Allicin Purified From Fresh Garlic Cloves Induces Apoptosis in Colon Cancer Cells Via Nrf2

Allicin (diallyl thiosulfinate) is the best-known biologically active component in freshly crushed garlic extract. We developed a novel, simple method to isolate active allicin, which yielded a stable compound in aqueous solution amenable for use in in vitro and in vivo studies. We focused on the in vitro effects of allicin on cell proliferation of colon cancer cell lines HCT-116, LS174T, HT-29, and Caco-2 and assessed the underlying mechanisms. This allicin preparation exerted a time- and dose-dependent cytostatic effect on these cells at concentrations ranging from 6.2 to 310 μM. Treatment with allicin resulted in HCT-116 apoptotic cell death as demonstrated by enhanced hypodiploid DNA content, decreased levels of B-cell non-Hodgkin lymphoma-2 (Bcl-2), increased levels of bax and increased capability of releasing cytochrome c from mitochondria to the cytosol. Allicin also induced translocation of NF-E2-related factor-2 (Nrf2) to the nuclei of HCT-116 cells. Luciferase reporter gene assay showed that allicin induces Nrf2-mediated luciferase transactivation activity. SiRNA knock down of Nrf2 significantly affected the capacity of allicin to inhibit HCT-116 proliferation. These results suggest that Nrf2 mediates the allicin-induced apoptotic death of colon cancer cells.     

Origanum Vulgare Induces Apoptosis in Human Colon Cancer Caco2 Cells

Oregano spice is widely used in the Mediterranean diet, which is associated with a low risk for colon cancer. Although the medicinal benefits of oregano, such as the anti-inflammatory and antimicrobial activities, are well known; nonetheless, only few data are available on its effect in cancer prevention, especially concerning the mechanism of action. Here, we investigated the effect of Origanum vulgare ethanolic extracts on redox balance, cell proliferation, and cell death in colon adenocarcinoma Caco2 cells. Oregano extract leads to growth arrest and cell death in a dose- and time-dependent manner. Changes in glutathione content, as well as the increase in its oxidized form, may be involved in oregano-triggered death. Both extrinsic and intrinsic apoptotic pathways appear to be activated by spice extract. Our findings suggest that oregano amounts found in the Mediterranean diet can exert proapoptotic effects, which are selective for cancer cells. Moreover, whole extract, instead of a specific component, can be responsible for the observed cytotoxic effects.     

Stearate Preferentially Induces Apoptosis in Human Breast Cancer Cells

Stearic acid (stearate) is an 18-carbon saturated fatty acid that has been shown to inhibit invasion and proliferation and induce apoptosis in various human cell types. The specificity of stearate-induced apoptosis for cancerous versus noncancerous breast cells has not been examined, and the mechanism underlying stearate-induced apoptosis is unknown. Morphological analysis, cell viability, and caspase-3 activity assays demonstrated that stearate activated apoptosis preferentially in cancerous breast cells in a time- and dose-dependent manner. Inhibition of de novo diacylgycerol synthesis or protein kinase C (PKC) blocked stearate-induced caspase-3 activity, indicating the involvement of a novel or classical PKC isozyme. To our knowledge this is the first study showing that stearate induces apoptosis preferentially in breast cancer cells and implicates protein kinase C in the signaling cascade. These results raise the possibility of dietary stearate having a beneficial role in the prevention or treatment of breast cancer.     

Dimethyl Sulfoxide Extract of Dianthus carmelitarum Induces S Phase Arrest and Apoptosis in Human Colon Cancer Cells

