Efficient TRAIL-R1/DR4-Mediated Apoptosis in Melanoma Cells by Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL)

Genomic and molecular landscape of gallbladder cancer elucidating pathogenic mechanisms novel therapeutic targets and clinical implications

Gallbladder cancer (GBC) is an aggressive malignancy with a poor prognosis, often diagnosed at advanced stages due to subtle early symptoms. Recent studies have provided a comprehensive view of GBC's genetic and mutational landscape, uncovering crucial pathways involved in its pathogenesis. Environmental exposures, particularly to heavy metals, have been linked to elevated GBC risk. Established signaling pathways, including hormonal, apoptotic, metabolic, inflammatory, and DNA damage repair pathways, are integral to GBC progression, and evidence points to the involvement of specific germline and somatic mutations in its development. Key mutations in genes such as KRAS, TP53, IDH1/2, ERBB, PIK3CA, MET, MYC, BRAF, MGMT, CDKN2A and p16 have been identified as contributors to tumorigenesis, with additional alterations including chromosomal aberrations and epigenetic modifications. These molecular insights reveal several potential therapeutic targets that could address the limited treatment options for GBC. Promising therapeutic avenues under investigation include immune checkpoint inhibitors, tyrosine kinase inhibitors, tumor necrosis factor-related apoptosis-inducing ligands (TRAIL), and phytochemicals. Numerous clinical trials are assessing the efficacy of these targeted therapies. This review provides a detailed examination of GBC's genetic and mutational underpinnings, highlighting critical pathways and emerging therapeutic strategies. We discuss the implications of germline and somatic mutations for early detection and individualized treatment, aiming to bridge current knowledge gaps. By advancing our understanding of GBC's molecular profile, we hope to enhance diagnostic accuracy and improve treatment outcomes, ultimately paving the way for precision medicine approaches in managing GBC.

Nanoparticle-mediated gene delivery of TRAIL to resistant cancer cells: A review

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), also known as APO2L, has emerged as a highly potential anticancer agent because of its capacity to effectively trigger apoptosis in tumor cells by specifically binding to either of its death receptors (DR4 or DR5) while having no adverse effects on normal cells. Nevertheless, its practical use has been hindered by its inefficient pharmacokinetics characteristics, the challenges involved in its administration and delivery to targeted cells, and the resistance exhibited by most cancer cells towards TRAIL. Gene therapy, as a promising approach would be able to potentially circumvent TRAIL-based cancer therapy challenges mainly through localized TRAIL expression and generating a bystander impact. Among different strategies, using nanoparticles in TRAIL gene delivery allows for precise targeting, and overcoming TRAIL resistance by combination therapy. In this review, we go over potential mechanisms by which cancer cells achieve resistance to TRAIL and provide an overview of different carriers for delivering of the TRAIL gene to resistant cancer cells, focusing on different types of nanoparticles utilized in this context. We will also explore the challenges, and investigate future perspectives of this nanomedicine approach for cancer therapy.

Phase II trial of vaccination with autologous, irradiated melanoma cells engineered by adenoviral mediated gene transfer to secrete granulocyte-macrophage colony stimulating factor in patients with stage III and IV melanoma

Background

In the era of immune checkpoint blockade, the role of cancer vaccines in immune priming has provided additional potential for therapeutic improvements. Prior studies have demonstrated delayed type hypersensitivity and anti-tumor immunity with vaccines engineered to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF). The safety, efficacy and anti-tumor immunity of GM-CSF secreting vaccine in patients with previously treated stage III or IV melanoma needs further investigation.

Methods

In this phase II trial, excised lymph node metastases were processed to single cells, transduced with an adenoviral vector encoding GM-CSF, irradiated, and cryopreserved. Individual vaccines were composed of 1x106, 4x106, or 1x107 tumor cells, and were injected intradermally and subcutaneously at weekly and biweekly intervals. The primary endpoints were feasibility of producing vaccine in stage III patients and determining the proportion of patients alive at two years in stage IV patients.

Results

GM-CSF vaccine was successfully developed and administered in all 61 patients. Toxicities were restricted to grade 1-2 local skin reactions. The median OS for stage III patients (n = 20) was 71.1 (95% CI, 43.7 to NR) months and 14.9 (95%CI, 12.1 to 39.7) months for stage IV patients. The median PFS in stage III patients was 50.7 (95%CI, 36.3 to NR) months and 4.1 (95% CI, 3.0-6.3) months in stage IV patients. In the overall population, the disease control rate was 39.3% (95%CI, 27.1 to 52.7%). In stage III patients, higher pre-treatment plasma cytokine levels of MMP-1, TRAIL, CXCL-11, CXCL-13 were associated with improved PFS (p<0.05 for all). An increase in post-vaccination levels of IL-15 and TRAIL for stage III patients was associated with improved PFS (p=0.03 for both). Similarly, an increase in post-vaccination IL-16 level for stage IV patients was associated with improved PFS (p=0.02) and clinical benefit.

Conclusions

Vaccination with autologous melanoma cells secreting GM-CSF augments antitumor immunity in stage III and IV patients with melanoma, is safe, and demonstrates disease control. Luminex data suggests that changes in inflammatory cytokines and immune cell infiltration promote tumor antigen presentation and subsequent tumor cell destruction. Additional investigation to administer this vaccine in combination with immune checkpoint inhibitors is needed.

TNF-Related Apoptosis-Inducing Ligand: Non-Apoptotic Signalling

TNF-related apoptosis-inducing ligand (TRAIL or Apo2 or TNFSF10) belongs to the TNF superfamily. When bound to its agonistic receptors, TRAIL can induce apoptosis in tumour cells, while sparing healthy cells. Over the last three decades, this tumour selectivity has prompted many studies aiming at evaluating the anti-tumoral potential of TRAIL or its derivatives. Although most of these attempts have failed, so far, novel formulations are still being evaluated. However, emerging evidence indicates that TRAIL can also trigger a non-canonical signal transduction pathway that is likely to be detrimental for its use in oncology. Likewise, an increasing number of studies suggest that in some circumstances TRAIL can induce, via Death receptor 5 (DR5), tumour cell motility, potentially leading to and contributing to tumour metastasis. While the pro-apoptotic signal transduction machinery of TRAIL is well known from a mechanistic point of view, that of the non-canonical pathway is less understood. In this study, we the current state of knowledge of TRAIL non-canonical signalling.

Mechanisms of resistance to immune checkpoint inhibitors in melanoma: What we have to overcome?

