• BMB Reports
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• 제46권2호
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• pp.92-96
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• 2013

The breast cancer susceptibility gene BRCA1 encodes a nuclear protein, which functions as a tumor suppressor and is involved in gene transcription and DNA repair processes. Many families with inherited breast and ovarian cancers have mutations in the BRCA1 gene. However, only a few studies have reported on the mechanism underlying the regulation of BRCA1 expression in humans. In this study, we investigated the transcriptional regulation of BRCA1 in HeLa cells treated with etoposide. We found that three Egr-1-binding sequences (EBSs) were located at -1031, -1005, and -385 within the enhancer region of the BRCA1 gene. Forced expression of Egr-1 stimulated the BRCA1 promoter activity. EMSA data showed that Egr-1 bound directly to the EBS within the BRCA1 gene. Knockdown of Egr-1 through the expression of a small hairpin RNA (shRNA) attenuated etoposide-induced BRCA1 promoter activity. We conclude that Egr-1 targets the BRCA1 gene in HeLa cells exposed to etoposide.

• Journal of Microbiology and Biotechnology
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• 제19권8호
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• pp.787-791
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• 2009

In the course of screening for substances that inhibit etoposide (10 ${\mu}g$/ml)-induced apoptosis in human leukemia U937 cells, fungal strain F000120, which exhibits potent inhibitory activity, was selected. The active compound was purified from an ethyl acetate extract of the microorganism by Sep-pak $C_{18}$ column chromatography and HPLC, and was identified as heptelidic acid (koningic acid) by spectroscopic methods. This compound inhibited caspase-3 induction in U937 cells with an $IC_{50}$ value of 40 ${\mu}M$ after 8 h of etoposide treatment. Fluorescent dye staining with acridine orange and ethidium bromide showed that heptelidic acid inhibited apoptosis. Furthermore, it was found that DNA fragmentation and caspase-3 activation, the biological hallmarks of apoptosis, were inhibited by the compound in a dose-dependent manner, suggesting that heptelidic acid inhibits etoposide-induced apoptosis via downregulation of caspases.

• Journal of Microbiology and Biotechnology
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• 제19권3호
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• pp.286-290
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• 2009

In the course of screening for substances inhibiting apoptosis of U937 human leukemia cells induced by etoposide ($10\;{\mu}g/ml$), Forsythiae fructus, which showed a high level of inhibition, was selected. The regulating compounds were purified from the ethyl acetate extract by silica gel column chromatography and HPLC. The active substance was purified and identified as rengyolone by spectroscopic methods. This compound showed inhibitory activity on caspase-3 induction, a major protease of the apoptosis cascade, with an $IC_{50}$ value of $38.96\;{\mu}M$ after 8 h of etoposide treatment in U937 cells. The expression level of caspase-3 and poly(ADP-ribose) polymerase (PARP) were dose-dependently inhibited by the compound, suggesting that rengyolone inhibits etoposide-induced apoptosis via downregulation of caspases.

• Journal of Microbiology and Biotechnology
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• 제15권3호
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• pp.532-536
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• 2005

In the course of our screening for small molecules to inhibit apoptosis of U937 human leukemia cells induced by etoposide ($10\;{\mu}g/ml$), Penicillium sp. F020150 with potent inhibitory activity was selected. The active compound was purified from ethyl acetate extract of the microorganism by Sephadex LH-20 column chromatography and HPLC, and was identified as gentisyl alcohol (2,5-dihydroxybenzyl alcohol) by spectroscopic methods. The compound inhibited caspase-3 induction with $IC_{50}$ value of $3.0\;{\mu}g/ml$ after 8 h of etoposide treatment. The expression levels of caspase-3 and PARP were dose-dependently inhibited by the compound, suggesting that gentisyl alcohol inhibits etoposide-induced apoptosis via downregulation of caspases.

