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The immunomodulator PSK induces in vitro cytotoxic activity in tumour cell lines via arrest of cell cycle and induction of apoptosis.

Jiménez-Medina E, Berruguilla E, Romero I, Algarra I, Collado A, Garrido F, Garcia-Lora A - BMC Cancer (2008)

Bottom Line: The inhibition ranged from 22 to 84%.Inhibition mechanisms were identified as cell cycle arrest, with cell accumulation in G0/G1 phase and increase in apoptosis and caspase-3 expression.In contrast, PSK shows a synergistic effect with IL-2 that increases PBL proliferation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Servicio de Análisis Clínicos e Inmunologia, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Av, de las Fuerzas Armadas 2, 18014 Granada, Spain. evajimenez@fundacionhvn.org

ABSTRACT

Background: Protein-bound polysaccharide (PSK) is derived from the CM-101 strain of the fungus Coriolus versicolor and has shown anticancer activity in vitro and in in vivo experimental models and human cancers. Several randomized clinical trials have demonstrated that PSK has great potential in adjuvant cancer therapy, with positive results in the adjuvant treatment of gastric, esophageal, colorectal, breast and lung cancers. These studies have suggested the efficacy of PSK as an immunomodulator of biological responses. The precise molecular mechanisms responsible for its biological activity have yet to be fully elucidated.

Methods: The in vitro cytotoxic anti-tumour activity of PSK has been evaluated in various tumour cell lines derived from leukaemias, melanomas, fibrosarcomas and cervix, lung, pancreas and gastric cancers. Tumour cell proliferation in vitro was measured by BrdU incorporation and viable cell count. Effect of PSK on human peripheral blood lymphocyte (PBL) proliferation in vitro was also analyzed. Studies of cell cycle and apoptosis were performed in PSK-treated cells.

Results: PSK showed in vitro inhibition of tumour cell proliferation as measured by BrdU incorporation and viable cell count. The inhibition ranged from 22 to 84%. Inhibition mechanisms were identified as cell cycle arrest, with cell accumulation in G0/G1 phase and increase in apoptosis and caspase-3 expression. These results indicate that PSK has a direct cytotoxic activity in vitro, inhibiting tumour cell proliferation. In contrast, PSK shows a synergistic effect with IL-2 that increases PBL proliferation.

Conclusion: These results indicate that PSK has cytotoxic activity in vitro on tumour cell lines. This new cytotoxic activity of PSK on tumour cells is independent of its previously described immunomodulatory activity on NK cells.

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Related in: MedlinePlus

Caspase-3 expression in tumour cell lines treatedwith PSK. AGS and B9 tumour cell lines were treated with 50 μg/ml of PSK and expression was analysed by flow cytometry using FITC conjugated monoclonal anti-active-caspase-3 antibody. Data indicate the percentage of cells positive for presence of active-caspase-3. PSK produced increased caspase-3 expression in AGS but not in B9 tumour cell lines. Results are representative of three experiments.
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Figure 6: Caspase-3 expression in tumour cell lines treatedwith PSK. AGS and B9 tumour cell lines were treated with 50 μg/ml of PSK and expression was analysed by flow cytometry using FITC conjugated monoclonal anti-active-caspase-3 antibody. Data indicate the percentage of cells positive for presence of active-caspase-3. PSK produced increased caspase-3 expression in AGS but not in B9 tumour cell lines. Results are representative of three experiments.

Mentions: Caspases are the main enzymes involved in the apoptotic pathway and the participation of active caspase-3 in PSK-induced apoptosis was evaluated. Tumour cells were treated with PSK (100 μg/ml) for 4 days, then permeabilized, fixed and stained for active human caspase-3 and analyzed by flow cytometry. In the AGS cell line, untreated cells were negative for presence of active-caspase-3, whereas around 36% of PSK-treated cells showed detectable active caspase-3 (Fig. 6). However, in tumour cell lines in which PSK did not produce apoptosis, e.g., B9 tumour cells, no caspase-3 expression was detected after PSK treatment (Fig. 6). Table 4 depicts the results obtained with the other tumour cell lines analysed.


