Co-expression of ErbB-family members in human breast cancer: Her-2/neu is the preferred dimerization candidate in nodal-positive tumors

Clinicopathological and prognostic correlations of HER3 expression and its degradation regulators, NEDD4-1 and NRDP1, in primary breast cancer

Background

Human epidermal growth factor receptor HER3 (ErbB3), especially in association with its relative HER2 (ErbB2), is known as a key oncogene in breast tumour biology. Nonetheless, the prognostic relevance of HER3 remains controversial. NEDD4–1 and NRDP1 are signalling molecules closely related to the degradation of HER3 via ubiquitination. NEDD4–1 and NRDP1 have been reported to contribute to HER3-mediated signalling by regulating its localization and cell membrane retention. We studied correlations between HER3, NEDD4–1, and NRDP1 protein expression and their association with tumour histopathological characteristics and clinical outcomes.

Methods

The prevalence of immunohistochemically detectable expression profiles of HER3 (n = 177), NEDD4–1 (n = 145), and NRDP1 (n = 145) proteins was studied in primary breast carcinomas on archival formalin-fixed paraffin-embedded (FFPE) samples. Clinicopathological correlations were determined statistically using Pearson’s Chi-Square test. The Kaplan-Meier method, log-rank test (Mantel-Cox), and Cox regression analysis were utilized for survival analysis.

Results

HER3 protein was expressed in breast carcinomas without association with HER2 gene amplification status. Absence or low HER3 expression correlated with clinically aggressive features, such as triple-negative breast cancer (TNBC) phenotype, basal cell origin (cytokeratin 5/14 expression combined with ER negativity), large tumour size, and positive lymph node status. Low total HER3 expression was prognostic for shorter recurrence-free survival time in HER2-amplified breast cancer (p = 0.004, p = 0.020 in univariate and multivariate analyses, respectively). The majority (82.8%) of breast cancers demonstrated NEDD4–1 protein expression - while only a minor proportion (8.3%) of carcinomas expressed NRDP1. NEDD4–1 and NRDP1 expression were not associated with clinical outcomes in HER2-amplified breast cancer, irrespective of adjuvant trastuzumab therapy.

Conclusions

Low HER3 expression is suggested to be a valuable prognostic biomarker to predict recurrence in HER2-amplified breast cancer. Neither NEDD4–1 nor NRDP1 demonstrated relevance in prognostics or in the subclassification of HER2-amplified breast carcinomas.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4917-1) contains supplementary material, which is available to authorized users.

Simultaneous Quantitative Detection of Relevant Biomarkers in Breast Cancer by Quantitative Real-Time PCR

The assessment of ERα, PgR and HER2 status is routinely performed today to determine the endocrine responsiveness of breast cancer samples. Such determination is usually accomplished by means of immunohistochemistry and in case of HER2 amplification by means of fluorescent in situ hybridization (FISH). The analysis of these markers can be improved by simultaneous measurements using quantitative real-time PCR (Qrt-PCR). In this study we compared Qrt-PCR results for the assessment of mRNA levels of ERα, PgR, and the members of the human epidermal growth factor receptor family, HER1, HER2, HER3 and HER4. The results were obtained in two independent laboratories using two different methods, SYBR Green I and TaqMan probes, and different primers. By linear regression we demonstrated a good concordance for all six markers. The quantitative mRNA expression levels of ERα, PgR and HER2 also strongly correlated with the respective quantitative protein expression levels prospectively detected by EIA in both laboratories. In addition, HER2 mRNA expression levels correlated well with gene amplification detected by FISH in the same biopsies. Our results indicate that both Qrt-PCR methods were robust and sensitive tools for routine diagnostics and consistent with standard methodologies. The developed simultaneous assessment of several biomarkers is fast and labor effective and allows optimization of the clinical decision-making process in breast cancer tissue and/or core biopsies.

H3K4 acetylation, H3K9 acetylation and H3K27 methylation in breast tumor molecular subtypes

Aim: Here, we investigated how the St Gallen breast molecular subtypes displayed distinct histone H3 profiles. Patients & methods: 192 breast tumors divided into five St Gallen molecular subtypes (luminal A, luminal B HER2-, luminal B HER2+, HER2+ and basal-like) were evaluated for their histone H3 modifications on gene promoters. Results: ANOVA analysis allowed to identify specific H3 signatures according to three groups of genes: hormonal receptor genes (ERS1, ERS2, PGR), genes modifying histones (EZH2, P300, SRC3) and tumor suppressor gene (BRCA1). A similar profile inside high-risk cancers (luminal B [HER2+], HER2+ and basal-like) compared with low-risk cancers including luminal A and luminal B (HER2-) were demonstrated. Conclusion: The H3 modifications might contribute to clarify the differences between breast cancer subtypes.

High-level ERBB2 gene amplification is associated with a particularly short time-to-metastasis, but results in a high rate of complete response once trastuzumab-based therapy is offered in the metastatic setting

Despite patient selection based on ERBB2 overexpression, not all patients benefit from trastuzumab therapy. We have investigated whether a ERBB2 gene dosage effect might provoke increased biological aggressiveness and altered trastuzumab sensitivity. Absolute ERBB2 copy numbers ("CN") and ERBB2/centromer 17 ratios ("R") were measured by FISH analysis in tumors of 127 patients receiving trastuzumab-based treatment for Her-2/neu overexpressing metastatic breast cancer. CN and R were both significantly associated with shorter time to first metastasis (TTM) (CN: OR: 1.099, 95% CI: 1.042-1.159; R: OR: 1.211, 95% CI: 1.080-1.357) and longer PFS (CN: OR: 0.917, 95% CI: 0.867-0.969; R: OR: 0.840, 95% CI: 0.743-0.949) in a continuous variable Cox's regression model. Tumors with ERBB2/centromer 17 ratios of <2.2 had a significantly shorter TTM (p = 0.002) and significantly longer PFS (p = 0.003) than tumors with low-level (R: 2.2-6) and high-level amplification (R: >6). Interestingly, when ERBB2 copy numbers were analyzed, a significantly shorter TTM (p = 0.001) and longer PFS (p = 0.026) were observed in the group with high-level amplified CN (CN: >13), while no difference was observed between non- and low-level amplified CN. R, but not CN, was an independent predictor of complete (CR; OR: 1.685; 95% CI: 1.122-2.532) and partial (PR; OR: 1.704; 95% CI: 1.136-2.556) response in logistic regression analysis. CR (p = 0.016) rates were significantly higher in the high-level amplification group (R > 6), but no difference existed in response rates between non- and low-level amplified tumors in Chi-square tests. High-level ERBB2 amplification is associated with shorter TTM, but improved response to trastuzumab in metastatic breast cancer.

Potential use of humanized antibodies in the treatment of breast cancer

With the growing knowledge of key cellular pathways in tumor induction and evolution, targeted therapies make up an increasing proportion of new drugs entering clinical testing. In the treatment of breast cancer, humanized antibodies have become a major option. The humanized monoclonal antibody trastuzumab (Herceptin); Genentech, Inc., CA, USA) for HER2-overexpressing, metastatic breast cancer, represents a successful agent associated with impressive survival benefits when combined with chemotherapy. Based on impressive results, trastuzumab will become a standard in the adjuvant treatment of HER2-overexpressing breast cancer. The role of trastuzumab in the neoadjuvant setting is promising, but must be further evaluated in large prospective, randomized trials. However, there is still a large proportion of patients overexpressing HER2 that do not respond to trastuzumab. Regarding this patient cohort, the optimal combination of trastuzumab with other agents needs further evaluation. In breast cancer lacking HER2 amplification, the role of the new antibody pertuzumab remains to be defined. The role of antibodies interfering with angiogenesis, tumor stroma or glycoproteins is of a preliminary nature and warrants further investigation. Here, an overview of humanized antibodies in human breast cancer is provided, with emphasis on the recent advances and future prospects in treating malignant breast cancer.

Do type 1 receptor tyrosine kinases inform treatment choice? A prospectively planned analysis of the TEAM trial

BACKGROUND

Epidermal growth factor receptors contribute to breast cancer relapse during endocrine therapy. Substitution of aromatase inhibitors (AIs) may improve outcomes in HER-positive cancers.

METHODS

Tissue microarrays were constructed. Quantitative analysis of HER1, HER2, and HER3 was performed. Data were analysed relative to disease-free survival and treatment using outcomes at 2.75 and 6.5 years.

