Cyclopentenyl cytosine and neuroblastoma SK-N-BE(2)-C cell line cells.

We studied the effect of cyclopentenyl cytosine (CPEC) on human neuroblastoma SK-N-BE(2)-C cell line cells. CPEC had an IC50 value of 100 nM for non-synchronised SK-N-BE(2)-C cells. These cells were arrested in G0/G1-phase or early S-phase of the cell cycle upon treatment with CPEC. After treatment of synchronised S-phase cells with 1 microM CPEC, the number of cells present after 3 days was less than 10% of that observed for the untreated cells. S-phase synchronised cells treated with CPEC and deoxycytidine showed an increased viability in comparison with cells treated with CPEC alone. Approximately 15% of the cells treated with CPEC and deoxycytidine traversed through one cell cycle. The amount of CTP declined to undetectable levels within 3 h after addition of 1 microM CPEC. The presence of cytidine prevented, to a large extent, the cytostatic effect of CPEC.