HER2 shedding and serum HER2 extracellular domain: Biology and clinical utility in breast cancer

A prospective study to assess the clinical utility of serum HER2 extracellular domain in breast cancer with HER2 overexpression

Purpose

We explored the clinical utility of human epidermal growth factor receptor-2 extracellular domain (HER2/ECD) in patients treated for an invasive breast cancer with HER2 overexpression.

Methods

We prospectively studied HER2/ECD levels in the sera of 334 women included between 2007 and 2014, all treated with trastuzumab. HER2/ECD levels were measured at diagnosis, during treatments, and along the follow-up. We investigated the relationship of HER2/ECD with other clinicopathological parameters at diagnosis, its prognosis value, and its utility during the monitoring of a neoadjuvant treatment and the follow-up.

Results

Elevated HER2/ECD at diagnosis correlated positively with parameters associated with tumor aggressiveness. Disease-free survival of non-metastatic patients was significantly shorter in patients with high HER2/ECD at diagnosis (HR = 13.6, 95 % CI 1.6–113.6, P < 0.0001). Progression-free survival of metastatic patients was better for patients with low HER2/ECD (HR = 2.6, 95 % CI 1.2–5.3, P = 0.033). A multivariate analysis revealed that HER2/ECD level at diagnosis was an independent prognosis factor. During neoadjuvant therapy, a significant decrease in HER2/ECD was reported only for the complete histological response group (P = 0.031). During the follow-up, HER2/ECD helped predict relapse, disease progression, and metastases before imaging in 18.6 % cases of the studied cohort.

Conclusions

HER2/ECD is a prognosis factor that is valuable in evaluating the neoadjuvant treatment efficiency. HER2/ECD also appears to be a helpful surveillance biomarker for the early diagnosis of relapses and to predict the fate of metastases. This study brings evidences to support the use of HER2/ECD in the management of HER2-positive breast cancer.

Improved decision making for prioritizing tumor targeting antibodies in human xenografts: Utility of fluorescence imaging to verify tumor target expression, antibody binding and optimization of dosage and application schedule

Preclinical efficacy studies of antibodies targeting a tumor-associated antigen are only justified when the expression of the relevant antigen has been demonstrated. Conventionally, antigen expression level is examined by immunohistochemistry of formalin-fixed paraffin-embedded tumor tissue section. This method represents the diagnostic "gold standard" for tumor target evaluation, but is affected by a number of factors, such as epitope masking and insufficient antigen retrieval. As a consequence, variances and discrepancies in histological staining results can occur, which may influence decision-making and therapeutic outcome. To overcome these problems, we have used different fluorescence-labeled therapeutic antibodies targeting human epidermal growth factor receptor (HER) family members and insulin-like growth factor-1 receptor (IGF1R) in combination with fluorescence imaging modalities to determine tumor antigen expression, drug-target interaction, and biodistribution and tumor saturation kinetics in non-small cell lung cancer xenografts. For this, whole-body fluorescence intensities of labeled antibodies, applied as a single compound or antibody mixture, were measured in Calu-1 and Calu-3 tumor-bearing mice, then ex vivo multispectral tumor tissue analysis at microscopic resolution was performed. With the aid of this simple and fast imaging method, we were able to analyze the tumor cell receptor status of HER1-3 and IGF1R, monitor the antibody-target interaction and evaluate the receptor binding sites of anti-HER2-targeting antibodies. Based on this, the most suitable tumor model, best therapeutic antibody, and optimal treatment dosage and application schedule was selected. Predictions drawn from obtained imaging data were in excellent concordance with outcome of conducted preclinical efficacy studies. Our results clearly demonstrate the great potential of combined in vivo and ex vivo fluorescence imaging for the preclinical development and characterization of monoclonal antibodies.

High-MET status in non-small cell lung tumors correlates with receptor phosphorylation but not with the serum level of soluble form

OBJECTIVES

The receptor tyrosine kinase MET is essential to embryonic development and organ regeneration. Its deregulation is associated with tumorigenesis. While MET gene amplification and mutations leading to MET self-activation concern only a few patients, a high MET level has been found in about half of the non-small cell lung cancers (NSCLCs) tested. How this affects MET activation in tumors is unclear. Also uncertain is the prognostic value, in cancer, of a phenomenon well described in cell models: MET shedding, i.e. its cleavage by membrane proteases leading to release of a soluble fragment into the medium.

