Death receptors and melanoma resistance to apoptosis

Screening of anti-melanoma compounds from Morus alba L.: Sanggenon C promotes melanoma cell apoptosis by disrupting intracellular Ca2+ homeostasis

ETHNOPHARMACOLOGICAL RELEVANCE

Morus alba L. is a widespread plant that has long been considered to have remarkable medical values, including anti-inflammation in Traditional Chinese Medicine (TCM). The components of Morus Alba L. constituents have been extensively studied and have been shown to have high prospects for cancer therapy. However, limited investigations have been done on the bioactive compounds in Morus alba L.

AIM OF THE STUDY

This study aimed to systematically examine the anticancer properties of 28 commercially available compounds from Morus alba L. against melanoma cells in vitro. Additionally, the anticancer mechanisms of the bioactive compound exhibiting the most significant potential were further studied.

MATERIALS AND METHODS

The anti-proliferative effects of Morus alba L.-derived compounds on melanoma cells were determined by colony formation assays. Their effects on cell viability and apoptosis were determined using the CCK8 assay and flow cytometry, respectively. The binding affinity of identified Morus alba L. compounds with anticancer activities towards melanoma targets was analyzed via molecular docking. The molecular mechanism of Sanggenon C was explored using soft agar assays, EdU incorporation assays, flow cytometry, western blotting, transcriptome analysis, and xenograft assays.

RESULTS

Based on colony formation assays, 11 compounds at 20 μM significantly inhibited colony growth on a panel of melanoma cells. These compounds displayed IC50 values (half maximal inhibitory concentrations) ranging from 5 μM to 30 μM. Importantly, six compounds were identified as novel anti-melanoma agents, including Sanggenon C, 3'-Geranyl-3-prenyl-2',4',5,7-tetrahydroxyflavone, Moracin P, Moracin O, Kuwanon A, and Kuwanon E. Among them, Sanggenon C showed the most potent effects, with an IC50 of about 5 μM, significantly reducing proliferation and inducing apoptosis in melanoma cells. Based on the xenograft model assay, Sanggenon C significantly inhibited melanoma cell proliferation in vivo. Sanggenon C triggered ER stress in a dose-dependent manner, which further disrupted cellular calcium ion (Ca2+) homeostasis. The Ca2+ chelator BAPTA partially restored cell apoptosis induced by Sanggenon C, confirming that Ca2+ signaling contributed to the anticancer activity of Sanggenon C against melanoma.

CONCLUSIONS

In our study, 11 compounds demonstrated anti-melanoma properties. Notably, Sanggenon C was found to promote apoptosis by disrupting the intracellular calcium homeostasis in melanoma cells. This study provides valuable information for the future development of novel cancer therapeutic agents from Morus alba L.

PhotoPyro-Induced cGAS-STING Pathway Activation Enhanced Anti-Melanoma Immunotherapy via a Manganese-Coordinated Nanomedicine

Malignant melanoma is an aggressive skin cancer with a high metastatic and mortality rate. Owing to genetic alterations, melanoma cells are resistant to apoptosis induction, which reduces the efficacy of most adjuvant systemic anticancer treatments in clinical. Here, a noninvasive strategy for anti-melanoma immunotherapy based on a manganese-coordinated nanomedicine is provided. Supplemented with photoirradiation, photon-mediated reactive oxygen species generation by photosensitizer chlorin e6 initiates photon-controlled pyroptosis activation (PhotoPyro) and promotes antitumor immunity. Simultaneously, photoirradiation-triggered double-stranded DNA generation in the cytosol would activate the Mn2+ -sensitized cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, which further augment the PhotoPyro-induced immune response. The syngeneic effect of these immunostimulatory pathways significantly benefits dendritic cell maturation by damage-associated molecular patterns and proinflammatory cytokines secretion, thereby activating T cells and remarkably eliciting a systemic antitumor immune response to inhibiting both primary and distant tumor growth. Collaboratively, the photoirradiation-triggered PhotoPyro and cGAS-STING pathway activation by nanomedicine administration could enhance the antitumor capacity of immunotherapy and serve as a promising strategy for melanoma treatment.

CD95 promotes stemness of colorectal cancer cells by lncRNA MALAT1

Colorectal cancer (CRC) is the second most fatal cancer. Many studies have shown that cancer stemness contributes to resistance to conventional chemotherapy and poor prognosis. However, the mechanisms involved in maintaining cancer stemness in CRC are still obscure and few clinical drugs were used to target cancer stemness. Previous studies had reported CD95 increases the stemness of cancer cells with long-term stimulation of exogenous agonist CD95 ligand (CD95L). However, the expression of CD95L is relative low in certain human tumor tissues. In this study, we found that CD95 was highly expressed in CRC cells, and in vitro it promoted the tumorsphere formation, chemotherapy resistance and in vivo tumor growth without stimulation of exogenous CD95L. Mechanistically, the bulk and single-cell RNA-sequencing results suggested that CD95 promotes stemness of CRC cells through upregulation of long non-coding RNAs metastasis-associated lung adenocarcinoma transcript 1 (lncRNA MALAT1). MALAT1 knockdown inhibited CD95-induced tumorsphere formation and chemotherapy resistance. In summary, our findings reveal that CD95 has the capability to modulate cancer stemness via the action of the lncRNA MALAT1. Targeting CD95 may be a promising strategy to inhibit cancer stemness in CRC.

Antimelanoma effect of manool in 2D cell cultures and reconstructed human skin models

Melanoma is the most aggressive and lethal type of skin cancer, characterized by therapeutic resistance. In this context, the present study aimed to investigate the cytotoxic potential of manool, a diterpene from Salvia officinalis L., in human (A375) and murine (B16F10) melanoma cell lines. The analysis of cytotoxicity using the XTT assay showed the lowest IC₅₀ after 48 h of treatment with the manool, being 17.6 and 18.2 µg/ml for A375 and B16F10, respectively. A selective antiproliferative effect of manool was observed on the A375 cells based on the colony formation assay, showing an IC₅₀ equivalent to 5.6 µg/ml. The manool treatments led to 43.5% inhibition of the A375 cell migration at a concentration of 5.0 µg/ml. However, it did not affect cell migration in the B16F10 cells. Cell cycle analysis revealed that the manool interfered in the cell cycle of the A375 cells, blocking the G2/M phase. No changes in the cell cycle were observed in the B16F10 cells. Interestingly, manool did not induce apoptosis in the A375 cells, but apoptosis was observed after treatment of the B16F10 cells. Additionally, manool showed an antimelanoma effect in a reconstructed human skin model. Furthermore, in silico studies, showed that manool is stabilized in the active sites of the tubulin dimer with comparable energy concerning taxol, indicating that both structures can inhibit the proliferation of cancer cells. Altogether, it is concluded that manool, through the modulation of the cell cycle, presents a selective antiproliferative activity and a potential antimelanoma effect.

Role of phloretin as a sensitizer to TRAIL‑induced apoptosis in colon cancer

Phloretin is one of the apple polyphenols with anticancer activities. Since tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves important roles in inducing apoptosis, the present study examined the effect of phloretin on TRAIL-induced apoptosis in colon cancer cells. Treatment with both phloretin and TRAIL markedly suppressed the survival of cancer cells from several colon cancer cell lines compared with that of cells treated with either TRAIL or phloretin. Additionally, decreased numbers of colonies were observed following addition of phloretin and TRAIL. Furthermore, TRAIL- and phloretin-treated HT-29-Luc cells exhibited decreased luciferase activity. Increased apoptosis was observed in phloretin- and TRAIL-treated HT-29-Luc colon cancer cells, accompanying elevated levels of cleaved poly(ADP-ribose) polymerase, and caspase-3, −8 and −9. The expression levels of MCL1 apoptosis regulator BCL2 family member (Mcl-1) were decreased following addition of phloretin in colon cancer cells. In addition, overexpression of Mcl-1 in phloretin- and TRAIL-treated HT-29-Luc cells resulted in increased cell survival. Treatment of HT-29-Luc cells with a combination of cycloheximide (CHX) and phloretin led to a more prominent decrease in Mcl-1 expression compared with that in cells treated with CHX alone, while Mcl-1 expression was recovered by treatment with MG132. Binding of ubiquitin with Mcl-1 was verified using immunoprecipitation. Intraperitoneal injection of both TRAIL and phloretin into tumor xenografts was associated with a decreased tumor volume compared with that following injection with either TRAIL or phloretin. Overall, the present results suggest a synergistic effect of phloretin on TRAIL-induced apoptosis in colon cancer cells.