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.571-576
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• 2019

Microenvironmental stress, which is naturally observed in solid tumors, has been implicated in anticancer drug resistance. This tumor-specific stress causes the degradation of topoisomerase $II{\alpha}$, rendering cells resistant to topoisomerase $II{\alpha}$-targeted anticancer agents. In addition, microenvironmental stress can induce the overexpression of 78kDa glucose regulated protein (GRP78), which can subsequently block the activation of apoptosis induced by treatment with anticancer agents. Therefore, inhibition of topoisomerase $II{\alpha}$ degradation and reduction in GRP78 expression may be effective strategies for inhibiting anticancer drug resistance. In this study, we investigated the active compound arctigenin, which inhibited microenvironmental stress-induced etoposide resistance in HT-29 cells. Arctigenin was also highly toxic to etoposide-resistant HT-29 cells, with an $IC_{50}$ value of $10{\mu}M$ for colony formation. We further showed that arctigenin inhibited the degradation of topoisomerase $II{\alpha}$ and reduced the expression of GRP78. Thus, these results suggest that arctigenin is a novel therapeutic agent that inhibits resistance to etoposide associated with microenvironmental stress conditions.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7719-7724
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• 2013

Background: Overexpression of survivin, a known inhibitor of apoptosis, is associated with tumor progression and drug resistance in numerous malignancies, including leukemias. The aim of this study was to investigate the effect of a specific survivin small interference RNA (siRNA) on proliferation and the sensitivity of HL-60 acute myeloid leukemia (AML) cells to the chemotherapeutic drug etoposide. Materials and Methods: The cells were transfected with siRNAs using Lipofectamine $^{TM}2000$ transfection reagent. Relative survivin mRNA and protein levels were measured by quantitative real-time PCR and Western blotting, respectively. Trypan blue exclusion assays were performed to monitor tumor cell proliferation after siRNA transfection. The cytotoxic effects of etoposide and survivin siRNA, alone and in combination, on leukemic cells were determined using MTT assay. Apoptosis was assessed by ELISA cell death assay. Results: Survivin siRNA markedly reduced both mRNA and protein expression levels in a time-dependent manner, leading to distinct inhibition of cell proliferation and increased spontaneous apoptosis. Surprisingly, survivin siRNA synergistically increased the cell toxic effects of etoposide. Moreover, survivin down-regulation significantly enhanced its induction of apoptosis. Conclusions: Our study suggests that down-regulation of survivin by siRNA can trigger apoptosis and overcome drug resistance of leukemia cells. Therefore, survivin siRNA may be an effective adjuvant in AML chemotherapy.

• Asian Pacific Journal of Cancer Prevention
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• 제15권10호
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• pp.4159-4163
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• 2014

Background: The aim of this study was to evaluate the efficacy of alternating etoposide-cisplatin and vinorelbine-cisplatin (EP-NP) compared with an etoposide-cisplatin (EP) regimen for advanced combined small cell carcinomas. Materials and Methods: Histologically confirmed combined small cell carcinoma patients who met the inclusion criteria were randomly assigned (1:1) into either the EP-NP setting (group A) or the EP setting (group B). The primary endpoint was progression-free survival in patients who received at least one dose of treatment. Results: Eighty-two patients entered into this trial, 42 in group A and 40 in group B. The objective response rates in group A and group B were 42.9% and 32.5%, respectively (p=0.334). Survival analysis showed that median progression-free survival was 6.1 months in group A, which was significantly longer than the 4.1 months in group B (p=0.041). However, as to overall survival, no significant difference was found between the two groups (11.0 vs 10.1 months in groups A and B, respectively, p=0.545). No unexpected side effects were observed in either group. Conclusions: The EP-NP regimen for combined small cell carcinomas prolonged progressio-nfree survival compared with the EP regimen. Further clinical investigations are warranted.

