Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide
The search for the substances sensitizing cancer cells to apoptosis induction by chemotherapeutic agents is a task of high importance in the modern strategy of anticancer therapy. The aim of the study was to investigate the apoptogenic and apoptosis-modulating activities of fucoidan (sulfated polysa...
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Інститут експериментальної патології, онкології і радіобіології ім. Р.Є. Кавецького НАН України
2007
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| Cite this: | Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide / A. Philchenkov, M. Zavelevich, T. Imbs, T. Zvyagintseva, T. Zaporozhets // Experimental Oncology. — 2007. — Т. 29, № 3. — С. 181-185. — Бібліогр.: 18 назв. — англ. |
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Philchenkov, A. Zavelevich, M. Imbs, T. Zvyagintseva, T. Zaporozhets, T. 2018-06-19T18:00:52Z 2018-06-19T18:00:52Z 2007 Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide / A. Philchenkov, M. Zavelevich, T. Imbs, T. Zvyagintseva, T. Zaporozhets // Experimental Oncology. — 2007. — Т. 29, № 3. — С. 181-185. — Бібліогр.: 18 назв. — англ. 1812-9269 https://nasplib.isofts.kiev.ua/handle/123456789/138963 The search for the substances sensitizing cancer cells to apoptosis induction by chemotherapeutic agents is a task of high importance in the modern strategy of anticancer therapy. The aim of the study was to investigate the apoptogenic and apoptosis-modulating activities of fucoidan (sulfated polysaccharide) isolated from far-eastern brown seaweeds Fucus evanescens in two human malignant lymphoid cell lines, MT-4 and Namalwa. Methods: Apoptosis was assessed morphologically and quantified by flow cytometry analysis of cells stained with propidium iodide. Caspase-3 activation was assayed by flow cytometry with the aid of labeled monoclonal antibodies. Results: The fucoidan at 500 µg/ml was not cytotoxic in MT-4 or Namalwa cells even in the setting of long-term presence in culture medium up to 14 days. Nevertheless, pretreatment of MT-4 but not Namalwa cells with fucoidan followed by the exposure to DNA topoisomerase II inhibitor etoposide led to about two-fold increase in the relative apoptotic index as compared with etoposide alone. Apoptosis enhancement of MT-4 cells by fucoidan was not accompanied by further increase in the number of the cells with active form of caspase-3. Conclusion: The present findings demonstrate for the first time that fucoidan enhances etoposide induced caspase-dependent cell death pathway in MT-4 but not Namalwa cell line. The mechanisms of such enhancement do not seem to be related directly to caspase-3 activation. Одной из важных задач современной стратегии противоопухолевой терапии является поиск веществ, повышающих чувствительность опухолевых клеток к индукции апоптоза под действием химиопрепаратов. Цель: изучение апоптогенной и апоптозмодулирующей активности фукоидана — сульфатированного полисахарида, выделенного из дальневосточной бурой водоросли Fucus evanescens, на двух линиях злокачественных лимфоидных клеток человека MT-4 и Namalwa. Методы: апоптоз выявляли морфологически и количественно проточной цитометрией клеток, окрашенных йодистым пропидием. Активацию каспазы-3 изучали методом проточной цитометрии клеток после реакции с конъюгированными моноклональными антителами. Результаты: фукоидан в дозе 500 мкг/мл не проявлял токсичности в клетках MT-4 или Namalwa даже при длительном присутствии препарата в культурах до 14 сут. Предварительная инкубация клеток MT-4 с фукоиданом в указанной дозе приводила к двукратному повышению относительного апоптотического индекса при действии ингибитора ДНК топоизомеразы II этопозида, причем такого эффекта в клетках Namalwa не отмечено. Повышение апоптотического индекса в клетках MT-4 под влиянием фукоидана при индукции апоптоза этопозидом не сопровождалось приростом процентного содержания клеток с активной формой каспазы-3, в сравнении с таковым при действии одного лишь индуктора апоптоза этопозида. Выводы: впервые продемонстрирована способность фукоидана усиливать этопозидиндуцированный