Enhancement of cisplatin [cis-diammine dichloroplatinum (II)] cytotoxicity by O6-benzylguanine involves endoplasmic reticulum stress

Cara A. Rabik, Melissa Fishel, Julianne L. Holleran, Kristen Kasza, Mark Kelley, Merrill J. Egorin, M. Eileen Dolan

Research output: Contribution to journalArticle

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Abstract

O6-Benzylguanine (BG) enhances cisplatin [cis-diammine dichloroplatinum (II)]-induced cytotoxicity and apoptosis in head and neck cancer cell lines by an unknown mechanism. We investigated the effect of cisplatin with and without BG on two targets of damage: DNA and the endoplasmic reticulum (ER). We chose three cancer cell lines to ascertain the mechanism of BG-enhanced cytotoxicity: SQ20b head and neck and SKOV-3x ovarian cancer cell lines, where BG enhanced cisplatin cytotoxicity, and A549 nonsmall cell lung cancer line, where BG did not enhance cisplatin cytotoxicity. All three lines had an increase in DNA damage when BG was added to cisplatin treatment, as evidenced by increased platination and phosphorylated histone H2AX formation. The increase in cisplatin-induced DNA damage after treatment with BG plus cisplatin is not sufficient to increase cytotoxicity or apoptosis in A549 cells. We evaluated the effect of cisplatin on the ER and observed increased caspase 12 cleavage in SQ20b and SKOV-3x cells, but not in A549 cells, after treatment with BG plus cisplatin versus cisplatin alone. Growth arrest and DNA damage inducible (GADD) 153, an ER stress-response gene, is up-regulated after treatment with BG plus cisplatin compared with cisplatin alone in SQ20b and SKOV-3x cells, but not in A549 cells. ER stress-induced apoptosis is an integral part of the mechanism by which BG enhances cisplatin. Inhibition of ER stress in the SQ20b cell line by salubrinal, an inhibitor of eIF2α dephosphorylation, or GADD153 small interfering RNA, abrogated BG-enhancement of cisplatin cytotoxicity and apoptosis through caspase 3 and 12 cleavage. These data indicate GADD153 up-regulation plays an important role in BG-enhanced cisplatin cytotoxicity and apoptosis.

Original languageEnglish
Pages (from-to)442-452
Number of pages11
JournalJournal of Pharmacology and Experimental Therapeutics
Volume327
Issue number2
DOIs
StatePublished - Nov 2008

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Endoplasmic Reticulum Stress
Cisplatin
DNA Damage
Apoptosis
Caspase 12
Cell Line
O(6)-benzylguanine
Endoplasmic Reticulum
Head and Neck Neoplasms
Non-Small Cell Lung Carcinoma
Caspase 3
Ovarian Neoplasms
Histones
Small Interfering RNA

ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

Cite this

Enhancement of cisplatin [cis-diammine dichloroplatinum (II)] cytotoxicity by O6-benzylguanine involves endoplasmic reticulum stress. / Rabik, Cara A.; Fishel, Melissa; Holleran, Julianne L.; Kasza, Kristen; Kelley, Mark; Egorin, Merrill J.; Dolan, M. Eileen.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 327, No. 2, 11.2008, p. 442-452.

Research output: Contribution to journalArticle

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abstract = "O6-Benzylguanine (BG) enhances cisplatin [cis-diammine dichloroplatinum (II)]-induced cytotoxicity and apoptosis in head and neck cancer cell lines by an unknown mechanism. We investigated the effect of cisplatin with and without BG on two targets of damage: DNA and the endoplasmic reticulum (ER). We chose three cancer cell lines to ascertain the mechanism of BG-enhanced cytotoxicity: SQ20b head and neck and SKOV-3x ovarian cancer cell lines, where BG enhanced cisplatin cytotoxicity, and A549 nonsmall cell lung cancer line, where BG did not enhance cisplatin cytotoxicity. All three lines had an increase in DNA damage when BG was added to cisplatin treatment, as evidenced by increased platination and phosphorylated histone H2AX formation. The increase in cisplatin-induced DNA damage after treatment with BG plus cisplatin is not sufficient to increase cytotoxicity or apoptosis in A549 cells. We evaluated the effect of cisplatin on the ER and observed increased caspase 12 cleavage in SQ20b and SKOV-3x cells, but not in A549 cells, after treatment with BG plus cisplatin versus cisplatin alone. Growth arrest and DNA damage inducible (GADD) 153, an ER stress-response gene, is up-regulated after treatment with BG plus cisplatin compared with cisplatin alone in SQ20b and SKOV-3x cells, but not in A549 cells. ER stress-induced apoptosis is an integral part of the mechanism by which BG enhances cisplatin. Inhibition of ER stress in the SQ20b cell line by salubrinal, an inhibitor of eIF2α dephosphorylation, or GADD153 small interfering RNA, abrogated BG-enhancement of cisplatin cytotoxicity and apoptosis through caspase 3 and 12 cleavage. These data indicate GADD153 up-regulation plays an important role in BG-enhanced cisplatin cytotoxicity and apoptosis.",
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