PNP expression and prodrug-drug conversion after bactofection with the eukaryotic expression plasmids encoding the converting enzymes (genes were under the control of P
) by COS-1, 4T1 and B16 cells. (a) Western blot analysis with anti-PNP antibodies performed with protein extracts of cells bactofected with WL-150 pSP118-PCMV-EGFP (A); WL-150 pSP118-PCMV-PNP (B) and WL-150 pSP118-P4xTETP-PNP (C) for 3 d or infected with WL-150 pSP0-P
actA-SP-PNP (D) for 4 h. Equal protein load was confirmed by Ponceau S-staining of the nitrocellulose membrane immediately after blotting. (b) Conversion of MePdR determined by HPLC-analysis in the supernatant of cell cultures 7 d after addition of 50 μM MePdR.