Involvement of both endoplasmic reticulum- and mitochondria-dependent pathways in cardiotoxin III-induced apoptosis in HL-60 cells

Emerging anticancer potential and mechanisms of snake venom toxins: A review

Animal-derived venom, like snake venom, has been proven to be valuable natural resources for the drug development. Previously, snake venom was mainly investigated in its pharmacological activities in regulating coagulation, vasodilation, and cardiovascular function, and several marketed cardiovascular drugs were successfully developed from snake venom. In recent years, snake venom fractions have been demonstrated with anticancer properties of inducing apoptotic and autophagic cell death, restraining proliferation, suppressing angiogenesis, inhibiting cell adhesion and migration, improving immunity, and so on. A number of active anticancer enzymes and peptides have been identified from snake venom toxins, such as L-amino acid oxidases (LAAOs), phospholipase A2 (PLA2), metalloproteinases (MPs), three-finger toxins (3FTxs), serine proteinases (SPs), disintegrins, C-type lectin-like proteins (CTLPs), cell-penetrating peptides, cysteine-rich secretory proteins (CRISPs). In this review, we focus on summarizing these snake venom-derived anticancer components on their anticancer activities and underlying mechanisms. We will also discuss their potential to be developed as anticancer drugs in the future.

Ensemble-based molecular docking and spectrofluorometric analysis of interaction between cytotoxin and tumor necrosis factor receptor 1

Cytotoxin (CTX) is a three-finger toxin presents predominantly in cobra venom. The functional site of the toxin is located at its three hydrophobic loop tips. Its actual mechanism of cytotoxicity remains inconclusive as few conflicting hypotheses have been proposed in addition to direct cytolytic effects. The present work investigated the interaction between CTX and death receptor families via ensemble-based molecular docking and fluorescence titration analysis. Multiple sequence alignments of different CTX isoforms obtained a conserved CTX sequence. The three-dimensional structure of the conserved CTX was later determined using homology modelling, and its quality was validated. Ensemble-based molecular docking of CTX was performed with different death receptors, such as Fas-ligand and tumor necrosis factor receptor families. Our results showed that tumor necrosis factor receptor 1 (TNFR1) was the best receptor interacting with CTX attributed to the interaction of all three functional loops and evinced with low HADDOCK, Z-score and RMSD value. The interaction between CTX and TNFR1 was also supported by a concentration-dependent reduction of fluorescence intensity with increasing binding affinity. The possible intermolecular interactions between CTX and TNFR1 were Van der Waals forces and hydrogen bonding. Our findings suggest a possibility that CTX triggers apoptosis cell death through non-covalent interactions with TNFR1.Communicated by Ramaswamy H. Sarma.

Oxilipin, a New Anti-cancer Phospholipase A2-like Protein from Iranian Caspian Cobra, Naja Naja Oxiana

The discovery of novel anti-cancer agents from natural resources is highly necessary. Concerning the above problem, the purpose of this study was to discover an anti-cancer compound from Caspian cobra venom. Fractionation of Caspian cobra venom was performed by gel filtration and IEX chromatography. The results showed an anti-cancer protein nominated as Oxilipin. Activity and toxicity of Oxilipin were studied on the colon SW480 cancer cell line using MTT, LDH release, PI staining, morphological cell analysis, hemolysis, and anti-proliferation assays. Oxilipin, an 11kDa protein purified from the venom of the Caspian cobra. LC/MS/MS analysis of obtained protein showed homology with Phospholipase A2 from ‎Naja naja oxiana. 40 µg/ml of Oxilipin can induce an apoptotic effect in SW480 cell line up to 90%; meanwhile, this amount can induce only one-third of cytotoxicity on a normal cell. In this study, Iranian cobra venom was found to have cytotoxic effects on SW480 colon cancer tumor cells, with the least cytotoxicity on normal cells on HEK-293. Given that Oxilipin has slight toxicity on normal cells, it can be hypothesized that the obtained peptide can be considered as a drug lead in an animal model study of colon cancer.