каспазозависимый апоптоз в клетках MT-4. Подобный эффект отсутствовал в клетках Namalwa. Механизм повышения чувствительности злокачественных лимфоидных клеток человека к этопозиду при действии фукоидана, по-видимому, напрямую не связан с активацией каспазы-3. This work was partly supported by the joint grants of Siberian Branch of the Russian Academy of Medical Sciences and Far East Division of Russian Academy of Sciences NN 05-II-CM-05-007, 06-II-CM-05-004, grant of Russian Foundation of Fundamental Research and the research program “Molecular and Cellular Biology” of the Russian Academy of Sciences. The authors are thankful to Dr. Natalia Khranovskaya (Kyiv, Ukraine) for her excellent expert assistance in flow cytometry. en Інститут експериментальної патології, онкології і радіобіології ім. Р.Є. Кавецького НАН України Experimental Oncology Original contributions Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide Повышение чувствительности злокачественных лимфоидных клеток человека к этопозиду при действии фукоидана полисахарида бурых водорослей Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| spellingShingle |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide Philchenkov, A. Zavelevich, M. Imbs, T. Zvyagintseva, T. Zaporozhets, T. Original contributions |
| title_short |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| title_full |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| title_fullStr |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| title_full_unstemmed |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| title_sort |
sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide |
| author |
Philchenkov, A. Zavelevich, M. Imbs, T. Zvyagintseva, T. Zaporozhets, T. |
| author_facet |
Philchenkov, A. Zavelevich, M. Imbs, T. Zvyagintseva, T. Zaporozhets, T. |
| 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 |
Повышение чувствительности злокачественных лимфоидных клеток человека к этопозиду при действии фукоидана полисахарида бурых водорослей |
| description |
The search for the substances sensitizing cancer cells to apoptosis induction by chemotherapeutic agents is a task of high importance in the modern strategy of anticancer therapy. The aim of the study was to investigate the apoptogenic and apoptosis-modulating activities of fucoidan (sulfated polysaccharide) isolated from far-eastern brown seaweeds Fucus evanescens in two human malignant lymphoid cell lines, MT-4 and Namalwa. Methods: Apoptosis was assessed morphologically and quantified by flow cytometry analysis of cells stained with propidium iodide. Caspase-3 activation was assayed by flow cytometry with the aid of labeled monoclonal antibodies. Results: The fucoidan at 500 µg/ml was not cytotoxic in MT-4 or Namalwa cells even in the setting of long-term presence in culture medium up to 14 days. Nevertheless, pretreatment of MT-4 but not Namalwa cells with fucoidan followed by the exposure to DNA topoisomerase II inhibitor etoposide led to about two-fold increase in the relative apoptotic index as compared with etoposide alone. Apoptosis enhancement of MT-4 cells by fucoidan was not accompanied by further increase in the number of the cells with active form of caspase-3. Conclusion: The present findings demonstrate for the first time that fucoidan enhances etoposide induced caspase-dependent cell death pathway in MT-4 but not Namalwa cell line. The mechanisms of such enhancement do not seem to be related directly to caspase-3 activation.
Одной из важных задач современной стратегии противоопухолевой терапии является поиск веществ, повышающих
чувствительность опухолевых клеток к индукции апоптоза под действием химиопрепаратов. Цель: изучение апоптогенной и
апоптозмодулирующей активности фукоидана — сульфатированного полисахарида, выделенного из дальневосточной бурой
водоросли Fucus evanescens, на двух линиях злокачественных лимфоидных клеток человека MT-4 и Namalwa. Методы: апоптоз
выявляли морфологически и количественно проточной цитометрией клеток, окрашенных йодистым пропидием. Активацию
каспазы-3 изучали методом проточной цитометрии клеток после реакции с конъюгированными моноклональными антителами.