• Asian Pacific Journal of Cancer Prevention
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• 제13권8호
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• pp.3973-3976
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• 2012

Background: The aim of this study was to evaluate the efficacy and toxicity of long-term, low-dose oral etoposide as an advanced treatment option in patients with platinum resistant epithelial ovarian cancer. Materials and Methods: For the purposes of this study, 51 patients with histologically-confirmed, recurrent or metastatic platinum-resistant epithelial ovarian cancer (EOC) treated at six different centers between January 2006 and January 2011 were retrospectively evaluated. Patients were treated with oral etoposide (50 mg/day for a cycle of 14 days, repeated every 21 days). Results: Among the 51 platinum-resistant patients, 17.6% demonstrated a partial response and 25.5% a stable response. The median progression-free survival (PFS) was 3.9 months (95% CI, 2.1-5.7), while the median overall survival was 16.4 months (11.8.20.9). No significant relationship was observed between the pre-treatment CA 125 levels, post-treatment CA-125 levels and the treatment response rates (p=0.21). Among the 51 patients who were evaluated in terms of toxicity, grade 1 or 4 hematologic toxicity was observed in 19 (37.3%); and grade 1-4 gastrointestinal toxicity occurred in 15 patients (29.4%). Conclusions: Chronic low-dose oral etoposide treatment is generally effective and well-tolerated in platinum-resistant ovarian cancer patients.

• Applied Microscopy
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• 제38권3호
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• pp.245-250
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• 2008

전립선암은 남성 사망의 주된 원인이 되는 치명적인 질병으로 남성호르몬 의존형과 비의존형이 있다. Etoposide (Eto)는 현재 전립선암을 치료하는 데 사용하고 있으나 남성호르몬 비의존형에는 치료 성공률이 낮아서, 보다 효과적인 치료제 개발이 절실히 요구되어왔다. 본 연구는 항산화제인 vitamin C (VC)가 전립선 암세포에 어떠한 역할을 하는지 알아보고자 남성호르몬 의존형-전립선 암세포인 LNCaP와 비의존형 암세포인 DU-145에 비교적 낮은 농도의 Eto와 VC를 복합처리한 결과, Eto만을 투여한 것과 비교하여 암세포의 성장이 현저하게 억제되었고, apoptosis의 발생률 역시 유의적으로 증가하였다(p<0.05). 이러한 결과는 VC가 전립선암 치료제로 사용하고 있는 Eto의 효과를 증가시킬 수 있음을 강력히 시사하는 것이다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권2호
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• pp.629-635
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• 2014

Background: Acute myeloid leukemia (AML) is a fatal hematological malignancy which is resistant to a variety of chemotherapy drugs. Myeloid cell leukemia-1 (Mcl-1), a death-inhibiting protein that regulates apoptosis, has been shown to be overexpressed in numerous malignancies. In addition, it has been demonstrated that the expression level of the Mcl-1 gene increases at the time of leukemic relapse following chemotherapy. The aim of this study was to target Mcl-1 by small interference RNA (siRNA) and analyze its effects on survival and chemosensitivity of acute myeloid leukemia cell line HL-60. Materials and Methods: siRNA transfection was performed with a liposome approach. The expression levels of mRNA and protein were measured by real-time quantitative PCR and Western blot analysis, respectively. Trypan blue assays were performed to evaluate tumor cell growth after siRNA transfection. The cytotoxic effects of Mcl-1 siRNA (siMcl-1) and etoposide were determined using MTT assay on their own and in combination. Apoptosis was quantified using a DNA-histone ELISA assay. Results: Transfection with siMcl-1 significantly suppressed the expression of Mcl-1 mRNA and protein in a time-dependent manner, resulting in strong growth inhibition and spontaneous apoptosis. Surprisingly, pretreatment with siMcl-1 synergistically enhanced the cytotoxic effect of etoposide. Furthermore, Mcl-1 down-regulation significantly increased apoptosis sensitivity to etoposide. No significant biological effects were observed with negative control siRNA treatment. Conclusions: Our results suggest that specific suppression of Mcl-1 by siRNA can effectively induce apoptosis and overcome chemoresistance of leukemic cells. Therefore, siMcl-1 may be a potent adjuvant in leukemia chemotherapy.