Venom peptides in cancer therapy: An updated review on cellular and molecular aspects

Based on the high incidence and mortality rates of cancer, its therapy remains one of the most vital challenges in the field of medicine. Consequently, enhancing the efficacy of currently applied treatments and finding novel strategies are of great importance for cancer treatment. Venoms are important sources of a variety of bioactive compounds including salts, small molecules, macromolecules, proteins, and peptides that are defined as toxins. They can exhibit different pharmacological effects, and in recent years, their anti-tumor activities have gained significant attention. Several different compounds are responsible for the anti-tumor activity of venoms, and peptides are one of them. In the present review, we discuss the possible anti-tumor activities of venom peptides by highlighting molecular pathways and mechanisms through which these molecules can act effectively. Venom peptides can induce cell death in cancer cells and can substantially enhance the efficacy of chemotherapy and radiotherapy. Also, the venom peptides can mitigate the migration of cancer cells via suppression of angiogenesis and epithelial-to-mesenchymal transition. Notably, nanoparticles have been applied in enhancing the bioavailability of venom peptides and providing targeted delivery, thereby leading to their elevated anti-tumor activity and potential application for cancer therapy.

Sweet as honey, bitter as bile: Mitochondriotoxic peptides and other therapeutic proteins isolated from animal tissues, for dealing with mitochondrial apoptosis

Mitochondria are subcellular organelles involved in cell metabolism and cell life-cycle. Their role in apoptosis regulation makes them an interesting target of new drugs for dealing with cancer or rare diseases. Several peptides and proteins isolated from animal and plant sources are known for their therapeutic properties and have been tested on cancer cell-lines and xenograft murine models, highlighting their ability in inducing cell-death by triggering mitochondrial apoptosis. Some of those molecules have been even approved as drugs. Conversely, many other bioactive compounds are still under investigation for their proapoptotic properties. In this review we report about a group of peptides, isolated from animal venoms, with potential therapeutic properties related to their ability in triggering mitochondrial apoptosis. This class of compounds is known with different names, such as mitochondriotoxins or mitocans.

Cytotoxicity of Nubein6.8 peptide isolated from the snake venom of Naja nubiae on melanoma and ovarian carcinoma cell lines

This study was conducted to examine the cytotoxic effects of Nubein6.8 isolated from the venom of the Egyptian Spitting Cobra Naja nubiae on melanoma (A375) and ovarian carcinoma cell lines and to reveal its mode of action. The size of Nubein6.8 (6801.8 Da) and its N-terminal sequence are similar to cytotoxins purified from the venom of other spitting cobras. Nubein6.8 showed a high significant cytotoxic effect on A375 cell line and moderate effect on A2780. A clonogenic assay showed that Nubein6.8 has a significant long-term potency on A375 cell survival when compared to A2780. The molecular intracellular signaling pathways of Nubein6.8 have been investigated using Western blotting analysis, flow cytometry, and microscale protein labeling. This data revealed that Nubein6.8 has DNA damaging effects and the ability to activate apoptosis in both tumor cell lines. Cellular uptake recordings revealed that the labeled-Nubein6.8 was intracellularly present in A375 cells while A2780 displayed resistance against it. SEM examination showed that Nubein6.8 was found to have high accessibility to malignant melanoma cells. The apoptotic effect of Nubein6.8 was confirmed by TEM examination that revealed many evident characteristics for Nubein6.8 apoptotic efficacy on A375 cell sections. Also, TEM reflected many resistant characteristics that faced Nubein6.8 acquisition through ovarian carcinoma cell sections. Accordingly, the snake venom peptide of Nubein6.8 is a promising template for developing potential cytotoxic agents targeting human melanoma and ovarian carcinoma.

Anticancer Activity of Toxins from Bee and Snake Venom-An Overview on Ovarian Cancer

Cancer represents the disease of the millennium, a major problem in public health. The proliferation of tumor cells, angiogenesis, and the relationship between the cancer cells and the components of the extracellular matrix are important in the events of carcinogenesis, and these pathways are being used as targets for new anticancer treatments. Various venoms and their toxins have shown possible anticancer effects on human cancer cell lines, providing new perspectives in drug development. In this review, we observed the effects of natural toxins from bee and snake venom and the mechanisms through which they can inhibit the growth and proliferation of cancer cells. We also researched how several types of natural molecules from venom can sensitize ovarian cancer cells to conventional chemotherapy, with many toxins being helpful for developing new anticancer drugs. This approach could improve the efficiency of standard therapies and could allow the administration of decreased doses of chemotherapy. Natural toxins from bee and snake venom could become potential candidates for the future treatment of different types of cancer. It is important to continue these studies concerning therapeutic drugs from natural resource and, more importantly, to investigate their mechanism of action on cancer cells.

