Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells

Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of th...

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Опубліковано в: :Experimental Oncology
Дата:2007
Автори: Pan, Y.Y., Xu, S.P., Jia, X.Y., Xu, H.Q., Zhang, Y., Rui, L.X., Wei, W.
Формат: Стаття
Мова:English
Опубліковано: Інститут експериментальної патології, онкології і радіобіології ім. Р.Є. Кавецького НАН України 2007
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Цитувати:Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells / Y.Y. Pan, S.P. Xu, X.Y. Jia, H.Q. Xu, Y. Zhang, L.X. Rui, W. Wei // Experimental Oncology. — 2007. — Т. 29, № 1. — С. 23-29. — Бібліогр.: 45 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-138556
record_format dspace
spelling Pan, Y.Y.
Xu, S.P.
Jia, X.Y.
Xu, H.Q.
Zhang, Y.
Rui, L.X.
Wei, W.
2018-06-19T09:28:43Z
2018-06-19T09:28:43Z
2007
Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells / Y.Y. Pan, S.P. Xu, X.Y. Jia, H.Q. Xu, Y. Zhang, L.X. Rui, W. Wei // Experimental Oncology. — 2007. — Т. 29, № 1. — С. 23-29. — Бібліогр.: 45 назв. — англ.
1812-9269
https://nasplib.isofts.kiev.ua/handle/123456789/138556
Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells. Methods: We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma. Results: Our results showed that the treatment of HepG2 cells with more than 50 µM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE2 production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 µM or 100 µM of nimesulide and low concentrations (5 µM to 20 µM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production. Conclusion: These data suggest synergistic and/or additive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma.
Угнетение циклооксигеназы-2 (ЦОГ-2) оказывает терапевтический эффект при лечении больных с солидными опухолями и сопровождается снижением пролиферации опухолевых клеток и индукцией апоптоза. Цель: изучение роли ингибитора ЦОГ-2 — нимесулида в процессах роста и апоптоза культивированных клеток гепатокарциномы человека HepG2. Методы: для оценки апоптоза и угнетения роста клеток при применении нимесулида самостоятельно и в сочетании с доксорубицином применяли MTT-анализ, проточную цитометрию и стандартные морфологические методы. Результаты: установлено, что обработка клеток HepG2 cells нимесулидом в концентрации > 50 μM приводила к угнетению активности ЦОГ-2 за счет снижения продукции PGE2 , после чего отмечали подавление роста и апоптоз клеток при неизмененном уровне экспрессии ЦОГ-2. Комбинированное применение 50 μM или 100 μM нимесулида и доксорубицина в концентрации 5–20 μM обусловило усиленное угнетение роста клеток, индукции апоптоза и снижение продукции VEGF. Выводы: полученные данные свидетельствуют о синергическом и/или аддитивном эффекте при применении ингибиторов ЦОГ-2 и химиотерапевтических препаратов.
We thank Hong-Mei Xu for excellent technical assistance.
en
Інститут експериментальної патології, онкології і радіобіології ім. Р.Є. Кавецького НАН України
Experimental Oncology
Original contributions
Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
Комбинированное применение ингибитора циклооксигеназы-2 и доксорубицина приводит к угнетению роста и апоптозу клеток гепатокарциномы человека
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
spellingShingle Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
Pan, Y.Y.
Xu, S.P.
Jia, X.Y.
Xu, H.Q.
Zhang, Y.
Rui, L.X.
Wei, W.
Original contributions
title_short Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
title_full Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
title_fullStr Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
title_full_unstemmed Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
title_sort combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells
author Pan, Y.Y.
Xu, S.P.
Jia, X.Y.
Xu, H.Q.
Zhang, Y.
Rui, L.X.
Wei, W.
author_facet Pan, Y.Y.
Xu, S.P.
Jia, X.Y.
Xu, H.Q.
Zhang, Y.
Rui, L.X.
