Inhibition of ATR protein kinase activity by schisandrin B in DNA damage response

ATM and ATR protein kinases play a crucial role in cellular DNA damage responses. The inhibition of ATM and ATR can lead to the abolition of the function of cell cycle checkpoints. In this regard, it is expected that checkpoint inhibitors can serve as sensitizing agents for anti-cancer chemo/radiotherapy. Although several ATM inhibitors have been reported, there are no ATR-specific inhibitors currently available. Here, we report the inhibitory effect of schisandrin B (SchB), an active ingredient of Fructus schisandrae, on ATR activity in DNA damage response. SchB treatment significantly decreased the viability of A549 adenocarcinoma cells after UV exposure. Importantly, SchB treatment inhibited both the phosphorylation levels of ATM and ATR substrates, as well as the activity of the G2/M checkpoint in UV-exposed cells. The protein kinase activity of immunoaffinity-purified ATR was dose-dependently decreased by SchB in vitro (IC(50): 7.25 muM), but the inhibitory effect was not observed in ATM, Chk1, PI3K, DNA-PK, and mTOR. The extent of UV-induced phosphorylation of p53 and Chk1 was markedly reduced by SchB in ATM-deficient but not siATR-treated cells. Taken together, our demonstration of the ability of SchB to inhibit ATR protein kinase activity following DNA damage in cells has clinical implications in anti-cancer therapy.

Protective effect of N-acetyl chitohexaose on Listeria monocytogenes infection in mice

A water-soluble oligosaccharide, N-acetyl chitohexaose (NACOS-6) was able to enhance the protecting effect of BALB/c male mice against Listeria monocytogenes infection, when administered intraperitoneally 24 hr before the challenge with this microbe. Significant decrease in number of microbes within the peritoneal cavity, spleen, and liver from the mice of NACOS-6-administered group was not observed 1 day after the infection but 4 days after the infection. Administration of NACOS-6 enhanced the delayed-type hypersensitivity response against sheep red blood cells (SRBC) or heat-killed L. monocytogenes. Splenic T lymphocytes from mice administered NACOS-6 released macrophage activating factor (MAF). These results suggested that NACOS-6 was also able to elevate the function of cellular immunity. Macrophages treated with a combination of NACOS-6 and the culture supernatant of splenic T lymphocytes from mice administered NACOS-6, "NACOS-6 sup," were found to exert a fairly strong growth-inhibitory effect on L. monocytogenes. Interferon-gamma (IFN-gamma) and interleukin 2 (IL-2) were able to enhance the growth-inhibitory effect on L. monocytogenes by the NACOS-6-treated macrophages.

Amyloid-β-Induced Cytotoxicity of PC-12 Cell Was Attenuated by Shengmai-san Through Redox Regulation and Outgrowth Induction

Neurodegenerative brain disorders such as Alzheimer's disease (AD) have been well investigated. However, significant methods for the treatment of the promotion and progression of AD are unavailable to date. Recent studies suggested that the redox imbalance and the accumulation of amyloid-beta (Abeta) peptide occurring in the brain of AD patients lead to oxidatively-induced apoptotic cell death. Here, we show the effects of Shengmai-san (SMS) on Abeta-induced cytotoxicity in PC-12 cells. SMS dose-dependently attenuated the cytotoxicity by Abeta incubation and also prevented the morphological damage in neurites of the PC-12 cells. Hemeoxygenase-1 and glutathione peroxidase-1 expressions were increased by SMS pretreatment. SMS decreased the phosphorylation level of c-jun amino-terminal kinase (JNK) and the activity of caspase-3, which were enhanced by Abeta incubation. Of importance, SMS treatment promoted neurite outgrowth. These data demonstrated dual roles of SMS in PC-12 cells. SMS prevents the apoptosis through the enhancement of anti-oxidant enzymes and inhibition of the JNK signaling pathway with the promotion of nerve cell maturation, thus suggesting benefits of SMS for the treating of neurodegenerative diseases. It may also be beneficial not only for the treatment of brain disorders but also for other diseases caused by oxidative stress.

