Combination treatment based on metabolic effects of dinaline

The human colon carcinoma cell line SW 707 was exposed for up to 72 h to the new antineoplastic agent 4-amino-N-(2'-aminophenyl)benzamide (GOE 1734, dinaline). Thereafter, uptake measurements with fluorodeoxy-[14C]glucose (FdGlc) were performed and cell-cycle fractions as well as adenine nucleotide pools were determined by flow cytometry and HPLC. One day after a 24 h exposure to 20-540 microM dinaline a 2.0-to 2.5-fold enhancement of FdGlc uptake was observed, and the values after 48-h or 72-h incubations showed a 2.5- to 3.5-fold or a 2.0-fold increase respectively. For all periods of exposure a diminished S phase (3%-71% of control) was found initially after incubation, demonstrating the antiproliferative effect of dinaline, with total recovery after 1 day. Adenine nucleotide pools were not diminished concomitantly. The enhanced FdGlc uptake caused by dinaline was the basis for choosing 2-deoxyglucose (dGlc) as the combination partner, which acts as an antimetabolite to enzymes involved in glucose metabolism. Several combinations of dinaline and dGlc were analyzed for their effects on growth inhibition. Almost 50% additional decrease in cell number as compared to monotherapy with dinaline was found after coexposure to 12 mM dGlc and 20 microM dinaline 24 h after incubation. Similar effects were observed 2 days after incubation with the two drugs. After 3 days, the cell numbers reached monotherapy levels. Since the cytostatic effect of dinaline could be enhanced by dGlc although incubation with dGlc alone caused no changes in cell number, the combined effect of both agents is synergistic. These results imply that dinaline might have applications in combination treatment in vivo.