Myriadenolide, a labdane diterpene isolated from Alomia myriadenia (asteraceae) induces depolarization of mitochondrial membranes and apoptosis associated with activation of caspases-8, -9, and -3 in Jurkat and THP-1 cells

Caspase-driven cancer therapies: Navigating the bridge between lab discoveries and clinical applications

Apoptosis is the cell's natural intrinsic regulatory mechanism of normal cells for programmed cell death, which plays an important role in cancer as a classical mechanism of tumor cell death causing minimal inflammation without causing damage to other cells in the vicinity. Induction of apoptosis by activation of caspases is one of the primary targets for cancer treatment. Over the years, a diverse range of natural, synthetic, and semisynthetic compounds and their derivatives have been investigated for their caspase-mediated apoptosis-induced anticancer activities. The review aims to compile the preclinical evidence and highlight the critical mechanistic pathways related to caspase-induced cell apoptosis in cancer treatment. The focus is placed on the key components of the mechanisms, including their chemical nature, and specific attention is given to phytochemicals derived from natural sources and synthetic and semisynthetic compounds. 180+ compounds from the past two decades with potential as anticancer agents are discussed in this review article. By summarizing the current knowledge and advancements in this field, this review provides a comprehensive overview of potential therapeutic strategies targeting apoptosis in cancer cells. The findings presented herein contribute to the ongoing efforts to combat cancer and stimulate further research into the development of effective and targeted anticancer therapies.

Advances on Natural Abietane, Labdane and Clerodane Diterpenes as Anti-Cancer Agents: Sources and Mechanisms of Action

Extensive research over the past decades has identified numerous phytochemicals that could represent an important source of anti-cancer compounds. There is an immediate need for less toxic and more effective preventive and therapeutic strategies for the treatment of cancer. Natural compounds are considered suitable candidates for the development of new anti-cancer drugs due to their pleiotropic actions on target events with multiple manners. This comprehensive review highlighted the most relevant findings achieved in the screening of phytochemicals for anticancer drug development, particularly focused on a promising class of phytochemicals such as diterpenes with abietane, clerodane, and labdane skeleton. The chemical structure of these compounds, their main natural sources, and mechanisms of action were critically discussed.

Vitexin isolated from Prosopis cineraria leaves induce apoptosis in K-562 leukemia cells via inhibition of the BCR-ABL-Ras-Raf pathway

OBJECTIVES

Leukemia is one of the severe cancer types all around the globe. Even though some chemotherapeutic drugs are available for treating leukemia, they have various side effects. As an alternative approach, herbal drugs are focused on current research to overcome leukemia. The present work was conducted to investigate the antileukemic mechanism of active phytochemical vitexin, which was isolated from ethno-medicine (Prosopis cineraria leaf) used by traditional healers of West Bengal, India.

METHODS

Antiproliferative mechanisms of selected phyto-compound against K-562 cells were evaluated using cellular uptake, morphological changes, DNA fragmentation, mitochondrial membrane potential and signaling pathways analysis.

KEY FINDINGS

Vitexin exhibited cytotoxicity by reducing mitochondrial membrane potential (32.40%) and causing DNA fragmentation (84.15%). The western blotting study indicated inhibition of cell survival proteins (BCR, ABL, H-RAS, N-RAS, K-RAS and RAF) and expression of apoptotic proteins (p38, BAX and caspase-9) in leukemia cells upon treatment with vitexin.

CONCLUSIONS

Based on the results, presently investigated phyto-compound vitexin could be considered for developing safe and natural drugs to treat leukemia after conducting suitable preclinical and clinical trials.

The Most Competent Plant-Derived Natural Products for Targeting Apoptosis in Cancer Therapy

Cancer is a challenging problem for the global health community, and its increasing burden necessitates seeking novel and alternative therapies. Most cancers share six basic characteristics known as "cancer hallmarks", including uncontrolled proliferation, refractoriness to proliferation blockers, escaping apoptosis, unlimited proliferation, enhanced angiogenesis, and metastatic spread. Apoptosis, as one of the best-known programmed cell death processes, is generally promoted through two signaling pathways, including the intrinsic and extrinsic cascades. These pathways comprise several components that their alterations can render an apoptosis-resistance phenotype to the cell. Therefore, targeting more than one molecule in apoptotic pathways can be a novel and efficient approach for both identifying new anticancer therapeutics and preventing resistance to therapy. The main purpose of this review is to summarize data showing that various plant extracts and plant-derived molecules can activate both intrinsic and extrinsic apoptosis pathways in human cancer cells, making them attractive candidates in cancer treatment.

