Kahalalide F induces necrosis-like cell death that involves depletion of ErbB3 and inhibition of Akt signaling

Kahalalide F (KF) is a novel marine-derived antitumor agent that is currently undergoing phase II clinical trials. The mechanism of action of KF is not well understood. In line with previous reports, we show that KF caused rapid and potent cytotoxicity in the breast cancer cell lines SKBR3 and BT474, characterized by cytoplasmic swelling and DNA clumping. Several markers of caspase-dependent apoptosis, such as phosphatidyl-serine externalization, cytochrome c release, and caspase-3 and poly-(ADP-ribose) polymerase cleavage were negative after KF exposure. Inhibitors of caspases or cathepsins failed to protect against KF cytotoxicity. Altogether, these data indicate that KF-induced cell death is a necrosis-like process. The sensitivity to KF in a panel of human tumor cell lines derived from breast (SKBR3, BT474, and MCF7), vulval (A431), non-small-cell lung (H460, A549, SW1573, and H292), and hepatic (Skhep1, HepG2, and Hep3B) carcinomas positively correlated with ErbB3 (HER3) protein levels. A KF-resistant subline of colon carcinoma cells, HT29/KF, expressed significantly reduced levels of all ErbB receptors, but short-term KF exposure of sensitive cell lines such as SKBR3 selectively induced down-regulation of ErbB3. On the other hand, stable transfection of an ErbB3-expressing plasmid increased the KF sensitivity of H460 cells, the most resistant cell line in our panel. Finally, we found that KF efficiently inhibited the phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway in sensitive cell lines and that ectopic expression of a constitutively active Akt mutant reduced KF cytotoxicity in this cell line. In summary, our results identify ErbB3 and the downstream PI3K-Akt pathway as important determinants of the cytotoxic activity of KF in vitro.     

Cytotoxic effects of glutathione synthesis inhibition by L-buthionine-(SR)-sulfoximine on human and murine tumor cells

The glutathione (GSH) synthesis inhibitor, buthionine sulfoximine (BSO) was tested for cytotoxicity and thiol depletion in murine and human tumor cells in vitro, and for its antitumor activity and toxicity in vivo. The cell lines used in these studies included murine L-1210 leukemia, human RPMI 8226 myeloma, MCF-7 breast cancer and WiDr colon carcinoma. Soft agar colony forming assays showed that BSO was most effective at reducing tumor colony formation when exposed continuously to cells in vitro. Drug concentrations which inhibited colony formation to 50% of control levels ranged from 2.0–6.2 mM (for 1 hour exposures), 2–100 mM for 24 hour exposures and 0.4–1.40 M (for continuous BSO exposures). Human myeloma cells proved most sensitive to BSO. In vitro cytotoxicity correlated with depletion of intracellular nonprotein sulfhydryls to 10% of control values in both L-1210 and 8226 cells. This was routinely achieved with prolonged exposures to mM BSO concentrations for > 24 hours. Normal mice tolerated high BSO doses (up to 5.0 g/kg) without evidence of acute toxicity. BSO was not active against L-1210 leukemia-bearing DBA/2 mice. When tested in vivo against MOPC-315 plasmacytoma-bearing BALB/c mice, BSO was not active at doses up to 4.0 g/kg. In contrast, the bifunctional alkylating agent melphalan (L-PAM) was active against MOPC-315 and this activity was enhanced by a 24 hour pretreatment of mice with 50 mg/kg of L-BSO. This BSO dose was shown to significantly reduce sulfhydryl levels in the liver (50% of control) and kidney (20% of control) but not in the bone marrow (100% of control). The enhancement by BSO was most significant only for the lower doses of L-PAM tested. These results suggest that BSO may not have direct antitumor activity, but that it can enhance cytotoxicity from a classic alkylating agent in vivo. Due to its low toxicity, BSO should be tested in combination with either anticancer agents which are dependent on (GSH) for detoxification and potential drug resistance.     

