AIB1 Expression Research Articles

Aib1 deficiency exacerbates inflammatory responses in acute myocardial infarction mice.

Acute myocardial infarction (AMI) is one of the major causes of death throughout the world, while inflammation has been known as a major contributor to the pathophysiology of AMI. Inhibition of inflammation is shown to protect from AMI. Amplified in breast 1 (Aib1) is a transcriptional coactivator protein which can suppress inflammation. The anti-inflammatory activities of Aib1 imply its potential effects against AMI; however, to date the role of Aib1 in AMI has not been described yet. Here we explored the potential functions of Aib1 in AMI. We induced AMI in both wild-type (WT) and Aib1-/- mice. The expression levels of Aib1 and inflammatory cytokines in the AMI WT mice were measured by RT-PCR and Western blot. The heart infarction area and cardiac functions were compared between the AMI WT and Aib1-/- mice. The expression levels of inflammatory cytokines including IL-6, IL-1β, TNF-α, and MCP-1 in heart tissues were compared between the AMI WT and Aib1-/- mice by ELISA and RT-PCR. AMI induced the production of inflammatory cytokines whereas suppressed the expression of Aib1 in WT mice. AMI Aib1-/- mice displayed increased infarct area and aggravated heart dysfunction, as well as upregulated levels of Il-6, Il-1β, Tnf-α, and Mcp-1 in heart tissues. Aib1 deficiency exacerbates inflammation in AMI mice. KEY MESSAGES: AMI induced inflammation in the heart tissue of mice. Aib1 knockout exacerbated infarction in AMI mice. Aib1 knockout exacerbated cardiac dysfunction in AMI mice. Aib1 knockout exacerbated inflammation in AMI mice.

Design of a hybrid deep learning system for discriminating between low- and high-grade colorectal cancer lesions, using microscopy images of IHC stained for AIB1 expression biopsy material

Design of a hybrid deep learning system for discriminating between low- and high-grade colorectal cancer lesions, using microscopy images of IHC stained for AIB1 expression biopsy material

PAX2 promoter methylation and AIB1 overexpression promote tamoxifen resistance in breast carcinoma patients.

Disease recurrence is an important obstacle in estrogen receptor positive (ER+) tamoxifen treated breast carcinoma patients. Tamoxifen resistance-related molecular mechanisms are not fully understood. Alteration in DNA methylation which contributes to transcriptional regulation of cancer-related genes plays a crucial role in tamoxifen response. In the present study, the contribution of promoter methylation and mRNA expression of PAX2 and AIB1 in the development of breast carcinoma and tamoxifen refractory was assessed. Methylation specific-high resolution melting (MS-HRM) analysis and Real-time quantitative PCR (RT-qPCR) experiment were performed to analyze the promoter methylation and mRNA expression levels of PAX2 and AIB1 genes in 102 breast tumors and adjacent normal breast specimens. We indicated that PAX2 expression is decreased in breast tissues due to hypermethylation in its promoter region. Compared to the adjacent normal tissues, the tumors exhibited significantly lower relative mRNA levels of PAX2 and increased expression of AIB1. Aberrant promoter methylation of PAX2 and overexpression of AIB1 was observed in tamoxifen resistance patients compared to the sensitive ones. Cox regression analysis exhibited that the increased promoter methylation status of PAX2 and overexpression of AIB1 remained as unfavorable identifiers which influence patients' survival independently. Our results revealed that the aberration in PAX2 promoter methylation and AIB1 overexpression are associated with the tamoxifen response in breast carcinoma patients. Further research is needed to demonstrate the potential of using PAX2 and AIB1 expression and their methylation-mediated regulation as predictive or prognostic biomarkers or as a new target therapy for better disease management.

Comparative analysis of the AIB1 interactome in breast cancer reveals MTA2 as a repressive partner which silences E-Cadherin to promote EMT and associates with a pro-metastatic phenotype

Steroid regulated cancer cells use nuclear receptors and associated regulatory proteins to orchestrate transcriptional networks to drive disease progression. In primary breast cancer, the coactivator AIB1 promotes estrogen receptor (ER) transcriptional activity to enhance cell proliferation. The function of the coactivator in ER+ metastasis however is not established. Here we describe AIB1 as a survival factor, regulator of pro-metastatic transcriptional pathways and a promising actionable target. Genomic alterations and functional expression of AIB1 associated with reduced disease-free survival in patients and enhanced metastatic capacity in novel CDX and PDX ex-vivo models of ER+ metastatic disease. Comparative analysis of the AIB1 interactome with complementary RNAseq characterized AIB1 as a transcriptional repressor. Specifically, we report that AIB1 interacts with MTA2 to form a repressive complex, inhibiting CDH1 (encoding E-cadherin) to promote EMT and drive progression. We further report that pharmacological and genetic inhibition of AIB1 demonstrates significant anti-proliferative activity in patient-derived models establishing AIB1 as a viable strategy to target endocrine resistant metastasis. This work defines a novel role for AIB1 in the regulation of EMT through transcriptional repression in advanced cancer cells with a considerable implication for prognosis and therapeutic interventions.

