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Oncology, Immunology and Surgery, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-ku, Nagoya 467-8601, Japan¹ Breast and Endocrine Surgery, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan

(Correspondence should be addressed to H Yamashita; Email: hirokoy{at}med.nagoya-cu.ac.jp)

	Abstract

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Endocrine therapy has become the most important treatment option for women with estrogen receptor (ER)-positive breast cancer. Urgently needed are prognostic assays that can identify those who need additional adjuvant therapy, such as signal transduction inhibitors or chemotherapy, for ER-positive early breast cancer. We examined phosphorylation of ER serine (Ser) 118, ER Ser167, p44/42 mitogen-activated protein kinase (MAPK), and Akt and expression of progesterone receptor, amplified in breast cancer 1 (AIB1), human epidermal growth factor receptor 2 (HER2), p53, and Ki67 in ER-positive breast cancers by immunohistochemistry, and analyzed their significance for prognosis. Phosphorylation levels of ER Ser118, ER Ser167, MAPK, and Akt were positively correlated. AIB1 expression was significantly associated with phosphorylation of ER Ser118, MAPK, and Akt, and HER2 expression. Low phosphorylation of ER Ser118 and high phosphorylation of ER Ser167 were associated with significantly improved disease-free (P=0.0003 and P=0.0002 respectively) and overall survival (P=0.0007 and P=0.0016 respectively) in multivariate analyses. Our data suggest that phosphorylation of ER Ser118 and ER Ser167 affects survival in ER-positive breast cancer and could be helpful in distinguishing patients who are likely to benefit from endocrine therapy alone from those who are not.

	Introduction

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Endocrine therapy has become the most important treatment option for women with estrogen receptor (ER)-positive breast cancer. Nevertheless, many breast cancer patients with tumors expressing high levels of ER are unresponsive to endocrine therapy, and all patients with advanced disease eventually develop resistance to the therapy. The potential mechanisms behind this intrinsic or acquired endocrine resistance involve ER-coregulatory proteins and crosstalk between the ER pathway and other growth factor signaling networks (Schiff et al. 2003, Osborne & Schiff 2005). An understanding of the molecular mechanisms that modulate the activity of the estrogen-signaling network has enabled new ways of overcoming endocrine resistance to be developed. An urgent issue is the discovery of prognostic methods to identify those patients who need additional adjuvant therapy, such as signal transduction inhibitors or chemotherapy, for ER-positive early breast cancer (Johnston et al. 2003, Ellis 2004).

ER is phosphorylated on multiple amino acid residues (Lannigan 2003). In general, phosphorylation of serine residues in the activation function 1 (AF-1) domain of ER appears to influence the recruitment of coactivators, resulting in enhanced ER-mediated transcription. It has been reported that ER was significantly phosphorylated on Ser118 in response to either estradiol binding or the activation of the mitogen-activated protein kinase (MAPK) pathway, while Ser167 is phosphorylated by Akt, Rsk, and casein kinase II as well as MAPK (Arnold et al. 1994, Kato et al. 1995, Joel et al. 1998, Campbell et al. 2001, Clark et al. 2001). Murphy et al. (2004a) reported that in 45 human breast tumor biopsies, phosphorylation of ER Ser118 correlated with active MAPK. Because MAPK is located downstream of human epidermal growth factor receptor 2 (HER2), it is possible that phosphorylation of ER Ser118 is in part caused by HER2–MAPK signaling in breast cancer. On the other hand, phosphorylation of ER Ser167 seems to be controlled by different mechanisms.

We previously analyzed phosphorylation of Ser118 and Ser167 of ER using immunohistochemistry (IHC) in primary breast tumor specimens from 75 metastatic breast cancer patients who received first-line treatment with endocrine therapy on relapse (Yamashita et al. 2005). Our results indicated that patients whose primary breast tumors showed high phosphorylation of ER Ser167, but not ER Ser118, responded significantly to endocrine therapy and had a better survival than other patients, suggesting that phosphorylation of ER Ser167 frequently occurs via estrogen-dependent signaling in human breast cancer.

