The CD95 (APO-1/Fas) and the TRAIL (APO-2L) apoptosis systems

Poncirin Induces Apoptosis in AGS Human Gastric Cancer Cells through Extrinsic Apoptotic Pathway by up-Regulation of Fas Ligand

Poncirin, a natural bitter flavanone glycoside abundantly present in many species of citrus fruits, has various biological benefits such as anti-oxidant, anti-microbial, anti-inflammatory and anti-cancer activities. The anti-cancer mechanism of Poncirin remains elusive to date. In this study, we investigated the anti-cancer effects of Poncirin in AGS human gastric cancer cells (gastric adenocarcinoma). The results revealed that Poncirin could inhibit the proliferation of AGS cells in a dose-dependent manner. It was observed Poncirin induced accumulation of sub-G1 DNA content, apoptotic cell population, apoptotic bodies, chromatin condensation, and DNA fragmentation in a dose-dependent manner in AGS cells. The expression of Fas Ligand (FasL) protein was up-regulated dose dependently in Poncirin-treated AGS cells Moreover, Poncirin in AGS cells induced activation of Caspase-8 and -3, and subsequent cleavage of poly(ADP-ribose) polymerase (PARP). Inhibitor studies’ results confirm that the induction of caspase-dependent apoptotic cell death in Poncirin-treated AGS cells was led by the Fas death receptor. Interestingly, Poncirin did not show any effect on mitochondrial membrane potential (ΔΨm), pro-apoptotic proteins (Bax and Bak) and anti-apoptotic protein (Bcl-xL) in AGS-treated cells followed by no activation in the mitochondrial apoptotic protein caspase-9. This result suggests that the mitochondrial-mediated pathway is not involved in Poncirin-induced cell death in gastric cancer. These findings suggest that Poncirin has a potential anti-cancer effect via extrinsic pathway-mediated apoptosis, possibly making it a strong therapeutic agent for human gastric cancer.

TRIM21, a negative modulator of LFG in breast carcinoma MDA-MB-231 cells in vitro

Lifeguard (LFG) is a transmembrane protein which is highly expressed in tissues of the hippocampus and the cerebellum, especially during postnatal development. This protein is responsible for the protection of neurons against Fas-induced apoptosis, and the same effect can be seen in tumor cells derived from mastocarcinoma. However, the molecular function of LFG and its regulation in the carcinogenesis of human breast cells remains to be elucidated. In the present study, we investigated the connection of the interaction of LFG within an array analysis of over 9,000 different proteins. Results showed an interaction between the proteins tripartite motif-containing 21 (TRIM21) and LFG and a negative regulatory effect of TRIM21 towards LFG on the protein level. Furthermore, Fas-induced apoptosis decreased upon the addition of TRIM21 to the cultured cells. These results revealed TRIM21 to be a negative modulator of LFG in cells of mastocarcinoma in vitro. For all analyses, MDA-MB-231 cells were used. The interaction of TRIM21 and LFG was analyzed by co-immunoprecipitation. To examine changes in regulatory processes, western blot analyses, real-time PCR, activity of apoptotic process and flow cytometric analyses were carried out.

Induction of apoptosis by an ethanol extract of Poria cocos Wolf. in human leukemia U937 cells

Poria cocos Wolf., which belongs to the Polyporaceae family, has been widely used as an Oriental traditional herbal medicine for centuries. Its sclerotium has been reported to possess a wide spectrum of pharmacological activities, including free-radical scavenging, anti-viral, anti-microbial, anti-inflammatory and anticancer activities. However, the cellular and molecular mechanisms of apoptosis induction by P. cocos in human cancer cells are poorly understood. In the present study, we investigated the pro-apoptotic potential of an ethanol extract of P. cocos sclerotium (EEPC) in human leukemia U937 cells in vitro. We found that EEPC induced anti-proliferative effects in U937 cells in a concentration- and time-dependent manner, which was due to apoptotic induction, as evident from morphological changes and flow cytometric assays. EEPC-induced apoptosis of U937 cells was associated with an increase in the Bax:Bcl-2 ratio, the release of cytochrome c to the cytosol, and a decrease in the expression of an inhibitor of the apoptosis family of proteins. The events were accompanied by activation of caspase-8, -9 and -3, and cleaved poly(ADP-ribose) polymerase, suggesting the involvement of both the intrinsic and extrinsic apoptotic cascades. In addition, the overexpression of Bcl-2 caused a significant attenuation of EEPC-induced caspase activation, degradation of PARP, and the collapse of mitochondrial membrane potential, and thereby reversed EEPC-induced cell apoptosis and growth inhibition. Collectively, these data provide insights into the molecular mechanisms underlying EEPC-induced apoptosis in U937 cells, suggesting that EEPC may be a new therapeutic option for the treatment of leukemia.

CD4+VEGFR1(HIGH) T cell as a novel Treg subset regulates inflammatory bowel disease in lymphopenic mice

Regulatory T cells (Tregs) are a specialized subpopulation of T cells that control the immune response and thereby maintain immune system homeostasis and tolerance to self-antigens. Many subsets of CD4(+) Tregs have been identified, including Foxp3(+), Tr1, Th3, and Foxp3neg iT(R)35 cells. In this study, we identified a new subset of CD4(+)VEGFR1(high) Tregs that have immunosuppressive capacity. CD4(+)VEGFR1high T cells, which constitute approximately 1.0% of CD4(+) T cells, are hyporesponsive to T-cell antigen receptor stimulation. Surface marker and FoxP3 expression analysis revealed that CD4(+)VEGFR1(high) T cells are distinct from known Tregs. CD4(+)VEGFR1(high) T cells suppressed the proliferation of CD4(+)CD25(-) T cell as efficiently as CD4(+)CD25(high) natural Tregs in a contact-independent manner. Furthermore, adoptive transfer of CD4(+)VEGFR1(+) T cells from wild type to RAG-2-deficient C57BL/6 mice inhibited effector T-cell-mediated inflammatory bowel disease. Thus, we report CD4(+) VEGFR1(high) T cells as a novel subset of Tregs that regulate the inflammatory response in the intestinal tract.