Correlating Changes in the Epithelial Gland Tissue With Advancing Colorectal Cancer Histologic Grade, Using IHC Stained for AIB1 Expression Biopsy Material

The objective of this study was to study the textural and color changes occurring in the epithelial gland tissue with advancing colorectal cancer (CRC), utilizing immunohistochemical stain for AIB1 expression biopsy material. Clinical material comprised biopsy specimens of 67 patients with a diagnosis of CRC. Two experienced pathologists used H&E-stained material for grading CRC lesions and immunohistochemical (IHC) stain for AIB1 expression. Twenty six patients were diagnosed with grade I, 28 with grade II, and 13 with grade III CRC. Guided by pathologists, we selected the regions of interest from AIB1-digitized images of each patient, encompassing the epithelial gland, and we computed 69 features, quantifying textural and color properties of the AIB1-stained lesions. We evaluated the statistical differences between grades by means of the Wilcoxon statistical test for each feature, and we assessed changes in feature values with advancing tumor grade by means of the Point Biserial Correlation. Statistical analysis revealed 14 single features, quantifying textural and color properties of the epithelial gland, which sustained statistically significant differences between LG-CRC and HG-CRC cases. These features were drawn from the gray-level image histogram, the cooccurrence matrix, the run length matrix, the discrete wavelet transform, the Tamura method, and the L*a*b color transform. A systematic statistical analysis of AIB1-stained biopsy material showed that high-grade CRC lesions contain higher intensity levels, appear coarser, are more homogeneous with smooth variation across the image, have lower contrast that is slowly varying across the image, have lower AIB1 staining, and have lower edges. A combination of textural and color attributes, evaluating image gray-tone distribution, textural roughness, inhomogeneity, AIB1 staining, and image coarseness should be considered in evaluating AIB1-stained CRC lesions.

Prognostic value of AIB1 and EIF5A2 in intravesical recurrence after surgery for upper tract urothelial carcinoma.

ObjectivesThe aim of this study was to investigate the prognostic effect of amplified in AIB1 and EIF5A2 expression on postoperative intravesical recurrence for upper urinary tract urothelial carcinoma (UTUC) and improve postoperative risk stratification and prediction of intravesical chemotherapy benefit.Materials and methodsWe evaluated immunohistochemical expression of AIB1 and EIF5A2 in 109 UTUC patients to determine the predictive significance in intravesical recurrence. A prognostic model was developed based on univariate and multivariate analyses.ResultsIntravesical recurrence occurred in 18 out of the 109 (16.5%) patients during the follow-up period. Significant associations of high expression of AIB1 and EIF5A2 with shortened bladder recurrence interval (median: 24 months vs 46 months, P=0.021; 28 months vs 39 months, P=0.002) were demonstrated. In different subsets of UTUC patients, high expression of AIB1 was a prognostic indicator in high grade (P=0.006) and pT2–4 (P=0.007), and high expression of EIF5A2 for high grade (P=0.014), pT2–4 (P=0.002) and pN0 (P=0.009). Moreover, in multivariate analysis, AIB1 and EIF5A2 expression (P=0.034 and 0.022, respectively) together with pN stage (P=0.009) provided significant independent predictors for intravesical recurrence after surgery for UTUC. Surgical approach with radical nephroureterectomy (RNU) was an informative factor toward good oncologic outcomes for intravesical recurrence (P=0.056). Based on a prognostic model with these factors, patients with UTUC were classified into the low-risk group and the high-risk group. In a subset analysis, the patients in the high-risk group were found to have a favorable response to intravesical chemotherapy (P=0.047). A nomogram based on the multivariate analysis was developed to predict intravesical recurrence accurately and guide postoperative intravesical instillations. The concordance index (c-index) of this model was 0.806.ConclusionHigh expression of AIB1 and EIF5A2 were independent predictors for intravesical recurrence after RNU and might be able to predict which patients benefit from postoperative intravesical chemotherapy.

Roles of the AIB1 protein in the proliferation and transformation of human esophageal squamous cell carcinoma.