Amplified in breast cancer 1 (AIB1) is a coactivator of ER, which is phosphorylated by MAPK that has been activated by signaling from epidermal growth factor receptor (EGFR) or HER2 (Font de Mora & Brown 2000). It has been reported that tamoxifen behaves as an estrogen agonist in breast cancer cells that express high levels of AIB1 and HER2, resulting in de novo resistance (Shou et al. 2004) and that high AIB1 expression in patients who received tamoxifen adjuvant therapy was associated with inferior disease-free survival (Osborne et al. 2003).

In this study, we examined phosphorylation of ER Ser118, ER Ser167, p44/42 MAPK, and Akt, as well as expression of progesterone receptor (PR), AIB1, HER2, p53, and Ki67 in ER-positive invasive breast cancer, because these factors are involved in ER signaling and were predicted to affect prognosis. Correlation between phosphorylation and expression levels of these molecular markers and their significance for survival were analyzed to identify patients who need additional therapy, such as signal transduction inhibitors or chemotherapy, together with endocrine therapy in ER-positive early breast cancer.

	Materials and methods

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Patients and breast cancer tissues

Breast tumor specimens from 278 female patients with invasive breast carcinoma, who were treated at Nagoya City University Hospital between 1982 and 1999, were included in this study (Table 1). The study protocol was approved by the institutional review board and conformed to the guidelines of the 1975 Declaration of Helsinki. All patients had undergone surgical treatment for primary breast cancer (either mastectomy or lumpectomy) and all primary tumors were ER positive. The samples were chosen from the continuous series of invasive carcinoma tissues. After surgery, 61 patients received no additional therapy. Of the remaining 217 patients, 100 received systemic adjuvant therapy consisting of endocrine therapy alone, 24 received chemotherapy alone, and 93 received combined endocrine therapy and chemotherapy. Patients who were positive for axillary lymph nodes received either oral administration of 5-fluorouracil derivatives for 2 years or a combination of cyclophosphamide, methotrexate, and fluorouracil. Patients were observed for disease recurrence at least once every 6 months for the first 5 years after the surgery and thereafter once every year. The median follow-up period was 96 months.

One 4 µm section of each submitted paraffin block was stained first with hematoxylin and eosin to verify that an adequate number of invasive carcinoma cells were present and that the fixation quality was adequate for IHC analysis. Serial sections (4 µm) were prepared from selected blocks and float-mounted on adhesive-coated glass slides, for staining of phosphorylation of ER Ser118, ER Ser167, p44/42 MAPK, and Akt, and expression of ER, PR, AIB1, HER2, p53, and Ki67 as described previously (Yamashita et al. 2005). Primary antibodies included monoclonal mouse anti-human ER antibody (1D5, DAKO, Glostrup, Denmark) at 1:100 dilution for ER, polyclonal rabbit anti-phospho-ER (Ser118) antibody (no. 2515, Cell Signaling, Beverly, MA, USA) at 1:25 dilution for phosphorylated ER Ser118, polyclonal rabbit anti-phospho-ER (Ser167) antibody (no. 2514, Cell signaling) at 1:25 dilution for phosphorylated ER Ser167, polyclonal rabbit anti-phospho-p44/42 Map kinase (Thr202/Tyr204) antibody (no. 9101, Cell signaling) at 1:25 dilution for phosphorylated MAPK (extracellular signal-regulated kinase; ERK), polyclonal rabbit anti-phospho-Akt (Ser473) antibody (no. 9277, Cell signaling) at 1:50 dilution for phosphorylated Akt, monoclonal mouse anti-human PR antibody (636, DAKO) at 1:100 dilution for PR, monoclonal mouse anti-AIB-1 antibody (Clone 34, BD Biosciences, San Jose, CA, USA) at 1:50 dilution for AIB1, rabbit anti-human c-erbB-2 oncoprotein antibody (DAKO) at 1:200 dilution for HER2, monoclonal mouse anti-human p53 protein antibody (PAb1801, Novocastra, Newcastle, UK) at 1:50 dilution for p53, and monoclonal mouse anti-human Ki67 antibody (MIB-1, DAKO) at 1:100 dilution for Ki67. The DAKO Envision system (DAKO EnVision labeled polymer, peroxidase) was used as the detection system as described previously except for p53 (Yamashita et al. 2005). The streptavidin–biotin system (SAB-PO kit, Nichirei Co., Inc., Tokyo, Japan) was used for detection of the bound antibody of p53.

