热疗对人肺癌细胞凋亡的影响

目的探讨热疗对人肺癌A549、H1299细胞生长与凋亡的影响。方法 MTT法检测热疗对人肺癌A549、H1299细胞生长的抑制作用;流式细胞术观察热疗对人肺癌A549、H1299细胞周期和凋亡的影响;RT-PCR检测凋亡相关基因p53及Casepase-3的表达。结果热疗对人肺癌A549、H1299两种细胞的生长均有抑制作用。热疗可以明显改变人肺癌A549细胞生长周期的分布,G0/G1期细胞明显减少;但对人肺癌H1299细胞生长周期的分布影响不大。热疗能使A549细胞p53蛋白的表达明显增强,但不能诱导H1299细胞p53蛋白的表达。热疗能同时诱导A549、H1299两种细胞Caspase-3蛋白表达的增强,并且以A549细胞的表达尤为明显。结论热疗对两种肺癌细胞的生长均有抑制作用,可以增加细胞凋亡。p53基因可能在热疗诱导肺癌细胞凋亡和周期分布改变的过程中起主导作用。     

Mechanisms of induction of cell cycle arrest and cell death by cryptolepine in human lung adenocarcinoma a549 cells.

We investigated p53-dependent and -independent molecular events associated with cell cycle alteration and cell death in human lung adenocarcinoma A549 cells using cryptolepine, a DNA-damaging agent. After a 24-h treatment, cryptolepine caused an accumulation of p53 at concentrations of 1.25-10 microM and induction of p21(Cip1/WAF1) but only at concentrations up to 5muM. p21(Cip1/WAF1) was also strongly induced by cryptolepine (2.5-5 microM) in cells with p53 largely ablated via small interfering RNA-mediated gene silencing. Cryptolepine induced G1-phase block at 1.25-2.5 microM, S-phase and G2/M-phase block at 2.5-5 microM, and cell death at 10 microM. The dead cells displayed condensed and fragmented nuclei, features of apoptosis. Wortmannin, an inhibitor of ataxia telangiectasia-mutated and DNA-dependent protein kinase (DNA-PK), caused cell cycle arrest at G1 phase without inducing p53 and p21(Cip1/WAF1) expression and cell death. The addition of wortmannin partially prevented cryptolepine-induced expression of p53 and p21(Cip1/WAF1) together with the S-phase block and sensitized cells to induction of cell death. NU7026, a DNA-PK-specific inhibitor, showed neither induction of cell cycle arrest and apoptosis nor the expression of p53 and p21(Cip1/WAF1). The presence of NU7026 caused further reduction of cells in G1 phase induced by cryptolepine at 5 microM without affecting the induction of p53 and p21(Cip1/WAF1) and cell death. This study using the A549 cell as a model demonstrated that cryptolepine selects different molecular pathways to cell cycle checkpoint activation in a dose-specific manner and evokes a wortmannin-sensitive antiapoptosis response.     

8-Chloro-adenosine inhibits growth at least partly by interfering with actin polymerization in cultured human lung cancer cells

A key feature of actin is its ability to bind and hydrolyze ATP. 8-Chloro-adenosine (8-Cl-Ado), which can be phosphorylated to the moiety of 8-Cl-ATP in living cells, inhibits tumor cell proliferation. Therefore we tested the hypothesis that 8-Cl-Ado can interfere with the dynamic state of actin polymerization. We found that 8-Cl-Ado inhibited the growth of human lung cancer cell line A549 and H1299 in culture, and arrested the target cells in G2/M phase evidenced by fluorescence-activated cell sorting (FACS). Immunocytochemistry showed that the normal organization of microfilaments was disrupted in 8-Cl-Ado-exposed cells, which is accompanied by the decrease of cell size and the alteration of cell shape, and by aberrant mitosis and apoptosis in targeted cells. Furthermore, in vitro light scattering assays revealed that 8-Cl-ATP could directly inhibit the transition of G-actin to F-actin. DNase I inhibition assays showed that the G/F-actin ratio, a surrogate marker of actin polymerization status in living cells, was significantly increased in 8-Cl-Ado-exposed A549 and H1299 cells, compared to the G/F-actin ratio in unexposed cells. Taken together, these results indicate that 8-Cl-Ado exposure can alter the dynamic properties of actin polymerization, disrupt the dynamic instability or the rearrangement ability of actin filaments. Therefore, our data suggest that 8-Cl-Ado may exert its cytotoxicity at least partly by interfering with the dynamic instability of microfilaments, which may correlate with its inhibitory effects on cell proliferation and cell death.     