The aim of this study was to investigate the expression of AIB1 in human esophageal squamous cell carcinoma and its correlation with Ki67 expression. The immunohistochemical method streptavidin-perosidase was used to analyze the expression of AIB1 and Ki67 in specimens from 60 patients with esophageal squamous cell carcinoma and in 20 control individuals with normal esophageal tissue. Expression correlation, clinical significance, and relationships between the two groups were determined. In the 20 individuals with normal esophageal mucosa cells, AIB expression was primarily detected at low levels in the nucleus or not at all, whereas 41.6% of specimens from individuals with esophageal squamous cell carcinoma exhibited high levels of AIB1 expression (P < 0.05). Furthermore, overexpression of AIB1 was observed more frequently in carcinoma specimens with late T stages (T3/ T4) and lymph node metastases (P < 0.05). No significant differences were observed in AIB1 expression by gender, age, or pathological type (P < 0.05). Comparatively, the rate of positive expression of Ki67 In esophageal squamous cell carcinoma specimens was 65.0% (39/60) (P < 0.05). Of these, 29 specimens exhibited simultaneous expression of AIB1, 25 of which demonstrated AIB1 overexpression; expression of AIB1 and Ki67 was positively correlated (P < 0.01). In summary, the results from this study suggested that AIB1 protein expression was associated with the T stage and lymph node metastasis in esophageal squamous cell carcinoma, and that Ki67 might play a role in the AIB1 non-steroid receptor pathway.

Abstract B121: AIB1 is a transcriptional and translational mediator of breast cancer cell growth and migration targets

Abstract The nuclear p160 steroid receptor co-activator, AIB1 is a downstream regulator of the insulin-like growth factor (IGF-I) tyrosine kinase signaling axis [1]. Since AIB1 is over-expressed in 31-64% of breast cancers cell several mechanisms have been described to explain its function in breast cancer [2]. AIB1 transcriptionally regulates genes involved in carcinogenesis via its co-partnership with estrogen receptor alpha (ERα) and E2F1 [3]. Interestingly the transcriptional mediators, c-myc and E2F1 induce mRNA translation potentially via the transcriptional regulation of ribosome biogenesis factors [4]. However, whether AIB1 acts in similarly is not well known [3]. Furthermore, since IGF-I signaling stimulates mRNA cap-dependent translation and also affects AIB1, we hypothesize that AIB1 acts as both a transcriptional and translational regulator of breast cancer cell growth and migration in an IGF-dependent manner. ER positive (MCF7L) wild-type, stably expressing AIB1 and scrambled control short hairpin RNA (shAIB1 and shCON) cells were created. Cells were treated for 24h in serum free media plus and minus IGF-I (5nM). Polyribosomal mRNA was stratified using sucrose gradients and fractionated into ten individual fractions and total-RNA samples were obtained. qRT-PCR was performed to determine IGF-I and AIB1 mediated transcriptional and translational effects on AIB1, markers of proliferation (i.e. KI67 and PCNA), cell cycle (i.e. p21), survival (i.e. BCL2), migration (i.e. VEGFA) and ribosome biogenesis factors (i.e. eIF3A and eIF5) in MCF7L shCON and shAIB1 cells. Statistical significance was determined by one-way ANOVA (p&amp;lt;0.05). Total-RNA expression of VEGFA, Ki67, PCNA and eIF5 was induced by IGF-I in the shCON and shAIB1 cells (p&amp;lt;0.05), apart from eIF5 where no induction by IGF-I was detected in the shAIB1 cells. No change in total-RNA expression of AIB1, BCL2, p21 or eIF3A was detected by IGF-I treatment. However, AIB1 and p21 total-RNA expression was reduced under both basal and IGF-I treated conditions in the shAIB1 vs. shCON cells (p&amp;lt;0.05). The percentage of ribosome-bound Ki67, PCNA, p21, VEGFA, and eIF3A mRNA was increased by IGF-I in all ten pooled fractionated RNA samples combined (range: 11% to 340%, mean: 110%), compared to control cells. This effect was either reversed (i.e. Ki67, PCNA and eIF3A), slightly increased (i.e. p21) or unaffected (i.e. VEGFA) in the shAIB1 IGF-I treated vs. control cells. IGF-I treatment reduced ribosome-bound BCL2 (23%) and eIF5 (20%) mRNA in the shCON cells, which was further reduced to 68% and 46% respectively in the shAIB1 cells. We observed a basal reduction of ribosome-bound mRNA for AIB1 (63%), VEGFA (24%), p21 (43%) and eIF3A (37%) and an increase for Ki67 (26%), PCNA (12%), eIF5 (32%) and BCL2 (59%) in the shAIB1 vs. shCON cells. Moreover, all genes had reduced ribosome-bound mRNA following IGF-I treatment in the shAIB1 vs. shCON fractions, except for eIF5 which increased. Our studies demonstrate that IGF-I transcriptionally induces Ki67, PCNA, VEGFA and eIF5 in an AIB1-dependent and independent manner and p21 was only transcriptionally regulated by AIB1. Importantly, IGF-I regulated mRNA ribosome recruitment was predominantly reduced in the AIB1 knock-down cells, indicative of a reduced malignant potential. These findings give preliminary evidence of AIB1 acting as a novel mediator of ribosomal recruitment, which may lead to novel combinatorial therapeutic approaches using AIB1 and translational targeted inhibitors in AIB1 over-expressing breast cancers. 1. Oh, A., et al. Cancer Res, 2004. 15 (64): p.8299-308 2. Lahusen, T., et al. Breast Cancer Res Treat, 2009: 116(2): p.225-37 3. Louie, MC., et al. Mol Cell Biol, 2004: 24(12): p. 5157-71 4. Cole, MD and Cowling VH. Oncogene, 2009: 28: p 1169-1175 Citation Format: Aleksandra M. Ochnik, Mark S. Peterson, Svetlana V. Avdulov, Douglas Yee. AIB1 is a transcriptional and translational mediator of breast cancer cell growth and migration targets. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr B121.

