Combined antitumor effect of cyclophosphamide and bromodeoxyuridine in BDF1 mice bearing L1210 ascites tumors.

We investigated the combined effect of cyclophosphamide (CPA) and 5-bromo-2'-deoxyuridine (BrdUrd) both in mice bearing L1210 ascites tumors and in L1210 leukemic cells in vitro. Administration of BrdUrd (100 mg/kg) for 5 consecutive days before a single dose (80 mg/kg) of CPA significantly extended the survival of mice by 158%, compared with CPA alone. BrdUrd administered at daily doses of 100 or 200 mg/kg for 5 consecutive days did not extended the survival of mice. An in vitro MTT assay revealed that BrdUrd enhanced the cytotoxic effect of 4-hydroxycyclophosphamide, an active form of CPA, in the L1210 cells. These results indicate that BrdUrd enhanced the antitumor effect of CPA both in vivo and in vitro.