Cytotoxic effects of incense particles in relation to oxidative stress,the cell cycle and F-actin assembly

Epidemiological studies have suggested that combustion-derived smoke, such as that produced during incense burning, is a deleterious air pollutant. It is capable of initiating oxidative stress and mutation; however, the related apoptotic processes remain unclear. In order to elucidate the biological mechanisms of reactive oxygen species (ROS)-induced respiratory toxicology, alveolar epithelial A549 cells were exposed to incense particulate matter (PM), with and without antioxidant N-acetyl-l-cysteine (NAC). The cross-linking associations between oxidative capacity, cell cycle events, actin cytoskeletal dynamics and intracellular calcium signals were investigated. An incense PM suspension caused significant oxidative stress in A549 cells, as shown by inhibition of the cell cycle at G1 and G2/M check-points, and the induction of apoptosis at Sub-G1. At the same time, alterations in the F-actin filamentous assemblies were observed. The levels of intracellular Ca²⁺ were increased after incense PM exposure. Antioxidant NAC treatment revealed that oxidative stress and F-actin remodelling was significantly mitigated. This suggests that ROS accumulation could alter cell cycle regulation and anomalous remodelling of the cortical cytoskeleton that allowed impaired cells to enter into apoptosis. This study has elucidated the integral patho-physiological interactions of incense PM and the potential mechanisms for the development of ROS-driven respiratory impairment.     

托瑞米芬联合顺铂对p53缺失型肺癌细胞株H1299生长抑制作用的研究

目的 探讨托瑞米芬联合顺铂对人肺癌细胞株H1299细胞生长抑制作用及其机制,了解P糖蛋白在H1299细胞中的表达情况.方法 本研究设空白组、对照组(单细胞悬液100μl)、实验组(单细胞悬液100μl+不同药物及浓度),实验组又分为托瑞米芬、顺铂和该2种药物联合组.用四甲基偶氮唑兰比色法检测托瑞米芬及与顺铂联用后H1299细胞的细胞增殖抑制率,分析其细胞周期的变化,检测P糖蛋白在H1299中的表达.结果 托瑞米芬的浓度为20和40 μmol/L时的细胞增殖抑制率分别为(0.307±0.011)％和(0.634±0.007)％,与对照组(0.068 ±0.031)％比较,组间差异均有统计学意义(P＜0.01).低剂量的托瑞米芬(5、10 μmol/L)联合不同浓度顺铂后的细胞增殖抑制率均高于单用顺铂组,并呈现浓度依赖性,组间比较差异有统计学意义(P＜0.05).托瑞米芬与顺铂联用促进H1299细胞凋亡,呈现浓度依赖性.托瑞米芬与顺铂联用后,与单用顺铂组相比,H1299细胞周期发生明显变化,G0/G1期比例增加,S期细胞比例下降,检测出44.9％的H1299细胞有P糖蛋白的存在.结论 低浓度的托瑞米芬(5、10μmol/L)与顺铂联用对H1299细胞有明显的协同抗肿瘤效应,其机制可能与抑制细胞增殖、改变细胞周期分布、促进细胞凋亡有关,且这种作用不依赖于p53基因和雌激素受体.     