RB mutation and RAS overexpression induce resistance to NK cell-mediated cytotoxicity in glioma cells

Several theories aim to explain the malignant transformation of cells, including the mutation of tumor suppressors and proto-oncogenes. Deletion of Rb (a tumor suppressor), overexpression of mutated Ras (a proto-oncogene), or both, are sufficient for in vitro gliomagenesis, and these genetic traits are associated with their proliferative capacity. An emerging hallmark of cancer is the ability of tumor cells to evade the immune system. Whether specific mutations are related with this, remains to be analyzed. To address this issue, three transformed glioma cell lines were obtained (Rb^−/−, Ras^V12, and Rb^−/−/Ras^V12) by in vitro retroviral transformation of astrocytes, as previously reported. In addition, Ras^V12 and Rb^−/−/Ras^V12 transformed cells were injected into SCID mice and after tumor growth two stable glioma cell lines were derived. All these cells were characterized in terms of Rb and Ras gene expression, morphology, proliferative capacity, expression of MHC I, Rae1δ, and Rae1αβγδε, mult1, H60a, H60b, H60c, as ligands for NK cell receptors, and their susceptibility to NK cell-mediated cytotoxicity. Our results show that transformation of astrocytes (Rb loss, Ras overexpression, or both) induced phenotypical and functional changes associated with resistance to NK cell-mediated cytotoxicity. Moreover, the transfer of cell lines of transformed astrocytes into SCID mice increased resistance to NK cell-mediated cytotoxicity, thus suggesting that specific changes in a tumor suppressor (Rb) and a proto-oncogene (Ras) are enough to confer resistance to NK cell-mediated cytotoxicity in glioma cells and therefore provide some insight into the ability of tumor cells to evade immune responses.

TAT-RasGAP317-326-mediated tumor cell death sensitization can occur independently of Bax and Bak

The increase of cancer specificity and efficacy of anti-tumoral agents are prime strategies to overcome the deleterious side effects associated with anti-cancer treatments. We described earlier a cell-permeable protease-resistant peptide derived from the p120 RasGAP protein, called TAT-RasGAP317-326, as being an efficient tumor-specific sensitizer to apoptosis induced by genotoxins in vitro and in vivo. Bcl-2 family members regulate the intrinsic apoptotic response and as such could be targeted by TAT-RasGAP317-326. Our results indicate that the RasGAP-derived peptide increases cisplatin-induced Bax activation. We found no evidence, using in particular knock-out cells, of an involvement of other Bcl-2 family proteins in the tumor-specific sensitization activity of TAT-RasGAP317-326. The absence of Bax and Bak in mouse embryonic fibroblasts rendered them resistant to cisplatin-induced apoptosis and consequently to the sensitizing action of the RasGAP-derived peptide. Surprisingly, in the HCT116 colon carcinoma cell line, the absence of Bax and Bak did not prevent cisplatin-induced apoptosis and the ability of TAT-RasGAP317-326 to augment this response. Our study also revealed that p53, while required for an efficient genotoxin-induced apoptotic response, is dispensable for the ability of the RasGAP-derived peptide to improve the capacity of genotoxins to decrease long-term survival of cancer cells. Hence, even though genotoxin-induced Bax activity can be increased by TAT-RasGAP317-326, the sensitizing activity of the RasGAP-derived peptide can operate in the absence of a functional mitochondrial intrinsic death pathway.

Competitive inhibition of survivin using a cell-permeable recombinant protein induces cancer-specific apoptosis in colon cancer model

Endogenous survivin expression has been related with cancer survival, drug resistance, and metastasis. Therapies targeting survivin have been shown to significantly inhibit tumor growth and recurrence. We found out that a cell-permeable dominant negative survivin (SurR9-C84A, referred to as SR9) competitively inhibited endogenous survivin and blocked the cell cycle at the G1/S phase. Nanoencapsulation in mucoadhesive chitosan nanoparticles (CHNP) substantially increased the bioavailability and serum stability of SR9. The mechanism of nanoparticle uptake was studied extensively in vitro and in ex vivo models. Our results confirmed that CHNP-SR9 protected primary cells from autophagy and successfully induced tumor-specific apoptosis via both extrinsic and intrinsic apoptotic pathways. CHNP-SR9 significantly reduced the tumor spheroid size (three-dimensional model) by nearly 7-fold. Effects of SR9 and CHNP-SR9 were studied on 35 key molecules involved in the apoptotic pathway. Highly significant (4.26-fold, P≤0.005) reduction in tumor volume was observed using an in vivo mouse xenograft colon cancer model. It was also observed that net apoptotic (6.25-fold, P≤0.005) and necrotic indexes (3.5-fold, P≤0.05) were comparatively higher in CHNP-SR9 when compared to void CHNP and CHNP-SR9 internalized more in cancer stem cells (4.5-fold, P≤0.005). We concluded that nanoformulation of SR9 did not reduce its therapeutic potential; however, nanoformulation provided SR9 with enhanced stability and better bioavailability. Our study presents a highly tumor-specific protein-based cancer therapy that has several advantages over the normally used chemotherapeutics.

Cancer-type-specific crosstalk between autophagy, necroptosis and apoptosis as a pharmacological target

Cell death plays an essential role in the development of organs, homeostasis, and cancer. Apoptosis and programmed necrosis are two major types of cell death, characterized by different cell morphology and pathways. Accumulating evidence shows autophagy as a new alternative target to treat tumor resistance. Besides its well-known pro-survival role, autophagy can be a physiological cell death process linking apoptosis and programmed necrosis cell death pathways, by various molecular mediators. Here, we summarize the effects of pharmacologically active compounds as modulators of different types of cancer cell death depending on the cellular context. Indeed, current findings show that both natural and synthetic compounds regulate the interplay between apoptosis, autophagy and necroptosis stimulating common molecular mediators and sharing common organelles. In response to specific stimuli, the same death signal can cause cells to switch from one cell death modality to another depending on the cellular setting. The discovery of important interconnections between the different cell death mediators and signaling pathways, regulated by pharmacologically active compounds, presents novel opportunities for the targeted treatment of cancer. The aim of this review is to highlight the potential role of these compounds for context-specific anticancer therapy.

Stem Cell-Based Therapies for Cancer

Stem cell-based therapeutic strategies have emerged as very attractive treatment options over the past decade. Stem cells are now being utilized as delivery vehicles especially in cancer therapy to deliver a number of targeted proteins and viruses. This chapter aims to shed light on numerous studies that have successfully employed these strategies to target various cancer types with a special emphasis on numerous aspects that are critical to the success of future stem cell-based therapies for cancer.

Expression of Fas (CD95/APO-1) and Fas ligand (FasL) in experimentally-induced acute pancreatitis

INTRODUCTION

Acinar cell death is a crucial event in acute pancreatitis (AP) and may occur either by apoptosis or necrosis. The aim of this study was to investigate the expression of the apoptosis associated proteins Fas and FasL in experimentally induced severe AP.