Marching into the second decade after the approval of ipilimumab, it is clear that immune checkpoint inhibitors (ICIs) have dramatically improved the prognosis of melanoma. Although the current edge is already high, with a 4-year OS% of 77.9% for adjuvant nivolumab and a 6.5-year OS% of 49% for nivolumab/ipilimumab combination in the metastatic setting, a high proportion of patients with advanced melanoma have no benefit from immunotherapy, or experience an early disease relapse/progression in the first few months of treatment, surviving much less. Reasonably, the primary and acquired resistance to ICIs has entered into the focus of clinical research with positive (e.g., nivolumab and relatlimab combination) and negative feedbacks (e.g., nivolumab with pegylated-IL2, pembrolizumab with T-VEC, nivolumab with epacadostat, and combinatorial triplets of BRAF/MEK inhibitors with immunotherapy). Many intrinsic (intracellular or intra-tumoral) but also extrinsic (systematic) events are considered to be involved in the development of this resistance to ICIs: i) melanoma cell immunogenicity (e.g., tumor mutational burden, antigen-processing machinery and immunogenic cell death, neoantigen affinity and heterogeneity, genomic instability, melanoma dedifferentiation and phenotypic plasticity), ii) immune cell trafficking, T-cell priming, and cell death evasion, iii) melanoma neovascularization, cellular TME components(e.g., T_regs, CAFs) and extracellular matrix modulation, iv) metabolic antagonism in the TME(highly glycolytic status, upregulated CD39/CD73/adenosine pathway, iDO-dependent tryptophan catabolism), v) T-cell exhaustion and negative immune checkpoints, and vi) gut microbiota. In the present overview, we discuss how these parameters compromise the efficacy of ICIs, with an emphasis on the lessons learned by the latest melanoma studies; and in parallel, we describe the main ongoing approaches to overcome the resistance to immunotherapy. Summarizing this information will improve the understanding of how these complicated dynamics contribute to immune escape and will help to develop more effective strategies on how anti-tumor immunity can surpass existing barriers of ICI-refractory melanoma.

TRAIL sensitivity of nasopharyngeal cancer cells involves redox dependent upregulation of TMTC2 and its interaction with membrane caspase-3

AIMS

Preferential expression of receptors for TNF-family related apoptosis inducing ligand (TRAIL), DR4 and DR5 makes TRAIL an attractive anti-cancer therapeutic. However, the efficacy of targeting death receptors has not been extensively studied in nasopharyngeal cancer (NPC). Here we investigated TRAIL sensitivity and its underlying mechanism in NPC cell lines, and assessed the potential of TRAIL as a therapeutic option against NPC.

RESULTS

Using two established NPC cell lines, we report the expression of DR4 and DR5, which respond to TRAIL ligation by triggering efficient Type II apoptosis. Mechanistically, early activation of caspase-3 and its membrane recruitment is identified in NPC cell lines, which is associated with, hitherto unreported, interaction with transmembrane and tetratricopeptide repeat containing 2 (TMTC2) in the lipid raft domains. TMTC2 expression is induced upon exposure to TRAIL and involves intracellular increase in peroxynitrite (ONOO-) production. While ONOO- increase is downstream of caspase-8 activation, it is involved in the upregulation of TMTC2, gene knockdown of which abrogated TRAIL-induced apoptotic execution. Bioinformatics analyses also provide evidence for a strong correlation between TMTC2 and DR4 or caspase-3 as well as a significantly better disease-free survival in patients with high TMTC2 expression.

INNOVATION AND CONCLUSION

Collectively, redox-dependent execution of NPC cells upon ligation of TRAIL receptors reintroduces the possible therapeutic use of TRAIL in NPC as well as underscores the potential of using TMTC2 as a biomarker of TRAIL sensitivity.

Crucial Role of Reactive Oxygen Species (ROS) for the Proapoptotic Effects of Indirubin Derivatives in Cutaneous SCC Cells

Efficient drugs are needed for countering the worldwide high incidence of cutaneous squamous cell carcinoma (cSCC) and actinic keratosis. Indirubin derivatives represent promising candidates, but their effects in cSCC cells have not been reported before. Here, we investigated the efficacy of three indirubin derivatives (DKP-071, -073 and -184) in four cSCC cell lines. High efficacy was seen in SCL-I, SCL-II, SCC-12 and SCC-13, resulting in up to 80% loss of cell proliferation, 60% loss of cell viability and 30% induced apoptosis (10 µM). Apoptosis was further enhanced in combinations with TNF-related apoptosis-inducing ligand (TRAIL). Induction of reactive oxygen species (ROS) appeared as critical for these effects. Thus, antioxidative pretreatment completely abolished apoptosis as well as restored cell proliferation and viability. Concerning the pathways, complete activation of caspases cascades (caspases-3, -4, -6, -7, -8 and -9), loss of mitochondrial membrane potential, activation of proapoptotic PKCδ (protein kinase C delta), inhibition of STAT3 (signal transducer and activator of transcription 3), downregulation of antiapoptotic XIAP (X-linked inhibitor of apoptosis protein) and survivin as well as upregulation of the proapoptotic Bcl-2 protein Puma and the cell cycle inhibitor p21 were obtained. Importantly, all activation steps were prevented by antioxidants, thus proving ROS as a master regulator of indirubins' antitumor effects. ROS induction presently develops as an important issue in anticancer therapy.

Silencing of Mcl-1 overcomes resistance of melanoma cells against TRAIL-armed oncolytic adenovirus by enhancement of apoptosis

Abstract

Arming of oncolytic viruses with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown as a viable approach to increase the antitumor efficacy in melanoma. However, melanoma cells may be partially or completely resistant to TRAIL or develop TRAIL resistance, thus counteracting the antitumor efficiency of TRAIL-armed oncolytic viruses. Recently, we found that TRAIL resistance in melanoma cells can be overcome by inhibition of antiapoptotic Bcl-2 protein myeloid cell leukemia 1 (Mcl-1). Here, we investigated whether the cytotoxicity of AdV-TRAIL, an oncolytic adenovirus, which expresses TRAIL after induction by doxycycline (Dox), can be improved in melanoma cells by silencing of Mcl-1. Two melanoma cell lines, the TRAIL-resistant MeWo and the TRAIL-sensitive Mel-HO were investigated. Treatment of both cell lines with AdV-TRAIL resulted in a decrease of cell viability, which was caused by an increase of apoptosis and necrosis. The proapoptotic effects were dependent on induction of TRAIL by Dox and were more pronounced in Mel-HO than in MeWo cells. SiRNA-mediated silencing of Mcl-1 resulted in a further significant decrease of cell viability and a further increase of apoptosis and necrosis in AdV-TRAIL-infected MeWo and Mel-HO cells. However, while in absolute terms, the effects were more pronounced in Mel-HO cells, in relative terms, they were stronger in MeWo cells. These results show that silencing of Mcl-1 represents a suitable approach to increase the cytotoxicity of a TRAIL-armed oncolytic adenovirus in melanoma cells.

Key messages

• Cytotoxicity of TRAIL-expressing adenovirus can be enhanced by silencing of Mcl-1.

• The effect occurs in TRAIL-sensitive and TRAIL-resistant melanoma cells.

• Increase of apoptosis is the main mechanism induced by Mcl-1 silencing.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-021-02081-3.

The Role of Exosomes Derived From Mesenchymal Stromal Cells in Dermatology

The skin is the largest organ of the human body and its main functions include providing protection from external harmful agents, regulating body temperature, and homeostatic maintenance. Skin injuries can damage this important barrier and its functions so research focuses on approaches to accelerate wound healing and treat inflammatory skin diseases. Due to their regenerative and immunomodulatory properties, mesenchymal stromal cells (MSCs) have been reported to play a significant role in skin repair and regeneration. However, it seems that the secretome of these cells and exosomes in particular may be responsible for their functions in skin regeneration and the immunomodulation field. The present review aims to gather the available information about the role of MSC-derived exosomes for both in vitro and in vivo models of different skin conditions and to highlight the need for further research in order to overcome any limitations for clinical translation.