RESULTS

Among 4541 eligible samples, 4225 (93%) had complete HER1-3 data. Overall, 5% were HER1-positive, 13% HER2-positive, and 21% HER3-positive; 32% (n=1351) overexpressed at least one HER receptor. In the HER1-3-negative subgroup, the hazard ratio (HR) for upfront exemestane vs tamoxifen at 2.75 years was 0.67 (95% confidence interval (CI), 0.52-0.87), in the HER1-3-positive subgroup, the HR was 1.15 (95% CI, 0.85-1.56). A prospectively planned treatment-by-marker analysis demonstrated a significant interaction between HER1-3 and treatment at 2.75 years (HR=0.58; 95% CI, 0.39-0.87; P=0.008), as confirmed by multivariate regression analysis adjusting for prognostic factors (HR=0.55; 95% CI, 0.36-0.85; P=0.005). This effect was time dependent.

CONCLUSION

In the 2.75 years prior to switching patients initially treated with tamoxifen to exemestane, a significant treatment-by-marker effect exists between AI/tamoxifen treatment and HER1-3 expression, suggesting HER expression could be used to select appropriate endocrine treatment at diagnosis to prevent or delay early relapses.

ANALYSIS OF BREAST CANCER PROFILES USING BAYESIAN NETWORK MODELING

Breast cancer is the leading cause of cancer-related death for women in Tunisia and the prognosis of its metastasis remains a major problem for oncologists despite advances in treatment. In this work we use Bayesian networks to develop a decision support system that is based on the modeling of relationships between key signaling proteins and clinical and pathological characteristics of breast tumors and patients. Motivated by the lack of prior information on the parameters of the problem, we use the Implicit inference for the structure and parameter learning. A dataset of 84 Tunisian breast cancer patients was used and new prognosis factors were identified. The system predicts a metastasis risk for different patients by computing a score that is the joint probability of the Bayesian network using parameters estimated on the learning database. Based on the results of the developed system we identified that overexpression of ErbB2, ErbB3, bcl2 as well as of oestrogen and progesterone receptors associated with a low level of ErbB4 was the predominant profile associated with high risk of metastasis.

Genome wide proteomics of ERBB2 and EGFR and other oncogenic pathways in inflammatory breast cancer

In this study we selected three breast cancer cell lines (SKBR3, SUM149 and SUM190) with different oncogene expression levels involved in ERBB2 and EGFR signaling pathways as a model system for the evaluation of selective integration of subsets of transcriptomic and proteomic data. We assessed the oncogene status with reads per kilobase per million mapped reads (RPKM) values for ERBB2 (14.4, 400, and 300 for SUM149, SUM190, and SKBR3, respectively) and for EGFR (60.1, not detected, and 1.4 for the same 3 cell lines). We then used RNA-Seq data to identify those oncogenes with significant transcript levels in these cell lines (total 31) and interrogated the corresponding proteomics data sets for proteins with significant interaction values with these oncogenes. The number of observed interactors for each oncogene showed a significant range, e.g., 4.2% (JAK1) to 27.3% (MYC). The percentage is measured as a fraction of the total protein interactions in a given data set vs total interactors for that oncogene in STRING (Search Tool for the Retrieval of Interacting Genes/Proteins, version 9.0) and I2D (Interologous Interaction Database, version 1.95). This approach allowed us to focus on 4 main oncogenes, ERBB2, EGFR, MYC, and GRB2, for pathway analysis. We used bioinformatics sites GeneGo, PathwayCommons and NCI receptor signaling networks to identify pathways that contained the four main oncogenes and had good coverage in the transcriptomic and proteomic data sets as well as a significant number of oncogene interactors. The four pathways identified were ERBB signaling, EGFR1 signaling, integrin outside-in signaling, and validated targets of C-MYC transcriptional activation. The greater dynamic range of the RNA-Seq values allowed the use of transcript ratios to correlate observed protein values with the relative levels of the ERBB2 and EGFR transcripts in each of the four pathways. This provided us with potential proteomic signatures for the SUM149 and 190 cell lines, growth factor receptor-bound protein 7 (GRB7), Crk-like protein (CRKL) and Catenin delta-1 (CTNND1) for ERBB signaling; caveolin 1 (CAV1), plectin (PLEC) for EGFR signaling; filamin A (FLNA) and actinin alpha1 (ACTN1) (associated with high levels of EGFR transcript) for integrin signalings; branched chain amino-acid transaminase 1 (BCAT1), carbamoyl-phosphate synthetase (CAD), nucleolin (NCL) (high levels of EGFR transcript); transferrin receptor (TFRC), metadherin (MTDH) (high levels of ERBB2 transcript) for MYC signaling; S100-A2 protein (S100A2), caveolin 1 (CAV1), Serpin B5 (SERPINB5), stratifin (SFN), PYD and CARD domain containing (PYCARD), and EPH receptor A2 (EPHA2) for PI3K signaling, p53 subpathway. Future studies of inflammatory breast cancer (IBC), from which the cell lines were derived, will be used to explore the significance of these observations.

Overexpression of CD44 accompanies acquired tamoxifen resistance in MCF7 cells and augments their sensitivity to the stromal factors, heregulin and hyaluronan

Background

Acquired resistance to endocrine therapy in breast cancer is a significant problem with relapse being associated with local and/or regional recurrence and frequent distant metastases. Breast cancer cell models reveal that endocrine resistance is accompanied by a gain in aggressive behaviour driven in part through altered growth factor receptor signalling, particularly involving erbB family receptors. Recently we identified that CD44, a transmembrane cell adhesion receptor known to interact with growth factor receptors, is upregulated in tamoxifen-resistant (TamR) MCF7 breast cancer cells. The purpose of this study was to explore the consequences of CD44 upregulation in an MCF7 cell model of acquired tamoxifen resistance, specifically with respect to the hypothesis that CD44 may influence erbB activity to promote an adverse phenotype.

Methods

CD44 expression in MCF7 and TamR cells was assessed by RT-PCR, Western blotting and immunocytochemistry. Immunofluorescence and immunoprecipitation studies revealed CD44-erbB associations. TamR cells (± siRNA-mediated CD44 suppression) or MCF7 cells (± transfection with the CD44 gene) were treated with the CD44 ligand, hyaluronon (HA), or heregulin and their in vitro growth (MTT), migration (Boyden chamber and wound healing) and invasion (Matrigel transwell migration) determined. erbB signalling was assessed using Western blotting. The effect of HA on erbB family dimerisation in TamR cells was determined by immunoprecipitation in the presence or absence of CD44 siRNA.

Results

TamR cells overexpressed CD44 where it was seen to associate with erbB2 at the cell surface. siRNA-mediated suppression of CD44 in TamR cells significantly attenuated their response to heregulin, inhibiting heregulin-induced cell migration and invasion. Furthermore, TamR cells exhibited enhanced sensitivity to HA, with HA treatment resulting in modulation of erbB dimerisation, ligand-independent activation of erbB2 and EGFR and induction of cell migration. Overexpression of CD44 in MCF7 cells, which lack endogenous CD44, generated an HA-sensitive phenotype, with HA-stimulation promoting erbB/EGFR activation and migration.

Conclusions

These data suggest an important role for CD44 in the context of tamoxifen-resistance where it may augment cellular response to erbB ligands and HA, factors that are reported to be present within the tumour microenvironment in vivo. Thus CD44 may present an important determinant of breast cancer progression in the setting of endocrine resistance.

Steroid receptor coactivators, HER-2 and HER-3 expression is stimulated by tamoxifen treatment in DMBA-induced breast cancer

Background

Steroid receptor coactivators (SRCs) may modulate estrogen receptor (ER) activity and the response to endocrine treatment in breast cancer, in part through interaction with growth factor receptor signaling pathways. In the present study the effects of tamoxifen treatment on the expression of SRCs and human epidermal growth factor receptors (HERs) were examined in an animal model of ER positive breast cancer.

Methods

Sprague-Dawley rats with DMBA-induced breast cancer were randomized to 14 days of oral tamoxifen 40 mg/kg bodyweight/day or vehicle only (controls). Tumors were measured throughout the study period. Blood samples and tumor tissue were collected at sacrifice and tamoxifen and its main metabolites were quantified using LC-MS/MS. The gene expression in tumor of SRC-1, SRC-2/transcription intermediary factor-2 (TIF-2), SRC-3/amplified in breast cancer 1 (AIB1), ER, HER-1, -2, -3 and HER-4, as well as the transcription factor Ets-2, was measured by real-time RT-PCR. Protein levels were further assessed by Western blotting.