Immunosuppressive Roles of Galectin-1 in the Tumor Microenvironment

Evasion of immune surveillance is an accepted hallmark of tumor progression. The production of immune suppressive mediators by tumor cells is one of the major mechanisms of tumor immune escape. Galectin-1 (Gal-1), a pivotal immunosuppressive molecule, is expressed by many types of cancer. Tumor-secreted Gal-1 can bind to glycosylated receptors on immune cells and trigger the suppression of immune cell function in the tumor microenvironment, contributing to the immune evasion of tumors. The aim of this review is to summarize the current literature on the expression and function of Gal-1 in the human tumor microenvironment, as well as therapeutics targeting Gal-1.

Anti-Proliferative, Pro-Apoptotic, Anti-Migrative and Tumor-Inhibitory Effects and Pleiotropic Mechanism of Theaflavin on B16F10 Melanoma Cells

Purpose

Theaflavin (TF) is a primary pigment of tea, exhibiting anti-proliferative, pro-apoptotic and anti-metastatic activities on cancer cell lines. However, it is unknown whether TF is effective in treating melanoma cells.

Methods

To determine the effects of TF on melanoma cells, we conducted in vitro assays of cell viability, DAPI staining, wound healing, transwell, and flow cytometry as well as in vivo experiments on B16F10-bearing mouse model. Real-time PCR (qPCR) and Western blot (WB) were conducted to explore the molecular actions of TF.

Results

The cell viability assay showed that TF exerted inhibitory effect on B16F10 cells in a dose-dependent manner from 40 to 400 μg/mL, with IC₅₀ values ranging from 223.8±7.1 to 103.7±7.0 μg/mL. Moreover, TF induced early and late apoptosis and inhibited migration/invasion of B16F10 cells in a dose-dependent manner, indicating its pro-apoptotic and anti-migrative effects. In vivo, TF significantly inhibited B16F10 tumor size in mice model from 40 to 120 mg/kg, which exerted higher effect than that of cisplatin. The molecular data showed that TF significantly up-regulated the mRNA expressions of pro-apoptotic genes (Bax, Casp3, Casp8, c-fos, c-Jun, and c-Myc), up-regulated the protein expressions of apoptosis-related p53 and JNK signaling molecules (ASK1, phosphorylated Chk1/2, cleaved caspase 3, phosphorylated JNK, c-JUN, cleaved PARP, and phosphorylated p53), and down-regulated the protein expressions of proliferation-related MEK/ERK and PI3K/AKT signaling molecules (phosphorylated MEK1/2, phosphorylated ERK1/2, phosphorylated PI3K, and phosphorylated AKT) as well as the expressions of MMP2 and MMP9.

Conclusion

It can be concluded that TB exhibited anti-proliferative, pro-apoptotic, anti-migrative, and tumor-inhibitory effects on melanoma cells through pleiotropic actions on the above pathways. This study provides new evidence of anti-melanoma efficacy and mechanism of TF, contributing to the development of TF-derived natural products for melanoma therapy.

RIG-I Has a Role in Immunity Against Haemonchus contortus, a Gastrointestinal Parasite in Ovis aries: A Novel Report

Retinoic acid inducible gene I (RIG-I) is associated to the DExD/H box RNA helicases. It is a pattern recognition receptor (PRR), playing a crucial role in the system and is a germ line encoded host sensor to perceive pathogen-associated molecular patterns (PAMPs). So far, reports are available for the role of RIG-I in antiviral immunity. This is the first report in which we have documented the role of RIG-I in parasitic immunity. Haemonchus contortus is a deadly parasite affecting the sheep industry, which has a tremendous economic importance, and the parasite is reported to be prevalent in the hot and humid agroclimatic region. We characterize the RIG-I gene in sheep (Ovis aries) and identify the important domains or binding sites with Haemonchus contortus through in silico studies. Differential mRNA expression analysis reveals upregulation of the RIG-I gene in the abomasum of infected sheep compared with that of healthy sheep, further confirming the findings. Thus, it is evident that, in infected sheep, expression of RIG-I is triggered for binding to more pathogens (Haemonchus contortus). Genetically similar studies with humans and other livestock species were conducted to reveal that sheep may be efficiently using a model organism for studying the role of RIG-I in antiparasitic immunity in humans.

Albumin-based nanoparticles: a promising strategy to overcome cancer drug resistance

Circumvention of cancer drug resistance is one of the major investigations in nanomedicine. In this regard, nanotechnology-based drug delivery has offered various implications. However, protein-based nanocarriers have been a versatile choice compared to other nanomaterials, provided by their favorable characteristics and safety profiles. Specifically, albumin-based nanoparticles have been demonstrated to be an effective drug delivery system, owing to the inherent targeting modalities of albumin, through gp60- and SPARC-mediated receptor endocytosis. Furthermore, surface functionalization was exploited for active targeting, due to albumin’s abundance of carboxylic and amino groups. Stimuli-responsive drug release has also been pertained to albumin nano-systems. Therefore, albumin-based nanocarriers could potentially overcome cancer drug resistance through bypassing drug efflux, enhancing drug uptake, and improving tumor accumulation. Moreover, albumin nanocarriers improve the stability of various therapeutic cargos, for instance, nucleic acids, which allows their systemic administration. This review highlights the recent applications of albumin nanoparticles to overcome cancer drug resistance, the nano-fabrication techniques, as well as future perspectives and challenges.

A Physically Triggered Cell Death via Transbarrier Cold Atmospheric Plasma Cancer Treatment

Cold atmospheric plasma (CAP) is a near room-temperature ionized gas composed of highly reactive species. CAP also generates thermal radiation, ultraviolet radiation, and electromagnetic (EM) waves. So far, nearly all biological effects of CAP have relied on the chemical factors in CAP. Here, we first show that the EM emission from CAP can lead to the death of melanoma cells via a transbarrier contactless method. Compared with reactive species, the effect of the physical factors causes much stronger growth inhibition on a reactive species-resistant melanoma cell line B16F10. Such a physically triggered growth inhibition is due to a new cell death type, characterized by the rapid leakage of bulk solutions from the cells, resulting in cytoplasm shrinkage and bubbling on the cell membrane. The physically based CAP-triggered cell death can occur even there is a macroscale gap between the bulk CAP and cells, which includes an air gap (∼8 mm) and a dielectric material of the dish or plate (∼1 mm). Either a too large or a too small gap will inhibit such cell death. The physically triggered cellular pressure may cause the bubbling on cells, which can be inhibited in a hypotonic environment via the extracellular osmotic pressure. This study builds a foundation to use CAP as a physically based noninvasive cancer treatment.