IHC scoring

Immunostained slides were scored after the entire slide was evaluated by light microscopy. The expression of ER, PR, and AIB1 and the phosphorylation of ER Ser118 and ER Ser167 were scored by assigning proportion and intensity scores, according to Allred's procedure (Allred et al. 1998). In brief, a proportion score represented the estimated proportion of tumor cells staining positive as follows: 0 (none); 1 (<1/100); 2 (1/100–1/10); 3 (1/10–1/3); 4 (1/3–2/3); and 5 (>2/3). Any brown nuclear staining in invasive breast epithelium counted toward the proportion score. An intensity score represented the average intensity of the positive cells as follows: 0 (none); 1 (weak); 2 (intermediate); and 3 (strong). The proportion and intensity scores were then added to obtain a total score, which could range from 0 to 8. Tumors with score 3 for ER were included in this study. The phosphorylation of MAPK and Akt was scored by assigning proportion scores as follows: 0 (none); 1 (<1/100); 2 (1/100–1/10); 3 (1/10–1/3); 4 (1/3–2/3); and 5 (>2/3). Any brown nuclear staining in invasive breast epithelium counted toward the proportion score. HER2 immunostaining was evaluated using the same method as is employed by the Hercep Test (DAKO). To determine the score of HER2 expression, the membrane staining pattern was estimated and scored on a scale of 0–3. The expression status of p53 and Ki67 was assessed according to the estimated proportion of nuclear staining of tumor cells that were positively stained as described previously (Yamashita et al. 2006). Scoring criteria were as follows: for p53: score=0, none; score=1, <1/10; score=2, 1/10–1/2; score=3, >1/2; and for Ki67: score=0, none; score=1, <1/100; score=2, 1/100–1/10; score=3, 1/10–1/2; score=4, >1/2.

Statistical analysis

The Mann–Whitney U test was used to compare the IHC scores of molecular markers with clinicopathological characteristics. Spearman's rank correlation test was used to study relationships among expression and phosphorylation of molecular markers. Estimation of disease-free and overall survival was performed using the Kaplan–Meier method, and differences between survival curves were assessed with the log-rank test. Cox's proportional hazards model was used for univariate and multivariate analyses of prognostic values.

	Results

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Correlation between expression and phosphorylation levels of molecular markers and clinicopathological factors

In this study, tumors with score 3 for ER were considered as ER positive and only patients with ER-positive tumors were included. We examined phosphorylation of ER Ser118, ER Ser167, MAPK, and Akt and expression of ER, PR, AIB1, HER2, p53, and Ki67 in 278 invasive breast carcinomas by IHC. The IHC scores for molecular markers were compared among patient subgroups, according to the clinicopathological factors. Phosphorylation of ER Ser167 was significantly correlated with tumor size (P=0.010) and lymph node status (P=0.012). There was a strong association between expression of AIB1 and tumor size (P=0.033). Phosphorylation of MAPK and expression of ER and Ki67 were significantly correlated with histological grade (P=0.044, P=0.036, and P=0.011 respectively). Expression of p53 was strongly correlated with tumor size (P=0.019), lymph node status (P=0.013), and histological grade (P=0.0009).

