Topotecan-induced alterations in the amount and stability of human DNA topoisomerase I in solid tumor cell lines.
BACKGROUND
Human DNA topoisomerase I (topo 1) is an essential nuclear enzyme involved in vital cellular processes and the sole target of antitumor drugs of the camptothecin (CPT) family. The CPT derivative topotecan (Tpt, Hycamtin) is currently used in clinic, its effectiveness varying considerably for different types of cancer. The purpose of this study was to compare time- and dose-dependent cellular responses to Tpt in terms of alterations in the amount and stability of topo 1 in lung adenocarcinoma (A-549), ovarian adenocarcinoma (CaOv-3), colorectal adenocarcinoma (HT-29) and breast adenocarcinoma (MCF-7) cell lines.


METHODS
Western blot analysis of the time-dependent redistribution of a full-size topo 1 and its proteolytical fragments was performed after Tpt treatment for 1 h at concentrations 10-fold or 100-fold higher than the Tpt IC50 for the respective cell lines.


RESULTS
Tpt treatment of the CaOv-3 cell line produced a substantial time-dependent decrease in the amount of topo 1 immunoprotein. Conversely, the MCF7 cell line did not exhibit a topo 1-associated response to the Tpt treatment. Strong but different time- and dose-dependent topo 1 down-regulation effects were observed in the HT-29 and A-549 cell lines.


CONCLUSIONS
The data obtained indicate that Tpt-induced time- and dose-dependent effects on the amount and stability of topo 1 are involved in the mechanisms of Tpt activity against different solid tumor cell lines.
EA no3306 Interactions Cellulaires et Moléculaires en Cancérologie, IFR no53 Biomolécules, UFR de Pharmacie, Université de Reims Champagne-Ardenne, 51100 Reims, France.
Jérome
J
Devy
Richard
R
Wargnier
Michel
M
Pluot
Igor
I
Nabiev
Alyona
A
Sukhanova
D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability / Q000187:drug effects; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000201:enzymology; D010446:Peptide Fragments / Q000378:metabolism; D059004:Topoisomerase I Inhibitors; D019772:Topotecan / Q000494:pharmacology*
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D059004:Topoisomerase I Inhibitors; D019772:Topotecan; D004264:DNA Topoisomerases, Type I