title: Concentration and sequence dependent synergism of ethyldeshydroxy-sparsomycin in combination with antitumor agents.
abstract: The modulating effect of ethyldeshydroxy-sparsomycin (EDSM), an inhibitor of ribosomal protein synthesis, on cytostatic agents was studied on cultured B16 melanoma cells using the microculture tetrazolium test (MTT). The data were analyzed for true synergism using the combination index and the median effect principle. The extent of cytotoxic drug interaction was influenced by the duration of drug exposure, the dose ratio, as well as the treatment schedule. When drug ratios were used, synergism was observed upon pre- and post-treatment in combination with cisplatin, cytosine arabinoside (Ara-C), methotrexate (MTX) and 5-fluorouracil (5-FU). The combination of a fixed dose of EDSM was synergistic with cisplatin, Ara-C, vincristine (VCR) and MTX, in the order MTX > Ara-C > VCR > cisplatin, while the combinations with doxorubicin, 5-FU and etoposide (VP-16) were shown to be antagonistic. These results suggest that only certain drugs and treatment schedules might be worthwhile for combination studies with EDSM in vivo and indicate a role for EDSM as modifier of antitumor responses in cancer chemotherapy.
authors.affiliation: Department of Internal Medicine, Nijmegen University Hospital, The Netherlands.
authors.forename: H P
authors.initials: HP
authors.lastname: Hofs
authors.forename: D J
authors.initials: DJ
authors.lastname: Wagener
authors.forename: V
authors.initials: V
authors.lastname: de Valk-Bakker
authors.forename: H
authors.initials: H
authors.lastname: van Rennes
authors.forename: H C
authors.initials: HC
authors.lastname: Ottenheijm
authors.forename: W J
authors.initials: WJ
authors.lastname: de Grip
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004396:Coloring Agents; D004336:Drug Antagonism; D004357:Drug Synergism; D008546:Melanoma, Experimental / Q000188:drug therapy / Q000503:physiopathology; D051379:Mice; D013033:Sparsomycin / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013778:Tetrazolium Salts; D013844:Thiazoles; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004396:Coloring Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; C074101:ethyldeshydroxysparsomycin; D013033:Sparsomycin; C022616:thiazolyl blue