title: Characterization of a human bladder cancer cell line selected for resistance to BMY 25067, a novel analogue of mitomycin C.
abstract: This study describes characteristics of a human bladder cancer cell line, SCaBER/R, selected for resistance to a mitomycin C (MMC) analogue BMY 25067. The SCaBER/R cell line was isolated by repeated 24 h exposures of the parental cells to 0.09 microM BMY 25067 (IC90, 24 h drug exposure) over a period of about 180 days. Approximately 2.2-fold higher concentration of BMY 25067 was required to kill 50% of the SCaBER/R cell line compared with parental cells (p < 0.001). The IC20 and IC90 values for BMY 25067 were also significantly higher in the SCaBER/R cell line than in SCaBER. Unlike most MMC resistant cell lines, the SCaBER/R cell line displayed a marked cross-resistance to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and lacked cross-resistance to cisplatin, doxorubicin or VP-16. The SCaBER/R cell line also displayed a marked cross-resistance to the parent drug (MMC) and BMY 25282, another analogue of MMC. NADPH cytochrome P450 reductase activity, an enzyme implicated in bio-reductive activation of MMC, did not differ significantly in these cells. DT-diaphorase activity, another MMC activation enzyme, was significantly lower in the SCaBER/R cell line when compared to the SCaBER cells. These results suggest that relatively lower sensitivity of SCaBER/R cell line to MMC and BMY 25067 may result from impaired drug activation. Cellular levels of glutathione (GSH) and GSH-transferase (GST), which have been suggested to affect the cytotoxicity of MMC, were comparable in SCaBER and SCaBER/R cell lines. BMY 25067 induced DNA interstrand cross-links (DNA-ISC) could not be detected in either of the cell lines even at drug concentrations which produced a significant cell kill. These findings suggest that (a) cellular resistance to BMY 25067 in the SCaBER/R cell line may be due to impaired drug activation, and (b) the nature of the cytotoxic produced by BMY 25067 may be different from that of MMC.
authors.affiliation: Cancer Research Laboratory, Mercy Cancer Institute, Mercy Hospital of Pittsburgh, PA 15219, USA.
authors.forename: S V
authors.initials: SV
authors.lastname: Singh
authors.forename: B H
authors.initials: BH
authors.lastname: Xu
authors.forename: V
authors.initials: V
authors.lastname: Gupta
authors.forename: E O
authors.initials: EO
authors.lastname: Emerson
authors.forename: H A
authors.initials: HA
authors.lastname: Zaren
authors.forename: J P
authors.initials: JP
authors.lastname: Jani
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D002453:Cell Cycle; D004351:Drug Resistance; D005978:Glutathione / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D016685:Mitomycin / Q000494:pharmacology*; D008937:Mitomycins; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000473:pathology*
chemical_list: D000970:Antineoplastic Agents; D008937:Mitomycins; D016685:Mitomycin; C055172:N-7-(2-(nitrophenyldithio)ethyl)mitomycin C; D009251:NADPH-Ferrihemoprotein Reductase; D016660:NAD(P)H Dehydrogenase (Quinone); D005982:Glutathione Transferase; D005978:Glutathione