Naturally Occurring Sclareol Diterpene Augments the Chemosensitivity of Human Hela Cervical Cancer Cells by Inducing Mitochondrial Mediated Programmed Cell Death, S-Phase Cell Cycle Arrest and Targeting Mitogen-Activated Protein Kinase (MAPK)/Extracellular-Signal-Regulated Kinase (ERK) Signaling Pathway

Background

Cervical cancer is a major threat to female health worldwide. This study was performed to study the anticancer potential of sclareol and as a chemo-sensitizing agent against human cervical cancer cells along with evaluating its effects on apoptosis, cell cycle arrest, and MAPK/ERK signaling pathway.

Material/Methods

MTT assay was performed to check cell viability, morphological changes were observed through phase-contrast microscopy, DAPI (4′,6-diamidino-2-phenylindole) staining and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labelling) assays were performed to evaluate apoptotic effects; MMP (matrix metalloproteinase) and cell cycle analysis were examined through flow cytometry. Western blotting analysis was performed to check the protein expressions of MAPK/ERK signaling pathway and apoptosis proteins.

Results

Results depicted that both sclareol and cisplatin induced cytotoxic effects individually but when used in combination, it led to much more pronounced cytotoxic effects indicating a synergistic effect of sclareol on cisplatin. Sclareol treatment led to significant decrease in the levels of p-MEK and p-ERK. Significant morphological changes (including chromatin condensation, nuclear fragmentation) in cervical cancer cells were seen after treatment. Western blot showed significant alterations including increase in BAX and decrease in BCL-2 levels. An increase in the S-phase cells, indicating cell cycle arrest at S-phase was seen along with modulating the expressions of CDK-1and Cdc25C, and increase in the levels of p-CDK-1, cyclin-B1, cyclin-A, and p-Cdc25C.

Conclusions

Sclareol not only induced cytotoxic effects but also enhanced chemosensitivity of human cervical cancer cells towards cisplatin and these effects are mediated via MAPK/ERK signaling pathway, stimulation of apoptosis and S-phase cell cycle arrest.

Proteomic and functional analysis identifies galectin-1 as a novel regulatory component of the cytotoxic granule machinery

Secretory granules released by cytotoxic T lymphocytes (CTLs) are powerful weapons against intracellular microbes and tumor cells. Despite significant progress, there is still limited information on the molecular mechanisms implicated in target-driven degranulation, effector cell survival and composition and structure of the lytic granules. Here, using a proteomic approach we identified a panel of putative cytotoxic granule proteins, including some already known granule constituents and novel proteins that contribute to regulate the CTL lytic machinery. Particularly, we identified galectin-1 (Gal1), an endogenous immune regulatory lectin, as an integral component of the secretory granule machinery and unveil the unexpected function of this lectin in regulating CTL killing activity. Mechanistic studies revealed the ability of Gal1 to control the non-secretory lytic pathway by influencing Fas–Fas ligand interactions. This study offers new insights on the composition of the cytotoxic granule machinery, highlighting the dynamic cross talk between secretory and non-secretory pathways in controlling CTL lytic function.

Enhanced Antibacterial Activity of Ent-Labdane Derivatives of Salvic Acid (7α-Hydroxy-8(17)-ent-Labden-15-Oic Acid): Effect of Lipophilicity and the Hydrogen Bonding Role in Bacterial Membrane Interaction

