TY - JOUR
T1 - Enhancement of cisplatin cytotoxicity by SAHA involves endoplasmic reticulum stress-mediated apoptosis in oral squamous cell carcinoma cells
AU - Suzuki, Maiko
AU - Endo, Manabu
AU - Shinohara, Fumiaki
AU - Echigo, Seishi
AU - Rikiishi, Hidemi
N1 - Funding Information:
Acknowledgments We thank Mr. D. Mrozek for editing the manuscript. This work was supported in part by Grant-in-Aids for ScientiWc Research (20659309) from the Japan Society for the Promotion of Science and (19791480 and 19791482) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan.
PY - 2009/11
Y1 - 2009/11
N2 - Purpose: The histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), enhances cisplatin [cis-diammine dichloroplatinum (II)] (CDDP)-induced apoptosis in the oral squamous cell carcinoma (OSCC) cell line by complex, multifunctional mechanisms. We investigated the role of endoplasmic reticulum (ER) stress in the enhancing effect of SAHA on CDDP, compared with the ER stressor thapsigargin. Methods: We chose OSCC cell line HSC-3 to ascertain the mechanism of SAHA-enhanced cytotoxicity among various cell lines. HSC-3 cells were incubated with CDDP/SAHA for 48 h, followed by the assessment of cell chemosensitivity to CDDP with MTT and TUNEL assays. Western blot analysis was used to detect the expressions of ER-related molecules, and flow cytometry was used to monitor caspase activity. Results: Treatment with CDDP/SAHA potently induced apoptosis in HSC-3 cells with a significant increase in caspase-4 and -12 functions. For example, 60% of cells became apoptotic after 48 h of treatment with CDDP/SAHA. In addition, SAHA alone rapidly induced sustained phosphorylation of eukaryotic translation initiation factor-2 (eIF2)α, which is up-regulated during ER stress. Inhibition of ER stress by salubrinal, an inhibitor of eIF2α dephosphorylation, abrogated SAHA's enhancement of CDDP cytotoxicity. Levels of phospho-Akt are decreased in SAHA-treated cells, and this is in turn associated with increased activity of protein phosphatase 1 (PP1) by SAHA, the phosphatase upstream of Akt. Conclusion: These data indicate that up-regulation of specific-ER stress-associated events is an integral part of the mechanism by which SAHA enhances CDDP-induced apoptosis, and PP1 up-regulation followed by Akt dephosphorylation plays an important role in SAHA-enhanced CDDP apoptosis.
AB - Purpose: The histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), enhances cisplatin [cis-diammine dichloroplatinum (II)] (CDDP)-induced apoptosis in the oral squamous cell carcinoma (OSCC) cell line by complex, multifunctional mechanisms. We investigated the role of endoplasmic reticulum (ER) stress in the enhancing effect of SAHA on CDDP, compared with the ER stressor thapsigargin. Methods: We chose OSCC cell line HSC-3 to ascertain the mechanism of SAHA-enhanced cytotoxicity among various cell lines. HSC-3 cells were incubated with CDDP/SAHA for 48 h, followed by the assessment of cell chemosensitivity to CDDP with MTT and TUNEL assays. Western blot analysis was used to detect the expressions of ER-related molecules, and flow cytometry was used to monitor caspase activity. Results: Treatment with CDDP/SAHA potently induced apoptosis in HSC-3 cells with a significant increase in caspase-4 and -12 functions. For example, 60% of cells became apoptotic after 48 h of treatment with CDDP/SAHA. In addition, SAHA alone rapidly induced sustained phosphorylation of eukaryotic translation initiation factor-2 (eIF2)α, which is up-regulated during ER stress. Inhibition of ER stress by salubrinal, an inhibitor of eIF2α dephosphorylation, abrogated SAHA's enhancement of CDDP cytotoxicity. Levels of phospho-Akt are decreased in SAHA-treated cells, and this is in turn associated with increased activity of protein phosphatase 1 (PP1) by SAHA, the phosphatase upstream of Akt. Conclusion: These data indicate that up-regulation of specific-ER stress-associated events is an integral part of the mechanism by which SAHA enhances CDDP-induced apoptosis, and PP1 up-regulation followed by Akt dephosphorylation plays an important role in SAHA-enhanced CDDP apoptosis.
KW - Apoptosis
KW - Cisplatin
KW - Endoplasmic reticulum stress
KW - Oral squamous cell carcinoma
KW - Suberoylanilide hydroxamic acid
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U2 - 10.1007/s00280-009-0969-x
DO - 10.1007/s00280-009-0969-x
M3 - Article
C2 - 19280190
AN - SCOPUS:69049084488
SN - 0344-5704
VL - 64
SP - 1115
EP - 1122
JO - Cancer Chemotherapy and Pharmacology
JF - Cancer Chemotherapy and Pharmacology
IS - 6
ER -