Результаты: фукоидан в дозе 500 мкг/мл не проявлял токсичности в клетках MT-4 или Namalwa даже при длительном
присутствии препарата в культурах до 14 сут. Предварительная инкубация клеток MT-4 с фукоиданом в указанной дозе
приводила к двукратному повышению относительного апоптотического индекса при действии ингибитора ДНК топоизомеразы II
этопозида, причем такого эффекта в клетках Namalwa не отмечено. Повышение апоптотического индекса в клетках MT-4
под влиянием фукоидана при индукции апоптоза этопозидом не сопровождалось приростом процентного содержания клеток с
активной формой каспазы-3, в сравнении с таковым при действии одного лишь индуктора апоптоза этопозида. Выводы: впервые
продемонстрирована способность фукоидана усиливать этопозидиндуцированный каспазозависимый апоптоз в клетках MT-4.
Подобный эффект отсутствовал в клетках Namalwa. Механизм повышения чувствительности злокачественных лимфоидных
клеток человека к этопозиду при действии фукоидана, по-видимому, напрямую не связан с активацией каспазы-3.
|
| issn |
1812-9269 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/138963 |
| citation_txt |
Sensitization of human malignant lymphoid cells to etoposide by fucoidan, a brown seaweed polysaccharide / A. Philchenkov, M. Zavelevich, T. Imbs, T. Zvyagintseva, T. Zaporozhets // Experimental Oncology. — 2007. — Т. 29, № 3. — С. 181-185. — Бібліогр.: 18 назв. — англ. |
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2025-11-24T16:26:15Z |
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| fulltext |
Experimental Oncology ���� ��������� ����� ��eptem�er�� ������� ��������� ����� ��eptem�er�� ����eptem�er�� ����� ��� ���
Etoposide is a widely prescri�ed and potent anti-
cancer drug �elonging to DNA topoisomerase II inhi�i-
tors�� which sta�ilize enzyme-DNA cleavage complexes
forming nonrepaira�le protein-linked DNA dou�le
strand �reaks [��� �]. The cells injured in such a way
are finally eliminated �y apoptosis.
Although the most efficacious chemotherapeutic
regimens for utilizing DNA topoisomerase II inhi�itors
were developed over the past several years�� their use-
fulness has �een limited �y the frequent development
of drug resistance. Chemosensitization consisting in
using one drug or agent to render cancer cells more
suscepti�le to a second agent represents the novel
strategy to enhance the effects of cytotoxic thera-
peutics [3].
During the past decade�� the search of novel su�-
stances with considera�le potential for chemosensiti-
zation was advantageous in revealing the compounds
of natural origin possessing the a�ility of enhancing
the cytotoxic activity of chemotherapeutics. For ex-
ample�� deguelin�� a plant-derived su�stance�� markedly
enhances chemosensitivity of human leukaemia cells
to etoposide or cytara�ine [4]. Recently�� the polysac-
charides and peptides�� isolated from seaweeds have
�ecome a matter of great interest for cancer therapy.
The mechanisms of their anticancer activity are related
to their a�ility to suppress the growth of cancer cells
�cytotoxic or cytostatic effects���� to enhance the im-
mune responses�� and to inhi�it tumor angiogenesis
[���]. �everal marine algal polysaccharides�� fucoi-
dans in particular�� have �een found to induce apopto-
sis in cancer cells [����]. Nevertheless�� the question
whether these su�stances are a�le to modulate the
apoptosis induced �y chemotherapeutic agents has
�een yet unresolved. Com�ining fucoidan with etopo-
side may �e a novel strategy that has the potential for
improving the antineoplastic activity of etoposide. This
study was designed to test this hypothesis.
MATERIALS AND METHODS
Materials and reagents. Far-eastern �rown sea-
weeds F. evanescens�� which have �een collected in
Okhotsk �ea in August ������ were used in this study.
Etoposide was purchased from Brystol-Myers �qui��
�pA �Italy��.