In the present study, the antibacterial activity of several ent-labdane derivatives of salvic acid (7α-hydroxy-8(17)-ent-labden-15-oic acid) was evaluated in vitro against the Gram-negative bacterium Escherichia coli and the Gram-positive bacteria Staphylococcus aureus and Bacillus cereus. For all of the compounds, the antibacterial activity was expressed as the minimum inhibitory concentration (MIC) in liquid media and minimum inhibitory amount (MIA) in solid media. Structure activity relationships (SAR) were employed to correlate the effect of the calculated lipophilicity parameters (logP_ow) on the inhibitory activity. Employing a phospholipidic bilayer (POPG) as a bacterial membrane model, ent-labdane-membrane interactions were simulated utilizing docking studies. The results indicate that (i) the presence of a carboxylic acid in the C-15 position, which acted as a hydrogen-bond donor (HBD), was essential for the antibacterial activity of the ent-labdanes; (ii) an increase in the length of the acylated chain at the C-7 position improved the antibacterial activity until an optimum length of five carbon atoms was reached; (iii) an increase in the length of the acylated chain by more than five carbon atoms resulted in a dramatic decrease in activity, which completely disappeared in acyl chains of more than nine carbon atoms; and (iv) the structural factors described above, including one HBD at C-15 and a hexanoyloxi moiety at C-7, had a good fit to a specific lipophilic range and antibacterial activity. The lipophilicity parameter has a predictive characteristic feature on the antibacterial activity of this class of compounds, to be considered in the design of new biologically active molecules.

Phytoconstituents as apoptosis inducing agents: strategy to combat cancer

Advancement in the field of cancer molecular biology has aided researchers to develop various new chemopreventive agents which can target cancer cells exclusively. Cancer chemopreventive agents have proficiency to inhibit, reverse and delay process of carcinogenesis during its early and later course. Chemopreventive agents can act as antioxidative, antimutagenic/antigenotoxic, anti-inflammatory agents or via aiming various molecular targets in a cell to induce cell death. Apoptosis is a kind of cell death which shows various cellular morphological alterations such as cell shrinkage, blebbing of membrane, chromatin condensation, DNA fragmentation, formation of apoptotic bodies etc. Nowadays, apoptosis is being one of the new approaches for the identification and development of novel anticancer therapies. For centuries, plants are known to play part in daily routine from providing food to management of human health. In the last two decades, diverse phytochemicals and various botanical formulations have been characterized as agents that possess potential to execute cancer cells via inducing apoptosis. Data obtained from the research carried out globally pointed out that natural products are the potential candidates which have capability to combat cancer. In the present review, we surveyed literature on natural products which throws light on the mechanism through which these phytochemicals induce apoptosis in cancer cells.

A polysaccharide from Sanguisorbae radix induces caspase-dependent apoptosis in human leukemia HL-60 cells

One polysaccharide (SRP) was purified from Sanguisorbae radix by DEAE-cellulose-52 anion-exchange and Sephacryl S-400 gel filtration chromatography. The aim of this study was to evaluate the anticancer efficacy of SRP on human leukemia HL-60 cells in vitro and unveil the underlying mechanisms. Our results showed that SRP was able to suppress the proliferation of HL-60 cells in a dose-dependent manner by the mechanism involved in the induction of apoptosis. The increase in SRP-induced apoptosis was correlated with a rapid and sustained loss of mitochondrial transmembrane potential (ΔΨm) and a release of cytochrome c from the mitochondria into the cytosol. Furthermore, Western blot and RT-PCR analysis revealed that the protein and mRNA levels of antiapoptotic Bcl-2 were downregulated, whereas those of pro-apoptotic Bax were upregulated. Besides, caspase-9 and caspase-3 were activated, while caspase-8 was intact. Additionally, the apoptotic cells by SRP were significantly inhibited by a caspase-3 inhibitor (z-DEVD-fmk) or a caspase-9 inhibitor (Z-LETD-FMK), demonstrating the important role of caspase-9 and -3 in the process. Taken together, these findings provided evidence that SRP induced the apoptosis of HL-60 cells through an intrinsic mitochondria-mediated signaling pathway and SRP may be a promising chemotherapeutic agent for treatment of leukemia.

The natural compound trans-chalcone induces programmed cell death in Arabidopsis thaliana roots

Chalcone (1,3-diphenyl-2-propen-1-one) is an aromatic ketone precursor of important molecules in plants such as flavonoids or anthocyanins. Its phytotoxicity has been demonstrated on different plant species, but to date little is known about the mechanisms of action of this secondary metabolite at plant cellular level. Detailed analysis by light and transmission electron microscopy (TEM) was conducted to examine the root meristems' ultrastructure of control and chalcone-treated Arabidopsis seedlings. Mitochondrial dysfunction was analysed by measuring mitochondrial membrane potential with JC-1 fluorochrome. Finally, acridine orange/ethidium bromide staining was used for the detection of programmed cell death. Microscopy revealed tissue alterations, inhibition of root hair formation and important changes after 7 and 14 d at the chalcone IC(50) value. Chalcone-treated cells showed signs of programmed cell death such as mitochondrial condensation, disruption of organelles and chromatin fragmentation. Acridine orange/ethidium bromide staining confirmed the programmed cell death, which could be induced by the reduction of mitochondrial transmembrane potential (ΔΨ(m)) that was detected after chalcone treatment. These results confirm the phytotoxic activity of chalcone on Arabidopsis seedlings, the alteration of mitochondrial membrane potential and the induction of programmed cell death.