Clinical significance of ERβ mRNA expression in ERα-negative and triple-negative breast cancers.

545 Background: Previously at the 2012 ASCO meeting, we reported significant ERβ mRNA expression in ERα-negative (ERα-) and triple negative breast cancers (TNBC). In this study, we analyzed its clinical outcome and correlation with other clinical parameters. Methods: A total of 141 cases consisted of 69 ERα- BC including 41 TNBC and 72 ERα+ BC were obtained from patients aged 29 to 97 years old between 2003 and 2010. Treatments included surgery, hormone, chemo- or radiotherapy, or any combinations. The follow-up period ranged from 1 to 132 months. ERβ mRNA was analyzed from formalin-fixed tumor tissues by RT-PCR. ERα, PR, Her-2, Ki-67, AIB-1, NFk/p65, p-c-jun, Ki-67, TIF-2, SRC-1, CK5/6 and p53 were tested by immunohistochemistry. The correlation was deemed significant if p value less than 0.05 from Chi-square. Overall survival (SVR) was defined from the date of diagnosis to last follow-up or death attributed to BC and was analyzed by the Kaplan-Meier curves and Wilcoxon rank sum. Results: Single or combination of ERβ isoform(s) was highly expressed in both ERα- and TNBC and ERβ2 was the most frequent (48.8%) and ERβ5, the least (30.2%). In contrast, ERβ5 was the most frequent in ERα+BC. Presence of all or any ERβ isoform was associated with significantly higher SVR in all cases, and in TNBC (ERβ total, Wilcoxon p = 0.0177, ERβ2, p= 0.0329), and also with negative LN (p&lt; 0.0001). ERβ2 and ERβ5 were expressed in 63.2% and 30 %, respectively, in 20 patients died in 1 to 60 months. Over expression of AIB-1, NF-kB/p65 and TIF-2 was associated with ERβ1 and ERβ2 (p&lt;0.05). Ki-67 + cells were mostly ERβ + BC than ERα+. ERα mRNA expression was up-regulated, and ERβ,down- regulated, with the ERα: ERβ+ ratio of 3-1000:1. There was no association between ERβ expression and the stage, age, tumor size, and postmenopausal status. Conclusions: Specific ERβ isoform appears to be a significant discriminating factor for SVR and negative node. ERβ2 is the predominant isoform in ERα- but ERβ5 in ERα+BC, suggesting a distinct role of ERβ isoform in ERα- and ERα+BC. ERβ isoform may be a selective therapeutic target in this cohort. ERβ+/ Ki-67+cells appear to be a sub-population of BC arising from basal-myoepithelial cells in this cohort.

Abstract P6-04-21: AIB1 expression specifically predicts breast cancer patient response to aromatase inhibitor therapy