Wei, W.
topic Original contributions
topic_facet Original contributions
publishDate 2007
language English
container_title Experimental Oncology
publisher Інститут експериментальної патології, онкології і радіобіології ім. Р.Є. Кавецького НАН України
format Article
title_alt Комбинированное применение ингибитора циклооксигеназы-2 и доксорубицина приводит к угнетению роста и апоптозу клеток гепатокарциномы человека
description Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells. Methods: We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma. Results: Our results showed that the treatment of HepG2 cells with more than 50 µM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE2 production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 µM or 100 µM of nimesulide and low concentrations (5 µM to 20 µM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production. Conclusion: These data suggest synergistic and/or additive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma. Угнетение циклооксигеназы-2 (ЦОГ-2) оказывает терапевтический эффект при лечении больных с солидными опухолями и сопровождается снижением пролиферации опухолевых клеток и индукцией апоптоза. Цель: изучение роли ингибитора ЦОГ-2 — нимесулида в процессах роста и апоптоза культивированных клеток гепатокарциномы человека HepG2. Методы: для оценки апоптоза и угнетения роста клеток при применении нимесулида самостоятельно и в сочетании с доксорубицином применяли MTT-анализ, проточную цитометрию и стандартные морфологические методы. Результаты: установлено, что обработка клеток HepG2 cells нимесулидом в концентрации > 50 μM приводила к угнетению активности ЦОГ-2 за счет снижения продукции PGE2 , после чего отмечали подавление роста и апоптоз клеток при неизмененном уровне экспрессии ЦОГ-2. Комбинированное применение 50 μM или 100 μM нимесулида и доксорубицина в концентрации 5–20 μM обусловило усиленное угнетение роста клеток, индукции апоптоза и снижение продукции VEGF. Выводы: полученные данные свидетельствуют о синергическом и/или аддитивном эффекте при применении ингибиторов ЦОГ-2 и химиотерапевтических препаратов.
issn 1812-9269
url https://nasplib.isofts.kiev.ua/handle/123456789/138556
citation_txt Combination of cyclooxygenase-2 inhibitor and doxorubicin increases the growth inhibition and apoptosis in human hepatocellular carcinoma cells / Y.Y. Pan, S.P. Xu, X.Y. Jia, H.Q. Xu, Y. Zhang, L.X. Rui, W. Wei // Experimental Oncology. — 2007. — Т. 29, № 1. — С. 23-29. — Бібліогр.: 45 назв. — англ.
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fulltext Experimental Oncology ���� ������� ����� ��arc��� ������ ������� ����� ��arc��� ���arc��� ���� �� �� Hepatocellular carcinoma �HCC�� is t�e fift� most common cancer and t�e fourt� leading cause of cancer related mortality worldwide�� wit� t�e �ig�est incidence in Asia�� w�ere �epatitis B or C is epidemic [1]. Alt�oug� t�e clinical diagnosis and management of early-stage HCC �as significantly improved�� HCC prognosis remains poor. Only 1����% of patients qualify for curative surgery [�]. T�e median survival of patients w�o �ave unresectable tumors is only 4 mont�s [�]. Currently�� no effective systemic �c�e- mot�erapeutic or c�emopreventive�� treatments are available. Hence�� investigating HCC pat�ogenesis and finding new treatment strategies is an urgent need. T�e cyclooxygenase-� �COX-��� is �ig�ly expressed in a variety of �uman cancers [4�� 5]. COX-� �as been associated wit� tumor growt��� angiogenesis�� invasion�� and metastasis [6�� ��]. Overexpression of COX-� may increase t�e resistance of cancer cells to apoptosis [8]. T�us�� t�e reduction of t�e COX-� enzyme activity or protein expression may in�ibit cell growt� in cancer cells. Non-steroidal anti-inflammatory drugs �NSAIDs�� �ave been s�own to in�ibit COX enzymes and may be employed for t�e c�emoprevention of cancer [��� 1�]. Some NSAIDs suc� as nimesulide ex�ibit �ig� selectiv- ity for