The labdane diterpene sclareol (labd-14-ene-8, 13-diol) induces apoptosis in human tumor cell lines and suppression of tumor growth in vivo via a p53-independent mechanism of action

The labdane diterpene sclareol has demonstrated significant cytotoxicity against human tumor cell lines and human colon cancer xenografts. Therefore, there is need to elucidate the mode of action of this compound as very little information is known for the anticancer activity of sclareol and other labdane diterpenes, in general. COMPARE analysis of GI(50) values for a number of human cancer cell lines was initially implicated in an effort to assign a putative mechanism of action to the compound. Sclareol-induced cell cycle arrest and apoptosis were assessed by flow cytometry and Western blot analyses. Finally, the anticancer ability of sclareol in vivo was assessed by using human colon cancer xenograft/mouse models. Sclareol arrested in vitro the growth of p53-deficient (HCT116(p53-/-)) human colon cancer cells and subsequently induced apoptosis by activating both caspases-8 and -9. Intraperitoneal administration of liposome-encapsulated sclareol at the maximum tolerated dose induced a marked growth suppression of HCT116(p53-/-) tumors established as xenografts in immunodeficient NOD/SCID mice. In conclusion, we demonstrate herein that sclareol kills human tumor cells by inducing arrest at the G(1)-phase of the cell cycle followed by apoptosis that involves activation of caspases-8, -9 and -3 via a p53-independent mechanism. These findings suggest that liposome-encapsulated sclareol possesses chemotherapeutic potential for the treatment of colorectal and other types of human cancer regardless of the p53-status.

BCR-ABL-mediated upregulation of PRAME is responsible for knocking down TRAIL in CML patients

Tumor necrosis factor-related apoptosis-inducing ligand-TNFSF10 (TRAIL), a member of the TNF-α family and a death receptor ligand, was shown to selectively kill tumor cells. Not surprisingly, TRAIL is downregulated in a variety of tumor cells, including BCR-ABL-positive leukemia. Although we know much about the molecular basis of TRAIL-mediated cell killing, the mechanism responsible for TRAIL inhibition in tumors remains elusive because (a) TRAIL can be regulated by retinoic acid (RA); (b) the tumor antigen preferentially expressed antigen of melanoma (PRAME) was shown to inhibit transcription of RA receptor target genes through the polycomb protein, enhancer of zeste homolog 2 (EZH2); and (c) we have found that TRAIL is inversely correlated with BCR-ABL in chronic myeloid leukemia (CML) patients. Thus, we decided to investigate the association of PRAME, EZH2 and TRAIL in BCR-ABL-positive leukemia. Here, we demonstrate that PRAME, but not EZH2, is upregulated in BCR-ABL cells and is associated with the progression of disease in CML patients. There is a positive correlation between PRAME and BCR-ABL and an inverse correlation between PRAME and TRAIL in these patients. Importantly, knocking down PRAME or EZH2 by RNA interference in a BCR-ABL-positive cell line restores TRAIL expression. Moreover, there is an enrichment of EZH2 binding on the promoter region of TRAIL in a CML cell line. This binding is lost after PRAME knockdown. Finally, knocking down PRAME or EZH2, and consequently induction of TRAIL expression, enhances Imatinib sensibility. Taken together, our data reveal a novel regulatory mechanism responsible for lowering TRAIL expression and provide the basis of alternative targets for combined therapeutic strategies for CML.