The multifaceted role of TRAIL signaling in cancer and immunity

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can lead to the induction of apoptosis in tumor or infected cells. However, activation of TRAIL signaling may also trigger nonapoptotic pathways in cancer and in nontransformed cells, that is, immune cells. Here, we review the current knowledge on noncanonical TRAIL signaling. The biological outcomes of TRAIL signaling in immune and malignant cells are presented and explained, with a focus on the role of TRAIL for natural killer (NK) cell function. Furthermore, we highlight the technical difficulties in dissecting the precise molecular mechanisms involved in the switch between apoptotic and nonapoptotic TRAIL signaling. Finally, we discuss the consequences thereof for a therapeutic manipulation of TRAIL in cancer and possible approaches to bypass these difficulties.

Mcl-1 targeting strategies unlock the proapoptotic potential of TRAIL in melanoma cells

TNF-related apoptosis-inducing ligand (TRAIL) induces apoptosis selectively in cancer cells. For melanoma, the targeting of TRAIL signaling appears highly attractive, due to pronounced TRAIL receptor expression in tumor tissue. However, mechanisms of TRAIL resistance observed in melanoma cells may limit its clinical use. The Bcl-2 family members are critical regulators of cell-intrinsic apoptotic pathways. Thus, the antiapoptotic Bcl-2 protein myeloid cell leukemia 1 (Mcl-1) is overexpressed in many tumor types and was linked to chemotherapy resistance in melanoma. In this study, we evaluated the involvement of antiapoptotic Bcl-2 proteins (Bcl-2, Bcl-x_L , Bcl-w, Mcl-1, Bcl-A1, and Bcl-B) in TRAIL resistance. They were targeted by small interfering RNA-mediated silencing in TRAIL-sensitive (A-375, Mel-HO) and in TRAIL-resistant melanoma cell lines (Mel-2a, MeWo). This highlighted Mcl-1 as the most efficient target to overcome TRAIL resistance. In this context, we investigated the effects of Mcl-1-targeting microRNAs as well as the Mcl-1-selective inhibitor S63845. Both miR-193b and S63845 resulted in significant enhancement of TRAIL-induced apoptosis, associated with decreased cell viability. Apoptosis induction was mediated by caspase-3 processing as well as by Bax and Bak activation, indicating the critical involvement of intrinsic apoptosis pathways. These data may indicate a high relevance of Mcl-1 targeting also in melanoma therapy. Furthermore, the data may suggest to consider the use of the tumor suppressor miR-193b as a strategy for countering TRAIL resistance in melanoma.

Countering TRAIL Resistance in Melanoma

Melanoma of the skin has become a prime example for demonstrating the success of targeted cancer therapy. Nevertheless, high mortality has remained, mainly related to tumor heterogeneity and inducible therapy resistance. But the development of new therapeutic strategies and combinations has raised hope of finally defeating this deadly disease. TNF-related apoptosis-inducing ligand (TRAIL) represents a promising antitumor strategy. The principal sensitivity of melanoma cells for TRAIL was demonstrated in previous studies; however, inducible resistance appeared as a major problem. To address this issue, combination strategies were tested, and survival pathway inhibitors were shown to sensitize melanoma cells for TRAIL-induced apoptosis. Finally, cell cycle inhibition was identified as a common principle of TRAIL sensitization in melanoma cells. Mitochondrial apoptosis pathways, pro- and antiapoptotic Bcl-2 proteins as well as the rheostat consisted of Smac (Second mitochondria-derived activator of caspase) and XIAP (X-linked inhibitor of apoptosis protein) appeared to be of particular importance. Furthermore, the role of reactive oxygen species (ROS) was recognized in this setting. Inducible TRAIL resistance in melanoma can be explained by (i) high levels of antiapoptotic Bcl-2 proteins, (ii) high levels of XIAP, and (iii) suppressed Bax activity. These hurdles have to be overcome to enable the use of TRAIL in melanoma therapy. Several strategies appear as particularly promising, including new TRAIL receptor agonists, Smac and BH3 mimetics, as well as selective kinase inhibitors.

Crucial role of reactive oxygen species (ROS) for the proapoptotic effects of indirubin derivative DKP-073 in melanoma cells

Melanoma represents a prime example demonstrating the success of targeted therapy in cancer. Nevertheless, it remained a deadly disease until now, and the identification of new, independent strategies as well as the understanding of their molecular mechanisms may help to finally overcome the high mortality. Both indirubins and TNF-related apoptosis-inducing ligand (TRAIL) represent promising candidates. Here, the indirubin derivative DKP-073 is shown to trigger apoptosis in melanoma cells, which is enhanced by the combination with TRAIL and is accompanied by complete loss of cell viability. Addressing the signaling cascade, characteristic molecular steps were identified as caspase-3 activation, downregulation of XIAP, upregulation of p53 and TRAIL receptor 2, loss of mitochondrial membrane potential, and STAT-3 dephosphorylation. The decisive step, however, turned out to be the early production of ROS already at 1 h. This was proven by antioxidant pretreatment, which completely abolished apoptosis induction and loss of cell viability as well as abrogated all signaling effects listed above. Thus, ROS appeared as upstream of all proapoptotic signaling. The data indicate a dominant role of ROS in apoptosis regulation, and the new pathway may expose a possible Achilleś heel of melanoma.

Exosomes derived from TRAIL-engineered mesenchymal stem cells with effective anti-tumor activity in a mouse melanoma model

Exosomes are biological nano-sized vesicles (~30-200 nm in diameter) that are produced by a wide range of cells and play several roles in cell-cell communications. These vesicles contain membrane and cytoplasmic components of producing cells. Mesenchymal stem cells (MSCs) are the ideal producer of exosomes. The secreted vesicles from MSCs are promising biological vehicles for cell-free therapy in regenerative medicine, cancer therapy and targeted delivery of therapeutic agents to the tumor cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising member of the TNF family with selective effect on cancerous cells. Recent evidences showed that the membrane TRAIL-armed exosomes possess anti-tumor activity. However, the effect of in vivo administration of TRAIL-armed exosomes has not been reported so far. In the current study, mesenchymal stem cells expressing TRAIL/GFP proteins were prepared with the help of a non-viral vector based on polyethylenimine 25 kDa. Then, exosomes containing TRAIL protein (Exo-TRAIL) were isolated from the supernatant of genetically engineered MSCs and characterized. Antitumor activity of both MSC-derived exosomes and Exo-TRAIL was investigated in vitro and in vivo in three models. The results indicated that the co-injection of both Exo-TRAIL and tumor cells delayed the tumor appearance. Besides, the tumor volume/weight was efficiently decreased in tumor bearing mice. Moreover, it was shown that multi-dose injections of Exo-TRAIL reduced the tumor size while single dose treatment with Exo-TRAIL did not show significant anti-tumor activity. To conclude, these results suggested that MSC-derived Exo-TRAIL has a potential capacity for cancer treatment. [corrected].

