TRAIL (APO-2L) induces apoptosis in human prostate cancer cells that is inhibitable by Bcl-2

The Relationship Between Inflammatory Processes and Apoptosis in Lumbar Disc Degeneration

OBJECTIVE

Degenerative Disc Disease (DDD) is a common health problem in the population. There are recent studies focusing on relationship between DDD and immunological factors. However, there is still a lack of data on the role of apoptosis in DDD pathophysiology. Therefore, we aimed to investigate the relationship between Modic-type changes and the apoptosis in DDD.

MATERIALS AND METHODS

Ninety adult male patients who presented with low back and/or radicular pain and were operated on due to lumbar disc herniation were included. Three groups were formed based on Modic type degeneration observed on magnetic resonance imaging. Specific parameters involved in the intrinsic and extrinsic pathways of apoptosis were assessed in excised disc materials using the enzyme-linked immunosorbent assay method.

RESULTS

All three groups formed according to Modic degeneration types were homogenous in all variances. Cytochrome-C was significantly decreased only in the Modic type-3 group, whereas Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Receptor-1, B-Cell Lymphoma-2 (Bcl-2) Homologous Antagonist Killer-1, Direct Inhibitor of Apoptosis-Binding Protein with Low Pi, and Bcl-2 Associated X Apoptosis Regulator levels were significantly different in both Modic type-2 and -3 groups. However, BH3 interacting domain death agonist and Bcl-2 levels were similar across all groups.

CONCLUSIONS

In conclusion, this study suggests that Direct Inhibitor of Apoptosis-Binding Protein with Low Pi, cytochrome - c, Bcl-2 Associated X Apoptosis Regulator, Bcl-2 Homologous Antagonist Killer-1, and Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Receptor-1proteins play important roles in the development and progression of DDD and are correlated with Modic types. Further studies are needed to explore the potential therapeutic role of inhibiting these apoptotic proteins in DDD.

Effect of the mycotoxin deoxynivalenol in combinational therapy with TRAIL on prostate cancer cells

Tumor necrosis factor-related apoptosis-induced ligand (TRAIL) is reported as a promising anti-cancer therapeutic target. Unfortunately, prostate cancer cells (PCa) are partially resistant to TRAIL-induced apoptosis limiting its therapeutic potential. The existing body of knowledge suggests that naturally produced compounds, such as mycotoxin deoxynivalenol (DON), might potentially sensitize cells to TRAIL treatment and improve the efficiency of therapy. Previously, we observed that DON induces oxidative stress and apoptosis in PCa cell lines. Thus we addressed here whether DON can sensitize PCa cells to TRAIL-induced apoptosis. Our data demonstrates that three out of four tested PCa cell lines pretreated with DON increased TRAIL-induced apoptosis detected with flow cytometry. This effect was associated with oxidative stress (LNCaP and DU-145 cell line) and elevated DNA damage (DU-145, LNCaP, and 22Rv1 cell lines). Next, in the animal model we inoculated PC tumor to SCKID mice followed by administration of DON intraperitoneally and/or TRIAL intravenously. During 21 days monitoring of tumor growth, the animals received 7 doses of DON, TRAIL, DON+TRAIL or control injections. No significant reduction in tumor mass was observed after combinational treatment of TRAIL and DON compared to 1 μg/kg of body weight DON treatment alone, which itself decreased the tumor growth. However, despite the lack of the TRAIL + DON effect, DON itself inducing apoptosis is an interesting compound worth investigating in the context of other combination therapies.

Harnessing TRAIL-induced cell death for cancer therapy: a long walk with thrilling discoveries

Tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) can induce apoptosis in a wide variety of cancer cells, both in vitro and in vivo, importantly without killing any essential normal cells. These findings formed the basis for the development of TRAIL-receptor agonists (TRAs) for cancer therapy. However, clinical trials conducted with different types of TRAs have, thus far, afforded only limited therapeutic benefit, as either the respectively chosen agonist showed insufficient anticancer activity or signs of toxicity, or the right TRAIL-comprising combination therapy was not employed. Therefore, in this review we will discuss molecular determinants of TRAIL resistance, the most promising TRAIL-sensitizing agents discovered to date and, importantly, whether any of these could also prove therapeutically efficacious upon cancer relapse following conventional first-line therapies. We will also discuss the more recent progress made with regards to the clinical development of highly active non-immunogenic next generation TRAs. Based thereupon, we next propose how TRAIL resistance might be successfully overcome, leading to the possible future development of highly potent, cancer-selective combination therapies that are based on our current understanding of biology TRAIL-induced cell death. It is possible that such therapies may offer the opportunity to tackle one of the major current obstacles to effective cancer therapy, namely overcoming chemo- and/or targeted-therapy resistance. Even if this were achievable only for certain types of therapy resistance and only for particular types of cancer, this would be a significant and meaningful achievement.

Dihydrotestosterone Increases Cytotoxic Activity of Macrophages on Prostate Cancer Cells via TRAIL

Although androgen deprivation therapy (ADT) and immunotherapy are potential treatment options in men with metastatic prostate cancer (CaP), androgen has conventionally been proposed to be a suppressor of the immune response. However, we herein report that DHT activates macrophages. When the murine macrophage cell line (RAW 264.7), human monocyte cell line (THP-1), and human peripheral blood monocytes were cultured with androgen-resistant CaP cell lines, DHT increased cytotoxicity of macrophages in a concentration-dependent manner. Further studies revealed that DHT induced M1 polarization and increased the expression levels of TNF-related apoptosis-inducing ligand (TRAIL) in macrophages and that this effect was abrogated when TRAIL was neutralized with a blocking antibody or small interfering RNA. Subsequent experiments demonstrated that induction of TRAIL expression was regulated by direct binding of androgen receptor to the TRAIL promoter region. Finally, an in vivo mouse study demonstrated that castration enhanced the growth of an androgen-resistant murine CaP tumor and that this protumorigenic effect of castration was blocked when macrophages were removed with clodronate liposomes. Collectively, these results demonstrate that DHT activates the cytotoxic activity of macrophages and suggest that immunotherapy may not be optimal when combined with ADT in CaP.

TRAIL pathway targeting therapeutics

Introduction

Despite decades of focused research efforts, cancer remains a significant cause of morbidity and mortality. Tumor necrosis factor(TNF)-related apoptosis-inducing ligand (TRAIL) is capable of inducing cell death selectively in cancer cells while sparing normal cells.

Areas covered

In this review, the authors cover TRA therapy and strategies that have been undertaken to improve their efficacy, as well as unconventional approaches to TRAIL pathway activation including TRAIL-inducing small molecules. They also discuss mechanisms of resistance to TRAIL and the use of combination strategies to overcome it.

Expert commentary

Targeting the TRAIL pathway has been of interest in oncology, and although initial clinical trials of TRAIL receptor agonists (TRAs) showed limitations, novel approaches represent the future of TRAIL-based therapy.

The regulation of combined treatment-induced cell death with recombinant TRAIL and bortezomib through TRAIL signaling in TRAIL-resistant cells

Background

Multiple trials have attempted to demonstrate the effective induction of cell death in TRAIL-resistant cancer cells, including using a combined treatment of recombinant TRAIL and various proteasome inhibitors. These studies have yielded limited success, as the mechanism of cell death is currently unidentified. Understanding this mechanism’s driving forces may facilitate the induction of cell death in TRAIL-resistant cancer cells.

Methods

Three kinds of recombinant soluble TRAIL proteins were treated into TRAIL-resistant cells and TRAIL-susceptible cells, with or without bortezomib, to compare their respective abilities to induce cell death. Recombinant TRAIL was treated with bortezomib to investigate whether this combination treatment could induce tumor regression in a mouse syngeneic tumor model. To understand the mechanism of combined treatment-induced cell death, cells were analyzed by flow cytometry and the effects of various cell death inhibitors on cell death rates were examined.

Results

ILz:rhTRAIL, a recombinant human TRAIL containing isoleucine zipper hexamerization domain, showed the highest cell death inducing ability both in single treatment and in combination treatment with bortezomib. In both TRAIL-resistant and TRAIL-susceptible cells treated with the combination treatment, an increase in cell death rates was dependent upon both the dose of TRAIL and its intrinsic properties. When a syngeneic mouse tumor model was treated with the combination of ILz:rhTRAIL and bortezomib, significant tumor regression was seen as a result of the effective induction of cancer cell death. The combination treatment-induced cell death was both inhibited by TRAIL blocking antibody and caspase-dependent. However, it was not inhibited by various ER stress inhibitors and autophagy inhibitors.

