Targeting the short form of cFLIP by RNA interference is sufficient to enhance TRAIL sensitivity in PC3 prostate carcinoma cells

White, Shai J.; Lü, Ping; Keller, Gina M.; Voelkel‐Johnson, Christina

doi:10.4161/cbt.5.12.3352

Cited by 13 publications

(17 citation statements)

References 19 publications

(27 reference statements)

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“…The hydrogen peroxide dose curve indicates that at doses as low as 25 μM, the protein profile of doxorubicin treatment is recapitulated. This profile, as we have shown in previous work [13] and in Figure 3B, is characterized by a reduction in cFLIP S , preservation of cFLIP L and strong phosphorylation of EF-2. We therefore hypothesized that hydrogen peroxide could, like doxorubicin, sensitize PC3 cells to TRAIL.…”

Section: Free Radicals Can Phosphorylate Ef-2 and Reduce Cflip S Exprsupporting

confidence: 56%

“…For instance, we have recently shown that downregulation of cFLIP S was sufficient to sensitize PC3 cells to TRAIL [13]. Because these cells have such low levels of Bcl-2 and Mcl-1, cFLIP S may be the critical determinant of its apoptotic phenotype.…”

Section: Discussionmentioning

confidence: 99%

“…Our previous study indicated that a doxorubicin dose as low as 250 ng/ml could effectively downregulate cFLIP S but that the effect is not mediated by transcriptional control or by ubiquitination [13]. Therefore, we next investigated translational control.…”

Section: Doxorubicin Treatment Halts Protein Synthesismentioning

confidence: 99%

“…The regulation of cFLIP S by doxorubicin does not appear to be mediated at the levels of transcription or proteasomal degradation [13]. Therefore, in this study we examined the possibility of translational control of cFLIP S .…”

Section: Introductionmentioning

confidence: 99%

“…In addition, PC3 cells can be sensitized with simple downregulation of cFLIP S through siRNA, suggesting that the myriad other actions of doxorubicin may be superfluous to this sensitization process [13]. Identifying this key protein change, we wished to determine how doxorubicin was accomplishing the downregulation of cFLIP S .…”

Section: Introductionmentioning

confidence: 99%

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Doxorubicin generates a proapoptotic phenotype by phosphorylation of elongation factor 2

White

Kasman

Kelly

et al. 2007

Free Radical Biology and Medicine

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We have previously shown that doxorubicin sensitizes prostate cancer cells to TNF-Related Apoptosis Inducing Ligand (TRAIL). Sensitization correlated with decreased expression of the antiapoptotic protein cFLIP S . The decrease in cFLIP S could not be explained by transcriptional regulation or increased degradation, leading us to focus on translational mechanisms. In this study, we found that doxorubicin caused strong and sustained phosphorylation of elongation factor 2 (EF-2), which interferes with protein elongation. Phosphorylation of EF-2 appeared to occur in a kinaseindependent manner. Treatment with hydrogen peroxide recapitulated the events observed after doxorubicin treatment. In addition, cells treated with hydrogen peroxide expressed less XIAP and survivin which, like cFLIP S , are short half-life proteins with an anti-apoptotic function while expression levels of DR5, caspases-8, -9, -3, and Bax are maintained. The doxorubicin-mediated decrease in cFLIP S and XIAP as well as TRAIL-induced apoptosis was prevented by pretreatment with an iron chelator, indicating that expression of these proteins was affected by free radical generation upon interaction of iron with doxorubicin. In conclusion, our data suggest that free radicals can affect the phosphorylation of EF-2 resulting in a net loss of short half-life proteins such as cFLIP S and XIAP, leaving a cell more vulnerable to apoptotic stimuli.