Extraction and purification of fucoidan. Fucoi-
dan from F. evanescens was prepared as descri�ed
in [��]. After removal of small shells and mechanical
impurities�� fresh seaweed F. evanescens ��� kg�� was
extracted with ethanol at a �:� ratio at temperature
of �� °C for �4 h. The extract was separated and
ethanol was evaporated to o�tain a concentrate of
�iologically active low-molecular su�stances. The
processed seaweeds were dried and extracted with
�.� M solution of hydrochloric acid �pH �.���.��� for
�� h at ����� °C. The extract was concentrated up
to ��% of initial volume �y ultrafiltration�� neutralized
to pH 6.� and evaporated up to � L. The concentrate
SENSITIZATION OF HUMAN MALIGNANT LYMPHOID CELLS
TO ETOPOSIDE BY FUCOIDAN, A BROwN SEAwEED
POLYSACCHARIDE
A. Philchenkov1, *, M. Zavelevich1, T. Imbs2, T. Zvyagintseva2, T. Zaporozhets3
1R.E. Kavetsky Institute of Experimental Pathology, Oncology and Radiobiology,
National Academy of Sciences of Ukraine, 03022 Kyiv, Ukraine
2Pacific Ocean Institute of Bioorganic Chemistry, Far East Division,
Russian Academy of Sciences, 690022 Vladivostok, Russia
3Research Institute of Epidemiology and Microbiology, Siberian Branch,
Russian Academy of Medical Sciences, 690087 Vladivostok, Russia
The search for the substances sensitizing cancer cells to apoptosis induction by chemotherapeutic agents is a task of high importance
in the modern strategy of anticancer therapy. The aim of the study was to investigate the apoptogenic and apoptosis-modulating
activities of fucoidan (sulfated polysaccharide) isolated from far-eastern brown seaweeds Fucus evanescens in two human malignant
lymphoid cell lines, MT-4 and Namalwa. Methods: Apoptosis was assessed morphologically and quantified by flow cytometry analy-
sis of cells stained with propidium iodide. Caspase-3 activation was assayed by flow cytometry with the aid of labeled monoclonal
antibodies. Results: The fucoidan at 500 µg/ml was not cytotoxic in MT-4 or Namalwa cells even in the setting of long-term pres-
ence in culture medium up to 14 days. Nevertheless, pretreatment of MT-4 but not Namalwa cells with fucoidan followed by the
exposure to DNA topoisomerase II inhibitor etoposide led to about two-fold increase in the relative apoptotic index as compared
with etoposide alone. Apoptosis enhancement of MT-4 cells by fucoidan was not accompanied by further increase in the number
of the cells with active form of caspase-3. Conclusion: The present findings demonstrate for the first time that fucoidan enhances
etoposide induced caspase-dependent cell death pathway in MT-4 but not Namalwa cell line. The mechanisms of such enhancement
do not seem to be related directly to caspase-3 activation.
Key words: fucoidan, brown seaweed, apoptosis, human malignant lymphoid cells, etoposide, caspase-3.
Received: August 27, 2007.
*Correspondence: Fax: +380 44 2581 656
E-mail: a_philch@onconet.kiev.ua
Exp Oncol �����
���� 3�� �������
��� Experimental Oncology ���� ��������� ����� ��eptem�er��
was further neutralized and precipitated with two vol-
umes of ethanol. The precipitate was washed out with
�6% ethanol and dried. Molecular weigth of fucoidan
from F. evanescens was ����� kDa; with the follow-
ing monosaccharide content �%��: Fuc — ��4�� Xyl — 6��
Man — ��� Glc — 4�� Gal — ��; Fuc:�O4
�� mol/mol — �:
����������. For cell culture experiments�� the aqueous
stock solution of fucoidan was prepared at � mg/ml
and sterilized in �oiling water �ath. The solution was
stored at 4 °C prior to the use.
Cell culture and morphology. Human T-acute
leukemia cell line MT4 and B-cell lymphoma line Na-
malwa were o�tained from the National Collection of
Cell Lines at the Institute of Experimental Pathology��
Oncology and Radio�iology �Kyiv�� Ukraine��. The cells
were grown in suspension in RPMI-�64� culture me-
dium ��igma Chem. Co.�� U�A���� supplemented with
��% fetal �ovine serum ��igma Chem. Co.�� in �%
CO� — ��% air atmosphere at 3�� °C and ���% humid-
ity. Cells were su�cultured once in 3 days �y dilution
with the fresh medium. Cell via�ility was evaluated in
hemocytometer after staining with �.�% Trypan �lue.