Although several studies have investigated the cytotoxic effects of different Dianthus species, there has been only limited research into the cytotoxic effect of Dianthus carmelitarum. The purpose of this research was to evaluate the phenolic characterization and the cytotoxic effect of D. carmelitarum on human colon cancer (WiDr) cells and the possible mechanisms involved. Total polyphenolic contents (TPC) and phenolic characterization of the extract were evaluated using the Folin-Cioceltau method and reversed-phase high performance liquid chromatography (RP-HPLC), respectively. The cytotoxic activity of the extract was determined using the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The mechanism involved in the extract’s cytotoxic effect was then evaluated in terms of apoptosis and the cell cycle using flow cytometry, while mitochondrial membrane potential (MMP) was investigated using the fluorometric method. The TPC value of the extract was 784.8?±?40.3?mg gallic acid equivalent per 100?g sample, and sinapic acid and benzoic acid were detected as major phenolics in the extract. D. carmelitarum extract exhibited a selective cytotoxic effect (3.6-fold) on WiDr cells compared to normal colon cells. The extract induced cell cycle arrest at the S phase and apoptosis via reduced MMP in WiDr cells. Phytomedical and nutraceutical applications of D. carmelitarum may represent promising approaches in the treatment of cancer.     

Macranthoside B Induces Apoptosis and Autophagy Via Reactive Oxygen Species Accumulation in Human Ovarian Cancer A2780 Cells

Macranthoside B (MB), a saponin compound in Lonicera macranthoides, can block cell proliferation and induce cell death in several types of cancer cells; however, the precise mechanisms by which MB exerts its anticancer effects remain poorly understood. MB blocked A2780 human ovarian carcinoma cell proliferation both dose- and time-dependently. MB induced apoptosis, with increased poly (ADP-ribose) polymerase (PARP) and caspase-3/9 cleavage. MB also caused autophagy in A2780 cells, with light chain 3 (LC3)-II elevation. Inhibiting MB-induced autophagy with the autophagy inhibitor 3-methyladenine (3-MA) significantly decreased apoptosis, with a reduction of growth inhibition; inhibiting MB-induced apoptosis with the pan-caspase inhibitor Z-VAD-FMK did not decrease autophagy but elevated LC3-II levels, indicating that MB-induced autophagy is cytotoxic and may be upstream of apoptosis. Furthermore, MB increased intracellular reactive oxygen species (ROS) levels, with activated 5′ adenosine monophosphate-activated protein kinase (AMPK), decreased mammalian target of rapamycin (mTOR) and P70S6 kinase phosphorylation, and increased PARP and caspase-3/9 cleavage, and LC3-II elevation; treatment with the ROS scavenger N-acetyl cysteine and the AMPK inhibitor Compound C diminished this effect. Therefore, the ROS/AMPK/mTOR pathway mediates the effect of MB on induction of apoptosis via autophagy in human ovarian carcinoma cells.     

Piperlongumine Induces Apoptosis in Human Melanoma Cells Via Reactive Oxygen Species Mediated Mitochondria Disruption

Malignant melanoma is a devastating skin cancer due to its severe drug resistance and prompt metastasis. Piperlongumine is an anti-inflammation and tumor-suppressing natural product with defined structure. While numerous studies revealed exceptional inhibitory effects of piperlongumine on several carcinomas, few investigations were performed on melanoma. Therefore, the present study investigated the anti-tumor effects of piperlongumine on human melanoma cells in vitro, and explored the mechanisms of action. Results from cytotoxicity and proliferation studies demonstrated that piperlongumine inhibited cell growth in melanoma cell lines A375, A875, and B16-F10 in a dose- and time-dependent manner. Flow cytometric analysis showed that piperlongumine obstructed cell cycle progression at G2/M phase and induced apoptosis in A375 cells. Mechanistic investigations illustrated that piperlongumine promoted reactive oxygen species production and decreased mitochondrial membrane potential. In addition, piperlongumine was reported to interfere with the expression of p21, p27, cleaved caspases-3, Bax, Bcl-2, and p-Jun N-terminal kinase (JNK), which are typical regulators associated with cell proliferation, intrinsic apoptosis, and JNKs pathway. Taken together, these results strongly suggested that piperlongumine inhibits cell growth and induces apoptosis in human melanoma cells via ROS mediated mitochondria disruption and JNKs pathway, and piperlongumine may exert promising potential for patients suffering from malignant melanoma.     