First Look at the Venom of Naja ashei

Naja ashei is an African spitting cobra species closely related to N. mossambica and N. nigricollis. It is known that the venom of N. ashei, like that of other African spitting cobras, mainly has cytotoxic effects, however data about its specific protein composition are not yet available. Thus, an attempt was made to determine the venom proteome of N. ashei with the use of 2-D electrophoresis and MALDI ToF/ToF (Matrix-Assisted Laser Desorption/Ionization Time of Flight) mass spectrometry techniques. Our investigation revealed that the main components of analysed venom are 3FTxs (Three-Finger Toxins) and PLA₂s (Phospholipases A₂). Additionally the presence of cysteine-rich venom proteins, 5'-nucleotidase and metalloproteinases has also been confirmed. The most interesting fact derived from this study is that the venom of N. ashei includes proteins not described previously in other African spitting cobras-cobra venom factor and venom nerve growth factor. To our knowledge, there are currently no other reports concerning this venom composition and we believe that our results will significantly increase interest in research of this species.

Venom-based peptide therapy: insights into anti-cancer mechanism

The 5-year relative survival rate of all types of cancer has increased significantly over the past three decades partly due to the targeted therapy. However, still there are many targeted therapy drugs could play a role only in a portion of cancer patients with specific molecular alternation. It is necessary to continue to develop new biological agents which could be used alone and/or in combination with current FDA approved drugs to treat complex cancer diseases. Venom-based drugs have been used for hundreds of years in human history. Nevertheless, the venom-origin of the anti-cancer drug do rarely appear in the pharmaceutical market; and this is due to the fact that the mechanism of action for a large number of the venom drug such as venom-based peptide is not clearly understood. In this review, we focus on discussing some identified venom-based peptides and their anti-cancer mechanisms including the blockade of cancer cell proliferation, invasion, angiogenesis, and metastasis (hallmarks of cancer) to fulfill the gap which is hindering their use in cancer therapy. Furthermore, it also highlights the importance of immunotherapy based on venom peptide. Overall, this review provides readers for further understanding the mechanism of venom peptide and elaborates on the need to explore peptide-based therapeutic strategies.

Inhibition of Src activation with cardiotoxin III blocks migration and invasion of MDA-MB-231 cells

Cardiotoxin III (CTX III), a basic polypeptide isolated from Naja naja atra venom, has been demonstrated to display anticancer activity. Breast cancer is a highly malignant carcinoma and most deaths of breast cancer are caused by metastasis. In this study, we show that CTX III blocks migration and invasion of MDA-MB-231 breast cancer cells without affecting apoptosis or cell cycle arrest. CTX III caused significant block of Src kinase activity in MDA-MB-231 cells. Moreover, CTX III treatment was correlated with reduced phosphorylation of FAK at Tyr576, 861 and 925 sites, p130(Cas) at Tyr410, and paxillin at Tyr118. CTX III also suppressed the activation of extracellular signal-regulated kinase1/2 and phosphatidylinositol 3-kinase/Akt. Consistent with inhibition of these signaling pathways and invasion, CTX III inhibited the expression of matrix metalloproteinase-9. In addition, Src specific inhibitor PP2 caused a significant decrease in the phosphorylation of FAK, p130(Cas), paxillin, PI3K/Akt, and ERK1/2. Taken together, CTX III significantly inhibited phosphorylation of Src and downstream molecules as well as cell migration and invasion. Our findings provide evidences that CTX III inhibits Src-mediated signaling pathways involved in controlling MDA-MB-231 cell migration and invasion, suggesting that it has therapeutic potential in breast cancer treatment.