Conclusions

The combination treatment with ILz:rhTRAIL and bortezomib was able to induce cell death in both TRAIL-susceptible and TRAIL-resistant cancer cells through the intracellular TRAIL signaling pathway. The efficiency of cell death was dependent on the properties of TRAIL under the environment provided by bortezomib. The combination treatment-induced cell death was not regulated by bortezomib-induced ER stress response or by autophagy.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4352-3) contains supplementary material, which is available to authorized users.

Reciprocal amplification of caspase-3 activity by nuclear export of a putative human RNA-modifying protein, PUS10 during TRAIL-induced apoptosis

Pus10 is a pseudouridine synthase present in Archaea and Eukarya, but not in Bacteria and yeast. It has been suggested that the human PUS10 (DOBI) gene is needed during TRAIL-induced apoptosis. We analyzed the role of PUS10 in TRAIL-induced apoptosis by immunofluorescence, immunoblotting and several indicators of apoptosis. We examined several TRAIL-sensitive cell lines and we also examined some resistant cell lines after treatment with cycloheximide. PUS10 is mainly present in the nucleus. Early during apoptosis, PUS10 translocates to mitochondria via CRM1-mediated export with the concurrent release of cytochrome c and SMAC. Caspase-3 is required for PUS10 translocation, which reciprocally amplifies the activity of caspase-3 through the intrinsic/mitochondrial pathway. This suggests that in addition to cytoplasmic factors, nuclear factors also have a direct role in the major apoptosis pathways. However, p53 is not involved in TRAIL-induced PUS10 movement. The caspase-3-mediated movement of PUS10 and the release of mitochondrial contents enhancing caspase-3 activity creates a feedback amplification loop for caspase-3 action. Therefore, any defect in the movement or interactions of PUS10 would reduce the TRAIL sensitivity of tumor cells.

PU.1 supports TRAIL-induced cell death by inhibiting NF-κB-mediated cell survival and inducing DR5 expression

The hematopoietic Ets-domain transcription factor PU.1/SPI1 orchestrates myeloid, B- and T-cell development, and also supports hematopoietic stem cell maintenance. Although PU.1 is a renowned tumor suppressor in acute myeloid leukemia (AML), a disease characterized by an accumulation of immature blast cells, comprehensive studies analyzing the role of PU.1 during cell death responses in AML treatment are missing. Modulating PU.1 expression in AML cells, we found that PU.1 supports tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis via two mechanisms: (a) by repressing NF-κB activity via a novel direct PU.1-RelA/p65 protein-protein interaction, and (b) by directly inducing TRAIL receptor DR5 expression. Thus, expression of NF-κB-regulated antiapoptotic genes was sustained in PU.1-depleted AML cells upon TRAIL treatment and DR5 levels were decreased. Last, PU.1 deficiency significantly increased AML cell resistance to anthracycline treatment. Altogether, these results reveal a new facet of PU.1's tumor suppressor function during antileukemic therapies.

Potential Role of TRAIL in Metastasis of Mutant KRAS Expressing Lung Adenocarcinoma

Apo2L/tumor necrosis factor (TNF)-α-related apoptosis-inducing ligand (TRAIL, TNFSF10) is an important cytokine in the tumor microenvironment and plays a major role in the balance of cell survival/death pathways. Bioinformatic analyses of 839 adenocarcinoma (AC) and 356 squamous cell lung carcinoma patient data (SCC) by cBioPortal (genomic analyses) shows that TRAIL expression leads to differential outcomes of disease free survival in AC and SCC. Oncomine datamining (transcript analyses) reveal that TRAIL is upregulated in 167 SCC as compared to 350 AC patients from six data sets. Genomic analyses using cBioPortal revealed high rates of KRAS mutation in AC accompanied by higher incidence of metastasis and increased amplifications of TRAIL gene in SCC. Bioinformatic analyses of an additional lung cancer patient database also showed that risk of disease progression was significantly increased with high TRAIL expression in AC (461 samples). In vitro studies demonstrated that TRAIL increased phosphorylation of ERK only in adenocarcinoma cell lines with mutant KRAS. This was associated with increased migration that was abrogated by MEK inhibitor PD98059. Effects of increased migration induced by TRAIL persisted even after exposure to ionizing radiation with suppression of DNA damage response. These results help understand the role of TRAIL signaling in metastasis which is essential to develop strategies to revert these signals into pro-apoptotic pathways.

Paclitaxel enhances tumoricidal potential of TRAIL via inhibition of MAPK in resistant gastric cancer cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) holds promise for cancer therapy due to its unique capacity to selectively trigger apoptosis in cancer cells. However, TRAIL therapy is greatly hampered by its resistance. A preclinical successful strategy is to identify combination treatments that sensitize resistant cancers to TRAIL. In the present study, we fully assessed TRAIL sensitivity in 9 gastric cancer cell lines. We found combined administration of paclitaxel (PTX) markedly enhanced TRAIL-induced apoptosis in resistant cancer cells both in vitro and in vivo. The sensitization to TRAIL was accompanied by activation of mitochondrial apoptotic pathway, upregulation of TRAIL receptors and downregulation of anti-apoptotic proteins including C-IAP1, C-IAP2, Livin and Mcl-1. Noticeably, we found PTX could suppress the activation of mitogen-activated protein kinases (MAPKs). Inhibition of MAPKs using specific inhibitors (ERK inhibitor U0126, JNK inhibitor SP600125 and P38 inhibitor SB202190) facilitated TRAIL-mediated apoptosis and cytotoxicity. Additionally, SP600125 upregulated TRAL receptors as well as downregulated C-IAP2 and Mcl-1 suggesting the anti-apoptotic role of JNK. Thus, PTX-induced suppression of MAPKs may contribute to restoring TRAIL senstitivity. Collectively, our comprehensive analyses gave new insight into the role of PTX on enhancing TRAIL sensitivity, and provided theoretical references on the development of combination treatment in TRAIL-resistant gastric cancer.

Inhibition of Transient Receptor Potential Melastain 7 Enhances Apoptosis Induced by TRAIL in PC-3 cells

Transient receptor potential melastain 7 (TRPM7) is a bifunctional protein with dual structure of both ion channel and protein kinase, participating in a wide variety of diseases including cancer. Recent researches have reported the mechanism of TRPM7 in human cancers. However, the correlation between TRPM7 and prostate cancer (PCa) has not been well studied. The objective of this study was to investigate the potential the role of TRPM7 in the apoptosis of PC-3 cells, which is the key cell of advanced metastatic PCa. In this study, we demonstrated the influence and potential function of TRPM7 on the PC-3 cells apoptosis induced by TNF-related apoptosis inducing-ligand (TRAIL). The study also found a novel up-regulated expression of TRPM7 in PC-3 cells after treating with TRAIL. Suppression of TRPM7 by TRPM7 non-specific inhibitors (Gd3+ or 2-aminoethoxy diphenylborate (2-APB) ) not only markedly eliminated TRPM7 expression level, but also increased the apoptosis of TRAIL-treated PC-3 cells, which may be regulated by the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway accompany with up-regulated expression of cleaved Caspase-3, (TRAIL-receptor 1, death receptors 4) DR4, and (TRAIL-receptor 2, death receptors 5) DR5. Taken together, our findings strongly suggested that TRPM7 was involved in the apoptosis of PC-3 cells induced by TRAIL, indicating that TRPM7 may be applied as a therapeutic target for PCa.

Glycogen synthase kinase-3β regulates tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-induced apoptosis via the NF-κB pathway in hepatocellular carcinoma

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is known for its ability to selectively induce apoptosis in malignant cells. However, human hepatocellular carcinoma (HCC) cells display resistance to TRAIL-induced cell death. The present study investigated whether TRAIL-induced apoptosis in HCC cells was enhanced by the administration of an inhibitor of glycogen synthase kinase-3β (GSK-3β) or by short hairpin RNA-mediated inhibition of GSK-3β. The results of the current study demonstrated that inhibition of GSK-3β significantly impairs the expression of the nuclear factor-κB (NF-κB) target genes Bcl-xL and clAP2 in HCC cells (P<0.05). This indicates that GSK-3β may regulate NF-κB target genes involved in cell survival. Furthermore, knockdown of Bcl-xL significantly enhanced the sensitizing effect of GSK-3β inhibitor on TRAIL-induced apoptosis (P<0.05). Overall, the present study provides a rationale for further exploration of GSK-3β inhibition combined with TRAIL as a novel treatment for HCC.

