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ABSTRACT: We examined the effects of sanguinarine, a benzophenanthridine alkaloid, on reactive oxygen species (ROS) production and the association of these effects with apoptotic cell death in a human colorectal cancer HCT-116 cell line. Sanguinarine generated ROS, which was followed by a decrease in the mitochondrial membrane potential (MMP), the activation of caspase-9 and -3, and the down-regulation of anti-apoptotic proteins, such as Bcl2, XIAP and cIAP-1. Sanguinarine also promoted the activation of caspase-8 and truncation of Bid (tBid). However, the quenching of ROS generation by N-acetyl-L-cysteine, a scavenger of ROS, reversed the sanguinarine-induced apoptosis effects via inhibition of the MMP collapse, tBid expression, and activation of caspases. Sanguinarine also markedly induced the expression of the early growth response gene-1 (Egr-1) during the early period, after which expression level was decreased. In addition, HCT-116 cells transfected with Egr-1 siRNA displayed significant blockage of sanguinarine-induced apoptotic activity in a ROS-dependent manner. These observations clearly indicate that ROS, which are key mediators of Egr-1 activation and MMP collapse, are involved in the early molecular events in the sanguinarine-induced apoptotic pathway acting in HCT-116 cells.
Toxicology Letters 05/2013; · 3.23 Impact Factor
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ABSTRACT: Taxanes are microtubule-stabilizing agents that have anticancer activity against several types of human solid tumors. Although the primary mechanism of action of these drugs is well understood, the signaling pathways that confer resistance to these agents in certain types of cancer remain poorly understood. In particular, the association of p53 with the mechanism(s) of taxane-mediated cell death is still controversial. In this study, we showed that p53 has a profound inhibitory effect on docetaxel (Doc)-induced apoptosis in prostate and colorectal cancer cells and that caspases play a critical role in this process. Doc induced prostate cancer cell apoptosis at high levels in p53-null PC3 cells, at intermediate levels in p53-mutant DU145 cells and at low levels in p53 wild-type LNCaP cells. While transient overexpression of p53 in PC3 cells suppressed Doc-induced apoptosis, knockdown of p53 in LNCaP cells increased apoptosis. This finding was further confirmed using an isogenic pair of colorectal cancer cell lines, HCT-116 p53-/- and p53+/+, indicating that p53 inhibits induction of apoptosis by Doc. To our knowledge, this is the first report describing that chemical or genetic knockout of p53 enhances the susceptibility of both prostate and colorectal cancer cells to Doc-induced apoptosis. These results may suggest an approach to stratify patients for regimens involving Doc.
International Journal of Molecular Medicine 04/2013; · 1.98 Impact Factor
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ABSTRACT: Osteosarcoma (OS) is the most common primary malignant bone cancer in children and adolescents. Although paclitaxel (PCX) has been considered one of the most important cancer chemotherapeutic drugs, the current protocols for OS treatment do not incorporate this agent. Therefore, the purpose of this study was to evaluate the induction of cell death in OS cells after exposure to PCX, to identify the cell death mechanism(s) activated by PCX and to investigate whether autophagy is associated with PCX-induced apoptosis. The results of the present study confirmed that exposure to low PCX concentrations can induce apoptotic cell death in Saos-2 cells; furthermore, caspase-3 activation, PARP degradation and XIAP downregulation were observed in combination with PCX-induced apoptosis. The potential involvement of mitochondrial events (intrinsic apoptotic pathway) in PCX-induced apoptosis in OS cells was verified by the alteration (depolarization) of mitochondrial membrane potential. In addition, pretreatment with 3-methyladenine (3-MA), a specific inhibitor of autophagy, significantly increased PCX-induced apoptotic cell death in Saos-2 cells. The augmentation of PCX-induced apoptosis by 3-MA was accompanied by increase in the cytochrome c release from the mitochondria, caspase-3 activity and XIAP downregulation, which suggests that inhibiting autophagy further stimulates the PCX-induced mitochondrion-related (intrinsic) apoptotic pathway by provoking caspase-3 activation. Thus, autophagy observed during PCX-induced apoptosis in Saos-2 OS cells represents the role of cytoprotection in cellular homeostatic processes. In conclusion, the results of this study revealed that PCX exposure effectively induces OS cell death by apoptosis associated with the mitochondrial-mediated caspase-dependent pathway. PCX can increase autophagic activity and suppressing autophagy enhances PCX-induced apoptosis in OS cells. Therefore, it is suggested that combination treatment involving low-dose PCX therapy and autophagy inhibitor therapy could be an effective and potent strategy for improved chemotherapy for OS in the near future.