Correlation between expression and phosphorylation levels of molecular markers

Links between the IHC scores for phosphorylation of ER Ser118, ER Ser167, MAPK, and Akt and expression of ER, PR, AIB1, HER2, p53, and Ki67 were analyzed using Spearman's rank correlation test (Table 2). Phosphorylation levels of ER Ser118, ER Ser167, MAPK, and Akt were strongly and positively correlated (P<0.0001 respectively). Expression of ER was significantly correlated with phosphorylation of ER Ser118 (P=0.028), ER Ser167 (P=0.0002), and Akt (P=0.008) and expression of AIB1 (P=0.014) and Ki67 (P=0.017). Significant and positive association was also found between phosphorylation of ER Ser118 and expression of AIB1 (P<0.0001) and HER2 (P=0.019). AIB1 expression was strongly and positively correlated with phosphorylation of MAPK (P<0.0001) and Akt (P<0.0001) and expression of HER2 (P<0.0001) and Ki67 (P<0.0001). There was a significant association between Akt phosphorylation and Ki67 expression (P=0.0008). The PR expression was positively correlated with Akt phosphorylation (P=0.025) and negatively correlated with p53 expression (P=0.044).

Low phosphorylation of ER Ser118 and high phosphorylation of ER Ser167 improve survival in ER-positive breast cancer

To identify a clinically meaningful cutoff point for levels of phosphorylation and expression of molecular markers that could be used in disease prognosis analysis, various levels of phosphorylation and expression were tested using the Cox's proportional hazards model and the Kaplan–Meier method verified by the log-rank test. When analyzing disease-free and overall survival, the cutoff points for the levels of phosphorylation of ER Ser118 and ER Ser167 were set at 6 and 2 respectively, and the cutoff points for the levels of expression of AIB1, HER2, and Ki67 were set at 5, 2 and 1 respectively. Phosphorylation of MAPK and Akt and expression of PR and p53 were not significantly related to survival in the univariate analysis (Tables 3 and 4). Kaplan–Meier analysis showed that low phosphorylation of ER Ser118 (score 0–6) was strongly associated with increased disease-free and overall survival (P<0.0001 and P=0.0015 respectively; Fig. 1A and B). By contrast, low phosphorylation of ER Ser167 (score 0–2) was associated with significantly decreased disease-free and overall survival (P=0.001 and P=0.001 respectively; Fig. 1C and D). Combination analysis of phosphorylation status for ER Ser118 and ER Ser167 revealed that patients whose tumors showed both low ER Ser118 phosphorylation and high ER Ser167 phosphorylation had significantly longer disease-free and overall survival (P<0.0001 and P<0.0001 respectively), whereas patients with high ER Ser118 phosphorylation and low ER Ser167 phosphorylation relapsed and died significantly sooner after surgery (Fig. 1E and F).

View larger version (21K): [in this window] [in a new window]   Figure 1 Effect of phosphorylation of ER Ser118, ER Ser167, and combination subgroups of ER Ser118 and ER Ser167 on disease-free (A, C, and E) and overall (B, D, and F) survival.

Univariate analysis demonstrated significant association between disease-free survival and phosphorylation status of ER Ser118 (P<0.0001) and ER Ser167 (P=0.0013), as well as tumor size (P=0.0039), lymph node status (P<0.0001), histological grade (P=0.013), expression of AIB1 (P=0.011), HER2 (P=0.014), and Ki67 (P=0.026; Table 3). There was no significant association between disease-free survival and phosphorylation of MAPK or Akt or expression of PR or p53. In multivariate analysis, patients with low phosphorylation of ER Ser118 (P=0.0003) and high phosphorylation of ER Ser167 (P=0.0002), as well as patients with negative lymph node status (P<0.0001) and low expression of Ki67 (P=0.014), had significantly improved disease-free survival (Table 3).