COX-� enzyme�� but �ave little effects on COX-1 enzyme [11]. T�e expression pattern of COX-� protein in HCC is well correlated wit� t�e differentiation grade�� suggesting t�at abnormal COX-� expression plays an important role in �epatocarcinogenesis [1��� 1�]. In�ibi- tion of COX-� by several in�ibitors including celecoxib�� NS-��8 and nimesulide induces growt� in�ibition and marked apoptosis in cultured HCC cells by various mec�anisms [1��� 14���]. T�ere is also evidence suggesting an important role of angiogenesis in COX-�-mediated �epatocar- cinogenesis. COX-� �as been s�own to induce angio- genesis via vascular endot�elial growt� factor �VEGF���� a well-studied regulator of pat�ological angiogenesis [�1���]. Several recent studies s�ow t�at elevated COX-� expression correlates wit� increased VEGF level and microvascular density in �uman HCCs [16�� �4�� �5]. In cultured �epatocellular carcinoma cells�� VEGF production is increased by overexpression of COX-� or by treatment wit� prostaglandin E� �PGE����� and t�is effect is blocked by in�ibition of COX-� [16]. A separate study also s�ows a role for PGE� in t�e up-regulation of VEGF in t�e �epatocellular carcinoma cells [16]. T�ese findings suggest t�at COX-� and COX-�-derived PGE� signaling may promote �epatocarcinogenesis in part t�roug� VEGF-induced angiogenesis. In t�is regard�� targeting COX-�-derived prostaglandin sig- naling represents a promising strategy to reduce t�e tumor burden. Doxorubicin is one of t�e effective agents for t�e treatment of patients wit� unresectable HCCs [�6�� ���]. Single use of doxorubicin yields response rate of up to ��%�� �owever median survival is not prolonged. T�ere is no convincing evidence from randomized trails t�at t�e combination c�emot�erapy prolongs t�e survival of patients wit� unresectable HCC better t�an single agents. W�et�er COX-� in�ibitors are beneficial in t�e treatment of HCC if given in combination wit� t�ese COMBINATION OF CYCLOOXYGENASE-2 INHIBITOR AND DOXORUBICIN INCREASES THE GROWTH INHIBITION AND APOPTOSIS IN HUMAN HEPATOCELLULAR CARCINOMA CELLS Y.Y. Pan1, *, S.P. Xu1, X.Y. Jia1, H.Q. Xu1, Y. Zhang, L.X. Rui2, W. Wei1 1Institute of Clinical Pharmacology of Anhui Medical University, Key Laboratory of Antiinflammatory and Immunological Pharmacology in Anhui Province, Anhui Medical University, China 2Metabolism Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA Inhibition of cyclooxygenase (COX)-2 elicits therapeutic effects in solid tumors that are coupled with the inhibition of cell proliferation and induction of apoptosis in tumor cells. Aim: This study was designed to investigate the role of COX-2 inhibitor nimesulide in cell growth and apoptosis of the cultured human hepatocellular carcinoma HepG2 cells. Methods: We performed the MTT assay, flow cytometric analysis and cell morphology study to evaluate growth inhibition and cell apoptosis upon the action of nimesulide alone or along with doxorubicin, a common agent for the treatment of human hepatocellular carcinoma. Results: Our results showed that the treatment of HepG2 cells with more than 50 μM of nimesulide suppressed COX-2 enzyme activity because of reduced PGE2 production, and then induced growth inhibition and cell apoptosis despite no alterations of COX-2 protein expression. Importantly, the combination of 50 μM or 100 μM of nimesulide and low concentrations (5 μM to 20 μM) of doxorubicin resulted in enhanced cell growth inhibition, apoptosis induction and reduced VEGF production. Conclusion: These data suggest synergistic and/or addi- tive effects of COX-2 inhibitors and chemotherapeutic agents, and may provide the rational for clinical studies of COX-2 inhibitors on the treatment or chemoprevention of human hepatocellular carcinoma. Key Words: hepatocellular carcinoma, nimesulide, COX-2, doxorubicin, apoptosis, VEGF. Received: January 31, 2007. *Correspondence: Fax: +86 551 2922826, E-mail: yueyinpan@gmail.com Abbreviation