International Journal of Oncology 04/2013; · 2.40 Impact Factor
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ABSTRACT: BACKGROUND: Bisphenol A (BPA) has been detected in human body fluids, such as serum and ovarian follicular fluids. Several reports indicate that BPA exposure is associated with the occurrence of several female reproductive diseases due to the disruption of steroid hormone biosynthesis in the adult ovary. OBJECTIVE: We hypothesized that long-term exposure to low concentrations of BPA disrupts 17β-estradiol (E2) production in granulosa cells via an alteration of steroidogenic proteins in ovarian cells. METHODS: Adult female rats received BPA for 90 days by daily gavage at doses of 0, 0.001, or 0.1 mg/kg body weight (BW). Serum levels of E2, testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were determined. Furthermore, the expressions of steroidogenic acute regulatory protein (StAR), P450 side-chain cleavage (P450scc), 3β-hydroxysteroid dehydrogenase isomerase (3β-HSD), and aromatase cytochrome P450 (P450arom) were analyzed in the ovary. RESULTS: Exposure to BPA significantly decreased E2 serum concentration, which was accompanied by augmented follicular atresia and luteal regression via increase of caspase-3-associated apoptosis in ovarian cells. Following BPA exposure, P450arom and StAR protein expression levels significantly decreased in granulosa and theca-interstitial (T-I) cells, respectively. However, P450scc and 3β-HSD protein levels remained unchanged. The increase in LH levels appeared to be associated with the decreased synthesis of T in T-I cells after BPA exposure via homeostatic positive feedback regulation. CONCLUSIONS: BPA exposure during adulthood can disturb the maintenance of normal ovarian functions by reducing E2. The steroidogenic proteins StAR and P450arom appear to be targeted by BPA.
Environmental Health Perspectives 03/2013; · 7.04 Impact Factor
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ABSTRACT: Decitabine (5-aza-2'-deoxycytidine), an inhibitor of DNA methyltransferases, has a wide range of anti-metabolic and anti-cancer activities. Decitabine also induces cell cycle arrest at G2/M phase and apoptosis in human cancer cells. However, the cellular and molecular mechanisms of this cell cycle arrest are poorly understood. In the present study, we investigated the roles of the tumor suppressor p53 and the cyclin-dependent kinase (Cdk) inhibitor p21 following decitabine-induced G2/M arrest in human cancer cells. DNA flow cytometric analyses indicated that decitabine induced a G2/M arrest in AGS gastric and A549 lung carcinoma cell lines, which have wild type p53. Western blot analyses using whole cell lysates from AGS cells demonstrated that decitabine treatment did not change the steady-state level of Cdks and Cdk inhibitor p27, but it partially inhibited expression of cyclin A, cyclin B1, and Cdc25C proteins. However, similar results were found using the A549 cell line, where decitabine induced a dramatic up-regulation of both p53 and p21 expression, and the increased levels of p21 were associated with increased binding of p21 with Cdks, cyclin A, and cyclin B1. Knockdown of p53 by small interfering RNA (siRNA) markedly abolished p53 induction by decitabine in AGS cells, yet p53 siRNA had no attenuating effect on p21 induction. In addition, depletion of p21 expression with siRNA, but not p53, significantly attenuated decitabine-induced G2/M arrest. We also observed that decitabine strongly induced G2/M arrest associated with p21 induction in both p53 allele-null (-/-) HCT116 and wild type p53 (+/+) HCT116 cell lines. Therefore, our data indicated that p21 plays a crucial role in decitabine-induced G2/M arrest and operates in a p53-independent manner.
