DINALINE INHIBITS AMINO-ACID-TRANSPORT AND PROLIFERATION OF COLON-CARCINOMA CELLS IN-VITRO

The human colon carcinoma cell line SW707 was incubated with different concentrations (7 mu M - 540 mu M) of the novel antineoplastic drug 4 -amino-N(2'-aminophenyl)benzamide (GOE1734, dinaline) to study the eff ects on H-3-alpha-aminoisobutyric acid (AIB) - and C-14-methionine upt ake as well as on H-3-thymidine incorporation into DNA. Additionally, adenine nucleotide pools were determined by high performance liquid ch romatography (h.p.l.c.), and cell cycle distribution by flow cytometry . 24 h exposure to low concentrations of dinaline caused mild cell pro liferation which turned into a cytostatic effect within a fil, ther 24 h without drug exposure. High concentrations of dinaline, however, we re found to be cytostatic and then cytotoxic after corresponding time intervals. Dinaline caused a concentration-dependent decrease in sodiu m-dependent AIB uptake. Immediately after exposure the effect ranged f rom 67% - 36% of control uptake. One day later an incomplete recovery not exceeding 70% of control was found for the three highest concentra tions. This differed significantly from sodium-dependent methionine up take which was initially decreased by 24% - 36% but recovered within o ne hour and was enhanced one day after exposure. Significant differenc es were also measured for sodium-independent AIB uptake and sodium-ind ependent methionine uptake immediately, 1 and 4 h after exposure. Aden ine nucleotide pools were mildly increased immediately and 4 h after e xposure. Thymidine incorporation into DNA was decreased by 70% to 84% immediately after exposure, and no full recovery was seen in the subse quent observation period Cell cycle analyses revealed a block at the S phase entrance. Changes in thymidine incorporation and S phase fracti on were highly correlated. The inhibition of the sodium-dependent upta ke of AIB might indicate interaction of dinaline with cell membrane fu nctions at low concentrations, the increase in methionine uptake point s to enhanced protein synthesis following drug withdrawal and the impa ired thymidine incorporation into DNA results from the cytostatic effe ct of dinaline. Taken together, the results show that SW707 colon carc inoma cells exposed to dinaline demonstrate distinct but reversible ch anges in amino acid transport, protein metabolism DNA synthesis and ce ll proliferation, thus giving a con elation with observations in vivo.