丹参酮ⅡA诱导人肺腺癌A549细胞凋亡

目的探讨丹参酮ⅡA(TanshinoneⅡA,TanⅡA)抗人肺腺癌A549作用及其可能作用机制。方法通过细胞形态学和MTT法观察TanⅡA对A549细胞增殖的影响;应用Hoechest33258和PI双染法观察细胞凋亡;采用荧光分光光度计检测细胞内钙及线粒体膜电位;RT-PCR检测Bad和MT-1A mRNA的表达。结果 TanⅡA能抑制A549细胞增殖,且随TanⅡA剂量的增加和作用时间的延长而增强,TanⅡA作用A549细胞24、48和72h的IC50分别为117.85、14.87和6.89μmol·L-1。TanⅡA作用A549细胞24h后,A549细胞出现染色质聚集等典型的凋亡形态学改变,且随TanⅡA剂量的增加,A549细胞凋亡百分率逐渐增大。TanⅡA作用后,A549细胞的细胞内钙升高、线粒体膜电位降低、Bad mRNA表达增加、MT-1A mRNA表达下调。结论 TanⅡA具有抗A549作用,其诱导细胞凋亡可能与钙依赖性通路和MT-1A表达下调有关。     

Sodium arsenite alters cell cycle and MTHFR, MT1/2, and c-Myc protein levels in MCF-7 cells

There is limited available information on the effects of arsenic on enzymes participating in the folate cycle. Therefore, our aim was to evaluate the effects of sodium arsenite on the protein levels of methylenetetrahydrofolate reductase (MTHFR) and dihydrofolate reductase (DHFR) and its further relationship with the expression MT1/2 and c-myc in MCF-7 cells. Arsenite treatment (0-10 μM) for 4 h decreased MTHFR levels in a concentration-dependent fashion without significant effects on DHFR. The effects on MTHFR were observed at arsenite concentrations not significantly affecting cell viability. We also observed an increase in S-phase recruitment at all concentrations probed. Lower concentrations (< 5 μM) induced cell proliferation, showing a high proportion of BrdU-stained cells, indicating a higher DNA synthesis rate. However, higher concentrations (≥ 5 μM) or longer treatment periods induced apoptosis. Arsenite also induced dose-dependent increases in MT1/2 and c-Myc protein levels. The levels of MTHFR were inversely correlated to MT1/2 and c-Myc overexpression and increased S-phase recruitment. Our findings indicate that breast epithelial cells are responsive to arsenite and suggest that exposure may pose a risk for breast cancer. The reductions in MTHFR protein levels contribute to understand the mechanisms underlying the induction of genes influencing growth regulation, such as c-myc and MT1/2. However, further research is needed to ascertain if the effects here reported following short-time and high-dose exposure are relevant for human populations chronically exposed to low arsenic concentrations.     

Acute exposure to arsenite induces metallothionein isoform-specific gene expression in human proximal tubule cells.

The expression of metallothionein (MT) mRNA and protein was determined in human proximal tubule cells (HPT) following acute exposure to the classic stimulators of the stress response, heat and sodium arsenite (As3+). Treatment of the cells with 100 microM As3+ for 4 h resulted in a significant increase in the MT-1 and MT-2 proteins immediately preceding and following removal of the stress. The level of the MT-3 isoform protein was unchanged as a result of As3+ treatment. An analysis of the MT isoform-specific mRNA demonstrated that control cells express the MT-1E, MT-1F, MT-1X, MT-2A, and MT-3 genes, but not the MT-1A, MT-1B, MT-1C, MT-1H, and MT-4 genes. Treatment with As3+ resulted in a significant increase in the expression of the MT-1X gene and appearance of mRNA for the MT-1A gene. Expression of the other MT genes was unaffected by As3+ exposure, except one isolate expressed a low level of MT-1G mRNA at several time points. It is likely that the increase in MT protein seen in As3+-treated cells is due to the increased expression of the MT-1X gene because its expression is much greater than the MT-1A isoform. Treatment of the HPT cells with heat shock had no marked effect on the levels of MT protein or mRNA. This study demonstrates that acute exposure to As3+ increases the levels of MT protein and that this elevation most likely arises from increased expression of the MT-1X isoform.     