The TRAIL to cancer therapy: Hindrances and potential solutions

Apoptosis is an ordered and orchestrated cellular process that occurs in physiological and pathological conditions. Resistance to apoptosis is a hallmark of virtually all malignancies. Despite being a cause of pathological conditions, apoptosis could be a promising target in cancer treatment. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), also known as Apo-2 ligand (Apo2L), is a member of TNF cytokine superfamily. It is a potent anti-cancer agent owing to its specific targeting towards cancerous cells, while sparing normal cells, to induce apoptosis. However, resistance occurs either intrinsically or after multiple treatments which may explain why cancer therapy fails. This review summarizes the apoptotic mechanisms via extrinsic and intrinsic apoptotic pathways, as well as the apoptotic resistance mechanisms. It also reviews the current clinically tested recombinant human TRAIL (rhTRAIL) and TRAIL receptor agonists (TRAs) against TRAIL-Receptors, TRAIL-R1 and TRAIL-R2, in which the outcomes of the clinical trials have not been satisfactory. Finally, this review discusses the current strategies in overcoming resistance to TRAIL-induced apoptosis in pre-clinical and clinical settings.

Reduced CTL motility and activity in avascular tumor areas

Patchy infiltration of tumors by cytotoxic T cells (CTLs) predicts poorer prognosis for cancer patients. The factors limiting intratumoral CTL dissemination, though, are poorly understood. To study CTL dissemination in tumors, we histologically examined human melanoma samples and used mice to image B16-OVA tumors infiltrated by OT-I CTLs using intravital two-photon microscopy. In patients, most CTLs concentrated around peripheral blood vessels, especially in poorly infiltrated tumors. In mice, OT-I CTLs had to cluster around tumor cells to efficiently kill them in a contact-and perforin-dependent manner and cytotoxicity was strictly antigen-specific. OT-I CTLs as well as non-specific CTLs concentrated around peripheral vessels, and cleared the tumor cells around them. This was also the case when CTLs were injected directly into the tumors. CTLs crawled rapidly only in areas within 50 µm of flowing blood vessels and transient occlusion of vessels immediately, though reversibly, stopped their migration. In vitro, oxygen depletion and blockade of oxidative phosphorylation also reduced CTL motility. Taken together, these results suggest that hypoxia limits CTL migration away from blood vessels, providing immune-privileged niches for tumor cells to survive. Normalizing intratumoral vasculature may thus synergize with tumor immunotherapy.

MicroRNAs in cancer cell death pathways: Apoptosis and necroptosis

To protect tissues and the organism from disease, potentially harmful cells are removed through programmed cell death processes, including apoptosis and necroptosis. These types of cell death are critically controlled by microRNAs (miRNAs). MiRNAs are short RNA molecules that target and inhibit expression of many cellular regulators, including those controlling programmed cell death via the intrinsic (Bcl-2 and Mcl-1), extrinsic (TRAIL and Fas), p53-and endoplasmic reticulum (ER) stress-induced apoptotic pathways, as well as the necroptosis cell death pathway. In this review, we discuss the current knowledge of apoptosis and necroptosis pathways and how these are impaired in cancer cells. We focus on how miRNAs disrupt apoptosis and necroptosis, thereby critically contributing to malignancy. Understanding which and how miRNAs and their targets affect cell death pathways could open up novel therapeutic opportunities for cancer patients. Indeed, restoration of pro-apoptotic tumor suppressor miRNAs (apoptomiRs) or inhibition of oncogenic miRNAs (oncomiRs) represent strategies that are currently being trialed or are already applied as miRNA-based cancer therapies. Therefore, better understanding the cancer type-specific expression of apoptomiRs and oncomiRs and their underlying mechanisms in cell death pathways will not only advance our knowledge, but also continue to provide new opportunities to treat cancer.

Autophagy inhibitors regulate TRAIL sensitivity in human malignant cells by targeting the mitochondrial network and calcium dynamics

In a variety of cancer cell types, the pharmacological and genetic blockade of autophagy increases apoptosis induced by various anticancer drugs. These observations suggest that autophagy counteracts drug-induced apoptosis. We previously reported that in human melanoma and osteosarcoma cells, autophagy inhibitors, such as 3-methyladenine and chloroquine increased the sensitivity to apoptosis induced by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In the present study, we report that different autophagy inhibitors regulate the mitochondrial network and calcium (Ca²⁺) dynamics in these cells. We found that compared to tumor cells, normal fibroblasts were more resistant to the cytotoxicity of TRAIL and autophagy inhibitors used either alone or in combination. Notably, TRAIL increased the autophagic flux in the tumor cells, but not in the fibroblasts. Live-cell imaging revealed that in tumor cells, TRAIL evoked modest mitochondrial fragmentation, while subtoxic concentrations of the autophagy inhibitors led to mitochondrial fusion. Co-treatment with TRAIL and subtoxic concentrations of the autophagy inhibitors resulted in severe mitochondrial fragmentation, swelling and clustering, similar to what was observed with autophagy inhibitors at toxic concentrations. The enhanced aberration of the mitochondrial network was preceded by a reduction in mitochondrial Ca²⁺ loading and store-operated Ca²⁺ entry. On the whole, the findings of this study indicate that co-treatment with TRAIL and autophagy inhibitors leads to increased mitochondrial Ca²⁺ and network dysfunction in a tumor-selective manner. Therefore, the co-administration of TRAIL and autophagy inhibitors may prove to be a promising tumor-targeting approach for the treatment of TRAIL-resistant cancer cells.

Tumor necrosis factor-related apoptosis-inducing ligand inhibits the growth and aggressiveness of colon carcinoma via the exogenous apoptosis signaling pathway

Colon cancer is one of the most common types of gastrointestinal tumor. Previous studies have demonstrated that tumor necrosis factor-(TNF)-related apoptosis-inducing ligand (TRAIL) reduces the aggressiveness of colon cancer tumors and promotes the apoptosis of colon carcinoma cells. In the present study, the inhibitory effects of TRAIL were investigated and the potential mechanism of TRAIL-mediated apoptosis was explored in colon cancer cells. Reverse transcription-quantitative polymerase chain reaction, western blotting, immunofluorescence, immunohistochemistry, TUNEL and flow cytometry assays were used to analyze the effects of TRAIL on the growth, migration, invasion and apoptosis of colon tumor cells. In vivo experiments were performed in mice to analyze the therapeutic effects of TRAIL. The results demonstrated that TRAIL significantly suppressed the growth of colorectal tumor cells in a dose-dependent manner (0.5–2.5 mg/ml) and also promoted colon tumor cell death. The migration and invasion of colon tumor cells were inhibited by the downregulation of fibronectin, Vimentin and E-cadherin. The apoptotic rate revealed that TRAIL (2.0 mg/ml) significantly promoted the apoptosis of colon tumor cells by regulating apoptosis-related gene expression. TRAIL administration promoted the apoptosis of colon tumor cells via the exogenous apoptosis signaling pathway due to the upregulation of caspase-3, caspase-8 and nuclear factor-κB protein expression. In vivo assays revealed that TRAIL administration significantly inhibited tumor growth and promoted apoptotic body and lymphocyte infiltration, which led to increased survival in tumor-bearing mice compared with the control group. Immunohistochemistry revealed that P53 and B-cell lymphoma-2 were downregulated in TRAIL-treated tumors. In conclusion, TRAIL treatment significantly inhibited the growth and aggressiveness of colon tumors by inducing apoptosis via the exogenous apoptosis pathway, which suggests that TRAIL may be a potential anticancer agent for colon carcinoma therapy.