Results

Tamoxifen and its main metabolites were detected at high concentrations in serum and accumulated in tumor tissue in up to tenfolds the concentration in serum. Mean tumor volume/rat decreased in the tamoxifen treated group, but continued to increase in controls. The mRNA expression levels of SRC-1 (P = 0.035), SRC-2/TIF-2 (P = 0.002), HER-2 (P = 0.035) and HER-3 (P = 0.006) were significantly higher in tamoxifen treated tumors compared to controls, and the results were confirmed at the protein level using Western blotting. SRC-3/AIB1 protein was also higher in tamoxifen treated tumors. SRC-1 and SRC-2/TIF-2 mRNA levels were positively correlated with each other and with HER-2 (P ≤ 0.001), and the HER-2 mRNA expression correlated with the levels of the other three HER family members (P < 0.05). Furthermore, SRC-3/AIB1 and HER-4 were positively correlated with each other and Ets-2 (P < 0.001).

Conclusions

The expression of SRCs and HER-2 and -3 is stimulated by tamoxifen treatment in DMBA-induced breast cancer. Stimulation and positive correlation of coactivators and HERs may represent an early response to endocrine treatment. The role of SRCs and HER-2 and -3 should be further studied in order to evaluate their effects on response to long-term tamoxifen treatment.

Discovery and validation of breast cancer early detection biomarkers in preclinical samples

Despite the widespread use of mammography for breast cancer screening, breast cancer remains the most common cause of cancer-related mortality among women worldwide. The identification of blood-based biomarkers useful for the early detection of breast cancer could have a major impact on reducing breast cancer disease burden by identifying cancers early when they are most treatable. We conducted a series of large-scale proteomic discovery and validation studies using preclinical samples from the Women's Health Initiative Observational Study prospective cohort. Of the 503 proteins quantified in experiments conducted on samples from ER(+) breast cancer patients and matched controls, 57 differentiated cases from controls. The seven candidates were assessed in an independent validation set with a commercially available ELISA assay. We confirmed that one of these candidates, epidermal growth factor receptor (EGFR), was elevated in cases versus controls. Compared to women in the lowest EGFR quartile, those in the highest quartile has a 2.90-fold (p = 0.0005) increased risk of developing breast cancer. An interaction with use of menopausal hormone therapy was observed such that among current estrogen plus progestin users, those in the highest EGFR quartile had a 9.04-fold (p = 0.0004) increased risk of developing breast cancer. While the performance of EGFR in terms of sensitivity and specificity is insufficient for it to be used on its own clinically, the formal validation of EGFR suggests that there may indeed be changes in the plasma proteome prior to the clinical diagnosis of breast cancer that are detectable and of potential clinical utility.

Characterization of ubiquitination dependent dynamics in growth factor receptor signaling by quantitative proteomics

Protein ubiquitination is a dynamic reversible post-translational modification that plays a key role in the regulation of numerous cellular processes including signal transduction, endocytosis, cell cycle control, DNA repair and gene transcription. The conjugation of the small protein ubiquitin or chains of ubiquitin molecules of various types and lengths to targeted proteins is known to alter proteins' lifespan, localization and function and to modulate protein interactions. Despite its central importance in various aspects of cellular life and function there are only a limited number of reports investigating ubiquitination on a proteomic scale, mainly due to the inherited complexity and heterogeneity of ubiquitination. We describe here a quantitative proteomics strategy based on the specificity of ubiquitin binding domains (UBDs) and Stable Isotope Labeling by Amino acids in Cell culture (SILAC) for selectively decoding ubiquitination-driven processes involved in the regulation of cellular signaling networks. We applied this approach to characterize the temporal dynamics of ubiquitination events accompanying epidermal growth factor receptor (EGFR) signal transduction. We used recombinant UBDs derived from endocytic adaptor proteins for specific enrichment of ubiquitinated complexes from the EGFR network and subsequent quantitative analyses by high accuracy mass spectrometry. We show that the strategy is suitable for profiling the dynamics of ubiquitination occurring on individual proteins as well as ubiquitination-dependent events in signaling pathways. In addition to a detailed seven time-point profile of EGFR ubiquitination over 30 minutes of ligand stimulation, our data determined prominent involvement of Lysine-63 ubiquitin branching in EGF signaling. Furthermore, we found two centrosomal proteins, PCM1 and Azi1, to form a multi-protein complex with the ubiquitin E3 ligases MIB1 and WWP2 downstream of the EGFR, thereby revealing possible ubiquitination cross-talk between EGF signaling and centrosomal-dependent rearrangements of the microtubules. This is a general strategy that can be utilized to study the dynamics of other cellular systems and post-translational modifications.

Epidermal growth factor and estrogen act by independent pathways to additively promote the release of the angiogenic chemokine CXCL8 by breast tumor cells

The tumor microenvironment contains multiple cancer-supporting factors, whose joint activities promote malignancy. Here, we show that epidermal growth factor (EGF) and estrogen upregulate in an additive manner the transcription and the secretion of the angiogenic chemokine CXCL8 (interleukin 8 [IL-8]) in breast tumor cells. In view of published findings on cross-regulatory interactions between EGF receptors and estrogen receptors in breast tumor cells, we asked whether the additive effects of EGF and estrogen were due to their ability to (1) induce intracellular cross talk and amplify shared regulatory pathways or (2) act in independent mechanisms, which complement each other. We found that stimulation by EGF alone induced the release of CXCL8 through signaling pathways involving ErbB2, ErbB1, Erk, and phosphoinositide 3-kinase (PI3K). ErbB2 and Erk were also involved in estrogen activities on CXCL8 but to a lower extent than with EGF. However, in the joint stimulatory setup, the addition of estrogen to EGF has led to partial (ErbB2, ErbB1, Erk) or complete (PI3K) shutoff of the involvement of these activation pathways in CXCL8 up-regulation. Furthermore, when costimulation by EGF + estrogen was applied, the effects of estrogen were channeled to regulation of CXCL8 at the transcription level, acting through the transcription factor estrogen receptor α (ERα). In parallel, in the joint stimulation, EGF acted independently at the transcription level through AP-1, to upregulate CXCL8 expression. The independent activities of EGF and estrogen on CXCL8 transcription reinforce the need to introduce simultaneous targeting of ErbBs and ERα to achieve effective therapy in breast cancer.

Furanodienone induces cell cycle arrest and apoptosis by suppressing EGFR/HER2 signaling in HER2-overexpressing human breast cancer cells

PURPOSE

Overexpression of EGFR and HER2 is seen in breast cancers and results in poor prognosis and decreased patient survival. Clinically, EGFR and HER2 are effective therapeutic targets. The objective of this study is to investigate the in vitro effects of furanodienone, an active chemical component isolated from Rhizoma Curcumae, on the activation of EGFR/HER2 signaling, cell cycle, and apoptosis in HER2-overexpressing BT474 and SKBR3 cells.

METHODS

Cell growth was assessed by SRB protein assay. Cell cycle analysis was carried out by flow cytometry, and apoptosis was observed by Annexin V and DAPI staining. Effects of furanodienone on the activation of EGFR/HER2 signaling-related proteins were analyzed by western blotting.

RESULTS

Furanodienone inhibited cell growth in BT474 and SKBR3 cells. Furanodienone caused G1 arrest in BT474 cells and induced apoptosis in SKBR3 cells. Furanodienone interfered with EGFR/HER2 signaling in treated cells as shown by decreases in phosphorylated EGFR, HER2, Akt, Gsk3β and an increase in p27(kip1) protein. Accordingly, furanodienone inhibited EGF-induced phosphorylation of EGFR, HER2, Akt, and Gsk3β. EGFR-specific siRNA knockdown did not affect the cell growth inhibitory effect of furanodienone. On the contrary, specific siRNA knockdown of HER2 increased cellular resistance to furanodienone toxicity. In HER-2-deficient MDA-MB-231 cells, the transfection and expression of HER2 increased the sensitivity of cells to furanodienone toxicity.

CONCLUSION

Furanodienone inhibited EGFR/HER2 signaling pathway in BT474 and SKBR3 cells. More importantly, the effect of furanodienone was specifically dependent on HER2, but not EGFR, expression.

