Biflorin induces cytotoxicity by DNA interaction in genetically different human melanoma cell lines

Cancer is a public health problem and the second leading cause of death worldwide. The incidence of cutaneous melanoma has been notably increasing, resulting in high aggressiveness and poor survival rates. Taking into account the antitumor activity of biflorin, a substance isolated from Capraria biflora L. roots that is cytotoxic in vitro and in vivo, this study aimed to demonstrate the action of biflorin against three established human melanoma cell lines that recapitulate the molecular landscape of the disease in terms of genetic alterations and mutations, such as the TP53, NRAS and BRAF genes. The results presented here indicate that biflorin reduces the viability of melanoma cell lines by DNA interactions. Biflorin causes single and double DNA strand breaks, consequently inhibiting cell cycle progression, replication and DNA repair and promoting apoptosis. Our data suggest that biflorin could be considered as a future therapeutic option for managing melanoma.     

Evaluation of the cytotoxic and antimutagenic effects of biflorin, an antitumor 1,4 o-naphthoquinone isolated from Capraria biflora L

Biflorin is a natural quinone isolated from Capraria biflora L. Previous studies demonstrated that biflorin inhibits in vitro and in vivo tumor cell growth and presents potent antioxidant activity. In this paper, we report concentration-dependent cytotoxic, genotoxic, antimutagenic, and protective effects of biflorin on Salmonella tiphymurium, yeast Saccharomyces cerevisiae, and V79 mammalian cells, using different approaches. In the Salmonella/microsome assay, biflorin was not mutagenic to TA97a TA98, TA100, and TA102 strains. However, biflorin was able to induce cytotoxicity in haploid S. cerevisiae cells in stationary and exponential phase growth. In diploid yeast cells, biflorin did not induce significant mutagenic and recombinogenic effects at the employed concentration range. In addition, the pre-treatment with biflorin prevented the mutagenic and recombinogenic events induced by hydrogen peroxide (H₂O₂) in S. cerevisiae. In V79 mammalian cells, biflorin was cytotoxic at higher concentrations. Moreover, at low concentrations biflorin pre-treatment protected against H₂O₂-induced oxidative damage by reducing lipid peroxidation and DNA damage as evaluated by normal and modified comet assay using DNA glycosylases. Our results suggest that biflorin cellular effects are concentration dependent. At lower concentrations, biflorin has significant antioxidant and protective effects against the cytotoxicity, genotoxicity, mutagenicity, and intracellular lipid peroxidation induced by H₂O₂ in yeast and mammalian cells, which can be attributed to its hydroxyl radical-scavenging property. However, at higher concentrations, biflorin is cytotoxic and genotoxic.     

A novel o-naphtoquinone inhibits N-cadherin expression and blocks melanoma cell invasion via AKT signaling

The down-regulation or loss of epithelial markers is often accompanied by the up-regulation of mesenchymal markers. E-cadherin generally suppresses invasiveness, whereas N-cadherin promotes invasion and metastasis in vitro. The aim of this work is to investigate the role of biflorin, a naphthoquinone with proven anticancer properties, on the expression of N-cadherin and AKT proteins in MDA-MB-435 invasive melanoma cancer cells after 12 h of exposure to 1, 2.5 and 5 μM biflorin. Biflorin inhibited MDA-MB-435 invasion in a dose-dependent manner (p < 0.01). Likewise, biflorin down-regulated N-cadherin and AKT-1 expression in a dose-dependent manner. Biflorin did not inhibit the adhesion of MDA-MB-435 cells to any tested substrates. Additionally, biflorin blocked the invasiveness of cells by down-regulating N-cadherin, most likely via AKT-1 signaling. As such, biflorin may be a novel anticancer agent and a new prototype for drug design.     