For studying cell morphology�� cells were cytospined
and stained �y May—Grunwald—Giemsa technique.
Detection of apoptotic cells. Apoptotic cells with
hypodiploid DNA content were detected as previously
reported [�3]. In �rief�� cells in exponential growth
phase were incu�ated with ��� µg/ml fucoidan for
the time indicated followed �y �� h incu�ation with
etoposide at a dose of 4 µg/ml �MT-4 cells�� or 4� µg/ml
�Namalwa cells��. The cells were washed with ice-cold
PB��� harvested and stained with �� µg/ml propidium
iodide �PI�� in phosphate-�uffered saline containing
�.�% sodium citrate�� �.�% Triton X-����� and �� µg/ml
RNase A. The DNA content of cells was analyzed with
FAC�can flow cytometer �Becton Dickinson�� U�A��. The
relative apoptotic index was calculated as follows:
Apoptotic percentage in presence of inducer —
Spontaneous apoptotic percentage
————————————————————————————————————————————————————— x 100%.
100% — Spontaneous apoptotic percentage
Caspase-3 activation assay. The percentage
of cells expressing active form of caspase-3 was
assessed �y flow cytometry with the use of a FITC-
conjugated monoclonal active caspase-3 anti�ody
kit �Becton Dickinson Biosciences�� U�A��. MT-4 or
Namalwa cells were pretreated with fucoidan and in-
cu�ated with or without etoposide as indicated a�ove.
The cells were collected and rinsed with ice-cold PB�.
Then these cells were permea�ilized and immunos-
tained according to the procedure recommended �y
the manufacturer. Data were analyzed �y using Cell-
Quest software �BD Biosciences�� U�A��.
Statistical analysis. The �tudent t test was used
to analyze the data. P value of < �.�� was considered
statistically significant.
RESULTS
The incu�ation of �oth MT-4 and Namalwa cells in
the presence of fucoidan at the doses up to ��� µg/ml
did not affect cell growth kinetics �Fig. ���.
Fig. 1. Effect of fucoidan on growth of MT-4 �a�� and Namalwa �b��
cells. Fucoidan was added at ��� µg/ml. Each experiment was
performed in triplicate and mean ± �.D. is indicated.
At this maximal dose �eing assayed�� fucoidan
did not increase the percentage of apoptotic cells
in �oth cell lines upon ��-hour treatment. Moreover��
no apoptotic effect was evident when the cells were
incu�ated in the presence of fucoidan for �4 days with
fresh fucoidan solution �eing added each time the cells
were su�cultured �Fig. ��� a��. Upon such a long-term
treatment with fucoidan�� cell morphology remained
unaltered �data not shown��.
Pre-incu�ation with ��� µg/ml fucoidan for �� h
followed �y apoptosis induction with etoposide has
resulted in a�out twice as much increase in the per-
centage of hypodiploid MT-4 cells as compared to
the cells treated with etoposide alone. The sensitiza-
tion effect of the same magnitude was also evident
in MT-4 cells incu�ated with ��� µg/ml fucoidan for
�4 days followed �y apoptosis induction with etoposide
�see Fig. ��� a��. When Namalwa cells were assayed in
the similar experimental setting�� the percentage of
hypodipoid cells upon etoposide treatment of control
culture did not differ significantly from that in the cul-
ture pre-incu�ated with fucoidan �Fig. ��� b��. No effects
of sensitization in Namalwa cells could �e detecta�le
upon long-term pretreatment with fucoidan.
