Showing papers by "Jing Liu published in 2011"

β-Elemene-induced autophagy protects human gastric cancer cells from undergoing apoptosis

Abstract: Background β-Elemene, a compound found in an herb used in traditional Chinese medicine, has shown promising anti-cancer effects against a broad spectrum of tumors. The mechanism by which β-elemene kills cells remains unclear. The aim of the present study is to investigate the anti-tumor effect of β-elemene on human gastric cancer cells and the molecular mechanism involved.

β‐Elemene induces apoptosis as well as protective autophagy in human non‐small‐cell lung cancer A549 cells

Abstract: Objectives beta-Elemene, a novel traditional Chinese medicine, has been shown to be effective against a wide range of tumours. In this study, the antitumour effect of beta-elemene on human non-small-cell lung cancer (NSCLC) A549 cells and the mechanism involved have been investigated. Methods Cell viability and apoptosis were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry, respectively. Protein expression was assayed by Western blotting. Autophagy was evaluated under fluorescence microscopy and transmission electron microscopy. Key findings beta-Elemene inhibited the viability of A549 cells in a dose-dependent manner. This suppression of cell viability was due to the induction of apoptosis. Further study showed that beta-elemene inhibited the activity of the PI3K/Akt/mTOR/p70S6K1 signalling pathway, and at the same time it triggered a robust autophagy. The autophagy was characterized by the accumulation of punctate LC3 dots in the cytoplasm, morphological changes, and the increased levels of LC3-II as well as Atg5-Atg12 conjugated proteins. Inhibition of autophagy with chlorochine significantly enhanced the antitumour effect of beta-elemene. Conclusions Our data indicated that beta-elemene inhibited the activity of the PI3K/Akt/mTOR/p70S6K1 signalling pathway in human NSCLC A549 cells, which resulted in apoptosis as well as protective autophagy. A combination of beta-elemene with autophagy inhibitor might be an effective therapeutic option for advanced NSCLC.

New trends of primary drug resistance among HIV type 1-infected men who have sex with men in Liaoning Province, China.

Abstract: To elucidate the recent changes in prevalence of HIV-1 primary resistance mutations in men who have sex with men (MSM) in Liaoning province, 217 samples from antiretroviral therapy-naive MSM were collected. For 201 samples, the entire protease gene and 256 amino acids of the reverse transcriptase gene were successfully amplified by reverse transcriptase polymerase chain reaction (RT-PCR) and nested PCR of viral RNA and were sequenced. Among the amplified pol sequences, HIV-1 CRF01_AE accounted for 87.6% (176/201), subtype B accounted for 8.0% (16/201), and subtype CRF07_BC accounted for 4.5% (9/201). The overall prevalence of mutations conferring resistance to any drug was 4.5%, representing 4.5% for protease inhibitor (PI)-related mutations, 0.5% for nucleoside/nucleotide reverse transcriptase inhibitor (NRTI)-related mutations, and 0.5% for nonnucleoside reverse transcriptase inhibitor (NNRTI)-related mutations. Included were V32I (0.5%), M46I (2.0%), L90M (2.0%), T215C (0.5%), and Y188L (0.5%)...

Epirubicin enhances TRAIL-induced apoptosis in gastric cancer cells by promoting death receptor clustering in lipid rafts

Abstract: Gastric cancer cells are usually insensitive to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In the present study, in MGC803 cells treated with 100 ng/ml TRAIL for 24 h, the inhibition rate of cell proliferation was 9.76±2.39% and the rate of cell apoptosis was only 4.37 ± 1.45%. Treatment with epirubicin (1.18 µg/ml, IC50 dose for 24 h) and TRAIL (100 ng/ml for 24 h) led to a marked increase in the inhibition rate of cell proliferation and apoptosis compared to treatment with epirubicin or TRAIL alone (P<0.05). Moreover, even more notable cleavage of caspase-3 and 8 was detected with the combination of epirubicin and TRAIL. TRAIL (100 ng/ml) induced only light lipid raft aggregation and DR4 and DR5 clustering. Epirubicin significantly promoted lipid raft DR4 and DR5 aggregation, as well as the localization of DR4 and DR5 in the lipid rafts. Similar results were detected with the combination of epirubicin and TRAIL. Pretreatment with 50 µg/ml nystatin, a cholesterol-sequestering agent, partially prevented epirubicin-induced lipid raft aggregation and DR4 and DR5 clustering. Pretreatment with nystatin did not markedly inhibit epirubicin-induced apoptosis, while nystatin partially suppressed epirubicin and TRAIL-induced apoptosis (P<0.05). Our data demonstrate that epirubicin enhanced TRAIL-induced apoptosis in gastric cancer MGC803 cells, at least partially, through death receptor redistribution in the lipid rafts.

Protective autophagy antagonizes oxaliplatin-induced apoptosis in gastric cancer cells.

