Oestrogen receptor (ERalpha) expression is a strong predictor of response to endocrine therapy. The PI3K/AKT/mTOR signal transduction pathway has been implicated in endocrine resistance in vitro. The present study was carried out to test the hypothesis that AKT activation mediates tamoxifen resistance in clinical breast cancer. Immunohistochemistry (IHC) using AKT1-3, pan-AKT, pAKT (Thr-308), pAKT (Ser-473), pER (Ser-167), and pHER2 antibodies was performed on 402 ERalpha-positive breast carcinomas from patients treated with tamoxifen. High pAKT (Ser-473) activity (p = 0.0406) and low AKT2 expression (p = 0.0115) alone, or in combination [high pAKT (Ser-473)/low AKT2; 'high-risk' patient group] (p = 0.0014), predicted decreased overall survival in tamoxifen-treated patients with ERalpha-positive breast cancers. There was no significant association between tumour levels of AKT expression or activity and disease-free survival (DFS); however, the 'high-risk' patient group was significantly more likely to relapse (p = 0.0491). During tamoxifen treatment, neither AKT2 nor pAKT predicted DFS. Finally, activation of AKT, via phosphorylation, was linked to activation of both HER2 and ERalpha in this patient cohort. The data presented here show that the PI3K/AKT/mTOR pathway is associated with relapse and death in ERalpha-positive breast cancer patients treated with tamoxifen, supporting in vitro evidence that AKT mediates tamoxifen resistance. Patients with a 'high-risk' expression profile were at increased risk of death (hazard ratio 3.22, p = 0.002) relative to 'low-risk' patients, highlighting the potential that tumour profiling, with multiple IHC markers predictive of therapeutic response, may improve patient selection for endocrine therapies, eg tamoxifen or aromatase inhibitor-based treatments.

ERBB4/HER4 (referred to here as ERBB4) is a unique member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. In contrast to the other three members of the EGFR family (i.e., EGFR, ERBB2/HER2/ NEU, and ERBB3), which are associated with aggressive forms of human cancers, ERBB4 expression seems to be selectively lost in tumors with aggressive phenotypes. Consistent with this observation, we show that ERBB4 induces apoptosis when reintroduced into breast cancer cell lines or when endogenous ERBB4 is activated by a ligand. We further show that ligand activation and subsequent proteolytic processing of endogenous ERBB4 results in mitochondrial accumulation of the ERBB4 intracellular domain (4ICD) and cytochrome c efflux, the essential and committed step of mitochondrial regulated apoptosis. Our results indicate that 4ICD is functionally similar to BH3-only proteins, proapoptotic members of the BCL-2 family required for initiation of mitochondrial dysfunction through activation of the proapoptotic multi-BH domain proteins BAX/BAK. Similar to other BH3-only proteins, 4ICD cell-killing activity requires an intact BH3 domain and 4ICD interaction with the antiapoptotic protein BCL-2, suppressed 4ICD-induced apoptosis. Unique among BH3-only proteins, however, is the essential requirement of BAK but not BAX to transmit the 4ICD apoptotic signal. Clinically, cytosolic but not membrane ERBB4/ 4ICD expression in primary human breast tumors was associated with tumor apoptosis, providing a mechanistic explanation for the loss of ERBB4 expression during tumor progression. Thus, we propose that ligand-induced mitochondrial accumulation of 4ICD represents a unique mechanism of action for transmembrane receptors, directly coupling a cell surface signal to the tumor cell mitochondrial apoptotic pathway. (Cancer Res 2006; 66(12): 6412-20)

We have demonstrated that ICCC is a consistent method to assess observer variation when a continuous scoring system is used, compared with kappa statistics, which depends on a categorical system. Given the importance of accurate assessment of protein expression in diagnostic and experimental medicine, we suggest raising thresholds for observer variation: ICCC of 0.7 should be regarded as the minimum acceptable standard, ICCC of 0.8 as good and ICCC of > or = 0.9 as excellent.

