Different roles of spermine in glucocorticoid- and Fas-induced apoptosis

PA-MSHA in combination with EGFR tyrosine kinase inhibitor: A new strategy to overcome the drug resistance of non-small cell lung cancer cells

The inhibition of epidermal growth factor receptor (EGFR) signaling by Gefitinib provides a promising treatment strategy for non-small cell lung cancer (NSCLC); however, drug resistance to Gefitinib and other tyrosine kinase inhibitors presents a major issue. Using NSCLC cell lines with differential EGFR status, we examined the potency of PA-MSHA (Pseudomonas aeruginosa-mannose-sensitive hemagglutinin) in combination with Gefitinib on proliferation, apoptosis, cell cycle arrest, EGFR signaling and tumor growth. PC-9, A549, and NCI-H1975 cells were treated with PA-MSHA, Gefetinib, or PA-MSHA plus Gefetinib at different concentrations and times. The effects of the drugs on proliferation, cell cycle distribution and apoptosis were evaluated. The activation of EGFR and apoptotic signaling-related molecules was evaluated by Western blotting in the presence or absence of EGFR siRNA. Tumor growth and pathway signaling activation was assessed by xenografts in nude mice. A time-dependent and concentration-dependent cytotoxic effect of PA-MSHA was observed in all NSCLC cells tested. The combination of PA-MSHA plus Gefitinib enhanced the growth inhibition, sub-G1 content and apoptosis over that observed with either agent alone. Furthermore, the combination of PA-MSHA plus Gefitinib resulted in caspase-3/caspase-9 cleavage and increased inhibition of EGFR-dependent activation of AKT and ERK phosphorylation. Combination treatment was more effective in reducing tumor size and EGFR activation than either agent alone. These data suggest that PA-MSHA and Gefitinib function additively to suppress the proliferative effects of NSCLC cells of differential EGFR status. The combination of PA-MSHA and Gefitinib provides a potential new strategy to conquer drug resistance for anti-EGFR-targeted therapy of NSCLC.

PA-MSHA inhibits proliferation and induces apoptosis in human non-small cell lung cancer cell lines with different genotypes

The present study examined the potential of Pseudomonas aeruginosa-mannose sensitive hemagglutinin (PA-MSHA) to inhibit proliferation and induce apoptosis in non‑small‑cell lung cancer (NSCLC) cell lines. It also investigated its mechanisms of action in different genotypes of human NSCLC. A total of three NSCLC cell lines, PC‑9, A549, and NCI‑H1975, were treated with PA‑MSHA at different concentrations. The anti‑proliferative effect of PA‑MSHA was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell cycle distribution and apoptosis induced by the treatment were measured by flow cytometry (FCM) with Annexin V/propidium iodide staining. Western blotting was conducted to determine the expression level of apoptosis‑associated proteins. PA‑MSHA was demonstrated to exert a time‑ and concentration‑dependent cytotoxic effect in PC‑9, A549, and NCI‑H1975 cells. The FCM indicated that all the different concentrations of PA‑MSHA used in the present study induce apoptosis and cell cycle arrest of NSCLC cells. Treatment with PA‑MSHA may exert anti‑proliferative effects on NSCLC cells by affecting regulation of the cell cycle and inducing apoptosis that is mediated in part by an intrinsic apoptosis signaling pathway. These data suggest that PA‑MSHA has the potential to inhibit proliferation and induce apoptosis in NSCLC cells. Furthermore, these data provide mechanistic details for the potential application of PA‑MSHA‑based therapeutic strategies for the treatment of different NSCLC genotypes. This present study suggests potential novel strategies to maximize effective therapeutic strategies targeting anti‑epidermal growth factor receptor for future clinical trials.