Resveratrol Induces Autophagy and Apoptosis in Non-Small-Cell Lung Cancer Cells by Activating the NGFR-AMPK-mTOR Pathway

Resveratrol (RSV) has been reported to induce autophagy and apoptosis in non-small-cell lung cancer A549 cells, and the nerve growth factor receptor (NGFR) regulates autophagy and apoptosis in many other cells. However, the effect of NGFR on autophagy and apoptosis induced by RSV in A549 cells remains unclear. Here, we found that RSV reduced the cell survival rate in time- and concentration-dependent manners, activating autophagy and apoptosis. Lethal autophagy was triggered by RSV higher than 55 μM. The relationship between autophagy and apoptosis depended on the type of autophagy. Specifically, mutual promotion was observed between apoptosis and lethal autophagy. Conversely, cytoprotective autophagy facilitated apoptosis but was unaffected by apoptosis. RSV enhanced NGFR by increasing mRNA expression and prolonging the lifespan of NGFR mRNA and proteins. RSV antagonized the enhanced autophagy and apoptosis caused by NGFR knockdown. As the downstream pathway of NGFR, AMPK-mTOR played a positive role in RSV-induced autophagy and apoptosis. Overall, RSV-induced autophagy and apoptosis in A549 cells are regulated by the NGFR-AMPK-mTOR signaling pathway.     

Diallyl Sulfide Promotes Cell-Cycle Arrest Through the p53 Expression and Triggers Induction of Apoptosis Via Caspase- and Mitochondria-Dependent Signaling Pathways in Human Cervical Cancer Ca Ski Cells

Diallyl sulfide (DAS) is a component of garlic (Alliaceae family). Although diallyl polysulfide has been shown to exhibit anticancer activities, no report explored DAS-affected cell death in human cervical cancer cells in vitro. This study investigated DAS affected on cell-cycle regulation and apoptosis in human cervical cancer Ca Ski cells. DAS at 25–100 μM decreased the viability of Ca Ski cells by increasing G0/G1 phase arrest followed by induction of apoptosis in concentration- and time-dependent effects. Flow cytomteric assay indicated that DAS (75 μM) promoted the production of Ca²⁺ accumulation and decreased the level of mitochondrial membrane potential in Ca Ski cells. Western blotting showed that 75 μM of DAS-induced G0/G1 phase arrest was mediated through the increased expression of p21, p27, and p53 with a simultaneous decrease in CDK2, CDK6, and CHK2 expression. The characteristics of apoptosis, such as morphological changes and DNA condensation, altered the ratio of Bax/Bcl-2 and sub-G1 phase occurred in Ca Ski cells after exposure to DAS. Furthermore, DAS induced mitochondrial dysfunction, leading to the release of cytochrome c for causing apoptosis in Ca Ski cells. These findings suggest that DAS might be a potential chemotherapeutic agent for the treatment of cervical cancer.     

Parkia javanica Extract Induces Apoptosis in S-180 Cells via the Intrinsic Pathway of Apoptosis

Parkia javanica is a leguminous tree, various parts of which are used as food and folklore medicine by the ethnic groups of northeastern India. The present study investigates the in vitro and in vivo anticancer effect of aqueous methanol extract of P. javanica fruit (PJE). HPLC analysis was done to establish the fingerprint chromatogram of PJE and its in vitro radical scavenging activity was measured. PJE caused significant cytotoxicity in sarcoma-180 (S-180), A549, AGS, and MDA-MB435S cancer cells in vitro. Exploration of the mechanistic details in S-180 cells suggested that the reduced cell viability was mediated by induction of apoptosis. Increased expression of proapoptotic proteins such as p53, p21, Bax/Bcl2, cytochrome c (Cyt c), caspase 9, and cleaved poly(ADP-ribose) polymerase, and decrease in proliferative and antiapoptotic markers (Ki-67, Proliferating Cell Nuclear Antigen [PCNA], Bcl-2) validated the anticancer effect of PJE. A decline in the relative fluorescence emission upon staining S-180 cells with Rhodamine 123 (Rh 123), enhanced expression of cytosolic Cyt c and mitochondrial Bax, and inhibition of apoptosis in the presence of caspase-9 inhibitor in PJE-treated cells indicated intrinsic pathway of apoptosis. Liver function test and hepatic antioxidant enzymes demonstrated non-toxicity of PJE. Finally, the detection of PJE in sera by HPLC confirmed its bioavailability.     