In vitro and in vivo antimelanoma effect of ethyl ester cyclohexyl analog of ethylenediamine dipropanoic acid

Melanoma, an aggressive skin tumor with high metastatic potential, is associated with high mortality and increasing morbidity. Multiple available chemotherapeutic and immunotherapeutic modalities failed to improve survival in advanced disease, and the search for new agents is ongoing. The aim of this study was to investigate antimelanoma effects of O,O-diethyl-(S,S)-ethylenediamine-N,N'di-2-(3-cyclohexyl) propanoate dihydrochloride (EE), a previously synthesized and characterized organic compound. Mouse melanoma B16 cell viability was assessed using acid phosphatase, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, sulforhodamine B, and lactate dehydrogenase assays. Apoptosis and autophagy were investigated using flow cytometry, fluorescence and electron microscopy, and western blotting. In vivo antitumor potential was assessed in subcutaneous mouse melanoma model after 14 days of treatment with EE. Tumor mass and volume were measured, and RT-PCR was used for investigating the expression of autophagy-related, proapoptotic, and antiapoptotic molecules in tumor tissue. Investigated organic compound exerts significant cytotoxic effect against B16 cells. EE induced apoptosis, as confirmed by phosphatidyl serine externalisation, caspase activation, and ultrastructural features typical for apoptosis seen on fluorescence and electron microscopes. The apoptotic mechanism included prompt disruption of mitochondrial membrane potential and oxidative stress. No autophagy was observed. Antimelanoma action and apoptosis induction were confirmed in vivo, as EE decreased mass and volume of tumors, and increased expression of several proapoptotic genes. EE possesses significant antimelanoma action and causes caspase-dependent apoptosis mediated by mitochondrial damage and reactive oxygen species production. Decrease in tumor growth and increase in expression of proapoptotic genes in tumor tissue suggest that EE warrants further investigation as a candidate agent in treating melanoma.

Cold PSM, but not TRAIL, triggers autophagic cell death: A therapeutic advantage of PSM over TRAIL

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and cold plasma-stimulated medium (PSM) are promising novel anticancer tools due to their strong anticancer activities and high tumor-selectivity. The present study demonstrated that PSM and TRAIL may trigger autophagy in human malignant melanoma and osteosarcoma cells. Live-cell imaging revealed that even under nutritional and stress-free conditions, these cells possessed a substantial level of autophagosomes, which were localized in the cytoplasm separately from tubular mitochondria. In response to cytotoxic levels of PSM, the mitochondria became highly fragmented, and aggregated and colocalized with the autophagosomes. The cytotoxic effects of PSM were suppressed in response to various pharmacological autophagy inhibitors, including 3-methyladenine (3-MA) and bafilomycin A1, thus indicating the induction of autophagic cell death (ACD). Lethal levels of PSM also resulted in non-apoptotic, non-autophagic cell death in a reactive oxygen species-dependent manner under certain circumstances. Furthermore, TRAIL exhibited only a modest cytotoxicity toward these tumor cells, and did not induce ACD and mitochondrial aberration. The combined use of TRAIL and subtoxic concentrations of 3-MA resulted in decreased basal autophagy, increased mitochondrial aberration, colocalization with autophagosomes and apoptosis. These results indicated that PSM may induce ACD, whereas TRAIL may trigger cytoprotective autophagy that compromises apoptosis. To the best of our knowledge, the present study is the first to demonstrate that PSM can induce ACD in human cancer cells. These findings provide a rationale for the advantage of PSM over TRAIL in the destruction of apoptosis-resistant melanoma and osteosarcoma cells.

Quercetin Suppresses CYR61-Mediated Multidrug Resistance in Human Gastric Adenocarcinoma AGS Cells

Cysteine-rich angiogenic inducer 61 (CYR61) is an extracellular matrix-associated protein involved in survival, tumorigenesis, and drug resistance. Therefore, we examined the effects of flavones against CYR61-overexpressing human gastric adenocarcinoma AGS (AGS-cyr61) cells, which show remarkable resistance to 5-fluorouracil (5-FU), adriamycin (ADR), tamoxifen (TAM), paclitaxel (PAC), and docetaxel (DOC). Among the tested flavones, quercetin had the lowest 50% inhibitory concentration (IC₅₀) and significantly reduced the viability of AGS-cyr61 cells compared with AGS cells. Quercetin: (1) reduced multidrug resistance-associated protein 1 and nuclear factor (NF)-kappa B p65 subunit levels; (2) reversed multidrug resistance (MDR); (3) inhibited colony formation and induced caspase-dependent apoptosis; and (4) suppressed migration and down-regulated epithelial-mesenchymal transition-related proteins in AGS-cyr61. Moreover, AGS-cyr61 cells treated with quercetin concentrations close to the IC₅₀ and simultaneously treated with 5-FU or ADR in the sub-lethal range showed strong synergism between quercetin and these two drugs. These findings indicate that CYR61 is a potential regulator of drug resistance and that quercetin may be a novel agent for improving the efficacy of anticancer drugs in AGS-cyr61 cells.

Plasma-stimulated medium kills TRAIL-resistant human malignant cells by promoting caspase-independent cell death via membrane potential and calcium dynamics modulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and cold plasma-stimulated medium (PSM) have been shown to exhibit tumor-selective cytotoxicity and have emerged as promising new tools for cancer treatment. However, to date, at least to the best of our knowledge, no data are available as to which substance is more potent in killing cancer cells. Thus, in this study, we systematically compared their abilities to kill human malignant cells from different origins. We found that PSM dose-dependently killed TRAIL-resistant melanoma, osteosarcoma and neuroblastoma cells. Moreover, PSM had little cytotoxicity toward osteoblasts. PSM was more potent than TRAIL in inducing caspase-3/7 activation, mitochondrial network aberration and caspase-independent cell death. We also found that PSM was more potent in inducing plasma membrane depolarization (PMD) and disrupting endoplasmic-mitochondrial Ca²⁺ homeostasis. Moreover, persistent PMD was caused by different membrane-depolarizing agents; the use of the anti-type II diabetes drug, glibenclamide, alone caused mitochondrial fragmentation and enhanced TRAIL-induced Ca²⁺ modulation, mitochondrial network abnormalities and caspase-independent cell killing. These results demonstrate that PSM has a therapeutic advantage over TRAIL owing to its greater capacity to evoke caspase-independent cell death via mitochondrial network aberration by disrupting membrane potential and Ca²⁺ homeostasis. These findings may provide a strong rationale for developing PSM as a novel approach for the treatment of TRAIL-resistant malignant cells.

The inhibitory effects of compound Muniziqi granule against B16 cells and harmine induced autophagy and apoptosis by inhibiting Akt/mTOR pathway

Background

Compound Muniziqi granule (MNZQ) is a multi-component herbal preparation and a popular traditional Uighur medicine used in China for treating endocrine disorder-induced acne, chloasma, dysmenorrhea, menopausal syndrome, and melanoma. Harmine presented in MNZQ has been confirmed potential anticancer effect on the B16 cells among others. The purpose of this study is to explore the inhibitory effects of MNZQ against B16 cells and mechanism of autophagy and apoptosis induced by harmine in B16 cells.

Methods

The cell viability was calculated by CCK8 assay. The in vitro tyrosinase activity was determined by spectrophotometry. The harmine-induced autophagy was demonstrated by electron microscopy and MDC staining. Flow cytometry was used to measure cell death and cell cycle distribution. All proteins expression was assessed by western blot.

Results

MNZQ and some herb extracts contained in preparation displayed inhibitory effects on B16 cells but without inhibition on mushroom tyrosinase compared with kojic acid. The formation of autophagosome was markedly induced by harmine with the accretion of LC3-II and the degeneration of p62 in B16 cells, which indicated that harmine was an autophagy inducer. Cell death and sub-G2 population suggested that harmine could induce cell death. Particularly, 3-MA, an autophagy inhibitor, was discovered to prevent harmine-induced decrease of the cell viability and cell cycle arrest on G2 phase, indicating that autophagy was vital to the cell death. In addition, the results indicated that harmine could inhibit the phosphorylation of Akt and mTOR, which might mediate autophagy.

Conclusion

Harmine could induce autophagy and apoptosis by inhibiting Akt/mTOR pathway in B16 cells. Harmine might be a promising therapeutic agent for treatment of melanoma in MNZQ.