Prognostic analysis of overall survival in ER-positive breast cancer

Univariate analysis showed significant association between overall survival and phosphorylation status of ER Ser118 (P=0.0024) and ER Ser167 (P=0.0020), as well as tumor size (P=0.0030), lymph node status (P<0.0001) and histological grade (P=0.0095; Table 4). There was no significant association between overall survival and phosphorylation of MAPK or Akt or expression of PR, AIB1, HER2, p53, or Ki67. In multivariate analysis, patients with low phosphorylation of ER Ser118 (P=0.0007) and high phosphorylation of ER Ser167 (P=0.0016), as well as patients with negative lymph node status (P=0.0002) had significantly improved overall survival (Table 4). We conclude that the phosphorylation levels of ER Ser118 and ER Ser167 are independent prognostic factors of disease-free and overall survival in ER-positive breast cancer.

	Discussion

Top Abstract Introduction Materials and methods Results Discussion Declaration of interest References

 
Using IHC technology, we investigated the phosphorylation of ER Ser118, ER Ser167, p44/42 MAPK, and Akt and expression of ER, PR, AIB1, HER2, p53, and Ki67 in ER-positive breast cancer. Our results indicate that those whose tumors showed low phosphorylation of ER Ser118 and high phosphorylation of ER Ser167 had a better disease-free and overall survival.

Our study demonstrated that phosphorylation of ER Ser118 was positively associated with phosphorylation of MAPK and expression of AIB1 and HER2, and that high phosphorylation of ER Ser118 and high expression of AIB1 and HER2 significantly reduced disease-free survival in ER-positive breast cancer. Murphy et al. demonstrated that phosphorylation of ER Ser118 correlated with active MAPK in 45 human breast tumor biopsies. Their result is consistent with our results that phosphorylation of ER Ser118 and MAPK was strongly and positively correlated (Murphy et al. 2004a). Our data also showed that significant and positive association was found between phosphorylation of ER Ser118 and expression of AIB1 and HER2. Gee et al. (2001) showed that phosphorylation of MAPK was associated with poor response to anti-hormonal therapy and decreased patient survival. It has been reported that ER is phosphorylated on Ser118 by MAPK (Kato et al. 1995), which also phosphorylates AIB1 (Font de Mora & Brown 2000). Furthermore, a recent study showed that AIB1 knockdown reduced EGF-induced HER2 phosphorylation (Lahusen et al. 2007). Because MAPK is located downstream of HER2, our study suggests that phosphorylation of ER Ser118 is in part caused by HER2–MAPK signaling in human breast cancer and that the HER2–MAPK–AIB1–ER Ser118 pathway may contribute to poor prognosis and endocrine therapy resistance in ER-positive breast cancer. Previous studies have shown that HER2-induced MAPK and ER activation leads to tamoxifen resistance (Kurokawa et al. 2000). Data from these clinical trials demonstrated that the antiproliferative response to endocrine therapy was impaired in ER-positive/HER2-positive primary breast cancers (Dowsett et al. 2001). It was also reported that ligand-dependent phosphorylation at Ser118 and Ser167 of ER was lost in tamoxifen-resistant MCF-7 Her2/neu cells (Likhite et al. 2006). Sarwar et al. (2006) reported that phosphorylation of ER Ser118 in 301 breast cancer tissues was higher in more differentiated tumors, whereas no significant correlation was found between phosphorylation of ER Ser118 and clinicopathological factors, such as tumor size, lymph node status, and histological grade in our present study. Patients with ER-negative tumors (6.3%) were included in their study. Although phosphorylation of ER Ser118 was not associated with survival, there was a positive correlation between phosphorylation of MAPK staining and ER Ser118 staining in their studies. They also demonstrated that phosphorylation of ER Ser118 was elevated in tumor biopsies taken from patients who had relapsed following tamoxifen treatment. In vitro studies have demonstrated that phosphorylation of ER Ser118 is stimulated by both estrogen-dependent and -independent pathways, so that a similar phenomenon may occur in clinical breast cancers.