MMPT as a reactive oxygen species generator induces apoptosis via the depletion of intracellular GSH contents in A549 cells

MMPT, (5-[(4-methylphenyl)methylene]-2-(phenylamino)-4(5H)-thiazolone), a thiazolidin compound, was identified in our laboratory as a novel antineoplastic agent with a broad spectrum of antitumor activity against many human cancer cells. A previous study showed that MMPT inhibited cell growth, and induced apoptosis in H1792 cells. In this study, the antiproliferative activity of MMPT was investigated. The results showed that MMPT was able to inhibit A549 cell growth in a time- and dose-dependent manner by blocking cell cycle progression in the G2 phase and inducing apoptosis. MMPT induced DNA fragmentation and caspase activation in A549 cells, both of which are hallmarks of apoptosis. The apoptotic process was accompanied by the generation of reactive oxygen species, depletion of glutathione (GSH), and reduction the GSH/GSSG ratio, suggesting that MMPT may induce apoptosis in A549 cells through a reactive oxygen species dependent pathway. Treatment with a thiol antioxidant, NAC, showed the recovery of GSH depletion and the reduction of reactive oxygen species levels in MMPT-treated cells, which were accompanied by the inhibition of apoptosis. In contrast, L-buthionine sulfoximine (BSO), a well-known inhibitor of GSH synthesis, aggravated GSH depletion and cell death in MMPT-treated cells. In conclusion, we have demonstrated that MMPT inhibits the growth of A549 cells by inducing a G2 arrest of the cell cycle and by triggering apoptosis accompanied with the depletion of GSH.     

Inhibition of topoisomerase I activity and efflux drug transporters’ expression by xanthohumol from hops

Xanthohumol (XN) and its related compounds were evaluated for their cytotoxicity against four different human cancer cell lines, A549 (lung), SK-OV-3 (ovarian), SK-MEL-2 (melanoma), and HCT-15 (colon) using a sulforhodamine B assay. XN showed the most active cytotoxicity against the human cancer cell lines. Isoxanthohumol, 8-prenylnaringenin, and xanthohumol 4'-O-beta-D-glucopyranoside showed comparable cytotoxicity and (2S)-5-methoxy-8-prenylnaringenin 7-O-beta-D-glucopyranoside was the least cytotoxic compound. The anticancer properties of XN, the most active cytotoxic compound, were further investigated. XN showed an inhibitory effect on the activity of DNA topoisomerase I (topo I), which was measured from the relaxation of supercoiled DNA. The inhibition of topo I by XN might explain the cytotoxicity against the human cancer cell lines. Moreover, the expression of the drug efflux genes was investigated to predict the drug resistance. XN clearly decreased the mRNA levels of ABCB1 (MDR1), ABCC1 (MRP1), ABCC2 (MRP2), and ABCC3 (MRP3). These results suggest that XN has anticancer properties by inhibiting the topo I activity and it might be used in conjunction with other anticancer chemotherapeutic agents to reduce the drug resistance inhibiting the efflux drug transporters.     

Contribution of glutathione and metallothioneins to protection against copper toxicity and redox cycling: quantitative analysis using MT+/+ and MT-/- mouse lung fibroblast cells