METHODS

AP was induced in 30 rats by injecting 0.2 ml of 4.5% sodium taurocholate solution into the biliopancreatic duct. Sham operated animals (n = 30) and 10 normal controls were used for comparisons. Animals were killed at 6, 12, 24, 48, 72 hr and 1 week after operation (five animals at each time point) and both serum and pancreatic tissue were obtained. The severity of AP was graded by morphological evaluation and by measuring serum amylase levels. Acinar cell apoptosis was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay. Tissue expressions of Fas and FasL were evaluated by immunohistochemistry.

RESULTS

Sodium taurocholate injection resulted in severe acute necrotizing pancreatitis as early as six hr after taurocholate infusion with gradually increasing severity and a peak at 72 hr, and a significant increase of serum amylase at 6 and 12 hr. Apoptotic acinar cells were observed between 48 and 72 hr. The expression of both Fas and FasL in pancreatic tissue was induced in comparison with normal controls. Fas expression in AP was higher and statistically significant at 24 hr whereas FasL expression was consistently lower with a statistical significance observed at 12 hr when compared to sham-operated animals suggesting Fas upregulation and FasL downregulation in this model of AP.

CONCLUSIONS

Induction and sequential changes in the expressions of Fas and FasL occur during taurocholate induced severe AP in rats and their temporal modulation might associate with acinar cell death by apoptosis.

Sensitization of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant primary prostate cancer cells by isoegomaketone from Perilla frutescens

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is currently in clinical trials as a cancer treatment due to its ability to induce apoptosis selectively in cancer cells. Nevertheless, the risk of developing resistance warrants the development of sensitizers that can overcome resistance to TRAIL. In this study, isoegomaketone (1) acted as a synergistic TRAIL sensitizer by mediating up-regulation of DR5 expression in primary prostate cancer RC-58T/h/SA#4 cells. Combined with 1, TRAIL exhibited enhanced apoptotic activity in a human prostate cancer cell line designated RC-58T/h/SA#4, as indicated by increases in annexin V-positive and sub-G1 cell populations as well as condensation of chromatin or apoptotic bodies. Combined treatment also activated caspases-8, -9, and -3; increased the protein levels of Bax, AIF, and cytosolic cytochrome c; and induced PARP cleavage while reducing Bcl-2 protein expression. Human recombinant DR5 Fc chimera efficiently attenuated 1-induced apoptosis, thereby demonstrating the critical role of DR5 in 1-mediated apoptotic cell death. Furthermore, DR5 expression induced by 1 was mediated via a ROS-independent pathway that required CHOP and p53. Overall, these findings provide evidence that 1 potentiates TRAIL-mediated apoptosis through up-regulation of DR5 via a ROS-independent pathway. This suggests that 1 has potential for increasing the effectiveness of prostate cancer therapy with TRAIL.

The Anticancer Properties and Apoptosis-inducing Mechanisms of Cinnamaldehyde and the Herbal Prescription Huang-Lian-Jie-Du-Tang ( Huáng Lián Jiě Dú Tang) in Human Hepatoma Cells

Hepatocellular carcinoma (HCC) has long been one of the most important causes of cancer mortality in the world. Many natural products and traditional herbal medicines have been used to treat HCC in Asian countries such as Japan, Korea, Taiwan, and China. The present review aims to describe the anticancer properties and apoptotic mechanisms of cinnamaldehyde, the bioactive ingredient isolated from cinnamon trees, and the herbal prescription Huang-Lian-Jie-Du-Tang (黃連解毒湯 Huáng Lián Jiě Dú Tang; HLJDT) against human hepatoma cells in vitro and in vivo. Implication of their treatment for the development of targeted therapy against HCC is discussed.

Tazarotene induces apoptosis in human basal cell carcinoma via activation of caspase-8/t-Bid and the reactive oxygen species-dependent mitochondrial pathway

Previous studies suggest that tazarotene, a new member of the acetylenic class of RARβ/γ selective retinoids which is approved to treat a variety of skin diseases, exhibits an anti-proliferative effect in human basal cell carcinoma (BCC) by triggering caspase-dependent apoptosis. However, the detailed molecular mechanisms underlying the anti-tumor activity of tazarotene are poorly understood. This study aims at investigating the molecular mechanisms of tazarotene-induced apoptosis in human BCC cells. Our results are the first to demonstrate that tazarotene induces mitochondria-dependent cleavage of caspase-9 and -3 and PARP in BCC cells by producing reactive oxygen species (ROS) and activating caspase-8 through both ROS and death receptor signaling. These events are accompanied by a decrease in BCL-2 and BCL-xl anti-apoptotic proteins as well as by survivin and XIAP, two IAP family members. Furthermore, our results presented for the first time that tazarotene triggers a convergence of the intrinsic and extrinsic apoptotic pathways via the caspase-8-truncated Bid signaling pathway. Collectively, these data provide insights into the molecular mechanisms underlying tazarotene-induced apoptosis in human BCC cells, suggesting that this compound is a potential anti-skin cancer drug.

Development of TRAIL resistance by radiation-induced hypermethylation of DR4 CpG island in recurrent laryngeal squamous cell carcinoma

PURPOSE

There are limited therapeutic options for patients with recurrent head and neck cancer after radiation therapy failure. To assess the use of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as a salvage chemotherapeutic agent for recurrent cancer after radiation failure, we investigated the effect of clinically relevant cumulative irradiation on TRAIL-induced apoptosis.

METHODS AND MATERIALS

Using a previously established HN3 cell line from a laryngeal carcinoma patient, we generated a chronically irradiated HN3R isogenic cell line. Viability and apoptosis in HN3 and HN3R cells treated with TRAIL were analyzed with MTS and PI/annexin V-FITC assays. Western blotting and flow cytometry were used to determine the underlying mechanism of TRAIL resistance. DR4 expression was semiquantitatively scored in a tissue microarray with 107 laryngeal cancer specimens. Methylation-specific polymerase chain reaction and bisulfite sequencing for DR4 were performed for genomic DNA isolated from each cell line.

RESULTS

HN3R cells were more resistant than HN3 cells to TRAIL-induced apoptosis because of significantly reduced levels of the DR4 receptor. The DR4 staining score in 37 salvage surgical specimens after radiation failure was lower in 70 surgical specimens without radiation treatment (3.03 ± 2.75 vs 5.46 ± 3.30, respectively; P<.001). HN3R cells had a methylated DR4 CpG island that was partially demethylated by the DNA demethylating agent 5-aza-2'-deoxycytidine.