used: COX-2 – cyclooxygenase-2; ELISA — enzyme- linked immunosorbent assay; HCC – hepatocellular carcinoma; MTT — 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide; PGE2 – prostaglandin E2; PI – propidium iodide; VEGF – vascular endothelial growth factor. Exp Oncol ����� ���� 1�� ����� �4 Experimental Oncology ���� ������� ����� ��arc��� effective agents suc� as doxorubicin wit� comple- mentary mec�anisms remains unknown. In t�is study�� we �ave c�aracterized t�e effects of COX-� in�ibition on cell growt� and survival by treat- ment wit� nimesulide�� a COX-� specific in�ibitor�� in �epatocellular carcinoma cell line HepG�. Our results s�owed t�at t�e treatment wit� nimesulide en�anced doxorubicin-mediated cytotoxicity and reduced pro- duction of PGE� and VEGF. Our results t�at s�ow addi- tive in�ibitory effects of COX-� in�ibitor nimesulide and doxorubicin on t�e growt� of �epatocellular carcinoma cells may provide t�e rationale for clinical studies of COX-� in�ibitors on t�e treatment or c�emopreven- tion of HCC. MATERIALS AND METHODS Reagents. Human HepG� �epatocellular carci- noma cell line was obtained from T�e Researc� Insti- tute on Hepatoma of S�ang�ai. R�PI 164��� D�E� and �E� culture medium was purc�ased from Gibco BRL. Fetal bovine serum �FBS�� was provided by Sijiqing Biological Engineering �aterial �Hangz�ou�� C�ina��. Rabbit anti-COX-� was from Cayman. S�eep anti- rabbit�� s�eep anti-mouse secondary antibodies were purc�ased from Santa Cruz Biotec�nology�� Inc. �Santa Cruz�� CA��. �-�4�� 5-Dimet�ylt�iazol-�-yl��-��� 5-dip�en- yltetrazolium bromide ��TT���� nimesulide and acridine orange �AO�� were purc�ased from Sigma C�emical Co. �St. Louis�� �O��. Doxorubicin was provided by Wanle Co. �S�enz�en�� C�ina��. Cell culture. HepG� cells were maintained in D�E� medium supplemented wit� 1�% fetal bovine serum �FBS���� 1�� units/ml penicillin�� and 1�� mg/ml streptomycin. HepG� cells were cultured at 5% CO� and ���° C in a �umidified incubator �Nacpo-61���� DuPont Company�� USA��. MTT assay. T�e number of viable cells was deter- mined by �TT assay. Eac� cell sample was plated at a density of 1�4 cells/well in �6-well cluster dis�es for �4 � before treatment. T�en t�e medium was c�anged and nimesulide and doxorubicin were added in various concentrations and analyzed at indicated time points. After addition of �TT solution �5 g/L�� in eac� well�� t�e cells were incubated at ���° for 4 ��� and t�en 15� µL D�SO was added to dissolve t�e dark blue crystals. T�e absorbance was measured in an ELISA plate reader �EL��1 Strip reader�� BIOTEK�� USA�� wit� a test wavelengt� of 5��� nm�� and t�e relative percentage of survival was calculated by dividing t�e absorbance of treated cells by t�at of t�e control in eac� experiment. Percent cytotoxicity was calculated using t�e formula: percent cytotoxicity = [1-�absorbance of experimental wells/absorbance of control wells��] × 1��%. Cell morphology. After treatement wit� drugs�� cytological morp�ology c�anges were observed under t�e Olympus optical microscope. Cells were subcul- tured on coverslips in 6-well culture plates. After �4 ��� t�e coverslips were taken out and stained wit� acridine orange. Cells were observed and p�otograp�s were taken under fluorescence microscope. Flow cytometry. HepG� cells were seeded in cul- ture flasks. T�e culture bottles were divided into one medium alone and t�ree drug-treated groups. Eac� group was in triplicate. W�en t�e cells were anc�ored to t�e plates�� various drugs were added and t�e cells incubated at ���°�� 5% CO� for 48 �. T�en eac� group of cells were was�ed wit� PBS�� trypsinized and t�en stained wit� propidium iodide �PI�� Sigma�� USA��. T�e red fluorescence of DNA-bound PI in eac� group was measured at 488 nm by FACScan flow cytometry �EPTCS XLL��CL Beckman Coulter�� UK��. Western blot analysis. For immunoblot analysis of COX-��� HepG� cells were lysed in a buffer consisting of 5� m� Tris-HCl�� pH ��.4�� 1% Tween ���� � m� EDTA�� 1 m� p�enylmet�ylsulfonyl fluoride�� 1� µg/mL aprotinin�� and 1� µg/mL leupeptin. Debris was removed by centrifu- gation �Beckman GPKR mac�ine�� at ������ g for �� min at 4 °C. A total of 6� µg of precipitated and denatured protein was separated by 1�% sodium dodecyl sulfate- polyacrylamide gel electrop�oresis �SDS-PAGE�� and transferred electrop�oretically to polyvinylidene fuoride membranes �Immun-Blot PVDF membrane�� �.