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Departments of 1 Pathology, 2 Urology, 3 Biostatistics, and 4 Surgery, and 5 The Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, Michigan
Requests for reprints: Celina G. Kleer, Department of Pathology, University of Michigan, 3510C MSRB1, 1150 West Medical Center Drive, Ann Arbor, MI 48109. Phone: 734-615-3448; Fax: 734-615-3441; E-mail: kleer{at}umich.edu.
| Abstract |
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| Introduction |
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By applying a two-stage Bayesian mixture modeling strategy, our group was able to develop a meta-signature predictive of disease-free survival in breast cancer patients (1). GATA binding protein 3 (GATA3), a transcriptional activator, emerged as one of the top genes with low expression in the meta-signature.
In breast cancer, high GATA3 mRNA levels are seen in the luminal A type, associated with estrogen receptor (ER) expression and with a favorable prognosis (25). Recently, Usary et al. (4) identified and characterized in detail somatic mutations of GATA3 in five ER-
-positive invasive breast cancers and in the ER-positive breast cancer cell line MCF-7 and suggested that loss of GATA3 may contribute to tumorigenesis in ER-positive breast cancers. Here, we show that GATA3 protein levels are strongly associated with the degree of differentiation of breast cancer and that low GATA3 protein expression is an independent predictor of tumor recurrence after treatment in breast cancer patients.
| Materials and Methods |
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Western blot analysis. Nine frozen invasive carcinomas of the breast were dissected following review of an H&E section to confirm the presence and location of the carcinoma in the block by a pathologist (C.G.K.). Protein extracts for Western blot analysis were prepared from these cancer tissues. In addition, four breast cell lines (MCF-7, MDA-MB-231, HME, and MCF-10A) were used. Standard immunoblot analysis was done using an anti-GATA3 mouse monoclonal antibody (sc-269, Santa Cruz Biotechnology, Inc., Santa Cruz, CA) at 1:250 dilution (4).
-Actin and ß-tubulin were used to control for equal loading.
Immunofluorescence and confocal microscopy. The breast tissue sections were deparaffinized in xylene. Slides were deparaffinized and blocked in PBS-Tween 20 with 5% normal donkey serum for 1 hour. A mixture of rabbit anti-E-cadherin antibody (LabVision Corp., Fremont, CA) and mouse anti-GATA3 antibody (Santa Cruz Biotechnology) was added to the slides at 1:50 and 1:100 dilutions, respectively, and incubated overnight at 4°C following standard immunofluorescence methods (12).
Breast sample collection and tissue microarray development. Breast tissue samples were obtained from the Surgical Pathology files at the University of Michigan with Institutional Review Board (IRB) approval. One hundred thirty-nine consecutive invasive breast carcinomas treated at our institution between 1987 and 1991 were reviewed (C.G.K.) and used to construct a TMA (n = 417 tissue microarray samples) using a manual arrayer as previously described (12). Each tumor was sampled in triplicate to account for tumor heterogeneity. Outcome information was obtained by chart review (M.S.S.) with IRB approval. The median duration of follow-up time was 8.9 years (range, 44 days-17 years). Clinicopathologic variables were assessed using well-established criteria (13).
Immunohistochemistry, digital image capture, and analysis. Immunohistochemistry was done on the TMA using standard biotin-avidin complex technique and a mouse monoclonal antibody against GATA3 (Santa Cruz Biotechnology) at 1:100 dilution as previously described (4). GATA3 was evaluated at least thrice for each microarray element and at least nine times for each tumor using a previously validated Web-based tool (TMA Profiler, University of Michigan, Ann Arbor, MI; ref. 14). GATA3 expression was scored blindly and independently by two surgical pathologists (C.G.K. and R.M.) as negative (score = 1), weak (2), moderate (3), and strong (4) on the basis of the intensity of staining and the percentage of tumor cells stained using a system that has been validated previously (15). The TMAs were previously stained for ER, progesterone receptor (PR), and HER-2/neu using well-described procedures (12, 15). The median value of all measurements from a patient was used for subsequent analysis. High GATA3 expression was defined as a median intensity of >2.5 and low GATA3 was defined as a median intensity of
2.5.
Statistical analyses. Statistical analyses were done using SAS (SAS Institute, Inc., Cary, NC) software by the biostatisticians in the study (R.S. and D.G.). GATA3 expression was dichotomized into low staining (median score
2.5) and high staining (median score > 2.5). No data-based optimization of the cut point was done. Associations between the GATA3 score and clinicopathologic features were assessed using
2 tests for 2 x 2 table analysis and Wilcoxon rank-sum test for 2 x n comparisons. Overall survival time and time to breast cancer specific mortality were calculated from the date of surgery until the subjects' date of death or date of death due to breast cancer, respectively. Patients experiencing competing events were censored at the date of the competing event. Treatment failures included local recurrence and regional or distant metastases. Patients not experiencing failure events were censored on their last date of follow-up or date of death. Univariate associations were assessed using the log-rank test and the product-limit method of Kaplan and Meier. The Cox proportional hazards model was used to determine the best multivariate model of disease applied to variables including GATA3 protein expression, histologic grade, tumor size, lymph node status, angiolymphatic invasion, and ER, PR, and HER2 status. Associations with disease-free survival and overall survival were assessed for each variable. To determine the influence of multiple variables simultaneously, a multivariate Cox proportional hazards model was applied to the clinical variables and GATA3. Wald's test was used to determine statistical significance in the Cox models.