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Section: Free Radicals Can Phosphorylate Ef-2 and Reduce Cflip S Exprsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Section: Doxorubicin Treatment Halts Protein Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Doxorubicin generates a proapoptotic phenotype by phosphorylation of elongation factor 2

White

Kasman

Kelly

et al. 2007

Free Radical Biology and Medicine

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A novel inhibitor of proteasome deubiquitinating activity renders tumor cells sensitive to TRAIL-mediated apoptosis by natural killer cells and T cells

Sarhan

Wennerberg

D’Arcy

et al. 2013

Cancer Immunol Immunother

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The proteasome inhibitor bortezomib simultaneously renders tumor cells sensitive to killing by natural killer (NK) cells and resistant to killing by tumor-specific T cells. Here, we show that b-AP15, a novel inhibitor of proteasome deubiquitinating activity, sensitizes tumors to both NK and T cell-mediated killing. Exposure to b-AP15 significantly increased the susceptibility of tumor cell lines of various origins to NK (p < 0.0002) and T cell (p = 0.02)-mediated cytotoxicity. Treatment with b-AP15 resulted in increased tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor-2 expression (p = 0.03) and decreased cFLIP expression in tumor cells in vitro. In tumor-bearing SCID/Beige mice, treatment with b-AP15 followed by infusion of either human NK cells or tumor-specific T cells resulted in a significantly delayed tumor progression compared with mice treated with NK cells (p = 0.006), T cells (p < 0.0001) or b-AP15 alone (p = 0.003). Combined infusion of NK and T cells in tumor-bearing BALB/c mice following treatment with b-AP15 resulted in a significantly prolonged long-term survival compared with mice treated with b-AP15 and NK or T cells (p ≤ 0.01). Our findings show that b-AP15-induced sensitization to TRAIL-mediated apoptosis could be used as a novel strategy to augment the anticancer effects of adoptively infused NK and T cells in patients with cancer.

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Caspase-8 and its inhibitors in RCCs in vivo: the prominent role of ARC

et al. 2008

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Activation of the initiator-caspase, caspase-8 is under tight control of multiple antiapoptotic regulators including ARC, cFlip(S), cFlip(L) and PED/PEA-15. Since there is little data regarding the expression of caspase-8 and its antiapoptotic regulators in human tumours in vivo, we analysed their expression in renal cell carcinomas (RCCs) to identify which of these genes might be crucial for the well known impaired apoptosis and--as a result--resistance towards chemotherapy and ionizing radiation of RCCs. Caspase-8, cFlip(S), cFlip(L) and PED/PEA-15 mRNA expression was significantly increased only in early stages of RCCs compared to non-neoplastic renal tissue. In contrast, ARC mRNA expression was significantly increased in RCCs of all stages without differences between the tumour stages and grades. Importantly, the relative mRNA expression ratio between ARC and caspase-8 was significantly increased during carcinogenesis and tumour progression. In contrast, the relative mRNA expression ratio between cFlip(S), cFlip(L) or PED/PEA-15 and caspase-8 remained constant during all tumour stages. In conclusion, our analysis revealed that ARC is the only caspase-8 inhibiting regulator being constantly overexpressed in RCCs. Furthermore, the balance between antiapoptotic ARC and proapoptotic caspase-8 is the only one to be disturbed during carcinogenesis and tumour progression of RCCs. This inhibition of Caspase-8 might therefore be one example for the multiple antiapoptotic functions of ARC in RCCs possibly contributing to the marked resistance of RCCs towards radio- and chemotherapy and reflects a shift of gene expression towards a more antiapoptotic context in RCCs.

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Targeting the short form of cFLIP by RNA interference is sufficient to enhance TRAIL sensitivity in PC3 prostate carcinoma cells

Cited by 13 publications

References 19 publications

Doxorubicin generates a proapoptotic phenotype by phosphorylation of elongation factor 2

Doxorubicin generates a proapoptotic phenotype by phosphorylation of elongation factor 2

A novel inhibitor of proteasome deubiquitinating activity renders tumor cells sensitive to TRAIL-mediated apoptosis by natural killer cells and T cells

Caspase-8 and its inhibitors in RCCs in vivo: the prominent role of ARC

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