Controlled delivery of BID protein fused with TAT peptide sensitizes cancer cells to apoptosis

BACKGROUND

Low cellular level of BID is critical for viability of numerous cancer cells. Sensitization of cells to anticancer agents by BID overexpression from adenovirus or pcDNA vectors is a proposed strategy for cancer therapy; however it does not provide any stringent control of cellular level of BID. The aim of this work was to examine whether a fusion of BID with TAT cell penetrating peptide (TAT-BID) may be used for controlled sensitization of cancer cells to anticancer agents acting through death receptors (TRAIL) or DNA damage (camptothecin). Prostate cancer PC3 and LNCaP, non-small human lung cancer A549, and cervix carcinoma HeLa cells were used in the study.

METHODS

Uptake of TAT-BID protein by cells was studied by quantitative Western blot analysis of cells extracts. Cells viability was monitored by MTT test. Apoptosis was detected by flow cytometry and cytochrome c release assay.

RESULTS

TAT-BID was delivered to all cancer cells in amounts depending on time, dose and the cell line. Recombinant BID sensitized PC3 cells to TRAIL or, to lesser extent, to camptothecin. Out of remaining cells, TAT-BID sensitized A549, and only slightly HeLa cells to TRAIL. None of the latter cell lines were sensitized to camptothecin. In all cases the mutant not phosphorylable by CK2 (TAT-BIDT59AS76A) was similarly efficient in sensitization as the wild type TAT-BID.

CONCLUSIONS

TAT-BID may be delivered to cancer cells in controlled manner and efficiently sensitizes PC3 and A549 cells to TRAIL. Therefore, it may be considered as a potential therapeutic agent that enhances the efficacy of TRAIL for the treatment of prostate and non-small human lung cancer.

Getting TRAIL back on track for cancer therapy

Unlike other members of the TNF superfamily, the TNF-related apoptosis-inducing ligand (TRAIL, also known as Apo2L) possesses the unique capacity to induce apoptosis selectively in cancer cells in vitro and in vivo. This exciting discovery provided the basis for the development of TRAIL-receptor agonists (TRAs), which have demonstrated robust anticancer activity in a number of preclinical studies. Subsequently initiated clinical trials testing TRAs demonstrated, on the one hand, broad tolerability but revealed, on the other, that therapeutic benefit was rather limited. Several factors that are likely to account for TRAs' sobering clinical performance have since been identified. First, because of initial concerns over potential hepatotoxicity, TRAs with relatively weak agonistic activity were selected to enter clinical trials. Second, although TRAIL can induce apoptosis in several cancer cell lines, it has now emerged that many others, and importantly, most primary cancer cells are resistant to TRAIL monotherapy. Third, so far patients enrolled in TRA-employing clinical trials were not selected for likelihood of benefitting from a TRA-comprising therapy on the basis of a valid(ated) biomarker. This review summarizes and discusses the results achieved so far in TRA-employing clinical trials in the light of these three shortcomings. By integrating recent insight on apoptotic and non-apoptotic TRAIL signaling in cancer cells, we propose approaches to introduce novel, revised TRAIL-based therapeutic concepts into the cancer clinic. These include (i) the use of recently developed highly active TRAs, (ii) the addition of efficient, but cancer-cell-selective TRAIL-sensitizing agents to overcome TRAIL resistance and (iii) employing proteomic profiling to uncover resistance mechanisms. We envisage that this shall enable the design of effective TRA-comprising therapeutic concepts for individual cancer patients in the future.

Casticin induces caspase-mediated apoptosis via activation of mitochondrial pathway and upregulation of DR5 in human lung cancer cells

OBJECTIVE

To assess if casticin induces caspase-mediated apoptosis via activation of mitochondrial pathway and upregulation of DR5 in human lung cancer cells.

METHODS

Human non-small-cell lung carcinoma cell lines H460, A549 and H157 were cultured in vitro. The cytotoxic activities were determined using MTT assay. The apoptotic cells death was examined by flow cytometry using PI staining and DNA agarose gel electrophoresis. The activities of caspase-3, -8 and -9 were measured via ELISA. Cellular fractionation was determined by flow cytometry to assess release of cytochrome c and the mitochondrial transmembrane potential. Bcl-2/Bcl-XL/XIAP/Bid/DR5 and DR4 proteins were analyzed using western blot.

RESULTS

The concentrations required for a 50% decrease in cell growth (IC(50)) ranged from 1.8 to 3.2 μM. Casticin induced rapid apoptosis and triggered a series of effects associated with apoptosis by way of mitochondrial pathway, including the depolarization of the mitochondrial membrane, release of cytochrome c from mitochondria, activation of procaspase-9 and -3, and increase of DNA fragments. Moreover, the pan caspase inhibitor zVAD-FMK and the caspase-3 inhibitor zDEVD-FMK suppressed casticin-induced apoptosis. In addition, casticin induced XIAP and Bcl-XL down-regulation, Bax upregulation and Bid clearage. In H157 cell line, casticin increased expression of DR5 at protein levels but not affect the expression of DR4. The pretreatment with DR5/Fc chimera protein effectively attenuated casticin-induced apoptosis in H157 cells. No correlation was found between cell sensitivity to casticin and that to p53 status, suggesting that casticin induce a p53-independent apoptosis.

CONCLUSIONS

Our results demonstrate that casticin induces caspase-mediated apoptosis via activation of mitochondrial pathway and upregulation of DR5 in human lung cancer cells.

Standardization of microfluidic cell cultures using integrated organic photodiodes and electrode arrays

Nanotechnology provides the tools to develop novel biosensors with improved performance, including sensitivity and response time that can be readily integrated into diagnostic devices. We have developed a miniaturized cell analysis platform to advance microfluidic cell cultures by combining two complementary, label-free and non-invasive cell analysis methods for the long-term monitoring of dynamic cell behavior. The novel dual-parameter cell-on-a-chip detects light scattering from adherent cells to provide information on cell numbers and intracellular granularity, while simultaneously performing impedance spectroscopy to monitor cell adhesion and cell-cell interaction. In the present work we have integrated spray-coated organic photodiode arrays with a lab-on-a-chip containing embedded interdigitated electrode structures to improve assay reproducibility, reliability and accuracy. We successfully demonstrate that the complementary cell chip technology can accurately detect cell numbers, clarify misleading results during cell-substance interaction assays, as well as the cytotoxicity screening of drug substances. The ability to precisely determine cell numbers within minutes constitutes a major step towards standardization.

Androgens regulate TRAIL-induced cell death in prostate cancer cells via multiple mechanisms

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising therapeutic agent for prostate cancer because it selectively induces apoptosis in cancer cells but not in normal cells. Previous reports have suggested that androgens regulate TRAIL-induced apoptosis in prostate cancer cells. However, there are discrepancies between these reports of how androgens affect TRAIL-induced cell death. To clarify the role of androgens on TRAIL-induced apoptosis in prostate cancer cells, we investigated the effects of androgen on TRAIL-induced cell death in a dose-response manner. Our results showed that although androgens sensitize LNCaP cells to TRAIL-induced apoptosis, this effect is dose-dependent and biphasic. We found that low levels of androgen are superior to high levels of androgen in term of sensitizing LNCaP cells to TRAIL. We also found that upregulation of DR5 (TRAIL-R2) expression by androgens is critical for sensitizing LNCaP cells to TRAIL. However, low levels of androgen are sufficient to induce DR5 expression and sensitize LNCaP cells to TRAIL-induced cell death. High levels of androgen alter the TRADD/RIP1 ratio, which may contribute to NF-κB activation and sequentially inhibit TRAIL-induced apoptosis.

Protective effects of [6]-paradol on histological lesions and immunohistochemical gene expression in DMBA induced hamster buccal pouch carcinogenesis

BACKGROUND

The search for naturally occurring agents in routinely consumed foods that may inhibit cancer development is of high priority. [6]-Paradol is a pungent phenolic bioactive component from ginger with well- documented health promoting antioxidant, antimutagenic, antigenotoxic and anti-inflammatory properties. However, anticarcinogenic effects have yet to be fully explored. The objectives of the present study were therefore to assess protective effects against 7,12-dimethylbenz(a)anthracene (DMBA) induced buccal pouch carcinogenesis in male golden Syrian hamsters.