MATERIALS AND METHODS

A prospective cohort of 39 NSCLC patients was constituted at diagnosis or soon after. Normal tissues, tumor tissues, and blood samples were obtained. This allowed, for the same patient, synchronous determination of (i) the MET level in the tumor, (ii) receptor phosphorylation, and (iii) the concentration of soluble MET fragment (sMET) in the serum.

RESULTS

After confirming the adequacy of an ELISA for measuring the serum level of sMET, we found no correlation between this level and the concentration of MET in tumors, as evaluated by immunohistochemistry and western blotting. Nevertheless, all but one tumor displaying a high MET level also displayed receptor phosphorylation, restricted to a small number of tumor cells.

CONCLUSION

Our results thus demonstrate that the serum level of sMET is not indicative of the amount of MET present in the tumor cells and cannot be used as a biomarker for therapeutic purposes. However, MET scoring of tumor biopsies could be a first step prior to determination of MET receptor activation in high-MET tumors.

Serum HER2 extra-cellular domain, S100ß and CA 15-3 levels are independent prognostic factors in metastatic breast cancer patients

Background

Metastatic breast cancer (MBC) prognosis is highly variable, depending on various factors such as the biological subtype, the performance status, disease extension…. A better evaluation of a patient’s prognostic factors could allow for a more accurate choice of treatments. The role of serum tumor markers remains, however, unclear in this population. Considering the recent interest in phenotypic changes and tumor heterogeneity during breast cancer progression, additional tumor markers could be interesting in this setting.

Methods

Two hundred fifty MBC patients treated at the Montpellier Cancer Institute (2008–2015) were retrospectively selected, based on the availability of frozen serum samples. The usual MBC clinical and pathological variables were collected, altogether with Cancer Antigen 15-3 (CA15-3), Carcinoembryonic Antigen (CEA), HER2 extra-cellular domain (ECD), Neuron Specific Enolase (NSE), S100ß protein and Matrix Metalloproteinase 9 (MMP-9) serum levels in order to determine their prognostic value.

Results

With a median follow-up of 40.8 months, median overall survival was 16.2 months (95 % CI 12.4–20.6). In multivariate analysis, the performance status, brain or subcutaneous metastases, the number of previous metastatic chemotherapy lines and the tumor biological subtype were independent prognostic factors. Elevated CA 15-3 (HR = 1.95, IC 95 % 1.31–2.93, p = 0.001), HER2 ECD (regardless of tumor HER2 status, HR = 2.51, IC 95 % 1.53–4.12, p < 0.001) and S100ß (HR = 1.93, IC 95 % 1.05–3.54, p = 0.033) serum levels were independently associated with a poor outcome.

Conclusions

Serum CA 15-3, HER2 ECD and S100ß could represent useful independent prognostic factors in MBC. Of particular interest is the independent value of serum HER2 ECD levels, regardless of the tumor HER2 status, possibly linked to metastatic tumor heterogeneity.

Immuno-Positron Emission Tomography with Zirconium-89-Labeled Monoclonal Antibodies in Oncology: What Can We Learn from Initial Clinical Trials?