Plasma lipoproteins as drug carriers: pharmacological activity and disposition of the complex of beta-sitosteryl-beta-D-glucopyranoside with plasma lipoproteins

The ability of plasma lipoproteins to act as carriers in site-specific drug delivery systems was evaluated by determining the disposition and pharmacological effects of beta-sitosteryl-beta-D-glucopyranoside (SG, 3). In the disposition studies, [3H]SG was absorbed from the intestinal tract by the formation of chylomicrons and was specifically associated with lipoproteins in vivo. [3H]SG was incorporated into various rat plasma lipoproteins in vitro. [3H]SG complexed with the lower density lipoproteins (d less than 1.063 g/mL), especially with the intermediate density lipoproteins (1.006 less than or equal to d less than 1.019 g/mL) which following intravenous administration to rats. In pharmacological studies, the hemostatic effect of SG in mice and the inhibitory effect of SG on vascular permeability in rats were only observed after intravenous administration of the complexes of SG with the lower density lipoproteins. The same results were obtained after the intravenous administration of the complexes of SG with human and mouse lipoproteins.

Non-thermal DNA damage of cancer cells using near-infrared irradiation

Previously, we reported that near-infrared irradiation that simulates solar near-infrared irradiation with pre- and parallel-irradiational cooling can non-thermally induce cytocidal effects in cancer cells. To explore these effects, we assessed cell viability, DNA damage response pathways, and the percentage of mitotic cancer cells after near-infrared treatment. Further, we evaluated the anti-cancer effects of near-infrared irradiation compared with doxorubicin in xenografts in nude mice by measuring tumor volume and assessing protein phosphorylation by immunoblot analysis. The cell viability of A549 lung adenocarcinoma cells was significantly decreased after three rounds of near-infrared irradiation at 20 J/cm(2). Apoptotic cells were observed in near-infrared treated cells. Moreover, near-infrared treatment increased the phosphorylation of ataxia-telangiectasia mutated (ATM) at Ser(1981), H2AX at Ser(139), Chk1 at Ser(317), structural maintenance of chromosome (SMC) 1 at Ser(966), and p53 at Ser(15) in A549 cells compared with control. Notably, near-infrared treatment induced the formation of nucleic foci of γH2AX. The percentage of mitotic A549 cells, as measured by histone H3 phosphorylation, decreased significantly after three rounds of near-infrared irradiation at 20 J/cm(2). Both near-infrared and doxorubicin inhibited the tumor growth of MDA-MB435 melanoma cell xenografts in nude mice and increased the phosphorylation of p53 at Ser(15), Chk1 at Ser(317), SMC1 at Ser(966), and H2AX at Ser(139) compared with control mice. These results indicate that near-infrared irradiation can non-thermally induce cytocidal effects in cancer cells as a result of activation of the DNA damage response pathway. The near-infrared irradiation schedule used here reduces discomfort and side effects. Therefore, this strategy may have potential application in the treatment of cancer.

Objective assessment of skin tightening in Asians using a water-filtered near-infrared (1,000-1,800 nm) device with contact-cooling and freezer-stored gel

BACKGROUND

Near-infrared has been shown to penetrate deeper than optical light sources independent of skin color, allowing safer treatment for the Asian skin type. Many studies have indicated the efficacy of various types of devices, but have not included a sufficiently objective evaluation. In this study, we used three-dimensional imaging for objective evaluation of facial skin tightening using a water-filtered near-infrared device.

METHODS

Twenty Japanese patients were treated with the water-filtered near-infrared (1,000-1,800 nm) device using a contact-cooling and nonfreezing gel stored in a freezer. Three-dimensional imaging was performed, and quantitative volume measurements were taken to evaluate the change in post-treatment volume. The patients then provided their subjective assessments.

RESULTS

Objective assessments of the treated cheek volume evaluated by a three-dimensional color schematic representation with quantitative volume measurements showed significant improvement 3 months after treatment. The mean volume reduction at the last post-treatment visit was 2.554 ± 0.999 mL. The post-treatment volume was significantly reduced compared with the pretreatment volume in all patients (P < 0.0001). Eighty-five percent of patients reported satisfaction with the improvement of skin laxity, and 80% of patients reported satisfaction with improvement of rhytids, such as the nasolabial folds. Side effects, such as epidermal burns and scar formation, were not observed throughout the study.

CONCLUSION

The advantages of this water-filtered near-infrared treatment are its high efficacy for skin tightening, associated with a minimal level of discomfort and minimal side effects. Together, these characteristics facilitate our ability to administer repeated treatments and provide alternative or adjunctive treatment for patients, with improved results. This study provides a qualitative and quantitative volumetric assessment, establishing the ability of this technology to reduce volume through noninvasive skin tightening.