Disrupting mitochondrial Ca2+ homeostasis causes tumor-selective TRAIL sensitization through mitochondrial network abnormalities

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has emerged as a promising anticancer agent with high tumor-selective cytotoxicity. The congenital and acquired resistance of some cancer types including malignant melanoma and osteosarcoma impede the current TRAIL therapy of these cancers. Since fine tuning of the intracellular Ca2+ level is essential for cell function and survival, Ca2+ dynamics could be a promising target for cancer treatment. Recently, we demonstrated that mitochondrial Ca2+ removal increased TRAIL efficacy toward malignant melanoma and osteosarcoma cells. Here we report that mitochondrial Ca2+ overload leads to tumor-selective sensitization to TRAIL cytotoxicity. Treatment with the mitochondrial Na+/Ca2+ exchanger inhibitor CGP-37157 and oxidative phosphorylation inhibitor antimycin A and FCCP resulted in a rapid and persistent mitochondrial Ca2+ rise. These agents also increased TRAIL sensitivity in a tumor-selective manner with a switching from apoptosis to a nonapoptotic cell death. Moreover, we found that mitochondrial Ca2+ overload led to increased mitochondrial fragmentation, while mitochondrial Ca2+ removal resulted in mitochondrial hyperfusion. Regardless of their reciprocal actions on the mitochondrial dynamics, both interventions commonly exacerbated TRAIL-induced mitochondrial network abnormalities. These results expand our previous study and suggest that an appropriate level of mitochondrial Ca2+ is essential for maintaining the mitochondrial dynamics and the survival of these cells. Thus, disturbing mitochondrial Ca2+ homeostasis may serve as a promising approach to overcome the TRAIL resistance of these cancers with minimally compromising the tumor-selectivity.

Bcl‑2 associated athanogene 4 promotes proliferation, migration and invasion of gastric cancer cells

Currently, with the increase of morbidity and mortality rate, gastric cancer (GC) is attracting increasing attention in China. Bcl-2-associated athanogene 4 (BAG4) has been identified as a tumor promoter in several tumors, but its role in GC remains unknown. The present study aimed to detect the expression of BAG4 and determine its function in the progression of GC. The results from reverse transcription-quantitative polymerase chain reaction and western blotting revealed that BAG4 was markedly upregulated in highly metastatic cell lines (SGC7901 and MGC803), compared with the lower-metastatic cell lines (AGS and BGC823). Through Cell Counting Kit-8, cell cycle, apoptosis, Transwell and colony formation assays, BAG4 was demonstrated to promote the proliferation, migration and invasion of GC cells in vitro. Additionally, in vivo assays further certified that BAG4 can increase the proliferation and invasion of GC cells. In conclusion, these findings implicate BAG4 as a potential therapeutic target for GC.

Mitochondrial Ca2+ removal amplifies TRAIL cytotoxicity toward apoptosis-resistant tumor cells via promotion of multiple cell death modalities

Ca2+ has emerged as a new target for cancer treatment since tumor-specific traits in Ca2+ dynamics contributes to tumorigenesis, malignant phenotypes, drug resistance, and survival in different tumor types. However, Ca2+ has a dual (pro-death and pro-survival) function in tumor cells depending on the experimental conditions. Therefore, it is necessary to minimize the onset of the pro-survival Ca2+ signals caused by the therapy. For this purpose, a better understanding of pro-survival Ca2+ pathways in cancer cells is critical. Here we report that Ca2+ protects malignant melanoma (MM) and osteosarcoma (OS) cells from tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) cytotoxicity. Simultaneous measurements using the site-specific Ca2+ probes showed that acute TRAIL treatment rapidly and dose-dependently increased the cytosolic Ca2+ concentration ([Ca2+]cyt) and mitochondrial Ca2+ concentration ([Ca2+]mit) Pharmacological analyses revealed that the [Ca2+]mit remodeling was under control of mitochondrial Ca2+ uniporter (MCU), mitochondrial permeability transition pore (MPTP), and a Ca2+ transport pathway sensitive to capsazepine and AMG9810. Ca2+ chelators and the MCU inhibitor ruthenium 360, an MPTP opener atractyloside, capsazepine, and AMG9810 all decreased [Ca2+]mit and sensitized these tumor cells to TRAIL cytotoxicity. The Ca2+ modulation enhanced both apoptotic and non-apoptotic cell death. Although the [Ca2+]mit reduction potentiated TRAIL-induced caspase-3/7 activation and cell membrane damage within 24 h, this potentiation of cell death became pronounced at 72 h, and not blocked by caspase inhibition. Our findings suggest that in MM and OS cells mitochondrial Ca2+ removal can promote apoptosis and non-apoptotic cell death induction by TRAIL. Therefore, mitochondrial Ca2+ removal can be exploited to overcome the resistance of these cancers to TRAIL.

Immune surveillance in melanoma: From immune attack to melanoma escape and even counterattack

Pharmacologic inhibition of the cytotoxic T lymphocyte antigen 4 (CTLA4) and the programmed death receptor-1 (PD1) has resulted in unprecedented durable responses in metastatic melanoma. However, resistance to immunotherapy remains a major challenge. Effective immune surveillance against melanoma requires 4 essential steps: activation of the T lymphocytes, homing of the activated T lymphocytes to the melanoma microenvironment, identification and episode of melanoma cells by activated T lymphocytes, and the sensitivity of melanoma cells to apoptosis. At each of these steps, there are multiple factors that may interfere with the immune surveillance machinery, thus allowing melanoma cells to escape immune attack and develop resistance to immunotherapy. We provide a comprehensive review of the complex immune surveillance mechanisms at play in melanoma, and a detailed discussion of how these mechanisms may allow for the development of intrinsic or acquired resistance to immunotherapeutic modalities, and potential avenues for overcoming this resistance.

STAT3 targeting by polyphenols: Novel therapeutic strategy for melanoma

Melanoma or malignant melanocytes appear with the low incidence rate, but very high mortality rate worldwide. Epidemiological studies suggest that polyphenolic compounds contribute for prevention or treatment of several cancers particularly melanoma. Such findings motivate to dig out novel therapeutic strategies against melanoma, including research toward the development of new chemotherapeutic and biologic agents that can target the tumor cells by different mechanisms. Recently, it has been found that signal transducer and activator of transcription 3 (STAT3) is activated in many cancer cases surprisingly. Different evidences supply the aspect that STAT3 activation plays a vital role in the metastasis, including proliferation of cells, survival, invasion, migration, and angiogenesis. This significant feature plays a vital role in various cellular processes, such as cell proliferation and survival. Here, we reviewed the mechanisms of the STAT3 pathway regulation and their role in promoting melanoma. Also, we have evaluated the emerging data on polyphenols (PPs) specifically their contribution in melanoma therapies with an emphasis on their regulatory/inhibitory actions in relation to STAT3 pathway and current progress in the development of phytochemical therapeutic techniques. An understanding of targeting STAT3 by PPs brings an opportunity to melanoma therapy. © 2016 BioFactors, 43(3):347-370, 2017.

Multiple hyperthermia-mediated release of TRAIL/SPION nanocomplex from thermosensitive polymeric hydrogels for combination cancer therapy

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) possesses strong anti-cancer potential because of its ability to specifically kill cancer cells. However, clinical use of TRAIL is impeded by its short in vivo half-life and native TRIAL-resistant cancer cell populations. To overcome these limitations, we designed a multiple magnetic hyperthermia (MHT)-mediated TRAIL release system for combination therapy using an injectable, biodegradable and thermosensitive polymeric hydrogel. In this system, positively charged TRAIL and hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) are complexed with negatively charged poly(organophosphazene) polymers via ionic and hydrophobic interactions, respectively. Transmission electron microscopy images showed a nano-sized core-shell structure of the TRAIL/SPION polymeric nanocomplex in aqueous solution that transformed into a hydrogel at body temperature. Hyperthermia can enhance the release of TRAIL from hydrogels through temperature-sensitive hydrogel dissolution. TRAIL-resistant U-87 MG cells were killed by the combination of TRAIL and multiple hyperthermia via caspase-3 and -8 active apoptosis. The hyperthermia-enhanced cytotoxicity of TRAIL was dependent on the hyperthermia cycle number and corresponding TRAIL release. Significant in vivo tumor reduction was observed by combining 2 cycles of mild MHT and TRAIL release using a single injection of TRAIL/SPION nanocomplex hydrogels without damage to main organs. Furthermore, the therapeutic outcomes can be monitored by long-term magnetic resonance imaging.