Andiroba oil (Carapa guianensis Aubl) shows cytotoxicity but no mutagenicity in the ACPP02 gastric cancer cell line

Andiroba (Carapa guianensis Aubl) is an Amazonian plant whose oil has been widely used in traditional medicine for various purposes, including anti-inflammation. Research reports indicate that the oil can confer antitumor activity due to the presence of fatty acids, which can directly influence cell death mechanisms. Thus, andiroba oil (AO) has gained interest for its potential to be used in antineoplastic therapies. Here, we report an in vitro analysis of the cytotoxic and mutagenic potential of AO in the gastric cancer cell line, ACP02. Cell survival was assessed by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, differential staining with ethidium bromide and acridine orange assessed apoptosis-necrosis, and mutagenesis was assessed by the micronucleus test. The apolar oil was first diluted in 0.1% dimethyl sulfoxide (DMSO) and then further diluted to six concentrations (0.01, 0.1, 1, 10 and 100 μg/mL and 1 mg/mL) in RPMI medium. Controls included RPMI alone (negative control) and 0.1% DMSO diluted in medium (vehicle control). The MTT test showed that AO significantly reduced cell viability (P < .05) only when the highest tested concentration was applied for 48 hours. The apoptosis/necrosis test showed that the highest concentration of AO induced cell death by apoptosis at 24 and 48 hours. There was no statistically significant increase in the frequency of micronuclei. The ability of the AO to decrease the viability of ACP02 cells via apoptosis, without exerting mutagenic effects, suggests that the oil could be useful as an alternative therapeutic agent for primary tumors of stomach cancer.     

Knockdown of LKB1 Sensitizes Endometrial Cancer Cells via AMPK Activation

Metformin is an anti-diabetic drug and has anticancer effects on various cancers. Several studies have suggested that metformin reduces cell proliferation and stimulates cell-cycle arrest and apoptosis. However, the definitive molecular mechanism of metformin in the pathophysiological signaling in endometrial tumorigenesis and metastasis is not clearly understood. In this study, we examined the effects of metformin on the cell viability and apoptosis of human cervical HeLa and endometrial HEC-1-A and KLE cancer cells. Metformin suppressed cell growth in a dose-dependent manner and dramatically evoked apoptosis in HeLa cervical cancer cells, while apoptotic cell death and growth inhibition were not observed in endometrial (HEC-1-A, KLE) cell lines. Accordingly, the p27 and p21 promoter activities were enhanced while Bcl-2 and IL-6 activities were significantly reduced by metformin treatment. Metformin diminished the phosphorylation of mTOR, p70S6K and 4E-BP1 by accelerating adenosine monophosphate-activated kinase (AMPK) in HeLa cancer cells, but it did not affect other cell lines. To determine why the anti-proliferative effects are observed only in HeLa cells, we examined the expression level of liver kinase B1 (LKB1) since metformin and LKB1 share the same signalling system, and we found that the LKB1 gene is not expressed only in HeLa cancer cells. Consistently, the overexpression of LKB1 in HeLa cancer cells prevented metformin-triggered apoptosis while LKB1 knockdown significantly increased apoptosis in HEC-1-A and KLE cancer cells. Taken together, these findings indicate an underlying biological/physiological molecular function specifically for metformin-triggered apoptosis dependent on the presence of the LKB1 gene in tumorigenesis.     

β,β-Dimethylacrylshikonin exerts antitumor activity via Notch-1 signaling pathway in vitro and in vivo

β,β-Dimethylacrylshikonin (DA) is a major component of Radix Lithospermum erythrorhizon and has various biological activities. We have investigated the inhibitory effect of DA on the growth of hepatocellular carcinoma in vitro and in vivo. Notch signaling plays a critical role in maintaining the balance between cell proliferation, differentiation and apoptosis. Hence, perturbed Notch signaling may contribute to tumorigenesis. In the present study, we evaluated whether DA could be an effective inhibitor on cell growth in human gastric cancer cell line, and also the molecular mechanisms. Using multiple cellular and molecular approaches such as MTT assay, colony formation assay, DAPI staining, flow cytometry, real-time PCR and Western blot analysis, we found that DA inhibited cell growth in a dose- and time-dependent manner. Biochemical analysis revealed the involvement of cell cycle regulated proteins in DA-mediated of G₀–G₁ arrest of SGC-7901 cells. Furthermore, DA treatment led to reduced Notch-1 activation, expression of Jagged-1 and its downstream target Hes-1 in vitro and in vivo. Our data demonstrated that DA is a potent inhibitor of progression of gastric cancer cells, which could be due to attenuation of Notch-1. We also suggest that DA could be further developed as a potential therapeutic agent for the treatment of gastric cancer.     

