1-4-6-8-tetramethyl-2h-furo(2-3-h)quinolin-2-one and Carcinoma--Ehrlich-Tumor

1,4,6,8-Tetramethyl-2H-furo[2,3h]quinolin-2-one (FQ) belongs to a series of furocoumarin isosters, designed to obtain new drugs for photochemotherapy. The objective of this study was to characterize the disposition of orally administered 3H-FQ in normal and ascitic tumor bearing mice and to evaluate the influence of UVA irradiation in control mice. This compound was rapidly absorbed and its decay in serum was biphasic. Binding to serum proteins, which was maximum at 30 min (74 %), time-dependently declined. FQ was distributed to all the studied tissues, primarily to the liver and kidneys. The administered radioactivity was excreted mostly in the urine (43 %) and was associated with polar metabolites. The unchanged compound was not present to any detectable extent in the urine. Elimination in the faeces, that may include FQ not absorbed, was low (14 % of administered radioactivity), emphasizing the quantitatively efficient gastrointestinal absorption of the drug. UVA irradiation of FQ-treated mice for 2 h caused a significant increase in radioactivity measured in serum as well as in the liver. In mice bearing Ehrlich ascitic tumor, serum and tissue concentrations were lower than in control animals, possibly due to the larger volume of body fluids (10+/-4 ml of ascitic fluid) available for drug distribution.

Topics: Animals; Antineoplastic Agents; Area Under Curve; Blood Proteins; Carcinoma, Ehrlich Tumor; Feces; Female; Intestinal Absorption; Kinetics; Mice; Quinolones; Tissue Distribution; Ultraviolet Rays

1,4,6,8-tetramethyl-2H-furo[2,3-h]quinolin-2-one (FQ) is a new isoster of angelicin characterised by an extremely strong photosensitizing activity, which is several times higher than that of 8-MOP and 4,6,4'-trimethylangelicin (TMA). Following treatment with 1.2 microM FQ and a dose as low as 0.05 kJ m(-2) of UVA irradiation, survival (colony forming ability) of HeLa cells was abolished, while TMA and 8-MOP (even at five times the concentration for the latter) were practically ineffective. Upon UVA irradiation FQ induces various types of lesions in mammalian cells in DNA: single-strand breaks (SSBs), many monoadducts and covalent DNA-protein cross-links (DPC), but not interstrand cross-links (ISC). Using the two step irradiation procedure, DPC induced by FQ appeared to be severe lesions, having a high antiproliferative activity; their formation requires the successive absorption of two photons, thus, in this respect, resembling ISC formation. In spite of its higher capacity for damaging DNA, FQ showed a skin-phototoxicity potency very similar to 8-MOP. As some benzopsoralens, FQ induced a certain antiproliferative activity also in the dark, which was accompanied by the formation of double-strand breaks into DNA associated with DPC. This lesion is generally induced by topoisomerase inhibitors. On the basis of these features, FQ can be expected to show useful activities in photochemotherapy and photopheresis. However, before medical use careful studies on its genotoxicity are required.

Topics: Animals; Carcinoma, Ehrlich Tumor; Cell Division; Cross-Linking Reagents; DNA; DNA Damage; Furocoumarins; Guinea Pigs; HeLa Cells; HL-60 Cells; Humans; Methoxsalen; Photochemistry; Photosensitizing Agents; Quinolones; Spectrophotometry; Ultraviolet Rays