Down‐regulation of KIF2A inhibits gastric cancer cell invasion via suppressing MT1‐MMP

Gastric cancer accounts for a sizeable proportion of global cancer mortality with high morbidity and poor prognosis. Kinesin superfamily proteins (KIFs) are microtubule‐dependent motor proteins that function as oncogenes in cancer cells, it has been discovered in recent years. Kinesin family member 2a (KIF2A), a member of the KIFs, has received attention for its role in carcinogenesis and its prognostic value in several human cancers such as breast cancer, colorectal cancer, and squamous cell carcinoma. However, the role of KIF2A in human gastric cancer remains unknown. In this study we aimed to explore the expression and biological functions of KIF2A in human gastric cancer cells, as well as to reveal its potential action mechanism. First, we found that KIF2A was markedly increased in gastric cancer cells (MKN‐28, MKN‐45, NCI‐N87 and SGC‐7901) compared to normal gastric mucosa epithelial cells (GES‐1). Then KIF2A was successfully silenced in MKN‐45 and SGC‐7901 cells to facilitate further research into its function. We discovered that KIF2A silencing can significantly inhibit the growth and invasion of MKN‐45 and SGC‐7901 cells in a time‐independent manner, accompanying a decreased expression of Membrane type 1‐matrix metalloproteinase (MT1‐MMP). When MT1‐MMP was reintroduced into MKN‐45 and SGC‐7901 cells in the KIF2A‐siRNA group, only invasion inhibition effects on MKN‐45 and SGC‐7901 cells induced by KIF2A silencing can be reversed. In conclusion, our study reveals that down‐regulation of KIF2A can inhibit gastric cancer cell invasion by suppressing MT1‐MMP.     

Diversified expression of aryl hydrocarbon receptor dependent genes in human laryngeal squamous cell carcinoma cell lines treated with β-naphthoflavone

The aryl hydrocarbon receptor (AhR) mediates a variety of biological responses to ubiquitous environmental pollutants. In this study the effect of administration of β-naphthoflavone (BNF), potent AhR ligand, on the expression of AhR, AhRR, CYP1A1, CYP1A2, CYP1B1, NQO1, GSTA1, ALDH3A1 and UGT1A genes encoding the enzymes controlled by AhR were examined in thirteen laryngeal tumor cell lines and in HepaRG cell line. The analyzed cell lines were derived from patients with squamous laryngeal cancer, with history of cigarette smoking and without signs of human papillomavirus types 16 and 18 infection in investigated cells. Quantitative real-time RT-PCR analysis revealed huge interindividual differences in expression of genes from AhR regulatory network. Our results strongly suggest predominant effect of DNA methylation on induction of CYP1A1 expression by AhR ligands as well. Our results indicate that differentiated HepaRG cell line appeared to be very good substitute for human liver in studies on xenobiotic metabolism by AhR regulated enzymes.     

Increased oxidative stress and antioxidant expression in mouse keratinocytes following exposure to paraquat

Paraquat (1,1′-dimethyl-4,4′-bipyridinium) is a widely used herbicide known to induce skin toxicity. This is thought to be due to oxidative stress resulting from the generation of cytotoxic reactive oxygen intermediates (ROI) during paraquat redox cycling. The skin contains a diverse array of antioxidant enzymes which protect against oxidative stress including superoxide dismutase (SOD), catalase, glutathione peroxidase-1 (GPx-1), heme oxygenase-1 (HO-1), metallothionein-2 (MT-2), and glutathione-S-transferases (GST). In the present studies we compared paraquat redox cycling in primary cultures of undifferentiated and differentiated mouse keratinocytes and determined if this was associated with oxidative stress and altered expression of antioxidant enzymes. We found that paraquat readily undergoes redox cycling in both undifferentiated and differentiated keratinocytes, generating superoxide anion and hydrogen peroxide as well as increased protein oxidation which was greater in differentiated cells. Paraquat treatment also resulted in increased expression of HO-1, Cu,Zn-SOD, catalase, GSTP1, GSTA3 and GSTA4. However, no major differences in expression of these enzymes were evident between undifferentiated and differentiated cells. In contrast, expression of GSTA1-2 was significantly greater in differentiated relative to undifferentiated cells after paraquat treatment. No changes in expression of MT-2, Mn-SOD, GPx-1, GSTM1 or the microsomal GST's mGST1, mGST2 and mGST3, were observed in response to paraquat. These data demonstrate that paraquat induces oxidative stress in keratinocytes leading to increased expression of antioxidant genes. These intracellular proteins may be important in protecting the skin from paraquat-mediated cytotoxicity.     

