Abstracts
2000 Digestive Disease Week

# 2291 Gene Therapy with HSV-Tk of Pancreatic Cancer Cell Lines: Different Responses to GCV Treatment.
Eliana Greco, Paola Fogar, Daniela Basso, Annalisa Stefani, Claudio Pasquali, Mario Plebani, Sergio Pedrazzoli, Padova, Italy

Aim of this study was to ascertain whether the transfection of the pancreatic cancer cell lines Mia PaCa 2 and CAPAN-1 with the HSV enzyme thymidine kinase (Tk) increases the death rate after ganciclovir (GCV) treatment. The vector used in our study, named IL2-IRES-TK SN, carries a neo selectable marker gene, human interleukin 2 gene, an IRES coding site and the region coding HSV-Tk. Transduced cells were established by selection with the neomycin analogue geneticin (G418). After two weeks of treatment with G418 at the dosages of 0.5 and 1.5 mg/mL, only transduced CAPAN-1 (Tk+ CAPAN-1) and MIA PaCa 2 (Tk+ MIA PaCa 2) cells survived respectively. GCV was administered to Tk+ and Tk- Mia PaCa 2 and CAPAN- 1 cells at the dosages of 0.001, 0.01, 0.1, 1, 10, 20, 100, 200 and 500 mm. The cells, plated in 96 plated wells, were cultured for up to 11 days. Cell growth was assessed by means of the XTT assay. GCV treatment did not modified Tk- MIA PaCa 2 or CAPAN-1 cell growth when used at the dosage of 20 mm or less, while 200 mm or more completely inhibited cell growth. GCV treatment significantly inhibited the growth of Tk+ MIA PaCa 2 cells when used at the dosages of 1, 10 and 20 mm for 6 (t=3.35, p<0.05; t=4.01, p<0.05 and t=5.56, p<0.01) and 11 (t=7.44, p<0.01; t=4.85, p<0.01 and t=4.22, p<0.05) days. GCV treatment significantly inhibited the growth of Tk+ CAPAN-1 cells when used at the dosages of 0.001, 0.01, 1, 10 and 20 mm for 6 (t=3.74, p<0.05; t=6.46, p<0.01; t=2.66, p<0.05; t=9.69, p<0.01 and t=12.84, p<0.001) and 11 (t=3.91, p<0.05; t=3.93, p<0.05; t=28.52, p<0.001; t=7.58, p<0.01 and t=11.52, p<0.001) days. The growth of Tk+ MIA PaCa 2 cells after GCV treatment at 20 mm was not completely inhibited (Abs450nm=1.46±0.17, mean±SD) after 11 days of treatment in comparison with results from day 1 (0.44±0.03); TK+ CAPAN-1 cell growth after GCV treatment at 10 mm was completely inhibited after 11 days (0.37±0.003, mean±SD) in comparison with results from day 1 (0.41±0.01). Conclusion: the transfected metastatic pancreatic cancer cell line CAPAN- 1 was highly sensitive to GCV treatment at low dosages, while the cell line MIA PaCa 2 was only slightly sensitive to higher GCV dosages. These data indicate that gene therapy with suicide genes in pancreatic cancer needs to be carefully evaluated before any application in clinical practice.