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Pseudomonas aeruginosa exotoxin A reduces chemoresistance of oral squamous carcinoma cell via inhibition of heat shock proteins 70 (HSP70).

Park SR, Lee KD, Kim UK, Gil YG, Oh KS, Park BS, Kim GC - Yonsei Med. J. (2010)

Bottom Line: On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells.While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Anatomy, School of Dentistry, Research Institute for Oral Biotechnology, Pusan National University, Yangsan, Korea.

ABSTRACT

Purpose: Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9).

Materials and methods: The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis.

Results: While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.

Conclusion: Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

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Related in: MedlinePlus

Involvement of E2F-1, Apaf-1, and caspase-9 in PEA-induced apoptosis. YD-9 cells were cultured in the presence of 15 nM PEA for the indicated time, and whole cell lysates were subjected to Western blot analysis of E2F-1 (56 kDa), Apaf-1 (130 kDa), and caspase-9 (full-length, 49 kDa; cleaved, 37 kDa).
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Figure 6: Involvement of E2F-1, Apaf-1, and caspase-9 in PEA-induced apoptosis. YD-9 cells were cultured in the presence of 15 nM PEA for the indicated time, and whole cell lysates were subjected to Western blot analysis of E2F-1 (56 kDa), Apaf-1 (130 kDa), and caspase-9 (full-length, 49 kDa; cleaved, 37 kDa).

Mentions: The transcription factor E2F-1 plays a role in apoptosis as well as cell cycle progression and enhances the expression of Apaf-1. Therefore, the changes in the expression of E2F-1, Apaf-1, and caspase-9 were investigated in YD-9 cells. As shown in Fig. 6, E2F-1 expression levels were markedly increased at 16 and 24 hours after PEA treatment and decreased thereafter. The expression of Apaf-1 increased at 16 and 24 hours after PEA treatment. These observations were accompanied by initial caspase-9 cleavage at 16 hours, with cleaved protein, reaching a peak concentration between 16 and 48 hours (Fig. 6).


Pseudomonas aeruginosa exotoxin A reduces chemoresistance of oral squamous carcinoma cell via inhibition of heat shock proteins 70 (HSP70).

Park SR, Lee KD, Kim UK, Gil YG, Oh KS, Park BS, Kim GC - Yonsei Med. J. (2010)

Involvement of E2F-1, Apaf-1, and caspase-9 in PEA-induced apoptosis. YD-9 cells were cultured in the presence of 15 nM PEA for the indicated time, and whole cell lysates were subjected to Western blot analysis of E2F-1 (56 kDa), Apaf-1 (130 kDa), and caspase-9 (full-length, 49 kDa; cleaved, 37 kDa).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2908850&req=5

Figure 6: Involvement of E2F-1, Apaf-1, and caspase-9 in PEA-induced apoptosis. YD-9 cells were cultured in the presence of 15 nM PEA for the indicated time, and whole cell lysates were subjected to Western blot analysis of E2F-1 (56 kDa), Apaf-1 (130 kDa), and caspase-9 (full-length, 49 kDa; cleaved, 37 kDa).
Mentions: The transcription factor E2F-1 plays a role in apoptosis as well as cell cycle progression and enhances the expression of Apaf-1. Therefore, the changes in the expression of E2F-1, Apaf-1, and caspase-9 were investigated in YD-9 cells. As shown in Fig. 6, E2F-1 expression levels were markedly increased at 16 and 24 hours after PEA treatment and decreased thereafter. The expression of Apaf-1 increased at 16 and 24 hours after PEA treatment. These observations were accompanied by initial caspase-9 cleavage at 16 hours, with cleaved protein, reaching a peak concentration between 16 and 48 hours (Fig. 6).

Bottom Line: On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells.While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Oral Anatomy, School of Dentistry, Research Institute for Oral Biotechnology, Pusan National University, Yangsan, Korea.

ABSTRACT

Purpose: Oral squamous carcinoma (OSCC) cells exhibit resistance to chemotherapeutic agent-mediated apoptosis in the late stage of malignancy. Increased levels of heat shock proteins 70 (HSP70) in cancer cells are known to confer resistance to apoptosis. Since recent advances in the understanding of bacterial toxins have produced new strategies for the treatment of cancers, we investigated the effect of Pseudomonas aeruginosa exotoxin A (PEA) on HSP70 expression and induction of apoptosis in chemoresistant OSCC cell line (YD-9).

Materials and methods: The apoptotic effect of PEA on chemoresistant YD-9 cells was confirmed by MTT, Hoechst and TUNEL stains, DNA electrophoresis, and Western blot analysis.

Results: While YD-9 cells showed high resistance to chemotherapeutic agents such as etoposide and 5-fluorouraci (5-FU), HSP70 antisense oligonucelotides sensitized chemoresistant YD-9 cells to etoposide and 5-FU. On the other hand, PEA significantly decreased the viability of YD-9 cells by deteriorating the HSP70-relating protecting system through inhibition of HSP70 expression and inducing apoptosis in YD-9 cells. Apoptotic manifestations were evidenced by changes in nuclear morphology, generation of DNA fragmentation, and activation of caspases. While p53, p21, and E2F-1 were upregulated, cdk2 and cyclin B were downregulated by PEA treatment, suggesting that PEA caused cell cycle arrest at the G2/M checkpoint.

Conclusion: Therefore, these results indicate that PEA reduced the chemoresistance through inhibition of HSP70 expression and also induced apoptosis in chemoresistant YD-9 cells.

Show MeSH
Related in: MedlinePlus