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 02/2013; · 2.24 Impact Factor
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ABSTRACT: The present study investigated possible mechanisms of apoptosis induction of U937 human leukemic cells by 7,8-dihydroxyflavone hydrate (7,8-DHF), a member of the flavonoid family and a recently identified tyrosine kinase receptor B (TrkB) agonist. 7,8-DHF treatment of U937 cells resulted in inhibition of growth and induction of apoptosis as measured by MTT assay, fluorescence microscopy, DNA fragmentation, and flow cytometry analysis. 7,8-DHF-induced apoptosis in U937 cells was correlated with the up-regulation of death receptor related protein levels and down-regulation of anti-apoptotic IAP family proteins. The increase in apoptosis was also associated with proteolytic activation of caspases, Bid cleavage, insertion of pro-apoptotic Bax into the mitochondria and release of cytochrome c from mitochondria to cytosol. Furthermore, it was found that Bcl-2 overexpression markedly protected U937 cells from 7,8-DHF-induced apoptosis by restoring activation of caspases. In addition, 7,8-DHF treatment effectively activated the mitogen-activated protein kinases (MAPK), and inhibitors of extracellular-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not p38 MAPK, which significantly reduced 7,8-DHF-induced apoptosis. Taken together, our results indicate that the JNK and ERK pathways, and modulation of Bcl-2 family proteins were key regulators of apoptosis in response to 7,8-DHF in U937 cells.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 12/2012; · 2.85 Impact Factor
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ABSTRACT: Nutlin-3 is a novel small-molecule antagonist of the human homolog of mouse double minute (MDM2) that binds MDM2 in the p53-binding pocket and activates the p53 signaling pathway. In this study, we show that nutlin-3 sensitizes Caki human renal cancer cells, but not normal human skin fibroblast (HSF) cells or human mesangial cells, to TRAIL-mediated apoptosis. Combined treatment with nutlin-3 and TRAIL markedly induces apoptosis in HCT116 cells (p53 wild type), but not in HCT116 p53-/- cells, suggesting that p53 is critical for the sensitizing effect of nutlin-3 on TRAIL-induced apoptosis. Pretreatment with N-acetylcysteine (NAC) significantly inhibited nutlin-3-induced DR5 upregulation and cell death induced by the combined treatment with nutlin-3 and TRAIL, suggesting that reactive oxygen species (ROS) mediate nutlin-3-induced DR5 upregulation, which contributes toward TRAIL-mediated apoptosis. However, the upregulation of the p53-mediated protein p53 upregulated modulator of apoptosis (PUMA) by nutlin-3 is likely to be ROS independent because antioxidants failed to block PUMA upregulation. Interestingly, a combined treatment with NAC and PUMA small interfering RNAs significantly blocks nutlin-3-induced and TRAIL-induced apoptosis. Therefore, the present study shows that nutlin-3 enhances TRAIL-induced apoptosis in human renal cancer cells by ROS-mediated or p53-mediated DR5 upregulation and p53-induced PUMA upregulation. These results may offer a novel therapeutic approach to TRAIL-based cancer therapy.
Anti-cancer drugs 11/2012; · 2.23 Impact Factor
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Cheng-Yun Jin,
Cheol Park,
Su Hyun Hong,
Min Ho Han,
Jin-Woo Jeong,
Hongde Xu,
Hongmin Liu,
Gi Young Kim,
Wun-Jae Kim, Young Hyun Yoo,
Yung Hyun Choi
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ABSTRACT: Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF super-family, and it has been shown that many human cancer cell lines are refractory to TRAIL-induced cell death. However, the molecular mechanisms underlying resistance are unclear. In the present study, we show that TRAIL-resistance is reversed in human hepatoma cells by anisomycin, which is known to inhibit protein synthesis and induce ribotoxic stress. Synergistic induction of apoptosis in cells treated with anisomycin plus TRAIL was associated with activation of caspases and cleavage of Bid, a pro-apoptotic BH3-only protein. Silencing of Bid expression by small interfering RNA (siRNA) significantly attenuated the loss of mitochondrial membrane potential (MMP, Δψm) and significantly increased induction of apoptosis in cells treated with anisomycin and TRAIL, confirming that Bid cleavage is required for the response. In addition, c-Jun/AP-1 was rapidly activated upon stimulation with anisomycin; however, the knockdown of c-Jun/AP-1 expression by c-Jun siRNA markedly reduced anisomycin plus TRAIL-induced loss of MMP and apoptosis. Taken together, the findings show that anisomycin sensitizes TRAIL-mediated hepatoma cell apoptosis via the mitochondria-associated pathway, involving the cleavage of Bid and activation of the c-Jun/AP-1 pathway, indicating that this compound can be used as an anti-tumor agent in combination with TRAIL.