Detection of elevated plasma levels of epidermal growth factor receptor before breast cancer diagnosis among hormone therapy users

Applying advanced proteomic technologies to prospectively collected specimens from large studies is one means of identifying preclinical changes in plasma proteins that are potentially relevant to the early detection of diseases such as breast cancer. We conducted 14 independent quantitative proteomics experiments comparing pooled plasma samples collected from 420 estrogen receptor-positive (ER(+)) breast cancer patients ≤17 months before their diagnosis and matched controls. Based on the more than 3.4 million tandem mass spectra collected in the discovery set, 503 proteins were quantified, of which 57 differentiated cases from controls with a P value of <0.1. Seven of these proteins, for which quantitative ELISA assays were available, were assessed in an independent validation set. Of these candidates, epidermal growth factor receptor (EGFR) was validated as a predictor of breast cancer risk in an independent set of preclinical plasma samples for women overall [odds ratio (OR), 1.44; P = 0.0008] and particularly for current users of estrogen plus progestin (E + P) menopausal hormone therapy (OR, 2.49; P = 0.0001). Among current E + P users, the EGFR sensitivity for breast cancer risk was 31% with 90% specificity. Whereas the sensitivity and specificity of EGFR are insufficient for a clinically useful early detection biomarker, this study suggests that proteins that are elevated preclinically in women who go on to develop breast cancer can be discovered and validated using current proteomic technologies. Further studies are warranted to examine the role of EGFR and to discover and validate other proteins that could potentially be used for early detection of breast cancer.

Combined inhibitory effect of formestane and herceptin on a subpopulation of CD44+/CD24low breast cancer cells

In breast cancer, stromal cells surrounding cancer epithelial cells can influence phenotype by producing paracrine factors. Among many mediators of epithelial-stromal interactions, aromatase activity is perhaps one of the best studied. Clinical data suggest that estrogen-independent signaling leads to increased proliferation even during therapy with aromatase inhibitors (AIs). Molecular mechanism of crosstalk between the estrogen receptor (ER) and the epidermal growth factor receptor (HER) family have been implicated in resistance to endocrine therapy, but this interaction is unclear. The ability of aromatase to induce estradiol biosynthesis provides a molecular rationale to combine agents that target aromatase activity and the HER pathway. We targeted stromal-epithelial interactions using formestane, which exerts antiaromatase activity, combined with the monoclonal anti-HER2 antibody herceptin, in a subpopulation of CD44+/CD24low cells sorted from epithelial-mesenchymal co-cultures of breast cancer tissues. The growth inhibition was respectively 16% (P < 0.01) in the response to herceptin, 25% to formestane (P < 0.01), and 50% (P < 0.001) with the combination of the two drugs, suggesting that herceptin cooperates with formestane-induced inhibition of aromatase and this effect could be mediated through HER family receptors. In cells which expressed ERalpha, formestane/herceptin combination suppressed the mRNA expression of aromatase and HER2 and decreased cyclin D1 expression. These results show that combination therapies involving AIs and anti-HER2 can be efficacious for the treatment of cancer in experimental models and suggest that subtyping breast tumors gives useful information about response to treatment.

ErbB2 expression through heterodimerization with erbB1 is necessary for ionizing radiation- but not EGF-induced activation of Akt survival pathway

PURPOSE

ErbB1-dependent Akt phosphorylation improves post-irradiation cellular survival. In the present study, we investigated the contribution of erbB2 as a heterodimerization partner of erbB1 in activation of Akt survival signaling after irradiation or EGF treatment.

MATERIALS AND METHODS

Pattern of receptor dimerization and protein phosphorylation were investigated by Western and immunoblotting as well as immunoprecipitation techniques. Residual DNA double-strand breaks (DNA-DSB) and clonogenic activity were analyzed by γH2AX and standard clonogenic assay. To knocked erbB2 expression siRNA was used.

RESULTS

In lung carcinoma cell lines A549 and H661, the erbB1-tyrosine kinase (TK) inhibitor erlotinib blocked EGF as well as ionizing radiation (IR)-induced Akt and DNA-PKcs phosphorylation. Targeting Akt and erbB1 induced cellular radiation sensitivity while, the erbB2-TK inhibitor AG825 neither affected phosphorylation of Akt and DNA-PKcs nor induced radiosensitization. ErbB2-siRNA and the anti-erbB2 antibody trastuzumab blocked IR-induced, but not EGF-stimulated Akt phosphorylation and impaired the repair of DNA-DSB. Likewise, IR but not EGF enhanced erbB1/erbB2 heterodimerization and resulted in the release of phosphorylated erbB2 cleavage products p135 and p95. Trastuzumab prevented radiation-induced formation of an active erbB1/erbB2 heterodimer and increased cellular radiation sensitivity. ErbB1- but not erbB2-TK inhibition stabilized erbB2 (p185) through preventing its cleavage.

CONCLUSIONS

The data indicates that ErbB2 through heterodimerization with erbB1 is necessary for the activation of Akt signaling following irradiation but not following EGF treatment.

HER1-4 protein concentrations in normal breast tissue from breast cancer patients are expressed by the same profile as in the malignant tissue

BACKGROUND

The epidermal growth factor receptor HER2 is overexpressed or amplified in 25%-30% of patients with breast cancer. The mechanism behind HER2 amplification is unknown, but may be a patho-physiological phenomenon caused by continuous stimulation and activation of the HER1-4 system. We have mapped the protein concentrations of HER1-4 in breast cancer tissue, autologous reference tissue, normal breast tissue and serum samples, to see whether non-cancer cells from these patients express a protein profile indicating general activation.

METHODS

Tissue samples from malignant and adjacent normal breast tissue (autologous reference tissue) were collected from 118 women consecutively admitted for surgical treatment of breast cancer. In addition, 26 samples of normal breast tissue were collected from healthy women having breast reduction surgery. The tissue samples were homogenized and the proteins extracted. The tissue and serum concentrations of HER1-4 were determined quantitatively using a commercially available enzyme linked immunosorbent assay (ELISA) method.

RESULTS

HER1 was down regulated in cancer tissue when compared to autologous reference tissue (p=8 x 10(-6)), while HER2 (p<10(-7)) and HER3 (p=3 x 10(-5)) were up regulated. Comparing autologous reference tissue with normal tissue showed down regulation of HER1 (p=0.122) and up regulation of HER2 (p=10(-6)), HER3 (p<10(-7)) and HER4 (p<10(-7)). Furthermore, we observed that correlations between the receptor combinations HER1-2, HER1-3 and HER1-4 were maintained from normal breast tissue to autologous reference breast tissue, but were lost in cancer tissue.

CONCLUSIONS

We suggest that these findings indicate that breast cancer is a systemic disease where the HER1-4 system in autologous reference tissue is continuously activated, thus favoring the subsequent development of cancer.

Quantitative multiplexed analysis of ErbB family coexpression for primary breast cancer prognosis in a large retrospective cohort

BACKGROUND

Assessment of outcome using a single prognostic or predictive marker is the current basis of targeted therapy, but is inherently limited by its simplicity. Multiplexing has provided better classification, but has only been done quantitatively using RNA or DNA. Automated quantitative analysis is a new technology that allows quantitative in situ assessment of protein expression. The authors hypothesized that multiplexed quantitative measurement of ErbB receptor family proteins may allow better prediction of outcome.

METHODS

The authors quantitatively assessed the expression of 6 proteins in 4 subcellular compartments in 676 patients using breast carcinoma tissue microarrays. Then using Cox proportional hazards modeling and unsupervised hierarchical clustering, they assessed the prognostic value of the expression singly and multiplexed.

RESULTS

Epidermal growth factor receptor (EGFR), HER-2, and HER-3 expression were associated with decreased survival. Multivariate analysis showed high HER-2 and HER-3 expression maintained independence as prognostic markers. Hierarchical clustering of expression data defined a small class enriched for HER-2 expression with 40% 10-year survival, compared with 55% using conventional methods. Clustering also revealed a similarly poor-prognostic subgroup coexpressing EGFR and HER-3 (but low for estrogen receptor, progesterone receptor, and HER-2) with a 42% 10-year survival.

CONCLUSIONS

This work shows that the combined analysis of protein expression improved prognostic classification, and that multiplexed models were superior to any single-marker-based method for prediction of 10-year survival. These methods illustrate a protein-based, multiplexed approach that could more accurately identify patients for targeted therapies.