Squalene Inhibits ATM-Dependent Signaling in γIR-Induced DNA Damage Response through Induction of Wip1 Phosphatase

Ataxia telangiectasia mutated (ATM) kinase plays a crucial role as a master controller in the cellular DNA damage response. Inhibition of ATM leads to inhibition of the checkpoint signaling pathway. Hence, addition of checkpoint inhibitors to anticancer therapies may be an effective targeting strategy. A recent study reported that Wip1, a protein phosphatase, de-phosphorylates serine 1981 of ATM during the DNA damage response. Squalene has been proposed to complement anticancer therapies such as chemotherapy and radiotherapy; however, there is little mechanistic information supporting this idea. Here, we report the inhibitory effect of squalene on ATM-dependent DNA damage signals. Squalene itself did not affect cell viability and the cell cycle of A549 cells, but it enhanced the cytotoxicity of gamma-irradiation (γIR). The in vitro kinase activity of ATM was not altered by squalene. However, squalene increased Wip1 expression in cells and suppressed ATM activation in γIR-treated cells. Consistent with the potential inhibition of ATM by squalene, IR-induced phosphorylation of ATM effectors such as p53 (Ser15) and Chk1 (Ser317) was inhibited by cell treatment with squalene. Thus, squalene inhibits the ATM-dependent signaling pathway following DNA damage through intracellular induction of Wip1 expression.

The Adjuvant Effect of Squalene, an Active Ingredient of Functional Foods, on Doxorubicin-Treated Allograft Mice

Many functional foods or physiologically active ingredients derived from plants and animals are actively being investigated for their role in chronic disease prevention. Squalene (SQ) is found as active ingredient in the functional foods predominantly present in olive oil and shark liver oil. It is known that during chemotherapy anticancer drugs induce inflammation. SQ has been thought to prevent and suppress inflammation; however, there is little direct evidence available. We examined the adjuvant effect of SQ on tumor-transplanted mice along with anticancer drug doxorubicin (DOX). SQ significantly suppressed the DOX-induced increase in prostaglandin E₂ (PGE₂) concentration (P < 0.05) in plasma of tumor-bearing mice. SQ inhibited the numbers of writhing response (P < 0.05), formalin-induced pain and decreased COX-2 and substance P expression in the tumor tissue compared to control mice and also enhanced the antitumor efficacy of DOX in allograft mice. Thus, SQ reduces inflammation through modulation of PGE₂ production indicating its potential as an adjuvant during chemotherapy in tumor-bearing mice.

Species differences in the disposition and metabolism of camazepam

After i.v. injection of camazepam, plasma camazepan concn. declined biexponentially. The half-life of the elimination phase (t1/2, beta) increased in the order: mice (0.73 h), rats (1.3 h), dogs (5.3 h). After oral dosing of camazepam, absorption was almost complete whereas systemic availability varied eight-fold, i.e., rats and mice (10-15%) less than dogs and monkeys (about 60%) less than humans (greater than 90%), indicating species difference in the first-pass effect. Camazepam was metabolized extensively in all species investigated to more than 10 metabolites, which were desmethyl, descarbamoyl and/or hydroxy products. In comparison with camazepam, plasma concn. of pharmacologically active metabolites, temazepam, oxazepan and hydroxy camazepam, were much higher in rats and mice than in dogs and monkeys.

Amadori-glycated phosphatidylethanolamine up-regulates telomerase activity in PANC-1 human pancreatic carcinoma cells

Several lines of experimental data have highlighted a key role of Amadori-glycated phosphatidylethanolamine (Amadori-PE) in the development of diabetic complications. Recent epidemiological studies suggest that diabetes mellitus could be a risk factor for some cancers. A characteristic of cancer cells is their immortal phenotype, and the enzyme telomerase contributes to the infinite replicative potential of cancer cells. The purpose of this study was to obtain new information about the effect of Amadori-PE on the regulation of telomerase in PANC-1 human pancreatic carcinoma cells. Amadori-PE enhanced cellular telomerase in a time- and dose-dependent manner by up-regulating hTERT expression through induction of c-myc. These results provide experimental evidence for a novel role of Amadori-PE in linking diabetes and cancer.