Autophagy plays a protective role against apoptosis induced by toxicarioside N via the Akt/mTOR pathway in human gastric cancer SGC-7901 cells

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.     

A novel Diels–Alder adduct of mulberry leaves exerts anticancer effect through autophagy-mediated cell death

Guangsangon E (GSE) is a novel Diels–Alder adduct isolated from leaves of Morus alba L, a traditional Chinese medicine widely applied in respiratory diseases. It is reported that GSE has cytotoxic effect on cancer cells. In our research, we investigated its anticancer effect on respiratory cancer and revealed that GSE induces autophagy and apoptosis in lung and nasopharyngeal cancer cells. We first observed that GSE inhibits cell proliferation and induces apoptosis in A549 and CNE1 cells. Meanwhile, the upregulation of autophagosome marker LC3 and increased formation of GFP–LC3 puncta demonstrates the induction of autophagy in GSE-treated cells. Moreover, GSE increases the autophagy flux by enhancing lysosomal activity and the fusion of autophagosomes and lysosomes. Next, we investigated that endoplasmic reticulum (ER) stress is involved in autophagy induction by GSE. GSE activates the ER stress through reactive oxygen species (ROS) accumulation, which can be blocked by ROS scavenger NAC. Finally, inhibition of autophagy attenuates GSE-caused cell death, termed as “autophagy-mediated cell death.” Taken together, we revealed the molecular mechanism of GSE against respiratory cancer, which demonstrates great potential of GSE in the treatment of representative cancer.     

Identification of ferroptosis as a novel mechanism for antitumor activity of natural product derivative a2 in gastric cancer

Ferroptosis is a type of cell death accompanied by iron-dependent lipid peroxidation, thus stimulating ferroptosis may be a potential strategy for treating gastric cancer, therapeutic agents against which are urgently required. Jiyuan oridonin A (JDA) is a natural compound isolated from Jiyuan Rabdosia rubescens with anti-tumor activity, unclear anti-tumor mechanisms and limited water solubility hamper its clinical application. Here, we showed a2, a new JDA derivative, inhibited the growth of gastric cancer cells. Subsequently, we discovered for the first time that a2 induced ferroptosis. Importantly, compound a2 decreased GPX4 expression and overexpressing GPX4 antagonized the anti-proliferative activity of a2. Furthermore, we demonstrated that a2 caused ferrous iron accumulation through the autophagy pathway, prevention of which rescued a2 induced ferrous iron elevation and cell growth inhibition. Moreover, a2 exhibited more potent anti-cancer activity than 5-fluorouracil in gastric cancer cell line-derived xenograft mice models. Patient-derived tumor xenograft models from different patients displayed varied sensitivity to a2, and GPX4 downregulation indicated the sensitivity of tumors to a2. Finally, a2 exhibited well pharmacokinetic characteristics. Overall, our data suggest that inducing ferroptosis is the major mechanism mediating anti-tumor activity of a2, and a2 will hopefully serve as a promising compound for gastric cancer treatment.KEY WORDS: Jiyuan Rabdosia rubescens, JDA derivative, Gastric cancer, Ferroptosis, ROS, GPX4, Ferrous iron, Autophagy     