Therapeutically targeting ErbB3: a key node in ligand-induced activation of the ErbB receptor-PI3K axis

The signaling network downstream of the ErbB family of receptors has been extensively targeted by cancer therapeutics; however, understanding the relative importance of the different components of the ErbB network is nontrivial. To explore the optimal way to therapeutically inhibit combinatorial, ligand-induced activation of the ErbB-phosphatidylinositol 3-kinase (PI3K) axis, we built a computational model of the ErbB signaling network that describes the most effective ErbB ligands, as well as known and previously unidentified ErbB inhibitors. Sensitivity analysis identified ErbB3 as the key node in response to ligands that can bind either ErbB3 or EGFR (epidermal growth factor receptor). We describe MM-121, a human monoclonal antibody that halts the growth of tumor xenografts in mice and, consistent with model-simulated inhibitor data, potently inhibits ErbB3 phosphorylation in a manner distinct from that of other ErbB-targeted therapies. MM-121, a previously unidentified anticancer therapeutic designed using a systems approach, promises to benefit patients with combinatorial, ligand-induced activation of the ErbB signaling network that are not effectively treated by current therapies targeting overexpressed or mutated oncogenes.

Effect of lapatinib on the development of estrogen receptor-negative mammary tumors in mice

Lapatinib, a selective orally available inhibitor of epidermal growth factor receptor (EGFR) and ErbB2 receptor tyrosine kinases, is a promising agent for the treatment of breast cancer. We examined the effect of lapatinib on the development of mammary tumors in MMTV-erbB2 transgenic mice, which express wild-type ErbB2 under the control of the mouse mammary tumor virus promoter and spontaneously develop estrogen receptor (ER)-negative and ErbB2-positive mammary tumors by 14 months of age. Mice were treated from age 3 months to age 15 months with vehicle (n = 17) or lapatinib (30 or 75 mg/kg body weight; n = 16 mice per group) by oral gavage twice daily (6 d/wk). All statistical tests were two-sided. By 328 days after the start of treatment, all 17 (100%) of the vehicle-treated mice vs five (31%) of the 16 mice treated with high-dose lapatinib developed mammary tumors (P < .001). Among MMTV-erbB2 mice treated for 5 months (n = 20 mice per group), those treated with lapatinib had fewer premalignant lesions and noninvasive cancers in their mammary glands than those treated with vehicle (P = .02). Lapatinib also effectively blocked epidermal growth factor-induced signaling through the EGFR and ErbB2 receptors, suppressed cyclin D1 and epiregulin mRNA expression, and stimulated p27 mRNA expression in human mammary epithelial cells and in mammary epithelial cells from mice treated for 5 months with high-dose lapatinib. Thus, cyclin D1, epiregulin, and p27 may represent useful biomarkers of lapatinib response in patients. These data suggest that lapatinib is a promising agent for the prevention of ER-negative breast cancer.

Signal integration: a framework for understanding the efficacy of therapeutics targeting the human EGFR family

The human EGFR (HER) family is essential for communication between many epithelial cancer cell types and the tumor microenvironment. Therapeutics targeting the HER family have demonstrated clinical success in the treatment of diverse epithelial cancers. Here we propose that the success of HER family-targeted monoclonal antibodies in cancer results from their ability to interfere with HER family consolidation of signals initiated by a multitude of other receptor systems. Ligand/receptor systems that initiate these signals include cytokine receptors, chemokine receptors, TLRs, GPCRs, and integrins. We further extrapolate that improvements in cancer therapeutics targeting the HER family are likely to incorporate mechanisms that block or reverse stromal support of malignant progression by isolating the HER family from autocrine and stromal influences.

Prognostic value of protein tyrosine kinase 6 (PTK6) for long-term survival of breast cancer patients

The cytoplasmic tyrosine kinase PTK6 (BRK) shows elevated expression in approximately two-thirds of primary breast tumours, and is implicated in EGF receptor-dependent signalling and epithelial tumorigenesis. Using immunohistochemistry, we performed a retrospective study on 426 archival breast cancer samples from patients with long-term follow-up and compared the protein expression levels of PTK6, the HER receptors, Sam68 (a substrate of PTK6), and signalling proteins including MAP kinase (MAPK), phosphorylated MAPK (P-MAPK), and PTEN. We show that PTK6 expression is of significant prognostic value in the outcome of breast carcinomas. In multivariate analysis, the disease-free survival of patients of >or=240 months was directly associated with the protein expression level of PTK6 (P<or=0.001), but was also inversely associated with nodal status (P<or=0.001) and tumour size (P<or=0.01). PTK6 expression in tumour tissue significantly correlated (P<or=0.05) with the expression of PTEN, MAPK, P-MAPK, and Sam68. To investigate whether these correlations may be due to molecular interactions between PTK6 and these proteins, we used protein extracts from the T47D cell line for immunoprecipitation and western blot analysis. By this, interactions could be demonstrated between PTK6 and MAPK, P-MAPK, HER2/neu, HER3, HER4, PTEN, and Sam68. On the basis of these results, we suggest that PTK6 may serve as a future target for the development of novel treatments in breast cancer.

In vitro expansion of human breast cancer epithelial and mesenchymal stromal cells: optimization of a coculture model for personalized therapy approaches

Molecularly targeted, customized therapies are designed based on the molecular portraits of cancer tissue. The efficacy of targeted therapy in individual patients depends on the contribution of single individual cancer cells within the context of their microenvironment. We have developed an in vitro model of human mammary epithelial-stromal cocultures to answer specific clinical questions related to breast cancer, to provide a tool with which to identify a signature in each breast tumor, and to identify the metabolic molecular targets of therapy in an attempt to optimize the efficacy of targeted therapy in each patient. Fifty-five human breast cancer samples were obtained through surgery. Epithelial and stromal cells were isolated from tissue specimens by differential centrifugation, and cryopreserved. Western blot analysis and RT-PCR were used to identify the tissue-specific expression patterns of cancer cells. Dose-response curves were constructed for the aromatase inhibitor formestane and for herceptin, and a 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide assay was done for combined treatment. We collected and cryopreserved, for future use, viable living cells from 55 breast tumor specimens from which we derived short-term cocultures. The presence of cytokeratins and vimentin was evaluated in 20 samples, and pHER2/neu and aromatase were evaluated in 4 cocultures. Formestane and herceptin had a cumulative growth-inhibitory effect on cocultures expressing epidermal growth factor receptors and aromatase. The in vitro model of human mammary epithelial-stromal cocultures reported herein can be used to examine, and to store, a patient's tumor-derived, living cells that retain the characteristics of the mother-tissue and respond, in vitro, to therapy.

Serum epidermal growth factor receptor and HER2 expression in primary and metastatic breast cancer patients

Background

Breast tissue expression of the ERBB proto-oncogene family has been extensively studied. It was recently shown that expression of epidermal growth factor receptor (EGFR; c-erbB-1) and epidermal growth factor receptor (HER)2 (c-erbB-2) can be detected in the serum of breast cancer patients. The clinical relevance of this has not been fully established.

Methods

EGFR and HER2 immunoassays were conducted in blood from 57 patients in whom paired serum samples were available (from the times of primary and metastatic diagnoses), from 96 primary breast cancer patients and from 49 normal individuals. Of the 57 patients with paired serum samples, paired tissue samples for HER2 expression were available for eight.

Results

Serum levels of EGFR serum levels were significantly higher in normal individuals (median 75.3 ng/ml, range 43.2 to 114.2 ng/ml) than in patients with primary breast cancer (median 59.3 ng/ml, range 21.3 to 94.1 ng/ml; P < 0.001). In the paired serum samples, EGFR levels decreased significantly between the time of primary diagnosis (median 56.3 ng/ml, range 29.1 to 142.7 ng/ml) and metastatic diagnosis (median 30.9 ng/ml, range 10.9 to 106.4 ng/ml; P < 0.001). In six (11%) a change occurred from over-expression (>78 ng/ml) to normal expression. In contrast, no significant difference was seen in HER2 serum levels in normal individuals (median 12.2 ng/ml, range 7.8 to 20.9 ng/ml) and primary breast cancer patients (median 12.5 ng/ml, range 6.9 to 122.2 ng/ml; P = 0.511). However, in the paired serum samples, HER2 levels increased significantly between the time of primary (median 12.2 ng/ml, range 5.7 to 85.0 ng/ml) and metastasis (median 17.7 ng/ml, range 6.3 to 3,337.4 ng/ml; P < 0.001). HER2 over-expression (>15 ng/ml) was observed in 16 out of 57 patients (28%) at primary breast cancer diagnosis and in 31 out of 57 (54%) at metastasis. In 18 patients (32%) HER2 expression changed from normal to over-expression.