CONCLUSION

Epigenetic silencing of the TRAIL receptor by hypermethylation of a DR4 CpG island might be an underlying mechanism for TRAIL resistance in recurrent laryngeal carcinoma treated with radiation.

Interaction of dietary fatty acids with tumour necrosis factor family cytokines during colon inflammation and cancer

Intestinal homeostasis is precisely regulated by a number of endogenous regulatory molecules but significantly influenced by dietary compounds. Malfunction of this system may result in chronic inflammation and cancer. Dietary essential n-3 polyunsaturated fatty acids (PUFAs) and short-chain fatty acid butyrate produced from fibre display anti-inflammatory and anticancer activities. Both compounds were shown to modulate the production and activities of TNF family cytokines. Cytokines from the TNF family (TNF- α, TRAIL, and FasL) have potent inflammatory activities and can also regulate apoptosis, which plays an important role in cancer development. The results of our own research showed enhancement of apoptosis in colon cancer cells by a combination of either docosahexaenoic acid (DHA) or butyrate with TNF family cytokines, especially by promotion of the mitochondrial apoptotic pathway and modulation of NF κ B activity. This review is focused mainly on the interaction of dietary PUFAs and butyrate with these cytokines during colon inflammation and cancer development. We summarised recent knowledge about the cellular and molecular mechanisms involved in such effects and outcomes for intestinal cell behaviour and pathologies. Finally, the possible application for the prevention and therapy of colon inflammation and cancer is also outlined.

Are all granzymes cytotoxic in vivo?

Granzymes are serine proteases mainly found in cytotoxic lymphocytes. The most-studied member of this group is granzyme B, which is a potent cytotoxin that has set the paradigm that all granzymes are cyototoxic. In the last 5 years, this paradigm has become controversial. On one hand, there is a plethora of sometimes contradictory publications showing mainly caspase-independent cytotoxic effects of granzyme A and the so-called orphan granzymes in vitro. On the other hand, there are increasing numbers of reports of granzymes failing to induce cell death in vitro unless very high (potentially supra-physiological) concentrations are used. Furthermore, experiments with granzyme A or granzyme M knock-out mice reveal little or no deficit in their cytotoxic lymphocytes’ killing ability ex vivo, but indicate impairment in the inflammatory response. These findings of non-cytotoxic effects of granzymes challenge dogma, and thus require alternative or additional explanations to be developed of the role of granzymes in defeating pathogens. Here we review evidence for granzyme cytotoxicity, give an overview of their non-cytotoxic functions, and suggest technical improvements for future investigations.

Lipid rafts and Fas/FasL pathway may involve in elaidic acid-induced apoptosis of human umbilical vein endothelial cells

Our previous study showed that trans-fatty acids can cause apoptosis of endothelial cells through the caspase pathway and the mitochondrial pathway. The objective of this study was to explore how trans-fatty acids activate the caspase pathway, whether there exist specific receptors induced apoptosis by comparing normal cells and non-rafts cells treated with elaidic acid (9t18:1) and oleic acid (9c18:1), respectively. Compared to normal cells treated with 9t18:1, the cell viability increased by 13% and the number of apoptotic cells decreased by 3% in non-rafts cells treated with 9t18:1 (p < 0.05), and the expression levels of pro-apoptotic proteins such as caspase-3, -8, -9, Bax, and Bid decreased, and expression of antiapoptotic protein Bcl-2 increased (p < 0.05). In addition, Fas/FasL expression in cell membrane decreased significantly (p < 0.05). In conclusion, the lipid rafts and Fas/FasL pathway may involve in 9t18:1-induced apoptosis of human umbilical vein endothelial cells.

Novel treatment option for MUC16-positive malignancies with the targeted TRAIL-based fusion protein Meso-TR3

Background

The targeted delivery of cancer therapeutics represents an ongoing challenge in the field of drug development. TRAIL is a promising cancer drug but its activity profile could benefit from a cancer-selective delivery mechanism, which would reduce potential side effects and increase treatment efficiencies. We recently developed the novel TRAIL-based drug platform TR3, a genetically fused trimer with the capacity for further molecular modifications such as the addition of tumor-directed targeting moieties. MUC16 (CA125) is a well characterized biomarker in several human malignancies including ovarian, pancreatic and breast cancer. Mesothelin is known to interact with MUC16 with high affinity. In order to deliver TR3 selectively to MUC16-expressing cancers, we investigated the possibility of targeted TR3 delivery employing the high affinity mesothelin/MUC16 ligand/receptor interaction.

Methods

Using genetic engineering, we designed the novel cancer drug Meso-TR3, a fusion protein between native mesothelin and TR3. The recombinant proteins were produced with mammalian HEK293T cells. Meso-TR3 was characterized for binding selectivity and killing efficacy against MUC16-positive cancer cells and controls that lack MUC16 expression. Drug efficacy experiments were performed in vitro and in vivo employing an intraperitoneal xenograft mouse model of ovarian cancer.

Results

Similar to soluble mesothelin itself, the strong MUC16 binding property was retained in the Meso-TR3 fusion protein. The high affinity ligand/receptor interaction was associated with a selective accumulation of the cancer drug on MUC16-expressing cancer targets and directly correlated with increased killing activity in vitro and in a xenograft mouse model of ovarian cancer. The relevance of the mesothelin/MUC16 interaction for attaching Meso-TR3 to the cancer cells was verified by competitive blocking experiments using soluble mesothelin. Mechanistic studies using soluble DR5-Fc and caspase blocking assays confirmed engagement of the extrinsic death receptor pathway. Compared to non-targeted TR3, Meso-TR3 displayed a much reduced killing potency on cells that lack MUC16.

Conclusions

Soluble Meso-TR3 targets the cancer biomarker MUC16 in vitro and in vivo. Following attachment to the tumor via surface bound MUC16, Meso-TR3 acquires full activation with superior killing profiles compared to non-targeted TR3, while its bioactivity is substantially reduced on cells that lack the tumor marker. This prodrug phenomenon represents a highly desirable property because it has the potential to enhance cancer killing with fewer side-effects than non-targeted TRAIL-based therapeutics. Thus, further exploration of this novel fusion protein is warranted as a possible therapeutic for patients with MUC16-positive malignancies.

