Adaphostin cytoxicity in glioblastoma cells is ROS-dependent and is accompanied by upregulation of heme oxygenase-1.
OBJECTIVE
To delineate a role for reactive oxygen species (ROS) induction in adaphostin-induced apoptosis in glioblastoma cells.


METHODS
Three glioblastoma cell lines with different sensitivities to adaphostin were characterized for sensitivity to an oxidant, tert-butyl hydroperoxide. The degree and duration of the ROS levels was assessed in the three cell lines after adaphostin exposure. Antioxidant protein levels were evaluated by Western blotting.


RESULTS
Of the three glioblastoma cell lines, the U87 cells were least sensitive to adaphostin. These cells were also least sensitive to tert-butyl hydroperoxide, indicating that sensitivity to a direct oxidant stress mirrors the cells' adaphostin sensitivities. In addition, the antioxidant N-acetylcysteine, (NAC) was protective against adaphostin-induced apoptosis. Direct measurement of intracellular peroxides showed a transient increase in the two less sensitive cell lines (U87 and LN18) which diminishes by 24 h. In contrast, U251 cells, which are most sensitive to adaphostin, display a sustained increase in the ROS levels. After the initial increase in intracellular peroxides, the heat shock protein and antioxidant heme oxygenase-1 (HO-1) was upregulated. Levels of other antioxidant proteins, such as catalase and thioredoxin, however, were not altered by adaphostin in glioblastoma cell lines. NAC attenuated HO-1 upregulation, confirming the time course analysis.


CONCLUSIONS
These results suggest a primary role for ROS in adaphostin-induced apoptosis in glioblastoma. Our data indicate that the duration of intracellular ROS levels is a key factor in mediating sensitivity to adaphostin. Furthermore, upregulation of HO-1 is a novel molecular marker of adaphostin's action. The kinetics with which adaphostin upregulates HO-1 correlates with sensitivity to the drug. Taken together, our data indicate that a cell's ability to cope with ROS dictates sensitivity to adaphostin and conceivably other chemotherapies that cause redox perturbations.
Long
Jason
J
Department of Pediatrics Research, Division of Pediatrics, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., 853, Houston, TX 77030, USA.
Manchandia
Tejas
T
Ban
Kechen
K
Gao
Shan
S
Miller
Claudia
C
Chandra
Joya
J
D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D053938:DNA Fragmentation / Q000187:drug effects; D016044:Fusion Proteins, bcr-abl / Q000037:antagonists & inhibitors; D005909:Glioblastoma / Q000188:drug therapy* / Q000378:metabolism; D005978:Glutathione / Q000032:analysis; D051547:Heme Oxygenase-1 / Q000235:genetics*; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation
D000970:Antineoplastic Agents; D006873:Hydroquinones; C404397:NSC 680410; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D051547:Heme Oxygenase-1; D016044:Fusion Proteins, bcr-abl; D005978:Glutathione; D000218:Adamantane