Glutathione (GSH) and metallothioneins (MT) are believed to play important roles in protecting cells against high copper (Cu) concentrations. Little is known, however, about their specific intracellular interactions and the coordination of protective functions. We investigated contributions of GSH and MT to protection against Cu toxicity in fibroblasts derived from wild-type (MT+/+) and knockout (MT-/-) mice that were challenged with cupric nitrilotriacetate (Cu-NTA). Endogenous levels of GSH and MT were manipulated using an inhibitor of gamma-glutamylcysteine synthetase, buthionine sulfoximine (BSO, 5 microM), as GSH depletor and ZnCl(2) (100 microM) as inducer of MT expression. BSO pretreatment markedly decreased cellular GSH levels in MT+/+ and MT-/- cells, by 65% and 70%, respectively, which resulted in Cu cytotoxicity accompanied by its elevated redox-cycling activity and enhanced Cu-induced membrane phospholipid peroxidation. BSO-pretreated MT-/- cells were markedly more sensitive to Cu despite the fact that the residual levels of GSH were similar in both BSO-pretreated MT+/+ and MT-/- cells. Zn pretreatment resulted in more than 10-fold induction of MT in MT+/+ cells but not in MT-/- cells. Accordingly, Zn pretreatment afforded significant protection of MT+/+ cells against Cu cytotoxicity, likely associated with MT-dependent suppression of Cu redox-cycling activity and phospholipid peroxidation, but it exerted no protection in MT-/- cells (as compared to naive cells). To determine whether MT functions specifically in Cu regulation or rather acts as a nonspecific Cu-binding cysteine-rich nucleophile, experiments were performed using MT+/+ and MT-/- cells pretreated with both BSO and Zn. BSO pretreatment did not affect Zn-induced MT expression in MT+/+ cells. As compared with BSO pretreatment alone, exposure to Cu of MT+/+ cells after Zn/BSO pretreatment resulted in the following: (i) a significantly higher viability; (ii) attenuated Cu-dependent redox-cycling activity; and (iii) a lower level of phospholipid peroxidation. In BSO/Zn-pretreated MT-/- cells, the redox-cycling activity of Cu and the level of phospholipid peroxidation remained remarkably higher than in naive cells and were not significantly different from those in cells pretreated with BSO alone. Cu-induced toxicity was remarkably higher in BSO/Zn-pretreated MT-/- cells than in naive or Zn-pretreated cells, although slightly lower than in the MT-/- cells pretreated with BSO alone.     

三氧化二砷对人肺腺癌A549/R细胞多药耐药相关蛋白表达的影响

目的探讨三氧化二砷(As2O3)对人肺腺癌A549/R细胞耐药性的逆转作用及对多药耐药相关蛋白（MRP）表达的影响。方法以荧光分光光度计测定细胞内药物浓度的改变，采用半定量逆转录聚合酶联反应(RT PCR) 技术检测As2O3处理后A549/R MRP基因表达的变化。结果As2O3的非细胞毒性剂量可增加A549/R细胞内多柔比星(ADM)浓度，降低其IC50。A549/R细胞中MRP呈过表达状态，不同浓度的As2O3处理A549/R后MRP表达水平明显降低。结论As2O3可部分逆转A549/R细胞对ADM的耐药性，其逆转机制与改变MRP基因表达有关。     

The role of reduced glutathione and glutathione reductase in the cytotoxicity of chromium (VI) in osteoblasts.

It is accepted that to exert cytotoxicity and carcinogenicity chromium VI has to be reduced inside cells. The role of reduced glutathione (GSH) and glutathione reductase in the intracellular reduction of Cr VI was investigated using an immortalized rat osteoblast cell line, FFC. Alkaline phosphatase activity was the index of cytotoxicity measured. To investigate the role of GSH in Cr VI toxicity, GSH levels in the cells were elevated by pretreatment with L-cysteine, and depleted using buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. Intracellular GSH levels were not depleted during the metabolism of Cr VI. Depletion of GSH by BSO caused the cells to be more resistant to the toxicity of Cr VI, indicating that GSH is involved in reduction of the Cr VI. Inhibition of glutathione reductase by carmustine (BCNU) partially protected against the cytotoxicity of Cr VI irrespective of the intracellular GSH. The cytotoxic response was similar if cells were pretreated with BCNU plus L-cysteine, or with BCNU plus BSO, although the GSH levels were markedly different. The results indicate that glutathione reductase plays an important role in the intracellular reduction of Cr VI in osteoblasts.     