Extracellular signal-regulated kinase activation and Bcl-2 downregulation mediate apoptosis after gemcitabine treatment partly via a p53-independent pathway

Gemcitabine is a promising compound for the treatment of human lung cancer. Although apoptosis has been shown to play a role in certain cell types with gemcitabine, the steps leading to cell death after the drug-target interaction are not well understood. We studied the molecular mechanisms of gemcitabine-induced apoptosis and determined the role of p53 function on the cytotoxic effects of gemcitabine in human nonsmall cell lung cancer (NSCLC) H1299 and H1299/p53 cells. Here, we found that gemcitabine induced an apoptotic cell death via a Bcl-2-dependent caspase-9 activation pathway. Moreover, phosphorylated activation of extracellular signal-regulated kinase (ERK) was observed upon gemcitabine treatment. Genetical or pharmacological inhibition of ERK activation markedly blocked gemcitabine-induced cell death. Furthermore, inactivation of Akt was also involved in this event. Taken together, our observations indicate that ERK activation and Akt inactivation mediated gemcitabine-induced apoptosis independently of p53 in human NSCLC H1299 cells.     

Antiproliferative activity of aucubin is through cell cycle arrest and apoptosis in human non-small cell lung cancer A549 cells

Aucubin, an iridoid glycoside isolated from the leaves of Aucuba japonica, inhibits human non-small cell lung cancer A549 cells by blocking cell cycle progression in the G(0)/G(1) phase and inducing apoptosis. An ELISA showed that the G(0)/G(1) phase arrest is due to p53-mediated induction of p21. Enhancement of Fas and its two ligands, membrane-bound and soluble Fas ligand, may be responsible for the apoptotic effect induced by aucubin. The present study shows, for the first time, that the induction of p53 and activity of the Fas/Fas ligand apoptotic system may participate in the antiproliferative activity of aucubin in A549 cells.     

Benzo(a)pyrene induces p73 mRNA expression and necrosis in human lung adenocarcinoma H1299 cells

p53 can mediate DNA damage‐induced apoptosis in various cell lines treated with Benzo(a)pyrene (BaP). However, the potential role of p73, one of the p53 family members, in BaP‐induced apoptotic cell death remains to be determined. In this study, normal fetal lung fibroblasts (MRC‐5) and human lung adenocarcinoma cells (H1299, p53‐null) were treated with BaP at concentrations of 8, 16, 32, 64, and 128 μM for 4 and 12 h. The oxidative stress status, extent of DNA damage, expression of p53, p73, mdm2, bcl‐2, and bax at the mRNA and protein levels, and the percentages of apoptosis and/or necrosis were assessed. In the two BaP‐treated cell lines, we observed increased malondialdehyde (MDA) formation and decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH‐Px) activity at 4 h after the treatment; furthermore, at the time points of 4 and 12 h, we observed extremely high levels of DNA damage. In addition, at 4 h after the treatment, BaP had induced necrosis in MRC‐5 and H1299 cells, but it had inhibited apoptosis in MRC‐5 cells (P < 0.01 for all). Furthermore, in BaP‐treated H1299 cells, only the p73 mRNA level was up‐regulated. The results suggested that BaP‐induced DNA damage could trigger a shift from apoptotic cell death toward necrotic cell death and that necrotic cell death is independent of p53 and p73 in these cell lines. Future studies are needed to investigate the time course of changes in the type of BaP‐induced cell death in more cell lines. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Variation in the kinetics of caspase-3 activation, Bcl-2 phosphorylation and apoptotic morphology in unselected human ovarian cancer cell lines as a response to docetaxel

