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Topoisomerase II Expression in Breast Cancer

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Topoisomerase II Expression in Breast Cancer Topoisomerase II␣ Expression in Breast Cancer: Correlation with Outcome Variables Peter L. Depowski, M.D., Seth I. Rosenthal, M.D., Thomas P. Brien, M.D., Scott Stylos, M.D., Rebecca L. Johnson, M.D., Jeffrey S. Ross, M.D. Department of Pathology, Albany Medical College (PLD, SIR, TPB, JSR), Albany, New York, and Berkshire Medical Center (SS, RLJ), Pittsfield, Massachusetts iate analysis, stage (p < .0001), lymph node metas- all (002. ؍ Topoisomerase II␣ (topo II␣) plays a key role in tasis (p < .0001), and tumor grade (p DNA replication and is a target for multiple chemo- independently predicted disease-related death. therapeutic agents. In breast cancer, topo II expres- Increased topo II expression is associated with an sion has been linked to cell proliferation and HER2/ aggressive form of breast cancer featuring HER-2 neu protein overexpression. However, its amp and predicts disease-related death, lymph relationship with outcome variables is not well es- node metastasis, and advanced tumor stage. tablished. Formalin-fixed, paraffin-embedded primary KEY WORDS: Breast cancer, HER-2/neu, MIB-1, breast cancers from 184 women (mean age, 60 Stage, Survival, Topoisomerase II␣ years) were stained for topo II by automated immu- Mod Pathol 2000;13(5):542–547 nohistochemistry. A topo II expression index (TI) was determined by counting the number of positive Topoisomerase II␣ (topo II␣) is a component of the cells per high-power field and calculating an overall DNA machinery that is intricately involved at many mean number of positive cells per high-power field. levels of DNA metabolism (1–3). Its primary func- Tumors with a TI of more than 1 were considered tion is to alter DNA topology from its storage (su- positive, and those with a TI of 1 or less were con- percoiled) form to a more exposed (partially un- sidered negative. A cell proliferation index was de- coiled) form by inducing single-strand DNA breaks termined by automated immunohistochemistry us- and simultaneously passing another intact double ing the MIB-1 antibody in an identical technique. helix through the gap (4–5). HER-2/neu gene amplification (HER-2 amp) was The anthracycline class of antitumor cytotoxic determined by automated fluorescence in situ hy- drugs is topoisomerase poisons specifically target- bridization using the Ventana unique sequence ing topo II␣ (2, 6–7). These drugs create a cleavable probe. complex including drug, topo II␣, and DNA strand. Fifty-nine (32%) of the tumors had a TI greater It is hypothesized that the cleavable complex dam- than 1. On univariate analysis, increased topo II ages the DNA, causing toxicity, and may induce expression correlated with decreased patient sur- apoptosis in proliferating tumor cells (8–10). From ؍ ؍ vival (p .001), advanced tumor stage (p .034), most in vitro analyses, it has been shown that low ؍ lymph node metastasis (p .018), and HER-2 amp levels of topo II␣ expression in cancer cells are ؍ (p .016). Tumor stage (p < .0001), node-positive associated with drug resistance, whereas high levels ؍ status (p < .0001), tumor grade (p .025), HER-2 indicate sensitivity (11–13). However, in one study, ؍ amp (p < .0001), and MIB-1 overexpression (p no correlation between the level of topo II␣ expres- .002) also correlated with survival on univariate sion and drug sensitivity in breast cancer cell lines analysis. Topo II expression did not correlate with was found (14), and recent reports using paraffin- tumor size, grade, estrogen receptor/progesterone embedded breast cancer tissues failed to find asso- receptor status, or disease recurrence. On multivar- ciations between topo II␣ expression and drug sen- sitivity (15). Exclusive of topo II␣’s potential role as a target Copyright © 2000 by The United States and Canadian Academy of Pathology, Inc. for anticancer drugs, few studies have analyzed it as VOL. 13, NO. 5, P. 542, 2000 Printed in the U.S.A. Date of acceptance: October 26, 1999. a potential prognostic marker in breast cancer. Of Address reprint requests to: Jeffrey S. Ross, M.D., Department of Pathol- the limited data available, a common finding has ogy, Mail Code 81, Albany Medical College, 47 New Scotland Avenue, Albany, NY 12208. e-mail: [email protected]; fax: 518-262- been correlation with known proliferation markers 8092. such as MIB-1 immunostaining and tumor S phase 542 fraction (16–18). These findings support the role of able data on tumor size. Hematoxylin and eosin– topo II␣ as a proliferation marker in breast cancer. stained slides from each case were reviewed, and An additional finding in some studies has been the tumors were graded according to the modified coexpression of both topo II␣ and HER-2/neu on- Bloom Richardson grading system (26). The tumors coprotein, a known poor prognostic indicator (19– were separated into high grade (scores of 8 or 9) 24). Of the few studies that evaluated this associa- and non–high grade (scores of Ͻ8). There were 95 tion, two