Reversal of P-glycoprotein and multidrug resistance-associated protein 1 mediated multidrug resistance in cancer cells by HZ08 Isomers, tetrataisohydroquinolin derivatives

Overexpression of P-glycoprotein (Pgp) and multidrug resistance protein 1 (MRP1) by tumors results in multidrug resistance (MDR) to structurally unrelated anti-tumor agents. HZ08, a chiral compound, was a newly synthesized tetraisohydroquinoline derivative to reverse Pgp and MRP1 mediated MDR. In present studies, R, S-HZ08 and their racemate reversed the resistance to adriamycin and vincristine of adriamycin-selected human leukemia (K562/ADM) cells that overexpress Pgp. R, S-HZ08 and their racemate modulated adriamycin cytotoxicity when R, S-HZ08 and their racemate were removed 12 h prior to the cytotoxicity assay. In addition, R, S-HZ08 and their racemate increased intracellular accumulation of Rhodamine123 in Caco-2 cells that overexpress Pgp. Furthermore, using a DNA content analysis and an annexin V binding assay, R, S-HZ08 and their racemate effectively reversed the resistance to adriamycin-induced apoptosis in K562/ADM cells. R, S-HZ08 and their racemate also moderately reversed the resistance to adriamycin and vincristine of MCF-7/ADM cells that overexpress MRP1. However, R, S-HZ08 and their racemate hardly affected intracellular glutathione (GSH) levels and glutathione S-transferase (GST) activities in MCF-7/ADM cells. The result showed that R, S-HZ08 and their racemate possibly reverse MDR1 mediated multidrug resistance by a direct interaction with MRP1, not interaction with MRP1 via GSH. Thus, R, S-HZ08 and their racemate should be useful for treating patients with tumors that overexpress both Pgp and MRP1.     

Iron is not involved in oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin

BACKGROUND AND PURPOSE: The anticancer drugs doxorubicin and bleomycin are well-known for their oxidative stress-mediated side effects in heart and lung, respectively. It is frequently suggested that iron is involved in doxorubicin and bleomycin toxicity. We set out to elucidate whether iron chelation prevents the oxidative stress-mediated toxicity of doxorubicin and bleomycin and whether it affects their antiproliferative/proapoptotic effects. EXPERIMENTAL APPROACH: Cell culture experiments were performed in A549 cells. Formation of hydroxyl radicals was measured in vitro by electron paramagnetic resonance (EPR). We investigated interactions between five iron chelators and the oxidative stress-inducing agents (doxorubicin, bleomycin and H(2)O(2)) by quantifying oxidative stress and cellular damage as TBARS formation, glutathione (GSH) consumption and lactic dehydrogenase (LDH) leakage. The antitumour/proapoptotic effects of doxorubicin and bleomycin were assessed by cell proliferation and caspase-3 activity assay. KEY RESULTS: All the tested chelators, except for monohydroxyethylrutoside (monoHER), prevented hydroxyl radical formation induced by H(2)O(2)/Fe(2+) in EPR studies. However, only salicylaldehyde isonicotinoyl hydrazone and deferoxamine protected intact A549 cells against H(2)O(2)/Fe(2+). Conversely, the chelators that decreased doxorubicin and bleomycin-induced oxidative stress and cellular damage (dexrazoxane, monoHER) were not able to protect against H(2)O(2)/Fe(2+). CONCLUSIONS AND IMPLICATIONS: We have shown that the ability to chelate iron as such is not the sole determinant of a compound protecting against doxorubicin or bleomycin-induced cytotoxicity. Our data challenge the putative role of iron and hydroxyl radicals in the oxidative stress-mediated cytotoxicity of doxorubicin and bleomycin and have implications for the development of new compounds to protects against this toxicity.     

Cytotoxic-antineoplastic activity of acetyl derivatives of prenylnaphthohydroquinone

Several acetyl derivatives of prenylnaphthohydroquinone have been synthetized and evaluated for their cytotoxicity against A-549 human lung carcinoma and H-116 human colon carcinoma neoplastic cells. The IC50 values against A-549 are compared with those observed for previously reported unsubstituted derivatives.     