Abstract: Oxaliplatin-based chemotherapy is used for treating gastric cancer. Autophagy has been extensively implicated in cancer cells; however, its function is not fully understood. Our study aimed to determine if oxaliplatin induce autophagy in gastric cancer MGC803 cells and to assess the effect of autophagy on apoptosis induced by oxaliplatin. MGC803 cells were cultured with oxaliplatin. Cell proliferation was measured using MTT assay, and apoptosis was determined by flow Cytometry. Protein expression was detected by Western blot. Autophagy was observed using fluorescent microscopy. Our results showed that the rate of apoptosis was 9.73% and 16.36% when MGC803 cells were treated with 5 and 20 µg/mL oxaliplatin for 24 h, respectively. In addition, Caspase activation and poly ADP-ribose polymerase (PARP) cleavage were detected. Furthermore, when MGC803 cells were treated with oxaliplatin for 24 h, an accumulation of punctate LC3 and an increase of LC3-II protein were also detected, indicating the activation of autophagy. Phosphorylation of Akt and mTOR were inhibited by oxaliplatin. Compared to oxaliplatin alone, the combination of autophagy inhibitor chlorochine and oxaliplatin significantly enhanced the inhibition of cell proliferation and the induction of cell apoptosis. In conclusion, oxaliplatin-induced protective autophagy partially prevents apoptosis in gastric cancer MGC803 cells. The combination of autophagy inhibitor and oxaliplatin may be a new therapeutic option for gastric cancer.

Ubiquitin ligase c-Cbl is involved in tamoxifen-induced apoptosis of MCF-7 cells by downregulating the survival signals.

Abstract: Background. Tamoxifen (TAM) is a nonsteroidal antiestrogen that has been widely used in the treatment of breast cancer through its anti-estrogen activity. Recent studies show that TAM is cytotoxic to both estrogen receptor (ER)-positive and ER-negative cells via the induction of apoptosis. However, the molecular mechanisms of this effect are not well understood. In the present study, we investigated the roles of c-Src, ERK, AKT and c-Cbl ubiquitin ligases during TAM-induced apoptosis of MCF-7 cells. Material and methods. MCF-7 cell proliferation and apoptosis were measured by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and fl ow cytometry, respectively. c-Cbl expression, and the activity of c-Src, ERK, AKT were assayed by Western blotting. Overexpression of the wild and the dominant-negative type of c-Cbl (70Z/Cbl) were achieved by transient transfection of plasmids encoding c-Cbl and 70Z/Cbl, respectively, and were confi rmed by Western blotting. Statistical analysis was performed using the t-test, and a p-value � 0.05 was considered to be statistically signifi cant. Results. A high concentration of TAM (25 μ M) induced a time-dependent apoptosis of MCF-7 cells. ERK1/2 and AKT were activated during TAM-induced apoptosis. The ERK1/2 inhibitor PD98059, the PI3K/Akt inhibitor LY294002, and the c-Src inhibitor PP2 all enhanced TAM action. Moreover, the ubiquitin ligase c-Cbl was upregulated during this process. Over-expression of c-Cbl signifi cantly enhanced the apoptosis-inducing effects of TAM, while 70Z/Cbl suppressed the apoptosis-inducing effects of TAM. Further investigation revealed that, overexpression of c-Cbl signi fi cantly downregulated the c-Src protein levels and TAM-induced AKT activity. But 70Z/Cbl signifi cantly upregulated TAM-induced ERK and AKT activity. Conclusions. This study demonstrates that c-Src, ERK, and AKT played a protective role during TAM-induced apoptosis, and that c-Cbl sensitized MCF-7 cells to TAM by modulating the expression of c-Src, and TAM-induced ERK and AKT activity.

Proteasome inhibitor bortezomib (PS-341) enhances RANKL-induced MDA-MB-231 breast cancer cell migration.

Abstract: The receptor activator of nuclear factor κB ligand/receptor activator of nuclear factor κB (RANKL/RANK) pathway is crucial for the migration of RANK-expressing cancer cells The ubiquitin-proteasome protein degradation pathway plays a significant role in tumor metastasis However, the relationship between these two pathways in tumor cell migration is unclear In the present study, we explored the effect of the proteasome inhibitor bortezomib (PS-341) on RANKL-induced MDA-MB-231 breast cancer cell migration Transwell migration assay showed that RANKL-induced MDA-MB-231 cell migration was significantly blocked by the decoy receptor osteoprotegerin (OPG), and was also inhibited by the PI3-K inhibitor LY294002 Western blotting results showed that Akt was rapidly activated by soluble RANKL treatment PS-341 significantly enhanced RANKL-induced MDA-MB-231 cell migration Further study showed that the enhancement of migration by PS-341 involved upregulation of activated Akt and RANK Our results for the first time support the theory that PS-341 treatment may be unsuitable for RANK-positive breast cancer patients

Alteration of inhibitory and activating natural killer cell receptor expression on T cells in human immunodeficiency virus-infected Chinese.