Journey of TRAIL from Bench to Bedside and its Potential Role in Immuno-Oncology

Induction of apoptosis in cancer cells has increasingly been the focus of many therapeutic approaches in oncology field. Since its identification as a TNF family member, TRAIL (TNF-related apoptosis-inducing ligand) paved a new path in apoptosis inducing cancer therapies. Its selective ability to activate extrinsic and intrinsic cell death pathways in cancer cells only, independently from p53 mutations responsible for conventional therapeutics resistance, spotted TRAIL as a potent cancer apoptotic agent. Many recombinant preparations of TRAIL and death receptor targeting monoclonal antibodies have been developed and being tested pre-clinically and clinically both as a single agent and in combinations. Of note, the monoclonal antibodies were not the only type of antibodies developed to target TRAIL receptors. Recent technology has brought forth several single chain variable domains (scFv) designs fused recombinantly to TRAIL as well. Also, it is becoming progressively more understandable that field of nanotechnology has revolutionized cancer diagnosis and therapy. The recent breakthroughs in materials science and protein engineering have helped considerably in strategically loading drugs into nanoparticles or conjugating drugs to their surface. In this review we aim to comprehensively highlight the molecular knowledge of TRAIL in the context of its pathway, receptors and resistance factors. We also aim to review the clinical trials that have been done using TRAIL based therapies and to review various scFv designs, the arsenal of nano-carriers and molecules available to selectively target tumor cells with TRAIL.

The Hydrogen Sulfide Releasing Molecule Acetyl Deacylasadisulfide Inhibits Metastatic Melanoma

Melanoma is the most common form of skin cancer. Given its high mortality, the interest in the search of preventive measures, such as dietary factors, is growing significantly. In this study we tested, in vitro and in vivo, the potential anti-cancer effect of the acetyl deacylasadisulfide (ADA), a vinyl disulfide compound, isolated and purified from asafoetida a foul-smelling oleo gum-resin of dietary and medicinal relevance. ADA markedly suppressed proliferation of human melanoma cell lines by inducing apoptosis. Moreover, treatment of melanoma cells with ADA reduced nuclear translocation and activation of NF-κB, decreased the expression of the anti-apoptotic proteins c-FLIP, XIAP, and Bcl-2 and inhibited the phosphorylation and activation of both AKT and ERK proteins, two of the most frequently deregulated pathways in melanoma. Finally, the results obtained in vitro were substantiated by the findings that ADA significantly and dose-dependently reduced lung metastatic foci formation in C57BL/6 mice. In conclusion, our findings suggest that ADA significantly inhibits melanoma progression in vivo and could represent an important lead compound for the development of new anti-metastatic agents.

PGRMC1-dependent autophagy by hyperoside induces apoptosis and sensitizes ovarian cancer cells to cisplatin treatment

Cisplatin treatment some times leads to chemoresistance, which is now acknowledged partially due to the inductive expression of progesterone receptor membrane component (PGRMC)1 in ovarian cancer cells. PGRMC1 enhances autophagy, activates cytochrome p450, and inveigles signaling pathways to promote cell survival and reduce the effect of drug treatments. In this study, we give first line evidence that hyperoside inhibits cell viability, triggers autophagy and apoptosis in ovarian cancer cell lines. Mechanistically, PGRMC1-dependent autophagy was utilized by hyperoside to induce apoptotic cell death. Hyperoside induced the conversion of LC3B-I to LC3B-II and the formation of autophagosomes in ovarian cancer cells. Notably, PGRMC1 colocolized with LC3B‑II, and PGRMC1 overexpression enhanced hyperoside-induced autophagy and apoptosis, while PGRMC1 knockdown abrogated the action. Additionally, AKT signaling and Bcl-2 family were also involved in the hyperoside-induced autophagy and apoptosis. Importantly, in cisplatin-resistant ovarian cancer cells where PGRMC1 was overexpressed, hyperoside sensitized the cells to cisplatin treatment. Together these findings indicate hyperoside functions as a complementary therapy for ovarian cancer patients receiving platinum-based therapy.

RACK1 promotes hepatocellular carcinoma cell survival via CBR1 by suppressing TNF-α-induced ROS generation

It has been reported that intracellular accumulation of reactive oxygen species (ROS) has a significant role in tumor necrosis factor (TNF)-α-induced cell apoptosis and necrosis; however, the key molecules regulating ROS generation remain to be elucidated. The present study reports that knockdown of endogenous receptor for activated C kinase 1 (RACK1) increases the intracellular ROS level following TNF-α or H₂O₂ stimulation in human hepatocellular carcinoma (HCC) cells, leading to promotion of cell death. Carbonyl reductase 1 (CBR1), a ubiquitous nicotinamide adenine dinucleotide phosphate-dependent enzyme, is reported to protect cells from ROS-induced cell damage. The present study reports that RACK1 is a regulator of CBR1 that interacts with and sustains the protein stability of CBR1. Overexpression of CBR1 reverses the enhanced cell death due to RACK1 knockdown. Taken together, the results of the present study suggest that RACK1 protects HCC cells from TNF-α-induced cell death by suppressing ROS generation through interacting with and regulating CBR1.

Targeting miRNAs associated with surface expression of death receptors to modulate TRAIL resistance in breast cancer

Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) is capable of inducing apoptosis upon engagement of its death receptors (DRs) 4 and 5. TRAIL therapy has garnered intense interest as one of the most promising agents for cancer therapy, for its selective induction of tumor-cell apoptosis while low toxicity to most normal cells. However, a variety of breast cancer cell lines could be resistant to TRAIL-induced apoptosis. Absence of DR4 and DR5 on the breast cancer cell surface has been proposed to be critically involved in resistance to TRAIL and its agonistic antibodies. Moreover, endocytosis and autophagy in breast cancer cells could induce TRAIL resistance through downregulation of surface DR4/5. MicroRNAs (miRNAs), as endogenously expressed small non-coding RNAs, function as regulators of gene expression and involve tremendous biological processes including drug resistance. In this review, we highlight recent advances in the functional role of miRNAs in endocytosis and autophagy pathways. This review aims to present that, through regulation of critical molecules involved in autophagy and endocytosis, miRNAs could lead to mislocalization of DR4/5 in breast cancer cells and therefore play an important role in TRAIL-mediated apoptosis and TRAIL resistance.