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 11/2012; · 2.24 Impact Factor
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Chunlan Yan,
Joon Seok Oh,
Seung Hee Yoo,
Jee Suk Lee,
Young Geol Yoon,
Yoo Jin Oh,
Min Seok Jang,
Sang Yeob Lee,
Jun Yang,
Sang Hwa Lee,
Hye Young Kim, Young Hyun Yoo
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ABSTRACT: Previous studies have reported that a Gamitrinib variant containing triphenylphosphonium (G-TPP) binds to mitochondrial Hsp90 and rapidly inhibits its activity, thus inducing the apoptotic pathway in the cells. Accordingly, G-TPP shows a potential as a promising drug for the treatment of cancer. A cell can die from different types of cell death such as apoptosis, necrosis, necroptosis, and autophagic cell death. In this study, we further investigated the mechanisms and modes of cell death in the G-TPP-treated Hep3B and U937 cell lines. We discovered that G-TPP kills the U937 cells through the apoptotic pathway and the overexpression of Bcl-2 significantly inhibits U937 cell death to G-TPP. We further discovered that G-TPP kills the Hep3B cells by activating necroptosis in combination with the partial activation of caspase-dependent apoptosis. Importantly, G-TPP overcomes the apoptosis resistance conferred by Bcl-2 in Hep3B cells via necroptosis. We also observed that G-TPP induces compensatory autophagy in the Hep3B cell line. We further found that whereas there is a Bcl-2-Beclin 1 interaction in response to G-TPP, silencing the beclin 1 gene failed to block LC3-II accumulation in the Hep3B cells, indicating that G-TPP triggers Beclin 1-independant protective autophagy in Hep3B cells. Taken together, these data reveal that G-TPP induces cell death through a combination of death pathways, including necroptosis and apoptosis, and overcomes the apoptosis resistance conferred by Bcl-2 in Hep3B cells via necroptosis. These findings are important for the therapeutic exploitation of necroptosis as an alternative cell death program to bypass the resistance to apoptosis.
Toxicology and Applied Pharmacology 11/2012; · 4.45 Impact Factor
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ABSTRACT: Fatty acid synthase (FASN) is overexpressed in a wide variety of human cancers, making it an attractive target for anticancer therapy. One of the most widely used inhibitors of FASN, cerulenin, is a natural product of Cephalosporium caerulens. Cerulenin is selectively toxic to human cancer cells in vitro. However, the mechanism by which FASN inhibition causes apoptosis in tumor cells remains unclear. Because of the widespread clinical interest in combining cerulenin with other chemotherapeutic agents, we performed this study to gain insight into the downstream effects of FASN inhibition that lead to apoptosis. Here, we observed the increased antitumor effect of cerulenin when combined with the topoisomerase inhibitor SN-38. We identified topoisomerase I as a potential mediator of cerulenin-induced apoptosis, possibly by upregulating intracellular polyunsaturation. Finally, we show that suppressing topoisomerase I catalytic activity results in synergistic effects between cerulenin and LY294002. Our results suggest that topoisomerase I could participate in cerulenin-induced apoptosis by upregulating intracellular polyunsaturation. These results will help determine the molecular basis of the cerulenin and SN-38 drug combination. Further investigation of this pathway will provide new insight into cancer cell metabolism and may aid in the design of additional cancer chemotherapeutic agents.