Inhibitor of apoptosis proteins as targets for anticancer therapy

Cell death by apoptosis plays a critical role in regulating the subtle balance between cell death and proliferation to maintain tissue homeostasis. Accordingly, tipping the balance in either direction may cause human disease. Too little cell death may promote tumor formation and progression. In addition, killing of cancer cells by current therapies is largely due to induction of apoptosis in tumor cells. Since a hallmark of human cancers is their resistance to apoptosis, there is a demand to develop novel strategies that restore the apoptotic machinery in order to overcome cancer resistance. Inhibitor of apoptosis proteins (IAPs) block apoptosis at the core of the apoptotic machinery by inhibiting caspases. Elevated levels of IAPs are found in many human cancers and have been associated with poor prognosis. Recent insights into the role of IAPs have provided the basis for various exciting developments that aim to modulate the expression or function of IAPs in human cancers. Targeting IAPs (e.g., by antisense approaches or small-molecule inhibitors) presents a promising novel approach to either directly trigger apoptosis or to potentiate the efficacy of cytotoxic therapies in cancer cells. Thus, inhibition of IAPs such as X chromosome-linked IAP may prove to be a successful strategy to overcome apoptosis resistance of human cancers that deserves further exploitation.

Granzyme M: behind enemy lines

The granule-exocytosis pathway is the major mechanism via which cytotoxic lymphocytes eliminate virus-infected and tumor cells. In this pathway, cytotoxic lymphocytes release granules containing the pore-forming protein perforin and a family of serine proteases known as granzymes into the immunological synapse. Pore-formation by perforin facilitates entry of granzymes into the target cell, where they can activate various (death) pathways. Humans express five different granzymes, of which granzymes A and B have been most extensively characterized. However, much less is known about granzyme M (GrM). Recently, structural analysis and advanced proteomics approaches have determined the primary and extended specificity of GrM. GrM functions have expanded over the past few years: not only can GrM efficiently induce cell death in tumor cells, it can also inhibit cytomegalovirus replication in a noncytotoxic manner. Finally, a role for GrM in lipopolysaccharide-induced inflammatory responses has been proposed. In this review, we recapitulate the current status of GrM expression, substrate specificity, functions, and inhibitors.

Modulation of cyclins, p53 and mitogen-activated protein kinases signaling in breast cancer cell lines by 4-(3,4,5-trimethoxyphenoxy)benzoic acid

Despite the advances in cancer therapy and early detection, breast cancer remains a leading cause of cancer-related deaths among females worldwide. The aim of the current study was to investigate the antitumor activity of a novel compound, 4-(3,4,5-trimethoxyphenoxy)benzoic acid (TMPBA) and its mechanism of action, in breast cancer. Results indicated the relatively high sensitivity of human breast cancer cell-7 and MDA-468 cells towards TMPBA with IC₅₀ values of 5.9 and 7.9 μM, respectively compared to hepatocarcinoma cell line Huh-7, hepatocarcinoma cell line HepG2, and cervical cancer cell line Hela cells. Mechanistically, TMPBA induced apoptotic cell death in MCF-7 cells as indicated by 4′,6-diamidino-2-phenylindole (DAPI) nuclear staining, cell cycle analysis and the activation of caspase-3. Western blot analysis revealed the ability of TMPBA to target pathways mediated by mitogen-activated protein (MAP) kinases, 5′ adenosine monophosphate-activated protein kinase (AMPK), and p53, of which the concerted action underlined its antitumor efficacy. In addition, TMPBA induced alteration of cyclin proteins’ expression and consequently modulated the cell cycle. Taken together, the current study underscores evidence that TMPBA induces apoptosis in breast cancer cells via the modulation of cyclins and p53 expression as well as the modulation of AMPK and mitogen-activated protein kinases (MAPK) signaling. These findings support TMPBA’s clinical promise as a potential candidate for breast cancer therapy.

Antitumor mechanisms of amino Acid hydroxyurea derivatives in the metastatic colon cancer model

The paper presents a detailed study of the biological effects of two amino acid hydroxyurea derivatives that showed selective antiproliferative effects in vitro on the growth of human tumor cell line SW620. Tested compounds induced cell cycle perturbations and apoptosis. Proteins were identified by proteomics analyses using two-dimensional gel electrophoresis coupled to mass spectrometry, which provided a complete insight into the most probable mechanism of action on the protein level. Molecular targets for tested compounds were analyzed by cheminformatics tools. Zinc-dependent histone deacetylases were identified as potential targets responsible for the observed antiproliferative effect.

Evaluation of the BH3-only protein Puma as a direct Bak activator

Interactions among Bcl-2 family proteins play critical roles in cellular life and death decisions. Previous studies have established the BH3-only proteins Bim, tBid, and Noxa as "direct activators" that are able to directly initiate the oligomerization and activation of Bak and/or Bax. Earlier studies of Puma have yielded equivocal results, with some concluding that it also acts as a direct activator and other studies suggesting that it acts solely as a sensitizer BH3-only protein. In the present study we examined the interaction of Puma BH3 domain or full-length protein with Bak by surface plasmon resonance, assessed Bak oligomerization status by cross-linking followed by immunoblotting, evaluated the ability of the Puma BH3 domain to induce Bak-mediated permeabilization of liposomes and mitochondria, and determined the effect of wild type and mutant Puma on cell viability in a variety of cellular contexts. Results of this analysis demonstrate high affinity (KD = 26 ± 5 nM) binding of the Puma BH3 domain to purified Bak ex vivo, leading to Bak homo-oligomerization and membrane permeabilization. Mutations in Puma that inhibit (L141E/M144E/L148E) or enhance (M144I/A145G) Puma BH3 binding to Bak also produce corresponding alterations in Bak oligomerization, Bak-mediated membrane permeabilization and, in a cellular context, Bak-mediated killing. Collectively, these results provide strong evidence that Puma, like Bim, Noxa, and tBid, is able to act as a direct Bak activator.