Downregulation of the polyamine regulator spermidine/spermine N(1)-acetyltransferase by Epstein-Barr virus in a Burkitt's lymphoma cell line

Transition of Akata Burkitt's lymphoma (BL) from a malignant to nonmalignant phenotype upon loss of Epstein-Barr virus (EBV) is evidence for a viral contribution to tumorigenesis despite the tight restriction of EBV gene expression in BL. Examination of global cellular gene expression in Akata subclones that retained or lost EBV identified spermidine/spermine N(1)-acetyltransferase (SAT1), an inducible enzyme whose catabolism of polyamines affects both apoptosis and cell growth, as one of a limited number of cellular genes downregulated by EBV. Re-infection of the EBV-negative Akata clone reduced SAT1 mRNA to a level comparable with the parental EBV-positive Akata. EBV-positive Akata cells demonstrated decreased SAT1 enzyme activity concomitant with altered intracellular polyamine constituents. Reduction of SAT1 in EBV-positive BL was a transcriptional effect. Forced expression of the viral BCL2 homologue, BHRF1, in an EBV-negative Akata clone reduced SAT1 mRNA. Thus, EBV repression of polyamine catabolism becomes a complementary alteration to dysregulated c-myc enhancement of polyamine synthesis in BL and favorable to BL lymphomagenesis.

Gallic acid as a cancer-selective agent induces apoptosis in pancreatic cancer cells

BACKGROUND

Gallic acid (GA) is a plant phenol isolated from water caltrop which is reported to have anti-inflammatory and anti-cancer effects. In this study, the antiproliferative effect of GA on human pancreatic cancer cell lines CFPAC-1 and MiaPaCa-2 as well as hepatocytes HL-7702 as normal cells was examined. Particularly, the mechanism of GA-induced apoptosis in MiaPaCa-2 cells in vitro was further studied.

METHODS

Cell viability was measured using SRB assay, and apoptosis was detected by Hoechst staining and annexin V-PI staining assays. Mitochondrial membrane potential was detected by rhodamine-123 staining. Flow cytometry analysis was employed to detect the apoptosis-related events.

RESULTS

GA inhibited the proliferation of CFPAC-1 and MiaPaCa-2 cells in a time- and dose-dependent manner, with IC(50)S of 102.3 ± 2.4 and 135.2 ± 0.6 µM at 48 h, respectively. GA treatment led to the increased proportion of cell apoptosis from 12.5 ± 0.72 to 78.3 ± 2.48% at the concentrations of 6.25 and 25.0 µg/ml, which was evidenced again by chromatins staining assay. Also, GA activated caspase-3, caspase-9, and reactive oxygen species, elevated Bax expression and [Ca(2+)](i) and reduced mitochondrial membrane potential (ΔΨm) in MiaPaCa-2 cells. Remarkably, when compared with human normal cells HL-7702 (IC(50) >100 µg/ml), GA showed selective toxicity for cancer cells.

CONCLUSIONS

GA can function as a cancer-selective agent by inducing apoptosis in MiaPaCa-2 cells via the mitochondria-mediated pathways. To the best of our knowledge, GA should open up new opportunities for the therapy of pancreatic cancer.

A potent lead induces apoptosis in pancreatic cancer cells

Pancreatic cancer is considered a lethal and treatment-refractory disease. To obtain a potent anticancer drug, the cytotoxic effect of 2-(benzo[d]oxazol-3(2H)-ylmethyl)- 5-((cyclohexylamino)methyl)benzene-1,4-diol, dihydrochloride (NSC48693) on human pancreatic cancer cells CFPAC-1, MiaPaCa-2, and BxPC-3 was assessed invitro. The proliferation of CFPAC-1, MiaPaCa-2, and BxPC-3 is inhibited with IC₅₀ value of 12.9±0.2, 20.6±0.3, and 6.2±0.6 µM at 48 h, respectively. This discovery is followed with additional analysis to demonstrate that NSC48693 inhibition is due to induction of apoptosis, including Annexin V staining, chromatins staining, and colony forming assays. It is further revealed that NSC48693 induces the release of cytochrome c, reduces mitochondrial membrane potential, generates reactive oxygen species, and activates caspase. These results collectively indicate that NSC48693 mainly induces apoptosis of CFPAC-1, MiaPaCa-2, and BxPC-3 cells by the mitochondrial-mediated apoptotic pathway. Excitingly, the study highlights an encouraging inhibition effect that human embryonic kidney (HEK-293) and liver (HL-7702) cells are more resistant to the antigrowth effect of NSC48693 compared to the three cancer cell lines. From this perspective, NSC48693 should help to open up a new opportunity for the treatment of patients with pancreatic cancer.

