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Dietary phytochemicals as adjuvants have been suggested to play important roles in enhancing chemotherapeutic potential owing to multitargeted chemopreventive properties and lack of substantial toxicity. Here, we investigated the efficacy of the combined treatment of various phytochemicals with the anticancer drug clofarabine in malignant mesothelioma MSTO-211H cells and normal mesothelial MeT-5A cells. The combined treatment of resveratrol and clofarabine produced a synergistic antiproliferative effect in MSTO-211H cells, but not in MeT-5A cells. In MSTO-211H cells, the nuclear accumulation of Sp1 and the levels of p-Akt, Sp1, c-Met, cyclin D1, and p21 were effectively decreased by the combined treatment of them. In combination with clofarabine, the ability of resveratrol to reduce the contents of Sp1 and its target gene products was also evident in a time- and dose-dependent experiment. The inhibition of phosphoinositide 3-kinase using Ly294002 augmented a decrease in the p21 level induced by their combination, but it showed no significant effects on expression of Sp1 and cyclin D1. Taken together, the data provide evidence that the synergistic antiproliferative effect of resveratrol and clofarabine is linked to the inhibition of Akt and Sp1 activities, and suggest that this combination may have therapeutic value in treatment of malignant mesothelioma.

We previously reported that MSTO-211H cells have a higher capacity to regulate Nrf2 activation in response to changes in the cellular redox environment. To further characterize its biological significance, the response of Nrf2, a transcription factor that regulates ARE-containing genes, on the synergistic cytotoxic effect of clofarabine and resveratrol was investigated in mesothelioma cells. The combination treatment showed a marked growth-inhibitory effect, which was accompanied by suppression of Nrf2 activation and decreased expression of heme oxygenase-1 (HO-1). While transient overexpression of Nrf2 conferred protection against the cytotoxicity caused by their combination, knockdown of Nrf2 expression using siRNA enhanced their cytotoxic effect. Pretreatment with Ly294002, a PI3K inhibitor, augmented the decrease in HO-1 level by their combination, whereas no obvious changes were observed in Nrf2 levels. Altogether, these results suggest that the synergistic cytotoxic effect of clofarabine and resveratrol was mediated, at least in part, through suppression of Nrf2 signaling. [BMB Reports 2012; 45(11): 647-652]

The nuclear factor erythroid-derived 2 related factor 2 (Nrf2)/heme oxygenase (HO)-1 induction plays cytoprotective roles against oxidative injury, apoptosis, and anticancer therapy; however, little is known about its regulation in human mesothelioma MSTO-211H cells. In this study, we investigated Nrf2/HO-1 induction in response to sulforaphane and determined the signaling pathways involved in this process. Sulforaphane treatment decreased cell viability and triggered a rapid and transient increase in the intracellular ROS levels. Pretreatment with N-acetylcysteine (NAC) prevented sulforaphane-induced cytotoxicity. Erk1/2 was activated within 1h of sulforaphane addition, whereas Akt phosphorylation was suppressed until the first 8h, and was then maintained at an elevated level until 72h, displaying a biphasic regulatory feature. Nrf2 protein levels in both nuclear and whole cell lysates were increased after sulforaphane treatment and were decreased by pretreatment with NAC, actinomycin D and cycloheximide. Activation of the Nrf2/HO-1 system after sulforaphane treatment was suppressed by pretreatment with NAC or Ly294002, a PI3K inhibitor. Knockdown of Nrf2 with siRNA decreased cell viability and attenuated sulforaphane-induced HO-1 up-regulation. Overall, our results indicate that ROS generation and/or activation of PI3K/Akt signaling regulate cell survival and Nrf2-driven HO-1 expression in sulforaphane-treated MSTO-211H cells.

Cadmium is a well-known toxic metal and occupational exposure to it is associated with lung cancer. In probing the possible non-genotoxic molecular targets of cadmium-induced nasal toxicity, we performed an mRNA differential display analysis for cadmium-treated human nasal septum carcinoma RPMI-2650 cells. Cadmium (≥0.5 μM) inhibited the cell proliferation. The intracellular ROS levels were induced by cadmium treatment. In addition, cadmium elicited the AKR1C3 expression. The cadmium-induced increase in AKR1C3 protein levels was suppressed by N-acetylcysteine (NAC) and, to a lesser extent, PI3K inhibitor (Ly294002). Cells pretreated with Ly294002 were more resistant to cadmium toxicity than control. The increase in AKR1C3 protein level was accompanied by an increase in the nuclear transcription factor Nrf2. Overall, our data suggest that cadmium-induced ROS cause up-regulation of AKR1C3 expression, at least partially via the activation of PI3K-related intracellular signaling pathways, and Nrf2 activation, thereby contributing to an adaptive intracellular response to cadmium toxicity.