Cochinchina Momordica Seed Extract Induces Apoptosis and Cell Cycle Arrest in Human Gastric Cancer Cells Via PARP and p53 Signal Pathways

Cochinchina momordica seed is the dried ripe seed of Momordica cochinchinensis (Lour.) Spreng, which is a kind of fruit and consumed for dietary as well as medicinal uses. In this study, using the human SGC7901 and MKN-28 gastric cancer cell lines, we explored the anticancer activity of the extract from cochinchina momordica seed (ECMS). ECMS inhibited significantly the survival rates of SGC7901 and MKN-28 cells in concentration- and time-dependent manners by MTT assay. The typical apoptotic morphological changes were observed by Hoechst 33258 dye assay after SGC7901 and MKN-28 cells were treated with ECMS for 48 h. Flow cytometry analysis revealed that ECMS-treatment blocked the cells at the S phase of cell cycle. Furthermore, the protein expression levels of poly (ADP-ribose) polymerase (PARP) and Bcl-2 were downregulated notably by ECMS-treatment, whereas those of Fas/Fas-associated death domain, p53, and Bax were upregulated in SGC7901 cells. ECMS dramatically enhanced the enzymatic activities of caspase-3 and caspase-9 whilst slightly increased caspase-8 activity. Taken together, this study demonstrated that ECMS exerted cytotoxic activities via PARP and p53 signal pathways in the human gastric cancer cells.     

Diallyl Trisulfide Induces Apoptosis of Human Basal Cell Carcinoma Cells via Endoplasmic Reticulum Stress and the Mitochondrial Pathway

Diallyl trisulfide (DATS), an active component of garlic oil, has attracted much attention because of its anticancer effect on several types of cancers. However, the mechanism of DATS-induced apoptosis of basal cell carcinoma (BCC) is not fully understood. In the present study, we revealed that DATS-mediated dose-dependent induction of apoptosis in BCC cells was associated with intracellular reactive oxygen species accumulation and disrupted mitochondrial membrane potential. Western analysis demonstrated concordant expression of molecules involved in mitochondrial apoptosis, including DATS-associated increases in phospho-p53, proapoptotic Bax, and decreases in antiapoptotic Bcl-2 and Bcl-xl in BCC cells. Moreover, DATS induced the release of cytochrome c, apoptosis-inducing factor, and HtrA2/Omi into the cytoplasm, and activated factors downstream of caspase-dependent and caspase-independent apoptosis, including nuclear translocation of apoptotic-inducing factor and endonuclease G and the caspase cascade. These results were confirmed by pretreatment with the antioxidant N-acetyl-L-cysteine and the caspase inhibitor (z-VAD-fmk), the latter of which did not completely enhance the viability of DATS-treated BBC cells. Exposure to DATS additionally induced endogenous endoplasmic reticulum stress markers and intracellular Ca2⁺ mobilization, upregulation of Bip/GRP78 and CHOP/GADD153, and activation of caspase-4. Our findings suggest that DATS exerts chemopreventive potential via ER stress and the mitochondrial pathway in BCC cells.     