Apoptosis 10/2012; · 4.07 Impact Factor
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Jee Suk Lee,
Hye Young Kim,
Na Young Jeong,
Sang Yeob Lee,
Young Geol Yoon,
Yung Hyun Choi,
Chunlan Yan,
In-Sun Chu,
Hyungjong Koh,
Hwan Tae Park, Young Hyun Yoo
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ABSTRACT: Although crystallins are major structural proteins in the lens, α-crystallins perform non-lens functions, and αB-crystallin has been shown to act as an anti-apoptotic mediator in various cells. The present study was undertaken to examine whether αB-crystallin expressed in human malignant glioma cells exerts anti-apoptotic acitivity. In addition, we sought to elucidate the mechanism underlying any observed anti-apoptotic function of αB-crystallin in these cells. Three glioma cell lines, U373MG, U118MG, and T98G, were used. We observed that only the U373MG cell line expresses αB-crystallin, whereas the other 2 glioma cell lines, U118MG and T98G, demonstrated no endogenous expression of αB-crystallin. We next observed that the silencing of αB-crystallin sensitized U373MG cells to suberoylanilide hydroxamic acid (SAHA)-induced apoptosis and that αB-crystallin associates with caspase-3 and XIAP. Because XIAP is the most potent suppressor of mammalian apoptosis through the direct binding with caspases, we assessed whether XIAP also plays an anti-apoptotic role in SAHA-induced apoptosis in αB-crystallin-expressing U373MG cells. Of note, the silencing of XIAP did not alter the amount of cell death induced by SAHA, indicating that XIAP does not exert an anti-apoptotic activity in U373MG cells. We then determined whether the ectopic expression of αB-crystallin in glioma cells caused a loss of the anti-apoptotic activity of XIAP. Accordingly, we established 2 αB-crystallin over-expressing glioma cell lines, U118MG and T98G, and found that the silencing of XIAP did not sensitize these cells to SAHA-induced apoptosis. These findings suggest that αB-crystallin expressed in glioma cells overrides the anti-apoptotic activity exerted by XIAP.
Neuro-Oncology 10/2012; 14(11):1332-45. · 5.72 Impact Factor
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Seung Hun Jeong,
In Sung Song,
Hyoung Kyu Kim,
Sung Ryul Lee,
Suhee Song,
Hongsuk Suh,
Young Geol Yoon, Young Hyun Yoo,
Nari Kim,
Byoung Doo Rhee,
Kyung Soo Ko,
Jin Han
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ABSTRACT: Resveratrol is a phytoalexin and polyphenol derived from grapes, berries, and peanuts. It has been shown to mediate death of a wide variety of cancer cells. Although resveratrol is considered an important potential chemotherapeutic agent, it is required at high doses to achieve a biologically or physiologically significant effect, which may be impractical for treating cancer. Thus, a more stable and potent derivative of resveratrol, with more effective tumoricidal activity, must be developed. A novel resveratrol analog, HS-1793, has recently been synthesized and was determined to exhibit a greater decrease in cancer cell viability than resveratrol. However, the underlying mechanism of HS-1793-induced cancer cell death remains unknown. We thus investigated the mechanism by which HS-1793 induces cell death and assessed whether this occurs through a mitochondrial-mediated mechanism. Using the MCF-7 breast cancer cell line, we determined that HS-1793 treatment significantly increased cell death at a relatively low dose compared with resveratrol. HS-1793 treatment more significantly decreased mitochondrial membrane potential, cellular ATP concentration, and cellular oxygen consumption rate than resveratrol treatment. At the molecular level, HS-1793 treatment down-regulated the expression of major mitochondrial biogenesis-regulating proteins, including mitochondrial transcriptional factor A (TFAM), Tu translation elongation factor (TUFM), and single-stranded DNA-binding protein. We conclude that HS- 1793 acts by regulating the expression of TFAM and TUFM, leading to a block in normal mitochondrial function, which sensitizes cancer cells to cell death. We therefore propose that HS-1793 can be a useful chemosensitization agent, which together with other such agents can efficiently target cancer cells.
Molecules and Cells 10/2012; 34(4):357-65. · 2.18 Impact Factor
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ABSTRACT: The anticancer agent, taxol, stabilizes tubulin polymerization, resulting in arrest at the G2/M phase of the cell cycle and apoptotic cell death. However, the molecular mechanism of this growth inhibition and apoptosis is poorly understood. In this study, we used MCF-7 and MDA-MB-231 human breast carcinoma cells which have different estrogen receptor (ER) and tumor suppressor p53 statuses to examine the mechanisms of taxol-induced growth inhibition and apoptosis. Treatment of the cells with taxol resulted in a time-dependent inhibition of cell viability, which was accompanied by an accumulation of cells at G2/M and the sub-G1 apoptotic region, determined by flow cytometric analysis. Furthermore, chromatin condensation, DNA ladder formation and proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) in both cell lines were observed following treatment with taxol, indicating the occurrence of apoptotic cell death. Western blot analysis using whole cell lysates from MCF-7 and MDA-MB-231 cells treated with taxol demonstrated that taxol treatment inhibited expression of cyclin A and cyclin B1 proteins in a time-dependent manner. The inhibitory effects of taxol on cell growth and apoptosis induced by taxol were also associated with the downregulation of Wee1 kinase expression and a marked induction in the activity of the cyclin-dependent kinase inhibitor, p21WAF/CIP1. Furthermore, taxol elevated p21 promoter activity in both cell lines. These findings suggest that taxol-induced G2/M arrest and apoptosis in human breast carcinoma cells is mediated through the ER- and p53-independent upregulation of p21.