� µm; Bio-Rad��. �embranes were blocked wit� 5% nonfat milk powder in �.5 % Tween ��-PBS for � �. Primary antibod- ies to COX-� were used at a final dilution of 1 : 1��� for overnig�t�� at 4 °C. T�e blot was was�ed several times wit� �.�5% Tween ��-PBS and incubated wit� t�e appropri- ate goat anti-rabbit antibody for � �. Immunodetection was carried out using en�anced c�emiluminescence reagent following t�e manufacturer’s instructions �Pierce Biotec�nology Inc�� USA��. Measurement of prostaglandin E2 and VEGF production. HepG� carcinoma cells were plated at a density of 5 × 1�5 cells / p6� Petri dis� in complete D�E� medium for 1� �. HepG� cells were treated wit� �5� 1�� µ� nimesulide for �4 �. After drug treatment�� cul- ture supernatant was collected and centrifuged briefly. T�e amount of PGE� in t�e medium was measured using a commercial RIA kit �Wu�an Boster Co�� Wu�an�� C�ina�� and VEGF level determined wit� an enzyme-linked im- munosorbent assay �ELISA�� kit �Promega Corporation�� following t�e manufacturer’s instructions. Statistical analysis. Data from t�e popula- tion of cells treated wit� different conditions were analyzed using paired Student’s t-test or ANOVA test �a comparison of multiple groups���� and p value of < �.�5 was considered statistically significant in t�e experiments. RESULTS Nimesulide inhibits the COX-2 activity in HepG2 hepatocellular carcinoma cells. First�� we performed t�e Western blot analysis to examine w�et�er COX-� protein is expressed in HepG�cells. As s�own in Fig. 1�� a�� COX-� protein was �ig�ly expressed in HepG� cells. T�is is consistent to a recent immuno�itoc�emistry study t�at s�ows �ig� COX-� protein expression in HepG� and Hu��� cells [�8]. As treatment wit� �5�1�� µ� nimesulide for �4 � did not significantly alter expression levels of COX-� protein in HepG� cells �Fig. 1�� a���� next Experimental Oncology ���� ������� ����� ��arc��� �5���� ������� ����� ��arc��� �5�arc��� �5�� �5 �5 we tested w�et�er treatment wit� nimesulide in�ibits t�e COX-� enzyme activity by measuring PGE� levels of culture supernatant. T�e average amount of PGE� in t�e medium alone controls from t�ree independent ex- periments was �.65 ng/ml. Compared wit� t�e control�� t�e PGE� production was reduced by about 8�%�� 65% and 4�% �4 � after t�e treatment wit� �5 µ��� 5� µ� or 1�� µ� of nimesulide�� respectively �Fig. 1�� b���� indicating t�e dose-dependent in�ibition. Fig.1. Effects of nimesulide on t�e COX-� protein expression and PGE� production in �uman HepG� cells. �a�� HepG� cells were treated wit� �5�1�� µ� nimesulide for �4 � as indicated. T�e total protein extracts were subjected to Western blot analysis using anti-COX-� antibody. Anti-ERK-� antibody was used as a loading control. �b�� T�e HepG� cells were treated wit� �5�1�� µ� nimesulide. After incubation for �4 ��� t�e PGE� level in t�e culture medium was measured by a PGE� EIA kit following t�e manufacturer’s protocol. T�e means ± S.E of t�ree independent experiments in eac� treatment are s�own Nimesulide inhibits cell growth and enhances doxorubicin-mediated apoptosis of cultured HepG2 cells. To determine w�et�er COX-� in�ibi- tion by nimesulide contributes to growt� in�ibition of HepG� cells we measured t�e number of apoptotic cells after treatment wit� various doses of nimesulide by �TT assay. As s�own in t�e left panel of Fig. ��� a�� t�e number of viable cells started to decline by treat- ment wit� a low concentration of nimesulide ��5 