Codonopsis lanceolata extract induces G0/G1 arrest and apoptosis in human colon tumor HT-29 cells--involvement of ROS generation and polyamine depletion

Codonopsis lanceolata (Campanulasea) is widely distributed and grown in Asia and has been in use as traditional medicine for long time. The n-butanol fraction (BF) of C. lanceolata significantly inhibited human colon cancer HT-29 cell growth in a dose- and time-dependent manner by inducing G0/G1 phase arrest and apoptosis. The inhibition was associated with intracellular ROS generation and polyamine depletion as evidenced by HPLC quantitatively. Additionally, semi-quantitative RT-PCR revealed enhanced expression of caspase-3, p53, and the Bax/Bcl-2 ratio and reduced expression of survivin in HT-29 cells treated with BF. Furthermore, western blot analysis of p53, JNK, and caspase-3 showed that ROS generation was accompanied by JNK activation. Increase of the Bax/Bcl-2 ratio and activation of caspase-3 might be due to intracellular polyamine depletion. Conclusively, the findings of this study imply a critical role of ROS and polyamine depletion in the anticancer effects of C. lanceolata root extract.

Metabolic correlations of glucocorticoids and polyamines in inflammation and apoptosis

Glucocorticoid hormones (GC) are essential in all aspects of human health and disease. Their anti-inflammatory and immunosuppressive properties are reasons for therapeutic application in several diseases. GC suppress immune activation and uncontrolled overproduction and release of cytokines. GC inhibit the release of pro-inflammatory cytokines and stimulate the production of anti-inflammatory cytokines. Investigation of GC's mechanism of action, suggested that polyamines (PA) may act as mediators or messengers of their effects. Beside glucocorticoids, spermine (Spm) is one of endogenous inhibitors of cytokine production. There are many similarities in the metabolic actions of GC and PA. The major mechanism of GC effects involves the regulation of gene expression. PA are essential for maintaining higher order organization of chromatin in vivo. Spermidine and Spm stabilize chromatin and nuclear enzymes, due to their ability to form complexes with negatively charged groups on DNA, RNA and proteins. Also, there is an increasing body of evidence that GC and PA change the chromatin structure especially through acetylation and deacetylation of histones. GC display potent immunomodulatory activities, including the ability to induce T and B lymphocyte apoptosis, mediated via production of reactive oxygen species (ROS) in the mitochondrial pathway. The by-products of PA catabolic pathways (hydrogen peroxide, amino aldehydes, acrolein) produce ROS, well-known cytotoxic agents involved in programmed cell death (PCD) or apoptosis. This review is an attempt in the better understanding of relation between GC and PA, naturally occurring compounds of all eukaryotic cells, anti-inflammatory and apoptotic agents in physiological and pathological conditions connected to oxidative stress or PCD.

Conjugation of substituted naphthalimides to polyamines as cytotoxic agents targeting the Akt/mTOR signal pathway

Though several naphthalimide derivatives have exhibited antitumor activity in clinical trials, some issues such as toxicity prompted further structural modifications on the naphthalimide backbone. A series of naphthalimides conjugated with polyamines were synthesized to harness the polyamine transporter (PAT) for drug delivery, which was beneficial for the tumor cell selectivity. Bioevaluation in human hepatoma HepG2 cells treated with alpha-difluoromethylornithine (DFMO) or spermidine (Spd), human hepatoma Bel-7402 and normal QSG-7701 hepatocyte confirmed the PAT recognition and cell selectivity. In addition, the novel naphthalimide polyamine conjugate kills cells via apoptosis, and the Akt/mTOR signal pathway was first identified as the upstream cellular target through the apoptotic mechanism research. The presence of DFMO or Spd only either elevated or attenuated the cell apoptosis, but did not change the signal pathway. Collectively, the proper polyamine recognition element (i.e., homospermidine) mediated effective drug delivery via the PAT, and helped the proper cytotoxic goods (i.e., diverse naphthalimides) exert antitumor properties.

