Modulation of Alkylating Agents by Etanidazole and Fluosol-DA/Carbogen in the FSalIC Fibrosarcoma and EMT6 Mammary Carcinoma

Tumor cell survival assay in the 1Sal K murine fibrosarcoma demon strated that when the modulator Fluosol-DA (0.3 ml; 12 ml/kg i.v.) was administered just prior to an alkylating agent plus carbogen breathing for 6 h or the modulator etanidazole (1 g/kg i.p.) was administered just prior to an alkylating agent, the combination treatment produced signif icantly more tumor cell killing across the dosage range of each alkylating agent tested compared with the alkylating agent alone. Each alkylating agent produced a dose-dependent log-linear tumor cell survival curve. There was an increase in tumor cell killing of 5-10-fold when either Fluosol-DA/carbogen or etanidazole was added to treatment with the alkylating agent. For c/ã- diamminedichloroplatinum(II) (CDDP) and jV,/V',Ar”-triethylenethiophosphoramide, the modulators used in combi nation increased tumor cell killing by only 2-3-fold over that obtained with a single modulator, but for the other alkylating agents, tumor cell killing was increased by 10-50-fold when the combination of modulators was used. Bone marrow granulocyte-macrophage colony-forming unit survival assays showed that the combination of modulators with the alkylating agents resulted in only small increases in bone marrow toxicity of the alkylating agents except for Ar,/V',Ai-triethylenethiophosphoramide and i.-phenylalanine mustard (L-PAM), for which the toxicity to the bone marrow granulocyte-macrophage colony-forming unit was in creased by 5-10-fold compared with the alkylating agents alone. The Hoechst 33342 dye diffusion defined tumor cell subpopulation assay, also in the FSalIC tumor, demonstrated that the combination of modulators increased the toxicity of CDDP, cyclophosphamide, L-PAM, and 1,3- bis(2-chloroethyl)-l-nitrosourea by 9-55-fold compared with the alkyl ating agent alone in both the bright (euxoic-enriched) and dim (hypoxicenriched) cells. For each alkylating agent except l,3-bis(2-chloroethyl)- l-nitrosourea, the increase in tumor cell killing was greater in the dim cells than in the bright cells. Finally, tumor growth delay studies in both the FSalIC tumor and the EMT-6 murine mammary adenocarcinoma confirmed that the combination of modulators significantly in creased the tumor growth delay caused by CDDP, carboplatin, cyclo phosphamide, A'.yV'./V-triethylenethiophosphoramide, L-PAM, and l,3-bis(2-chloroethyl)-l-nitrosourea. The greatest increases (4-5-fold) were observed for carboplatin and L-PAM in the FSalIC tumor and CDDP and cyclophosphamide in the EMT-6 tumor. These results suggest that Fluosol-DA/carbogen together with etanidazole may be an effective modulator combination of alkylating agents in the clinic.