title: Modulation of VP-16 cytotoxicity by carboplatin and 41.8 degrees C hyperthermia.
abstract: OBJECTIVE
  To study in vitro the effect of carboplatin and/or hyperthermia in relation to etoposide (VP-16) cytotoxicity in L929 cells.
  
  
  RESULTS
  Cell survival assays demonstrated that the addition of 41.8 degrees C (x60 min) hyperthermia and carboplatin to VP-16 produced an antagonistic effect relative to VP-16 cytotoxicity in L929 cells; administering carboplatin and hyperthermia 24 h before VP-16 reduced this drug resistance; administering carboplatin and hyperthermia 48 h before VP-16, however, produced a supra-additive cytotoxicity. In order to gain insight into the molecular basis for these observations, we investigated the effect of hyperthermia and/or carboplatin on the stress protein GRP78, which is known to affect VP-16 cytotoxicity. Results obtained were consistent with the hypothesis that carboplatin and hyperthermia perturbation of NAD + pools results in down-regulation of GRP78 with subsequent modulation of VP-16 cytotoxicity. To further explicate these results we studied G-361 as a control cell line that had significantly higher pretreatment NAD+ levels, which were not affected by carboplatin and/or hyperthermia. This cell line did not exhibit a down-regulation of GRP78 or modulation of VP-16 cytotoxicity as a function of carboplatin and hyperthermia.
  
  
  CONCLUSIONS
  These data taken collectively, demonstrate a sequence effect (regarding the aforementioned antineoplastic agents), and provide a framework for future studies directed at the therapeutic optimization of the sequential application of carboplatin, hyperthermia, and VP-16.
authors.affiliation: Department of Physiology, Medical University of Lübeck, Germany.
authors.forename: D M
authors.initials: DM
authors.lastname: Katschinski
authors.forename: E L
authors.initials: EL
authors.lastname: Jacobson
authors.forename: G J
authors.initials: GJ
authors.lastname: Wiedemann
authors.forename: H I
authors.initials: HI
authors.lastname: Robins
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000037:antagonists & inhibitors*; D015153:Blotting, Western; D016190:Carboplatin / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D000091342:Endoplasmic Reticulum Chaperone BiP; D005047:Etoposide / Q000037:antagonists & inhibitors*; D005354:Fibrosarcoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D006979:Hyperthermia, Induced; D051379:Mice; D009243:NAD / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717248:Hspa5 protein, mouse; D009243:NAD; D005047:Etoposide; D016190:Carboplatin