| Results |
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As expected, at the univariate level, lymph node status, tumor size, and histologic tumor grade were associated with disease-specific and overall survival (Table 1). PR was inversely associated with outcome. We found a strong association between GATA3 and survival. Low GATA3 protein levels were associated with a shorter disease-free interval and a high probability of death (Fig. 3A and B). The 10-year disease-free survival for patients with invasive cancers expressing low GATA3 levels was 55% and, by contrast, for high levels of GATA3, 84% (log-rank P = 0.005). The hazard ratio of metastasis or recurrence according to the GATA3 status was 0.31 [95% confidence interval (95% CI), 0.13-0.74; P = 0.009]. Furthermore, low GATA3 expression was associated with disease-specific survival in patients with lymph nodenegative disease (log-rank P = 0.02; Fig. 3C).
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The best multivariable model predictive of disease-specific survival showed that low GATA3 was a strong independent predictor of outcome providing survival information above other prognostic features, with a hazard ratio of 0.12 (95% CI, 0.01-1.01; P = 0.05; Table 1). The risk of recurrence for GATA3 low cases was eight times higher than that of the risk for GATA3 high cases.
| Discussion |
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The promising prognostic utility of GATA3 in breast cancer patients has been suggested by analyses of published breast tumor microarray data (4, 16, 17). We provide a validation of those results derived from individual data sets. By doing a meta-analysis, we unified disparate gene expression data on a common probability scale, thus providing a robust interstudy validation of GATA3 expression as a prognostic marker. Our results further strengthen the value of the mixture model based data transformation in the identification and cross-validation of biomarkers across cDNA data sets which are based on different experimental platforms.
We found that GATA3 expression was strongly associated with ER expression and with the histologic grade of the carcinomas, a measure of differentiation. In DNA microarray analyses, GATA3 was associated with the expression of ER and of a subset of genes important for breast luminal cell differentiation including LIV-1, RERG, and TFF3 (24). Our data support these observations and suggest a role for GATA3 in maintaining a differentiated state in breast cells. We found a strong association between GATA3 and ER expression at the mRNA and protein levels. Recently, Usary et al. (4) reported a strong association between GATA3 and ER in normal breast luminal epithelial cells and discovered mutations of GATA3 near the highly conserved second zinc-finger domain required for DNA binding in breast cancers and in the MCF-7 breast cancer cell line, which suggested that GATA3 is expressed in normal mammary epithelium and that decreased expression due to mutation or deletion may contribute to breast cancer development.
Despite genomic coexpression of ER and GATA3 transcription factors in breast cancer, estrogens do not regulate GATA3 (3). Although the gene for ER is not induced by GATA3, it has been suggested that GATA3 variants may contribute to tumorigenesis in ER-positive tumors (4). In our study, we identified a group of ER-positive invasive carcinomas that have low GATA3 protein levels. Furthermore, GATA3 was able to uncover a group of ER-positive invasive carcinomas with worse clinical outcome who developed tumor recurrence and/or metastases independently of hormonal treatment, which may have clinical implications. Future studies will test the model developed in this study to confirm these initial observations.
Furthermore, GATA3 protein levels were able to discern which node-negative patients develop tumor recurrence or metastases from those who do not. These results suggest that detection of GATA3 protein may be useful in supplying additional power to delineate prognosis in node-negative breast cancer patients. In the future, this may pave the way to tailor the aggressiveness of therapies to molecular profiles that include GATA3.
By interrogating 29 cancer microarray data sets for evidence of differential expression of GATA3 transcript in benign and malignant tissues using Oncomine 2.0 (18), GATA3 was elevated in several carcinomas including lung (P = 0.002), prostate (P = 0.003), pancreas (P = 0.046), liver (P < 0.0001), endometrium (P = 0.004), adenoid cystic carcinoma of salivary gland (P < 0.0001), and diffuse large B-cell lymphomas (P = 0.007). These microarray studies suggest a role of GATA3 in several human tumor types.
In summary, we show that GATA3 is a promising novel prognostic biomarker in breast cancer. Our retrospective studies suggest that GATA3 levels may be used to identify patients with ER-positive and lymph nodenegative breast cancer with a more aggressive phenotype, thereby enhancing our prognostic knowledge. Although our results are promising, they need to be validated in relationship to outcome in the context of controlled clinical trials. If confirmed, application of GATA3 immunohistochemical analysis will be technically straightforward and clinically useful.
| Acknowledgments |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
We thank Dr. Daniel Hayes (University of Michigan, Ann Arbor, MI) for review of this manuscript and helpful suggestions, Srilakshmi Bhagavathula for assistance in preparation of data, Nancy McAnsh and Michele LeBlanc for immunohistochemical support, and Scott A. Tomlins for critical review of figures.
| Footnotes |
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Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/).
Received 7/20/05. Revised 9/20/05. Accepted 10/ 3/05.
| References |
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-methylacyl-CoA racemase protein expression is associated with the degree of differentiation in breast cancer using quantitative image analysis. Cancer Epidemiol Biomarkers Prev 2005;14:141823.This article has been cited by other articles:
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