TY - JOUR
T1 - Acquired alkylating drug resistance of a human ovarian carcinoma cell line is unaffected by altered levels of pro- and anti-apoptotic proteins
AU - Roy, Gargi
AU - Horton, Julie K.
AU - Roy, Rabindra
AU - Denning, Timothy
AU - Mitra, Sankar
AU - Boldogh, Istvan
N1 - Funding Information:
We are grateful to Drs CB Thompson, S Korsmeyer, K Scanlon, MP Thelen, and D Chen for cell lines, expression plasmids and antibodies, and Ms Trisha Castranio for technical assistance. We thank Dr D Konkel for editing the manuscript and Ms W Smith for expert secretarial assistance. This research was supported by US Public Health Service Grant ES07572, NIEHS Center Grant ES06676, and by a UTMB Sealy Foundation Development Grant.
PY - 2000/1/6
Y1 - 2000/1/6
N2 - In a systematic study to elucidate the involvement of pro-and anti-apoptotic proteins in alkylating drug resistance of tumor cells, we utilized the A2780(100) line, that was selected by repeated exposure of A2780 cell line (human ovarian carcinoma line) to chlorambucil (CBL). A2780(100) was 5-10-fold more resistant to nitrogen mustards (IC50 of 50-60 μM) and other DNA crosslinking agents, e.g., cisplatin, and also to DNA topoisomerase inhibitor etoposide (ETO) than A2780. CBL (125 μM) induced extensive apoptosis in A2780 associated with mitochondrial damage but not in A2780(100). No significant differences were observed between A2780 and A2780(100) cells in the basal levels, or the enhanced levels in some cases after CBL treatment, of DNA repair proteins involved in repair of alkyl base adducts or in repair of DNA crosslinks or double strand break repair. However, the basal levels of anti-apoptotic proteins Bcl-x(L) and Mcl-1 were 4-8-fold higher in A2780(100) than in A2780 neither of which expressed Bcl-2. In contrast, the levels of pro-apoptotic Bax and Bak were 3-5-fold higher in the CBL-treated A2780 but not in A2780(100). ETO (5 μM) induced apoptosis in A2780 without altering the levels of Bax and Bak in these cells. At the same time, neither overexpression of Bcl-x(L), in A2780, nor its antisense expression in A2780(100), and nor overexpression of Bax in A2780(100), significantly affected drug sensitivity of either line. Our results suggest that a change in an early step in DNA damage processing which affects intracellular signaling, such as enhanced DNA double-strand break repair, could be the primary cause for development of resistance in A2780(100) cells to drugs which induce DNA crosslinks or double strand-breaks.
AB - In a systematic study to elucidate the involvement of pro-and anti-apoptotic proteins in alkylating drug resistance of tumor cells, we utilized the A2780(100) line, that was selected by repeated exposure of A2780 cell line (human ovarian carcinoma line) to chlorambucil (CBL). A2780(100) was 5-10-fold more resistant to nitrogen mustards (IC50 of 50-60 μM) and other DNA crosslinking agents, e.g., cisplatin, and also to DNA topoisomerase inhibitor etoposide (ETO) than A2780. CBL (125 μM) induced extensive apoptosis in A2780 associated with mitochondrial damage but not in A2780(100). No significant differences were observed between A2780 and A2780(100) cells in the basal levels, or the enhanced levels in some cases after CBL treatment, of DNA repair proteins involved in repair of alkyl base adducts or in repair of DNA crosslinks or double strand break repair. However, the basal levels of anti-apoptotic proteins Bcl-x(L) and Mcl-1 were 4-8-fold higher in A2780(100) than in A2780 neither of which expressed Bcl-2. In contrast, the levels of pro-apoptotic Bax and Bak were 3-5-fold higher in the CBL-treated A2780 but not in A2780(100). ETO (5 μM) induced apoptosis in A2780 without altering the levels of Bax and Bak in these cells. At the same time, neither overexpression of Bcl-x(L), in A2780, nor its antisense expression in A2780(100), and nor overexpression of Bax in A2780(100), significantly affected drug sensitivity of either line. Our results suggest that a change in an early step in DNA damage processing which affects intracellular signaling, such as enhanced DNA double-strand break repair, could be the primary cause for development of resistance in A2780(100) cells to drugs which induce DNA crosslinks or double strand-breaks.
KW - Alkylating drugs
KW - Apoptosis
KW - Bcl-2 family
KW - Drug resistance
KW - Pro- and anti-apoptotic proteins
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U2 - 10.1038/sj.onc.1203318
DO - 10.1038/sj.onc.1203318
M3 - Article
C2 - 10644989
AN - SCOPUS:0034610802
SN - 0950-9232
VL - 19
SP - 141
EP - 150
JO - Oncogene
JF - Oncogene
IS - 1
ER -