Potentiation of cytotoxicity of paclitaxel in combination with Cl-IB-MECA in human C32 metastatic melanoma cells: A new possible therapeutic strategy for melanoma

Metastatic melanoma monotherapies with drugs such as dacarbazine, cisplatin or paclitaxel (PXT) are associated with significant toxicity and low efficacy rates. These facts reinforce the need for development of novel agents or combinatory strategies. Cl-IB-MECA is a small molecule, orally bioavailable, well tolerated and currently under clinical trials as an anticancer agent. Our aim was to investigate a possible combinatory therapeutic strategy using PXT and Cl-IB-MECA on human C32 melanoma cells and its underlying mechanisms. Cytotoxicity was evaluated using MTT reduction, lactate dehydrogenase leakage and neutral red uptake assays, for different concentrations and combinations of both agents, at 24 and 48 h. Apoptosis was also assessed using fluorescence microscopy and through the evaluation of caspases 8, 9, and 3 activities. We demonstrated, for the first time, that combination of PXT and Cl-IB-MECA significantly increases cytotoxicity for clinically relevant concentrations. This combination seems to act synergistically in disrupting membrane integrity, but also causing lysosomal and mitochondrial dysfunction. When using the lowest PTX concentration (10 ng/mL), co-incubation with CI-IB-MECA (micromolar concentrations) potentiated overall cytotoxic effects and morphological signs of apoptosis. All combinations studied enhanced caspase 8, 9, and 3 activities, suggesting the involvement of both intrinsic and extrinsic apoptotic pathways. The possibility that cytotoxicity elicited by Cl-IB-MECA, alone or in combination with PXT, involves adenosine receptor activation was discarded and results confirmed that oxidative stress is only involved in cytotoxicity after treatment with PXT, alone. Being melanoma a very apoptosis-resistance cancer, this combination seems to hold promise as a new therapeutic strategy for melanoma.

The prognostic value of the apoptosis pathway in colorectal cancer: a review of the literature on biomarkers identified by immunohistochemistry

Research towards biomarkers that predict patient outcome in colorectal cancer (CRC) is rapidly expanding. However, none of these biomarkers have been recommended by the American Association of Clinical Oncology or the European Group on Tumor Markers. Current staging criteria result in substantial under-and over-treatment of CRC patients. Evasion of apoptosis, a characteristic feature of tumorigenesis, is known to correlate with patient outcome. We reviewed the literature on immunohistochemistry-based studies between 1998 and 2011 describing biomarkers in this pathway in CRC and identified 26 markers. Most frequently described were p53, Bcl-2, survivin, and the Fas and TRAILR1 receptors and their ligands. None of the studies reviewed provided sufficient support for implementing a single marker into current clinical practice. This is likely due to the complex biology of this pathway. We suggest focusing on the combination of key markers within the apoptosis pathway that together represent an ‘apoptotic tumor profile’, which better reflects the status of this pathway in a tumor.

Phosphanegold(I) dithiocarbamates, R3PAu[SC(=S)N((i)Pr)CH2CH2OH] for R = Ph, Cy and Et: role of phosphane-bound R substituents upon in vitro cytotoxicity against MCF-7R breast cancer cells and cell death pathways

The synthesis and characterisation of R3PAu[S2CN((i)Pr)CH2CH2OH], for R = Ph (1), Cy (2) and Et (3)4, is reported. Compounds 1-3 are cytotoxic against the doxorubicin-resistant breast cancer cell line, MCF-7R, with 1 exhibiting greater potency and cytotoxicity than either of doxorubicin and cisplatin. Based on human apoptosis PCR-array analysis, caspase activities, DNA fragmentation, cell apoptotic assays, intracellular reactive oxygen species (ROS) measurements and human topoisomerase I inhibition, induction of apoptosis by 1, and necrosis by 2 and 3, are demonstrated, by both extrinsic and intrinsic pathways. Compound 1 activates the p53 gene, 2 activates only the p73 gene, whereas 3 activates both the p53 and p73 genes. Compounds 1 and 3 activate NF-κB, and each inhibits topoisomerase I.

Death receptor-ligand systems in cancer, cell death, and inflammation

The discovery of tumor necrosis factor (TNF) marked the beginning of one of the most fascinating journeys in modern biomedical research. For the moment, this journey has culminated in the development of drugs that inhibit TNF. TNF blockers have revolutionized the treatment of many chronic inflammatory diseases. Yet, the journey seems far from over. TNF is the founding member of a family of cytokines with crucial functions in cell death, inflammation, and cancer. Some of these factors, most prominently TNF, CD95L, and TRAIL, can induce cell death. The receptors that mediate this signal are therefore referred to as death receptors, even though they also activate other signals. Here I will take you on a journey into the discovery and study of death receptor-ligand systems and how this inspired new concepts in cancer therapy and our current understanding of the interplay between cell death and inflammation.

Down-regulation of RIP1 by 2-deoxy-D-glucose sensitizes breast cancer cells to TRAIL-induced apoptosis

TNF-related apoptosis-inducing ligand (TRAIL) appears to be a promising anticancer agent as it specifically kills a wide variety of cancer cells. However, resistance of subpopulations of cancer cells to TRAIL-induced cell death remains a major obstacle for successful treatment of cancer using TRAIL-based therapy. In this report we show that the hexokinase inhibitor 2-deoxy-d-glucose (2-DG) efficiently enhances TRAIL-induced apoptosis through downregulation of receptor-interacting protein kinase 1 (RIP1) in breast cancer cells. Although 2-DG alone did not kill breast cancer cells, it sensitized the cells to TRAIL-induced cell death. This could be efficiently inhibited by blockage of the caspase cascade, suggesting 2-DG augments TRAIL-mediated apoptotic signaling. Indeed, treatment with 2-DG resulted in upregulation of TRAIL receptor 2 (TRAIL-R2), downregulation of cIAP1 and XIAP, and reduction in RIP1. The latter appeared to play an important role in regulating sensitivity of breast cancer cells to TRAIL, in that knockdown of RIP1 recapitulated, at least in part, the effect of 2-DG on TRAIL-induced apoptosis. Taken together, these results indicate that 2-DG enhances TRAIL-induced apoptosis in breast cancer cells by multiple mechanisms including suppression of RIP1, and highlight the potential therapeutic benefit of combinations of 2-DG and TRAIL in the treatment of breast cancer.

5-Azacytidine induces early stage apoptosis and promotes in vitro maturation by changing chromosomal construction in murine oocytes

As an anticancer drug, 5-azacytidine (5-AzaC) has been widely used to treat various cancers. To investigate the effect of 5-AzaC on mouse oocytes cultured in vitro, we have performed morphological and molecular biology studies to examine the behavior of chromosomes and oocyte development. In 5-AzaC-treated oocytes, chromosomes were decondensed and unstable. The mRNA levels of Caspase3, Caspase8, and Caspase9 increased with the occurrence of early stage apoptosis in oocytes following 5-AzaC treatment. Furthermore, the mRNA levels of Gdf9 and Bmp15 also increased with the corresponding morphological changes in 5-AzaC-treated oocytes. In conclusion, 5-AzaC not only induced early apoptosis through both extrinsic and intrinsic pathways, but also had a positive effect on the developmental competence of mouse oocytes during in vitro maturation. These effects may be due to changes in chromosomal construction induced by DNA hypomethylation.