Pseudomonas aeruginosa: mannose sensitive hemagglutinin inhibits the growth of human hepatocarcinoma cells via mannose-mediated apoptosis

A vaccine derived from the outer membrane proteins of the Gram-negative bacterium Pseudomonas aeruginosa has been shown to have immune modulatory properties. An inactivated mutant strain of P. aeruginosa with mannose sensitive hemagglutinin fimbria (PA-MSHA) has been used for adjuvant therapy for malignant cancer. In this study, the growth of human hepatocellular carcinoma Hep G2 and BEL-7402 cells is inhibited by PA-MSHA, but not by mannose-cleaved PA-MSHA. PA-MSHA-treated cells arrested in the S phase of the cell cycle and underwent apoptosis. We hypothesize that apoptosis induced by treatment of Hep G2 and BEL-7402 cells with PA-MSHA is mediated by the mannose residues of PA-MSHA and is propagated through the extrinsic apoptosis pathway directly through caspase-8. These data provide mechanistic details for the potential application of PA-MSHA-based treatment of hepatocellular carcinoma.

A novel homospermidine conjugate inhibits growth and induces apoptosis in human hepatoma cells

AIM

To elucidate the mechanism responsible for the antiproliferative effects of a novel homospermidine conjugate, anthracenylmethyl homospermidine (ANTMHspd), in the human hepatoma BEL-7402 cell line.

METHODS

The viability of the cells was assessed by MTT assay and the trypan blue dye exclusion method. Morphological changes were observed by fluorescence microscopy with Hoechst 33258 staining. Cell cycle distribution, apoptosis, and mitochondrial membrane potential were measured by flow cytometry. Protein expression was detected by Western blot analysis.

RESULTS

ANTMHspd strongly decreased BEL-7402 cell proliferation in a dose- and time-dependent manner. Hoechst 33258 staining and the flow cytometry assay showed that ANTMHspd induced cell apoptosis and cell cycle perturbation. Furthermore, ANTMHspd could induce mitochondrial membrane potential loss and cytochrome c release and enhance cleaved caspase-3, cleaved caspase-9, and Bax protein expression without caspase-8 activation. ANTMHspd could also decrease the expression of Bcl-2 and cytochrome c in mitochondria. In addition, the specific inhibitors of caspase-9 and caspase-3 almost abolished the ANTMHspd-induced caspase-9 and caspase-3 activation, respectively.

CONCLUSION

ANTMHspd could induce BEL-7402 cell apoptosis via the mitochondrial/caspase-dependent pathway and the Bcl-2 family was involved in the control of apoptosis.

Redundant role for early growth response transcriptional regulators in thymocyte differentiation and survival

The early growth response (Egr) family of transcriptional regulators consists of four proteins that share highly conserved DNA-binding domains. In many cell types, they are coexpressed and appear to have cooperative roles in regulating gene expression during growth and differentiation. Three Egr proteins, Egr1, Egr2, and Egr3, are induced during thymocyte differentiation in response to pre-TCR signaling, suggesting they may be critical for some aspects of pre-TCR-mediated differentiation. Indeed, enforced expression of Egr proteins in developing thymocytes can recapitulate some aspects of pre-TCR signaling, but the mechanisms by which they contribute to beta-selection are still poorly understood. Egr3 stimulates proliferation of beta-selected thymocytes, and Egr3-deficient mice have hypocellular thymuses, defects in proliferation, and impaired progression from double-negative 3 to double-negative 4. Surprisingly, Egr1-deficient mice exhibit normal beta-selection, indicating that the functions of Egr1 during beta-selection are likely compensated by other Egr proteins. In this study, we show that mice lacking both Egr1 and Egr3 exhibit a more severe thymic atrophy and impairment of thymocyte differentiation than mice lacking either Egr1 or Egr3. This is due to a proliferation defect and cell-autonomous increase in apoptosis, indicating that Egr1 and Egr3 cooperate to promote thymocyte survival. Microarray analysis of deregulated gene expression in immature thymocytes lacking both Egr1 and Egr3 revealed a previously unknown role for Egr proteins in the maintenance of cellular metabolism, providing new insight into the function of these molecules during T cell development.