METHODS

Oral squamous cell carcinomas developed in the left buccal pouch of hamsters on painting with 0.5% of DMBA, three times in a week. To assess the apoptotic associated gene expressing potential of [6]-paradol, it was orally administered to DMBA treated hamsters on alternate days from DMBA painting for 14 weeks.

RESULTS

We observed 100% tumor formation with marked levels of neoplastic changes and altered the expression of apoptotic associated gene (p53, bcl-2, caspase-3 and TNF-α) was observed in the DMBA alone painted hamsters as compared to control hamsters. Oral administration of [6]-paradol at a dose of 30 mg/kg b.wt to DMBA treated animals on alternative days for 14 weeks significantly reduced the neoplastic changes and improved the status of apoptosis associated gene expression.

CONCLUSION

These observations confirmed that [6]-paradol acts as a tumor suppressing agent against DMBA induced oral carcinogenesis. We also conclude that [6]-paradol also effectively enhances apoptosis- associated gene expression in DMBA treated animals.

PI3 Kinase inhibition on TRAIL-induced apoptosis correlates with androgen-sensitivity and p21 expression in prostate cancer cells

TNF-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in many types of cancer cells. TRAIL is considered a therapeutic target, therefore, it was of interest to examine molecular mechanisms that may modulate sensitivity to TRAIL signaling in prostate cancer cells. LNCaP cells were found to be relatively resistant to TRAIL induced cell death while PC3 cells were sensitive. PI3-kinase (PI3 K) inhibitors were able to render LNCaP cells sensitive to TRAIL but conferred resistance to PC3 cells. PI3 K inhibitors were associated with an increase in p21(waf1, cip1) expression in PC3 cells where as p21 decreases in LNCaP cells suggesting that p21 may impart TRAIL resistance. Since androgen receptor (AR) signaling can be modulated by AKT, and p21 is an AR responsive gene, the impact of PI3 K inhibition on TRAIL sensitivity was evaluated in AR transfected PC3 cells (PC3AR). The expression of AR was significantly downregulated by PI3 K inhibition in LNCaP cells, which have an intact AR signaling axis. PC3AR cells expressed higher levels of p21 protein and were relatively resistant to TRAIL compared to control cells. Finally, using adenoviral p21 gene transfer we directly demonstrated that p21 can confer resistance to TRAIL-induced cell death. These results suggest that TRAIL resistance is not regulated simply by a PI3 K/AKT survival pathway associated with inactivating PTEN mutations but may also be modulated by downstream AR responsive targets such as p21. These findings may have significant clinical implications for the utility of TRAIL in the management of prostate cancer.

Isolation of a TRAIL antagonist from the serum of HIV-infected patients

Virus-host interactions are characterized by the selection of adaptive mechanisms by which to evade pathogenic and defense mechanisms, respectively. In primary T cells infected with HIV, HIV infection up-regulates TNF-related apoptosis inducing ligand (TRAIL) and death-inducing TRAIL receptors, but blockade of TRAIL:TRAIL receptor interaction does not alter HIV-induced cell death. Instead, HIV infection results in a novel splice variant that we call TRAIL-short (TRAIL-s), which antagonizes TRAIL-R2. In HIV patients, plasma TRAIL-s concentration increases with increasing viral load and renders cells resistant to TRAIL-induced death. Knockdown of TRAIL-s abrogates this resistance. We propose that TRAIL-s is a novel adaptive mechanism of apoptosis resistance acquired by HIV-infected cells to avoid their elimination by TRAIL-dependent effector mechanism.

Cathepsin E enhances anticancer activity of doxorubicin on human prostate cancer cells showing resistance to TRAIL-mediated apoptosis

We previously described that cathepsin E specifically induces growth arrest and apoptosis in several human prostate cancer cell lines in vitro by catalyzing the proteolytic release of soluble tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) from the tumor cell surface. It also prevents tumor growth and metastasis in vivo through multiple mechanisms, including induction of apoptosis, angiogenesis inhibition and enhanced immune responses. Using the prostate cancer cell line PPC-1, which is relatively resistant to cell death by doxorubicin (40-50% cytotoxicity), we first report that a combination treatment with cathepsin E can overcome resistance of the cells to this agent. In vitro studies showed that combined treatment of PPC-1 cells with the two agents synergistically induces viability loss, mainly owing to down-regulation of a short form of the FLICE inhibitory protein FLIP. The enhanced antitumor activity was corroborated by in vivo studies with athymic mice bearing PPC-1 xenografts. Intratumoral application of cathepsin E in doxorubicin-treated mice results in tumor cell apoptosis and tumor regression in xenografts by enhanced TRAIL-induced apoptosis through doxorubicin-induced c-FLIP down-regulation and by a decrease in tumor cell proliferation. These results indicate that combination of cathepsin E and doxorubicin is sufficient to overcome resistance to TRAIL-mediated apoptosis in chemoresistant prostate cancer PPC-1 cells, thus indicating therapeutic potential for clinical use.

PDTC enables type I TRAIL signaling in type II follicular lymphoma cells

Based on Bcl-X(L) overexpression studies we identified type I and type II follicular lymphoma cell lines in response to TRAIL. We demonstrate here that either amount of caspase-8 activation or Bid cleavage could not define the dependence on mitochondria. Furthermore, an inhibitor of NF-kappaB, PDTC, enabled TRAIL to activate type I apoptotic pathway in type II cells. However, an inhibitor of IKK did not switch apoptosis to type I pathway in type II cells, indicating that NF-kappaB might not be responsible for the switch.

Synergism of CPT-11 and Apo2L/TRAIL against two differentially sensitive human colon tumor xenografts

OBJECTIVE

The ability to sustain and grow portions of human tumors as xenografts in SCID mice provides a valuable preclinical opportunity to test the response of human tumors to treatments, both individually and in combination. Using this model, our laboratory has previously demonstrated that the growth of several human adenocarcinomas can be inhibited by Apo2L/TRAIL. Apo2L/TRAIL triggers apoptosis in many types of tumor cells, and when combined with various chemotherapeutic agents results in enhanced inhibition of tumor growth in many xenograft models.

METHODS

To gain further insight into the antitumor potential of Apo2L/TRAIL in combination with chemotherapy, we compared the responses of 2 human colon adenocarcinomas, both of which were sensitive to CPT-11 while one was sensitive and the other comparatively resistant to Apo2L/TRAIL.

RESULTS

In both cases, a greater degree of growth inhibition was achieved when these agents were used in combination. Western blot analysis demonstrated that in the Apo2L/TRAIL-sensitive tumor total cellular expression of Apo2L/TRAIL death receptors (DR4 and DR5) as well as protein expression of the pro-apoptotic molecule BAX were higher and the anti-apoptotic molecule Bcl-2 was lower in comparison to the Apo2L/TRAIL-resistant tumor.

CONCLUSION

These results indicate that both Apo2L/TRAIL-sensitive and -resistant colon tumors will respond to a combination of CPT-11 and Apo2L/TRAIL and predict that this will be useful in the treatment of human colon cancers in a clinical setting.

ABT-737 induces expression of the death receptor 5 and sensitizes human cancer cells to TRAIL-induced apoptosis

Because Bcl-2 family members inhibit the ability of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce apoptosis, we investigated whether ABT-737, a small molecule Bcl-2 inhibitor, enhances TRAIL killing. We demonstrate that a combination of ABT-737 and TRAIL induced significant cell death in multiple cancer types, including renal, prostate, and lung cancers, although each agent individually had little activity in these tumor cells. All of these cell lines expressed the Mcl-1 protein that is known to block the activity of ABT-737 and TRAIL but did not block the synergy between these agents. However, Bax-deficient cell lines, including DU145 and HCT116 cells and those cell lines expressing low levels of TRAIL receptor, were resistant to apoptosis induced by these agents. To understand how ABT-737 functions to markedly increase TRAIL sensitivity, the levels of specific death-inducing signaling complex components were evaluated. Treatment with ABT-737 did not change the levels of c-FLIP, FADD, and caspase-8 but up-regulated the levels of the TRAIL receptor DR5. DR5 up-regulation induced by ABT-737 treatment occurred through a transcriptional mechanism, and mutagenesis studies demonstrated that the NF-kappaB site found in the DR5 promoter was essential for the ability of ABT-737 to increase the levels of this mRNA. Using luciferase reporter plasmids, ABT-737 was shown to stimulate NF-kappaB activity. Together, these results demonstrate that the ability of ABT-737 and TRAIL to induce apoptosis is mediated through activation of both the extrinsic and intrinsic pathways. Combinations of ABT-737 and TRAIL can be exploited therapeutically where antiapoptotic Bcl-2 family members drive tumor cell resistance to current anticancer therapies.