The immunomodulator PSK induces in vitro cytotoxic activity in tumour cell lines via arrest of cell cycle and induction of apoptosis.

Jiménez-Medina E, Berruguilla E, Romero I, Algarra I, Collado A, Garrido F, Garcia-Lora A - BMC Cancer (2008)

Caspase-3 expression in tumour cell lines treatedwith PSK. AGS and B9 tumour cell lines were treated with 50 μg/ml of PSK and expression was analysed by flow cytometry using FITC conjugated monoclonal anti-active-caspase-3 antibody. Data indicate the percentage of cells positive for presence of active-caspase-3. PSK produced increased caspase-3 expression in AGS but not in B9 tumour cell lines. Results are representative of three experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2291471&req=5

Figure 6: Caspase-3 expression in tumour cell lines treatedwith PSK. AGS and B9 tumour cell lines were treated with 50 μg/ml of PSK and expression was analysed by flow cytometry using FITC conjugated monoclonal anti-active-caspase-3 antibody. Data indicate the percentage of cells positive for presence of active-caspase-3. PSK produced increased caspase-3 expression in AGS but not in B9 tumour cell lines. Results are representative of three experiments.
Mentions: Caspases are the main enzymes involved in the apoptotic pathway and the participation of active caspase-3 in PSK-induced apoptosis was evaluated. Tumour cells were treated with PSK (100 μg/ml) for 4 days, then permeabilized, fixed and stained for active human caspase-3 and analyzed by flow cytometry. In the AGS cell line, untreated cells were negative for presence of active-caspase-3, whereas around 36% of PSK-treated cells showed detectable active caspase-3 (Fig. 6). However, in tumour cell lines in which PSK did not produce apoptosis, e.g., B9 tumour cells, no caspase-3 expression was detected after PSK treatment (Fig. 6). Table 4 depicts the results obtained with the other tumour cell lines analysed.

Bottom Line: The inhibition ranged from 22 to 84%.Inhibition mechanisms were identified as cell cycle arrest, with cell accumulation in G0/G1 phase and increase in apoptosis and caspase-3 expression.In contrast, PSK shows a synergistic effect with IL-2 that increases PBL proliferation.

View Article: PubMed Central - HTML - PubMed

Affiliation: Servicio de Análisis Clínicos e Inmunologia, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Av, de las Fuerzas Armadas 2, 18014 Granada, Spain. evajimenez@fundacionhvn.org

ABSTRACT

Background: Protein-bound polysaccharide (PSK) is derived from the CM-101 strain of the fungus Coriolus versicolor and has shown anticancer activity in vitro and in in vivo experimental models and human cancers. Several randomized clinical trials have demonstrated that PSK has great potential in adjuvant cancer therapy, with positive results in the adjuvant treatment of gastric, esophageal, colorectal, breast and lung cancers. These studies have suggested the efficacy of PSK as an immunomodulator of biological responses. The precise molecular mechanisms responsible for its biological activity have yet to be fully elucidated.

Methods: The in vitro cytotoxic anti-tumour activity of PSK has been evaluated in various tumour cell lines derived from leukaemias, melanomas, fibrosarcomas and cervix, lung, pancreas and gastric cancers. Tumour cell proliferation in vitro was measured by BrdU incorporation and viable cell count. Effect of PSK on human peripheral blood lymphocyte (PBL) proliferation in vitro was also analyzed. Studies of cell cycle and apoptosis were performed in PSK-treated cells.

Results: PSK showed in vitro inhibition of tumour cell proliferation as measured by BrdU incorporation and viable cell count. The inhibition ranged from 22 to 84%. Inhibition mechanisms were identified as cell cycle arrest, with cell accumulation in G0/G1 phase and increase in apoptosis and caspase-3 expression. These results indicate that PSK has a direct cytotoxic activity in vitro, inhibiting tumour cell proliferation. In contrast, PSK shows a synergistic effect with IL-2 that increases PBL proliferation.

Conclusion: These results indicate that PSK has cytotoxic activity in vitro on tumour cell lines. This new cytotoxic activity of PSK on tumour cells is independent of its previously described immunomodulatory activity on NK cells.

Show MeSH
Related in: MedlinePlus