Targeted Tumor Therapy Remixed-An Update on the Use of Small-Molecule Drugs in Combination Therapies

Over the last decade, the treatment of tumor patients has been revolutionized by the highly successful introduction of novel targeted therapies, in particular small-molecule kinase inhibitors and monoclonal antibodies, as well as by immunotherapies. Depending on the mutational status, BRAF and MEK inhibitor combinations or immune checkpoint inhibitors are current first-line treatments for metastatic melanoma. However, despite great improvements of survival rates limitations due to tumor heterogeneity, primary and acquired therapy resistance, immune evasion, and economical considerations will need to be overcome. Accordingly, ongoing clinical trials explore the individualized use of small-molecule drugs in new targeted therapy combinations based on patient parameters and tumor biopsies. With focus on melanoma therapy this review aims at providing a comprehensive overview of such novel alternative and combinational therapy strategies currently emerging from basic research. The molecular principles and drug classes that may hold promise for improved tumor therapy combination regimens including kinase inhibition, induction of apoptosis, DNA-damage response inhibition, epigenetic reprogramming, telomerase inhibition, redox modulation, metabolic reprogramming, proteasome inhibition, cancer stem cell transdifferentiation, immune cell signaling modulation, and others, are explained in brief. In addition, relevant targeted therapy combinations in current clinical trials and individualized treatment strategies are highlighted.

Antibody-Based Cancer Therapy: Successful Agents and Novel Approaches

Since their discovery, antibodies have been viewed as ideal candidates or "magic bullets" for use in targeted therapy in the fields of cancer, autoimmunity, and chronic inflammatory disorders. A wave of antibody-dedicated research followed, which resulted in the clinical approval of a first generation of monoclonal antibodies for cancer therapy such as rituximab (1997) and cetuximab (2004), and infliximab (2002) for the treatment of autoimmune diseases. More recently, the development of antibodies that prevent checkpoint-mediated inhibition of T cell responses invigorated the field of cancer immunotherapy. Such antibodies induced unprecedented long-term remissions in patients with advanced stage malignancies, most notably melanoma and lung cancer, that do not respond to conventional therapies. In this review, we will recapitulate the development of antibody-based therapy, and detail recent advances and new functions, particularly in the field of cancer immunotherapy. With the advent of recombinant DNA engineering, a number of rationally designed molecular formats of antibodies and antibody-derived agents have become available, and we will discuss various molecular formats including antibodies with improved effector functions, bispecific antibodies, antibody-drug conjugates, antibody-cytokine fusion proteins, and T cells genetically modified with chimeric antigen receptors. With these exciting advances, new antibody-based treatment options will likely enter clinical practice and pave the way toward more successful control of malignant diseases.

hvTRA, a novel TRAIL receptor agonist, induces apoptosis and sustained growth retardation in melanoma

In recent years, new treatment options for malignant melanoma patients have enhanced the overall survival for selected patients. Despite new hope, most melanoma patients still relapse with drug-resistant tumors or experience intrinsic resistance to the therapy. Therefore, novel treatment modalities beneficial for subgroups of patients are needed. TRAIL receptor agonists have been suggested as promising candidates for use in cancer treatment as they preferentially induce apoptosis in cancer cells. Unfortunately, the first generation of TRAIL receptor agonists showed poor clinical efficacy. hvTRA is a second-generation TRAIL receptor agonist with improved composition giving increased potency, and in the present study, we showed hvTRA-induced activation of apoptosis leading to an efficient and sustained reduction in melanoma cell growth in cell lines and xenograft models. Furthermore, the potential of hvTRA in a clinical setting was demonstrated by showing efficacy on tumor cells harvested from melanoma patients with lymph node metastasis in an ex vivo drug sensitivity assay. Inhibition of mutated BRAF has been shown to regulate proteins in the intrinsic apoptotic pathway, making the cells more susceptible for apoptosis induction. In an attempt to increase the efficacy of hvTRA, combination treatment with the mutated BRAF inhibitor vemurafenib was investigated. A synergistic effect by the combination was observed for several cell lines in vitro, and an initial cytotoxic effect was observed in vivo. Unfortunately, the initial increased reduction in tumor growth compared with hvTRA mono treatment was not sustained, and this was related to downregulation of the DR5 level by vemurafenib. Altogether, the presented data imply that hvTRA efficiently induce apoptosis and growth delay in melanoma models and patient material, and the potential of this TRAIL receptor agonist should be further evaluated for treatment of subgroups of melanoma patients.

Onto better TRAILs for cancer treatment

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of the TNF cytokine superfamily. By cross-linking TRAIL-Receptor (TRAIL-R) 1 or TRAIL-R2, also known as death receptors 4 and 5 (DR4 and DR5), TRAIL has the capability to induce apoptosis in a wide variety of tumor cells while sparing vital normal cells. The discovery of this unique property among TNF superfamily members laid the foundation for testing the clinical potential of TRAIL-R-targeting therapies in the cancer clinic. To date, two of these therapeutic strategies have been tested clinically: (i) recombinant human TRAIL and (ii) antibodies directed against TRAIL-R1 or TRAIL-R2. Unfortunately, however, these TRAIL-R agonists have basically failed as most human tumors are resistant to apoptosis induction by them. It recently emerged that this is largely due to the poor agonistic activity of these agents. Consequently, novel TRAIL-R-targeting agents with increased bioactivity are currently being developed with the aim of rendering TRAIL-based therapies more active. This review summarizes these second-generation novel formulations of TRAIL and other TRAIL-R agonists, which exhibit enhanced cytotoxic capacity toward cancer cells, thereby providing the potential of being more effective when applied clinically than first-generation TRAIL-R agonists.

Stem cell-based gene therapy activated using magnetic hyperthermia to enhance the treatment of cancer

Stem cell-based gene therapies, wherein stem cells are genetically engineered to express therapeutic molecules, have shown tremendous potential for cancer applications owing to their innate ability to home to tumors. However, traditional stem cell-based gene therapies are hampered by our current inability to control when the therapeutic genes are actually turned on, thereby resulting in detrimental side effects. Here, we report the novel application of magnetic core-shell nanoparticles for the dual purpose of delivering and activating a heat-inducible gene vector that encodes TNF-related apoptosis-inducing ligand (TRAIL) in adipose-derived mesenchymal stem cells (AD-MSCs). By combining the tumor tropism of the AD-MSCs with the spatiotemporal MCNP-based delivery and activation of TRAIL expression, this platform provides an attractive means with which to enhance our control over the activation of stem cell-based gene therapies. In particular, we found that these engineered AD-MSCs retained their innate ability to proliferate, differentiate, and, most importantly, home to tumors, making them ideal cellular carriers. Moreover, exposure of the engineered AD-MSCS to mild magnetic hyperthermia resulted in the selective expression of TRAIL from the engineered AD-MSCs and, as a result, induced significant ovarian cancer cell death in vitro and in vivo.