Raloxifene inhibits growth of RT4 urothelial carcinoma cells via estrogen receptor-dependent induction of apoptosis and inhibition of proliferation

Bladder cancer is the fifth most common type of cancer in the USA, with over 70,000 new cases diagnosed each year. Treatment often involves invasive surgical therapies, as chemotherapy alone is often ineffective and associated with high recurrence rates. Identification of estrogen receptor-β (ERβ) in up to 75 % of urinary tumors raises the question of whether this receptor could be targeted to effectively treat bladder cancer. In this study, a panel of five bladder cancer cell lines representing a variety of disease stage and grades were treated with the antiestrogens 4-hydroxytamoxifen, raloxifene, or the pure antagonist ICI 182,780. All cell lines were ERβ positive while only a few expressed estrogen receptor-α (ERα). Notably, all but the TCCSUP cell line were growth inhibited 20-100 % by at least two antiestrogens. Using RT4 cells, we demonstrate that growth inhibition by raloxifene is ER dependent and either ERα or ERβ can mediate this response. Activation of caspase-3 and its effector poly-ADP ribose polymerase (PARP) demonstrate that raloxifene-induced growth inhibition is in part the result of increased apoptosis; this PARP cleavage was ER dependent. Moreover, changes in the expression of cell cycle genes indicate that cell proliferation is also affected. Specifically, raloxifene treatment results in the stabilization of p27 protein, likely via the downregulation of S-phase kinase-associated protein (SKP2). Expression of the negative cell cycle regulator B-cell translocation gene (BTG2) is also increased, while cyclin D1 transcription is reduced. These results indicate that antiestrogens may be useful therapeutics in the treatment of bladder cancer by targeting ER and inhibiting growth via multiple mechanisms.

Treatment of malignant melanoma by downregulation of XIAP and overexpression of TRAIL with a conditionally replicating oncolytic adenovirus

BACKGROUND AND AIM

Currently available systemic therapies for malignant melanoma produce low response rates in patients, and more effective treatment modalities are clearly needed. The tumor necrosis factor (TNF)- related apoptosis-inducing ligand has a significant impact on therapy for patients with X-linked inhibitor of apoptosis protein-downregulation malignant melanoma. The primary objective of this study was to assess its therapeutic potential.

MATERIALS AND METHODS

We employed a conditionally replicating oncolytic adenoviral vector, named CRAd5.TRAIL/siXIAP, with the characteristics of over-expression of the therapeutic gene TRAIL and downregulation of XIAP in one vector. B16F10-luc cells were employed to detect anti-tumor activity of CRAd5.TRAIL/siXIAP in vitro and in vivo.

RESULTS

CRAd5.TRAIL/siXIAP enhanced caspase-8 activation and caspase-3 maturation in B16F10 cells in vitro. Furthermore, it more effectively infected and killed melanoma cells in vitro and in vivo than other adenoviruses.

CONCLUSION

Taken together, the combination of upregulation of TRAIL and downregulation of siXIAP with one oncolytic adenoviral vector holds promise for development of an effective therapy for melanomas and other common cancers.

Anacardic acid induces mitochondrial-mediated apoptosis in the A549 human lung adenocarcinoma cells

Anacardic acid (AA) is a constituent of the cashew nut shell and is known as an inhibitor of nuclear factor-κB (NF-κB). We investigated the cytotoxicity of AA on cancer cells and more experiments to reveal the cell death mechanism focused on A549 lung adenocarcinoma cells for our interest in lung cancer. To examine the molecular mechanism of cell death in AA treated A549 cells, we performed experiments such as transmission electron microscopy (TEM), western blot analysis, fluorescence-activated cell sorting (FACS), genomic DNA extraction and staining with 4',6-diamidino-2-phenylindole (DAPI). For the first time we revealed that AA induces caspase-independent apoptosis with no inhibition of cytotoxicity by pan-caspase inhibitor, Z-VAD-fmk, in A549 cells. Our results showed the possibility of mitochondrial-mediated apoptosis through the activation of apoptosis-inducing factor (AIF) and an intrinsic pathway executioner such as cytochrome c. This study will be helpful in revealing the cell death mechanisms and in developing potential drugs for lung cancer using AA.

Sub-toxic dose of apigenin sensitizes HepG2 cells to TRAIL through ERK-dependent up-regulation of TRAIL receptor DR5

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is regarded as a promising candidate for anticancer therapy due to its selective toxicity to cancer cells. Nevertheless, because of TRAIL resistance in some cancer cells, combined treatment with sensitizing agents is required to enhance the anticancer potential of TRAIL. In this study, we investigated the underlying mechanism of apigenin-induced sensitization of HepG2 cells to TRAIL-induced cell death. Synergistic induction of apoptosis by combination was confirmed by examining the typical morphology changes of apoptosis, PARP-cleavage, and activation of effector caspases. Z-VAD-fmk, a pan-caspase inhibitor, inhibited the enhanced cell death by combined treatment of apigenin and TRAIL, demonstrating that a caspase-dependent pathway is involved in apigenin/TRAIL-mediated apoptosis. In addition, we found that apigenin/ TRAIL co-treatment up-regulates DR5 cell surface expression. The synergistic induction of cell death by the apigenin/ TRAIL combination was significantly attenuated by DR5 blocking chimera antibody. Next, using pharmacological inhibitors, we found that ERK activation is involved in the induction of DR5 expression. Inhibition of ERK1/2 by U0126 significantly decreased the apigenin/TRAIL-induced DR5 expression and apoptosis. Taken together, our results indicate that apigenin can enhance the apoptotic effect of TRAIL via ERK-induced up-regulation of DR5.

New frontiers in promoting tumour cell death: targeting apoptosis, necroptosis and autophagy

Cancer is a multifaceted disease comprising a combination of genetic, metabolic and signalling aberrations, which severely disrupt the normal homeostasis of cell growth and death. Many oncogenic events while promoting tumour development also increase the sensitivity of cells to cell death stimuli including chemotherapeutic drugs. As a result, tumour cells often acquire the ability to evade death by inactivating cell death pathways that normally function to eliminate damaged and harmful cells. The impairment of cell death function is also often the reason for the development of chemotherapeutic resistance encountered during treatment. It is therefore necessary to achieve a comprehensive understanding of existing cell death pathways and the relevant regulatory components involved, with the intention of identifying new strategies to kill cancer cells. This review provides an insightful overview of the common forms of cell death signalling pathways, the interactions between these pathways and the ways in which these pathways are deregulated in cancer. We also discuss the emerging therapies targeted at activating or restoring cell death pathways to induce tumour cell death, which are currently being tested in clinical trials.