Baicalin induces ferroptosis in bladder cancer cells by downregulating FTH1

Ferroptosis is a non-apoptotic regulated cell death caused by iron accumulation and subsequent lipid peroxidation. Currently, the therapeutic role of ferroptosis on cancer is gaining increasing interest. Baicalin an active component in Scutellaria baicalensis Georgi with anticancer potential various cancer types; however, the effects of baicalein on bladder cancer and the underlying molecular mechanisms remain largely unknown. In the study, we investigated the effect of baicalin on bladder cancer cells 5637 and KU-19-19. As a result, we show baicalin exerted its anticancer activity by inducing apoptosis and cell death in bladder cancer cells. Subsequently, we for the first time demonstrate baicalin-induced ferroptotic cell death in vitro and in vivo, accompanied by reactive oxygen species (ROS) accumulation and intracellular chelate iron enrichment. The ferroptosis inhibitor deferoxamine but not necrostatin-1, chloroquine (CQ), N-acetyl-l-cysteine, l-glutathione reduced, or carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (Z-VAD-FMK) rescued baicalin-induced cell death, indicating ferroptosis contributed to baicalin-induced cell death. Mechanistically, we show that ferritin heavy chain 1 (FTH1) was a key determinant for baicalin-induced ferroptosis. Overexpression of FTH1 abrogated the anticancer effects of baicalin in both 5637 and KU19-19 cells. Taken together, our data for the first time suggest that the natural product baicalin exerts its anticancer activity by inducing FTH1-dependent ferroptosis, which will hopefully provide a prospective compound for bladder cancer treatment.     

New Frontiers in Gut Nutrient Sensor Research: Prophylactic Effect of Glutamine Against Helicobacter pylori–Induced Gastric Diseases in Mongolian Gerbils

Ammonia is one of the important toxins produced by Helicobacter pylori (H. pylori), the major cause of peptic ulcer diseases. We examined whether glutamine or marzulene (a gastroprotective drug containing 1% sodium azulene and 99% glutamine) protects the gastric mucosa against H. pylori in vivo and investigated the mechanism underlying glutamine-induced mucosal protection against ammonia in gastric epithelial cells in vitro. Mongolian gerbils were fed for 3 months with a diet containing glutamine (2% – 20%) or marzulene (20%) starting from 2 weeks or 2 years after H. pylori infection. Then, gastric mucosal changes were evaluated both macro- and microscopically. Cultured gastric epithelial cells were incubated in the presence of ammonia, with or without glutamine; and cell viability, ammonia accumulation, and chemokine production were determined. Gerbils exhibited edema, congestion, and erosion after 3-month infection; and after 2-year infection, they showed cancer-like changes in the gastric mucosa. Glutamine and marzulene significantly suppressed these pathological changes caused in the gastric mucosa by H. pylori infection. Ammonia was accumulated in the cells, resulting in an increase in chemokine production and a decrease in cell viability. These pathological responses were prevented by glutamine. In addition, glutamine decreased chemokine production and cell death through inhibition of cellular accumulation of ammonia, resulting in the prevention of H. pylori–induced gastric diseases in vivo. These results suggest that glutamine/marzulene would be useful for prophylactic treatment of H. pylori–induced gastric diseases in patients.     

Diethyldithiocarbamate induces apoptosis in neuroblastoma cells by raising the intracellular copper level,triggering cytochrome c release and caspase activation

Dithiocarbamates are nitrogen- and sulfur-containing compounds commonly used in pharmacology, medicine and agriculture. The molecular effects of dithiocarbamates on neuronal cell systems are not fully understood, especially in terms of their ability to accumulate copper ions inside the cell. In this work, the molecular effects of N,N-diethyldithiocarbamate (DEDTC) were studied in human SH-SY5Y neuroblastoma cells to determine the role of copper in the DEDTC toxicity and the pathway trigged in cell by the complex Cu-DEDTC. From concentration-dependent studies, we found that 5 μM of this compound induced a drastic decrease in viable cells with a concomitant accumulation in intracellular copper resulted from complexation with DEDTC, measured by atomic absorption spectroscopy. The mechanism of DEDTC-induced apoptosis in neuronal model cells is thought to occur through the death receptor signaling triggered by DEDTC-copper complex in low concentration that is associated with the activation of caspase 8. Our results indicated that the mechanism of cell death involves cytochrome c release forming the apoptosome together with Apaf-1 and caspase 9, converting the caspase 9 into its active form, allowing it to activate caspase 3 as observed by immunofluorescence. This pathway is induced by the cytotoxic effects that occur when DEDTC forms a complex with the copper ions present in the culture medium and transports them into the cell, suggesting that the DEDTC by itself was not able to cause cell death and the major effect is from its copper-complex in neuroblastoma cells. The present study suggests a role for the influence of copper by low concentrations of DEDTC in the extracellular media, the absorption and accumulation of copper in the cell and apoptotic events, induced by the cytotoxic effects that occur when DEDTC forms a complex with the copper ions.     