Abstract: T cell expression of NKRs can trigger or inhibit cell-mediated cytotoxicity. However, few studies on T lymphocyte NKR expression in HIV infection exist. Here, we examined the expression patterns of NKG2D, NKG2A, and KIR3DL1 on CD8⁺ and CD3⁺CD8⁻ cells by multicolor flow cytometry in groups of patients with HIV, AIDS or HAART-treated AIDS, as well as HIV-negative normal controls. Individual analysis of KIR3DL1 on CD3⁺ CD8⁺ or CD3⁺CD8⁻ cells revealed no significant differences among any of the groups (P > 0.05). In contrast, the percentage of NKG2A⁺NKG2D⁻CD8⁺ T cells was higher in the AIDS group than in the HIV-negative normal control group (P < 0.01). Meanwhile, the prevalence of NKG2D⁺ NKG2A⁻ CD8⁺ T cells was lower in the AIDS group than in HIV-negative normal controls (P < 0.001). Similar results were also observed for the percentage of NKG2A⁺ NKG2D⁻ on CD3⁺ CD8⁻ cells. However, in contrast to CD8⁺ T cells, the frequencies of NKG2D⁺ NKG2A⁻ on CD3⁺CD8⁻ cells were higher in AIDS and HIV patients than in HIV-negative normal controls (P < 0.01, P < 0.05, respectively). The percentage of NKG2A⁺NKG2⁻CD8⁺ T cells was negatively correlated with CD4⁺T cell counts (r=-0.499, P < 0.01), while the percentage of NKG2D⁺NKG2A⁻CD8⁺ T cells was positively correlated with CD4⁺ T cell counts (r= 0.494, P < 0.01). The percentage of NKG2D⁺NKG2A⁻CD3⁺CD8⁻ T cells was also positively correlated with viral load (r= 0.527, P < 0.01) and negatively correlated with CD4⁺ T cell counts (r=-0.397, P < 0.05). Finally, HAART treatment reversed the changes in NKR expression caused by HIV infection. These results indicate that the expression of NKRs on T cells may be correlated with HIV disease progression.

Cisplatin enhances TRAIL-induced apoptosis in gastric cancer cells through clustering death receptor 4 into lipid rafts

Abstract: Objective Gastric cancer cells are insensitive to tumor necrosis factor-related apoptosisinducing ligand （TRAIL）. To sensitize gastric cancer cells to TRAIL, we treated gastric cancer MGC803 cells with TRAIL and cisplatin. Methods Cell proliferation was measured using MTT assay. Cell apoptosis was determined by flow cytometry. Expression of proteins was analyzed by Western blot. The distribution of lipid rafts and death receptors was analyzed by immunofluorescence microscopy. MGC803 cells were pretreated with 50 mg/L nystatin for 1 h, and followed by the treatment of cisplatin and TRAIL. Results 100 μg/L TRAIL resulted in （ 8.51 ± 3.45 ） % inhibition of cell proliferation and caused （ 3.26 ± 0.89 ） % cell apoptosis in MGC803 cells. Compared with the treatment with cisplatin alone, treatment with TRAIL （100 μg/L） and cisplatin （8.49 mg/L, ICs0 dose of 24 h） led to a dramatic increase in both inhibition of cell proliferation [ （ 52.58 ± 4.57 ） % vs. （ 76.43 ± 5.35 ） %, P 〈 0.05 ] and cell apoptosis [ （ 23.10 ±3.41 ） % vs. （42.56 ±4.11 ） % , P 〈0.05 ]. Moreover, cleavage of caspase-8 and caspase-3 was detected. TRAIL （100 μg/L） did not induce obvious lipid rafts aggregation and death receptor 4 （DR4） clustering, while cisplatin （8.49 mg/L） significantly promoted the localization of DR4 in aggregated lipid rafts. Pretreatment with 50 mg/L nystatin, a cholesterol-sequestering agent, triggered （3.66 ± 0.52）% cell apoptosis after 24 h. Pretreatment with nystatin for I h before the addition of 8.49 mg/L cisplatin for 24 h caused a decreased tendency to cell apoptosis [ （25.74 ± 3.28） % vs. （22.76 ± 2.97） % ]. While, pretreatment with nystatin before the addition of cisplatin and TRAIL, the proportion of apoptotic cells decreased from （43.16 ± 4.26）% to （31.52 ±3.99）% （P〈0.05）. Conclusion Cisplatin enhances TRAIL-induced apoptosis in gastric cancer MGC803 cells through clustering death receptors into lipid rafts. Key words: TRAIL; Cisplatin; Stomach neoplasms ; MGC803 cells ; Lipid rafts ; Death receptor 4 ; Apoptosis