Snake venom: a potent anticancer agent

Since cancer is one of the leading causes of death worldwide, and there is an urgent need to find better treatment. In recent years remarkable progress has been made towards the understanding of proposed hallmarks of cancer development and treatment. Treatment modalities comprise radiation therapy, surgery, chemotherapy, immunotherapy and hormonal therapy. Currently, the use of chemotherapeutics remains the predominant option for clinical control. However, one of the major problems with successful cancer therapy using chemotherapeutics is that patients often do not respond or eventually develop resistance after initial treatment. This has led to the increased use of anticancer drugs developed from natural resources. The biodiversity of venoms and toxins makes them a unique source from which novel therapeutics may be developed. In this review, the anticancer potential of snake venom is discussed. Some of the included molecules are under clinical trial and may find application for anticancer drug development in the near future.

The Anticancer Effect of Cytotoxin 1 from Naja atra Cantor Venom is Mediated by a Lysosomal Cell Death Pathway Involving Lysosomal Membrane Permeabilization and Cathepsin B Release

The cytotoxin family of cobra venom proteins, also called cardiotoxins, can activate both necrotic and apoptotic cell death pathways in cancer cells. Cytotoxin 1 (CTX1)from Naja atra Cantor venom is a 60 amino acid, 6698 Da protein with as yet untested anticancer efficacy and cell selectivity. We tested the toxicity of CTX1 on a number of cancer cell lines (MCF-7, P388, K562, and H22) and on one normal human cell line (16HBE). The rank order of cytotoxicity was MCF-7 > P388 ≈ K562 >H22 ≈ 16HBE, indicating that the effect of CTX1 on certain cancer cell types was relatively selective.Treatment with CTX1 greatly prolonged the survival of P388 ascites tumors bearing KM mice compared to cyclophosphamide treatment. Cell viability, apoptosis, and lysosomal permeability assays all demonstrated that CTX1 induced dose- and time-dependent cell death, with most cells exhibiting the morphological and biochemical features of late apoptosis and necrosis. Mitochondrial membrane potential was lost in CTX1-treated P388 cells. In addition, CTX1 induced an increase in both lysosomal membrane permeability and cathepsin B protease activity. These analyses reveal that CTX1 possesses significant and selective anticancer activity, likely by inducing programmed cell death through mitochondrial and/or lysosomal pathways.

Endoplasmic reticulum stress contributes to arsenic trioxide-induced apoptosis in drug-sensitive and -resistant leukemia cells

This study characterized the role of endoplasmic reticulum stress (ERS)-related pathways in arsenic trioxide-induced apoptosis in multidrug-resistant leukemia K562/ADM cells. Arsenic trioxide exposure led to much significant induction of apoptosis in K562/ADM cells than the parental K562 cells, and the chaperone proteins glucose-regulated protein 78, CHOP/GADD153, X-box binding protein-1 and caspase-12 were activated to varying degrees. Furthermore, arsenic trioxide stimulation led to inhibition of P-glycoprotein and Bcl-2 expression. This study demonstrates a missing link between arsenic trioxide and ERS-induced apoptosis, and suggests that the greater effects obtained in drug-resistant K562/ADM cells may be mediated by downregulation of P-glycoprotein and Bcl-2 expression.

Antimetastatic potential of cardiotoxin III involves inactivation of PI3K/Akt and p38 MAPK signaling pathways in human breast cancer MDA-MB-231 cells

AIM

The aim of this study is to determine whether cardiotoxin III (CTX III) inhibited the metastasis in MDA-MB-231 cells and to further explain its possible mechanisms.

MAIN METHODS

The MTT assay, wound healing assay, Boyden chamber invasion assay, zymography analysis, reverse transcriptase polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), inhibitor assay, and Western blot analysis were used to reveal molecular events of CTX III in this study.

KEY FINDINGS

During treatment with non-toxic doses of CTX III, not only cell migration and invasion were markedly suppressed but the expression/activity of matrix metalloproteinase-9 (MMP-9) was also significantly and selectively suppressed in a concentration-dependent manner. In addition, CTX III decreased the nuclear protein level of nuclear factor kappa B (NF-κB), and pretreatment with NF-κB inhibitor (PDTC) or IκB protease inhibitor (TPCK) also reduced MMP-9 expression/activity and cell migration. Our biochemical assays indicated that CTX III potently suppressed the phosphorylation of p38 mitogen-activated protein kinase (MAPK), phosphatidylinositide-3-kinase (PI3K) and Akt. Additionally, the treatment of inhibitors specific for p38 MAPK (SB203580) or PI3K (wortmannin) to cells could result in a reduced expression of NF-κB and MMP-9 expression, concomitantly with an inhibition on cell metastasis.