Conclusion

Decisions regarding the use of targeted therapies in the metastatic setting are often based on the oncogene expression of the primary tumour. Our results suggest that serum oncogene assessments may be complementary to this and could potentially widen the indications for these beneficial therapies.

Cytogenetic analysis of HER1/EGFR, HER2, HER3 and HER4 in 278 breast cancer patients

INTRODUCTION

The HER (human EGFR related) family of receptor tyrosine kinases (HER1/EGFR (epidermal growth factor receptor)/c-erbB1, HER2/c-erbB2, HER3/c-erbB3 and HER4/c-erbB4) shares a high degree of structural and functional homology. It constitutes a complex network, coupling various extracellular ligands to intracellular signal transduction pathways resulting in receptor interaction and cross-activation. The most famous family member is HER2, which is a target in Herceptin therapy in metastatic status and also in adjuvant therapy of breast cancer in the event of dysregulation as a result of gene amplification and resulting protein overexpression. The HER2-related HER receptors have been shown to interact directly with HER2 receptors and thereby mutually affect their activity and subsequent malignant growth potential. However, the clinical outcome with regard to total HER receptor state remains largely unknown.

METHODS

We investigated HER1-HER4, at both the DNA and the protein level, using fluorescence in situ hybridisation (FISH) probes targeted to all four receptor loci and also immunohistochemistry in tissue microarrays derived from 278 breast cancer patients.

RESULTS

We retrospectively found HER3 gene amplification with a univariate negative impact on disease-free survival (hazard ratio 2.35, 95% confidence interval 1.08 to 5.11, p = 0.031), whereas HER4 amplification showed a positive trend in overall and disease-free survival. Protein expression revealed no additional information.

CONCLUSION

Overall, the simultaneous quantification of HER3 and HER4 receptor genes by means of FISH might enable the rendering of a more precise stratification of breast cancer patients by providing additional prognostic information. The continuation of explorative and prospective studies on all HER receptors will be required for an evaluation of their potential use for specific therapeutic targeting with respect to individualised therapy.

Malignant transformation of mammary epithelial cells increases expression of leptin and leptin receptor

Both normal and malignant mammary tissues have been shown to produce leptin and express leptin receptors. This study compared the expression of leptin and leptin receptor mRNA in a variety of normal and malignant mammary epithelial cell lines and observed that in general the malignant lines expressed higher levels of leptin and leptin receptor mRNA than nonmalignant lines. Furthermore, oncogenic transformation of nonmalignant cell lines increased expression of leptin and leptin receptor, with expression of ErbB2 giving particularly high levels of expression of long-form leptin receptor. In addition, nonmalignant cells exhibited little or no increase in DNA synthesis following leptin treatment, whereas oncogene-transformed cells had increased DNA synthesis in response to leptin. These effects varied among oncogenes, with ErbB2-transformed cells showing particularly high expression of leptin receptor mRNA and high response to leptin.

ErbB/HER ligands in human breast cancer, and relationships with their receptors, the bio-pathological features and prognosis

BACKGROUND

The aim of this study is to provide an expression profile of ErbB/HER ligands in breast cancer. We analysed the relationships with their receptors, the bio-pathological features and prognosis.

PATIENTS AND METHODS

Epidermal growth factor (EGF), transforming growth factor-alpha (TGFalpha), amphiregulin (AREG), betacellulin (BTC), heparin-binding EGF-like growth factor (HB-EGF), epiregulin (EREG) and neuregulins1-4 (NRG1-4) were quantified in 363 tumours by real-time reverse transcription-polymerase chain reaction using TaqMan probes.

RESULTS

Ligands were detected in 80%-96% of the cases, except NRG3 (42%) and EREG (45.5%). At least one ligand was expressed in 304 cases (cut-off: upper quartile). Almost all combinations of receptor and ligand co-expressions were observed, but TGFalpha is preferentially expressed in tumours co-expressing EGFR/HER3, NRG3 in those co-expressing EGFR/HER4, AREG and EREG in those co-expressing HER2/HER4. EGF and AREG were associated with estradiol receptors, small tumour size, low histoprognostic grading, high HER4 levels. TGFalpha, HB-EGF and NRG2 were negatively related to these parameters. In Cox univariate analyses, EGF was a prognostic factor.

CONCLUSION

Our study demonstrates that (i) ErbB/HER ligands, including BTC and EREG, are expressed in most breast cancers; and (ii) TGFalpha, HB-EGF and NRG2 high expressions are related to the biological aggressiveness of the tumours.

Gene copy numbers of HER family in breast cancer

AIM

The aim of the study was to analyze the occurrence of abnormal gene copy numbers of all HER oncogenes and to correlate these alterations to other clinicopathological variables in a consecutive series of 225 breast cancer patients.

METHODS

Gene copy number of HER oncogenes was analyzed with double differential polymerase chain reaction (ddPCR). Statistical analysis was performed with a set of nonparametric tests.

RESULTS

Sixty-five percent of the tumors contained abnormal gene copy number of at least one HER oncogene. Alterations of at least two oncogenes were found in 31% of cases. The correlations between average gene copy numbers (AGCNs) of particular HER oncogenes were much stronger in node positive compared to node-negative tumors. Deletions of EGFR were associated with the lack of steroid hormone receptors. The HER3 and HER4 amplifications were more common in well differentiated tumors.

CONCLUSIONS

Our results indicate a key role of HER heterodimers in tumor progression and confirm earlier data that HER2 is the preferred partner for other HER oncogenes in this process. Deletions of EGFR were associated with unfavorable characteristics, whereas HER3 and HER4 amplifications may be linked with less aggressive phenotypes.

Downregulation of erbB3 abrogates erbB2-mediated tamoxifen resistance in breast cancer cells

Receptor tyrosine kinase activity is essential for erbB2 (HER2/neu) promotion of breast carcinogenesis, metastasis and therapeutic resistance. erbB2 kinase can be activated by dimerization with another erbB receptor, most of which bind ligands. Of these, the erbB2/erbB3 heterodimer is the most potent oncogenic complex. erbB2 reportedly requires erbB3 to promote cellular proliferation, although this may occur without changes in erbB2 tyrosine kinase activity in some model systems. Our investigations focus on the role(s) of erbB3 in erbB2-associated kinase activity and tamoxifen resistance. Using tumor-derived cell lines from wild type rat c-neu transgenic mice and human breast cancers, we demonstrate that erbB3 plays a critical role in the activation of erbB2 tyrosine kinase activity and erbB2-associated tumorigenesis. Mechanistically, downregulation of erbB3 by specific siRNA reduces erbB2 tyrosine phosphorylation, decreases the PI-3K/Akt signaling, and inhibits mammary/breast cancer cell proliferation and colony formation. Specific erbB3 siRNA sensitizes erbB2 transfected MCF-7 cells (MCF-7/erbB2) to tamoxifen-associated inhibition of both cell growth and colony formation and enhances tamoxifen-induced apoptosis, in contrast to control siRNA transfected MCF-7/erbB2 cells which are tamoxifen-resistant. Our data indicates that erbB2/erbB3 heterodimerization is a prerequisite for erbB2 tyrosine kinase activation in mammary/breast cancer cells and that downregulation of erbB3 inhibits erbB2-associated procarcinogenic activity via inactivation of the PI-3K/Akt pathway. Furthermore, erbB3 also contributes to erbB2-mediated tamoxifen resistance and therefore may be a clinically relevant therapeutic target in addition to erbB2.

PTK (protein tyrosine kinase)-6 and HER2 and 4, but not HER1 and 3 predict long-term survival in breast carcinomas

The HER receptors are of therapeutic and prognostic significance in breast cancer, and their function is modulated by cytoplasmic tyrosine kinases like PTK6 (brk). We performed a retrospective study on archival breast cancer samples from patients with long follow-up and compared the protein expression between individual HERs and between HERs and the PTK6. Univariate and multivariate analyses were used to study the prognostic value of parameters. Metastases-free survival of patients for longer than 240 months was inversely associated (P< or =0.05) with nodal status, tumour size, and oestrogen receptor status, but was also directly associated with high protein expression levels of HER4 and PTK6 in Kaplan-Meier analysis. In multivariate analysis for metastases-free survival of >240 months, the stepwise selected parameters were tumour size (relative risk 3.1), PTK6 expression (0.4), and number of positive lymph nodes (1.2). Furthermore, we demonstrated a timedependence of the prognostic value attributed to the parameters. The HER receptors (HER2,4), but not PTK6, were independent prognostic markers for metastases-free survival at 60 months, whereas at 240 months PTK6 is the strongest prognostic marker. We demonstrate that PTK6 is a prognostic marker of metastases-free survival in breast cancer, and is independent of the classical morphological and molecular markers of lymph node involvement, tumour size, and HER2 status.

