Relationship between expression of topoisomerase II isoforms and intrinsic sensitivity to topoisomerase II inhibitors in breast cancer cell lines

• Published in: British journal of cancer Vol. 72; no. 6; pp. 1454 - 1461
• Main Authors: HOULBROOK, S, ADDISON, C. M, DAVIES, S. L, CARMICHAEL, J, STRATFORD, I. J, HARRIS, A. L, HICKSON, I. D
• Format: Journal Article
• Language: English
• Published: Basingstoke Nature Publishing Group 01-12-1995
• Subjects: Antibody Specificity; Antigens, Neoplasm; Antineoplastic agents; Antineoplastic Agents - pharmacology; Biological and medical sciences; Breast Neoplasms - drug therapy; Breast Neoplasms - enzymology; Chemotherapy, Adjuvant; DNA Topoisomerases, Type II - biosynthesis; DNA-Binding Proteins; Drug Screening Assays, Antitumor; Enzyme Inhibitors - pharmacology; General aspects; Humans; Isoenzymes - antagonists & inhibitors; Isoenzymes - biosynthesis; Medical sciences; Pharmacology. Drug treatments; RNA, Messenger - metabolism; Topoisomerase II Inhibitors; Tumor Cells, Cultured; Adenocarcinoma; Antineoplastic agent; Human; DNA topoisomerase (ATP-hydrolysing); Molecular form; Carcinoma; Enzyme; Isozyme; Acridine derivatives; Enzyme inhibitor; Malignant tumor; Gene expression; In vitro; Mammary gland diseases; Sensitivity; Isomerases; Established cell line; Anthracyclins; Mammary gland
• ISSN: 0007-0920; 1532-1827
• DOI: 10.1038/bjc.1995.529

Topoisomerase II is a key target for many anti-cancer drugs used to treat breast cancer. In human cells there are two closely related, but differentially expressed, topoisomerase II isoforms, designated topoisomerase II alpha and beta. Here, we report the production of a new polyclonal antibody raised against a fragment of the C-terminal domain of the 180 kDa form of topoisomerase II (the beta isoform), which does not cross-react with the 170 kDa form (the alpha isoform). Using this antibody, together with a polyclonal antibody specific for the 170 kDa isoform of topoisomerase II, we have examined the relationship between the sensitivity of a panel of human breast cancer cell lines to different classes of topoisomerase II inhibitors and cellular levels of the topoisomerase II alpha and beta proteins. We found that sensitivity to amsacrine showed a correlation with the level of expression of topoisomerase II alpha protein, and that sensitivity to etoposide showed a similar correlation with the level of expression of topoisomerase II beta protein. There was also a relationship between sensitivity of these cell lines to mitoxantrone and the cellular level of both isoforms of topoisomerase II. No relationship was found between the level of mRNA for topoisomerase II alpha or beta, and either sensitivity of breast cancer cell lines to topoisomerase II inhibitors or the level of topoisomerase II protein expression.