Paclitaxel is able to cause cell death through the induction of apoptosis. Cell death characteristics for docetaxel have not yet been described in detail. We investigated four unselected human ovarian cancer cell lines for the sensitivity to a 1hr exposure to docetaxel and calculated the concentrations inhibiting 50% (IC(50)) and 90% (IC(90)) of cell growth. Of the cell lines A2780, H134, IGROV-1 (all wild-type p53) and OVCAR-3 (mutant, mt p53) A2780 was most sensitive and OVCAR-3 least sensitive. Equitoxic drug concentrations representing IC(90) values (25-510nM) were applied for 1hr to measure cell cycle distribution, DNA degradation, and to count apoptotic cell bodies and cells with multifragmented nuclei at various time-points after drug exposure. H134, IGROV-1 and OVCAR-3 showed a continued mitotic block up to at least 72hr and prolonged presence of cells with multifragmented nuclei. High percentages of apoptosis were calculated at 48hr and at later time-points. In contrast, A2780 cells accumulated in the S-phase of the cell cycle and apoptosis was hardly present. The changes in the expression levels of p53, p21/WAF1, Bax and Bcl-2, were not predictive for docetaxel-induced apoptosis. Caspase-3 activation occurred only in cells with accumulation in the G2/M phase starting as early as 8hr in OVCAR-3. Prolonged Bcl-2 phosphorylation was evident in OVCAR-3, visible at 24hr in H134 and IGROV-1, while this phenomenon did not occur in A2780. The mitogen-activated protein kinase pathway (JNKs/SAPKs or c-Jun N-terminal kinases/stress-activated protein kinases, JNK1/2; extracellular response kinase, ERK1/2; p38) did not seem to be directly involved in Bcl-2 phosphorylation or apoptosis. We conclude that docetaxel is able to activate caspase-3, induce Bcl-2 phosphorylation and apoptosis in cells that show a prolonged G2/M arrest, but cells may also die by a caspase-3-independent cell death mechanism.     

Mechanisms of action of the novel sulfonamide anticancer agent E7070 on cell cycle progression in human non-small cell lung cancer cells

E7070 is a novel sulfonamide antitumoragent that exhibits potent antitumoractivity in vitro and in vivo.This compound affects cell cycleprogression in human tumor cells. Toelucidate the mechanisms by which E7070inhibits tumor cell growth, we establishedand characterized an E7070-resistantsubline, A549/ER, from a human non-smallcell lung cancer cell line A549. Flowcytometric analyses demonstrated anincrease in G0/G1 and a decrease in S phasepopulations in cells treated with E7070 at20 or 100 g/ml for 24 h. Longerexposure to E7070, i.e. 48 and 72 h,increased the G2/M phase fraction in A549cells. These inhibitory actions of E7070on cell cycle progression were not observedin A549/ER cells. E7070 inhibited thephosphorylation of pRb, decreasedexpressions of cyclin A, B1, CDK2, and CDC2proteins, and suppressed CDK2 catalyticactivity with the induction of p53 andp21 proteins in A549 cells but not inA549/ER cells. Taken together, theseresults suggest that E7070 exerts itsantitumor effects by disturbing the cellcycle at multiple points, including boththe G1/S and the G2/M transition, in humanlung cancer cells.     

Tetrazolium Violet Induced Apoptosis and Cell Cycle Arrest in Human Lung Cancer A549 Cells

Tetrazolium violet is a tetrazolium salt and has been proposed as an antitumor agent. In this study, we reported for the first time that tetrazolium violet not only inhibited human lung cancer A549 cell proliferation but also induced apoptosis and blocked cell cycle progression in the G1 phase. The results showed that tetrazolium violet significantly decreased the viability of A549 cells at 5-15 μM. Tetrazolium violet -induced apoptosis in A549 cells was confirmed by {"type":"entrez-nucleotide","attrs":{"text":"H33258","term_id":"978675","term_text":"H33258"}}H33258 staining assay. In A549, tetrazolium violet blocked the progression of the cell cycle at G1 phase by inducing p53 expression and further up-regulating p21/WAF1 expression. In addition, an enhancement in Fas/APO-1 and its two forms of ligands, membrane-bound Fas ligand (mFasL) and soluble Fas ligand (sFasL), as well as caspase, were responsible for the apoptotic effect induced by tetrazolium violet. The conclusion of this study is that tetrazolium violet induced p53 expression which caused cell cycle arrest and apoptosis. These findings suggest that tetrazolium violet has strong potential for development as an agent for treatment lung cancer.     