[177Lu]pertuzumab: experimental therapy of HER-2-expressing xenografts

Pertuzumab (Omnitarg) is a novel antibody against HER-2, domain II. HER-2 is a tyrosine kinase receptor that is overexpressed in several carcinomas, especially breast cancer. Pertuzumab, labeled with the low-energy beta emitter (177)Lu, might be a candidate for targeted radiotherapy of disseminated HER-2-positive micrometastases. The radiolabeled antibody [(177)Lu]pertuzumab showed favorable targeting properties in BALB/c (nu/nu) mice with HER-2-overexpressing xenografts. The absorbed dose in tumors was more than five times higher than the absorbed dose in blood and more than seven times the absorbed dose in any other normal organ. Experimental therapy showed that [(177)Lu]pertuzumab delayed tumor progression compared with controls (no treatment, P < 0.0001; nonlabeled pertuzumab antibody, P < 0.0001; and (177)Lu-labeled irrelevant antibody, P < 0.01). No adverse side effects of the treatment could be detected. Thus, the experimental results support the planning of clinical studies applying [(177)Lu]pertuzumab for therapy.

Her-2 targeted therapy: beyond breast cancer and trastuzumab

Her-2 is a validated therapeutic target in breast cancer. The two critical questions that remain regarding Her-2 targeting concern 1) the relevance of Her-2 inhibition in other malignancies and 2) the ability of novel agents to achieve greater Her-2 inhibition than trastuzumab. The contribution of cell signaling effects and immunologic mechanisms to the effect of trastuzumab in vivo remains poorly understood. Thus, the preclinical data that support the greater efficacy of novel Her-2 antibodies or small molecule tyrosine kinase inhibitors remain to be validated in clinical trials. In this review, we discuss the evidence from recent trastuzumab clinical trials as a point of departure for consideration of novel Her-2 targeted therapies. Preliminary results from early clinical trials suggest that Her-2 tyrosine kinase inhibitors may extend the population for which this strategy offers therapeutic effect.

Her-2/neu and EGFR tyrosine kinase activation predict the efficacy of trastuzumab-based therapy in patients with metastatic breast cancer

Her-2/neu overexpression in human breast cancer leads to an aggressive biological behavior and poor prognosis. Although the anti-Her-2/neu antibody trastuzumab (Herceptin(R)) has become a valuable therapeutic option for patients with Her-2/neu-overexpressing breast cancer, many patients do not benefit from this therapy. To evaluate the effect of receptor activation on tumor response, we have investigated the phosphorylation status of Her-2/neu and EGFR in 46 Her-2/neu-overexpressing tumor samples from trastuzumab-treated metastatic breast cancer patients by immunohistochemistry. Activated (p)tyr-1248 Her-2/neu was detected in 9 of 46 breast cancers (20%), and activated (p)tyr-845 and (p)tyr-1173 EGFR were both present in 6 tumors (13%) while EGFR was present in 16 cases (35%). ptyr-1248 Her-2/neu showed a trend to correlate with increased response to trastuzumab (p = 0.063), while ptyr-845, ptyr-1173 EGFR and EGFR did not. The presence of ptyr-1248 Her-2/neu and ptyr-845 or ptyr-1173 EGFR, however, was a strong predictor of both response to trastuzumab-based treatment (OR = 8.0, p = 0.021 and OR = 8.0, p = 0.021) and clinical benefit (OR = 5.47, p = 0.041 and OR = 6.22, p = 0.028 multivariate logistic regression analysis). Furthermore, ptyr-845 EGFR and ptyr-1248 Her-2/neu were both independent predictors of progression-free survival (RR = 0.21, p = 0.01 and RR = 0.45, p = 0.026, multivariate analysis). Patients with ptyr-845 EGFR positive tumors also tended toward increased overall survival (RR = 0.17, p = 0.082). Taken together, we have demonstrated that the determination of activated EGFR improves the utility of ptyr-1248 Her-2/neu staining in predicting the clinical outcome of patients undergoing trastuzumab treatment. We hypothesize that the activation state of both Her-2/neu and EGFR are key determinants for trastuzumab efficacy.

Proteomic analysis in human breast cancer: Identification of a characteristic protein expression profile of malignant breast epithelium

Gene expression analysis has become a promising tool in predicting the clinical course of malignant disease and the response to antineoplastic therapy. Surprisingly, only little is known about the protein expression pattern of human tumors. Recent advances in proteomic analysis allow proteins of interest to be identified by their expression and/or modification pattern in 2-DE rather than using the traditional approach of translating gene expression data. To identify a proteomic pattern that is characteristic for malignant breast epithelium, we performed differential 2-DE analysis in sets of microdissected malignant breast epithelia and corresponding adjacent normal breast epithelia from five patients with invasive breast carcinoma. Thirty-two protein spots were found to be selectively regulated in malignant epithelium, and were subjected to MALDI-TOF and/or immunoblotting for protein identification. Thirteen of the identified proteins had previously not been associated with breast cancer. The validity of these findings was confirmed by literature review and immunohistochemistry for identified proteins in an independent cohort of 50 breast cancer specimens. We here describe, for the first time, a proteomic analysis of matched normal and malignant epithelia from invasive breast carcinomas. This strategy leads to a better understanding of oncogenesis at an operational level and helps to characterize the malignant phenotype of individual tumors, and thereby to identify novel targets for antineoplastic therapy.

Prostatic intraepithelial neoplasia and adenocarcinoma in mice expressing a probasin-Neu oncogenic transgene

NEU (ERBB2) and other members of the epidermal growth factor receptor (EGFR) family have been implicated in human prostate cancer (CAP) development and progression to an androgen-independent state, but the extent of involvement and precise role of this signaling pathway remain unclear. To begin addressing such open questions in an animal model, we have developed a transgenic line in which an oncogenic Neu cDNA (Neu*) driven by the probasin gene promoter is overexpressed in the mouse prostate and causes development of prostatic intraepithelial neoplasia (PIN) that progresses to invasive carcinoma. Expression profiling using microarrays, which was selectively validated and extended by immunophenotyping of Neu*-induced PIN and CAP, led to the identification of some novel biomarkers and also revealed increased expression of Egfr, Erbb3 and phosphorylated androgen receptor. In view of this information from our mouse model, which can be used to analyze further the role of Erbb signaling in prostatic tumorigenesis, we examined human prostate cancer tissue arrays by immunohistochemistry. Based on statistical analyses of the results, we propose the testable hypothesis that ERBB3, shown to be expressed in 86% of the human CAP cases that we examined, is the pivotal element of the Erbb pathway promoting tumorigenesis by heterodimerization with NEU or EGFR, while a NEU/EGFR dimer does not appear to play a significant role in CAP.

Serum EGFR levels and efficacy of trastuzumab-based therapy in patients with metastatic breast cancer

The antibody trastuzumab inhibits signal transduction in Her-2/neu overexpressing human breast cancer. However, the activation of co-expressed EGFR has also been show to additionally modulate the anti-tumoural effects of this drug. Similar to Her-2/neu, the extra cellular binding region of EGFR is believed to be proteolytically released from the cell surface upon receptor activation and can be detected in patients' serum (sEGFR). Considering the biological significance of an interaction between EGFR and Her-2/neu signalling in other human malignancies, we have investigated if trastuzumab treatment would affect sEGFR in 33 patients with Her-2/neu overexpressing metastatic breast cancer. We detected EGFR expression in 33% of Her-2/neu overexpressing breast tumours. In contrast to serum Her-2/neu (ECD) levels, which were correlated with the degree of Her-2/neu expression (P=0.048, Mann-Whitney test), we did not detect significant differences between sEGFR serum levels in EGFR expressing or non-expressing tumours. Furthermore, sEGFR serum levels were not correlated with clinical parameters such as response or clinical benefit rates, and no association was found between increased sEGFR levels and progression-free survival or overall survival. While we have previously observed a selective and significant decrease of ECD levels in patients who derived a clinical benefit from trastuzumab treatment during the first weeks of treatment, we were unable to find similar alterations in sEGFR concentrations. We therefore conclude that the measurement of systemic sEGFR levels in addition to ECD serum concentrations do not allow the prediction of clinical course of trastuzumab-treated patients more accurately.

