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Introduction: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is currently under development as a chemotherapeutic agent because it induces apoptosis in many cancer cells but spares normal cells. However this approach faces the obstacle that some cancer cells are resistant to TRAIL. In this study, we investigated genomic alternations contributing to the TRAIL resistance in human glioblastoma cells. Methods: Molecular cytogenetic approaches were undertaken to decipher the genome of human glioblastoma cell lines with varying degrees of sensitivity to TRAIL. A combination of comparative genomic hybridization (CGH), G-banding/spectral karyotyping (SKY) and fluorescence in situ hybridization (FISH) analyses with chromosomal region specific probes was used to identify aberration of chromosomal regions that harbor key TRAIL signaling gene DR4/DR5, caspase-8, capsase-3, caspase-7, caspase-9, Bid, Bax, Bak, Bcl-2 and Smac. Results: A large number of twenty-six glioblastoma cell lines were screened for their sensitivity to TRAIL and eight (2 sensitive, 3 partially resistant and 3 resistant) of the cell lines were examined for their genomic alternations. Loss or structural aberration of chromosome regions harboring DR4/DR5, caspase-8, and Smac genes was simultaneously observed in all three TRAIL resistant cell lines. Two out of the three resistant cell lines also showed a loss involving Bid locus. Lose of above gene loci was not observed simultaneously among the TRAIL sensitive cell lines. The aberrations involving those loci were observed in partial resistant cell lines but much less frequently than the resistant cell lines. Protein expression of these genes was significantly downregulated in the resistant cell lines. Examination of TRAIL-induced extrinsic and intrinsic pathways revealed cleavage of caspase-8, caspase-3, caspase-9, and DNA fragmentation factor 45 in the sensitive but not in the resistant cell lines. Conclusions: The multiple simultaneous genomic alterations in DR4/DR5, caspase-8, Bid and Smac loci contribute to TRAIL resistance in human glioblastoma cell lines. This study not only sheds some light on the genomic mechanisms in glioblastomas cell resistance to TRAIL-induced apoptosis but also identifies genetic markers that could be used to predict the responsiveness of glioblastomas to TRAIL therapy in clinical trials.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]