TRAIL-receptor antibodies as a potential cancer treatment

Increasing attention has been focused on the use of agonistic monoclonal antibodies against TNF-related apoptosis-inducing ligand (TRAIL) death receptors DR4 or DR5 as a potential cancer treatment. These antibodies have strong apoptosis-inducing activity against cancer cells and potent antitumor activity against tumor xenografts in preclinical models that are enhanced by combination chemotherapy treatment. There are several agonistic humanized or human monoclonal antibodies against DR4 and DR5 that have been tested in Phase I and II trials in patients with advanced cancer. These trials have demonstrated these antibodies to be well tolerated, and to produce prolonged stable disease, which is the best antitumor effect in patients with advanced cancer. Clinical studies in which TRAIL-receptor antibodies are being investigated in combination treatment regimens in patients with advanced cancer are ongoing. It is anticipated that the results from a broad spectrum of cancer therapy clinical trials will identify the activity and toxicity profiles of TRAIL death-receptor antibodies as a single agent, or in combination with chemotherapy agents or radiation therapy.

Analysis of TNF-related apoptosis-inducing ligand in vivo through bone marrow transduction and transplantation

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family of cytokines. TRAIL has gained much attention because of its ability to preferentially kill tumor cells with no apparent toxic side effects. Recently, different TRAIL receptor agonists, including TRAIL itself and various agonistic monoclonal antibodies against the two apoptosis-inducing human TRAIL receptors, have been developed as novel cancer therapeutics and are currently under investigation in clinical trials. However, the mechanisms by which TRAIL mediates its selective antineoplastic activity are still not well understood. In addition to playing a role in cancer immune surveillance and tumor suppression, TRAIL has been associated with immune homeostasis, inflammatory diseases, and autoimmunity. In light of the multifunctional role of TRAIL in mediating various pathologic conditions and the potential benefits of TRAIL-based therapies, the study of the physiologic significance of TRAIL is of great importance. Here, we describe a syngeneic system for the characterization of the in vivo function of TRAIL. By use of this model, in which the full-length murine TRAIL protein is overexpressed in the hematopoietic cells of wild-type mice, the in vivo tumoricidal activity of TRAIL overexpression can be studied on syngeneic murine tumor cell challenge, and the potential toxicity of TRAIL protein to normal tissues can also be analyzed.

TRAIL receptor-targeted therapy

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family of cytokines. Based on its ability to induce apoptosis selectively in a wide variety of cancer cell lines and human tumor xenografts, TRAIL has been in drug development as a potential biological agent for cancer therapy. A variety of chemotherapy agents have been shown to enhance the cytotoxic effects of TRAIL. The potential benefits of TRAIL as an anticancer therapy have been further indicated by its ability to enhance the efficacy of radiotherapy. Preclinical studies have shown the potential use of agonistic monoclonal antibodies that selectively bind TRAIL death receptors for cancer therapy. This review provides an overview of TRAIL receptor-mediated apoptosis of tumor cells, with TRAIL or agonistic monoclonal antibodies only or with chemotherapy drugs. Treatment of tumor xenografts with these ligands, alone or in combination with chemotherapy or radiation, are discussed along with preliminary information about early clinical trials. Additional clinical trials with TRAIL receptor ligands in combination treatment regimens are required to determine their potential for targeted therapy of cancer.

Transduction of tumor necrosis factor-related apoptosis-inducing ligand into hematopoietic cells leads to inhibition of syngeneic tumor growth in vivo

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF family of cytokines and has been shown to induce cell death in many types of tumor and transformed cells but not in normal cells. This tumor-selective property has made TRAIL a promising candidate for the development of cancer therapy. However, safety issues are a concern because certain preparations of recombinant TRAIL protein were reported to induce toxicity in normal human hepatocytes in culture. In addition, previous studies on tumor selectivity of exogenous TRAIL protein were carried out in xenograft models, which do not directly address the tumor selectivity issue. It was not known whether exogenous or overexpression of TRAIL in a syngeneic system could induce tumor cell death while leaving normal tissue cells unharmed. Thus, the tumor selectivity of TRAIL-induced apoptosis remains to be further characterized. In our study, we established mice that overexpress TRAIL by retroviral-mediated gene transfer in bone marrow cells followed by bone marrow transplantation. Our results show that TRAIL overexpression is not toxic to normal tissues, as analyzed by hematologic and histologic analyses of tissue samples from TRAIL-transduced mice. We show for the first time that TRAIL overexpression in hematopoietic cells leads to significant inhibition of syngeneic tumor growth in certain tumor lines. This approach may be used further to identify important molecules that regulate the sensitivity of tumor cells to TRAIL-induced cell death in vivo.

Inorganic selenium sensitizes prostate cancer cells to TRAIL-induced apoptosis through superoxide/p53/Bax-mediated activation of mitochondrial pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in prostate cancer cells through DR4 and DR5 death receptors, but not in normal prostate cells, which do not express these receptors. Therefore, TRAIL has excellent potential to be a selective prostate cancer therapeutic agent with minimal toxic side effects. However, prostate cancer cells, as many other cancer types, develop resistance to TRAIL, and the underlying molecular mechanisms require further investigation. We hypothesize that selenium may sensitize TRAIL-resistant cells to undergo caspase-mediated apoptosis and increase therapeutic efficacy. Here, we report that TRAIL signaling in LNCaP prostate cancer cells stalled at downstream of caspase-8 and BID cleavage, as indicated by the lack of Bax translocation into mitochondria, and no subsequent activation of the caspase-9 cascade. Selenite induced a rapid generation of superoxide and p53 Ser(15) phosphorylation and increased Bax abundance and translocation into the mitochondria. Selenite and TRAIL combined treatment led to synergistic increases of Bax abundance and translocation into mitochondria, loss of mitochondrial membrane potential, cytochrome c release, and cleavage activation of caspase-9 and caspase-3. Inactivating p53 with a dominant-negative mutant abolished apoptosis without affecting superoxide generation, whereas a superoxide dismutase mimetic agent blocked p53 activation, Bax translocation to mitochondria, cytochrome c release, and apoptosis induced by selenite/TRAIL. In support of Bax as a crucial target for cross-talk between selenite and TRAIL pathways, introduction of Bax into p53 mutant DU145 cells enabled selenite to sensitize these cells for TRAIL-induced apoptosis. Taken together, the results indicate that selenite induces a rapid superoxide burst and p53 activation, leading to Bax up-regulation and translocation into mitochondria, which restores the cross-talk with stalled TRAIL signaling for a synergistic caspase-9/3 cascade-mediated apoptosis execution.

Identification of cell cycle regulatory genes as principal targets of p53-mediated transcriptional repression

Historically, most studies attribute p53 function to the transactivation of target genes. That p53 can selectively repress genes to affect a cellular response is less widely appreciated. Available evidence suggests that repression is important for p53-induced apoptosis and cell cycle arrest. To better establish the scope of p53-repressed target genes and the cellular processes they may affect, a global expression profiling strategy was used to identify p53-responsive genes following adenoviral p53 gene transfer (Ad-p53) in PC3 prostate cancer cells. A total of 111 genes, 0.77% of the 14,500 genes represented on the Affymetrix U133A microarray, were repressed more than 2-fold (p < or = 0.05). Validation of the array data, using reverse transcription-PCR of 20 randomly selected genes, yielded a confirmation rate of >95.5% for the complete data set. Functional over-representation analysis revealed that cell cycle regulatory genes exhibited a highly significant enrichment (p < or = 5 x 10(-28)) within the transrepressed targets. 41% of the repressed targets are cell cycle regulators. A subset of these genes exhibited repression following DNA damage, preceding cell cycle arrest, in LNCaP cells. The use of a p53 small interfering RNA strategy in LNCaP cells and the use of p53-null cell lines demonstrated that this repression is p53-dependent. These findings identify a set of genes not known previously to be down-regulated by p53 and indicate that p53-induced cell cycle arrest is a function of not only the transactivation of cell cycle inhibitors (e.g. p21) but also the repression of targets that regulate proliferation at several distinct phases of the cell cycle.