Differential effect of schisandrin B stereoisomers on ATR-mediated DNA damage checkpoint signaling

We have previously reported that schisandrin B (SchB) is a specific inhibitor of ATR (ataxia telangiectasia and Rad-3-related) protein kinase. Since SchB consists of a mixture of its diastereomers gomisin N (GN) and γ-schisandrin (γ-Sch), the inhibitory action of SchB might result from a stereospecific interaction between one of the stereoisomers of SchB and ATR. Therefore, we investigated the effect of GN and γ-Sch on UV (UVC at 254 nm)-induced activation of DNA damage checkpoint signaling in A549 cells. UV-induced cell death (25 - 75 J/m(2)) was amplified by the presence of the diastereomers, especially GN. At the same time, GN, but not γ-Sch, inhibited the phosphorylation of checkpoint proteins such as p53, structural maintenance of chromosomes 1, and checkpoint kinase 1 in UV-irradiated cells. Moreover, GN inhibited the G2/M checkpoint during UV-induced DNA damage. The in vitro kinase activity of immunoaffinity-purified ATR was dose-dependently inhibited by GN (IC50: 7.28 μM) but not by γ-Sch. These results indicate that GN is the active component of SchB and suggest that GN inhibits the DNA damage checkpoint signaling by stereospecifically interacting with ATR.

Metabolism and cytotoxic effects of phosphatidylcholine hydroperoxide in human hepatoma HepG2 cells

In this study, we investigated cellular uptake and metabolism of phosphatidylcholine hydroperoxide (PCOOH) in human hepatoma HepG2 cells by high performance liquid chromatography-tandem mass spectrometry, and then evaluated whether PCOOH or its metabolites cause pathophysiological effects such as cytotoxicity and apoptosis. Although we found that most PCOOH was reduced to PC hydroxide in HepG2 cells, the remaining PCOOH caused cytotoxic effects that may be mediated through an unusual apoptosis pathway. These results will enhance our fundamental understanding of how PCOOH, which is present in oxidized low density lipoproteins, is involved in the development of atherosclerosis.

Treatment of skin laxity using multisource, phase-controlled radiofrequency in Asians: visualized 3-dimensional skin tightening results and increase in elastin density shown through histologic investigation

BACKGROUND

A new multisource phase-controlled radiofrequency (MPCRF) device is widely used for skin tightening and rejuvenation in Asia.

OBJECTIVE

To evaluate the efficacy of MPCRF objectively and histologically.

METHODS

An MPCRF device with real-time impedance control was evaluated. Ten Japanese patients were treated one side of the face, and the untreated side served as a control. Three-dimensional (3-D) imaging was performed to evaluate the posttreatment volume change. An independent observer assessed the 3-D images. Histologic evaluations of elastin were performed by Victoria Blue staining in 5 Japanese patients.

RESULTS

Objective assessments evaluated by a 3-D color schematic representation showed improvement in skin laxity after the final treatment in all patients. The treated side improved markedly compared with the untreated side; however, even the untreated side slightly improved. The elastin density was significantly increased compared with controls in all 5 Japanese patients (p = .0013). Induced elastin appeared to be relatively thin elastic fibers without irregular elastic fibers, such as solar elastosis. Side effects were not observed, and the patients reported feeling comfortable throughout the study.

CONCLUSION

Multisource phase-controlled radiofrequency treatments provide stimulation of elastin and skin-tightening results safely and effectively, and thus are beneficial for improving skin laxity and rhytides.

The metabolic fate of camazepam in rats

The metabolites of camazepam in rat plasma were characterized by t.l.c., mass spectroscopy and n.m.r. spectroscopy as the mono- or di-desmethylated metabolites and the mono- or di-hydroxymethylated metabolites. The postulated metabolic pathways of camazepam involved stepwise series of desmethylations. The mono- and di-hydroxymethylated metabolites were found to be intermediates in desmethylation. Temazepam and oxazepam, metabolites of camazepam, were formed from the mono- or di-hydroxymethylated metabolites.

