hTERT-targeted E.coli purine nucleoside phosphorylase gene/ 6-methylpurine deoxyribose therapy for pancreatic cancer

Background Pancreatic cancer is one of the most common tumors and has a 5-year survival for all stages of less than5%.Most patients with pancreatic cancer are diagnosed at an advanced stage and therefore are not candidates forsurgical resection.In recent years,investigation into alternative treatment strategies for this aggressive disease has ledto advances in the field of gene therapy for pancreatic cancer.E.coli purine nucleoside phosphorylase/6-methylpurinedeoxyribose(ePNP/MePdR)is a suicide gene/prodrug system where PNP enzyme cleaves nontoxic MePdR intocytotoxic membrane-permeable compounds 6-methylpurine(MeP)with high bystander activity,hTERT is expressed incell lines and tissues for telomerase activity.In this study we examined the efficacy of ePNP under the control of hTERTpromoter sequences and assessed the selective killing effects of the ePNP/prodrug MePdR system on pancreatictumors.Methods Recombinant pET-PNP was established.The protein of E.coli PNPase was expressed and an antibody to E.coli PNPase was prepared.Transcriptional activities of hTERT promoter sequences were analyzed using a luciferasereporter gene.A recombinant phTERT-ePNP vector was constructed.The ePNP/MePdR system affects SW1990 humanpancreatic cancer cell lines in vitro.Results The hTERT promoter had high transcriptional activity and conferred specificity on cancer cell lines.Theantibody to E.coli PNPase was demonstrated to be specific for the ePNP protein.The MePdR treatment induced a highin vitro cytotoxicity on the sole hTERT-ePNP-producing cell lines and affected SW1990 cells in a dose-dependentmanner.Conclusions The hTERT promoter control of the ePNP/MePdR system can provide a beneficial anti-tumor treatment inpancreatic cancer cell lines including a good bystander killing effect.