5,25 and 50μmol/L 5-Aza-2'-deoxycytidinerespectively. The expression of the gene S100A2 mRNA and S100A2 protein was detected byreverse transcription polymerase chain reaction (RT-PCR) and fluorescence quantitativeanalysis . The cell cycle were analyzed by flow cytometry.The growth of the cells wasobserved by a cloning efficiency assay (Radioresistant subline SW1990-R were treated with 0.1, 1.0, 6.25, 12.5,25 and 50μmol/L 5-Aza-2'-deoxycytidine respectively ,then were exposed to0,1,2,3,5,7,and 10 Gy x-ray radiation , then cultured for 2 weeks.) .③Transfect gene S100A2to radioresistant subline SW1990-R cells, and then test gene S100A2 expression , cell cycleand radio biological responses of gene S100A2 trasfected cells.④Knock out gene S100A2 inparental SW1990 cells , and then test gene S100A2 expression , cell cycle and radio biologicalresponses of gene S100A2 kocked out cells.RESULTS:①Expression of S100A2 in radioresistant subline SW1990-R is lower than inparental cell line.②5-Aza-2'-deoxycytidine increased expression of S100A2 in radioresistantpancreatic cell line .Expression of S100A2 is associated with G2 phase of cells, S100A2increased in cells at G2 phase. Cloning efficiency assays showed that survival rate ofradioresistant cell line was lower by Rexpression S100A2.③S100A2 expression wasupregulated in transfected gene S100A2 radioresistant subline SW1990. Expression of S100A2is associated with G2 phase of cells, S100A2 upregulation in cells at G2 phase (P＜0.05).Cloning efficiency assays showed that survival rate of radioresistant subline SW1990-R waslower by Rexpression S100A2 (P＜0.05).④S100A2 expression was downregulated in geneS100A2 kocked out parental SW1990 cell line, which reduced the proportion of knocked-outgene cells at G2 phase (P＜0.05). Cloning efficiency assays showed that survival rate ofknocked-out gene cells was higher by downregulating the expression of gene S100A2 (P＜0.05).CONCLUSION:①Expression of S100A2 in radioresistant subline SW1990-is lower than in parentalline SW1990.②5-Aza-2'-deoxycytidine may reexpress gene S100A2 in radioresistant sublineSW1990-R, which diminished the radioresistance of radioresistant subline SW1990-R.③Expression of S100A2 is associated with G2 phase of cells, which affects the radio biologicalresponses of pancreatic cancer cell line.④Don't exclude that S100A2 affects the radiobiological responses of pancreatic cancer cell line through other mechanisms.