Immunohistochemical study of cell proliferation, Bcl-2, p53, and caspase-3 expression on preneoplastic changes induced by cadmium and zinc chloride in the ventral rat prostate

This work was directed to evaluate immunoexpression of markers for apoptosis, resistance to apoptosis, and cell proliferation, as well as estimates of nuclear size in ventral prostate of rats treated with cadmium chloride and cadmium+zinc chloride because a possible protective effect of zinc has been postulated. The following variables were studied: volume fraction (VF) of Bcl-2 immunostaining, percentage of cells immunoreactive to proliferating cell nuclear antigen (LIPCNA) and p53 (LIp53), numerical density of caspase-3 immunoreactive cells (NV caspase-3), and estimates of volume-weighted mean nuclear volume (upsilonV). The LIPCNA and VF of Bcl-2 were significantly increased in the treated animals. The dysplasias (independent of their origin) showed a significant increase of the LIp53, NV caspase-3, and upsilonV in comparison with normal acini from treated and control animals. It can be concluded that cell proliferation is enhanced in long-term cadmium-exposed rats, and exposure to zinc combined with cadmium had no effect on any of the variables studied when comparing with normal acini. The increase of nuclear upsilonV could indicate a more aggressive behavior for pretumoral lesions.

Decreased intracellular zinc in human tumorigenic prostate epithelial cells: a possible role in prostate cancer progression

Background

Zinc plays important roles in maintaining normal function of the prostate and in development of prostate malignancy. It has been demonstrated that prostate malignant epithelial cells contain much less cellular zinc than the surrounding normal epithelial cells. However, the pathway(s) which leads to lower zinc accumulation in malignant prostate epithelial cells is poorly understood. In this study, the zinc homeostatic features of two human prostate epithelial cell lines (non-tumorigenic, RWPE1, and tumorigenic, RWPE2) were investigated. Effects of over-expression of ZIP1 in RWPE2 on cell proliferation and apoptosis were also studied.

Results

RWPE2 accumulated less intracellular zinc than RWPE1 due to the decreased zinc uptake activity. The mRNA expression of ZIP1 and ZIP3 in RWPE1 and RWPE2 was comparable. However, the protein expression of ZIP1 in RWPE2 was lower than that in RWPE1. ZIP3 was detected in a lysosomal compartment of RWPE2 while no ZIP3 was detected in the same compartment of RWPE1. Over-expression of ZIP1 in RWPE2 resulted in an elevation of intracellular zinc concentration and suppression of cell growth of RWPE2 due to the increased apoptosis.

Conclusion

These findings suggest that tumorigenic prostate epithelial cells accumulated less intracellular zinc than non-tumorigenic prostate epithelial cells. The reduction in capacity for accumulation of intracellular zinc in tumorigenic prostate epithelial cells may be caused by the decrease in the ZIP1 protein expression and the intracellular redistribution of ZIP3 in RWPE2. RWPE1 and RWPE2 are excellent cellular models to study the association of intracellular zinc levels with prostate cancer progression.

Functional expression of TRAIL receptors TRAIL-R1 and TRAIL-R2 in esophageal adenocarcinoma

The tumour necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL/Apo2L) is a member of the TNF superfamily that preferentially induces apoptosis in cancer cells, while sparing normal cells. TRAIL induces apoptosis by interacting with its receptors TRAIL-R1 and TRAIL-R2. Recently, new humanized agonistic anti-TRAIL-R1 and anti-TRAIL-R2 antibodies have been developed, and are undergoing phase I/II clinical trails. Esophageal adenocarcinoma (EA) is associated with significantly poor outcome and is rapidly increasing in incidence in the United States and Western Europe, with virtually no effective non-surgical treatment. The aim of this study was to determine whether human EA tissue express TRAIL-R1 and/or TRAIL-R2, and whether EA cell lines Bic-1 and Seg-1 expresses functional TRAIL-R1 and/or TRAIL-R2. The expression of TRAIL-R1 and TRAIL-R2 was determined in sections from 18 human EA by immunohistochemistry (IHC). Sixteen (89%) of the EA expressed TRAIL-R1 and 17 (94%) expressed TRAIL-R2. Both cell lines were found to express TRAIL-R1 and TRAIL-R2 by western blot analysis, IHC, and flow cytometry. The fully human agonistic TRAIL-R1 (HGS-ETR1) and TRAIL-R2 (HGS-ETR2) antibodies induced apoptosis in Bic-1 and Seg-1 cells in a time and dose dependent manner. Our results show that the vast majority of primary human EA express TRAIL-R1 and TRAIL-R2 and that EA cells lines express functional TRAIL-R1 and TRAIL-R2. Targeting of these receptors by agonist monoclonal antibodies may be of therapeutic value in patients with EA.

Sulindac sulfide–induced apoptosis is enhanced by a small-molecule Bcl-2 inhibitor and by TRAIL in human colon cancer cells overexpressing Bcl-2

Sulindac is a nonsteroidal anti-inflammatory drug (NSAID) that induces apoptosis in cultured colon cancer cells and in intestinal epithelia in association with its chemopreventive efficacy. Resistance to sulindac is well documented in patients with familial adenomatous polyposis; however, the molecular mechanisms underlying such resistance remain unknown. We determined the effect of ectopic Bcl-2 expression upon sulindac-induced apoptotic signaling in SW480 human colon cancer cells. Sulindac sulfide activated both the caspase-8-dependent and mitochondrial apoptotic pathways. Ectopic Bcl-2 attenuated cytochrome c release and apoptosis induction compared with SW480/neo cells. Coadministration of sulindac sulfide and the small-molecule Bcl-2 inhibitor HA14-1 increased apoptosis induction and enhanced caspase-8 and caspase-9 cleavage, Bax redistribution, and cytochrome c and second mitochondria-derived activator of caspase release. Given that sulindac sulfide activated caspase-8 and increased membrane death receptor (DR4 and DR5) protein levels, we evaluated its combination with the endogenous death receptor ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Coadministration of sulindac sulfide and TRAIL cooperatively enhanced apoptotic signaling as effectively as did HA14-1. Together, these data indicate that HA14-1 or TRAIL can enhance sulindac sulfide-induced apoptosis and represent novel strategies for circumventing Bcl-2-mediated apoptosis resistance in human colon cancer cells.

Tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis is inhibited by Bcl-2 but restored by the small molecule Bcl-2 inhibitor, HA 14-1, in human colon cancer cells

PURPOSE

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent that induces apoptosis in multiple tumor cell types while sparing most normal cells. We determined the effect of ectopic Bcl-2 expression on TRAIL-induced apoptosis and whether the small molecule Bcl-2 inhibitor, HA14-1, could increase TRAIL sensitivity.

EXPERIMENTAL DESIGN

SW480 human colon cancer cells were stably transfected with the PC3-Bcl-2 plasmid or vector alone. Cells were incubated with recombinant human TRAIL +/- HA14-1 or caspase-9 inhibitor (Z-LEHD-FMK). Apoptosis was analyzed by Annexin V-fluorescein isothiocyanate labeling and DNA fragmentation factor 45 (DFF45) cleavage. Clonigenic survival was also studied. Caspase activation was determined by immunoblotting or colorimetric assay. The cytosolic expression of Bid, Bax, and XIAP and release of cytochrome c and Smac/DIABLO were determined by immunoblotting.

RESULTS

Bcl-2 overexpression partially protected SW480 cells from a dose-dependent induction of apoptosis by TRAIL, as did a caspase-9 inhibitor, and increased their clonogenic survival. Bcl-2 overexpression attenuated TRAIL-induced cleavage of caspase-8, indicating its activation upstream and downstream of mitochondria, as well as cleavage of Bid and caspase-3. Bcl-2 inhibited TRAIL-induced Bax translocation, cytosolic release of cytochrome c and Smac/DIABLO, and the downstream cleavage of XIAP and DFF45. Coadministration of HA14-1 and TRAIL increased apoptosis in SW480/Bcl-2 cells by restoring Bax redistribution and cytochrome c release.

CONCLUSIONS

Bcl-2 confers apoptosis resistance to TRAIL by inhibiting a mitochondrial amplification step and by inactivating downstream XIAP in SW480 cells. HA14-1 reversed Bcl-2-mediated TRAIL resistance, suggesting a novel strategy for increasing TRAIL sensitivity in Bcl-2-overexpressing colon cancers.