µ��� and continued to drop by up to 4�% at 4�� µ� of nimesulide. As expected�� cell apoptosis induced by doxorubicin is more evident t�an t�at by nimesulide as treatment wit� 8� µ� of doxorubicin induced deat� of almost all cells in t�e culture �Fig. ��� a�� rig�t panel��. T�e apoptosis triggered by nimesulide or doxorubicin was s�own in a concentration-dependent manner. Because nimesulide-induced cell deat� is t�roug� COX-� in�ibition and doxorubicin acts as cell cycle in�ibitor on triggering cell apoptosis�� we �ypot�esize t�at t�e in�ibition of COX-� by nimesulide may en- �ance t�e doxorubicin-mediated cytotoxity. To test t�is possibility�� we performed t�e �TT assay by co-treat- ment of HepG� cells wit� doxorubicin and nimesulide. As s�own in Fig. ��� b�� compared to cell treated wit� 5 µ� of doxorubicin alone�� addition of �5�� 5� or 1�� µ� nimesulide yielded a � to �.5 fold increase in cell deat��� respectively. T�is synergistic effect of nimesulide persisted even at �ig�er concentrations of doxorubi- cin�� 1� µ� or �� µ�. Since treatment wit� more t�an 4� µ� of doxorubicin alone already induced apoptosis of most cells�� an increase in doxorubicin-mediated cytotoxity of HepG� cells by addition of nimesulide was limited �Fig. ��� b�� rig�t two panels��. Fig. 2. Co-treatment of nimesulide and doxorubicin additively in�ibited t�e growt� of HepG� cells. �a�� T�e cells were treated wit� indicated �5�4�� µ� nimesulide or indicated 5�8� µ� of doxorubicin for �4 �. T�e cell survival was measured by �TT assay. Results were obtained from � independent experiments and t�e bar represents S.E. Significant c�anges between un- treated and treated samples are marked by asterisks: *p < �.�5 and **p < �.�1. �b�� T�e cells were co-treated wit� 5�8� µ� doxorubicin alone or toget�er wit� �5�1�� µ� nimesulide for �4 �. T�en t�e cell survival was measured by �TT assay. Results were obtained from 4 independent experiments and t�e bar represents t�e S.E. Significant c�anges between doxorubicin alone and co-treatment wit� nimesulide samples are marked by asterisks: *p < �.�5 To furt�er confirm t�e cytotoxic synergy between nimesulide and doxorubicin we performed morp�ol- ogy study by staining cells wit� acridine orange. We observed t�e normal morp�ology of drug-untreated HepG� cells: s�ape of tri- or multi-angles wit� abundant �6 Experimental Oncology ���� ������� ����� ��arc��� cytoplasma�� and large oval nuclei wit� dispersed c�ro- matin �Fig. ��� a�� left panel��. �4 � after treatment wit� 1�� µ� of nimesulide and 1� µ� of doxorubicin�� HepG� cells ex�ibited t�e typical morp�ology of apoptotic cells�� including cell s�rinkage�� deep-dyed pyknotic nuclei�� margination of nuclear c�romatin�� cytoplasmic blebbing and clusters of apoptotic bodies �Fig. ��� a�� rig�t panel��. Also�� we measured t�e DNA content by propidium iodide �PI�� staining�� and cell apoptosis was reflected by t�e appearance of a cell population wit� subdiploid and pre-G1p�ase t�roug� flow cytometric analysis. Consistent wit� �TT assay�� addition of 1�� µ� of nimesulide significantly increased a portion of sub- diploid and pre-G1 p�ase ��1.��%�� compared to t�at of doxorubicin alone group �1�.6%�� �Fig. ��� b�� bottom two panels��. By contrast�� a muc� smaller portion of pre-G1 p�ase was s�own in t�e cells treated wit� nimesulide alone �Fig. ��� b�� rig�t top panel��. Fig. 3. Co-treatment of nimesulide and doxorubicin en�anced apoptosis induction of HepG� cells. �a�� T�e HepG� cells were treated wit� or wit�out nimesulide 1�� µ� and doxorubicin 1� µ� for �4 � and stained wit� acridine orange. T�e cell morp�ology was observed under fluorescent microscope. �b�� Flow cytometry analysis of DNA content of HepG� cells after treated wit� 1�� µ� of nimesulide and/or �� µ� of doxorubicin for �4 �. Represen- tative DNA �istograms were from � independent experiments. T�e percentage of pre-G1 p�ase at various culture conditions is indicated