We demonstrate here a new concept termed "oncogene tolerance" whereby human EGF receptor 2 (HER2) increases sphingosine kinase 1 (SK1) expression in estrogen receptor-positive (ER ؉ ) MCF-7 HER2 cells and SK1, in turn, limits HER2 expression in a negative-feedback manner. The HER2-dependent increase in SK1 expression also limits p21-activated protein kinase 1 (p65 PAK1) and extracellular signal regulated kinase 1/2 (ERK-1/2) signaling. Sphingosine 1-phosphate signaling via S1P 3 is also altered in MCF-7 HER2 cells. In this regard, S1P binding to S1P 3 induces a migratory phenotype via an SK1-dependent mechanism in ER ؉ MCF-7 Neo cells, which lack HER2. This involves the S1P stimulated accumulation of phosphorylated ERK-1/2 and actin into membrane ruffles/lamellipodia and migration. In contrast, S1P failed to promote redistribution of phosphorylated ERK-1/2 and actin into membrane ruffles/lamellipodia or migration of MCF-7 HER2 cells. However, a migratory phenotype in these cells could be induced in response to S1P when SK1 expression had been knocked down with a specific siRNA or when recombinant PAK1 was ectopically overexpressed. Thus, the HER2-dependent increase in SK1 expression functions to desensitize the S1P-induced formation of a migratory phenotype. This is correlated with improved prognosis in patients who have a low HER1-3/SK1 expression ratio in their ER ؉ breast cancer tumors compared to patients that have a high HER1-3/SK1 expression ratio."Oncogene addiction" is a term that has been used to describe the reliance of cancer cells on the continued expression of oncogenes in order to maintain the diseased phenotype, progression, and metastasis of the cancer cell (39). Oncogene addiction is intrinsically susceptible to cross talk and feedback regulation that reflects abnormal signaling wiring in the cancer cell and which potentially makes these cells more susceptible to drug intervention at the level of the oncogene than normal cells. HER2 is a well-established oncogene that has an important role in enhancing breast cancer progression (2). The importance of its functional role as an addictive oncogene is exemplified by the fact that targeting HER2 with antibody mediated therapies, such as herceptin, demonstrates significant clinical efficacy (40). Indeed, this approach is in line with the concept that oncogene addiction is the "Achilles heel" of the cancer cell.There are four members of the human epidermal growth factor (EGF) receptor-related family, termed HER1 to HER4. The HER2/neu (c-erbB-2) gene encodes a 185-kDa transmembrane receptor tyrosine kinase, which is similar in amino acid sequence to other members of the EGF receptor family (30). Moreover, the overexpression of HER2/neu and gene amplification is found in up to 30% of primary breast cancers, and its expression is correlated with increased tumor invasion, poor prognosis, and therapeutic resistance (2). Overexpression of HER2 is also associated with downregulation of the estrogen receptor (ER) but not necessarily the complete elimination of...

Purpose: Resistance to tamoxifen is linked to overexpression of HER2, and aromatase inhibitors show particular benefit in progesterone receptor (PR)^negative patients.We previously reported reduced survival in patients overexpressing HER1, HER2, and HER3. We now show that both HER1-3 and PR status predicts for early relapse in estrogen receptor (ER)^positive tamoxifentreated breast cancer patients. Experimental Design: Tissue microarray technology was used to analyze 402 ER-positive tamoxifen-treated patients. Immunohistochemistry using epidermal growth factor receptor, HER2, HER3, HER4, and PR antibodies was done. Kaplan-Meier life table and Cox Regression analysis (log-rank testing of differences in breast cancer^related relapse on tamoxifen) was done. Results: HER1-3 (but not HER4) overexpression predicted for early relapse on tamoxifen (P = 0.0060). PR-negative cases were also significantly more likely to relapse while on tamoxifen (P = 0.017). HER1-3-positive and/or PR-negative patients combined as a ''high-risk'' group were significantly more likely to relapse on tamoxifen in univariate (P < 0.0001) and Cox's multivariate analysis (P = 0.0069). However, this applied to early relapse on tamoxifen only, as any disease relapse after 3 years of tamoxifen was unrelated to PR/HER status. Conclusions: We show that HER1-3 and PR status can identify time-dependent de novo tamoxifen resistance with risk declining markedly after 3 years of tamoxifen treatment. These results parallel data from the ATAC and Intergroup Exemastane Study trials which suggest that whereas PR-negative patients derive greater benefit from initial aromatase inhibitor treatment, PR status has no effect on response when given as delayed treatment to those disease free on tamoxifen after 3 years.