Effects of glucocorticoids on polyamine metabolism in liver and spleen of guinea pig during sensitization

Glucocorticoids are potent anti-inflammatory and immunosuppressive agents. As endogenous inhibitors of cytokine synthesis, glucocorticoids suppress immune activation and uncontrolled overproduction of cytokines, preventing tissue injury. Also, polyamine spermine is endogenous inhibitor of cytokine production (inhibiting IL-1, IL-6 and TNF synthesis). The idea of our work was to examine dexamethasone effects on the metabolism of polyamines, spermine, spermidine and putrescine and polyamine oxidase activity in liver and spleen during sensitization of guinea pigs. Sensitization was done by application of bovine serum albumin with addition of complete Freund's adjuvant. Our results indicate that polyamine amounts and polyamine oxidase activity increase during immunogenesis in liver and spleen. Dexamethasone application to sensitized and unsensitized guinea pigs causes depletion of polyamines in liver and spleen. Dexamethasone decreases polyamine oxidase activity in liver and spleen of sensitized guinea pigs, increasing at the same time PAO activity in tissues of unsensitized animals.

Polyamine deficiency leads to accumulation of reactive oxygen species in aspe2Δ mutant ofSaccharomyces cerevisiae

We have previously shown that polyamine-deficient Saccharomyces cerevisiae are very sensitive to incubation in oxygen. The current studies show that, even under more physiological conditions (i.e. growth in air), polyamine-deficient cells accumulate reactive oxygen species (ROS). These cells develop an apoptotic phenotype and, after incubation in polyamine-deficient medium, die. To show a specific effect of polyamines on ROS accumulation, uncomplicated by any effects on growth, spermine was added to spermidine-deficient spe2Delta fms1Delta cells, since spermine does not affect the growth of this strain. In this strain, spermine addition caused a marked, but not complete, decrease in the accumulation of ROS and a moderate protection against cell death. In other experiments with polyamine-deficient cells containing plasmids that overexpress superoxide dismutases (SOD1, SOD2), ROS decreased but with only a partial protection against cell death. Polyamine-deficient cells incubated anaerobically show markedly less cell death. These data show that part of the function of polyamines is protection of the cells from accumulation of ROS.

Polyamines and apoptosis

The natural polyamines putrescine, spermidine and spermine are in multiple ways involved in cell growth and the maintenance of cell viability. In the course of the last 15 years more and more evidence hinted also at roles in gene regulation. It is therefore not surprising that the polyamines are involved in events inherent to genetically programmed cell death. Following inhibition of ornithine decarboxylase, a key step in polyamine biosynthesis, numerous links have been identified between the polyamines and apoptotic pathways. Examples of activation and prevention of apoptosis due to polyamine depletion are known for several cell lines. Elevation of polyamine concentrations may lead to apoptosis or to malignant transformation. These observations are discussed in the present review, together with possible mechanisms of action of the polyamines. Contradictory results and incomplete information blur the picture and complicate interpretation. Since, however, much interest is focussed at present on all aspects of programmed cell death, a considerable progress in the elucidation of polyamine functions in apoptotic signalling pathways is expected, even though enormous difficulties oppose pinpointing specific interactions of the polyamines with pro- and anti-apoptotic factors. Such situation is quite common in polyamine research.