Non-thermal DNA damage of cancer cells using near-infrared irradiation

Previously, we reported that near-infrared irradiation that simulates solar near-infrared irradiation with pre- and parallel-irradiational cooling can non-thermally induce cytocidal effects in cancer cells. To explore these effects, we assessed cell viability, DNA damage response pathways, and the percentage of mitotic cancer cells after near-infrared treatment. Further, we evaluated the anti-cancer effects of near-infrared irradiation compared with doxorubicin in xenografts in nude mice by measuring tumor volume and assessing protein phosphorylation by immunoblot analysis. The cell viability of A549 lung adenocarcinoma cells was significantly decreased after three rounds of near-infrared irradiation at 20 J/cm(2). Apoptotic cells were observed in near-infrared treated cells. Moreover, near-infrared treatment increased the phosphorylation of ataxia-telangiectasia mutated (ATM) at Ser(1981), H2AX at Ser(139), Chk1 at Ser(317), structural maintenance of chromosome (SMC) 1 at Ser(966), and p53 at Ser(15) in A549 cells compared with control. Notably, near-infrared treatment induced the formation of nucleic foci of γH2AX. The percentage of mitotic A549 cells, as measured by histone H3 phosphorylation, decreased significantly after three rounds of near-infrared irradiation at 20 J/cm(2). Both near-infrared and doxorubicin inhibited the tumor growth of MDA-MB435 melanoma cell xenografts in nude mice and increased the phosphorylation of p53 at Ser(15), Chk1 at Ser(317), SMC1 at Ser(966), and H2AX at Ser(139) compared with control mice. These results indicate that near-infrared irradiation can non-thermally induce cytocidal effects in cancer cells as a result of activation of the DNA damage response pathway. The near-infrared irradiation schedule used here reduces discomfort and side effects. Therefore, this strategy may have potential application in the treatment of cancer.

Abstract 2971: The modulation checkpoint signaling by natural products during the DNA damage response

ATM (ataxia telangiectasia mutated) and ATR (AT and Rad3 related) protein kinases play a crucial role in cellular DNA damage responses. The inhibition of these kinases and/or related signaling molecules lead to an abolishment of one such signal pathways termed as checkpoints. It is expected that the discovery of checkpoint modulator such as natural products will be an effective assistance of anti-cancer therapy with lower side effect. In the present study, we demonstrated the inhibitory effect of Squalene (SQ), flavonoids derived from Persimmon leaves (PL) and Schisandrin-B (SchB) on ATM/ATR-dependent checkpoint signaling pathway. The cell viability was decreased by SQ, PL or SchB treated A549 adenocarcinoma after gamma-irradiation (IR) or UV exposure. In each SQ, PL and SchB treated cells, G2/M checkpoint activity was abolished in DNA damaged cells. In vitro kinase assay revealed that PL and SchB inhibits ATM and ATR, respectively. SQ, on the other hand, showed no effect on both kinases. Interestingly, SQ increased Wip1 protein expression in unperturbed cells, and suppressed ATM activation in IR treated cells. Consistent with potential inhibition of ATM by SQ or PL, IR-induced phosphorylations of ATM effectors such as p53 (S15) and Chk1 (S317) were remarkably inhibited by the treatment of SQ or PL. SchB inhibited the specific phosphorylation of these effectors by ATR. Moreover, Xenograft and allograft studies with natural products were demonstrated that the tumor growth of both cancer cells in vivo were obviously inhibited by SQ, PL or SchB treatment. These results suggest that some natural products such as SQ, PL and SchB might be applicable to the sensitization of anti-cancer therapies such as radio- /chemotherapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2971. doi:10.1158/1538-7445.AM2011-2971

Abstract 3873: Squalene enhanced chemotherapy and radiation therapy sensitivity in mice through the inhibition of DNA damage checkpoint activity