Selection of the right drug for the right patient is a promising approach to increase clinical benefit of targeted therapy with monoclonal antibodies (mAbs). Assessment of in vivo biodistribution and tumor targeting of mAbs to predict toxicity and efficacy is expected to guide individualized treatment and drug development. Molecular imaging with positron emission tomography (PET) using zirconium-89 (⁸⁹Zr)-labeled monoclonal antibodies also known as ⁸⁹Zr-immuno-PET, visualizes and quantifies uptake of radiolabeled mAbs. This technique provides a potential imaging biomarker to assess target expression, as well as tumor targeting of mAbs. In this review we summarize results from initial clinical trials with ⁸⁹Zr-immuno-PET in oncology and discuss technical aspects of trial design. In clinical trials with ⁸⁹Zr-immuno-PET two requirements should be met for each ⁸⁹Zr-labeled mAb to realize its full potential. One requirement is that the biodistribution of the ⁸⁹Zr-labeled mAb (imaging dose) reflects the biodistribution of the drug during treatment (therapeutic dose). Another requirement is that tumor uptake of ⁸⁹Zr-mAb on PET is primarily driven by specific, antigen-mediated, tumor targeting. Initial trials have contributed toward the development of ⁸⁹Zr-immuno-PET as an imaging biomarker by showing correlation between uptake of ⁸⁹Zr-labeled mAbs on PET and target expression levels in biopsies. These results indicate that ⁸⁹Zr-immuno-PET reflects specific, antigen-mediated binding. ⁸⁹Zr-immuno-PET was shown to predict toxicity of RIT, but thus far results indicating that toxicity of mAbs or mAb-drug conjugate treatment can be predicted are lacking. So far, one study has shown that molecular imaging combined with early response assessment is able to predict response to treatment with the antibody-drug conjugate trastuzumab-emtansine, in patients with human epithelial growth factor-2 (HER2)-positive breast cancer. Future studies would benefit from a standardized criterion to define positive tumor uptake, possibly supported by quantitative analysis, and validated by linking imaging data with corresponding clinical outcome. Taken together, these results encourage further studies to develop ⁸⁹Zr-immuno-PET as a predictive imaging biomarker to guide individualized treatment, as well as for potential application in drug development.

Meaningful interpretation of serum HER2 ECD levels requires clear patient clinical background, and serves several functions in the efficient management of breast cancer patients

BACKGROUND

This study was initiated to evaluate the clinical significant of HER2 extracellular domain (ECD) in the real-time management of breast cancer patients.

METHODS

Five-hundred forty-six eligible breast cancer patients were divided according to their clinical background. The correlation between ECD, tissue HER2, and clinical outcome of the patients were analyzed.

RESULTS

Receiver operating characteristic analysis revealed that ECD measured before receiving neoadjuvant therapy yielded the highest area under the curve (0.9185; P<0.0001), indicating that ECD and tissue HER2 levels are consistent in untreated tumor-bearing patients. At cut-off of 15.0ng/ml, the prognostic value of ECD was demonstrated using univariate (HR=1.664, P<0.0001) and multivariate (HR=1.547, P=0.011) Cox regression analysis. Kaplan-Meier survival curves revealed that patients with elevated ECD had shorter progression-free survival (PFS) (4.0 vs. 6.1months, P<0.0001). Elevated ECD was also an adverse predictor for PFS in response to anti-HER2 therapy (4.3 vs. 10.2months, P=0.0155). In contrast, ≥20%, decreased ECD was associated with longer PFS in patients who received anti-HER2 therapy (10.9 vs. 2.4months, P=0.0164) and overall (10.7 vs. 2.8months, P=0.0034).

CONCLUSIONS

A patient's clinical history can help determine whether ECD could provide added value for breast cancer management.

Homogeneous Protein Analysis by Magnetic Core-Shell Nanorod Probes

Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.

Enfortumab Vedotin Antibody-Drug Conjugate Targeting Nectin-4 Is a Highly Potent Therapeutic Agent in Multiple Preclinical Cancer Models

The identification of optimal target antigens on tumor cells is central to the advancement of new antibody-based cancer therapies. We performed suppression subtractive hybridization and identified nectin-4 (PVRL4), a type I transmembrane protein and member of a family of related immunoglobulin-like adhesion molecules, as a potential target in epithelial cancers. We conducted immunohistochemical analysis of 2,394 patient specimens from bladder, breast, lung, pancreatic, ovarian, head/neck, and esophageal tumors and found that 69% of all specimens stained positive for nectin-4. Moderate to strong staining was especially observed in 60% of bladder and 53% of breast tumor specimens, whereas the expression of nectin-4 in normal tissue was more limited. We generated a novel antibody-drug conjugate (ADC) enfortumab vedotin comprising the human anti-nectin-4 antibody conjugated to the highly potent microtubule-disrupting agent MMAE. Hybridoma (AGS-22M6E) and CHO (ASG-22CE) versions of enfortumab vedotin (also known as ASG-22ME) ADC were able to bind to cell surface-expressed nectin-4 with high affinity and induced cell death in vitro in a dose-dependent manner. Treatment of mouse xenograft models of human breast, bladder, pancreatic, and lung cancers with enfortumab vedotin significantly inhibited the growth of all four tumor types and resulted in tumor regression of breast and bladder xenografts. Overall, these findings validate nectin-4 as an attractive therapeutic target in multiple solid tumors and support further clinical development, investigation, and application of nectin-4-targeting ADCs. Cancer Res; 76(10); 3003-13. ©2016 AACR.