Erucin,a new promising cancer chemopreventive agent from rocket salads,shows anti-proliferative activity on human lung carcinoma A549 cells

Erucin (ER) is a dietary isothiocyanate present in cruciferous vegetables, such as rocket salads (Erucasativa Mill., Diplotaxis sp.), that has been recently considered a promising cancer chemopreventive phytochemical. Biological activity of ER was investigated on human lung adenocarcinoma A549 cells, analyzing its effects on molecular pathways involved in apoptosis and cell cycle arrest, such as PARP-1 cleavage, p53 and p21 protein expression. Our results show that ER affects the A549 cell proliferation, enhancing significantly p53 and p21 protein expression in a dose-dependent manner (p < 0.001). PARP-1 cleavage occurs only after exposure to high concentrations of ER (50 μM), in accordance to previous studies showing similar bioactivity of other isothiocyanates (ITCs). Our study reports for the first time that the induction of p53, p21 and PARP-1 cleavage may participate in the anti-proliferative activity of ER in human lung adenocarcinoma A549 cells. Comparison of data with those obtained with the isothiocyanate sulforaphane (SF), structurally related to ER, underlines the strong relationship between structural analogy of ITCs and their biological activity. The ability of dietary compounds to modulate molecular mechanisms that affect cancer cell proliferation is certainly a key point of the cancer prevention potential by functional foods.     

EGFR upregulates inflammatory and proliferative responses in human lung adenocarcinoma cell line (A549), induced by lower dose of cadmium chloride

Exposure to cadmium is associated with the development of pulmonary damage such as emphysema and lung cancer. This metal is also a powerful inducer of different proinflammatory and cell cycle regulatory proteins in many biologic models. Previously, we showed that prolonged exposure of low concentration of cadmium resulted in upregulation of proinflammatory cytokines and cell cycle regulatory molecules in mice lung cell. The present study was undertaken to determine molecular mechanism of inflammation and its relation to cell proliferation in a transformed human lung adenocarcinoma epithelial cell line (A549) in response to cadmium chloride. In comparative studies, we examine that short-duration exposure to lower doses of cadmium significantly increase the growth of A549 cells, whereas higher doses are toxic and cause cell death. We also observed that cadmium induced elevated expression of epidermal growth factor receptor (EGFR) along with different proinflammatory cytokines like interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). The possible occurrence of cell proliferation events was evaluated via analysis of the physical state of the DNA and the expression of Ki-67 and proliferating cell nuclear antigen (PCNA). We also checked the pattern of expression of different cell cycle regulatory molecules involved in the onset of cell proliferation. Our results indicate that cadmium treatment appears to induce inflammatory and growth responses in transformed A549 cell line by activating EGFR and its downstream modulators. These results may contribute to better understand the toxic mechanism of cadmium; moreover, the expression profile of cadmium-induced regulatory molecules could provide potential biomarkers for cadmium exposure.     

Basal and metal-induced expression of metallothionein isoform 1 and 2 genes in the RWPE-1 human prostate epithelial cell line

The human prostate gland has low basal expression of the metallothionein-1 and -2 proteins. In prostate cancer, MT-1/2 protein expression is variable and correlates directly with the increasing Gleason score of the tumor. The goal of the present study was to determine if the RWPE-1 cell line is a good model to elucidate the mechanisms underlying the alterations in MT-1/2 expression that occur during the development of prostate cancer. It was shown that the RWPE-1 cell line and in situ prostate tissue have identical expression profiles of MT-1 and MT-2 isoform-specific mRNAs (MT-1E, MT-1X and MT-2A) and similar levels of MT-1/2 protein. It was also shown that the RWPE-1 cells respond to Zn(+2) and Cd(+2) exposure by induction of the basally expressed MT mRNAs and the accumulation of high levels MT-1/2 protein (in excess of 10% of total protein). It was also shown that additional MT-1 mRNAs were expressed when the cells were exposed to either metal; MT-1A, MT-1F, MT-G and MT-1H for Cd(+2)-exposed cells; and, MT-1F, MT-G and MT-1H for Zn(+2)-exposed cells. The results suggest that RWPE-1 cells may be a valuable system to define the interplay between Zn(+2) concentration, Cd(+2) exposure and MT in normal and malignant prostate epithelial cells.     