Modulation of cisplatin cytotoxicity and cisplatin-induced DNA cross-links in HepG2 cells by regulation of glutathione-related mechanisms

Glutathione (GSH), glutathione S-transferase (GST), and glutathione conjugate export pump (GS-X pump) have been shown to participate collectively in the detoxification of many anticancer drugs, including cisplatin. Identification and regulation of the rate-limiting step in the overall system for cisplatin detoxification is of crucial importance for sensitization of human tumor cells to cisplatin. In this study, the GSH content, GST activity, and GS-X pump activity were regulated separately to examine effects of the regulation on cisplatin cytotoxicity and cisplatin-induced DNA interstrand cross-links (ICL) in HepG2 cells. Seventy-percent depletion of GSH by buthionine sulfoximine (BSO) and 50% increase of GSH by monoethyl GSH ester (GSHe) potentiated and decreased cisplatin cytotoxicity, respectively. This was reflected by a significant decrease and increase of their respective IC(50) values by 62 and 107%. Cisplatin-induced ICL was also potentiated by depletion of GSH by BSO and decreased by enrichment of GSH by GSHe, as shown by a 125% increase and a 34% decrease of cross-linked DNA compared with control samples exposed to cisplatin alone (p = 0.008 and 0.03, respectively). On the other hand, inhibition of GST and GS-X pump by ethacrynic acid, quercetin, tannic acid, and indomethacin at concentrations that inhibited activities of GST and GS-X pump by more than 50% had no significant effects on cisplatin cytotoxicity and cisplatin-induced DNA ICL in these cells. The results showed that of the parameters measured, intracellular GSH seems to be the rate-limiting factor, and its regulation would provide a more promising strategy for sensitization of human liver tumor cells to cisplatin.     

Anti-tumorigenic activity of sophoflavescenol against Lewis lung carcinoma in vitro and in vivo

This study examined the in vitro cytotoxic activity and in vivo antitumor activity as well as intracellular apoptotic capacities of a prenylated flavonol, sophoflavescenol from Sophora flavescens, to evaluate prospective anti-tumorigenic drugs, and antitumor potential. In addition, the in vitro antioxidant and anti-inflammatory capacities were evaluated. Despite the small effect on human breast adenocarcinoma (MCF-7), sophoflavescenol showed cytotoxicity against human leukaemia (HL-60), Lewis lung carcinoma (LLC), and human lung adenocarcinoma epithelial (A549) cells. Interestingly, it also exerted potent in vivo antitumor activity by tumor growth inhibition in the LLC tumor model as well as apoptotic activity by caspase-3 activation in HL-60 cells. In addition, it exhibited potent antioxidant activities in 1,1-diphenyl-2-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radicals and lipid peroxidation assays. Sophoflavescenol exerted notable anti-inflammatory activity by inhibiting nitric oxide generation and tert-butylhydroperoxide-induced ROS generation rather than inhibiting nuclear factor kappa B activation in RAW 264.7 cells. The findings show that the antioxidant, anti-inflammatory, and apoptotic activities of sophoflavescenol might contribute to the antitumor activity without severe side effects, highlighting its potential for chemoprevention and/or anticancer drugs due to multi-effective targets in almost all stages of tumorigenesis, including initiation, promotion, and progression.     

Nanotoxicity of pure silica mediated through oxidant generation rather than glutathione depletion in human lung epithelial cells

Though, oxidative stress has been implicated in silica nanoparticles induced toxicity both in vitro and in vivo, but no similarities exist regarding dose–response relationship. This discrepancy may, partly, be due to associated impurities of trace metals that may present in varying amounts. Here, cytotoxicity and oxidative stress parameters of two sizes (10 nm and 80 nm) of pure silica nanoparticles was determined in human lung epithelial cells (A549 cells). Both sizes of silica nanoparticles induced dose-dependent cytotoxicity as measured by MTT [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] and lactate dehydrogenase (LDH) assays. Silica nanoparticles were also found to induce oxidative stress in dose-dependent manner indicated by induction of reactive oxygen species (ROS) generation, and membrane lipid peroxidation (LPO). However, both sizes of silica nanoparticles had little effect on intracellular glutathione (GSH) level and the activities of glutathione metabolizing enzymes; glutathione reductase (GR) and glutathione peroxidase (GPx). Buthionine-[S,R]-sulfoximine (BSO) plus silica nanoparticles did not result in significant GSH depletion than that caused by BSO alone nor N-acetyl cysteine (NAC) afforded significant protection from ROS and LPO induced by silica nanoparticles. The rather unaltered level of GSH is also supported by finding no appreciable alteration in the level of GR and GPx. Our data suggest that the silica nanoparticles exert toxicity in A549 cells through the oxidant generation (ROS and LPO) rather than the depletion of GSH.     