Reactive Oxygen Species Regulate Caspase Activation in Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand–Resistant Human Colon Carcinoma Cell Lines

The effects of reactive oxygen species (ROS) on tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in solid cancers have yet to be clearly defined. In this study, we found that the classic uncoupler of oxidative phosphorylation, carbonyl cyanide m-chlorophenylhydrazone (CCCP), induced a reduction in DeltaPsim and generation of ROS. This uncoupling effect enhanced TRAIL-induced apoptosis in TRAIL-resistant human colon carcinoma cell lines (RKO, HT29, and HCT8). Sensitization was inhibited by benzyloxycarbonyl-valine-alanine-aspartate fluoromethylketone, indicating the requirement for caspase activation. CCCP per se did not induce apoptosis or release of proapoptotic factors from mitochondria. Generation of ROS by CCCP was responsible for TRAIL-induced Bax and caspase activation because scavenging ROS completely abrogated apical caspase-8 activation and further downstream events leading to cell death. Overexpression of Bcl-2 did not prevent the initial loss of DeltaPsim and ROS generation following CCCP treatment, but did prevent cell death following TRAIL and CCCP exposure. Uncoupling of mitochondria also facilitated TRAIL-induced release of proapoptotic factors. X-linked inhibitor of apoptosis overexpression abrogated TRAIL-induced apoptosis in the presence of CCCP and decreased initiator procaspase-8 processing, indicating that additional processing of caspase-8 required initiation of a mitochondrial amplification loop via effector caspases. Of interest, depletion of caspase-9 in RKO cells did not protect cells from TRAIL/CCCP-induced apoptosis, indicating that apoptosis occurred via a caspase-9-independent pathway. Data suggest that in the presence of mitochondrial-derived ROS, TRAIL induced mitochondrial release of Smac/DIABLO and inactivation of X-linked inhibitor of apoptosis through caspase-9-independent activation of caspase 3.

Activity of selective fully human agonistic antibodies to the TRAIL death receptors TRAIL-R1 and TRAIL-R2 in primary and cultured lymphoma cells: induction of apoptosis and enhancement of doxorubicin- and bortezomib-induced cell death

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is a death protein that preferentially kills tumour cells while sparing normal cells. TRAIL has four exclusive receptors, two of which (TRAIL-R1, TRAIL-R2) are death receptors. Both TRAIL/Apo2L and agonistic antibodies to the TRAIL death receptors are currently being explored for cancer therapy. Although the activity of TRAIL/Apo2L in a variety of haematological malignancies has been examined, the activity of anti-TRAIL receptor agonistic antibodies in primary and cultured lymphoma cells has not. Using two fully human selective agonistic monoclonal antibodies to the TRAIL death receptors TRAIL-R1 (HGS-ETR1) and TRAIL-R2 (HGS-ETR2) this study demonstrated that both monoclonal antibodies activated caspase-8 and induced cell death in five of nine human lymphoma cell lines, and induced >10% cell death in 67% and 70%, respectively, of 27 primary lymphoma cells, and >20% cell death in at least one-thirds of the samples. HGS-ETR1 and HGS-ETR2 demonstrated comparable activity in the fresh tumour samples, which was independent of TRAIL receptor surface expression, Bax, cFLIP, or procaspase-8 expression, or exposure to prior therapy. Furthermore, both antibodies enhanced the killing effect of doxorubicin and bortezomib. Our data demonstrate that HGS-ETR1 and HGS-ETR2 monoclonal antibodies can induce cell death in a variety of cultured and primary lymphoma cells, and may have therapeutic value in lymphoma.

Role of tumor necrosis factor-related apoptosis-inducing ligand in immune response to influenza virus infection in mice

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis of various tumor cells but not normal cells. However, various cytokines and virus infection differentially regulate TRAIL and TRAIL receptor expression. It has been demonstrated that virus infection changes the pattern of human TRAIL-receptor expression on normal cells, which were resistant to TRAIL-mediated apoptosis, and makes them susceptible to TRAIL-mediated apoptosis. Since previous studies on the function of TRAIL have been performed mainly in vitro, its physiological role in the immune response to virus infection remains unknown. In the present study, we investigated the expression of TRAIL in the lungs of influenza virus-infected mice and the function of TRAIL in the immune response to infection. Influenza virus infection increased TRAIL mRNA expression in the lung. TRAIL protein expression was induced on NK cells in the lung 4 days after infection. At 7 days after infection, TRAIL protein expression was also detected on CD4(+) and CD8(+) T cells. However, NK cells and T cells in the lungs of uninfected mice did not express a detectable level of TRAIL on their cell surfaces. DR5, which is a mouse TRAIL receptor, was also induced to express after virus infection. Expression of both TRAIL and DR5 mRNAs was reduced to normal level at 6 weeks after virus infection. Administration of anti-TRAIL monoclonal antibody, which blocks TRAIL without killing TRAIL-expressing cells, to mice during influenza virus infection significantly delayed virus clearance in the lung. These results suggest that TRAIL plays an important role in the immune response to virus infection.

Enhancement of therapeutic potential of TRAIL by cancer chemotherapy and irradiation: mechanisms and clinical implications

Activation of cell surface death receptors by their cognate ligands triggers apoptosis. Several human death receptors (Fas, TNF-R1, TRAMP, DR4, DR5, DR6, EDA-R and NGF-R) have been identified. The most promising cytokine for anticancer therapy is TRAIL/APO-2L, which induces apoptosis in cancer cells by binding to death receptors TRAIL-R1/DR4 and TRAIL-R2/DR5. The cytotoxic activity of TRAIL is relatively selective to cancer cells compared to normal cells. Signaling by TRAIL and its receptors is tightly regulated process essential for key physiological functions in a variety of organs, as well as the maintenance of immune homeostasis. Despite early promising results, recent studies have identified several TRAIL-resistant cancer cells of various origins. Based on molecular analysis of death-receptor signaling pathways several new approaches have been developed to increase the efficacy of TRAIL. Resistance of cancer cells to TRAIL appears to occur through the modulation of various molecular targets. They may include differential expression of death receptors, constitutively active Akt and NFkappaB, overexpression of cFLIP and IAPs, mutations in Bax and Bak genes, and defects in the release of mitochondrial proteins in resistant cells. Conventional chemotherapeutic and chemopreventive drugs, and irradiation can sensitize TRAIL-resistant cells to undergo apoptosis. Thus, these agents enhance the therapeutic potential of TRAIL in TRAIL-sensitive cells and sensitize TRAIL-resistant cells. TRAIL and TRAIL-receptor antibodies may prove to be useful for cancer therapy, either alone or in association with conventional approaches such as chemotherapy or radiation therapy. This review discusses intracellular mechanisms of TRAIL resistance and various approaches that can be taken to sensitize TRAIL-resistant cancer cells.

Death Receptor Regulation and Celecoxib-Induced Apoptosis in Human Lung Cancer Cells

BACKGROUND

Celecoxib, a cyclooxygenase 2 inhibitor, has chemopreventive and therapeutic activities toward lung cancer and other epithelial malignancies. Celecoxib can induce apoptosis in various cancer cell lines through a mechanism that is independent of its cyclooxygenase 2 inhibitory activity but is otherwise largely uncharacterized. We investigated the mechanism of celecoxib-induced apoptosis further.

METHODS

All experiments were conducted in human non-small-cell lung carcinoma (NSCLC) cell lines; results in celecoxib-treated and untreated cells were compared. Cell survival was assessed with a sulforhodamine B assay. Apoptosis was assessed by DNA fragmentation with an enzyme-linked immunosorbent assay, by terminal deoxynucleotidyltransferase-mediated dUTP nick-end-labeling (TUNEL) assay, and by western blot analysis of caspase activation. Death receptor gene and protein expression was detected by northern and western blot analysis, respectively. Gene silencing was achieved with small interfering RNA (siRNA) technology.

RESULTS

Celecoxib treatment decreased cell survival, activated caspase cascades, and increased DNA fragmentation, all of which were abrogated when caspase 8 expression was silenced with caspase 8 siRNA. Celecoxib treatment induced the expression of death receptors, particularly that of DR5. Overexpression of a dominant negative Fas-associated death domain mutant, but not of BCL2, reduced the level of celecoxib-induced apoptosis, and silencing of DR5 expression by DR5 siRNA suppressed celecoxib-induced caspase 8 activation and apoptosis. Combination treatment with celecoxib and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induced additional apoptosis. For example, survival of A549 cells was decreased with 50 muM celecoxib alone by 38.7% (95% confidence interval [CI] = 35.2% to 42.2%), with TRAIL alone by 29.3% (95% CI = 25.1% to 33.6%), but with their combination by 77.5% (95% CI = 74.5% to 79.5%), a greater than additive effect.