Monitoring serum HER2 levels in breast cancer patients

Background

We have developed a new approach to reduce the serum interference for ELISA. The purpose of this study is to investigate if we can use the optimized ELISA (MBB-ELISA) to detect serum soluble HER2/neu (sHER2) in early stage primary breast cancer and monitor its change during treatments.

Findings

We collected sera preoperatively from 118 primary breast cancer patients. Serum samples were also collected sequentially from a subset of patients during and after adjuvant treatment. sHER2 in these samples was measured by the MBB-ELISA. Only 16.7 % of tissue HER2 (tHER2) positive patients had significantly elevated sHER2 levels in serum. Interestingly, sera of some patients with tHER2 negative tumors, including those that were 2+ by IHC but negative by FISH, demonstrated slightly elevated sHER2 levels. Multivariate analysis demonstrated that patients with elevated sHER2 (> = 7 ng/ml) had significantly worse disease free survival. During treatments, sHER2 levels consistently fell in response to adjuvant therapies. Nevertheless, in all 4 patients who developed metastases, a steady rise in sHER2 levels was noted before metastatic disease became clinically evident.

Conclusions

For early stage breast cancers, sHER2 is a poor biomarker to predict tHER2 status, but may have value to supplement tissue tests to identify patients with HER2 tumors. Our results also suggest that sHER2 is worth further study as a biomarker to monitor breast cancer patients during treatments.

Antitumor immunization of mothers delays tumor development in cancer-prone offspring

Maternal immunization is successfully applied against some life-threatening infectious diseases as it can protect the mother and her offspring through the passive transfer of maternal antibodies. Here, we sought to evaluate whether the concept of maternal immunization could also be applied to cancer immune-prevention. We have previously shown that antibodies induced by DNA vaccination against rat Her2 (neu) protect heterozygous neu-transgenic female (BALB-neuT) mice from autochthonous mammary tumor development. We, herein, seek to evaluate whether a similar maternal immunization can confer antitumor protection to BALB-neuT offspring. Significantly extended tumor-free survival was observed in BALB-neuT offspring born and fed by mothers vaccinated against neu, as compared to controls. Maternally derived anti-neu immunoglobulin G (IgG) was successfully transferred from mothers to newborns and was responsible for the protective effect. Vaccinated mothers and offspring also developed active immunity against neu as revealed by the presence of T-cell-mediated cytotoxicity against the neu immunodominant peptide. This active response was due to the milk transfer of immune complexes that were formed between the neu extracellular domain, shed from vaccine-transfected muscle cells, and the anti-neu IgG induced by the vaccine. These findings show that maternal immunization has the potential to hamper mammary cancer in genetically predestinated offspring and to develop into applications against lethal neonatal cancer diseases for which therapeutic options are currently unavailable.

Pertuzumab in combination with trastuzumab and docetaxel for HER2-positive metastatic breast cancer

Overexpression of HER2 - found in approximately 15-20% of all breast cancers - is a negative prognostic factor. Although trastuzumab significantly improves the prognosis of HER2-positive breast cancer, half of the patients with metastatic breast cancer experience disease progression within 1 year. Pertuzumab is a novel HER2-targeted humanized monoclonal antibody that binds to the dimerization domain of HER2 and acts synergically with trastuzumab in inhibiting tumor progression. The CLEOPATRA trial demonstrated that adding pertuzumab to trastuzumab plus docetaxel significantly prolonged progression-free survival and overall survival without increasing severe adverse events. Conclusively, pertuzumab was approved by the US FDA in June 2012 for use in combination with trastuzumab and docetaxel for the treatment of patients with HER2-positive metastatic breast cancer. Furthermore, various clinical trials to evaluate the efficacy and safety of pertuzumab combined with other cytotoxic agents are ongoing at present. Thus, pertuzumab has been becoming important for the treatment of patients with HER2-positive metastatic breast cancer.