Co-treatment with doxorubicin and nimesulide reduces production of VEGF in HepG2 cells. VEGF�� one of t�e most potent angiogenic factors�� �as been s�own to play a pivotal role in tumor angiogenesis�� in- cluding HCC. A line of evidence reveals t�at t�e elevated COX-� expression correlates wit� increased VEGF level and microvascular density in �uman HCCs [16�� �4�� �5]. However�� it is not known w�et�er t�e in�ibition of COX-� reduces VEGF production in �epatocellular carcinoma cells. To test t�is possibility�� we treated HepG� cells wit� �5 µ� or 5� µ� of nimesulide and measured VEGF levels in t�e culture supernatants by an ELISA. As s�own in Fig. 4�� treatment wit� 5� µ� of nimesulide alone led to an about � fold reduction in VEGF levels and t�is effect was largely augmented by addition of 5 µ� or 1� µ� of doxorubicin. VEGF production was also significantly reduced if t�e cells were co-treated wit� doxorubicin and a lower concentration ��5 µ��� of nimesulide�� sug- gesting t�e synergistic in�ibition of VEGF production in HepG� cells by two agents. Fig. 4. Co-treatment wit� nimesulide and doxorubicin reduced VEGF production of cultured HepG� cells. T�e cells were co- treated wit� 5�1� µ� doxorubicin and �5�5� µ� nimesulide for 48 �. T�e VEGF levels were determined in culture supernatants by ELISA following t�e manufacturer’s protocol. VEGF secretion was significantly reduced in t�e co-treatment group compared wit� t�e single nimesulide or doxorubicin treated group �*p < �.�5�� DISCUSSION Doxorubicin is one of t�e most often used drugs for treatment of HCC and single use of doxorubicin yields response rate of about ��% for unresectable tumors. However�� t�ere is no convincing evidence t�at t�e use of doxorubicin improves t�e prognosis of patients wit� HCC�� t�erefore t�e effect of t�is drug on HCC is still limited [�����]. NSAIDs�� suc� as aspirin�� indomet�a- cin and sulindac�� may play a role in t�e in�ibition of proliferation and induction of apoptosis in tumor cells t�roug� t�e in�ibition of COX-� activity [����5]. T�e anti-inflammatory and anti-angiogenic effects of NSAIDs �ave been explored for t�e cancer t�erapy and some of t�ese agents are currently under clinical trials [�6�� ���]. Nimesulide�� a specific COX-� in�ibitor�� can bind specifically to t�e large catalytic moiety of COX-��� wit� muc� less adverse effects on t�e gastrointestinal tract compared to t�e non-specific NSAIDs. A selective COX-� in�ibitor JTE-5�� �as been reported to en�ance cytotoxity in bladder cancer wit� 5-fluorouracil [�8]. A combination of common antitumor drugs and COX-� in�ibitors may en�ance c�emot�erapeutic efficacy�� reduce drug dose and adverse side effects. It �as been s�own t�at nimesulide in�ibits t�e growt� of �uman �epatoma cell line S��C-�����1 in vitro [1��]. However�� studies on t�e combination of selective COX-� in�ibi- tors including nimesulide and common c�emot�erapy agents against �uman �epatocellular carcinoma are not documented. In t�is study�� we investigated t�e effects of a combination of nimesulide and doxorubi- cin on t�e growt� in�ibition in �uman �epatocellular Experimental Oncology ���� ������� ����� ��arc��� ������� ������� ����� ��arc��� ����arc��� ����� ��� ��� carcinoma HepG� cells. Our results s�owed t�at treat- ment of nimesulide significantly in�ibited cell growt� in HepG� cells. �oreover�� t�e combination of doxorubi- cin and nimesulide additively increased t�e cytotoxicity and growt� in�ibition in HepG� cells. T�erefore�� our results suggest t�at t�e use of COX-� in�ibitors may be beneficial w�en combined wit� doxorubicin for t�e treatment of patients wit� HCC. Prostaglandins�� including PGE��� synt�esized by COX enzymes�� are reported to increase cell growt� and induce proliferation in t�e cultured rat �epatocytes [���� 4�]. In �uman �epatocellular carcinoma cells�� treatment wit� prostaglandin E� �PGE��� increases VEGF production and t�is effect is blocked by in�ibition