Succinate modulates Ca(2+) transient and cardiomyocyte viability through PKA-dependent pathway

GPR91 is an orphan G-protein-coupled receptor (GPCR) that has been characterized as a receptor for succinate, a citric acid cycle intermediate, in several tissues. In the heart, the role of succinate is unknown. We now report that rat ventricular cardiomyocytes express GPR91. We found that succinate, through GPR91, increases the amplitude and the rate of decline of global Ca(2+) transient, by increasing the phosphorylation levels of ryanodine receptor and phospholamban, two well known Ca(2+) handling proteins. The effects of succinate on Ca(2+) transient were abolished by pre-treatment with adenylyl cyclase and cAMP-dependent protein kinase (PKA) inhibitors. Direct PKA activation by succinate was further confirmed using a FRET-based A-kinase activity reporter. Additionally, succinate decreases cardiomyocyte viability through a caspase-3 activation pathway, effect also prevented by PKA inhibition. Taken together, these observations show that succinate acts as a signaling molecule in cardiomyocytes, modulating global Ca(2+) transient and cell viability through a PKA-dependent pathway.

Phytochemistry and in vitro pharmacological activities of South African Vitex (Verbenaceae) species

AIM OF THE STUDY

The in vitro phytochemical and pharmacological investigation of the non-volatile extracts of five South African Vitex species (Verbenaceae); V. obovata ssp. obovata, V. obovata ssp. wilmsii, V. pooara, V. rehmannii and V. zeyheri were investigated in order to validate their traditional use to treat a wide range of ailments such as malaria, wounds, skin diseases and body pains.

MATERIAL AND METHODS

The antimicrobial activity was assessed using the minimum inhibitory concentration assay. Through bioactivity-guided fractionation, the fraction responsible for the antimicrobial activity was determined. The toxicity profile, anti-oxidant and anti-inflammatory activity was evaluated using the tetrazolium cellular viability, 2,2-diphenyl-1-picrylhydrazyl and 5-lipoxygenase assays respectively. The antimalarial activity of the extracts and isolated compound from V. rehmannii was also investigated on the chloroquine-resistant Gambian FCR-3 strain of Plasmodium falciparum using the tritiated hypoxanthine incorporation assay.

RESULTS

Mostly good antimicrobial inhibition was evident against Gram-positive bacteria (0.02-8.00 mg/ml) and lower activity against the Gram-negative bacteria and the yeast (0.50-8.00 mg/ml). The fraction responsible for antimicrobial activity of V. rehmannii was purified to give a labdane diterpene as an inseparable epimeric mixture of 12S,16S/R-dihydroxy-ent-labda-7,13-dien-15,16-olide. Cirsimaritin was also isolated and identified from V. rehmannii. All the species, apart from V. zeyheri, exhibited scavenging activity (IC50: 22.14+/-1.74 to 33.06+/-1.68 microg/ml) in the anti-oxidant assay. None of the species displayed any anti-inflammatory activity at 100 microg/ml. All the extracts and the labdane diterpene exhibited good antimalarial activity, with the labdane diterpene being the most active (IC50: 2.39+/-0.64 microg/ml). The test extracts were shown to be highly toxic, displaying safety index values ranging from 0.53 to 2.59.

CONCLUSION

Of all the pharmacological investigations, the antimalarial and antimicrobial activity exhibited greatest activity and may provide a scientific basis for the ethnomedical use of Vitex species.

Sclareol induces apoptosis in human HCT116 colon cancer cells in vitro and suppression of HCT116 tumor growth in immunodeficient mice

Labd-14-ene-8, 13-diol (sclareol) is a labdane-type diterpene, which has demonstrated significant cytotoxic activity against human leukemic cell lines, but its effect on solid tumor-derived cells is uknown. Here, we demonstrate that addition of sclareol to cultures of human colon cancer HCT116 cells results in inhibition of DNA synthesis, arrest of cells at the G(1) phase of the cell cycle, activation of caspases-8, -9, PARP degradation, and DNA fragmentation, events characteristic of induction of apoptosis. Intraperitoneal (ip) administration of sclareol alone, at the maximum tolerated dose, was unable to induce suppression of growth of HCT116 tumors established as xenografts in immunodeficient SCID mice. In contrast, ip administration of liposome-encapsulated sclareol, following a specific schedule, induced suppression of tumor growth by arresting tumor cell proliferation as assessed by detecting the presence of the cell proliferation-associated nuclear protein, Ki67, in thin tumor sections. These findings suggest that sclareol incorporated into liposomes may possess chemotherapeutic potential for the treatment of colorectal and other types of human cancer.