Oncology Reports 09/2012; 28(6):2163-9. · 1.84 Impact Factor
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Min Ho Jeong,
Kwang Mo Yang,
Yoo Jin Choi,
Sung Dae Kim, Young Hyun Yoo,
Su Yeong Seo,
Sang Hwa Lee,
Seong Ryul Ryu,
Chang Min Lee,
Hong Suk Suh,
Wol Soon Jo
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ABSTRACT: Natural agents with the immunomodulating property have been gaining traction to be employed in the complementary therapy of cancer because the ineffectiveness of numerous therapeutic strategies may be related in part to the tumor-induced immunosuppressive phenotypes, especially regulatory T (Treg) cells found in the tumor microenvironment. The present study was undertaken to examine whether HS-1793, synthetic resvertrol analog free from the restriction of metabolic instability and high dose requirement of resveratrol, induces an in vivo anti-tumor effect in FM3A tumor bearing mice through the suppression of Treg cells, which contribute to an increase in tumor specific cytotoxic T cell responses. Intraperitoneal injections of HS-1793 showed not only therapeutic benefits on established tumors, but also preventive anti-tumor effects. Treg cells (CD4+CD25+Foxp3+ cells) were significantly reduced in the total splenocytes as well as tumor tissues from HS-1793-administered mice, and the production of TGF-β inducing Treg showed a similar pattern. On the contrary, the administration of HS-1793 increased IFN-γ-expressing CD8+ T cells, upregulated IFN-γ production, and enhanced the cytotoxicity of splenocytes against FM3A tumor cells both in therapeutic and preventive experimental animals. These results demonstrated the suppressive role of HS-1793 on the function of Treg cells contributing to tumor specific cytotoxic T lymphocyte responses in tumor-bearing mice, which explained the underlying mechanism of the anti-tumor immunity of HS-1793.
International immunopharmacology 08/2012; 14(3):328-33. · 2.21 Impact Factor
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ABSTRACT: The Bcl-2 protein is known to exert not only anti-apoptotic but also anti-autophagic activities. Numerous studies have demonstrated that etoposide, which is one of the most widely used cancer chemotherapy agents, induces apoptotic cell death. However, the exact molecular mechanism leading to cell death by etoposide remains to be resolved. This study aimed to dissect the mode of cell death induced by etoposide in Hep3B hepatoma cells. Furthermore, this study was conducted to examine whether etoposide overcomes the resistance conferred by Bcl-2 in Hep3B hepatoma cells. We observed that Hep3B cells treated with etoposide show not only apoptotic but autophagic phenotypes. Autophagy inhibition by 3-methyladenine (3MA) and caspase inhibition by zVAD-fmk effectively decreased autophagic and apoptotic phenotypes, respectively. However, either zVAD-fmk or 3MA only partially prevented cell death. These data indicate that etoposide concomitantly induces autophagic cell death and apoptosis in Hep3B cells. Importantly, etoposide can effectively induce cell death in Bcl-2-overexpressing Hep3B cells. Conversely, staurosporine, which exclusively induces apoptosis in Hep3B cells, did not efficiently induce cell death in Bcl‑2‑overexpressing Hep3B cells. Staurosporine-treated Hep3B cells also showed an autophagic phenotype. While autophagy is cell death-inducing in Hep3B cells treated with etoposide, it is cytoprotective in Hep3B cells treated with staurosporine. To this end, we observed that etoposide-induced mixed type of programmed cell death is associated with the dissociation of Bcl-2 from Beclin-1. Taken together, etoposide induces a mixed type of programmed cell death and overcomes the resistance conferred by Bcl-2 in Hep3B hepatoma cells.
