Cytotoxic mechanisms of FK317, a new class of bioreductive agent with potent antitumor activity.
FK317 is a member of a new class of bioreductive agents that exhibit strong cytotoxicity against various human cancer cells. The effect of FK317 was found to be stronger than that of mitomycin C (MMC), adriamycin (ADR) or cisplatin (CDDP). Alkaline elution analysis indicated that FK317 formed interstrand DNA-DNA and DNA-protein cross-links in cells. On the other hand, no DNA single-strand breaks were observed in the cells treated with FK317. In a cell-free system the deacetylated metabolites produced cross-linked DNA under reductive conditions, though FK317 itself did not form DNA-DNA cross-links. In order to elucidate the metabolic activation mechanisms, we established an FK317-resistant subline from human non-small cell lung cancer cells (Lu99) by stepwise and brief exposure (1 h) to FK317. The resistant subline (Lu99/317) showed cross-resistance to MMC and carboquone (CQ), but not to ADR or CDDP. DT-diaphorase, which is one of the activation enzymes of MMC and CQ, was deficient in Lu99/317 cells as determined by enzyme activity assay. However, the levels of NADPH:cytochrome P450 reductase, which is another activation enzyme for MMC and CQ, were comparable in resistant and parent cell lines. Treatment of the cells with dicumarol, an inhibitor of DT-diaphorase, reduced the cytotoxicity of FK317 to Lu99 cells, but not to Lu99/317 cells. These results indicate that deacetylation of FK317 is necessary for its reductive activation, and deacetylated FK317 is reduced by DT-diaphorase to form an active metabolite, which produces DNA-DNA interstrand and DNA-protein cross-links that lead to cell death.
Department of Pharmacology, Pharmacological Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., Osaka.
Y
Y
Naoe
M
M
Inami
I
I
Kawamura
F
F
Nishigaki
S
S
Tsujimoto
S
S
Matsumoto
T
T
Manda
K
K
Shimomura
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004247:DNA / Q000187:drug effects; D001728:Dicumarol / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D006801:Humans; D007939:Leukemia L1210 / Q000378:metabolism; D010078:Oxazines / Q000737:chemistry / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D003432:Cross-Linking Reagents; D010078:Oxazines; D001728:Dicumarol; C112463:FK 317 dihydrobenzoxazine; D004247:DNA