Abstract Aromatase inhibitors (AI) have evolved over the last decade into an effective therapeutic regime for postmenopausal women with primary or advanced breast cancer. Despite their remarkable success in the clinic, intrinsic resistance to therapy occurs in a proportion of patients, while other patients who respond initially to treatment will relapse with recurrent disease. Previous studies suggest that this may be due, at least in part to estrogen receptor (ER) hypersensitivity. We undertook ER ChIPseq analysis on AI resistant cell model and data for this suggests that ER transcriptional regulation alone may not be responsible for the development of the resistant phenotype. We examined the role of the established ER coactivator protein AIB1. AIB1 has previously been associated with initiation of breast cancer and resistance to endocrine therapy. In tamoxifen treated patients, expression of AIB1 in conjunction with an activated HER2 cascade has been associated with treatment resistance and early disease recurrence. By contrast, we have observed that AIB1 alone can predict response to AIs. In our TMA the expression of AIB1 associated with disease recurrence (p = 0.025) and reduced disease free survival time (p = 0.0471) in patients treated with AIs as first-line therapy. Reflecting increased growth factor activity reported in AI resistance, AIB1 expression associated with the growth factor second messenger signaling proteins, p-Src and pERK1/2, but not the receptor HER2. These results suggest that AIB1 may utilize additional transcription factors other than ER to drive endocrine resistance. Additionally, we show that AIB1 is highly expressed in AI resistant metastases; therefore, monitoring AIB1 expression may be useful to screen for disease progression and detect disease advancement before metastases appear. Our studies of cell line models of AI resistance suggest that AIB1 may play a functional role in aggressive, migratory, phenotype of AI resistance. We have generated cell line models of resistance to letrozole (LetR) and anastrozole (AnaR). Our resistance models have higher levels of AIB1 and have increased migratory capacity. Interestingly, knockdown of AIB1 reduces the migratory capacity of the resistant cells. Furthermore, we have observed that AIB1 regulation of ER target genes is selectively enhanced in AI resistant cells in a promoter specific context. AIB1 recruitment to ER target genes such as pS2 and Myc becomes insensitive to letrozole. By contrast, AIB1 recruitment to cyclinD1 retained letrozole sensitivity. Our evidence suggests that steroidal regulation of transcription factors such as Jun and Fos may contribute to this promoter-specific regulation of ER target genes. We establish a role for AIB1 in AI-resistant breast cancer and describe a new mechanism of ERalpha/AIB1 gene regulation which could contribute to the development of an aggressive tumour phenotype. We provide evidence of a central role for AIB1 in regulating selective ER transcriptional activity and driving tumour recurrence in AI treated patients. Tackling the emerging problem of AI resistance in a timely fashion will enable us to tailor existing therapies and improve outcome in specific patient groups before disease recurrence becomes a clinical issue. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-04-21.

AIB1:ERα Transcriptional Activity Is Selectively Enhanced in Aromatase Inhibitor–Resistant Breast Cancer Cells

The use of aromatase inhibitors (AI) in the treatment of estrogen receptor (ER)-positive, postmenopausal breast cancer has proven efficacy. However, inappropriate activation of ER target genes has been implicated in the development of resistant tumors. The ER coactivator protein AIB1 has previously been associated with initiation of breast cancer and resistance to endocrine therapy. Here, we investigated the role of AIB1 in the deregulation of ER target genes occurring as a consequence of AI resistance using tissue microarrays of patients with breast cancer and cell line models of resistance to the AI letrozole. Expression of AIB1 associated with disease recurrence (P = 0.025) and reduced disease-free survival time (P = 0.0471) in patients treated with an AI as first-line therapy. In a cell line model of resistance to letrozole (LetR), we found ERα/AIB1 promoter recruitment and subsequent expression of the classic ER target genes pS2 and Myc to be constitutively upregulated in the presence of both androstenedione and letrozole. In contrast, the recruitment of the ERα/AIB1 transcriptional complex to the nonclassic ER target cyclin D1 and its subsequent expression remained sensitive to steroid treatment and could be inhibited by treatment with letrozole. Molecular studies revealed that this may be due in part to direct steroid regulation of c-jun-NH(2)-kinase (JNK), signaling to Jun and Fos at the cyclin D1 promoter. This study establishes a role for AIB1 in AI-resistant breast cancer and describes a new mechanism of ERα/AIB1 gene regulation which could contribute to the development of an aggressive tumor phenotype.

P4-01-15: Alteration of Y-box Binding Protein-1 Expression Modifies the Response to Endocrine Therapy in Estrogen Receptor Positive Breast Cancer.

Abstract Y-box binding protein-1 (YB-1) plays an important role in tumor progression and drug resistance. This study examined whether YB-1 is involved in the alteration of response to endocrine therapy in ER-positive breast cancer cells. MCF7 cells that stably expressed YB-1 (MCF7-YB-1) and vector control cells (MCF7-vector) were established. These cells were used to analyze the expression of the factors related to the ER and growth factor receptor signaling pathways, response to the antiestrogens (tamoxifen and fulvestrant), and estrogen responsive element (ERE) activity. The effect of knocking down endogenous YB-1 expression was tested in wild-type MCF7 cells. In addition, the expression of the YB-1 and the factors related to the ER and growth factor receptor signaling pathways were evaluated in the clinical breast cancers treated with preoperative chemotherapy. The expression of HER2, AIB1, p-Erk and c-Myc were increased in the MCF7-YB-1 cells. In contrast, knocking down of YB-1 decreased the expression of these factors, but increased the expression of ERα in the wild-type MCF7 cells. Furthermore, sensitivity to antiestrogens was decreased in the MCF7-YB-1 in comparison to those in the MCF7-vector cells. In the MCF7-YB-1 cells, the expression levels of p-Erk and c-Myc were continuously upregulated when the cells were treated either with tamoxifen or fulvestrant. The ERE activity was decreased in the MCF7-YB-1 cells in comparison to the MCF7-vector cells, and the ERE activity of the MCF7-YB-1 cells was inhibited by fulvestrant at a lower concentration than that which inhibited the ERE activity of the MCF7-vector cells. In the ER-positive clinical breast cancers treated with preoperative chemotherapy, significantly more of the specimens that showed increased or positive nuclear YB-1 expression after the chemotherapy were positive for HER2 expression. These data suggest that alteration of YB-1 may modify the crosstalk between the ER pathway and HER2 pathway in ER-positive breast cancer cells, and consequently may alter the response to endocrine therapy in these cells. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-15.