Murphy et al. (2004b) analyzed phosphorylation of ER Ser118 by IHC in 117 breast cancer tissues and showed that phosphorylation of ER Ser118 is a marker of better prognosis in patients treated with tamoxifen. Their result is opposite to ours. However, expression status of ER in their study was analyzed by ligand-binding assay not by IHC and there were four cases (3.4%) with ER-negative tumors. Moreover, immunohistochemically determined phosphorylation status of ER Ser118 was evaluated as positive if any nuclear staining was detectable and negative in the absence of any detectable nuclear staining. We set at the cutoff at a score of 6 by Allred's methods. Cutoff points for IHC analysis should be investigated in further studies.

We previously found that patients whose primary breast tumors showed high phosphorylation of ER Ser167 responded significantly better to endocrine therapy than those that did not (Yamashita et al. 2005). In this study, we demonstrated that high phosphorylation of ER Ser167 improves survival in ER-positive breast cancer. Moreover, our present data indicate that high phosphorylation of ER Ser167 is associated with significantly increased disease-free survival in ER-positive breast cancer patients who received endocrine therapy alone as adjuvant therapy. Since our previous and present studies demonstrate that phosphorylation of ER Ser167 is predictive of response to endocrine therapy and improved survival in ER-positive breast cancer, it is suggested that phosphorylation of ER Ser167 may occur frequently in response to estradiol binding. By contrast, phosphorylation of ER Ser118 was not predictive of response to endocrine therapy, and high phosphorylation of this residue correlated with poor prognosis, indicating that ER Ser118 phosphorylation occurs frequently without estradiol.

Several studies have reported that phosphorylation of Akt predicts worse outcome and tamoxifen resistance in ER-positive breast cancer (Perez-Tenorio & Stal 2002, Kirkegaard et al. 2005, Tokunaga et al. 2006a,b). Our data did not indicate correlation between Akt phosphorylation and prognosis, although phosphorylation of Akt was strongly and positively associated with phosphorylation of ER Ser118, ER Ser167, and MAPK, and expression of AIB1. It was reported that estradiol rapidly activates Akt via the HER2 signaling pathway (Stoica et al. 2003). Akt might be activated via growth factor signaling pathways both estrogen dependently and -independently in breast cancer.

In conclusion, the present study has demonstrated for the first time that low phosphorylation of ER Ser118 and high phosphorylation of ER Ser167 significantly improve disease-free and overall survival in ER-positive breast cancer. Our data suggest that phosphorylation of ER Ser118 and ER Ser167 affects survival in ER-positive breast cancer and could be helpful in distinguishing patients who are likely to benefit from endocrine therapy alone from those who are not.

	Declaration of interest

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The authors declare that there is no conflict of interest that would prejudice the impartiality of this scientific work.

	Funding

 
This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.

	Acknowledgements

 
We thank Yoshikazu Sugimoto for assistance, and Hideki Nagase and Yoshihiro Okayama for statistical assistance.

	References

Top Abstract Introduction Materials and methods Results Discussion Declaration of interest References

 
Allred DC, Harvey JM, Berardo M & Clark GM 1998 Prognostic and predictive factors in breast cancer by immunohistochemical analysis. Modern Pathology 11 155–168.[Web of Science][Medline]

Arnold SF, Obourn JD, Jaffe H & Notides AC 1994 Serine 167 is the major estradiol-induced phosphorylation site on the human estrogen receptor. Molecular Endocrinology 8 1208–1214.[Abstract/Free Full Text]

Campbell RA, Bhat-Nakshatri P, Patel NM, Constantinidou D, Ali S & Nakshatri H 2001 Phosphatidylinositol 3-kinase/AKT-mediated activation of estrogen receptor : a new model for anti-estrogen resistance. Journal of Biological Chemistry 276 9817–9824.[Abstract/Free Full Text]

Clark DE, Poteet-Smith CE, Smith JA & Lannigan DA 2001 Rsk2 allosterically activates estrogen receptor alpha by docking to the hormone-binding domain. EMBO Journal 20 3484–3494.[CrossRef][Web of Science][Medline]