Efeito do miriadenolídeo isolado de Alomia myriadenia (Asteraceae) sobre o tumor de Erlich ascítico no camundongo

Estudou-se atividade antineoplásica de um produto natural isolado de Alomia myriadenia (miriadenolídeo) no modelo do tumor de Ehrlich em camundongos. Dezoito fêmeas de camundongo Swiss foram inoculadas com 2x10(7) células viáveis de tumor de Ehrlich via intraperitoneal (0,3ml) e posteriormente distribuídas aleatoriamente em três grupos que receberam: grupo I (controle) - 0,3ml de solução de Hanks; grupo II - 31µg/kg de miriadenolídeo; e grupo III - 139µg/kg de miriadenolídeo. No oitavo dia de experimento, foram realizados exames hematológicos e perfil protéico sérico eletroforético. Coletou-se todo o líquido ascítico para avaliação do volume, aparência, pH, contagem de células viáveis e inviáveis, realização de esfregaços para contagem de células claras e escuras, leucócitos e avaliação das regiões organizadoras de nucléolos argentafins (AgNORs). Foram realizados exames macro e microscópicos do baço, fígado e rins e aspirado o conteúdo da medula óssea dos fêmures direito e esquerdo de cada animal para avaliação da relação mielóide:eritróide. Não houve diferença significativa no volume, pH, contagem de células viáveis e inviáveis entre os três grupos estudados, observando-se valores de 17,6 x 10(4) células tumorais viáveis no grupo III, 27,7 x 10(4) no grupo II e 21,1 x 10(4) no grupo I. As AgNORs apresentaram-se pequenas, com distribuição difusa e incontáveis no grupo I, e em menor quantidade no grupo III. Os animais do grupo III apresentaram a menor concentração protéica total sérica (4,7g/dl) (P<0,05) quando comparados com os do grupo II (5,3g/dl) e do grupo I (5,1g/dl). Os valores de albumina foram semelhantes nos três grupos (2,6g/dl), e as globulinas totais foram maiores (P<0,05) no grupo II (2,71g/dl) quando comparadas com os valores médios do grupo III (2,11g/dl) e semelhantes ao grupo I (2,43g/dl). Não houve diferença entre alfa e beta globulinas entre os três grupos estudados, porém as gamaglobulinas foram maiores (P<0,05) no grupo II (1,72g/dl) quando comparadas com as do grupo III (1,13g/dl). Com relação ao eritrograma e leucograma, não houve diferença significativa entre os grupos tratados. A relação mielóide:eritróide foi maior (P<0,05) no grupo III (1,40) quando comparada com a relação nos grupos I (0,92) e II (0,61). A contagem de reticulócitos também foi maior (P<0,05) (11,2) no grupo III, quando comparada com as dos grupos I (4,3) e II (3,6). Em todos os grupos, observou-se degeneração hepática.

Design and development of liposomes incorporating a bioactive labdane-type diterpene. In vitro growth inhibiting and cytotoxic activity against human cancer cell lines

The isolation and identification of bioactive compounds from natural sources has given insights in the discovery of new drugs against several diseases. Labdane-type diterpenes isolated from nature, have been investigated in the past for their pharmaceutical activities. Labd-7,13-dien-15-ol (1), a major lipophilic constituent of the resin 'ladano' was found to exhibit cytotoxic and cytostatic activity against cell lines derived from solid tumors with a profound activity on small lung cancer cells, DMS114. The present study, based on liposomal technology, aimed to develop a suitable carrier of compound 1 to overcome its water insolubility that inhibits further in vivo administration. Liposomes have been proved adequate drug carriers which enhance the solubility of water insoluble drugs and reduce possible side effects. Dipalmitoyl phosphatidylcholine (DPPC), egg phosphatidylcholine (EPC) and dipalmitoyl phosphatidylglycerol (DPPG) were used to prepare liposomes incorporating compound 1 at various molar ratios. Their physicochemical characteristics were determined and liposomes composed of EPC:DPPG 9:0.1 (molar ratio) was chosen as the most suitable carrier concerning their physical characteristics, stability, incorporation efficiency as well as the ability to retain the capture of compound 1 in the presence of RPMI-1640 medium. The activity of the liposomal formulation of compound 1 against human cancer cell lines was compared to that of its free form. The results showed that EPC:DPPG:1 9:0.1:5 (molar ratio) liposomal formulation maintained the pharmacological activity of 1, improved its water solubility and was justified as suitable formulation for in vivo administration of compound 1.