Because caspase activation is known to �e involved
in etoposide-induced apoptosis [�4]�� we attempted to
evaluate the percentage of MT-4 cells with the active
form of caspase-3 upon their treatment with etoposide
alone or etoposide treatment following pre-incu�ation
with fucoidan. As illustrated in Fig. 3�� the increase in
apoptotic cell percentage in MT-4 cells treated with
etoposide after their preincu�ation with fucoidan was
not accompanied �y further increase in caspase-3-
Experimental Oncology ���� ��������� ����� ��eptem�er�� ��3���� ��������� ����� ��eptem�er�� ��3�eptem�er�� ��3�� ��3 ��3
positive cells as compared with the cells treated with
etoposide only.
Fig. 2. Relative apoptotic index in MT-4 �a�� or Namalwa �b��
cells treated with fucoidan �� — ��� µg/ml �� h�� � — ��� µg/ml
�4 days���� etoposide �3���� fucoidan �� h + etoposide �4���� fucoi-
dan �4 days + etoposide ����. The concentration of etoposide
was 4 µg/ml in a and 4� µg/ml in b. Each experiment was
performed in triplicate and mean ± �.D. is indicated
*p < �.�� vs etoposide alone.
DISCUSSION
Fucoidans are major sulfated polysaccharides of
the �rown seaweed possessing the wide spectrum of
�iological activities. There have �een many reports on
anti-tumor effects of fucoidan [6�� ���� ������]. Recently��
it has �een demonstrated that fucoidan may induce
apoptosis of cancer cell acting via caspase-3 and -��
activation-dependent pathway and down-regulation of
ERK pathways �decreased phosphorylation of ERK and
G�K�� �ut not p3� or Akt�� [���� ��]. Nevertheless�� in our
study fucoidan from far-eastern �rown seaweeds F. eva
nescens did not possess apoptogenic activity in two
lines of human lymphoid malignant cells even upon the
prolonged treatment at a concentration of ��� µg/ml.
Our data are in line with the results presented recently
�y Teruya et al. [��] who demonstrated that the native
non-modified fucoidan from Cladosiphon okamuranus
did not decrease cell via�ility of U�3�� cells.
�ince fucoidan assayed in our study was not capa�le
of inducing apoptosis�� we have attempted to investigate
whether or not fucoidan could enhance the sensitivity
to etoposide of two lines of human lymphoid malignant
cells. Earlier we have shown that MT-4 and Namalwa
cells are characterized �y different intrinsic suscepti�il-
ity to apoptosis induction �y etoposide [�3]. Therefore��
etoposide dose in our experiments in Namalwa cells was
ten-fold as large as that used for apoptosis induction
in MT-4 cells providing for a�out the same apoptotic
percentage in �oth cell lines assayed. In MT-4 cells��
fucoidan was shown to �e effective as sensitizer to-
wards the apoptogenic effects of etoposide providing
for two-fold increase in the apoptotic cell percentage.
The sensitization activity of fucoidan was assessed in
cells pretreated for �� h or �4 days. The trend of incre-
ment of apoptotic cell percentage with the increasing
pre-incu�ation time was demonstrated although the
difference was not significant. In contrast�� pretreat-
ment with fucoidan did not affect the suscepti�ility of
Namalwa cells to etoposide.
Caspases are known to �e crucial mediators of
apoptosis �see review [��] for details��. To �etter under-
stand the pro�a�le mechanisms of the apoptosis en-
hancement �y fucoidan�� in particular the mechanisms
related to caspase-dependent pathway of apoptosis
induction in MT-4 cells�� we tried to assess the involve-
ment of caspase-3 in sensitization effect of fucoidan
in etoposide-induced apoptosis. While etoposide
treatment of MT-4 cells resulted in the pronounced
caspase-3 activation�� the apoptosis enhancement �y
fucoidan was not accompanied �y further increase
in the content of active form of caspase-3. �everal
explanations of this fact could �e put forward. The
optimal apoptosis induction in MT-4 cells�� especially
in case of etoposide dose �elow LD�� may require
Fig. 3. Active form of caspase-3 in MT-4 cells. a — control �without treatment��; b — fucoidan for �� h; c — etoposide 4 µg/ml;
d — fucoidan �� h + etoposide 4 µg/ml. The figures show representative staining profiles for ������� cells per experiment. M� is the
cell population defined as caspase-3-positive
��4 Experimental Oncology ���� ��������� ����� ��eptem�er��
some specified level of caspase-3 activation �a�out
3�% according to our data���� while further increment
in caspase-3 activation may �e redundant. Moreover��
other proteases are certainly involved in the realization
of etoposide-induced apoptosis. The elucidation of the
apoptosis-related intracellular targets of fucoidan will
�e addressed in future studies.