International Journal of Oncology 08/2012; · 2.40 Impact Factor
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ABSTRACT: Selenium in the form of sodium selenite has been reported to exert anti-tumor effects in several cancer cell types by inducing autophagic cell death and apoptosis mediated by reactive oxygen species (ROS). However, the exact molecular pathways underlying these effects have not been fully established. The present study used A549 human lung carcinoma cells for further investigation of the anti-cancer mechanism of sodium selenite. We showed that sodium selenite modulated both the extrinsic and intrinsic apoptotic pathways, which were interconnected by Bid truncation. We used z-VAD-fmk, a pan-caspase inhibitor, to demonstrate that sodium selenite-induced apoptosis was dependent on the activation of caspases. Sodium selenite also increased autophagy, as indicated by an increase in microtubule-associated protein light chain-3 (LC3) puncta, accumulation of LC3II, and elevation of autophagic flux. Pretreatment with bafilomycin A1 enhanced sodium selenite-induced apoptosis, indicating that sodium selenite-induced autophagy functioned as a survival mechanism. Sodium selenite treatment also resulted in generation of ROS, which abrogated mitochondrial membrane potential (MMP) and regulated both apoptosis and autophagy. Phospho-nuclear factor erythroid 2-related factor 2 (p-Nrf2) showed a ROS-dependent translocation to the nucleus, which suggested that Nrf2 might increase cell survival by suppressing ROS accumulation and apoptosis mediated by oxidative stress. Sodium selenite treatment of A549 cells therefore appeared to trigger both apoptosis and cytoprotective autophagy, which were both mediated by ROS. The data suggest that regulation of ROS generation and autophagy can be a potential strategy for treating lung cancer that is resistant to pro-apoptotic therapeutics.
Toxicology Letters 06/2012; 212(3):252-61. · 3.23 Impact Factor
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ABSTRACT: We investigated the mechanisms of the anti-proliferative action of 7,8-dihydroxyflavone (7,8-DHF), a member of the flavonoid family, in U937 human monocytic leukemia cells. We found that 7,8-DHF time-dependently inhibited the growth of U937 cells, arresting them in the G1 phase of their cell cycle and inducing apoptosis. 7,8-DHF-induced G1 arrest was correlated with downregulation of cyclin E, with a concomitant upregulation of cyclin-dependent kinase (Cdk) inhibitors including p27, and association of p27 with Cdk2 was markedly induced in 7,8-DHF-treated cells. We also observed that downregulation of the phosphorylation of retinoblastoma protein (pRB) by this flavonoid was associated with enhanced binding of pRB and the transcription factor E2F-1. Overall, our results demonstrate a combined mechanism for the anticancer effects of 7,8-DHF that involves the inhibition of pRB phosphorylation and induction of p27 as targets for 7,8-DHF.
Oncology Reports 04/2012; 28(1):353-7. · 1.84 Impact Factor
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ABSTRACT: 7,12-Dimethylbenzanthracene (DMBA), a polycyclic aromatic hydrocarbon, exhibits mutagenic, carcinogenic, immunosuppressive, and apoptogenic properties in various cell types. To achieve these functions effectively, DMBA is modified to its active form by cytochrome P450 1 (CYP1). Exposure to DMBA causes cytotoxicitymediated apoptosis in bone marrow B cells and ovarian cells. Although uterine endometrium constitutively expresses CYP1A1 and CYP1B1, their apoptotic role after exposure to DMBA remains to be elucidated. Therefore, we chose RL95-2 endometrial cancer cells as a model system for studying DMBA-induced cytotoxicity and cell death and hypothesized that exposure to DMBA causes apoptosis in this cell type following CYP1A1 and/or CYP1B1 activation. We showed that DMBA-induced apoptosis in RL95-2 cells is associated with activation of caspases. In addition, mitochondrial changes, including decrease in mitochondrial potential and release of mitochondrial cytochrome c into the cytosol, support the hypothesis that a mitochondrial pathway is involved in DMBA-induced apoptosis. Exposure to DMBA upregulated the expression of AhR, Arnt, CYP1A1, and CYP1B1 significantly; this may be necessary for the conversion of DMBA to DMBA-3,4-diol-1,2-epoxide (DMBA-DE). Although both CYP1A1 and CYP1B1 were significantly upregulated by DMBA, only CYP1B1 exhibited activity. Moreover, knockdown of CYP1B1 abolished DMBA-induced apoptosis in RL95-2 cells. Our data show that RL95-2 cells are susceptible to apoptosis by exposure to DMBA and that CYP1B1 plays a pivotal role in DMBA-induced apoptosis in this system.