AIB1 as an Independent Prognostic Marker in Hepatocellular Carcinoma After Hepatic Resection

BackgroundAmplified in breast cancer 1 (AIB1) has been shown to promote growth and invasion in several types of human cancers and to have a prognostic role in some of cancers. However, its prognostic significance in hepatocellular carcinoma (HCC) remains unknown. This study aimed to address the issue. MethodsImmunohistochemical staining of AIB1 was performed for HCC and paired paratumorous liver (PTL) tissues from 139 patients. Associations between AIB1 expression with clinicopathological variables and patient survival were evaluated. ResultsThe expression rate of AIB1 was significantly higher in HCC (71/139, 51.1%) than in PTL tissues (1/139, 0.72%, P < 0.001). AIB1 expression in HCC was significantly associated with serum α-fetoprotein levels (P = 0.001) and Edmondson–Steiner grade (P = 0.038). Higher AIB1 expression in HCC was associated with shorter cumulative overall survival of the patients. Multivariate Cox regression analysis revealed that AIB1 was of independent prognostic significance for HCC. ConclusionsAIB1 is independently associated with poor prognosis of HCC.

Alteration of Y-box binding protein-1 expression modifies the response to endocrine therapy in estrogen receptor-positive breast cancer

Y-box binding protein-1 (YB-1) plays an important role in tumor progression and drug resistance. This study examined whether YB-1 is involved in the alteration of response to endocrine therapy in estrogen receptor (ER)-positive breast cancer cells. MCF7 cells that stably expressed YB-1 (MCF7-YB-1) and vector control cells (MCF7-vector) were established. These cells were used to analyze the expression of the factors related to ER and growth factor receptor signaling pathways and responses to antiestrogens (tamoxifen and fulvestrant) and estrogen responsive element (ERE) activity. The effect of knocking down endogenous YB-1 expression was tested in wild-type MCF7 cells. In addition, the expression of YB-1 and the factors related to ER and growth factor receptor signaling pathways were evaluated in clinical breast cancers treated with preoperative chemotherapy. The expression of HER2, AIB1, p-Erk, and c-Myc was increased in MCF7-YB-1 cells. In contrast, knocking down of YB-1 decreased the expression of these factors but increased the expression of ERα in wild-type MCF7 cells. Furthermore, sensitivity to antiestrogens was decreased in the MCF7-YB-1 in comparison to that in MCF7-vector cells. The introduction of YB-1 into MCF7 cells inhibited apoptosis and cell cycle arrest at G1 phase induced by antiestrogens. In MCF7-YB-1 cells, the expression levels of p-Erk and c-Myc were continuously upregulated when cells were treated with either tamoxifen or fulvestrant. The ERE activity was reduced in MCF7-YB-1 cells in comparison to MCF7-vector cells, and the ERE activity in MCF7-YB-1 cells was inhibited by fulvestrant at a lower concentration than that which inhibited the ERE activity in MCF7-vector cells. In ER-positive clinical breast cancers treated with preoperative chemotherapy, significantly more number of specimens that showed increased or positive YB-1 expression after chemotherapy was positive for HER2 expression. These data suggest that alteration of YB-1 may modify the crosstalk between the ER pathway and HER2 pathway in ER-positive breast cancer cells, and consequently, may alter the response to endocrine therapy in ER-positive breast cancer cells.