A SENSITIVE,HIGH-CAPACITY RADIOIMMUNOASSAY FOR METALLOTHIONEIN AND ITS APPLICATION TO URINE SAMPLES FROM CADMIUM-TREATED RATS

A double-antibody radioimmunoassay (RIA) for metallothionein (MT) using sheep antiserum and its application to urine samples from rats chronically exposed to cadmium (Cd) are described. The procedure can be completed in two rather than the usual three days. The separation of the antigen-antibody complex is carried out in 96-well plates equipped with membrane filters. This assay format makes it possibletoprocess approximately 200 samples in quadruplicate with relative ease. Antiserum raised in sheep against a mixture of rat hepatic MT-1 and MT-2 reacted equally with both isomers of MT with a detection limit of about 1 ng/50muL urine or tissue homogenate. The usefulness of this highcapacity assay was further examined by analyzing the urinary MT levels of control rats and rats maintained on drinking water containing 100 mg Cd/L for up to 21 months. In the Cd-treated group, urinary MT gradually increased with the duration of exposure. After 6 months of exposure urinary MT was significantly higher in the Cd-treated group than in the control group and at 21 months reached 1mug/mg creatinine. Theresults indicatethat themodified highcapacity RIA is a sensitive, convenient, and reliable method for measuring MT in biological tissues and fluids. Application of the method to urine specimens from rats chronically exposed to Cd confirms an earlier finding that urinary MT is an indicator of Cd exposure.     

Chronic occupational exposure to arsenic induces carcinogenic gene signaling networks and neoplastic transformation in human lung epithelial cells

Chronic arsenic exposure remains a human health risk; however a clear mode of action to understand gene signaling-driven arsenic carcinogenesis is currently lacking. This study chronically exposed human lung epithelial BEAS-2B cells to low-dose arsenic trioxide to elucidate cancer promoting gene signaling networks associated with arsenic-transformed (B-As) cells. Following a 6 month exposure, exposed cells were assessed for enhanced cell proliferation, colony formation, invasion ability and in vivo tumor formation compared to control cell lines. Collected mRNA was subjected to whole genome expression microarray profiling followed by in silico Ingenuity Pathway Analysis (IPA) to identify lung carcinogenesis modes of action. B-As cells displayed significant increases in proliferation, colony formation and invasion ability compared to BEAS-2B cells. B-As injections into nude mice resulted in development of primary and secondary metastatic tumors. Arsenic exposure resulted in widespread up-regulation of genes associated with mitochondrial metabolism and increased reactive oxygen species protection suggesting mitochondrial dysfunction. Carcinogenic initiation via reactive oxygen species and epigenetic mechanisms was further supported by altered DNA repair, histone, and ROS-sensitive signaling. NF-κB, MAPK and NCOR1 signaling disrupted PPARα/δ-mediated lipid homeostasis. A ‘pro-cancer’ gene signaling network identified increased survival, proliferation, inflammation, metabolism, anti-apoptosis and mobility signaling. IPA-ranked signaling networks identified altered p21, EF1α, Akt, MAPK, and NF-κB signaling networks promoting genetic disorder, altered cell cycle, cancer and changes in nucleic acid and energy metabolism. In conclusion, transformed B-As cells with their whole genome expression profile provide an in vitro arsenic model for future lung cancer signaling research and data for chronic arsenic exposure risk assessment.     