Phenethyl isothiocyanate alters the gene expression and the levels of protein associated with cell cycle regulation in human glioblastoma GBM 8401 cells

Glioblastoma is the most common and aggressive primary brain malignancy. Phenethyl isothiocyanate (PEITC), a member of the isothiocyanate family, can induce apoptosis in many human cancer cells. Our previous study disclosed that PEITC induces apoptosis through the extrinsic pathway, dysfunction of mitochondria, reactive oxygen species (ROS)‐induced endoplasmic reticulum (ER) stress, and intrinsic (mitochondrial) pathway in human brain glioblastoma multiforme (GBM) 8401 cells. To the best of our knowledge, we first investigated the effects of PEITC on the genetic levels of GBM 8401 cells in vitro. PEITC may induce G0/G1 cell‐cycle arrest through affecting the proteins such as cdk2, cyclin E, and p21 in GBM 8401 cells. Many genes associated with cell‐cycle regulation of GBM 8401 cells were changed after PEITC treatment: 48 genes were upregulated and 118 were downregulated. The cell‐division cycle protein 20 (CDC20), Budding uninhibited by benzimidazole 1 homolog beta (BUB1B), and cyclin B1 were downregulated, and clusterin was upregulated in GBM 8401 cells treated with PEITC. These changes of gene expression can provide the effects of PEITC on the genetic levels and potential biomarkers for glioblastoma. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 176–187, 2017.     

Indole-3-carbinol induces apoptosis through p53 and activation of caspase-8 pathway in lung cancer A549 cells

Indole-3-carbinol (I3C) has anti-tumor effects in various cancer cell lines. However, the anti-tumor effect of I3C on human lung cancers has been rarely reported. We investigated the anti-tumor effects and its mechanism of I3C on human lung carcinoma A549 cell line. Treatment of the A549 cells with I3C significantly reduced cell proliferation, increased formations of fragmented DNA and apoptotic body, and induced cell cycle arrest at G0/G1 phase. I3C increased not only the protein levels of cyclin D1, phosphorylated p53, and p21 but also the expression of Fas mRNA. Cleavage of caspase-9, -8, -3 and PARP also was increased by I3C. Treatment with wortmannin significantly suppressed both I3C-induced Ser15 phosphorylation and accumulation of p53 protein. The inhibition of caspase-8 by z-IETD-FMK significantly decreased cleavage of procaspase-8,-3 and PARP in I3C-treated A549 cells. Taken together, these results demonstrate that I3C induces cell cycle arrest at G0/G1 through the activation of p-p53 at Ser 15 and induces caspase-8 mediated apoptosis via the Fas death receptor. This molecular mechanism for apoptotic effect of I3C on A549 lung carcinoma cells may be a first report and suggest that I3C may be a preventive and therapeutic agent against lung cancer.     

Induction of apoptosis in a non-small cell human lung cancer cell line by isothiocyanates is associated with P53 and P21.

This study was aimed at examining the effects of glucosinolate derivatives including phenylethyl isothiocyanate (PEITC), benzyl isothiocyanate (BITC), and indole-3-carbinol (I3C), on the induction of apoptosis in human non-small cell lung carcinoma A549 cells. The results indicated that all tested compounds inhibited the growth of A549 cells in a concentration-dependent manner. Flow cytometric analyses and annexin V staining showed that induction of apoptosis occurred at low concentrations of PEITC and BITC (< or = 10 microM), and that necrosis occurred at higher concentrations of PEITC and BITC (25 microM); however, apoptosis was not the major pathway for the antiproliferative effects of I3C. Furthermore, Western blot analyses demonstrated that increased expression of P53 and P21 proteins, but not Bax protein, were associated with PEITC- and BITC-induced apoptosis.     