Fisetin, a phytochemical, potentiates sorafenib-induced apoptosis and abrogates tumor growth in athymic nude mice implanted with BRAF-mutated melanoma cells

Melanoma is the most deadly form of cutaneous malignancy, and its incidence rates are rising worldwide. In melanoma, constitutive activation of the BRAF/MEK/ERK (MAPK) and PI3K/AKT/mTOR (PI3K) signaling pathways plays a pivotal role in cell proliferation, survival and tumorigenesis. A combination of compounds that lead to an optimal blockade of these critical signaling pathways may provide an effective strategy for prevention and treatment of melanoma. The phytochemical fisetin is known to possess anti-proliferative and pro-apoptotic activities. We found that fisetin treatment inhibited PI3K signaling pathway in melanoma cells. Therefore, we investigated the effect of fisetin and sorafenib (an RAF inhibitor) alone and in combination on cell proliferation, apoptosis and tumor growth. Combination treatment (fisetin + sorafenib) more effectively reduced the growth of BRAF-mutated human melanoma cells at lower doses when compared to individual agents. In addition, combination treatment resulted in enhanced (i) apoptosis, (ii) cleavage of caspase-3 and PARP, (iii) expression of Bax and Bak, (iv) inhibition of Bcl2 and Mcl-1, and (v) inhibition of expression of PI3K, phosphorylation of MEK1/2, ERK1/2, AKT and mTOR. In athymic nude mice subcutaneously implanted with melanoma cells (A375 and SK-MEL-28), we found that combination therapy resulted in greater reduction of tumor growth when compared to individual agents. Furthermore, combination therapy was more effective than monotherapy in: (i) inhibition of proliferation and angiogenesis, (ii) induction of apoptosis, and (iii) inhibition of the MAPK and PI3K pathways in xenograft tumors. These data suggest that simultaneous inhibition of both these signaling pathways using combination of fisetin and sorafenib may serve as a therapeutic option for the management of melanoma.

Role of nanotechnology and gene delivery systems in TRAIL-based therapies

Since its identification as a member of the tumour necrosis factor (TNF) family, TRAIL (TNF-related apoptosis-inducing ligand) has emerged as a new avenue in apoptosis-inducing cancer therapies. Its ability to circumvent the chemoresistance of conventional therapeutics and to interact with cancer stem cells (CSCs) self-renewal pathways, amplified its potential as a cancer apoptotic agent. Many recombinant preparations of this death ligand and monoclonal antibodies targeting its death receptors have been tested in monotherapy and combinational clinical trials. Gene therapy is a new approach for cancer treatment which implies viral or non-viral functional transgene induction of apoptosis in cancer cells or repair of the underlying genetic abnormality on a molecular level. The role of this approach in overcoming the traditional barriers of radiation and chemotherapeutics systemic toxicity, risk of recurrence, and metastasis made it a promising platform for cancer treatment. The recent first Food Drug Administration (FDA) approved oncolytic herpes virus for melanoma treatment brings forth the potency of the cancer gene therapy approach in the future. Many gene delivery systems have been studied for intratumoural TRAIL gene delivery alone or in combination with chemotherapeutic agents to produce synergistic cancer cytotoxicity. However, there still remain many obstacles to be conquered for this different gene delivery systems. Nanomedicine on the other hand offers a new frontier for clinical trials and biomedical research. The FDA approved nanodrugs motivates horizon exploration for other nanoscale designed particles’ implications in gene delivery. In this review we aim to highlight the molecular role of TRAIL in apoptosis and interaction with cancer stem cells (CSCs) self-renewal pathways. Finally, we also aim to discuss the different roles of gene delivery systems, mesenchymal cells, and nanotechnology designs in TRAIL gene delivery.

Resistance to ursolic acid-induced apoptosis through involvement of melanogenesis and COX-2/PGE2 pathways in human M4Beu melanoma cancer cells

Melanoma is one of the most aggressive forms of cancer with a continuously growing incidence worldwide and is usually resistant to chemotherapy agents, which is due in part to a strong resistance to apoptosis. Previously, we had showed that B16-F0 murine melanoma cells undergoing apoptosis are able to delay their own death induced by ursolic acid (UA), a natural pentacyclic triterpenoid compound. We had demonstrated that tyrosinase and TRP-1 up-regulation in apoptotic cells and the subsequent production of melanin were implicated in an apoptosis resistance mechanism. Several resistance mechanisms to apoptosis have been characterized in melanoma such as hyperactivation of DNA repair mechanisms, drug efflux systems, and reinforcement of survival signals (PI3K/Akt, NF-κB and Raf/MAPK pathways). Otherwise, other mechanisms of apoptosis resistance involving different proteins, such as cyclooxygenase-2 (COX-2), have been described in many cancer types. By using a strategy of specific inhibition of each ways, we suggested that there was an interaction between melanogenesis and COX-2/PGE2 pathway. This was characterized by analyzing the COX-2 expression and activity, the expression of tyrosinase and melanin production. Furthermore, we showed that anti-proliferative and proapoptotic effects of UA were mediated through modulation of multiple signaling pathways including Akt and ERK-1/2 proteins. Our study not only uncovers underlying molecular mechanisms of UA action in human melanoma cancer cells but also suggest its great potential as an adjuvant in treatment and cancer prevention.

Engineered adenovirus fiber shaft fusion homotrimer of soluble TRAIL with enhanced stability and antitumor activity

Successful cancer therapies aim to induce selective apoptosis in neoplastic cells. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered an attractive anticancer agent due to its tumor cell-specific cytotoxicity. However, earlier studies with recombinant TRAIL revealed many shortcomings, including a short half-life, off-target toxicity and existence of TRAIL-resistant tumor cells. In this study, we developed a novel engineering strategy for recombinant soluble TRAIL by redesigning its structure with the adenovirus knobless fiber motif to form a stable homotrimer with improved antitumor activity. The result is a highly stable fiber-TRAIL fusion protein that could form homotrimers similar to natural TRAIL. The recombinant fusion TRAIL developed here displayed high specific activity in both cell-based assays in vitro and animal tests in vivo. This construct will serve as a foundation for a new generation of recombinant proteins suitable for use in preclinical and clinical studies and for effective combination therapies to overcome tumor resistance to TRAIL.

Ethanol Extract of Oldenlandia diffusa - an Effective Chemotherapeutic for the Treatment of Colorectal Cancer in Humans: -Anti-Cancer Effects of Oldenlandia diffusa

Objectives:

Oldenlandia diffusa is traditionally used to relieve the symptoms of and to treat various diseases, but its anti-cancer activity has not been well studied. In the present study, the authors investigated the anti-cancer effects of an ethanol extract of Oldenlandia diffusa (EOD) on HT-29 human adenocarcinoma cells.

Methods:

Cells were treated with different concentrations of an EOD, and cell death was assessed by using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Analyses of the sub G1 peak, the caspase-3 and -9 activities, and the mitochondrial membrane depolarizations were conducted to confirm cell death by apoptosis. Also, intracellular reactive oxygen species (ROS) generation was determined using carboxy-H2DCFDA (5-(and-6)-carboxy-20,70-dichlorodihydrofluorescein diacetate).

Results:

EOD inhibited the proliferation of HT-29 cells for 24 hours by 78.6% ± 8.1% at 50 μg/mL, 74.4% ± 4.6% at 100 μg/mL, 65.9% ± 5.2% at 200 μg/mL, 51.4% ± 6.2% at 300 μg/mL, and by 41.7% ± 8.9% at 400 μg/mL, and treatment for 72 hours reduced the proliferation at the corresponding concentrations by 43.3% ± 8.8%, 24.3 ± 5.1 mV, 13.5 ± 3.2 mV, 6.5 ± 2.3 mV, and by 2.6 ± 2.3 mV. EOD increased the number of cells in the sub-G1 peak in a dose-dependent manner. The mitochondrial membrane depolarization was elevated by EOD. Also, caspase activities were dose-dependently elevated in the presence of EOD, and these activities were repressed by a pan-caspase inhibitor (zVAD-fmk). The ROS generation was significantly increased by EOD and N-acetyl-L-cysteine (NAC; a ROS scavenger) remarkably abolished EOD-induced cell death. In addition, a combination of sub-optimal doses of EOD and chemotherapeutic agents noticeably suppressed the growth of HT-29 cancer cells.

Conclusion:

These results indicate that EOD might be an effective chemotherapeutic for the treatment of human colorectal cancer.