PEG-liposomal oxaliplatin induces apoptosis in human colorectal cancer cells via Fas/FasL and caspase-8

Since cellular uptake of PEG [poly(ethylene glycol)]-liposomal L-OHP (oxaliplatin) induces bioactive changes in CRC (colorectal cancer), we have investigated its apoptotic effect and anticancer mechanism. Human CRC SW480 cells were treated with PEG-liposomal L-OHP and a caspase-8 inhibitor [Z-IETD-FMK (benzyloxycarbonyl-Ile-Glu-Thr-dl-Asp-fluoromethylketone)]. Apoptosis was measured by FCM (flow cytometry) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. Expression of Fas/FasL and cytochrome c was detected using FCM and an immunofluorescence assay. Expression of caspase-8, Bid, caspase-9, caspase-7 and activated caspase-3 (P17) was examined by Western blot analyses. The results indicated that PEG-liposomal L-OHP (28 μg/ml L-OHP) induced marked apoptosis in SW480 cells compared with 28 μg/ml free L-OHP. The expression levels of Fas, FasL, cytochrome c, caspase-9, caspase-7 and activated caspase-3 proteins were up-regulated, with a corresponding increase in apoptosis; however, expression of caspase-8 and Bid were down-regulated as apoptosis increased. When cells were treated with Z-IETD-FMK, apoptosis was inhibited, but there was little impact on the expression of Fas, FasL, cytochrome c, Bid, caspase-9, caspase-7 and activated caspase-3. These findings indicate that PEG-liposomal L-OHP enhances the anticancer potency of the chemotherapeutic agent; moreover, Fas/FasL and caspase-8 signalling pathways play a key role in mediating PEG-liposomal L-OHP-induced apoptosis.

Apoptotic cell death by the novel natural compound, cinobufotalin

Cinobufotalin (CB), one of the bufadienolides prepared from toad venom, was investigated for its cytotoxicity, and the underneath mechanism involved. We primarily utilized DNA fragmentation assay and microscopic observation to assess the effect of various doses of CB in human lymphoma U937 cells. Following that, we investigated other parameters involved in cell death mechanism such as reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and apoptotic proteins activation. HeLa cells were concomitantly used to generalize the data observed. Our results show that CB caused significant DNA fragmentation, decrease of MMP, and an increase in the intracellular Ca(2+) ion and ROS production. In addition, CB induced upregulation of Fas protein, proteolytic activation of cytochrome c, caspase-2, -3, -8 and -9 together with the activation of Bid and Bax. Our findings were further validated using either Fas/FasL antagonist or pan-caspase inhibitor to significantly inhibit CB-induced DNA fragmentation. In our study, we suggest that CB induces caspase dependent cell death in U937 cells, and that Fas plays a role in CB-induced apoptosis. Altogether, our data provides novel insights of the mechanism of action of CB and its potential as a future chemotherapeutic agent.

Mesenchymal stem cells engineered for cancer therapy

Recent pre-clinical and clinical studies have shown that stem cell-based therapies hold tremendous promise for the treatment of human disease. Mesenchymal stem cells (MSC) are emerging as promising anti-cancer agents which have an enormous potential to be utilized to treat a number of different cancer types. MSC have inherent tumor-trophic migratory properties, which allows them to serve as vehicles for delivering effective, targeted therapy to isolated tumors and metastatic disease. MSC have been readily engineered to express anti-proliferative, pro-apoptotic, anti-angiogenic agents that specifically target different cancer types. Many of these strategies have been validated in a wide range of studies evaluating treatment feasibility or efficacy, as well as establishing methods for real-time monitoring of stem cell migration in vivo for optimal therapy surveillance and accelerated development. This review aims to provide an in depth status of current MSC-based cancer therapies, as well as the prospects for their clinical translation.

Neuroprotection of co-activation of GABA receptors by preventing caspase-3 denitrosylation in KA-induced seizures

Previous studies have demonstrated that kainic acid (KA)-induced seizures can cause the enhancement of excitation and lead to neuronal death in rat hippocampus. Co-activation of the inhibitory GABA receptors can attenuate the excitatory JNK3 apoptotic signaling pathway via inhibiting the increased assembly of the GluR6-PSD-95-MLK3 signaling module induced by KA in epileptic rat hippocampal CA1 and CA3 regions. Caspase-3 is a cysteine protease located in both the cytoplasm and mitochondrial intermembrane space that is a central effector of many apoptotic pathways. We designed experiments to elucidate the underlying molecular mechanisms of procaspase-3 activation and neuroprotection of co-activation of GABA receptors against neuronal death induced by KA. In this study, we show that co-activation of GABA receptors can attenuate the Fas/FasL apoptotic signaling pathway and inhibit the increased of thioredoxin reductase activity induced by KA, subsequently inhibit the activation of procaspase-3 by diminishing the denitrosylation of its active-site thiol and decreasing the cleavage of the caspase-3 zymogen to its active subunits. These results indicate that co-activation of GABA receptors results in neuroprotection by preventing caspase-3 denitrosylation in KA-induced seizure of rats.

Plakoglobin-dependent regulation of keratinocyte APOPTOSIS by Rnd3

The human epidermis is a self-renewing, stratified epithelial tissue that provides the protective function of the skin. The principal cell type within the epidermis is the keratinocyte and normal function of the epidermis requires that keratinocyte proliferation, differentiation and cell death be carefully controlled. There is clear evidence that signalling through adhesion receptors such as integrins and cadherins plays a key role in regulating epidermal function. Previous work has shown that Rho family GTPases regulate cadherin- and integrin-based adhesion structures and hence epidermal function. In this study we show that a member of this family - Rnd3 - regulates desmosomal cell-cell adhesion in that loss of Rnd3 expression leads to an increase in desmosomes at sites of cell-cell adhesion and altered colony morphology. Loss of Rnd3 expression is also associated with resistance to cisplatin-mediated apoptosis in keratinocytes and this resistance is mediated via the desmosomal protein plakoglobin. We propose a novel plakoglobin-dependent role for Rnd3 in the regulation of keratinocyte cell death.