Expression of tumor necrosis factor-related apoptosis-inducing ligand death receptors DR4 and DR5 in human nonmelanoma skin cancer

Death receptors 4 and 5 (DR4 and DR5) are cell surface receptors that when activated by their ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) triggers apoptosis in most cancer cells but not in normal cells. Currently, it remains unclear whether DR4 and DR5 are involved in immune surveillance against nonmelanoma skin cancer (NMSC) progression. The aim of this study was to investigate the expression of DR4 and DR5 in NMSC and relate the results to the established clinicopathologic prognostic factors. This study was conducted on about 80 skin specimens from patients with NMSC (40 basal cell carcinoma and 40 squamous cell carcinoma) and diagnosed and confirmed by biopsy. Immunohistochemical analysis for DR4 and DR5 was carried out on formalin-fixed paraffin-embedded sections of skin tissues using avidin-biotin peroxidase method. Significant expression of both DR4 and DR5 was observed in NMSC cases. There was statistically significant association between DR4 and DR5 expression in squamous cell carcinoma and each of tumor site and lymph node metastasis. There was statistically significant association between DR4 expression in basal cell carcinoma and histopathologic subtypes (high expression in nodular type) and between DR5 expression and tumor site (high expression in sun-exposed area). In conclusion, expression of TRAIL receptors that mediate extrinsic apoptotic pathway in NMSC may be suggestive of a reassessment of the suitability of TRAIL-based strategy in future NMSC therapies.

Liposome-bound TRAIL induces superior DR5 clustering and enhanced DISC recruitment in histiocytic lymphoma U937 cells

Human Apo2-Ligand/TRAIL is a promising antitumor agent. Our group demonstrated that TRAIL was physiologically released to the extracellular medium inserted in lipid vesicles, known as exosomes. Recently we demonstrated that artificial lipid nanoparticles coated with bioactive TRAIL (LUV-TRAIL), which resemble the natural exosomes, greatly improved TRAIL activity compared with the soluble form of this death ligand and were able to induce apoptosis in hematological malignancies. In this study we have deepened the underlying mechanism of action of LUV-TRAIL in hematologic cells. Using histiocytic lymphoma U937 cells, we demonstrated that TRAIL signaling almost exclusively depends on DR5 despite these cells expressing high amounts of DR4, and proved that LUV-TRAIL's higher pro-apoptotic effect relies on its superior ability to induce DR5 clustering on cell surface, therefore enhancing DISC recruitment and triggering caspase activation more efficiently than the soluble form of TRAIL.

TRAIL-based tumor sensitizing galactoxyloglucan, a novel entity for targeting apoptotic machinery

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an attractive target for cancer therapy due to its ability to selectively induce apoptosis in cancer cells, without causing significant toxicity in normal tissues. We previously reported that galactoxyloglucan (PST001) possesses significant antitumor and immunomodulatory properties. However, the exact mechanism in mediating this anticancer effect is unknown. This study, for the first time, indicated that PST001 sensitizes non-small cell lung cancer (A549) and nasopharyngeal (KB) cells to TRAIL-mediated apoptosis. In vitro studies suggested that PST001 induced apoptosis primarily via death receptors and predominantly activated caspases belonging to the extrinsic apoptotic cascade. Microarray profiling of PST001 treated A549 and KB cells showed the suppression of survivin (BIRC5) and anti-apoptotic Bcl-2, as well as increased cytochrome C. TaqMan low density array analysis of A549 cells also confirmed that the induction of apoptosis by the polysaccharide occurred through the TRAIL-DR4/DR5 pathways. This was finally confirmed by in silico analysis, which revealed that PST001 binds to TRAIL-DR4/DR5 complexes more strongly than TNF and Fas ligand-receptor complexes. In summary, our results suggest the potential of PST001 to be developed as an anticancer agent that not only preserves innate biological activity of TRAIL, but also sensitizes cancer cells to TRAIL-mediated apoptosis.

Sensitization of melanoma cells for TRAIL-induced apoptosis by activation of mitochondrial pathways via Bax

The death ligand TRAIL (TNF-related apoptosis-inducing ligand) represents a promising therapeutic strategy for metastatic melanoma, however prevalent and inducible resistance limits its applicability and therapeutic use. Recent work has revealed that combinations with survival pathway inhibitors could efficiently sensitize melanoma cells for TRAIL. Here, a particular role was attributed to the activation of Bax, which is regulated by phosphorylation. Thus, TRAIL resistance in melanoma is explained by three major steps, namely high levels of antiapoptotic Bcl-2 proteins, high levels of inhibitor of apoptosis proteins (cIAPs) and suppressed Bax activity. Importantly, Bid was activated in response to TRAIL alone also in resistant cells to antagonize Bcl-2, and Bax was activated in response to pathway inhibitors. However, only in combinations, mitochondrial apoptosis pathways were opened to result in release of Smac/DIABLO, which functions as antagonist of cIAPs. Opening the caspase cascade by Smac then allowed efficient induction of apoptosis. Thus, direct or indirect targeting of Bax represents a suitable strategy to overcome TRAIL resistance in melanoma and may allow the establishment of TRAIL-based therapeutic approaches.

Visible light is a better co-inducer of apoptosis for curcumin-treated human melanoma cells than UVA

Curcumin attracts worldwide scientific interest due to its anti-proliferative and apoptosis inducing effects on different tumor cells at concentrations ranging from 10 to 150 µM (3.7-55 µg/ml). Unfortunately, because of a low oral bioavailability, only low and pharmacologically ineffective serum levels are achievable. In this study, an alternative treatment concept consisting of low concentration curcumin (0.2-5 µg/ml) and irradiation with UVA or visible light (VL) has been tested. The experimental results show clearly that this treatment decreases the proliferation and the viability of human melanoma cells while the cell membrane integrity remains intact. We identified the onset of apoptosis characterized by typical markers such as active caspases 8, 9 and 3 as well as DNA fragmentation accompanied by the loss of cell adhesion. The mitochondrial apoptosis signaling pathway is predominant due to an early activation of caspase-9. The present data indicate a higher efficacy of a combination of curcumin and VL than curcumin and UVA. Reduced effects as a result of light absorption by heavily pigmented skin are unlikely if VL is used. These results indicate that a combination of curcumin and light irradiation may be a useful additional therapy in the treatment of malignant disease.

ROS-dependent phosphorylation of Bax by wortmannin sensitizes melanoma cells for TRAIL-induced apoptosis

The pathways of reactive oxygen species (ROS)-mediated apoptosis induction, of Bax activation and the sensitization of tumor cells for TRAIL (TNF-related apoptosis-inducing ligand)-induced apoptosis are still largely elusive. Here, sensitization of melanoma cells for TRAIL by the PI3-kinase inhibitor wortmannin correlated to the activation of mitochondrial apoptosis pathways. Apoptosis was dependent on Bax and abrogated by Bcl-2 overexpression. The synergistic enhancement was explained by Bax activation through wortmannin, which tightly correlated to the characteristic Bax phosphorylation patterns. Thus, wortmannin resulted in early reduction of the Bax-inactivating phosphorylation at serine-184, whereas the Bax-activating phosphorylation at threonine-167 was enhanced. Proving the responsibility of the pathway, comparable effects were obtained with an Akt inhibitor (MK-2206); while suppressed phosphorylation of serine-184 may be attributed to reduced Akt activity itself, the causes of enhanced threonine-167 phosphorylation were addressed here. Characteristically, production of ROS was seen early in response to wortmannin and MK-2206. Providing the link between ROS and Bax, we show that abrogated ROS production by α-tocopherol or by NADPH oxidase 4 (NOX4) siRNA suppressed apoptosis and Bax activation. This correlated with reduced Bax phosphorylation at threonine-167. The data unraveled a mechanism by which NOX4-dependent ROS production controls apoptosis via Bax phosphorylation. The pathway may be considered for proapoptotic, anticancer strategies.

