SYNTHESIS AND CELLULAR UPTAKE OF 2'-SUBSTITUTED ANALOGS OF (E)-5-(2-[I-125]IODOVINYL)-2'-DEOXYURIDINE IN TUMOR-CELLS TRANSDUCED WITH THE HERPES-SIMPLEX TYPE-1 THYMIDINE KINASE GENE - EVALUATION AS PROBES FOR MONITORING GENE-THERAPY

A useful synthetic methodology was developed to synthesize and radiola bel a series of (E)-5-(2-[I-125]iodovinyl)uracil nucleoside substrates for herpes simplex virus type-1 thymidine kinase (HSV-1 TK). (E)-5-(2 -[I-125]Iodovinyl)-2'-deoxyuridine ([I-125]IVDU, 10), )-5-(2-[I-125]io dovinyl)-2'-fluoro-2'-deoxyuridine ([I-125]IVFRU, 11), [I-125]iodoviny l)-2'-fluoro-2'-deoxyarabinouridine ([I-125]IVFAU, 12), and (E)-5-(2-[ I-125]iodovinyl)arabinouridine ([I-125]IVAU, 13) were synthesized in 6 3-83% radiochemical yield by reaction of the unprotected (E)-5-(2-(tri methylsilyl)vinyl) precursors (6-9) with [I-125]ICl. Cellular uptake o f these labeled compounds (10-13) was evaluated in vitro. All compound s showed minimal uptake in the KBALB cell line. However, increased upt ake was observed for all compounds in KBALB-STK cells which are transd uced with a replication incompetent Moloney murine leukemia virus vect or encoding the HSV-1 TK gene. The results indicate that uptake of the se compounds in KBALB-STK cells is variable and highly dependent on th e nature of the sugar 2'-substituent. When a fluoro (12) or a hydroxy (13) substituent is present in the arabinofuranosyl (up) configuration at the 2'-position, there is diminished cellular uptake in KBALB-STK cells relative to hydrogen (10) or fluorine (11) in the ribofuranosyl (down) configuration at the 2'-position. Our results indicate that rad iolabeled IVFRU (11) is most promising for further in vivo studies.