Toxicology and Applied Pharmacology 04/2012; 260(2):124-34. · 4.45 Impact Factor
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ABSTRACT: Recent advances in the understanding of the mechanisms responsible for tumor progression suggest the possibility to control cancer growth, not only through chemotherapy-induced cancer cell destruction, but also by stimulating anticancer immunity. However, immune tolerance against tumor antigens disturbs diverse forms of immunotherapy. One of the most potent and well-studied tumor-induced immunosuppressive phenotypes found in the tumor microenvironment is the regulatory subpopulation cells (CD4(+)CD25(+)FoxP3(+) Treg cells). Among the great number of natural agents derived from plants and potentially useful for application in the complementary therapy of cancer, resveratrol is gaining attention for its immunomodulating properties in breast cancer, since the ineffectiveness of numerous immunotherapy strategies may be related, in part, to their negative effects on Treg cells. The present study was undertaken to examine whether HS-1793, a synthetic resveratrol analogue free from the restriction of the metabolic instability and high dose requirement of resveratrol, shows a direct effect on immune responses by enhancing lymphocyte proliferation or an immunomodulatory effect by inducing changes in the Treg cell population in FM3A breast tumor-bearing mice. Although HS-1793 had no direct immunostimulatory effect, it dose-dependently decreased IL-2 secretion and increased IL-4 secretion of concanavalin A-stimulated lymphocytes from tumor-bearing mice, which suggest that HS-1793 may induce changes in the subpopulations of tumor-derived T lymphocytes. The CD4(+)CD25(+) cell population from tumor-bearing mice decreased after HS-1793 treatment in a dose-dependent manner, while the CD4(+) T cell population remained unchanged. FoxP3(+)-expressing cells among the CD4(+)CD25(+) population showed a similar pattern. In contrast, the CD8(+) T cell population as well as the interferon (IFN)-γ-expressing CD8(+) T cell population and IFN-γ secretion of splenocytes from tumor-bearing mice were significantly upregulated by HS-1793 treatment. These results suggest that HS-1793 induces the modulation of tumor-derived T lymphocytes, particulary having a suppressive effect on the Treg cell population, likely contributing to enhanced tumor-specific cytotoxic T lymphocyte responses and CD4(+) T cells involving antitumor immunity. Therefore, HS-1793 may serve as a promising adjuvant therapeutic reagent in breast cancer immunotherapy.
Experimental and therapeutic medicine 04/2012; 3(4):592-598.
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ABSTRACT: We recently reported that cilostazol protects chondrocytes against stress-induced apoptosis and prevents cartilage destruction in an osteoarthritis (OA) model. In the present study, we elucidate the mechanism underlying the protective effect induced by cilostazol against stress-induced apoptosis in chondrocytes. Cilostazol significantly reduced the expression of type II collagen and stimulated the accumulation of β-catenin in primary rat articular chondrocytes. Moreover, cilostazol-induced chondrocytes showed induction of senescent phenotypes, such as changes in cell morphology, decrease in cell proliferation and increase in specific senescence-associated β-galactosidase (SA-β-gal) staining. Moreover, dedifferentiated chondrocytes obtained by serial subculture showed cellular senescence that increased with passage number. In addition, the percentage of terminal dUTP nick end-labeling (TUNEL)-positive cells was higher when chondrocytes were treated with cilostazol and the apoptosis inducer etoposide than when the cells were treated with etoposide alone. Our findings suggest that cilostazol induces dedifferentiation and senescence in rat articular chondrocytes and renders them resistant to etoposide-induced apoptosis.
International Journal of Molecular Medicine 04/2012; 29(4):619-24. · 1.98 Impact Factor