Background: We have shown previously that whereas overexpression of human epidermal growth factor receptor (HER)1, HER2 and HER3 is associated with poor prognosis in breast cancer, HER4 is associated with a good prognosis. Cell proliferation is a key component of aggressive cancers and is driven by growth factors. In this study, bromodeoxyuridine (BrdU)-derived proliferation indices are correlated with clinical outcome and HER1-4 status for further clarification of the differing roles for the HER family at a biological level.Methods: Seventy-eight invasive breast cancers had BrdU labelling in vivo to determine the BrdU labelling index (BLI) and the potential tumour doubling time (T pot ). Long-term clinical follow-up was available for these patients. We used immunohistochemistry to establish the HER1-4 status in 55 patients from the BrdU cohort. Results:We demonstrate a significant correlation between high BLI values and breast cancer-specific death (P = 0.0174). Low T pot times were also significantly correlated with breast cancer-specific death (P = 0.0258). However, BLI did not independently predict survival in Cox's multiple regression analysis when combined with other prognostic factors such as size, grade and nodal status. Tumours found to be positive for HER1, HER2 or HER3 had significantly (P = 0.041) higher labelling indices, with HER1 also showing significantly higher indices when considered independently (P = 0.024). Conversely, HER4 positivity was significantly correlated (P = 0.013) with low BLI values, in line with previous data associating this receptor with good prognosis tumours. Conclusions:These results support the hypothesis that HER1-3 are associated with driving tumour proliferation, whereas HER4 is involved in a non-proliferative or even protective role.

Purpose: Amplified in breast cancer 1 (AIB1) is a member of the p160/steroid receptor coactivators family and is involved in estrogen-dependent gene transcription by reducing the antagonistic activity of tamoxifen-bound estrogen receptor-a (ER-a).The present study was carried out to test the hypothesis that AIB1protein expression and/or gene amplification mediates tamoxifen resistance in breast cancer. Experimental Design: Immunohistochemistry using AIB1 antibody and fluorescence in situ hybridization using probes specific forAIB1and chromosome 20 was done on 402 ER-a^positive tamoxifen-treated breast cancers. Results: AIB1overexpression was not associated with relapse during treatment with tamoxifen. In contrast, high AIB1expression in patients with human epidermal growth factor receptor (HER) 2^and HER3-overexpressing tumors or tumors expressing one or more of HER1, HER2, or HER3 (HER1-3 positive) was associated with an increased risk of relapse on tamoxifen [hazard ratio, 2.20; 95% confidence interval, 1.07-3.52 (P = 0.0416); hazard ratio, 2.42; 95% confidence interval, 1.32-4.43 (P = 0.0030), respectively]. AIB1 gene amplification was observed in 18 of 362 (5%) patients. High AIB1 gene copy number had no effect on overall or disease-free survival. Conclusions: Data presented here support a role forAIB1expression on relapse during tamoxifen treatment in hormone-responsive HER-expressing clinical breast cancers and support clinical evidence, suggesting a cross-talk between ER-a and growth factor receptor pathways through changes in expression of specific coactivator proteins, such as AIB1. This study highlights the potential that tumor profiling, using multiple markers of treatment response, may improve patient selection for endocrine treatment, such as tamoxifen or aromatase inhibitors.

PurposeIn an earlier randomised controlled trial, we showed that early stage breast cancer patients who received a supervised exercise programme, with discussion of behaviour change techniques, had psychological and functional benefits 6 months after the intervention. The purpose of this study was to determine if benefits observed at 6 months persisted 18 and 60 months later.MethodsWomen who were in the original trial were contacted at 18 and 60 months after intervention. Original measures were repeated.ResultsOf the 148 women from the original study who agreed to be contacted again, 114 attended for follow-up at 18 months and 87 at 60 months. Women in the original intervention group reported more leisure time physical activity and more positive moods at 60 months than women in the original control group. Irrespective of original group allocation, women who were more active consistently reported lower levels of depression and increased quality of life compared to those who were less active.ConclusionsWe have shown that there are lasting benefits to an exercise intervention delivered during treatment to breast cancer survivors. Regular activity should be encouraged for women with early stage breast cancer as this can have lasting implications for physical and psychological functioning.