Adenovirus-mediated wild-type p53 tumor suppressor gene therapy induces apoptosis and suppresses growth of human pancreatic cancer

Background: The p53 tumor suppressor gene is mutated in up to 70% of pancre atic adenocarcinomas. We determined the effect of reintroduction of the wil d-type p53 gene on proliferation and apoptosis in human pancreatic cancer c ells using an adenoviral vector containing the wild-type p53 tumor suppress or gene. Methods: Transduction efficiencies of six p53-mutant pancreatic cancer cell lines (AsPC-1, BxPC-3, Capan-1, CFPAC-1, MIA PaCa-2, and PANC-1) were dete rmined using the reporter gene construct AdS/CMV/beta-gal. Cell proliferati on was monitored using a H-3-thymidine incorporation assay. Western blot an alysis for p53 expression was performed, and DNA laddering and fluorescence -activated cell sorter analysis were used to assess apoptosis. p53 gene the rapy was tested in vivo in a subcutaneous tumor model. Results: The cell lines varied in transduction efficiency. The MIA PaCa-2 c ells had the highest transduction efficiency, with 65% of pancreatic tumor cells staining positive for beta-galactosidase (beta-gal) at a multiplicity of infection (MOI) of 50. At the same MOI, only 15% of the CFPAC-1 cells e xpressed the beta-gal gene. Adenovirus-mediated p53 gene transfer suppresse d growth of all human pancreatic cancer cell lines in a dose-dependent mann er. Western blot analysis confirmed the presence of the p53 protein product at 48 hours after infection. DNA ladders demonstrated increased chromatin degradation, and fluorescence-activated cell sorter analysis demonstrated a four-fold increase in apoptotic cells at 48 and 72 hours following infecti on with Ad5/CMV/p53 in the MIA PaCa-2 and PANC-1 cells. Suppression of tumo r growth mediated by induction of apoptosis was observed in vivo in an esta blished nude mouse subcutaneous tumor model following intratumoral injectio ns of Ad5/CMV/p53. Conclusions: Introduction of the wild-type p53 gene using an adenoviral vec tor in pancreatic cancer with p53 mutations induces apoptosis and inhibits cell growth. These data provide preliminary support for adenoviral mediated p53 tumor suppressor gene therapy of human pancreatic cancer.