Anti-tumor effect of germacrone on human hepatoma cell lines through inducing G2/M cell cycle arrest and promoting apoptosis

Germacrone is one of the main bioactive components in the traditional Chinese medicine Rhizoma curcuma. In this study, the anti-proliferative effect of germacrone on the human hepatoma cell lines and the molecular mechanism underlying the cytotoxicity of germacrone were investigated. Treatment of human hepatoma cell lines HepG2 and Bel7402 with germacrone resulted in cell cycle arrest and apoptosis in a dose-dependent manner as measured by MTT assay, flow cytometric and fluorescent microscopy analysis, while much lower effect on normal human liver cell L02 was observed. Flow cytometric analysis revealed that germacrone induced G2/M arrest in the cell cycle progression that was associated with an obvious decrease in the protein expression of cyclin B1 and its activating partner CDK1 with concomitant inductions of p21. Hoechst 33258 and Annexin V/PI staining results showed that the total cell number in apoptosis associated with a dose-dependent up-regulation of Bax and down-regulation of Bcl-2/Bcl-xl was increased. In the meantime, the up-regulation of p53 and reactive oxygen species increase were observed, which suggested that germacrone might be a new potent chemopreventive drug candidate for liver cancer via regulating the expression of proteins related to G2/M cell cycle and apoptosis, and p53 and oxidative damage may play important roles in the inhibition of human hepatoma cells growth by germacrone.     

Azaindole derivatives are inhibitors of microtubule dynamics,with anti-cancer and anti-angiogenic activities

Background and Purpose

Drugs targeting microtubules are commonly used for cancer treatment. However, the potency of microtubule inhibitors used clinically is limited by the emergence of resistance. We thus designed a strategy to find new cell-permeable microtubule-targeting agents.

Experimental Approach

Using a cell-based assay designed to probe for microtubule polymerization status, we screened a chemical library and identified two azaindole derivatives, CM01 and CM02, as cell-permeable microtubule-depolymerizing agents. The mechanism of the anti-tumour effects of these two compounds was further investigated both in vivo and in vitro.

Key Results

CM01 and CM02 induced G2/M cell cycle arrest and exerted potent cytostatic effects on several cancer cell lines including multidrug-resistant (MDR) cell lines. In vitro experiments revealed that the azaindole derivatives inhibited tubulin polymerization and competed with colchicines for this effect, strongly indicating that tubulin is the cellular target of these azaindole derivatives. In vivo experiments, using a chicken chorioallantoic xenograft tumour assay, established that these compounds exert a potent anti-tumour effect. Furthermore, an assay probing the growth of vessels out of endothelial cell spheroids showed that CM01 and CM02 exert anti-angiogenic activities.

Conclusions and Implications

CM01 and CM02 are reversible microtubule-depolymerizing agents that exert potent cytostatic effects on human cancer cells of diverse origins, including MDR cells. They were also shown to inhibit angiogenesis and tumour growth in chorioallantoic breast cancer xenografts. Hence, these azaindole derivatives are attractive candidates for further preclinical investigations.     

Dihydrotanshinone induces apoptosis of SGC7901 and MGC803 cells via activation of JNK and p38 signalling pathways

Context: Dihydrotanshinone (DHT), a natural compound from Salvia miltiorrhiza Bunge (Lamiaceae), showed higher cytotoxic potential compared with other tanshinones. Its effect and mechanism on gastric cancer have not been investigated.

Objective: This study evaluates the effects of DHT on cell proliferation and apoptosis on gastric cancer cells, and elucidates its molecular mechanisms.

Materials and methods: Human gastric cancer MGC803 and SGC7901 cells were treated with various concentrations of DHT (0–15?μM) for 24 and 48?h, and cell growth was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Cell apoptosis was analysed by flow cytometry and DAPI staining. Western blots were performed to investigate changes in the level of apoptosis related genes in gastric cancer cell.