Upregulation of Fas/Fas ligand-mediated apoptosis by gossypol in an immortalized human alveolar lung cancer cell line

Gossypol has wide antineoplastic effects in vitro, but its effects on human lung cancer have not been explored. To evaluate the activity of gossypol against alveolar cell lung cancer and to provide information on the mechanism of action, we examined the effects of gossypol on the proliferation of A549 cells indirectly using an XTT assay and on the distribution of cells within the phases of the cell cycle using flow cytometry. We also examined several factors that may affect apoptosis, including p53, p21/WAF1, Fas receptor, Fas ligand (FasL) and caspase 8 activity. The results showed that gossypol inhibited proliferation of A549 cells at a concentration of 0.5 micromol/L after 12 h treatment. The effect was both dose- and time-dependent by the induction of apoptosis without the effect of p53 and p21/WAF1. Upregulation of Fas/FasL, in association with the activation of downstream caspase 8 activity, was observed following treatment with gossypol. The Fas/FasL pathway accounted for 75% of gossypol-mediated apoptosis. We suggest that the Fas/FasL apoptotic system is the major pathway for gossypol-mediated apoptosis of A549 cells. Gossypol had no effect on the distribution of A549 cells within the phases of the cell cycle. In conclusion, gossypol inhibited A549 cells mainly by induction of the Fas/FasL apoptotic pathway, but not the p53 and p21/WAF1 pathway.     

Induction of cell cycle arrest and apoptosis in human non-small cell lung cancer A549 cells by casuarinin from the bark of Terminalia arjuna Linn

Casuarinin, a hydrolyzable tannin isolated from the bark of Terminalia arjuna Linn. (Combretaceae), inhibits human non-small cell lung cancer A549 cells by blocking cell cycle progression in the G0/G1 phase and inducing apoptosis. Enzyme-linked immunosorbent assay showed that the G0/G1 phase arrest is due to p53-dependent induction of p21/WAF1. An enhancement in Fas/APO-1 and the two forms of Fas ligand (FasL), membrane-bound FasL and soluble FasL, might be responsible for the apoptotic effect induced by casuarinin. Our study reports here for the first time that the induction of p53 and the activity of the Fas/FasL apoptotic system may participate in the antiproliferative activity of casuarinin in A549 cells.     

Isokotomolide A, a new butanolide extracted from the leaves of Cinnamomum kotoense, arrests cell cycle progression and induces apoptosis through the induction of p53/p21 and the initiation of mitochondrial system in human non-small cell lung cancer A549 cells

This study is the first to investigate isokotomolide A (IKA), a butanolide compound isolated from the leaves of Cinnamomum kotoense Kanehira & Sasaki (Lauraceaee), which exhibits an anti-proliferative activity in human non-small cell lung cancer A549 cells. The results show that IKA inhibits the proliferation of A549 by blocking cell cycle progression in the G0/G1 phase and inducing apoptosis. Blockade of cell cycle was associated with increased p21/WAF1 levels and reduced amounts of cyclin D1, cyclin E, Cdk2, Cdk4, and Cdk6 in a p53-mediated manner. IKA treatment also increased p53 phosphorylation (Ser15) and decreased the interaction of p53-MDM2. IKA treatment triggered the mitochondrial apoptotic pathway, indicated by changing Bax/Bcl-2 ratios, cytochrome c release and caspase-9 activation. In addition, pre-treatment of cells with caspase-9 inhibitor inhibited IKA-induced apoptosis, indicating that caspase-9 activation was involved in A549 cells' apoptosis induced by IKA. Our study reports here for the first time that the induction of p53/p21 and the initiation of the mitochondrial apoptotic system may participate in the anti-proliferative activity of IKA in human non-small cell lung cancer cells.     