Prognostic value of novel biomarkers in astrocytic brain tumors: nuclear receptor co-regulators AIB1, TIF2, and PELP1 are associated with high tumor grade and worse patient prognosis

Estrogen receptors alpha (ERα) and beta (ERβ) and their co-regulatory proteins are key components of complex signaling networks that specifically regulate the growth and development of various tissues and tumors. Still, their protein expression profiles and possible role in the pathogenesis of astrocytic tumors remain largely unknown. The purpose of the present study is to evaluate the differential protein expression of ΕRα, ERβ, and their co-activators, AIB1, TIF2, and PELP1 in astrocytic tumors of World Health Organization (WHO) grade II-IV, using immunohistochemistry. Potential correlations with clinicopathological parameters and patient prognosis were also explored. ERα protein expression was undetectable while ERβ levels were significantly decreased with progression of tumor grade (P < 0.001). High expression of ERβ was an independent favorable prognostic factor on multivariate analysis (P = 0.003). Expression of AIB1, TIF2, and PELP1 was not correlated with ERβ expression and followed an opposite trend, with increasing levels in high-grade relative to low-grade tumors (P < 0.001). Univariate survival analysis revealed that high AIB1, TIF2, and PELP1 expression was associated with worse prognosis (P = 0.049, P = 0.033, and P = 0.020, respectively). ERβ and ER co-activators AIB1, TIF2, and PELP1 appear to play an important role in the pathogenesis and progression of astrocytic tumors and might have prognostic significance. The mechanisms underlying their involvement in astrocytic tumorigenesis, as well as their utility for prognostic and therapeutic purposes merit further investigation.

The p160 ER co-regulators predict outcome in ER negative breast cancer

The SRC family of ER co-regulators are frequently overexpressed in breast cancer. Overexpression of AIB1 appears to be linked to hormone resistance in HER2 positive breast cancer. However, the role of these co-regulators in ER negative disease is poorly understood. SRC1, SRC2 and AIB1 expression was determined by immunohistochemical analysis of tissue microarrays constructed from tumours within the Edinburgh Breast Conservation Series (BCS). The BCS represents a fully documented consecutive cohort of 1,812 patients treated by breast conservation surgery in a single institution. Our results demonstrate tumours that overexpress both HER2 and AIB1 were associated with markedly reduced relapse free, distant relapse free and overall survival compared to HER2 and AIB1 only overexpressing tumours irrespective of ER status. In ER negative disease both SRC1 and AIB1 were linked to early relapse and death. The SRC family of ER co-regulators is involved in early relapse and resistance in both ER negative and ER positive breast cancer challenging the conventional concept that this effect is mediated solely via the ER.

Abstract P5-03-08: Overexpression of AIB1 mRNA in Breast Cancer Inversely Correlates with Estrogen Receptor Positivity

Abstract Background: The AIB1 is a steroid receptor coactivator that promotes the transcriptional activity of nuclear receptors such as estrogen receptor. It is overexpressed at the mRNA level in up to 60% of primary breast carcinomas. Methods: In situ hybridization to examine AIB1 mRNA expression was performed in 113 breast carcinomas in the Catholic university of Korea, from Jan. 2004 to Dec. 2008. We investigated the prognostic significance of AIB1 and the correlation of immunohistochemical staining results of estrogen receptor(ER), progesterone receptor (PR), and Her2/neu. Results: AIB1 mRNA overexpression showed in 55 of 113 (48.7%) breast carcinomas. AIB1 mRNA expression was significantly associated with T stage (P=0.002), but not associated with age, lymph node metastasis, histologic type and histologic grade. High expression of AIB1 mRNA was inversely correlated with expression of ER (P=0.011, R=-0.241) and not significantly associated, but also adversely related, with expression of PR (P=0.101, R=-0.157). AIB1 mRNA overexpression was associated with positivity of Her2/neu (P=0.001, R= 0.311). Survival and recurrent free analysis did not reveal significant association with AIB1 expression. Conclusion: AIB1 mRNA overexpression could be involved in breast cancer by mechanism not totally dependent on steroid receptor cofactor, and may involved other estrogen independent growth pathway such as Her2/neu expression. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-03-08.

Upregulation of AIB1, aromatase and ERα provides long-term estrogen-deprived human breast cancer cells with a mechanistic growth advantage for survival.

To investigate the mechanisms by which breast cancer cells adapt and are able to grow during estrogen deprivation, human estrogen receptor-α (ERα)-positive breast cancer cells stably transfected with the aromatase gene (MCF-7Ca) were cultured in steroid-depleted medium for 6-8months until they started proliferating. Compared with the parental MCF-7Ca cells, long-term estrogen-deprived UMB-1Ca cells exhibited increased aromatase activity (2000%), AIB1 expression (3500%) and ERα expression (100%). When MCF-7Ca cells were isolated from tumors of mice treated for 12months with an aromatase inhibitor, letrozole, ERα was reduced (50%) whereas AIB1 levels were increased (>1000%), suggesting that the mechanism of estrogen deprivation might predetermine the signaling pathway utilized. To a lesser extent long-term estrogen-deprived MCF-7 cells (LTED) displayed an increase in AIB1, ERα and aromatase activity. Consistent with other findings, the growth of the LTED cells was inhibited by estradiol and antiestrogens, whereas the UMB-1Ca cells were slightly stimulated by estradiol and inhibited by antiestrogens and letrozole. In LTED cells treated with estradiol, levels of AIB1 and ERα (95%) were reduced. Interestingly, estradiol treatment caused no change in AIB1 and ERα expression in the UMB-1Ca cells which might explain the differential growth effect of the cells to estradiol. Together, these results demonstrate that estrogen deprivation results in the upregulation of the estrogen signaling pathway at the level of AIB1, ERα and aromatase, which might attenuate ER-mediated transcription representing one mechanism by which tumors adapt to proliferation in a low estrogenic environment.

