Fig. 2

ILz:rhTRAIL showed the highest cell death inducing ability in the combination treatment of recombinant TRAIL and bortezomib. Cells were cultured onto 96-well plates with 80% to 90% of confluency. Cell death rates were analyzed by XTT assay 24 h after the indicated treatment. The relative values of the XTT assay were examined following comparison to untreated controls. (a) Each cell was treated with 100 ng/ml of recombinant TRAIL protein and a distinctive amount of bortezomib as indicated: rmT, recombinant mouse TRAIL from Peprotech (rmTRAIL); rhT, recombinant human TRAIL from Peprotech (rhTRAIL); ILz:T, isoleucine zipper hexamerization motif containing recombinant human TRAIL (ILz:rhTRAIL). (b) Two TRAIL-resistant cell lines (B16F10 and CT26) were treated with fixed amounts of bortezomib (50 and 100 nM) and serially increasing amounts of ILz:rhTRAIL. (c) Two TRAIL-sensitive cell lines (HEK 293 and MDA-MB-231) were treated with fixed amounts of bortezomib (25 and 50 nM) and serially increasing amounts of ILz:rhTRAIL: bort, bortezomib. * and **p < 0.05 and p < 0.1 by Student’s t-test, respectively