In summary�� we demonstrated�� to our knowledge
for the first time�� that fucoidan significantly sensitized
human leukemia MT-4 cells to death induced �y DNA
topoisomerase II inhi�itor etoposide. This activity of
fucoidan does not seem to �e related to caspase-3
activation-dependent pathway. �ince in Namalwa cells
the sensitization effects of fucoidan were not evident��
tumor cell of different origin should �e investigated
with regard to the cooperative role of fucoidan with
topoisomerase II inhi�itors.
ACkNOwLEDGEMENTS
This work was partly supported �y the joint grants
of �i�erian Branch of the Russian Academy of Medical
�ciences and Far East Division of Russian Academy
of �ciences NN ��-II-CM-��-������ �6-II-CM-��-��4��
grant of Russian Foundation of Fundamental Research
and the research program “Molecular and Cellular Biol-
ogy” of the Russian Academy of �ciences. The authors
are thankful to Dr. Natalia Khranovskaya �Kyiv�� Ukraine��
for her excellent expert assistance in flow cytometry.
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Experimental Oncology ���� ��������� ����� ��eptem�er�� ������� ��������� ����� ��eptem�er�� ����eptem�er�� ����� ��� ���
ПОВЫШЕНИЕ ЧУВСТВИТЕЛЬНОСТИ ЗЛОКАЧЕСТВЕННЫХ
ЛИМФОИДНЫХ КЛЕТОК ЧЕЛОВЕКА К ЭТОПОЗИДУ
ПРИ ДЕЙСТВИИ ФУКОИДАНА ПОЛИСАХАРИДА бУРЫХ
ВОДОРОСЛЕЙ
Одной из важных задач современной стратегии противоопухолевой терапии является поиск веществ, повышающих
чувствительность опухолевых клеток к индукции апоптоза под действием химиопрепаратов. Цель: изучение апоптогенной и
апоптозмодулирующей активности фукоидана — сульфатированного полисахарида, выделенного из дальневосточной бурой
водоросли Fucus evanescens, на двух линиях злокачественных лимфоидных клеток человека MT-4 и Namalwa. Методы: апоптоз
выявляли морфологически и количественно проточной цитометрией клеток, окрашенных йодистым пропидием. Активацию
каспазы-3 изучали методом проточной цитометрии клеток после реакции с конъюгированными моноклональными антителами.
Результаты: фукоидан в дозе 500 мкг/мл не проявлял токсичности в клетках MT-4 или Namalwa даже при длительном
присутствии препарата в культурах до 14 сут. Предварительная инкубация клеток MT-4 с фукоиданом в указанной дозе
приводила к двукратному повышению относительного апоптотического индекса при действии ингибитора ДНК топоизомеразы II
этопозида, причем такого эффекта в клетках Namalwa не отмечено. Повышение апоптотического индекса в клетках MT-4
под влиянием фукоидана при индукции апоптоза этопозидом не сопровождалось приростом процентного содержания клеток с
активной формой каспазы-3, в сравнении с таковым при действии одного лишь индуктора апоптоза этопозида. Выводы: впервые
продемонстрирована способность фукоидана усиливать этопозидиндуцированный каспазозависимый апоптоз в клетках MT-4.
Подобный эффект отсутствовал в клетках Namalwa. Механизм повышения чувствительности злокачественных лимфоидных
клеток человека к этопозиду при действии фукоидана, по-видимому, напрямую не связан с активацией каспазы-3.
Ключевые слова: фукоидан, бурые водоросли, апоптоз, линии злокачественных лимфоидных клеток человека, этопозид,
каспаза-3.
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