Treatment based on a combination of the CYP2B1/cyclophosphamide system and p53 delivery enhances tumour regression in human pancreatic cancer

Background: Strategies based on the introduction of pro-drug activating enzymes or the restoration of tumour suppressor genes have been proposed as encouraging methods to improve the efficiency of treatments in pancreatic cancer. The in situ bioactivation of cyclophosphamide by cytochrome p450-2B1 and subsequent p53 delivery were examined. Materials and methods: NP-18 cell line derived from a human pancreatic adenocarcinoma was treated in vitro with a combination of the Adenovirus-CYP2B1/cyclophosphamide and adenoviral-mediated wt-p53 reintroduction. Cell viability and cytometric cell cycle profiles were analyzed to evaluate the sensitivity of NP-18 cells to this treatment. The efficiency of this combination was assessed in an in vivomodel consisting of xenografts into the subcutaneous tissue of Balb/c mice by tumour growth, histological analysis and cell cycle determinations. Results: Ad-CYP2B1/cyclophosphamide or Ad-p53treatments led to a marked decrease in cell viability of NP-18 cells. Combination of both treatments elicited a higher loss of cell viability and marked increases in sub-G1 population in cell cycle profiles. Animals treated with the combination strategy showed a quick reduction of tumour volumes due to the bioactivation of cyclophosphamide by CYP2B1 and sustained growth inhibition throughout the period evaluated after p53 delivery. Only this group of animals presented statistically significant differences with respect to control and cyclophosphamide-treated groups (P < 0.05). Conclusions: These results indicate that in situbioactivation of cyclophosphamide by CYP2B1 and the recognition of the damaged DNA by p53 increase tumour regressions and may be a promising therapy for solid tumour therapy in man.