of COX-��� suggesting a link of COX-� wit� VEGF signaling in �epatocarcinogenesis [16]. In support of t�ese find- ings�� we �ave observed t�e �ig� expression of COX-� protein in HepG� cells and in�ibition of COX-� by nime- sulide led to reduced production of PGE� and VEGF�� and decreased viable cells in t�e culture. T�erefore�� t�e interplay between COX-�-derived prostaglandin signaling and ot�er growt�-regulatory pat�ways suc� as VEGF is expected to provide important t�erapeutic implications. Apoptosis is an important p�ysiological process t�at prevents t�e formation of tumor clone and t�e failures of apoptosis lead to t�e development of many tumors including �epatocellular carcinoma [41]. T�e recent reports �ave demonstrated t�at NSAIDs induce apoptosis in different tumor cells [1��� 4�]. It is also conceivable t�at apoptosis mig�t occur in t�e �uman �epatocellular carcinoma cells in response to nime- sulide. To evaluate t�e role of nimesulide in cell apop- tosis�� we cultured HepG� cells and treated cells wit� various concentrations of nimesulide or toget�er wit� a low concentration of doxorubicin. Flow cytometry analysis of sub-diploid peak of DNA content revealed t�e ability of nimesulide to trigger apoptosis in HepG� cells at t�ese concentrations t�at were sufficient to in�ibit cell proliferation. In addition�� t�e nimesulide-in- duced apoptosis is significantly increased by addition of a low concentration of doxorubicin. T�us�� apoptosis may be one of t�e mec�anisms for nimesulide to in�ibit cell growt� in HepG� cells�� especially w�en nimesulide is combined wit� doxorubicin. In patients wit� �epatocellular carcinoma�� �y- pervascularity correlated wit� t�e over-expression of VEGF and significantly associated wit� t�e tumor extension and s�orter median survival time [�5�� 4��� 44]. Prostaglandin E� increases t�e expression and t�e secretion of VEGF in �epatocellular carcinoma cells [16�� 45]. We found t�at t�e in�ibition of COX-� by nimesulide reduced VEGF production in HepG� cells. Interestedly�� treatment of doxorubicin also in�ibited VEGF secretion by HepG� cells�� and co-treatment of doxorubicin and nimesulide markedly decreased t�e levels of VEGF in cultured supernatants. Toget�er�� our data suggest t�at co-treatment wit� doxorubicin and nimesulide induces growt� in�ibition and cell deat� in part t�roug� t�e in�ibition of VEGF production in HepG� cells. 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Experimental Oncology ���� ������� ����� ��arc��� ������ ������� ����� ��arc��� ���arc��� ���� �� �� КОМБИНИРОВАННОЕ ПРИМЕНЕНИЕ ИНГИБИТОРА ЦИКЛООКСИГЕНАЗЫ-2 И ДОКСОРУБИЦИНА ПРИВОДИТ К УГНЕТЕНИЮ РОСТА И АПОПТОЗУ КЛЕТОК ГЕПАТОКАРЦИНОМЫ ЧЕЛОВЕКА Угнетение циклооксигеназы-2 (ЦОГ-2) оказывает терапевтический эффект при лечении больных с солидными опухолями и сопровождается снижением пролиферации опухолевых клеток и индукцией апоптоза. Цель: изучение роли ингибито- ра ЦОГ-2 — нимесулида в процессах роста и апоптоза культивированных клеток гепатокарциномы человека HepG2. Методы: для оценки апоптоза и угнетения роста клеток при применении нимесулида самостоятельно и в сочетании с доксорубицином применяли MTT-анализ, проточную цитометрию и стандартные морфологические методы. Результаты: установлено, что обработка клеток HepG2 cells нимесулидом в концентрации > 50 μM приводила к угнетению активности ЦОГ-2 за счет снижения продукции PGE2, после чего отмечали подавление роста и апоптоз клеток при неизмененном уровне экспрессии ЦОГ-2. Комбинированное применение 50 μM или 100 μM нимесулида и доксорубицина в концентра- ции 5–20 μM обусловило усиленное угнетение роста клеток, индукции апоптоза и снижение продукции VEGF. Выводы: полученные данные свидетельствуют о синергическом и/или аддитивном эффекте при применении ингибиторов ЦОГ-2 и химиотерапевтических препаратов. Ключевые слова: гепатокарцинома, нимесулид, ЦОГ-2, доксорубицин, апоптоз, VEGF. Copyright © Experimental Oncology, 2007