Dowsett M, Harper-Wynne C, Boeddinghaus I, Salter J, Hills M, Dixon M, Ebbs S, Gui G, Sacks N & Smith I 2001 HER-2 amplification impedes the antiproliferative effects of hormone therapy in estrogen receptor-positive primary breast cancer. Cancer Research 61 8452–8458.[Abstract/Free Full Text]

Ellis M 2004 Overcoming endocrine therapy resistance by signal transduction inhibition. Oncologist 9 20–26.[Abstract/Free Full Text]

Font de Mora J & Brown M 2000 AIB1 is a conduit for kinase-mediated growth factor signaling to the estrogen receptor. Molecular and Cellular Biology 20 5041–5047.[Abstract/Free Full Text]

Gee JM, Robertson JF, Ellis IO & Nicholson RI 2001 Phosphorylation of ERK1/2 mitogen-activated protein kinase is associated with poor response to anti-hormonal therapy and decreased patient survival in clinical breast cancer. International Journal of Cancer 95 247–254.[CrossRef][Web of Science][Medline]

Joel PB, Smith J, Sturgill TW, Fisher TL, Blenis J & Lannigan DA 1998 pp90rsk1 regulates estrogen receptor-mediated transcription through phosphorylation of Ser-167. Molecular and Cellular Biology 18 1978–1984.[Abstract/Free Full Text]

Johnston SR, Head J, Pancholi S, Detre S, Martin LA, Smith IE & Dowsett M 2003 Integration of signal transduction inhibitors with endocrine therapy: an approach to overcoming hormone resistance in breast cancer. Clinical Cancer Research 9 524S–532S.[Abstract/Free Full Text]

Kato S, Endoh H, Masuhiro Y, Kitamoto T, Uchiyama S, Sasaki H, Masushige S, Gotoh Y, Nishida E, Kawashima H et al. 1995 Activation of the estrogen receptor through phosphorylation by mitogen-activated protein kinase. Science 270 1491–1494.[Abstract/Free Full Text]

Kirkegaard T, Witton CJ, McGlynn LM, Tovey SM, Dunne B, Lyon A & Bartlett JM 2005 AKT activation predicts outcome in breast cancer patients treated with tamoxifen. Journal of Pathology 207 139–146.[CrossRef][Web of Science][Medline]

Kurokawa H, Lenferink AE, Simpson JF, Pisacane PI, Sliwkowski MX, Forbes JT & Arteaga CL 2000 Inhibition of HER2/neu (erbB-2) and mitogen-activated protein kinases enhances tamoxifen action against HER2-overexpressing, tamoxifen-resistant breast cancer cells. Cancer Research 60 5887–5894.[Abstract/Free Full Text]

Lahusen T, Fereshteh M, Oh A, Wellstein A & Riegel AT 2007 Epidermal growth factor receptor tyrosine phosphorylation and signaling controlled by a nuclear receptor coactivator, amplified in breast cancer 1. Cancer Research 67 7256–7265.[Abstract/Free Full Text]

Lannigan DA 2003 Estrogen receptor phosphorylation. Steroids 68 1–9.[CrossRef][Web of Science][Medline]

Likhite VS, Stossi F, Kim K, Katzenellenbogen BS & Katzenellenbogen JA 2006 Kinase-specific phosphorylation of the estrogen receptor changes receptor interactions with ligand, deoxyribonucleic acid, and coregulators associated with alterations in estrogen and tamoxifen activity. Molecular Endocrinology 20 3120–3132.[Abstract/Free Full Text]

Murphy L, Cherlet T, Adeyinka A, Niu Y, Snell L & Watson P 2004a Phospho-serine-118 estrogen receptor-alpha detection in human breast tumors in vivo. Clinical Cancer Research 10 1354–1359.[Abstract/Free Full Text]

Murphy LC, Niu Y, Snell L & Watson P 2004b Phospho-serine-118 estrogen receptor-alpha expression is associated with better disease outcome in women treated with tamoxifen. Clinical Cancer Research 10 5902–5906.[Abstract/Free Full Text]