Cooperative interactions of HER-2 and HPV-16 oncoproteins in the malignant transformation of human mammary epithelial cells

To better understand the mechanisms of transformation by the oncogene HER-2, we transduced the human mammary epithelial (HME) cell line MCF-10A with HER-2 and developed a cell line that appeared to moderately overexpress HER-2. These MCF-10HER-2 cells were unable to grow in the absence of epidermal growth factor (EGF). However, coexpression of HER-2 with the HPV-16 oncoproteins E6 and E7 resulted in EGF-independent cells that expressed very high levels of constitutively activated HER-2. Interestingly, coexpression of E7 with HER-2 resulted in cells that were EGF-independent for growth but did not express HER-2 to high levels, and coexpression of E6 with HER-2 resulted in cells expressing higher levels of HER-2, which were still dependent on EGF for growth and survival. The MCF-10HER-2E7 and HER-2/E6E7 cells exhibited constitutive activation of a form of epidermal growth factor receptor (EGFR) that had a faster electrophoretic mobility than EGFR activated by exogenous growth factors. Exposure of cells with EGFR activation to ZD1839 (Iressa), at concentrations specific for EGFR, had little or no influence on proliferation of cells with amplified HER-2 but little or no EGFR. These results indicate that HER-2, E6, and E7 cooperate with endogenous EGFR to yield fully transformed cells.

Blockade of epidermal growth factor receptors chemosensitizes breast cancer cells through up-regulation of Bnip3L

Epidermal growth factor receptor-1 (EGFR) and EGFR-2 (HER2) have become major targets for cancer treatment. Blocking antibodies and small-molecule inhibitors are being used to silence the activity of these receptors in different tumors with varying efficacy. Thus, a better knowledge on the signaling pathways activated by EGFR and HER2 may help unravel novel therapeutic targets and molecular markers of response. Here, we show that treatment of breast cancer cell lines with blocking antibodies against EGFR (cetuximab) or HER2 (trastuzumab) promotes the specific induction of proapoptotic Bnip3L and chemosensitization. Moreover, we found that the Bnip3L gene is transcriptionally activated by FoxO3a. Trastuzumab-mediated induction of Bnip3L and nuclear translocation of FoxO3a was also shown in pleural effusion cells from a breast cancer patient. Transfection of breast cancer cells with constitutively active FoxO3a or with Bnip3L promotes sensitization to chemotherapy-induced apoptosis. On the contrary, blockade of Bnip3L expression by a small interfering RNA strategy significantly diminished the chemosensitizing effect of cetuximab. We found also an inverse correlation between EGFR and Bnip3L expression in surgical specimens from patients with breast cancer. Therefore, blockading EGFR or HER2 specifically up-regulates Bnip3L, which is required for chemosensitization of breast cancer cells. This novel pathway provides also the rationale for therapeutic strategies aimed to induce the expression of Bnip3L.

Zinc finger transcription factors designed for bispecific coregulation of ErbB2 and ErbB3 receptors: insights into ErbB receptor biology

Signaling through the ErbB family of tyrosine kinase receptors in normal and cancer-derived cell lines contributes to cell growth and differentiation. In this work, we altered the levels of ErbB2 and ErbB3 receptors, individually and in combination, by using 6-finger and 12-finger synthetic zinc finger protein artificial transcription factors (ATFs) in an epidermoid squamous cell carcinoma line, A431. We successfully designed 12-finger ATFs capable of coregulating ErbB3 and ICAM-1 or ErbB2 and ErbB3. With ATFs, the effects of changes in ErbB2 and ErbB3 receptor levels were evaluated by using cell proliferation, cell migration, and cell signaling assays. Cell proliferation was increased when ErbB2 and ErbB3 were both overexpressed. Cell migration on collagen was decreased when ErbB2 was down-regulated, yet migration on laminin was significantly increased with ErbB3 overexpression. ErbB2 and ErbB3 overexpression also stimulated the phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathways. Our ATF approach has elucidated differences in ErbB receptor-mediated proliferation, migration, and intracellular signaling that cannot be explained merely by the presence or absence of particular ErbB receptors and emphasizes the dynamic nature of the ErbB signaling system. The transcription factor approach developed here provides a gene-economical route to the regulation of multiple genes and may be important for complex gene therapies.

Trastuzumab: updates and future issues

Trastuzumab has had an enormous impact on the clinical management of breast cancer: the survival of Her-2-positive metastatic breast cancer patients has improved significantly and tumor Her-2 status has been built into the decision-making tree for primary breast cancer patients. Several pioneering studies have shown that trastuzumab-combined chemotherapy elicits high levels of pathological complete response in the neoadjuvant setting. Currently, therefore, a more precise understanding of the mechanisms of therapeutic response is needed so that trastuzumab-based therapies can be optimized more individually. It might also be important to investigate, with greater depth, the interaction between the Her-axis and the hormone-axis. This short review describes and discusses these topics.

Coexpression of the type 1 growth factor receptor family members HER-1, HER-2, and HER-3 has a synergistic negative prognostic effect on breast carcinoma survival

BACKGROUND

The clinical significance of coexpression of type 1 growth factor receptor (T1GFR) family members remains largely unknown. The objective of the current study was to determine the frequency and the possible prognostic effect of coexpression of HER-1, HER-2, HER-3, and HER-4 by breast carcinoma.

METHODS

Tissue microarrays were constructed using clinically annotated formalin-fixed, paraffin-embedded tumor samples from 242 patients with invasive breast carcinomas with a median 15-year follow-up. The levels of TIGFR family members (HER-1-HER-4) were measured by immunohistochemistry. K-means clustering algorithm, as well as univariate (Kaplan-Meier, log-rank test) and multivariate (Cox regression) survival analyses were applied to the data set.

RESULTS

Using univariate analysis, expression of HER-1, HER-2, and HER-3, but not HER-4, was significantly associated with decreased patient disease-specific survival (P < 0.05). Kaplan-Meier survival analysis showed that coexpression of >/= 2 of HER-1, HER-2, and HER-3 in any combination was associated with reduced patient disease-specific survival compared with single marker expression or no expression (35% vs. 65% vs. 78% 10-year survival rates, P = 0.001). Using multivariate analysis, expression of >/= 2 of HER-1, HER-2, and HER-3 was independent of lymph node status and tumor size.

CONCLUSIONS

In a cohort of patients with breast carcinoma, the authors observed T1GFR family member coexpression (HER-1, HER-2, and HER-3) to have a negative synergistic effect on patient outcome, independent of tumor size or lymph node status. Thus, coexpression of T1GFR family members identified a subset of patients with a poor disease prognosis who may potentially benefit from therapy simultaneously targeting several T1GFR family members.

ErbB-receptors expression and survival in breast carcinoma: A 15-year follow-up study

Aberrant expression of the epidermal growth factor receptor family has been implicated in the pathogenesis and progression of breast cancer and associated with poor prognosis. To evaluate the prognostic impact of the ErbB receptors expression profile, we analyzed a well-characterized series of 145 primary breast carcinomas for the simultaneous expression of epidermal growth factor receptor (EGFR/HER-1), ErbB-2 (HER-2), ErbB-3 (HER-3), and ErbB-4 (HER-4), using immunohistochemistry. Tumors were considered negative or positive for each marker when less than or more than 25% of the cancer cells were immunopositive. Expression of EGFR, ErbB-2, ErbB-3, and ErbB-4 was observed in 31 (21.4%), 65 (44.8%), 72 (49.7%), and 81 (55.9%) of the cases, respectively. There were significant associations between EGFR expression and pT status (P = 0.01), and between ErbB-3 expression and pN (P = 0.003), menopausal (P = 0.01) and PR (P < 0.001) status. The majority of the cases co-expressed two or more receptors. ErbB-3 resulted positive in 51/81 (63.0%) of the ErbB-4 positive cases and ErbB-3/ErbB-4 co-expression was statistically significant (P = 0.0003). As expected, ErbB-2 expression was associated with reduced overall survival at 15 years of follow-up (P = 0.04), even after adjusting for a series of other prognostic factors (P = 0.05). Moreover, cumulative analysis of ErbB-2/3/4 expression showed a strong positive association between higher total ErbB-2/3/4 expression score and worse prognosis (P = 0.002). The simultaneous expression in cancer cells of more than one ErbB receptor identifies a subset of breast cancer patients at high risk for poor survival.