Polyamine depletion induces apoptosis through mitochondria-mediated pathway

Polyamines, namely putrescine, spermidine, and spermine, are essential for cell survival and proliferation. A decrease in intracellular polyamine levels is associated with apoptosis. In this study, we used inhibitors of polyamine biosynthesis to examine the effect of polyamine depletion. A combination of inhibitors of ornithine decarboxylase, S-adenosylmethionine decarboxylase, or spermidine synthase decreased intracellular polyamine levels and induced cell death in a WEHI231 murine B cell line. These cells exhibited apoptotic features including chromatin condensation and oligonucleosomal DNA fragmentation. Addition of exogenous polyamines reversed the observed features of apoptotic cell death. Similar effects were also observed in other cell lines: a human B cell line Ramos and a human T cell line Jurkat. Depletion of polyamines induced activation of caspase-3 and disruption of the mitochondrial membrane potential (Delta psi m). Inhibition of caspase activities by an inhibitor prevented the apoptotic nuclear changes but not Delta psi m disruption induced by polyamine depletion. Overexpression of Bcl-xl, an anti-apoptotic Bcl-2 family protein, completely inhibited Delta psi m disruption, caspase activation, and cell death. These results indicate that the depletion of intracellular polyamines triggers the mitochondria-mediated pathway for apoptosis, resulting in caspase activation and apoptotic cell death.

Transglutaminase activity during senescence and programmed cell death in the corolla of tobacco (Nicotiana tabacum) flowers

Corolla life span of undetached flowers of Nicotiana tabacum was divided into stages from the closed corolla (stage 1) through anthesis (stage 5) to death (stage 9). Senescence began around stage 6 in the proximal part, concomitantly with DNA laddering. Nuclear blebbing, DNA laddering, cell wall modification, decline in protein, water, pigment content and membrane integrity were observed during senescence and PCD. Transglutaminase activity was measured as mono- and bis-derivatives of putrescine (mono-PU; bis-PU) and bis-derivatives of spermidine (bis-SD). Bis-derivatives decreased with the progression of senescence, while mono-PU increased during early senescence; derivatives were present in different amounts in the proximal and distal parts of the corolla. In excised flowers, exogenous spermine delayed senescence and PCD, and caused an increase in free and acid-soluble conjugated PA levels. Bis-PU was the most abundant PA-derivative before DNA laddering stage; thereafter, bis-PU generally decreased and mono-PU became the most abundant derivative.

Rapid caspase-dependent cell death in cultured human breast cancer cells induced by the polyamine analogue N(1),N(11)-diethylnorspermine

The spermine analogue N(1),N(11)-diethylnorspermine (DENSPM) efficiently depletes the cellular pools of putrescine, spermidine and spermine by down-regulating the activity of the polyamine biosynthetic enzymes and up-regulating the activity of the catabolic enzyme spermidine/ spermine N(1)-acetyltransferase (SSAT). In the breast cancer cell line L56Br-C1, treatment with 10 microm DENSPM induced SSAT activity 60 and 240-fold at 24 and 48 h after seeding, respectively, which resulted in polyamine depletion. Cell proliferation appeared to be totally inhibited and within 48 h of treatment, there was an extensive apoptotic response. Fifty percent of the cells were found in the sub-G(1) region, as determined by flow cytometry, and the presence of apoptotic nuclei was morphologically assessed by fluorescence microscopy. Caspase-3 and caspase-9 activities were significantly elevated 24 h after seeding. At 48 h after seeding, caspase-3 and caspase-9 activities were further elevated and at this time point a significant activation of caspase-8 was also found. The DENSPM-induced cell death was dependent on the activation of the caspases as it was inhibited by the general caspase inhibitor Z-Val-Ala-Asp fluoromethyl ketone. The results are discussed in the light of the L56Br-C1 cells containing mutated BRCA1 and p53, two genes involved in DNA repair.

Utilizing chimeric proteins for exploring the cellular fate of endogenous proteins

We recently designed and constructed chimeric proteins for the elimination of specific cell populations. These chimeric proteins are composed of a targeting component fused to an apoptotic protein as the killing moiety. However, chimeric proteins can serve not only to eliminate cell populations, but also as "biological tools" for studying the fate of endogenous proteins. We show here that upon entering their target cell, a variety of chimeric proteins composed of an endogenous protein as their killing moiety reach the subcellular location of their endogenous counterpart. In contrast, bacterial-based killing domains head for the subcellular site of their substrate. Moreover, the chimeric protein acts similarly to the endogenous protein, while causing the cell to die. Therefore, chimeric proteins may serve as a unique tool for investigating cellular proteins and their intracellular localization, without the need to overexpress them.