Cadmium modulates adipocyte functions in metallothionein-null mice

Our previous study has demonstrated that exposure to cadmium (Cd), a toxic heavy metal, causes a reduction of adipocyte size and the modulation of adipokine expression. To further investigate the significance of the Cd action, we studied the effect of Cd on the white adipose tissue (WAT) of metallothionein null (MT^−/−) mice, which cannot form atoxic Cd–MT complexes and are used for evaluating Cd as free ions, and wild type (MT^+/+) mice. Cd administration more significantly reduced the adipocyte size of MT^−/− mice than that of MT^+/+ mice. Cd exposure also induced macrophage recruitment to WAT with an increase in the expression level of Ccl2 (MCP-1) in the MT^−/− mice. The in vitro exposure of Cd to adipocytes induce triglyceride release into culture medium, decrease in the expression levels of genes involved in fatty acid synthesis and lipid hydrolysis at 24 h, and at 48 h increase in phosphorylation of the lipid-droplet-associated protein perilipin, which facilitates the degradation of stored lipids in adipocytes. Therefore, the reduction in adipocyte size by Cd may arise from an imbalance between lipid synthesis and lipolysis. In addition, the expression levels of leptin, adiponectin and resistin decreased in adipocytes. Taken together, exposure to Cd may induce unusually small adipocytes and modulate the expression of adipokines differently from the case of physiologically small adipocytes, and may accelerate the risk of developing insulin resistance and type 2 diabetes.     

Apoptosis-inducing activity of synthetic hydrocarbon-stapled peptides in H358 cancer cells expressing KRASG12C

Lung cancers are the leading cause of cancer deaths worldwide and pose a grave threat to human life and health. Non-small cell lung cancer (NSCLC) is the most frequent malignancy occupying 80% of all lung cancer subtypes. Except for other mutations (e.g., KRAS^G12V/D) that are also vital for the occurrence, KRAS^G12C gene mutation is a significant driving force of NSCLC, with a prevalence of approximately 14% of all NSCLC patients. However, there are only a few therapeutic drugs targeting KRAS^G12C mutations currently. Here, we synthesized hydrocarbon-stapled peptide 3 that was much shorter and more stable with modest KRAS^G12C binding affinity and the same anti-tumor effect based on the α-helical peptide mimic SAH-SOS1_A. The stapled peptide 3 effectively induced G2/M arrest and apoptosis, inhibiting cell growth in KRAS-mutated lung cancer cells via disrupting the KRAS-mediated RAF/MEK/ERK signaling, which was verified from the perspective of genomics and proteomics. Peptide 3 also exhibited strong anti-trypsin and anti-chymotrypsin abilities, as well as good plasma stability and human liver microsomal metabolic stability. Overall, peptide 3 retains the equivalent anti-tumor activity of SAH-SOS1_A but with improved stability and affinity, superior to SAH-SOS1_A. Our work offers a structural optimization approach of KRAS^G12C peptide inhibitors for cancer therapy.     

Preferential induction of the AhR gene battery in HepaRG cells after a single or repeated exposure to heterocyclic aromatic amines

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) are two of the most common heterocyclic aromatic amines (HAA) produced during cooking of meat, fish and poultry. Both HAA produce different tumor profiles in rodents and are suspected to be carcinogenic in humans. In order to better understand the molecular basis of HAA toxicity, we have analyzed gene expression profiles in the metabolically competent human HepaRG cells using pangenomic oligonucleotide microarrays, after either a single (24-h) or a repeated (28-day) exposure to 10 μM PhIP or MeIQx. The most responsive genes to both HAA were downstream targets of the arylhydrocarbon receptor (AhR): CYP1A1 and CYP1A2 after both time points and CYP1B1 and ALDH3A1 after 28 days. Accordingly, CYP1A1/1A2 induction in HAA-treated HepaRG cells was prevented by chemical inhibition or small interference RNA-mediated down-regulation of the AhR. Consistently, HAA induced activity of the CYP1A1 promoter, which contains a consensus AhR-related xenobiotic-responsive element (XRE). In addition, several other genes exhibited both time-dependent and compound-specific expression changes with, however, a smaller magnitude than previously reported for the prototypical AhR target genes. These changes concerned genes mainly related to cell growth and proliferation, apoptosis, and cancer. In conclusion, these results identify the AhR gene battery as the preferential target of PhIP and MeIQx in HepaRG cells and further support the hypothesis that intake of HAA in diet might increase human cancer risk.