RAF inhibition overcomes resistance to TRAIL-induced apoptosis in melanoma cells

Mutated BRAF represents a critical oncogene in melanoma, and selective inhibitors have been approved for melanoma therapy. However, the molecular consequences of RAF inhibition in melanoma cells remained largely elusive. Here, we investigated the effects of the pan-RAF inhibitor L-779,450, which inhibited cell proliferation both in BRAF-mutated and wild-type melanoma cell lines. It furthermore enhanced apoptosis in combination with the death ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and overcame TRAIL resistance in melanoma cells. Enhanced apoptosis coincided with activation of mitochondrial pathways, seen by loss of mitochondrial membrane potential and release of cytochrome c, Smac (second mitochondria-derived activator of caspases), and apoptosis-inducing factor (AIF). Subsequently, caspase-9 and -3 were activated. Apoptosis induction by L-779,450/TRAIL was prevented by Bcl-2 overexpression and was dependent on Bax. Thus, activation of Bax by L-779,450 alone was demonstrated by Bax conformational changes, whereas Bak was not activated. Furthermore, the BH3-only protein Bim was upregulated in response to L-779,450. The significant roles of Smac, Bax, and Bim in this setting were proven by small interfering RNA (siRNA)-mediated knockdown experiments. L-779,450 also resulted in morphological changes indicating autophagy confirmed by the autophagy marker light chain 3-II (LC3-II). The pro-apoptotic effects of L-779,450 may explain the antitumor effects of RAF inhibition and may be considered when evaluating RAF inhibitors for melanoma therapy.

Death receptors as targets in cancer

Anti-tumour therapies based on the use pro-apoptotic receptor agonists, including TNF-related apoptosis-inducing ligand (TRAIL) or monoclonal antibodies targeting TRAIL-R1 or TRAIL-R2, have been disappointing so far, despite clear evidence of clinical activity and lack of adverse events for the vast majority of these compounds, whether combined or not with conventional or targeted anti-cancer therapies. This brief review aims at discussing the possible reasons for the lack of apparent success of these therapeutic approaches and at providing hints in order to rationally design optimal protocols based on our current understanding of TRAIL signalling regulation or resistance for future clinical trials.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

Sensitization of melanoma cells for TRAIL-induced apoptosis by BMS-345541 correlates with altered phosphorylation and activation of Bax

Resistance to TRAIL (TNF-related apoptosis-inducing ligand)- induced apoptosis limits its therapeutic use. Different strategies of TRAIL sensitization and a dependency on Bax have been reported, but common principles of TRAIL resistance and the way of Bax activation remained poorly understood. Applying a melanoma model of TRAIL-sensitive and -resistant cell lines, efficient sensitization for TRAIL-induced apoptosis is demonstrated by the kinase inhibitor BMS-345541 (N-(1,8-dimethylimidazo(1,2-a)quinoxalin-4-yl)-1,2-ethanediamine hydrochloride), which targets IκB (inhibitor of κB proteins) kinase β (IKKβ). This effect was completely abrogated by Bax knockout as well as by Bcl-2 overexpression, in accordance with a Bax dependency. Early loss of the mitochondrial membrane potential, release of cytochrome c and Smac (second mitochondria-derived activator of caspases) clearly indicated the activation of mitochondrial apoptosis pathways. Of note, BMS-345541 alone resulted in an early Bax activation, seen by conformational changes and by Bax translocation. The synergistic effects can be explained by Bid activation through TRAIL, which inhibits Bcl-2, and the activation of Bax through BMS-345541. The critical roles of XIAP (X-chromosome-linked inhibitor of apoptosis protein), Smac and Bid were clearly proven by overexpression and siRNA knockdown, respectively. The way of Bax activation by BMS-345541 was unraveled by establishing new assays for Bax activation. These showed reduction of the inactivating Bax phosphorylation at serine-184, while the activating Bax phosphorylation at threonine-167 was enhanced. Thus, modulation of Bax phosphorylation appeared as tightly related to TRAIL sensitivity/resistance in melanoma cells, and therapeutic strategies may be considered.

General Sensitization of melanoma cells for TRAIL-induced apoptosis by the potassium channel inhibitor TRAM-34 depends on release of SMAC

The death ligand TRAIL represents a promising therapeutic strategy for metastatic melanoma, however prevalent and inducible resistance limit its applicability. A new approach is presented here for sensitization to TRAIL. It is based on inhibition of the membrane potassium channel KCa3.1 (IK1), which serves fundamental cellular functions related to membrane potential. The selective inhibitor TRAM-34 did not induce apoptosis by itself but synergistically enhanced TRAIL sensitivity and overrode TRAIL resistance in a large panel of melanoma cell lines. Expression of IK1 was also found in mitochondria, and its inhibition resulted in mitochondrial membrane hyperpolarization and an early activation of Bax. The combination of TRAM-34 and TRAIL resulted in massive release of mitochondrial factors, cytochrome c, AIF and SMAC/DIABLO. Bax knockdown and Bcl-2 overexpression abolished apoptosis. Overexpression of XIAP diminished apoptosis by two-fold, and SMAC knockdown almost completely abolished apoptosis. These data uncover the existence of a rheostat in melanoma cells, consisting of inhibitor of apoptosis proteins and SMAC, which regulates TRAIL sensitivity. Thus, a new strategy is described based on mitochondrial membrane channels, which correspond to Bax activation. As both TRAIL and IK1 inhibitors had shown only minor side effects in clinical trials, a clinical application of this combination is conceivable.

Efficient melanoma cell killing and reduced melanoma growth in mice by a selective replicating adenovirus armed with tumor necrosis factor-related apoptosis-inducing ligand

High mortality and therapy resistance of melanoma demand the development of new strategies, and overcoming apoptosis deficiency appears as particularly promising. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has shown high potential for apoptosis induction in melanoma cells and may be applicable for gene therapy because of its selective impact on tumor cells. We have constructed a conditional replication-competent adenoviral vector with TRAIL controlled by a tetracycline-inducible promoter (AdV-TRAIL). A variant E1A protein and the lack of E1B aimed at the restriction of viral replication to tumor cells. In particular, the replication gene E1A is controlled by a tyrosinase promoter with high selectivity for melanoma cells. AdV-TRAIL mediated strong expression of E1A and doxycycline-dependent induction of TRAIL selectively in melanoma cells, which resulted in tumor cell lysis and induction of apoptosis. In contrast, non-melanoma cells and normal human melanocytes appeared to be protected. Comparison of the AdV-TRAIL approach with a comparable CD95L vector revealed similar efficacy in vitro. In mouse xenotransplantation models, AdV-TRAIL demonstrated its activity by significant melanoma growth reduction. Melanoma cell killing by AdV-TRAIL was further improved in vitro by combinations with chemotherapeutics. We demonstrate that melanoma cells may be efficiently targeted by TRAIL-based gene therapy, and resistance may be overcome by combined chemotherapy.