Results: DHT exhibited obvious inhibition of the survival of gastric cancer cells. The IC₅₀ values in SGC7901 and MGC803 cells were 9.14 and 5.39?μM for 24?h, respectively. Cells treated with 6?μM DHT resulted in 41.3% and 35.4% apoptotic cell fractions in SGC7901 and MGC803 cells, respectively, significantly higher than that of the control. Hallmarks of apoptosis were observed in gastric cancer cells after DHT exposure. DHT enhanced the expression levels of cleaved caspase-3, caspase-9 and poly-ADP-ribose polymerases. Furthermore, DHT increased the phosphorylation of JNK and p38 in SGC7901 and MGC803 cells.

Conclusion: DHT induced growth inhibition and apoptosis of gastric cancer cells, involving activation of caspase proteins and the JNK/p38 signaling pathway. The results indicated that DHT has a promising chemotherapeutic potential for human gastric cancer.     

MAPK14 (p38α) inhibition effects against metastatic gastric cancer cells: A potential biomarker and pharmacological target

Gastric cancer has been considering one of the worst cancer types since it is diagnosed in advanced stages, currently in the metastatic stage. Therefore, the challenge is to find out a biomarker and a pharmacology target that would help face this worldwide health issue. In this sense, the mitogen-activated protein kinase (MAPK) signaling pathway has become an important aim of the studies in several cancers. Therefore, we evaluated the role of MAPK14 (p38α) inhibitor SB-245392 in the cellular process, such as proliferation, cell death, and cell migration, and whether MAPK14 gene could be a potential biomarker in gastric cancer models. The results clearly suggest that p38α inhibition significantly impairs the cell proliferation, induces modest apoptosis and strongly inhibits cell migration of gastric cancer cell (AGP-01). Gene expression analysis showed that c-MYC level was decreased and TP53 was increased after SB-245392 treatment. Furthermore, MAPK14 was found in high levels in gastric cancer samples compared to normal samples in the TCGA database, especially in advanced stages (stage 3 and 4), which is significantly associated with low rate survival of the patients. In conclusion, the MAPK14 could be a potential biomarker for advanced gastric cancer as well as a pharmacological target, which could improve the survival rate of patients.     

Ultrafine particles of Ulmus davidiana var. japonica induce apoptosis of gastric cancer cells via activation of caspase and endoplasmic reticulum stress

Small-sized particles are more suitable for targeted delivery and are therapeutically more effective than large-sized particles. In this study, we investigated the anticancer effects of ultrafine particles of Ulmus davidiana var. japonica (ufUJ) on human gastric cancer cell lines SNU-1, SNU-216, and SNU-484. ufUJ induced apoptosis by the proteolytic activation of caspase-9, caspase-6, and caspase-3 and cleavage of poly (ADP-ribose) polymerase. The expression levels of the endoplasmic reticulum stress-related protein BiP markedly increased after ufUJ treatment. BiP knockdown decreased ufUJ-induced cell death. ufUJ-induced apoptosis was inhibited by the caspase-3 inhibitor z-DEVD-fmk, caspase-6 inhibitor z-VEID-fmk, and caspase-9 inhibitor z-LEHD-fmk, and by siRNAs against caspases 3, 6, and 9. Gastric cancer cells did not show anchorage-independent growth in the presence of ufUJ. However, cells treated with caspase inhibitors showed an enhanced colony-forming ability. These findings may be helpful in the prevention of gastric cancer and in the development of functional foods.     

Honokiol inhibits gastric tumourigenesis by activation of 15-lipoxygenase-1 and consequent inhibition of peroxisome proliferator-activated receptor-�� and COX-2-dependent signals

Background and purpose:

Peroxisome proliferator-activated receptor-γ (PPAR-γ), COX-2 and 15-lipoxygenase (LOX)-1 have been shown to be involved in tumour growth. However, the roles of PPAR-γ, COX-2 or 15-LOX-1 in gastric tumourigenesis remain unclear. Here, we investigate the role of 15-LOX-1 induction by honokiol, a small-molecular weight natural product, in PPAR-γ and COX-2 signalling during gastric tumourigenesis.

