Infuence of cDNA-expressed cytochrome P450 isoforms on anticancer activity of some new diesters of zidovudine

P Ruszkowski1, H Laskowska1, L Celewicz2, T Bobkiewicz-Kozlowska1, B Hladon1. 1Poznan University of Medical Sciences, Department of Pharmacology, Poland, 2Adam Mickiewicz University, Faculty of Chemistry, Poland

Some of nucleoside analogues play an important role in anticancer and antiviral pharmacotherapy. Zidovudine (AZT), although originally designed as an antitumor agent, is so far widely used as antiviral inhibitor of HIV-1 reverse transcriptase, that acts as a DNA chain terminator. It is postulated that the mechanism of action of zidovudine may be associated with its conversion to zidovudine-triphosphate , followed by its incorporation by DNA host polymerases. Phosphoramidate pronucleotides seems to be effective for the intracellular delivery of nucleoside 5’-monophosphates (MP) as regards to their in vitro anticancer activity showed in human tumor cell models. A series of twenty nine newly synthesized: 5’-(4-chloropfenyl)-and 5’-(2-chlorophenyl)- phosphoramidate diesters (1D – 29D) desired as the potentially pro-nucleotides were studied against HeLa, KB, MCF-7 and Hep-G2 human tumor cells in tissue culture systems, based on the DR and D, NCI, NIH Bethesda programs. Four mostly active compounds: 4D, 11D, 18D and 23D were qualified for in vitro investigation using a mixture of insect cell-expressed human drug metabolizing cytochrome P450 isoforms (CYPs: 1A2,2C8,2C9,2C19,2D6 and 3A4) model as to be related to their activities in human liver microsomes. That mixture system has been proposed as an experimental model comparable to human liver microsomes for drug biotransformation studies. The results performed with cDNA-expressed cytochrome P450 isoforms showed considerable increase of anticancer activity in vitro against MCF-7 tumor cells for compounds: 4D and 11D with their IC50 of 0.06 and 0.11 μg/cm3 respectively, in comparison with non-activated control samples. It is proposed that the influence of drug metabolizing CYP450 isoforms plays important role both in chemical reduction of phoshoramidate diesters of zidovudine with formation to high reactive intermediate of 3’-amino-derivatives metabolites and enhance their in vitro anticancer activity.