Buthionine sulfoximine inhibition of cystine uptake and glutathione biosynthesis in human lung carcinoma cells

Intracellular glutathione (GSH) content of human lung carcinoma cells, A549, in log phase was 25 +/- 5 nmol/10(6) cells, which is considerably higher than that reported in other tumor cells. After partial depletion of GSH with diethyl maleate (DEM), addition of cystine to the medium allowed full resynthesis of GSH in 4 hr, cysteine in the same time period led to less resynthesis, and methionine provided minimal resynthesis. Using cystine as the sole sulfur source and with buthionine sulfoximine (BSO, 5 mM) included in the medium after cells were depleted with DEM, inhibition of both cystine uptake and resynthesis of GSH occurred. BSO inhibited [35S]cystine uptake (as early as 10 min) in a concentration-dependent process, ranging from a 28% decrease for 1 microM BSO to an 85% decrease for 100 microM BSO compared to the control cells after 240 min of incubation. In addition, GSH resynthesis from [35S]cystine for 240 min was inhibited in a parallel dose-dependent manner, in that 1 microM BSO caused a 27% decrease and 100 microM BSO provided a 75% decrease from control values. BSO did not inhibit the uptake of [35S]methionine, but inhibited the low amount of resynthesis of GSH when methionine was the sole sulfur source. BSO did not inhibit the uptake of arginine, phenylalanine, and leucine. DL-, L-, and methyl ester-BSO each inhibited [35S]cystine uptake and incorporation into GSH to a similar extent. The half-life of GSH was 3.5 +/- 0.4 hr in A549 cells that were grown in complete medium with GSH synthesis occurring.     

Role of the lung resistance-related protein (LRP) in the drug sensitivity of cultured tumor cells.

Drug resistance, one of the major obstacle in the successful anticancer therapy, can be observed at the outset of therapy (intrinsic resistance) or after exposure to the antitumor agent (acquired resistance). To gain a better insight into the mechanisms of intrinsic resistance we have analyzed two human cell types derived from untreated tumors: MCF-7 breast cancer and A549 non small cell lung cancer (NSCLC). We have examined: the cytotoxic effect induced by doxorubicin (DOX); the time course of drug accumulation by flow cytometry and intracellular drug distribution by confocal microscopy; the expression and distribution of proteins related to anthracycline resistance, such as P-gp (P-glycoprotein), MRP1 (multidrug resistance-associated protein) and LRP (lung resistance-related protein). The cytotoxicity assays showed that A549 cells were less sensitive than MCF-7 cells to the DOX treatment in agreement with the different DOX uptake. Moreover, while in A549 cells DOX was mostly located in well defined intracytoplasmic vesicles, in MCF-7 cells it was mainly revealed inside the nuclei. The analysis of P-gp and MRP expression did not show significant differences between the two cell lines while a high expression of LRP was detected at the nuclear envelope and cytoplasmic levels in A549 cells. These findings suggest that the lower sensitivity to DOX treatment showed by lung carcinoma cells could be ascribed to drug sequestration by LRP inside the cytoplasmic compartments.     

Effects of cooking oil fumes on the genotoxicity and oxidative stress in human lung carcinoma (A-549) cells.