ATM (Ataxia Telangiectasia Mutated) protein kinase plays a crucial role in cellular DNA damage responses. The inhibition of ATM leads to an abolishment of one such signal pathways termed as “checkpoints”. It is expected that the discovery of checkpoint inhibitor will be an effective assistance of anti-cancer therapy. Recent study reported that Wip1, a magnesium dependent protein phosphatase, de-phosphorylates molecules involved DNA damage checkpoint response such ATM (Ser1981). On the other hand, Squalene (SQ) has been thought to assist anti-cancer therapies such as chemo and/or radiation therapy though there is few available data which refer to its detailed mechanisms. We previously showed that SQ enhances the γ-irradiation (IR) sensitivity through the induction of Wip1 in A549 adenocarcinoma cells. It was indicated that IR induced DNA damage checkpoint was abrogated by SQ pre-treatment, and led to the shrinkage of tumor in vivo. Here, we report SQ sensitizes chemotherapy and an advanced radiation therapy, heavy ion (HI) exposure, in mice using allo/xeno-graft model. Mouse Colon-26 and human MKN45 cells (5 × 106 cells/ mouse) were transplanted into Balb/c and SCID mice, respectively. The tumor volumes were estimated by measuring the growing diameters of tumor tissue every day. SQ (200μl, oral administration) was challenged after day-8 and later days. Chemotherapy using DOX (2 mg/kg, i.p.) was conducted in same days with SQ. One-time exposure of HI (Carbon, 290MeV) was performed on the day-8 in NIRS (National Institute of Radiological Sciences, Japan). Marked change of body weight was not observed between the treatments. DOX and HI prevented the tumor growth. SQ itself inhibited tumor growth slightly. The administration of SQ significantly improved the efficacy of DOX and HI on tumor growth. Wip1 protein expression in tumor tissue was detected by western blot analysis, and was elevated by the oral administration of SQ. These results were confirmed in xenograft model using MKN45 cells and SCID mice. Taken together these findings, SQ sensitized chemo/radio therapy through the inhibition of DNA damage checkpoint activity by Wip1. Further in-depth study is required to determine the clinical feasibility of SQ as a sensitizing agent for anti-cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3873.

Abstract 3875: Persimmon leaf extract inhibit gamma ray and heavy ion induced DNA damage checkpoint activity in A549 lung adenocarcinoma cells

Persimmon leaves have been commonly used as traditional medicines in Asia. They have variety kinds of health benefits in such prevention of cancer, hypertension, and inflammation. However, a few of scientific evidences are reported to date. Recent study reported that the cell cycle checkpoint system is playing a pivotal role in DNA damage response, and it is expected that the discovery of checkpoint inhibitor will be an effective assistance of anti-cancer therapy. Checkpoint signaling cascades are critically modulated by ATM (Ataxia telangiectasia-mutated) and ATR (ATM-Rad3-related) protein kinases. Generally, ATM primarily responds to ionizing radiation-induced DNA double-strand breaks, whereas ATR is activated by stalled replication resulting from UV and some genotoxic drugs. In the previous study, we demonstrated that a flavonoid-enriched persimmon leaf extract (FEPLE) promoted cytotoxic effect of cancer cells by chemotherapeutic agents inhibiting the checkpoint activity, especially in ATM dependent pathway. Here, we investigated whether FEPLE inhibits checkpoint activity during DNA damage response induced by radiation such as gamma irrradiation (γIR) and heavy ion (HI) treatment.

Dried persimmon leaves were prepared by a decoction for 30 min. A soluble extract was subsequently partitioned into ethyl acetate layer which is flavonoid-enriched persimmon leaves extract (FEPLE). FEPLE included eight flavonol components, non-galloylated flavonoids (kaempferol 3-O-glucoside, kaempferol 3-O-galactoside, quercetin 3-O-glucoside, quercetin 3-O-galactoside) and galloylated flavonoids (their 2″-gallated flavonol glucoside). γIR (2.5 to 20 Gy) and HI (2.5 to 20 Gy) were performed in National Institute of Radiological Sciences (NIRS) and Heavy Ion Medical Accelerator in Chiba (HIMAC), respectively.

Human lung adenocarcinoma A549 cells were incubated with FEPLE (0, 1, 10, 30 μg/mL) at one hour prior to γIR or HI treatment. Intracellular levels of phosphorylation in each checkpoint molecule such as p53, SMC1 and Chk1 were determined by western blot using phospho-specific antibodies of Ser15, Ser966 and Ser345, respectively. Phosphorylation on Ser10 of histone H3 was measured by flow-cytometry as a marker of cells in mitosis.

The phosphorylation of p53, SMC1 and Chk1 were increased by the treatment of γIR and HI. FEPLE reduced the phosphorylation of checkpoint proteins in both γIR and HI. Furthermore, ATM activity, estimated by the phosphorylation of Ser1981, was inhibited by the treatment of FEPLE. The pre-treatment of FEPLE significantly prevented the decrease of mitotic cells in HI exposed cells. These results indicated that DNA damage checkpoint system in γIR or HI exposed cells were abrogated by FEPLE treatment through the inhibition of ATM-dependent signaling pathway. FEPLE might be useful for clinical application by combining γIR or HI cancer therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3875.