01) higher CK-18 fragment levels (8.69- ± 0.75-fold increase; Fig. 8C). Similarly, treatment with nontargeted scTRAIL and BZB induced a significantly (P < 0.01) higher cell-death rate (6.98- ± 1.00-fold increase, compared to untreated control), compared to EGFR-targeted scTRAIL combined with bortezomib (2.91- ± 0.28-fold increase; Fig. 8D). Thus, in combination with BZB, EGFR-targeted scTRAIL showed only marginal toxic effects on inflamed liver tissues, in Ivacaftor cell line contrast to nontargeted scTRAIL, which strongly induced toxicity in inflamed liver tissues. Although first clinical trials using TRAIL for the treatment

of various advanced cancers showed promising results, including stable disease, it becomes evident that TRAIL monotherapy most likely will not result in http://www.selleckchem.com/products/Deforolimus.html a sufficient response, especially in solid tumor entities.10 Under certain conditions, TRAIL treatment of solid tumors even increased tumor cell migration and metastatic spread.33,34 In such conditions, TRAIL might activate prosurvival pathways, such as the nuclear factor kappa B (NF-κB) or MAPK pathways, rather than induce apoptosis. Thus, restoring TRAIL sensitivity toward apoptosis by the combined treatment of TRAIL with TRAIL-sensitizing agents

is required to increase not only the clinical benefit, but, possibly, also to prevent cancer patients from harming effects of TRAIL in apoptosis-resistant tumors. In HCC high levels of various antiapoptotic

regulators of the death receptor and mitochondrial pathways, including cellular FLICE inhibitory protein (c-FLIP), X-linked inhibitor of apoptosis protein (XIAP), and several Bcl-2 proteins, have been observed.35,36 Proteasome inhibitors, such as BZB, have been recently shown to sensitize tumor cells, including HCC cells, toward TRAIL-induced apoptosis.23,24 These agents might be superior to other TRAIL-synergizing drugs, because inhibition of the proteasome as the central regulator of protein turnover affects multiple pathways and thus increases the likelihood that various TRAIL-resistance mechanisms can be bypassed.37 BZB treatment MCE of hepatoma cells resulted in TRAIL-R1/2 up-regulation, enhanced death-inducing signaling complex formation, and down-regulation of c-FLIP and XIAP.24 BZB not only influences the extrinsic, but also the intrinsic pathway by triggering the release of proapoptotic mitochondrial factors.24,38 In addition, proteasome inhibitors trigger cell-cycle arrest and NF-κB inhibition, thereby influencing apoptosis induction.39 In view of the various targets of proteasome inhibitors that have been identified, it must be noted that it was not our intention to further investigate the mechanisms of BZB-mediated TRAIL sensitization. Targeting of TRAIL to the tumor site represents an additional therapeutic strategy to increase antitumoral efficacy and avoid systemic toxicity.