Labd-14-ene-8,13-diol (sclareol) induces cell cycle arrest and apoptosis in human breast cancer cells and enhances the activity of anticancer drugs

Sclareol is a labdane-type diterpene that has demonstrated a significant cytotoxic activity against human leukemic cell lines. Here, we report the effect of sclareol against the human breast cancer cell lines MN1 and MDD2 derived from the parental cell line, MCF7. MN1 cells express functional p53, whereas MDD2 cells do not express p53. Flow cytometry analysis of the cell cycle indicated that sclareol was able to inhibit DNA synthesis induce arrest at the G(0/1) phase of the cycle apoptosis independent of p53. Sclareol-induced apoptosis was further assessed by detection of fragmented DNA in the cells. Furthermore, sclareol enhanced the activity of known anticancer drugs, doxorubicin, etoposide and cisplatinum, against MDD2 breast cancer cell line.

Labdane-type diterpenes: thermal effects on phospholipid bilayers, incorporation into liposomes and biological activity

Labd-13(E)-ene-8alpha,15-diol (1) and its derivative labd-13(E)-ene-8alpha-ol-15-yl-acetate (2) are water insoluble biological active molecules and their structures were elucidated using NMR and X-ray techniques. Differential scanning calorimetry (DSC) was applied to study the thermal effects of 1 and 2 on DPPC bilayers. Liposomes composed of egg phosphatidylcholine/dipalmytoylphosphatidylglycerol (9:0.1 molar ratio) were prepared by the thin-film hydration method and were used for incorporating 1 and 2. Free and liposomal 1 and 2 were tested for their activity against human cancer cell lines using the sulphorhodamine B assay. The effect of 1 and 2 on DPPC bilayers caused abolition of the pre-transition temperature, lowering of the main phase transition and reduction of the transition enthalpy only in the presence of cholesterol. The liposomes that have been designed and developed offer high incorporation efficiency; 62.4% (0.369 drug/lipid molar ratio) and 99.7% (0.661 drug/lipid molar ratio) for 1 and 2, respectively. Liposomal 2 showed growth-inhibiting activity against the majority of the tested cell lines.

Shiga toxin 1 induces apoptosis in the human myelogenous leukemia cell line THP-1 by a caspase-8-dependent, tumor necrosis factor receptor-independent mechanism

Shiga toxins (Stxs) induce apoptosis in a variety of cell types. Here, we show that Stx1 induces apoptosis in the undifferentiated myelogenous leukemia cell line THP-1 in the absence of tumor necrosis factor alpha (TNF-alpha) or death receptor (TNF receptor or Fas) expression. Caspase-8 and -3 inhibitors blocked, and caspase-6 and -9 inhibitors partially blocked, Stx1-induced apoptosis. Stx1 induced the mitochondrial pathway of apoptosis, as activation of caspase-8 triggered the (i) cleavage of Bid, (ii) disruption of mitochondrial membrane potential, and (iii) release of cytochrome c into the cytoplasm. Caspase-8, -9, and -3 cleavage and functional activities began 4 h after toxin exposure and peaked after 8 h of treatment. Caspase-6 may also contribute to Stx1-induced apoptosis by directly acting on caspase-8. It appears that functional Stx1 holotoxins must be transported to the endoplasmic reticulum to initiate apoptotic signaling through the ribotoxic stress response. These data suggest that Stxs may activate monocyte apoptosis via a novel caspase-8-dependent, death receptor-independent mechanism.

Human gastric signet ring carcinoma (KATO-III) cell apoptosis induced by Vitex agnus-castus fruit extract through intracellular oxidative stress