N-Acetylcysteine (NAC), sulfidryl-containing thiol antioxidant, has been heralded as chemopreventive agent, generally because of its ability to scavenge free radicals. It also suppresses the proliferation of many cancer cells; however, the antiproliferative mechanism(s) remain to be fully elucidated. In this study, we investigated a growth-suppressive mechanism of NAC action in androgen-independent prostate carcinoma PC-3 cells. NAC (≥ 1mM) inhibited the proliferation of PC-3 cells in a dose- and time-dependent manner. Moreover, NAC treatment suppressed the activation of NF-κB induced by IKK-β as detected by the NF-κB reporter gene assay. NAC exerted a biphasic effect on the intracellular ROS levels depending on incubation time; the antioxidant effect was seen within 2h after NAC treatment, however, a pro-oxidant effect was evident after 48 h treatment. In addition to these effects, NAC treatment elicited a dose- and time-dependent increase in the Cyr61 expression that was accompanied by an increase in its mRNA and blocked by cycloheximide pretreatment. Importantly, NAC treatment caused an early but transient activation of Akt and Erk1/2. The NAC-induced increase in Cyr61 protein levels was suppressed by the PI3K inhibitor (Ly294002) and, to a lesser extent, MEK/Erk1/2 inhibitor (PD98059). Taken together, our data suggest that the antiproliferative effect of NAC is partially mediated by intracellular ROS production, the inhibition of NF-κB activity, and the activation of PI3K- and/or MEK/Erk-related intracellular signaling pathways, which lead to up-regulation of Cyr61 expression.

Malignant mesothelioma is highly resistant to apoptosis. Hence, new strategies to enhance the apoptotic signal and overcome resistance to therapeutic drugs are necessary to improve the therapeutic efficacy of malignant mesothelioma. Here, we investigated the effects of the combined treatment of various phytochemicals as a chemo-potentiator in combination with the chemotherapeutic agent clofarabine in malignant mesothelioma MSTO-211H cells and normal mesothelial Met-5A cells. Treatment with resveratrol in combination with clofarabine at a subtoxic concentration produced a synergistic antiproliferative effect and induced apoptotic cell death, as evidenced by increased subG1 peak on flow cytometric analysis, chromatin condensation and nuclear fragmentation on DAPI staining, and DNA laddering on agarose gel electrophoresis, in MSTO-211H cells, but not in Met-5A cells. In MSTO-211H cells, endogenous expression of the transcription factors Nrf2 and Sp1 proteins, several Nrf2 and Sp1-regulated gene products (HO-1, c-Met, and cyclin D1), and Akt phosphorylation, were effectively suppressed by the combined treatment of clofarabine and resveratrol. Furthermore, the nuclear accumulations of Nrf2 and Sp1 were inhibited by the combination treatment. In combination with clofarabine, the ability of resveratrol to increase the contents of the phosphorylated p53 and the apoptotic molecules, PARP and cleaved caspase 3, was also evident in a time- and dose-dependent experiment. Taken together, the data provide evidence that the synergistic antiproliferative effect of resveratrol and clofarabine is linked to simultaneous suppression of multi-target molecules, such as Nrf2, Sp1, and Akt activities, and suggest that this combination may have therapeutic value in treatment of malignant mesothelioma. Citation Format: David M. Lee, Yoon-Jin Lee, Jae-Hyuk Im, Seong-Youn Won, Hae-Seon Nam, Sang-Han Lee. Synergistic anticancer effects of resveratrol and clofarabine in malignant mesothelioma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3285. doi:10.1158/1538-7445.AM2013-3285

목적 폐경과 이와 관련된 유관변수들이 여성들의 혈중 납 농도에 어떠한 영향을 주는지를 규명하기 위하여 본 연구를 시도하였다. 연구방법 83명의 폐경 중이거나 폐경을 경험한 여성과 52명의 폐경 전 여성을 연구대상자로 선정하였다. 혈중 납량은 원자흡광광도계로 분석하였다. 난포자극호르몬(follicle-stimulating hormone, FSH)과 성선자극호르몬(lutenizing hormone, LH)을 측정하였으며, 이외에 혈색소, 혈구용적치, 체질량지수를 연구변수로 측정하였다. 또한 음주와 흡연에 관한 정보도 확보하였다. 결과 폐경기의 여성들의 혈중 납량은 평균(95% 신뢰구간)은 2.27 μg/dL (2.12-2.41 μg/dL)로서 폐경 전 여성들의 평균 1.89 μg/dL (1.76-2.02μg/dL)보다 통계적으로 유의하게 높았다. 그러나 폐경기 여성들을 다시 구분한 폐경 중과 폐경 후의 평균은 양자 간에 통계적으로 유의한 차이가 없었다. 연령, 체질량지수, 혈색소 및 흡연과 음주여부를 통제한 다중회귀분석에서 폐경 여부만이 대수 변환한 혈중 납량을 증가시키는 유일한 독립변수이었으며, FSH과 LH는 유의한 영향을 주지 못했다. 결론 본 연구결과 폐경기 한국여성들의 혈중 납량은 폐경 전 여성들보다 유의하게 높은 것이 확인되었다.