Antioxidant Rich Morus alba leaf Extract Induces Apoptosis in Human Colon and Breast Cancer Cells by the Downregulation of Nitric Oxide Produced by Inducible Nitric Oxide Synthase

Morus species had been used widely in the traditional medicines for various diseases. In this study we report the in vitro antiproliferative activity of the methanol extract of Morus alba. The extract is capable of inducing cytotoxicity in human colon cancer (HCT-15) cells (IC₅₀ = 13.8 μg/ml) and breast cancer (MCF-7) cells (IC₅₀ = 9.2 μg/ml), resulted in significant morphological changes of the cells, fragmentation of DNA, and caspase-3 activation- characteristics of apoptosis. It downregulated the amount of nitric oxide (NO) produced as a result of inducible nitric oxide (iNOS) activation. The HPLC analysis of the extract showed epicatechin (20%), myricetin (10%), quercetin hydrate (12%), luteolin (12%), and kaempferol (6%) as the major active components and ascorbic acid, gallic acid, pelargonidine, and p-coumaric acid as the minor components. To the best of our knowledge, this is the first report showing the downregulation of iNOS and induction of apoptosis by M. alba extract.     

Butyrate Induces Glutathione S-Transferase in Human Colon Cells and Protects From Genetic Damage by 4-Hydroxy-2-Nonenal

Butyrate, one of the major products of gut fermentation, is known to inhibit proliferation, induce apoptosis and differentiation, and increase phase II enzyme activities in tumor cells, whereas little information is available on protective effects in less-transformed colon cells. The aim of this study was to investigate whether the chemoprotective mechanism of glutathione S-transferase (GST) induction by butyrate could also play a role in earlier stages of colon carcinogenesis and whether chemoresistance of cells toward the endogenous genotoxic risk factor 4-hydroxy-2-nonenal (HNE) could be a consequence of butyrate treatment. As cell models, we used the human tumor cell lines HT29 and HT29 clone 19A, a differentiated subclone with properties resembling primary colon cells. We determined the expression of GSTP1 protein (enzyme-linked immunosorbent assay), the major GST in HT29, GSTP1 mRNA (Northern blotting), GST activity, intracellular glutathione, and total protein. The genotoxic impact of HNE (100-200 μM) was compared in butyrate-treated and nontreated cells using single-cell microgel electrophoresis. Our results show that GSTP1 mRNA, GSTP1 protein, GST activity, and total protein were increased (1.2- to 2.5-fold) and glutathione levels were maintained after 24- 72 h of incubation with 4 mM butyrate. Moreover, a marked reduction of HNE-induced genotoxicity was caused by preincubation with butyrate. Butyrate also induced the phosphorylation of extracellular signal-regulated kinases (ERK1/2, Western blotting) after 5-30 min, which indicates a regulation of GST expression by this signal pathway. Most effects were greater in HT29 parent cells than in clone cells. In conclusion, butyrate enhances expression of GST and other proteins in both cell lines, which leads to an enhanced chemoprotection, reducing the impact of HNE genotoxicity. Thus butyrate could play a role in early and later stages of cancer prevention by reducing exposure to relevant risk factors.     

Ursodeoxycholic Acid Protects Colon Cancer HCT116 Cells From Deoxycholic Acid-Induced Apoptosis by Inhibiting Apoptosome Formation

We previously demonstrated that ursodeoxycholic acid (UDC) requires prolonged (≥5 h) preincubation to exhibit effective protection of colon cancer HCT116 cells from deoxycholic acid (DC)-induced apoptosis. Although UDC diminished DC-mediated caspase-9 activation, cytochrome c release from the mitochondria was not inhibited, indicating that UDC acts on the steps of caspase-9 activation. In the present study, therefore, we investigated the effects of UDC on the factors involved in caspase-9 activation. We found that UDC had no significant effect on the expression of antiapoptotic XIAP. Furthermore, UDC did not affect the expression or release of proapoptotic Smac/DIABLO, or the association of XIAP and Smac/DIABLO. In contrast, association of Apaf-1 and caspase-9 stimulated by 500 μM DC was inhibited by UDC pretreatment. Although UDC caused remarkable activation of Akt/PKB, phosphatidylinositol-3-kinase (PI3K) inhibitor did not significantly reduce UDC-mediated cytoprotection. Furthermore, phosphorylation of threonine residues on caspase-9 after UDC pretreatment could not be detected. UDC-mediated cytoprotection was independent of the MAPK pathway, and cyclic AMP (cAMP) analogue did not inhibit DC-induced apoptosis. Our results indicate that UDC protects colon cancer cells from apoptosis induced by hydrophobic bile acids, by inhibiting apoptosome formation independently of the survival signals mediated by the PI3K, MAPK, or cAMP pathways.     