SIGNIFICANCE

These results demonstrated that CTX III inhibition of MDA-MB-231 cells may occur through inactivation of both PI3K/Akt and p38 MAPK signaling pathways, exerting inhibitory effects on NF-κB transcriptional factor, thereby decreasing the activity of MMP-9 and then posing an anti-metastatic effect in the cells.

Endoplasmic-reticulum calcium depletion and disease

The endoplasmic reticulum (ER) as an intracellular Ca(2+) store not only sets up cytosolic Ca(2+) signals, but, among other functions, also assembles and folds newly synthesized proteins. Alterations in ER homeostasis, including severe Ca(2+) depletion, are an upstream event in the pathophysiology of many diseases. On the one hand, insufficient release of activator Ca(2+) may no longer sustain essential cell functions. On the other hand, loss of luminal Ca(2+) causes ER stress and activates an unfolded protein response, which, depending on the duration and severity of the stress, can reestablish normal ER function or lead to cell death. We will review these various diseases by mainly focusing on the mechanisms that cause ER Ca(2+) depletion.

Ikarugamycin induces DNA damage, intracellular calcium increase, p38 MAP kinase activation and apoptosis in HL-60 human promyelocytic leukemia cells

Ikarugamycin (IKA) is an antibiotic with strong antiprotozoal and cytotoxic activity. The purpose of our work was to provide insight into the mechanism of action characterizing the cytotoxic effect of IKA in HL-60 leukemia cells in order to evaluate its potential as an antineoplastic agent. Cell viability was reduced in response to IKA (IC(50) of 221.3nM), while the amount of HL-60 cells with a subdiploid DNA content increased significantly after 24h. Apoptotic cell death was confirmed by the cleavage of caspase-9, -8 and -3 using immunoblotting. Single cell gel electrophoresis pointed to an early genotoxic effect. Monitoring of intracellular calcium ([Ca(2+)](i)) levels by flow cytometric analysis of Fluo-3-AM fluorescence indicated an increase in cytosolic calcium that correlated with the cleavage of caspases. In addition, IKA triggered the activation of p38 MAP kinase which was partly dependent on elevated [Ca(2+)](i) concentrations and contributed to caspase activation. The data demonstrate that IKA induced apoptosis in HL-60 cells through genotoxicity and caspase activation which was in part correlated to an increase in intracellular calcium levels and activation of p38 MAP kinase.

Diabetes- and angiotensin II-induced cardiac endoplasmic reticulum stress and cell death: metallothionein protection

We have shown cardiac protection by metallothionein (MT) in the development of diabetic cardiomyopathy (DCM) via suppression of cardiac cell death in cardiac-specific MT-overexpressing transgenic (MT-TG) mice. The present study was undertaken to define whether diabetes can induce cardiac endoplasmic reticulum (ER) stress and whether MT can prevent cardiac cell death via attenuating ER stress. Diabetes was induced by streptozotocin in both MT-TG and wild-type (WT) mice. Two weeks, and 2 and 5 months after diabetes onset, cardiac ER stress was detected by expression of ER chaperones, and apoptosis was detected by CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) and cleaved caspase-3 and caspase-12. Cardiac apoptosis in the WT diabetic mice, but not in MT-TG diabetic mice, was significantly increased 2 weeks after diabetes onset. In parallel with apoptotic effect, significant up-regulation of the ER chaperones, including glucose-regulated protein (GRP)78 and GRP94, cleaved ATF6 and phosporylated eIF2alpha, in the hearts of WT, but not MT-TG diabetic mice. Infusion of angiotensin II (Ang II) also significantly induced ER stress and apoptosis in the hearts of WT, but not in MT-TG mice. Direct administration of chemical ER stress activator tunicamycin significantly increased cardiac cell death only in WT mice. Pre-treatment with antioxidants completely prevented Ang II-induced ER stress and apoptosis in the cultured cardiac cells. These results suggest that ER stress exists in the diabetic heart, which may cause the cardiac cell death. MT prevents both diabetes- and Ang II-induced cardiac ER stress and associated cell death most likely via its antioxidant action, which may be responsible for MT's prevention of DCM.