Osborne CK & Schiff R 2005 Estrogen-receptor biology: continuing progress and therapeutic implications. Journal of Clinical Oncology 23 1616–1622.[Free Full Text]

Osborne CK, Bardou V, Hopp TA, Chamness GC, Hilsenbeck SG, Fuqua SA, Wong J, Allred DC, Clark GM & Schiff R 2003 Role of the estrogen receptor coactivator AIB1 (SRC-3) and HER-2/neu in tamoxifen resistance in breast cancer. Journal of the National Cancer Institute 95 353–361.[Abstract/Free Full Text]

Perez-Tenorio G & Stal O 2002 Activation of AKT/PKB in breast cancer predicts a worse outcome among endocrine treated patients. British Journal of Cancer 86 540–545.[CrossRef][Web of Science][Medline]

Sarwar N, Kim JS, Jiang J, Peston D, Sinnett HD, Madden P, Gee JM, Nicholson RI, Lykkesfeldt AE, Shousha S et al. 2006 Phosphorylation of ERalpha at serine 118 in primary breast cancer and in tamoxifen-resistant tumours is indicative of a complex role for ERalpha phosphorylation in breast cancer progression. Endocrine-Related Cancer 13 851–861.[Abstract/Free Full Text]

Schiff R, Massarweh S, Shou J & Osborne CK 2003 Breast cancer endocrine resistance: how growth factor signaling and estrogen receptor coregulators modulate response. Clinical Cancer Research 9 447S–454S.[Abstract/Free Full Text]

Shou J, Massarweh S, Osborne CK, Wakeling AE, Ali S, Weiss H & Schiff R 2004 Mechanisms of tamoxifen resistance: increased estrogen receptor-HER2/neu cross-talk in ER/HER2-positive breast cancer. Journal of the National Cancer Institute 96 926–935.[Abstract/Free Full Text]

Stoica GE, Franke TF, Wellstein A, Czubayko F, List HJ, Reiter R, Morgan E, Martin MB & Stoica A 2003 Estradiol rapidly activates Akt via the ErbB2 signaling pathway. Molecular Endocrinology 17 818–830.[Abstract/Free Full Text]

Tokunaga E, Kimura Y, Oki E, Ueda N, Futatsugi M, Mashino K, Yamamoto M, Ikebe M, Kakeji Y, Baba H et al. 2006a Akt is frequently activated in HER2/neu-positive breast cancers and associated with poor prognosis among hormone-treated patients. International Journal of Cancer 118 284–289.[CrossRef][Web of Science][Medline]

Tokunaga E, Kataoka A, Kimura Y, Oki E, Mashino K, Nishida K, Koga T, Morita M, Kakeji Y, Baba H et al. 2006b The association between Akt activation and resistance to hormone therapy in metastatic breast cancer. European Journal of Cancer 42 629–635.[CrossRef][Web of Science][Medline]

Yamashita H, Nishio M, Kobayashi S, Ando Y, Sugiura H, Zhang Z, Hamaguchi M, Mita K, Fujii Y & Iwase H 2005 Phosphorylation of estrogen receptor alpha serine 167 is predictive of response to endocrine therapy and increases postrelapse survival in metastatic breast cancer. Breast Cancer Research 7 R753–R764.[CrossRef][Web of Science][Medline]

Yamashita H, Toyama T, Nishio M, Ando Y, Hamaguchi M, Zhang Z, Kobayashi S, Fujii Y & Iwase H 2006 p53 protein accumulation predicts resistance to endocrine therapy and decreased post-relapse survival in metastatic breast cancer. Breast Cancer Research 8 R48[CrossRef][Medline]

This Article Abstract Full Text (PDF) All Versions of this Article: ERC-08-0078v1 15/3/755    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yamashita, H. Articles by Iwase, H. Search for Related Content PubMed PubMed Citation Articles by Yamashita, H. Articles by Iwase, H.