recent studies of 230 and 55 breast (52%) lymph node–negative and 89 (48%) lymph cancers, respectively, reported significant correla- node–positive cases. A total of 117 patients had tion between HER-2/neu oncoprotein overexpres- available ER status data, and 101 patients had avail- sion in tumors with increased topo II␣ expression. able PR status data. There were 107 cases with However, in a relatively small study of 30 breast available HER-2/neu gene amplification (HER-2 cancers by Lynch et al. (15), no association between amp) data. All 184 patients were included in the HER-2/neu oncoprotein overexpression and a high survival analysis. topo II␣ index was identified. The correlation of topo II␣ expression with other Immunohistochemistry known outcome variables in breast cancer has been inconsistent. Studies have shown a significant cor- Immunohistochemical staining for topo II was relation of topo II␣ expression with lymph node performed on the Ventana ES automated immuno- metastases, tumor grade, tumor size, and distant histochemistry (IHC) instrument (Ventana Medical metastases (25) and with negative hormone recep- Systems, Inc., Tucson, AZ) with an indirect biotin ␮ tor status, high grade, and DNA aneuploidy (16, 18). avidin system on 5 m formalin-fixed, paraffin- Other studies have found the association of topo II␣ embedded sections from a representative block in expression with cell proliferation markers only (15, each case. Tissue blocks were stored in ambient 17). conditions in the pathology departments of both In the following study of 184 primary breast can- institutions for 3 to 18 years before IHC procedures. cers, topo II␣ expression was compared with tumor All blocks were cut immediately before IHC. The stage, lymph node metastases, tumor grade, tumor antigenic determinant sites were unmasked with size, estrogen receptor (ER) status, progesterone 0.01 M sodium citrate solution in association with receptor (PR) status, disease recurrence, survival, microwave irradiation at maximum power for 15 HER-2/neu gene status, and MIB-1 expression by min for each antibody (27). The slides were subse- univariate and multivariate analysis. quently incubated with a biotinylated universal sec- ondary antibody and in avidin peroxidase label (Ventana). After the development of color with dia- MATERIALS AND METHODS minobenzidine substrate, the slides were counter- stained with hematoxylin. Positive control slides Patients using non-neoplastic human tonsil were included The clinical records and tissue blocks were ob- with every batch. To confirm the specificity of the tained from 160 randomly selected patients who primary antibody, negative control slides were run underwent either mastectomy or local excision for using an isotype-matched mouse IgG1, (Sigma, St. infiltrating ductal carcinoma at the Albany Medical Louis, MO) at the same concentration as that of the Center between 1980 and 1985. The clinical records primary antibody. The immunochemicals, incuba- and tissue blocks were also obtained from 24 pa- tion times, positive control specimens, and final tients who underwent mastectomy for infiltrating antibody concentration/dilutions are summarized ductal carcinoma at the Berkshire Medical Center in Table 1. between 1980 and 1982. The tumors were staged pathologically according to American Joint Com- mittee on Cancer criteria using the TNM classifica- Staining Interpretation tion scheme. There were 55 (30%) Stage 1, 90 (50%) Assessment of topo II staining was performed Stage 2, 15 (8%) Stage 3, and 21 (12%) Stage 4 cases; without prior knowledge of patient clinical patho- 3 tumors were not staged because of lack of avail- logic parameters. The staining was uniformly dis- TABLE 1. Immunohistochemical Primary Antibodies Positive Control Final Antibody Primary Antibody Antibody Source Clone Specimens Concentration Incubation Monoclonal Antihuman Topo Novocastra Laboratories, Ltd., 3F6 Non-neoplastic Diluted 1:20 32 min @ 41° C II␣, IgG Newcastle, UK human tonsil Monoclonal Antihuman MIB- Ventana Medical Systems, MM1 Non-neoplastic 8 ␮g/mL 32 min @ 41° C 1, mouse IgG Tucson, AZ human tonsil Topoisomerase in Breast Cancer (P.L. Depowski et al.) 543 tributed within the nuclei. No cytoplasmic or mem- for the HER-2/neu gene when a group of 20 cells brane staining was observed. A topo II␣ staining featuring a mean of five or more signals per cell index (TI) was established by visual quantitation at could be identified (24, 28). 400ϫ magnification (surface area of 0.2 mm2). Briefly, the index was determined by counting the Statistical Analysis number of positive cells per high-power field (HPF: field diameter, 0.50 mm, area, 0.20 mm2). An overall Statistical comparisons were carried out with the mean number of positive cells per HPF was calcu- STATA software (Computing Resource Center, ␹2 lated. Tumors with a TI of more than 1 (increased Santa Monica, CA) using the test to determine expression) were considered positive, whereas the significance of the association between differ- those with a TI of 1 or less were considered nega- ent variables.
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