Prognostic Relevance of AGR2 Expression in Breast Cancer
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Imaging, Diagnosis, Prognosis Prognostic Relevance of AGR2 Expression in Breast Cancer Florian Rudolf Fritzsche,1Edgar Dahl,3 Stefan Pahl,1Mick Burkhardt,1Jun Luo,4 Empar Mayordomo,1Tserenchunt Gansukh,1Anja Dankof,1Ruth Knuechel,3 Carsten Denkert,1Klaus-Ju« rgen Winzer,2 Manfred Dietel,1andGlenKristiansen1, 2 Abstract Purpose:We aimed to evaluate the expression of the human anterior gradient-2 (AGR2)inbreast cancer on RNA and protein level and to correlate it with clinicopathologic data, including patient survival. Experimental Design: AGR2 mRNA expression was assessed by reverse transcription-PCR in 25 breast cancer samples and normal tissues. A polyclonal rabbit AGR antiserum was used for immunohistochemistry on155clinicopathologically characterized cases. Statistical analyses were applied to test for prognostic and diagnostic associations. Results: Immunohistochemical detection of AGR2 was statistically significantly associated with positive estrogen receptor status and lower tumor grade. AGR2-positive tumors showed signifi- cantly longer overall survival times in univariate analyses. For the subgroup of nodal-negative tumors, an independent prognostic value of AGR2 was found. Conclusions: The expression of AGR2 in breast cancer is strongly associated with markers of tumor differentiation (estrogen receptor positivity, lower tumor grade). A prognostic effect of AGR2 for overall survival could be shown, which became independently significant for the group of nodal-negative tumors. Despite considerable diagnostic and therapeutic advances in entiation and expression of neural marker genes in a fibroblast the treatment of breast cancer in recent years, there is still an growth factor–dependent way (11). AGR2 has been shown urgent need for further molecular markers to provide the previously to be coexpressed with estrogen receptor (ER) in clinician with useful information concerning patient prognosis breast cancer cell lines (9), suggesting involvement of AGR2 in and possible therapeutic options. Kallikrein 5 (1), urokinase the tumor biology of hormonally responsive breast cancers. plasminogen activator, its inhibitor (2), tissue inhibitor of This is in agreement with the finding that an antiestrogen- metalloproteinases 1 (3), Ep-CAM (4), osteopontin (5), CD24 resistant derivative of the human T47D breast cancer cell line (6), and SFRP1 (7) are just a few examples of a growing list of that has lost ER expression also has a strongly reduced AGR2 potentially useful prognostic markers in breast cancer. We and expression (12). The estrogen-dependent expression of AGR2 others recently described up-regulation of the androgen- in breast cancer may be regulated by the four putative estrogen inducible gene anterior gradient-2 (AGR2) in prostate cancer response elements present in the AGR2 promoter (12). (6, 8). AGR2, which is also known as HAG-2 (9) or Gob-4 Although the Xenopus XAG-2 protein was shown to be secreted (10), is the human orthologue of the secreted Xenopus laevis (11), it is presently not clear whether the human AGR2 protein AGR protein XAG-2. It has a putative role in ectodermal is secreted in normal and malignant breast tissue as well (13). patterning of the frog embryo and is itself regulated by a Persson et al. (14) have shown by Basic Local Alignment number of fundamental embryonic molecules like noggin and Search Tool analysis (15) that AGR2 may represent a novel chordin (11). XAG-2 expression induces cement gland differ- member of the protein disulfide isomerase family. Protein disulfide isomerases are oxidoreductases of the endoplasmic reticulum involved in protein maturation in the endoplasmic reticulum (16). Authors’ Affiliations: 1Institute of Pathology and 2Breast Centre, Charite¤ , 3 In a recent study, Fletcher et al. showed immunohisto- Universita« tsmedizin Berlin, Berlin, Germany; Institute of Pathology, University chemical expression of AGR2 in 83% (n = 58) of breast cancer Hospital of the Rheinisch-Westfa« lische Technische Hochschule Aachen, Aachen, Germany; and 4Department of Urology, Johns Hopkins Medical Institutions, cases using a tissue microarray (17). They also found a Baltimore, Maryland significant correlation with ER expression and an inverse Received 9/20/05; revised 1/6/06; accepted 1/11/06. correlation with epidermal growth factor receptor expression. The costs of publication of this article were defrayed in part by the payment of page However, no significant association between AGR2 expression charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. and tumor grade, patient age, and presence of axillary lymph Note: F. R. Fritzsche, E. Dahl, and S. Pahl contributed equally to this