Abstract 3093: Overexpression of transcriptional coactivator AIB1 promotes hepatocellular carcinoma progression by enhancing cell proliferation and invasiveness

Abstract Amplified in breast cancer 1 (AIB1; SRC-3) is a transcriptional coactivator for nuclear receptors and other transcription factors. AIB1 has been identified to play an important role in malignancy of several cancers such as breast and prostate cancers; however, its involvement in the progression of hepatocellular carcinoma (HCC) remains unclear. The aim of this study is to investigate the expression and possible role of AIB1 in HCC. Western blot analysis revealed that AIB1 was significantly increased in 15 of 22 HCC samples (68%), whereas only trace amounts of AIB1 were detected in the most matched nontumorous liver tissues. Functional studies on HCC cells demonstrated that AIB1 specific small interfering RNA mediated down-regulation of AIB1 resulted in decreased cell proliferation rate, cell migration/invasion ability, colony formation ability, and tumorigenic potential in nude mice. Marked increase of cell cycle inhibitor p21Cip1/Waf1 expression and dramatic decrease of the expression of phosphorylated Akt, proliferating cell nuclear antigen (PCNA), and matrix metallopeptidase MMP-9 in AIB1 knockdown cells contributed to these phenotypic changes. Consistent with these results, clinical AIB1-positive HCC exhibited higher levels of PCNA protein expression compared with AIB1-negative HCC. Further statistical calculation revealed a positive and tight correlation between the levels of AIB1 protein and PCNA protein in HCC, indicating that AIB1 contributes significantly to HCC cell proliferation. Conclusion: our results demonstrate that AIB1 promotes the progression of human HCC by enhancing cell proliferation and invasiveness, and could be a potential therapeutic target molecule for HCC treatment. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3093.

Expression Levels of Co-Regulators in Early Breast Cancer.

Abstract Introduction: The p160 (SRC) family of estrogen receptor (ER) co-activators have important implications in tamoxifen resistance. The SRC family play a central role in ER mediated transcription. There are three family members; SRC-1, SRC-2 and AIB1. AIB1 is amplified in 5-10% of human breast cancers. SRC-1 expression is associated with HER2 expression, increased risk of recurrence and insensitivity to endocrine treatment. Co-factors interact with the ER and basal transcriptional machine to activate or repress ER-mediated transcription. To investigate the role of ER and its co-factors in breast cancer we have carried out quantitative RT-PCR (qRT-PCR) to measure the relative expression of ERa and its co-factors.Methods: In this study we examined patients which were untreated or treated with chemotherapy or hormonal therapy following breast conservation surgery. RNA was extracted from 340 early breast cancer specimens from the Edinburgh Breast Conserving Surgery cohort (BCS). The BCS is a fully documented consectutive cohort of breast cancers treated by conservation surgery, axillary node sampling or clearance, and whole breast radiotherapy between 1981-1998. Clinico-pathological features and complete follow up (duration &amp;gt;10 years) is available for this cohort. qRT-PCR was carried out using primers for ER, SRC-1, SRC-2, AIB1, NCoR1 and SMRT.Results: This study demonstrated SRC-1 expression to be negatively correlated with both SRC-2 and AIB1 expression. SRC-1 expression was also negatively correlated with the co-repressors NCoR1 and SMRT expression. There was a strong correlation between the co-repressors, NCoR1 and SMRT and the co-activators SRC-2 and AIB1. Relapse-free survival (RFS) was estimated using Kaplan-Meier curves. Patients who had high expression of all three co-activators had reduced relapse-free survival (HR: 2.15 95%C.I. 1.175-3.921, p=0.01). No significant association was noted with overall survival. Exploratory subgroup analysis was under powered and showed no significant association with outcome.Conclusion: In conclusion, our study of expression levels of ER and its cofactors by quantitative RT-PCR in breast cancer samples revealed a correlation between the co-factors and co-repressors. These findings would suggest that ER and cofactors may play a synergistic role in the development and progression of breast cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2127.