CONCLUSION

Celecoxib appears to induce apoptosis in human NSCLC through the extrinsic death receptor pathway.

A tumor-targeted and conditionally replicating oncolytic adenovirus vector expressing TRAIL for treatment of liver metastases

We have constructed a new capsid-modified adenovirus (Ad) vector that specifically replicates in tumor cells and expresses TNF-related apoptosis-inducing ligand (TRAIL). The Ad capsid contains short-shafted fibers derived from Ad serotype 35, which allow for efficient infection of malignant tumor cells, and largely avoids innate toxicity after intravenous application. Replication-dependent homologous recombination in Ad genomes was used to achieve tumor-specific expression of Ad E1a (to mediate viral replication) and TRAIL (to mediate apoptosis and enhance release of progeny virus from infected cells). We demonstrated that our oncolytic vector (Ad5/35.IR-E1A/TRAIL) induced apoptosis in human tumor cell lines derived from colorectal, lung, prostate, and liver cancer. Both in vitro and in vivo tumor models showed efficient intratumoral spread of this vector. In a model for metastatic colon cancer, tail vein infusion of Ad5/35.IR-E1A/TRAIL resulted in elimination of preestablished liver metastases. Intravenous injection of this vector caused a transient elevation of serum glutamic pyruvic transaminase in tumor-bearing mice, which we attributed to factors released from apoptotic tumor cells. Liver histology analyzed at day 14 after virus injection did not show signs of hepatocellular damage. This new oncolytic vector represents a potentially efficient means for gene therapy of metastatic cancer.

Persistent c-FLIP(L) expression is necessary and sufficient to maintain resistance to tumor necrosis factor-related apoptosis-inducing ligand-mediated apoptosis in prostate cancer

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in a variety of tumorigenic and transformed cell lines but not in many normal cells. Hence, TRAIL has the potential to be an ideal cancer therapeutic agent with minimal cytotoxicity. FLICE inhibitory protein (c-FLIP) is an important regulator of TRAIL-induced apoptosis. Here, we show that persistent expression of c-FLIP(Long) [c-FLIP(L)] is inversely correlated with the ability of TRAIL to induce apoptosis in prostate cancer cells. In contrast to TRAIL-sensitive cells, TRAIL-resistant LNCaP and PC3-TR (a TRAIL-resistant subpopulation of PC3) cells showed increased c-FLIP(L) mRNA levels and maintained steady protein expression of c-FLIP(L) after treatment with TRAIL. Ectopic expression of c-FLIP(L) in TRAIL-sensitive PC3 cells changed their phenotype from TRAIL sensitive to TRAIL resistant. Conversely, silencing of c-FLIP(L) expression by small interfering RNA in PC3-TR cells reversed their phenotype from TRAIL resistant to TRAIL sensitive. Therefore, persistent expression of c-FLIP(L) is necessary and sufficient to regulate sensitivity to TRAIL-mediated apoptosis in prostate cancer cells.

Antitumor effects of bortezomib (PS-341) on primary effusion lymphomas

Primary effusion lymphomas (PELs) are a rare type of non-Hodgkin's lymphoma that are resistant to cytotoxic chemotherapy. PELs manifest constitutive activation of nuclear factor kappa B (NF-kappaB), and inhibition of NF-kappaB induces apoptosis of PELs and sensitizes to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced death. Bortezomib (PS-341), a peptidyl boronic acid inhibitor of the proteasome, is a potent agent against a wide range of hematologic malignancies and has been shown to inhibit NF-kappaB. Thus, we examined the cytotoxic effects of bortezomib alone and in combination with various drugs. Bortezomib potently inhibited NF-kappaB in PEL cells in a dose-dependent manner. In addition, bortezomib inhibited growth and induced apoptosis of PEL cell lines (IC(50) values of 3.4-5.0 nM). Results of drug interactions between bortezomib and chemotherapy (doxorubicin and Taxol) were schedule-dependent: synergistic interactions were generally observed when PEL cells were pretreated with bortezomib prior to chemotherapy, whereas additive or even antagonistic interactions occurred with chemotherapy pretreatment or simultaneous treatment with bortezomib and chemotherapy. Most schedules of bortezomib and dexamethasone were synergistic, although pretreatment with dexamethasone resulted in additive interactions. Effects of combinations of bortezomib and TRAIL were generally additive. Thus, bortezomib represents a promising potential therapy for the treatment of PEL.

Programmed cell death and survival pathways in prostate cancer cells

Programmed cell death, or apoptosis, is a series of morphologically and biochemically related processes. The extrinsic (death receptor mediated) and intrinsic (mitochondrial-mediated) apoptotic pathways can be triggered by physiological and pharmacological substances. However, other molecular events influence the sensitivity of prostate cancer cells to apoptotic stimuli, leading to marked variations in the responsiveness of prostate cancer cell lines to individual stimuli. Modulation of apoptotic responses by over expression of anti-apoptotic proteins (NF-kappaB, IAPs and Bcl-2), or attenuation of pro-apoptotic proteins (PTEN and Bax) may be responsible for the variations in sensitivity of these cell lines to hormone and chemotherapy. The expression of anti- and pro-apoptotic proteins in some of the widely used in vitro models of prostate cancer is reviewed.

Death receptor-induced cell death in prostate cancer

Prostate cancer mortality results from metastasis and is often coupled with progression from androgen-dependent to androgen-independent growth. Unfortunately, no effective treatment for metastatic prostate cancer increasing patient survival is available. The absence of effective therapies reflects in part a lack of knowledge about the molecular mechanisms involved in the development and progression of this disease. Apoptosis, or programmed cell death, is a cell suicide mechanism that enables multicellular organisms to regulate cell number in tissues. Inhibition of apoptosis appears to be a critical pathophysiological factor contributing to the development and progression of prostate cancer. Understanding the mechanism(s) of apoptosis inhibition may be the basis for developing more effective therapeutic approaches. Our understanding of apoptosis in prostate cancer is relatively limited when compared to other malignancies, in particular, hematopoietic tumors. Thus, a clear need for a better understanding of apoptosis in this malignancy remains. In this review we have focused on what is known about apoptosis in prostate cancer and, more specifically, the receptor/ligand-mediated pathways of apoptosis as potential therapeutic targets.

Addition of anticancer agents enhances freezing-induced prostate cancer cell death: implications of mitochondrial involvement

Recent evidence suggests that the successful treatment of prostate cancer may require adjuvant therapies. Accordingly, a better understanding of the molecular mechanisms involved in current treatments may lead to enhanced efficacy by providing a basis for adjuvant therapies. In this study, we demonstrate that the combination of sub-lethal concentrations of chemotherapeutic agents prior to freezing (-15 degrees C) in a prostate cancer cell (PC-3) model results in enhanced efficacy over either treatment alone. Morphological analysis revealed that necrosis appeared to be the prevalent mode of cell death following adjuvant (in vitro) modeling, yet molecular analysis indicated that freezing and chemotherapy differentially activated apoptotic cascades through modulating opposing members of the Bcl-2 protein family. Freezing results in a time-dependent increase of the antiapoptotic Bcl-2 protein, while chemotherapy results in an increase of the pro-apoptotic Bax protein. Anti-apoptotic Bcl-2 protein levels increase over 3-fold following exposure to freezing. 5-Fluorouracil (5-FU) causes pro-apoptotic Bax levels to increase 2-fold during the drug exposure. The increase in Bax was also apparent following the combination of 5-FU/freezing, while Bcl-2 levels were maintained at or below control levels. This led to a shift in the Bcl-2 to Bax ratio to a pro-death tendency. Other effective cryo/chemo combinations were also found to provide similar effects. The combination of cisplatin/freezing resulted in a 4-fold increase in the ratio of Bax to Bcl-2 when compared to controls, which represented a 2-fold increase over the 5-FU/freezing-combination model. This increase may contribute to the continued reduction in cell number observed during the 13-day recovery period. Additionally, the addition of an apoptotic caspase inhibitor was not able to protect cultures from cell death following combination treatment. In conclusion, the data suggest that both Bcl-2 and Bax may, not only, play an important role in the efficacy of the cryo/chemo combination, but also the balance between the two may determine the role and extent of system destruction.