Melanoma-associated Chondroitin Sulfate Proteoglycan (MCSP)-targeted delivery of soluble TRAIL potently inhibits melanoma outgrowth in vitro and in vivo

BACKGROUND

Advanced melanoma is characterized by a pronounced resistance to therapy leading to a limited patient survival of ~6 - 9 months. Here, we report on a novel bifunctional therapeutic fusion protein, designated anti-MCSP:TRAIL, that is comprised of a melanoma-associated chondroitin sulfate proteoglycan (MCSP)-specific antibody fragment (scFv) fused to soluble human TRAIL. MCSP is a well-established target for melanoma immunotherapy and has recently been shown to provide important tumorigenic signals to melanoma cells. TRAIL is a highly promising tumoricidal cytokine with no or minimal toxicity towards normal cells. Anti-MCSP:TRAIL was designed to 1. selectively accrete at the cell surface of MCSP-positive melanoma cells and inhibit MCSP tumorigenic signaling and 2. activate apoptotic TRAIL-signaling.

RESULTS

Treatment of a panel of MCSP-positive melanoma cell lines with anti-MCSP:TRAIL induced TRAIL-mediated apoptotic cell death within 16 h. Of note, treatment with anti-MCSP:sTRAIL was also characterized by a rapid dephosphorylation of key proteins, such as FAK, implicated in MCSP-mediated malignant behavior. Importantly, anti-MCSP:TRAIL treatment already inhibited anchorage-independent growth by 50% at low picomolar concentrations, whereas > 100 fold higher concentrations of non-targeted TRAIL failed to reduce colony formation. Daily i.v. treatment with a low dose of anti-MCSP:TRAIL (0.14 mg/kg) resulted in a significant growth retardation of established A375 M xenografts. Anti-MCSP:TRAIL activity was further synergized by co-treatment with rimcazole, a σ-ligand currently in clinical trials for the treatment of various cancers.

CONCLUSIONS

Anti-MCSP:TRAIL has promising pre-clinical anti-melanoma activity that appears to result from combined inhibition of tumorigenic MCSP-signaling and concordant activation of TRAIL-apoptotic signaling. Anti-MCSP:TRAIL alone, or in combination with rimcazole, may be of potential value for the treatment of malignant melanoma.

Anti-apoptotic role of HIF-1 and AP-1 in paclitaxel exposed breast cancer cells under hypoxia

Background

Hypoxia is a hallmark of solid tumors and is associated with metastases, therapeutic resistance and poor patient survival.

Results

In this study, we showed that hypoxia protected MDA-MB-231 breast cancer cells against paclitaxel- but not epirubicin-induced apoptosis. The possible implication of HIF-1 and AP-1 in the hypoxia-induced anti-apoptotic pathway was investigated by the use of specific siRNA. Specific inhibition of the expression of these two transcription factors was shown to increase apoptosis induced by chemotherapeutic agents under hypoxia indicating an involvement of HIF-1 and AP-1 in the anti-apoptotic effect of hypoxia. After HIF-1 specific inhibition and using TaqMan Human Apoptosis Array, 8 potential HIF-1 target genes were identified which could take part in this protection. Furthermore, Mcl-1 was shown to be a potential AP-1 target gene which could also participate to the hypoxia-induced chemoresistance.

Conclusions

Altogether, these data highlight two mechanisms by which hypoxia could mediate its protective role via the activation of two transcription factors and, consecutively, changes in gene expression encoding different anti- and pro-apoptotic proteins.

Novel SMAC-mimetics synergistically stimulate melanoma cell death in combination with TRAIL and Bortezomib

BACKGROUND

XIAP (X-linked inhibitor of apoptosis protein) is an anti-apoptotic protein exerting its activity by binding and suppressing caspases. As XIAP is overexpressed in several tumours, in which it apparently contributes to chemoresistance, and because its activity in vivo is antagonised by second mitochondria-derived activator of caspase (SMAC)/direct inhibitor of apoptosis-binding protein with low pI, small molecules mimicking SMAC (so called SMAC-mimetics) can potentially overcome tumour resistance by promoting apoptosis.

METHODS

Three homodimeric compounds were synthesised tethering a monomeric SMAC-mimetic with different linkers and their affinity binding for the baculoviral inhibitor repeats domains of XIAP measured by fluorescent polarisation assay. The apoptotic activity of these molecules, alone or in combination with tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and/or Bortezomib, was tested in melanoma cell lines by MTT viability assays and western blot analysis of activated caspases.

RESULTS

We show that in melanoma cell lines, which are typically resistant to chemotherapeutic agents, XIAP knock-down sensitises cells to TRAIL treatment in vitro, also favouring the accumulation of cleaved caspase-8. We also describe a new series of 4-substituted azabicyclo[5.3.0]alkane monomeric and dimeric SMAC-mimetics that target various members of the IAP family and powerfully synergise at submicromolar concentrations with TRAIL in inducing cell death. Finally, we show that the simultaneous administration of newly developed SMAC-mimetics with Bortezomib potently triggers apoptosis in a melanoma cell line resistant to the combined effect of SMAC-mimetics and TRAIL.

CONCLUSION

Hence, the newly developed SMAC-mimetics effectively synergise with TRAIL and Bortezomib in inducing cell death. These findings warrant further preclinical studies in vivo to verify the anticancer effectiveness of the combination of these agents.

Enhanced death ligand-induced apoptosis in cutaneous SCC cells by treatment with diclofenac/hyaluronic acid correlates with downregulation of c-FLIP

Actinic keratosis (AK) occurs on sun-exposed skin and may progress to invasive squamous cell carcinoma (SCC). As for its topical treatment, diclofenac/hyaluronic acid (HA) has been recently approved. The NSAID diclofenac is an inhibitor of COX-2; however, its mode of action in cutaneous epithelial cancer cells is largely unknown. Here, the effects of diclofenac/HA were investigated in relation to death ligand-mediated apoptosis (TNF-alpha, TRAIL, and CD95 activation). Whereas diclofenac/HA only moderately induced apoptosis by itself, it resulted in pronounced enhancement of death ligand-mediated apoptosis in sensitive SCC cell lines (3/4). Apoptosis was associated with activation of initiator caspases of the extrinsic pathway (caspase-8/caspase-10). Furthermore, death ligand and diclofenac/HA-mediated apoptosis were blocked by the same caspase inhibitors, indicating related pathways. The proapoptotic effects of diclofenac/HA appeared independent of the p53 pathway. Also, upregulation of death receptors appeared less important; however, strong downregulation of c-FLIP isoforms was seen after diclofenac/HA treatment. The crucial role of c-FLIP was proven through overexpression and knockdown experiments. Thus, induction of apoptosis appears to be highly characteristic of the mode of action of diclofenac/HA, and the therapeutic effect may be related to sensitization of neoplastic keratinocytes for death ligand-induced apoptosis.