Experimental approach:

Human gastric cancer cell lines (AGS, MKN45, N87 and SCM-1) were cultured with or without honokiol. Gene and protein expressions were analysed by RT–PCR and Western blotting respectively. Small interfering RNAs (siRNAs) for COX-2, PPAR-γ and 15-LOX-1 were used to interfere with the expressions of these genes. A xenograft gastric tumour model in mouse was used for in vivo study.

Key results:

PPAR-γ and COX-2 proteins were highly expressed in gastric cancer cells. Inhibitors, or siRNA for COX-2 or PPAR-γ, significantly decreased cell viability. Honokiol markedly inhibited PPAR-γ and COX-2 expressions in gastric cancer cells and tumours of xenograft mice, and induced apoptosis and cell death. Honokiol markedly activated cellular 15-LOX-1 expression and 13-S-hydroxyoctadecadienoic acid (a primary product of 15-LOX-1 metabolism of linoleic acid) production. 15-LOX-1 siRNA could reverse the honokiol-induced down-regulation of PPAR-γ and COX-2, and cell apoptosis. 15-LOX-1 was markedly induced in tumours of xenograft mice treated with honokiol.

Conclusions and implications:

These findings suggest that induction of 15-LOX-1-mediated down-regulation of a PPAR-γ and COX-2 pathway by honokiol may be a promising therapeutic strategy for gastric cancer.     

β-lapachone-Induced Apoptosis of Human Gastric Carcinoma AGS Cells Is Caspase-Dependent and Regulated by the PI3K/Akt Pathway

β-lapachone is a naturally occurring quinone that selectively induces apoptotic cell death in a variety of human cancer cells in vitro and in vivo; however, its mechanism of action needs to be further elaborated. In this study, we investigated the effects of β-lapachone on the induction of apoptosis in human gastric carcinoma AGS cells. β-lapachone significantly inhibited cellular proliferation, and some typical apoptotic characteristics such as chromatin condensation and an increase in the population of sub-G1 hypodiploid cells were observed in β-lapachone-treated AGS cells. Treatment with β-lapachone caused mitochondrial transmembrane potential dissipation, stimulated the mitochondria-mediated intrinsic apoptotic pathway, as indicated by caspase-9 activation, cytochrome c release, Bcl-2 downregulation and Bax upregulation, as well as death receptor-mediated extrinsic apoptotic pathway, as indicated by activation of caspase-8 and truncation of Bid. This process was accompanied by activation of caspase-3 and concomitant with cleavage of poly(ADP-ribose) polymerase. The general caspase inhibitor, z-VAD-fmk, significantly abolished β-lapachone-induced cell death and inhibited growth. Further analysis demonstrated that the induction of apoptosis by β-lapachone was accompanied by inactivation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. The PI3K inhibitor LY29004 significantly increased β-lapachone-induced apoptosis and growth inhibition. Taken together, these findings indicate that the apoptotic activity of β-lapachone is probably regulated by a caspase-dependent cascade through activation of both intrinsic and extrinsic signaling pathways, and that inhibition of the PI3K/Akt signaling may contribute to β-lapachone-mediated AGS cell growth inhibition and apoptosis induction.     

Low percentage of CD24hiCD27+CD19+ B cells decelerates gastric cancer progression in XELOX-treated patients

The XELOX regimen (capecitabine plus oxaliplatin) has been demonstrated as first-line chemotherapy for gastric cancer in China. However, the efficacy of XELOX varies in individuals. Some evidences indicate that the variable efficacy might be related to the distinct immune status not only in the tumor site but also in the systemic immune system, and further investigation is required. In this study, we collected 32 PBMC samples from 16 XELOX-treated patients with gastric cancer and analyzed the patterns of immune cells. At the end point, the proportion of CD24^hiCD27⁺CD19⁺ B cells in patients without progression revealed a significant decrease compared with that in patients with progression, but not other immune cells, such as T cells and NK cells. Furthermore, CD19⁺ B cells were more sensitive to capecitabine plus oxaliplatin stimulation in vitro than other immune cells, displaying higher frequency of apoptosis in a dose-dependent way. Thus, our results suggested that the outcomes of XELOX chemotherapy were inversely correlated with peripheral B cell subsets, which might provide a more convenient method to predict gastric cancer progression of XELOX-treated patients.