work. node metastasis could be shown. The estrogen responsiveness Requests for reprints: Glen Kristiansen, Institut fu« r Pathologie, Charite¤ , of AGR2 was recently confirmed by Liu et al. (13) as the Universita« tsmedizin Berlin, Schumannstrasse 20-21,10117 Berlin, Germany. Phone: AGR2 mRNA expression in MCF-7 breast cancer cells increased 49-30-450-536145; Fax: 49-30-450-563945; E-mail: glen.kristiansen@ >7-fold in the presence of estrogen. More importantly, their charite.de. F 2006 American Association for Cancer Research. study showed that AGR2 can induce a metastatic pheno- doi:10.1158/1078-0432.CCR-05-2057 type in vivo. AGR2-transfected rat mammary cells (Rama 37) Clin Cancer Res 2006;12(6) March 15, 2006 1728 www.aacrjournals.org Downloaded from clincancerres.aacrjournals.org on September 27, 2021. © 2006 American Association for Cancer Research. AGR Expression in Breast Cancer in separate dots (19). An AGR2-specific cDNA fragment (EcoRI/NotI fragment of IMAGE cDNA clone with accession no. AA625485) was radiolabeled using a Megaprime labeling kit (Amersham Biosciences, Braunschweig, Germany), hybridized overnight at 68jC using Expres- sHyb Hybridization Solution (Clontech), washed, and exposed to Kodak XAR-5 X-ray film with an intensifying screen (Eastman Kodak Co., Rochester, NY). RNA preparation from paraffin-embedded tissue specimens. Archival formalin-fixed, paraffin-embedded tissue from 25 well-characterized representative (44% pT1, 48% pN0, 40% G1-G2) breast cancer specimens and 16 normal breast tissues, both from the archives of the Institute of Pathology of the Rheinisch-Westfa¨lische Technische Hochschule Aachen, were used. For each formalin-fixed, paraffin- embedded tissue specimen, six 4-Am-thick tissue sections were cut with a microtome (Leica Microsystems, Bensheim, Germany) and trans- ferred to a water bath filled with diethylpyrocarbonate-treated water. Sections were mounted on standard glass slides and dried for 1 hour at 60jC. Sections were deparaffinized and rehydrated as follows: 2 Â 15 minutes in xylole; 2 Â 15 minutes in 100% ethanol; and short rinses in 96%, 70%, and 50% ethanol followed by immersion in distilled water. Tissue material was transferred to a microcentrifuge tube and RNA was extracted according to the Trizol protocol supplied by the manufacturer (Life Technologies, Mannheim, Germany). cDNA was Fig. 1. Western blot analysis of AGR2 expression inhuman prostate cancer cell lines. PC3 cells (A) strongly express AGR2 (positive control), whereas CWR22Rv1cells synthesized according to the protocol supplied with the Clontech RT- (B) do not express detectable amounts of AGR2 (negative control). h-Actin was for-PCR-kit. used as loading control. Quantitative reverse transcription-PCR. AGR2 mRNA expression was analyzed using intron-spanning primers on the LightCycler system (Roche Diagnostics, Mannheim, Germany). Glyceraldehyde-3-phosphate injected in the mammary fat pads of syngenic rats induced a dehydrogenase (GAPDH) mRNA was used as reference to obtain relative high incidence of lung metastases. Because the incidence of expression values. Primers used in this study are presented in Table 1. primary tumors in this rat model was not increased, it can be Real-time reverse transcription-PCR (RT-PCR) was carried out with Fast concluded that AGR2 expression may be associated with Start DNA master hybridization probes (Roche Diagnostics). The metastasis but not with initiation of ER-positive tumors (13). conditions were as follows: initial denaturation in one cycle of 15 The study of Liu et al. (13) also analyzed human breast minutes at 95jC, followed by 40 cycles at 95jC for 20 seconds, 60jC tumors (n = 44) immunohistochemically and found a for 20 seconds, and 72jC for 30 seconds. Gene expression was significant correlation between ERa positivity and AGR2 quantified by the comparative CT method (20). expression; however, no correlation to patient survival was Patients. For immunohistochemistry, our study included 155 patients with breast cancer diagnosed at the Institute of Pathology, analyzed. University Hospital Charite´, Berlin, Germany, between 1991 and In our study, we aimed to investigate the expression of AGR2 1997. Patient age at the time of diagnosis ranged from 30 to 81 years immunohistochemically in a large breast cancer collective with a mean of 59 years. Clinical follow-up data, including overall (n = 155) and to evaluate prognostic properties by correlation survival and disease-free survival, were available for all cases. The with clinicopathologic variables. Furthermore, we have careful- median observation time for overall survival was 75 months for ly analyzed the AGR2 mRNA expression by real-time PCR in patients still alive at the time of analysis, and ranged from 1 to 162 ERa-positive