Enhanced proapoptotic effects of tumor necrosis factor-related apoptosis-inducing ligand on temozolomide-resistant glioma cells.
OBJECTIVE
Death receptor targeting is an attractive approach in experimental treatment for tumors such as malignant gliomas, which are resistant to radiation and chemotherapy. Among the family of cytokines referred to as death li gands, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has attracted clinical interest. The aim of this study was to assess whether TRAIL can be used as an adjuvant to temozolomide (TMZ) for apoptosis induction in malignant glioma cell lines.


METHODS
Six human malignant glioma cell lines (A172, U87, U251, T98, U343, and U373) were exposed to human (h)TRAIL, TMZ, or an hTRAIL/TMZ combined treatment. Cell viability was assayed using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide and phase-contrast microscopy. Cell apoptosis was detected using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling technique and quantified using flow cytometric analysis. The apoptosis signaling cascade was studied with Western blotting. The additive effects of hTRAIL and TMZ resulted in a significant decrease in cell viability and an increased apoptotic rate. Expression of the death receptors DR5 and DR4 in two cell lines (A172 and U251) upregulated significantly when they were used in combination hTRAIL/TMZ treatment (p < 0.05 compared with baseline control), leading to activation of caspase-8 and caspase-3 (p < 0.05 compared with baseline control) and confirming an extrinsic apoptotic pathway. A cell intrinsic pathway through mitochondrial cytochrome c was not activated.


CONCLUSIONS
Based on this work, one may infer that hTRAIL should be considered as an adjuvant treatment for TMZ-resistant human malignant gliomas.
Uzzaman
Mahmud
M
Department of Neurosurgery, Mount Sinai School of Medicine, New York, New York 10029, USA.
Keller
Gordon
G
Germano
Isabelle M
IM
D018906:Antineoplastic Agents, Alkylating / Q000008:administration & dosage*; D017209:Apoptosis / Q000187:drug effects*; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003606:Dacarbazine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D004359:Drug Therapy, Combination; D005910:Glioma / Q000188:drug therapy* / Q000473:pathology*; D006801:Humans; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000008:administration & dosage*; D000077204:Temozolomide
D018906:Antineoplastic Agents, Alkylating; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D003606:Dacarbazine; D000077204:Temozolomide