Sources for Leads: Natural Products and Libraries

Natural products have traditionally been a major source of leads in the drug discovery process. However, the development of high-throughput screening led to an increased interest in synthetic methods that enabled the rapid construction of large libraries of molecules. This resulted in the termination or downscaling of many natural product research programs, but the chemical libraries did not necessarily produce a larger amount of drug leads. On one hand, this chapter explores the current state of natural product research within the drug discovery process. On the other hand it evaluates the efforts made to increase the amount of leads generated from chemical libraries and considers what role natural products could play here.

Apoptosis of AGS human gastric adenocarcinoma cells by methanolic extract of Dictamnus

BACKGROUND

The root bark of Dictamnus dasycarpus Turcz has traditionally been used in East Asia to treat skin diseases such as eczema, atopic dermatitis, and psoriasis. However, it has also been reported to exhibit an anti-proliferative effect on cancer cells.

OBJECTIVE

To investigate the anti-cancer effects of a methanol extract of Dictamnus dasycarpus root bark (MEDD) on AGS cells (a human gastric adenocarcinoma cell-line).

MATERIALS AND METHODS

An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium assay, a caspase activity assay, cell cycle analysis, mitochondrial membrane potential (MMP) measurements, and western blotting were used to investigate the anti-cancer effects of MEDD on AGS cells.

RESULTS

Treatment with MEDD significantly and concentration-dependently inhibited AGS cell growth. MEDD treatment in AGS cells led to increased accumulation of apoptotic sub-G1 phase cells in a concentration-dependent manner. Also, MEDD reduced the expressions of pro-caspase-3, -8 and -9, and increased the active form of caspase-3. Furthermore, subsequent Western blotting revealed elevated levels of poly (ADP-ribose) polymerase protein. MEDD treatment reduced levels of MMP and anti-apoptotic Bcl-2 and Bcl-xL proteins. Pretreatment with SB203580 (a specific inhibitor of p38 mitogen-activated protein kinases), SP600125 (a potent inhibitor of C-Jun N-terminal kinases), or PD98059 (a potent inhibitor of extracellular signal-regulated kinases) did not modify the effects of MEDD treatment. However, pretreatment with LY294002 (a specific inhibitor of Akt) significantly enhanced MEDD-induced cell death.

CONCLUSION

These results suggest that MEDD-mediated cell death is associated with the intrinsic apoptotic pathway and that inhibition of Akt signaling contributes to apoptosis induction by MEDD.

Association of a Methanol Extract of Rheum undulatum L. Mediated Cell Death in AGS Cells with an Intrinsic Apoptotic Pathway

OBJECTIVES

Rheum undulatum L. has traditionally been used for the treatment of many diseases in Asia. However, its anti-proliferative activity in cancer has still not been studied. In the present study, we investigated the anti-cancer effects of methanol extract of Rheum undulatum L. (MERL) on human adenocarcinoma gastric cell lines (AGS).

METHODS

To investigate the anti-cancer effect of MERL on AGS cells, we treated the AGS cells with varying con¬centrations of MERL and performed 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays. Cell cycle analyses, measurements of the mitochondrial membrane potential (MMP), caspase activity assays and Western blots were conducted to determine whether AGS cell death occurred by apoptosis.

RESULTS

Treatment with MERL significantly inhibited growth of AGS cells in a concentration dependent manner. MERL treatment in AGS cells leaded to increased accumulation of apoptotic sub G1 phase cells in a concentration dependent manner. In control cultures, 5.38% of the cells were in the sub G1 phase. In MERL treated cells, however, this percentage was significantly increased (9.95% at 70 μg/mL, 15.94% at 140 μg/mL, 26.56% at 210 μg/mL and 38.08% at 280 μg/mL). MERL treatment induced the decreased expression of pro-caspase-8 and -9 in a concentration dependent manner, whereas the expression of the active form of caspase-3 was increased. A subsequent Western blot analysis revealed increased cleaved levels of poly (ADP-ribose) polymerase (PARP) protein. Also, treatment with MERL increased the activities of caspase-3 and -9 compared with the control. MERL treatment increased the levels of the pro-apoptotic truncated Bid (tBid) and Bcl2 Antagonist X (Bax) proteins and decreased the levels of the anti-apoptotic B-cell lymphoma 2 (Bcl-2) protein, whose is the stabilization of mitochondria. However, inhibitions of p38, extracellular signal regulated kinases (ERKs) and C-Jun N-terminal kinases (JNK) by MERL treatment did not affect cell death.

CONCLUSION

These results suggest that MERL mediated cell death is associated with an intrinsic apoptotic pathway in AGS cells.

Bim and VDAC1 are hierarchically essential for mitochondrial ATF2 mediated cell death

BACKGROUND

ATF2 mediated cytochrome c release is the formation of a channel with some unknown factors larger than that of the individual proteins. BHS-only proteins (BH3s), such as Bim, could induce BAX and VDAC, forming a new channel. According to this facts, we can speculated that there is possible signal relationship with BH3s and ATF2, which is associated with mitochondrial-based death programs.

METHODS

The growth inhibitory effects of mitochondrial ATF2 were tested in cancer cell lines B16F10, A549, EG7, and LL2. Apoptosis was measured by flow cytometry. The effects of ATF2 and levels of apoptosis regulatory proteins were measured by Western blotting. The interaction of proteins were evaluated by immunoprecipitation analysis. The in vivo antitumor activity of mitochondrial ATF2 were tested in xenograft B16F10 models.

RESULTS

Genotoxic stress enabled mitochondrial ATF2 accumulation, perturbing the HK1-VDAC1 complex, increasing mitochondrial permeability, and promoting apoptosis. ATF2 inhibition strongly reduced the conformational activation of Bim, suggesting that Bim acts downstream of ATF2. Although Bim downregulation had no effect on ATF2 activation, Bim knockdown abolished VDAC1 activation; the failure of VDAC1 activation in Bim-depleted cells could be reversed by the BH3-only protein mimic ABT-737. We also demonstrate that silencing of ATF2 in B16F10 cells increases both the incidence and prevalence of tumor xenografts in vivo, whereas stably mitochondrial ATF2 transfection inhibited B16F10 tumor xenografts growth.

CONCLUSIONS

Altogether, these results show that ATF2 is a component of the apoptosis machinery that involves a hierarchical contribution of ATF2, Bim, and VDAC1. Our data offer new insight into the mechanism of mitochondrial ATF2 in mitochondrial apoptosis.

Sulforaphane-induced apoptosis involves p53 and p38 in melanoma cells

In malignant melanoma complex reprogramming of cell death and survival pathways leads to increased chemoresistance and poor longer-term survival. Sulforaphane (SF) is a promising isothiocyanate compound occurring in cruciferous plants with reported antiproliferative and proapoptotic activity in several tumor cell lines including melanoma. In this work we investigated the effects of SF in several melanoma cell lines and fresh melanoma cultivates. We found that SF is cytotoxic and induces mitochondrial, caspase-dependent apoptosis in our study model, however with lower efficiency in fresh melanoma cultivates. Moreover, our results indicate that in melanoma cell lines and fresh melanoma cultivates SF induces multiple signaling including oxidative stress-mediated activation of DNA-damage response pathway, changes in p38 kinase activity and enhanced expression of Bax and Puma proapoptotic proteins. In addition, in SF-exposed p53-mutant melanoma cells Puma expression seem to be under p38 control and acts as a compensatory proapoptotic mechanism. Conversely, decreased apoptosis in SF-exposed melanoma cultivates might be attributed to Akt-mediated suppression of p38 as well as p53 activity. Together, our results suggest that SF inhibits growth and proliferation and induces mitochondrial apoptosis both in melanoma cell lines as well as in fresh melanoma cultivates. This proapoptotic effect might be enhanced in combination with Akt inhibitors, in particular in melanoma samples. SF is thus commendable for further preclinical testing, both as a single agent as well as in combination regimens.