EGCG enhances TRAIL-mediated apoptosis in human melanoma A375 cell line

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anti-cancer agent. Epigallocatechin-3-gallate (EGCG) is a polyphenolic constituent of green tea. In this study, inhibitory effect of combined use of EGCG and TRAIL on human melanoma A375 cells was examined and the possible mechanism investigated. The cells were divided into 4 groups: control group, EGCG group (EGCG: 10, 20 mug/mL), TRAIL group (TRAIL: 25 ng/mL) and EGCG+TRAIL group (combined group). The growth inhibition was measured in the A375 cells treated with different concentrations of TRAIL ((25, 50, 75, 100, 125, 150 ng/mL) by MTT assay. The apoptosis was assessed by flow cytometry. The expressions of DR4 and DR5 were detected by flow cytometry and western blotting. The activities of caspase-8 and caspase-3 were determined by colorimetric assay. The results showed that TRAIL could dose-dependently inhibit the growth of A375 cells and the IC(50) of TRAIL was 150 ng/mL. The apoptosis rate was 11.8% in the TRAIL group, 5%-7% in the EGCG group and 48.9%-59.1% in the combined group. Significant difference was found in the apoptosis rate between the combined group and the EGCG or TRAIL group (P<0.05 for each). The expression of DR4 instead of DR5 was significantly increased in the EGCG group. The activity of caspase-3 rather than caspase-8 was substantially enhanced in the EGCG group. These results suggest that EGCG is useful for the TRAIL-based treatment for melanoma.

Bitumen products induce skin cell apoptosis in chronically exposed road pavers

BACKGROUND

Worker's exposure to bitumen fumes, via inhalation and skin contamination, is related to adverse effects including an increased risk of lung, stomach and non-melanoma skin cancers and leukaemia. The two major mechanisms regulating apoptosis include the mitochondria-mediated intrinsic pathway and the extrinsic pathway induced by death signalling ligands. In a previous study, we showed activation of apoptosis-regulating proteins BAX and BCL-2 in road pavers chronically exposed to bitumen fumes. These molecules play a central role in activation of programmed cell death by the intrinsic pathway. In this study, we hypothesized that the apoptosis mechanism could be activated in the skin of road pavers chronically exposed to bitumen fumes also through the extrinsic pathway, via mediation by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its death receptor, DR5.

METHODS

Skin punch biopsies from 16 occupationally exposed workers and a control group were processed immunohistochemically for TRAIL and DR5. Activation of programmed cell death was also investigated by expression of caspase-3 and visualization of DNA strand breaks.

RESULTS AND CONCLUSION

TRAIL, DR5 and caspase-3 overexpression and enhanced Terminal Deoxynucleotidyl Transferase Mediated dUTP Nick End Labeling (TUNEL) positivity were found in chronically bitumen-exposed skin, suggesting activation of apoptosis as a defence mechanism.

2-methoxyestradiol mediates apoptosis through caspase-dependent and independent mechanisms in ovarian cancer cells but not in normal counterparts

OBJECTIVE

The estrogen metabolite 2-methoxyestradiol has shown antitumorigenic action in some epithelial tumors. In the present work we investigate its effects in ovarian cancer used alone or in combination with other apoptotic-inducing reagents such as tumor necrosis factor-related apoptosis-inducing ligand.

METHODS

To assess the effect of 2-methoxyestradiol, dose response and time courses in ovarian cancer and normal cells were conducted. Apoptosis was confirmed through DNA laddering, by flow cytometry, and Western blotting of proteins involved in the apoptotic cascade.

RESULTS

2-Methoxyestradiol induced apoptosis in ovarian cancer cells but not in normal counterparts. 2-Methoxyestradiol activates both the intrinsic and extrinsic apoptotic pathways. 2-Methoxyestradiol-mediated apoptosis involves reactive oxygen species generation and caspase-dependent and caspase-independent mechanisms. We also demonstrate that 2-methoxyestradiol selectively induces an additive/synergistic apoptotic response in ovarian cancer cells when used in combination with tumor necrosis factor-related apoptosis-inducing ligand.

CONCLUSIONS

2-Methoxyestradiol, alone or in combination with tumor necrosis factor-related apoptosis-inducing ligand, should be considered as a potential treatment for ovarian cancer.

Expression and function of bcl-2 proteins in melanoma

Bcl-2 proteins are critical regulators of mitochondrial membrane permeability and the proapoptotic mitochondrial pathway. The family encloses pro- and antiapoptotic factors encoded by over 15 genes, which frequently give rise to alternative splice products. Antiapoptotic, proapoptotic multidomain, and proapoptotic BH3-only proteins are characterized by the presence of at least one of four Bcl-2 homology domains (BH 1-4). Their expression and activities are controlled by survival pathways as MAP kinases and protein kinase B/Akt, which are in touch with a number of transcription factors. In melanoma, the mitochondrial apoptosis pathways and Bcl-2 proteins appear of particular importance for apoptosis resistance, which has been addressed in clinical trials applying antisense-Bcl-2. Overexpression or induction of proapoptotic Bcl-2 proteins as well as the use of small molecule mimetics for the proapoptotic BH3 domain are further promising strategies.

Apoptosis pathways and oncolytic adenoviral vectors: promising targets and tools to overcome therapy resistance of malignant melanoma

In the last decades melanoma incidence has been increasing worldwide, while mortality remained on a high level. Until now, there is no suitable therapy for metastasized melanoma, which could lead to a significant increase in overall survival. Apoptosis deficiency is supposed to be a critical factor for therapy resistance, and previous work has characterized the basic mechanisms of apoptosis regulation in melanoma. Genes and strategies suitable for efficient induction of apoptosis in melanoma cells were identified, which are based on proapoptotic Bcl-2 proteins (Bcl-x(S), Bcl-x(AK), Bik/Nbk and Bax) as well as on tumor necrosis factor (TNF)-related death ligands (CD95L/Fas ligand and TNF-related apoptosis-inducing ligand, TRAIL). Proapoptotic genes may be employed in improved gene therapeutic strategies, based on conditional oncolytic adenoviral vectors.

Melanocyte receptors: clinical implications and therapeutic relevance

The activation or the inhibition of melanocyte-specific receptors offers novel means of augmenting normal melanocyte function, skin color, and photoprotection, or treating melanocytic disorders, namely at this time, metastatic melanoma. Melanocyte-specific receptors include melanocortin-1 (MCR1) and melatonin receptors. Other receptors that play an important role in melanoma progression are G-protein couple receptors such as Frizzled 5 and receptor tyrosine kinases such as c-Kit and hepatocyte growth factor (HGF) receptor. These receptors activate two crucial cell-signaling pathways, RAS/RAF/MEK/ERK and PI3K/AKT, integral to melanoma cell survival, and can serve as targets for therapy of disseminated melanoma. Activation of death receptors is another pathway that can be exploited with targeted therapeutics to control advanced melanoma. This article reviews the current understanding of melanocyte receptors, their agonists and inhibitors, and their potential to treat the melanocytic pathology.