Cabozantinib enhances the response of NSCLC cells with wild-type EGFR to erlotinib and pharmacodynamic modeling of their sequential combinations

The epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) monotherapies have limited efficacy in the treatment of EGFR mutation-negative non-small cell lung cancers (NSCLCs). In the present study, we aimed to investigate the combined effect of erlotinib (ER) and cabozantinib (CAB) on NSCLC cell lines harboring wild-type EGFR and to optimize the dosage regimens using pharmacodynamic (PD) modeling and simulation. Therefore, we examined the combined effect of ER and CAB on cell viability, cloning, apoptosis induction, migration and growth dynamics in H1299 and A549 cells. PD modeling and simulation were also performed to quantitatively describe the H1299 cells growth dynamics and to optimize the dosage regimens as well. Our results showed that CAB effectively enhanced the sensitivity of both cell lines to ER. The PD models fitted the data well, and some important parameters were obtained. The exponential (λ₀) and linear (λ₁) growth rates of H1299 cells were 0.0241 h^–1 and 360 cells·h^–1, respectively. The E_max of ER and CAB was 0.0091 h^–1 and 0.0085 h^–1, and the EC₅₀ was 0.812 μM and 1.16 μM, respectively. The synergistic effect observed in the experiments was further confirmed by the estimated combination index φ (1.37), (95% confidence interval: 1.24–1.50), obtained from PD modeling. Furthermore, the dosage regimens were optimized using simulations. In summary, both the experimental and modeling results demonstrated the synergistic interaction between ER and CAB in NSCLCs without EGFR mutations. Sequential combinations of ER and CAB provided an option for the therapy of the NSCLCs with wild-type EGFR, which would provide some references for preclinical study and translational research as well.     

Antiproliferative activity of paeoniflorin is through cell cycle arrest and the Fas/Fas ligand-mediated apoptotic pathway in human non-small cell lung cancer A549 cells

1. Paeoniflorin (PF), isolated from the paeony root, is reported to have immunoregulatory, neuromuscular blocking, anticonvulsant, antihyperglycaemic and antihypotensive effects. 2. The present study investigated the antiproliferative activity of PF. The results showed that PF inhibited the proliferation of A549 by blocking cell cycle progression in the G(0)/G(1) phase and inducing apoptosis. 3. An ELISA showed that G(0)/G(1) phase arrest may be due to p53-independent induction of p21/wild-type p53-activated fragment 1 (WAF1). Increased protein expression of Fas/apoptosis-1 (APO-1) and its two ligands, membrane-bound Fas ligand and soluble Fas ligand, may be responsible for the PF-induced apoptosis. 4. This is the first study to show that the induction of p21/WAF1 and the activity of the Fas/Fas ligand apoptotic system may participate in the antiproliferative activity of PF in A549 cells.     

Nuclear translocation of telomerase reverse transcriptase and calcium signaling in repression of telomerase activity in human lung cancer cells by fungal immunomodulatory protein from Ganoderma tsugae

Recombinant fungal immunomodulatory protein, reFIP-gts, was cloned from Ganoderma tsugae and purified. In our previous study, it was shown that reFIP-gts has anti-telomerase effects in A549 cells. Here, we proved that reFIP-gts entry into the cell and localization in endoplasmic reticulum can result in ER stress, thereby increasing ER stress markers (CHOP/GADD153) and intracellular calcium release in A549 cells. The use of calcium chelator restores reFIP-gts-mediated reduction in telomerase activity. These results strongly suggest that ER stress induces intracellular calcium release and results in inhibition of telomerase activity. Although reFIP-gts decreased hTERT mRNA level in both A549 and H1299 cells, only the telomerase activity in A549 cells was inhibited. Surprisingly, we found that reFIP-gts induces translocation of hTERT from the nucleus into the cytosol in A549 cells but not in H1299 cells. Using leptomycin B, nuclear export inhibitor, we showed that hTERT is not transported. Using MG132, a proteasome inhibitor, reFIP-gts also prevents hTERT translocation from proteasome degradation. Taken together, these results indicate that reFIP-gts inhibits telomerase activity in lung cancer cells through nuclear export mechanisms, which might be mediated by ER stress-induced intracellular calcium level.