We have previously reported that an ethanol extract of the dried ripe fruit of Vitex agnus-castus (Vitex) displays cytotoxic activity against certain kinds of human cancer cell line resulting in the induction of apoptosis. In this paper, we investigate the molecular mechanism of apoptosis induced by Vitex using a human gastric signet ring carcinoma cell line, KATO-III. DNA fragmentation was observed in Vitex-treated KATO-III cells in a time- and dose-dependent manner. DNA fragmentation was accompanied by the following phenomena: elevation in the level of hemeoxygenase-1 protein and thioredoxin reductase mRNA; repression of Mn-superoxide dismutase and catalase mRNAs; release of cytochrome c from mitochondria into the cytosol; activation of caspases-8, -9 and -3; decrease in the level of Bcl-2, Bcl-XL and Bid protein; increase in the level of Bad protein. The intracellular oxidized state, measured using 2',7'-dichlorofluorescin diacetate, increased after Vitex treatment. While the amount of intracellular GSH decreased significantly after treatment with Vitex, the level of GSSG was unaffected. Furthermore, no significant perturbation in the amount of proteins/mRNAs related to glutathione metabolism could be detected. These apoptotic alterations induced by exposure to Vitex were blocked by the presence of an anti-oxidative reagent, N-acetyl-l-cysteine, or the addition of exogenous GSH. Our results demonstrate that intracellular oxidative stress and mitochondrial membrane damage is responsible for Vitex-induced apoptosis, which may be mediated by a diminution of reduced type glutathione within the cell.

Bovine lactoferricin selectively induces apoptosis in human leukemia and carcinoma cell lines

Bovine lactoferricin (LfcinB) is a cationic, amphipathic peptide that is cytotoxic for human and rodent cancer cells. However, the mechanism by which LfcinB causes the death of cancer cells is not well understood. Here, we show that in vitro treatment with LfcinB rapidly induced apoptosis in several different human leukemia and carcinoma cell lines as determined by DNA fragmentation assays and phosphatidylserine headgroup inversion detected by Annexin V binding to the surface of cancer cells. Importantly, LfcinB treatment did not adversely affect the viability of untransformed human lymphocytes, fibroblasts, or endothelial cells. Studies with different LfcinB-derived peptide fragments revealed that the cytotoxic activity of LfcinB resided within the amino acid sequence FKCRRWQWRM. Treatment of Jurkat T leukemia cells with LfcinB resulted in the production of reactive oxygen species followed by caspase-2-induced dissipation of mitochondrial transmembrane potential and subsequent activation of caspase-9 and caspase-3. Selective inhibitors of caspase-2 (Z-VDVAD-FMK), caspase-9 (Z-LEHD-FMK), and caspase-3 (Z-DEVD-FMK) protected both leukemia and carcinoma cells from LfcinB-induced apoptosis. Conversely, a caspase-8 inhibitor (Z-IETD-FMK) had no effect, which argued against a role for caspase-8 and was consistent with the finding that death receptors were not involved in LfcinB-induced apoptosis. Furthermore, Jurkat T leukemia cells that overexpressed Bcl-2 were less sensitive to LfcinB-induced apoptosis, which was characterized by mitochondrial swelling and the release of cytochrome c from mitochondria into the cytosolic compartment. We conclude that LfcinB kills cancer cells by triggering the mitochondrial pathway of apoptosis at least in part through the generation of reactive oxygen species.

Pancratistatin causes early activation of caspase-3 and the flipping of phosphatidyl serine followed by rapid apoptosis specifically in human lymphoma cells

Recently a major research effort has been focused on the development of anticancer drugs by targeting the components of a biochemical pathway to induce apoptosis in cancerous cells. Some of the natural products (e.g. paclitaxel) have been proven to be useful in inducing apoptosis in cancer cells with limited specificity. Pancratistatin, a natural product isolated and characterized over a decade ago, has been shown to be cytostatic and antineoplastic. We investigated the specificity and biochemical mechanism of action of pancratistatin. Pancratistatin seemed to show more specificity than VP-16 or paclitaxel as an efficient inducer of apoptosis in human lymphoma (Jurkat) cells, with minimal effect on normal nucleated blood cells. Caspase-3 activation and exposure of phosphatidyl serine on the outer leaflet of the plasma membrane were earlier events than the generation of ROS and DNA fragmentation observed following pancratistatin treatment. This indicates a possible involvement of caspase-3 and plasma membrane proteins in the induction phase of apoptosis. Our results indicate that pancratistatin does not cause DNA double-strand breaks or DNA damage prior to the execution phase of apoptosis in cancer cells. Parallel experimentation with VP-16, a currently used medication for cancer treatment, indicated that VP-16 causes substantial DNA damage in normal non-cancerous blood cells, while pancratistatin does not cause any DNA double-strand breaks or DNA damage in non-cancerous cells. Taken together, our finding that pancratistatin induces apoptosis in cancer cells using non-genomic targets, and more importantly does not seem to have any affect non-cancerous cells, presents a significant platform to develop non-toxic anticancer therapies.