This study investigates the genotoxicity and cytotoxicity of oil fumes, formed when peanut oil is heated, on human lung carcinoma pulmonary type II-like epithelium cells. The major mutagenic compound (trans-trans-2,4-decadienal, t-t-2,4-DDE) contained in oil fumes and its effect on the induction of reactive oxygen species (ROS) is also discussed. The results indicate that the methanolic extract of oil fumes can apparently lead to cytotoxicity and oxidative DNA damage. Glutathione (GSH) content, and the activities of antioxidative enzymes such as GSH reductase, GSH peroxidase and GSH S-transferase were adversely reduced by the methanolic extract of oil fumes. t-t-2,4-DDE could produce superoxide anion, hydrogen peroxide and hydroxyl radicals in a phosphate buffer (pH 7.4), and form intracellular ROS, determined by dichlorofluorescein assay in A-549 cells. Moreover, t-t-2,4-DDE caused significant (P <0.05) oxidative damage of the 8-hydroxy-2'-deoxyguanosine formation in A-549 cells at concentrations from 50 to 200 microM. These results demonstrated that the DNA damage in A-549 cells, induced by t-t-2,4-DDE, was related to the ROS formation. The occurrence of t-t-2,4-DDE, therefore, was of significance in the genotoxicity of oxidized oil and fumes.     

Induction of apoptosis in lung adenocarcinoma and glioma cells by some oxadiazole derivatives

Oxadiazoles have received much attention due to their wide range of biological activities including antitumor activity. In this study, we aimed to study apoptotic effects of some 1,3,4-oxadiazole derivatives on human lung adenocarcinoma (A549) and rat glioma (C6) cell lines. The cytotoxicity of the compounds on both cell lines was determined, and the effects of these compounds on DNA synthesis were measured. Compounds 2 and 6 which exhibited significant cytotoxic activity in MTT assay were chosen for flow cytometric analyses to determine apoptotic percent of cells. These compounds also exhibited better DNA synthesis inhibition activity on cancer cells. Compound 6 carrying 2,4-dichlorophenyl substituent exhibited the highest apoptotic effect on A549 cells via the induction of Caspase 3 activity. It was suggested that compounds 2 and 6 can be identified as the most promising anticancer agents against A549 and C6 cancer cell lines.     

Effect of glutathion on cadmiuminduced cytotoxicity in nasopharyngeal carcinoma cell

To study the possible role of glutathion (GSH) in cadmium-induced anti-tumor effects on human nasopharyngeal carcinoma(NPC).CNE1 cell line was treated with CdCl2,and together with N-acetyl cysteine(NAC),the predecessor of GSH,or with L-buthionine-[S,R]-sulfoximine (BSO),a selective inhibitor of GSH synthesis.The intracellular GSH level,the LDH leakage and MTT assay were measured.Results showed that there was remarkable proliferation in NAC CdCl2 treated CNE1 cells,with high activity of GSH.However,in BSO CdCl2 exposed cells,with low level GSH,the proliferation was significantly inhibited.It was indicated that GSH depletion would sensitize the inducible cytotoxicity in NPC cell,which correlated with cadmium-induced anticancer effects.     

The selective effect of genistein on the toxicity of bleomycin in normal lymphocytes and HL-60 cells

This study was carried out to find whether genistein might enhance bleomycin induced cytotoxicity in human leukemia (HL-60) while protecting normal blood lymphocytes. Despite the excellent chemotherapeutic effect of bleomycin, its cytotoxicity and genotoxicity in normal cells remains a major problem in chemotherapy. Genistein, one of the major Soy isoflavones, is particularly effective in quenching free radicals generated by toxic agents. In this study, the protective and enhancement effects of genistein on bleomycin induced cytotoxicity in HL-60 cells and blood lymphocytes were demonstrated. HL-60 cells were treated with various concentrations of genistein for 3 h followed by treatment with various concentrations of bleomycin during the G1 phase. Pretreatment of genistein increased micronuclei (MN) frequency and DNA damage as a result of bleomycin treatment. However, when human lymphocytes were pretreated with genistein prior to bleomycin treatment during the G2 or G0 phase, the frequencies of bleomycin induced MN was decreased. Although the extent of bleomycin induced DNA damage determined by single cell gel electrophoresis was increased through the pretreatment of genistein in HL-60 cells, it was decreased in normal lymphocytes. The result of this study may therefore provide great impact on the potential activity of genistein as a therapeutic agent.