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

Abstract

Pancreatic cancer is one of the most common tumors and has a 5-year survival for all stages of less than 5%. Most patients with pancreatic cancer are diagnosed at an advanced stage and therefore are not candidates for surgical resection. In recent years, investigation into alternative treatment strategies for this aggressive disease has led to advances in the field of gene therapy for pancreatic cancer. E. coli purine nucleoside phosphorylase/6-methylpurine deoxyribose (ePNP/MePdR) is a suicide gene/prodrug system where PNP enzyme cleaves nontoxic MePdR into cytotoxic membrane-permeable compounds 6-methylpurine (MeP) with high bystander activity. hTERT is expressed in cell lines and tissues for telomerase activity. In this study we examined the efficacy of ePNP under the control of hTERT promoter sequences and assessed the selective killing effects of the ePNP/prodrug MePdR system on pancreatic tumors. 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 luciferase reporter gene. A recombinant phTERT-ePNP vector was constructed. The ePNP/MePdR system affects SW1990 human pancreatic cancer cell lines in vitro. The hTERT promoter had high transcriptional activity and conferred specificity on cancer cell lines. The antibody to E. coli PNPase was demonstrated to be specific for the ePNP protein. The MePdR treatment induced a high in vitro cytotoxicity on the sole hTERT-ePNP-producing cell lines and affected SW1990 cells in a dose-dependent manner. The hTERT promoter control of the ePNP/MePdR system can provide a beneficial anti-tumor treatment in pancreatic cancer cell lines including a good bystander killing effect.