Procyanidins From Japanese Quince (Chaenomeles Japonica) Fruit Induce Apoptosis in Human Colon Cancer Caco-2 Cells in a Degree of Polymerization-Dependent Manner

Plant proanthocyanidins, including procyanidins, display various biological activities. Here we report an inhibition of human colon cancer Caco-2 cell growth by the extract from Japanese quince fruit and the procyanidin-rich fractions of the extract. We observed that the amount of apoptotic Caco-2 cells increased by 52.1% vs. control after 72-h incubation with 50 μg extract/mL, as assessed by flow cytometry and image cytometry. Under the same experimental conditions the corresponding values for human colon cancer HT-29 cells and for rat normal intestinal IEC-6 cells were 5.0% and 8.1%, respectively. The extract fractions enriched with higher oligomers exhibited the highest proapoptotic activity. In conclusion, the Japanese quince procyanidins exhibited proapoptotic activity in Caco-2 cells within a submilimolar concentration range.     

Hesperetin Induces Apoptosis in Human Glioblastoma Cells via p38 MAPK Activation

Abstract

Glioblastoma (GBM) is the most common and aggressive form of malignant brain tumor, with poor prognosis and a lack of effective treatment. Hesperetin, a natural product found in citrus fruits, displayed bioactivities including antioxidant, anti-inflammatory, and anticancer, while its effects on GBM cells were largely unknown. Here, we explored the anticancer effect of hesperetin on human GBM cells in vitro, as well as the underlying signaling mechanisms. By CCK-8 assay and live/dead assay, hesperetin presented significant inhibitory effect on human GBM U-251 and U-87 cell viability. By DAPI staining and Annexin V-FITC/PI assay, apoptotic death was proved to contribute to the cell viability reduction, and it was verified by the increased Bax/Bcl-2 ratio in western blotting results. Furthermore, by cell cycle analysis and western blotting for cyclin B1, CDK1, and p21, hesperetin was found to induce cell-cycle arrest at G2/M phase. For signaling mechanism, the western blotting results showed elevated p38 MAPK activation, and the reduced Bcl-2 and enhanced Bax upon hesperetin treatment were partly reversed by p38 MAPK inhibitor SB203580. In summary, we have discovered hesperetin as a natural product candidate for the treatment of GBM, and that it could induce GBM cell apoptosis via p38 MAPK activation.     

Prebiotic Chondroitin Sulfate Disaccharide Isolated from Chicken Keel Bone Exhibiting Anticancer Potential Against Human Colon Cancer Cells

Chondroitin sulfate (CS)-Keel disaccharide (CSD) was produced by chondroitin AC lyase (PsPL8A) degradation of food grade CS-Keel polysaccharide isolated from chicken keel cartilage. PsPL8A showed specific activity, 340?±?5.2?U mg^?1 with CS-Keel polysaccharide. TLC showed CSD as the major product. CSD was purified by gel filtration and MS/MS, confirms it as C4S disaccharide. Structural characterization by FTIR and NMR showed presence of N-acetylgalactosamine and glucuronic acid. CSD displayed resistance to gastric juice with 23.7% hydrolysis at pH 1.0. CSD showed prebiotic score of 0.57 for L. acidophilus and 0.58 for B. infantis and produce SCFA products. MTT and morphological analysis confirmed, CSD (0.5?mg mL^?1) does not decrease viability of mouse fibroblast (L929), but showed anti-proliferative potential against human colon cancer (HT-29) cell lines (80% inhibition). CSD treated HT-29 cells exhibit nuclear fragmentation and apoptosis. Prebiotic and anticancer potential of CSD can be utilized for functional food preparation and prevention of gastrointestinal disorders.