The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web

The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies. Despite the advances, cases of drug resistance and recurrence of disease still remain a challenge to overcome. An important aspect for drug resistance is the complexity of the HER2 signaling network. This includes the crosstalk between HER2 and hormone receptors; its function as a transcription factor; the regulation of HER2 by protein-tyrosine phosphatases and a complex network of positive and negative feedback-loops. This review summarises the current knowledge of many different HER2 interactions to illustrate the complexity of the HER2 network from the transcription of HER2 to the effect of its downstream targets. Exploring the novel avenues of the HER2 signaling could yield a better understanding of treatment resistance and give rise to developing new and more effective therapies.

HER2 as a therapeutic target in head and neck squamous cell carcinoma

The majority of patients with head and neck squamous cell carcinoma (HNSCC) present with advanced-stage disease. The current standard of care is surgery followed by adjuvant radiotherapy with or without chemotherapy or chemoradiation alone. The addition of cetuximab for the treatment of patients with locally advanced or recurrent/metastatic HNSCC has improved overall survival and locoregional control; however, responses are often modest, and treatment resistance is common. A variety of therapeutic strategies are being explored to overcome cetuximab resistance by blocking candidate proteins implicated in resistance mechanisms such as HER2. Several HER2 inhibitors are in clinical development for HNSCC, and HER2-targeted therapy has been approved for several cancers. This review focuses on the biology of HER2, its role in cancer development, and the rationale for clinical investigation of HER2 targeting in HNSCC.

Serum HER2 levels and HER2 status in tumor cells in advanced gastric cancer patients

OBJECTIVE

Increased serum human epidermal growth factor receptor 2 levels have been found in metastatic breast cancer patients and are correlated with human epidermal growth factor receptor 2 overexpression in tumor cells. However, the prevalence of serum human epidermal growth factor receptor 2 in gastric cancer patients has not been elucidated.

METHODS

We retrospectively analyzed formalin-fixed paraffin-embedded tumor tissues and serum samples from 96 advanced gastric cancer patients. Human epidermal growth factor receptor 2 expression and gene amplification in tumor cells were determined by immunohistochemistry and fluorescence in situ hybridization. Serum human epidermal growth factor receptor 2 levels were measured using a chemiluminescent immunoassay. Human epidermal growth factor receptor 2 positivity in tumor cells was defined as immunohistochemistry 2+ with fluorescence in situ hybridization positive or immunohistochemistry 3+ with any fluorescence in situ hybridization results.

RESULTS

All tissue samples and serum samples were successfully measured. Nineteen patients (20%) were human epidermal growth factor receptor 2-positive in tumor cells. The median serum human epidermal growth factor receptor 2 level was 9.3 ng/ml (range, 5.0-332.4 ng/ml), and serum human epidermal growth factor receptor 2 levels were significantly separated according to human epidermal growth factor receptor 2 status in tumor cells (P < 0.0001, Wilcoxon's rank sum test); median serum human epidermal growth factor receptor 2 levels in human epidermal growth factor receptor 2-negative patients and -positive patients were 8.9 (range, 5.0-20.5) and 24.0 (range, 9.7-332.4), respectively. There were 15 serum human epidermal growth factor receptor 2-positive patients (16%) using a cutoff value of 15 ng/ml. The sensitivity and the specificity of serum human epidermal growth factor receptor 2 with respect to human epidermal growth factor receptor 2 positivity in tumor cells were 53 and 94%, respectively.

CONCLUSIONS

Serum human epidermal growth factor receptor 2 measurements cannot be substituted for tissue human epidermal growth factor receptor 2 diagnosis in advanced gastric cancer patients. However, serum human epidermal growth factor receptor 2 levels are associated with human epidermal growth factor receptor 2 overexpression in tumor cells. Further investigations of clinical significance of serum human epidermal growth factor receptor 2 as a predictive marker and a therapy-monitoring marker are warranted.

Circulating Her-2/neu extracellular domain in breast cancer patients-correlation with prognosis and clinicopathological parameters including steroid receptor, Her-2/neu receptor coexpression

HER-2/neu extracellular domain (ECD) can be detected in blood as a soluble circulating protein. The aim of this study was to analyze the relationship between HER-2/neu extracellular domain in the serum and the prognosis in breast cancer patients. We also correlated HER-2/neu ECD with various clinicopathological factors including steroid receptor, HER-2/neu receptor coexpression. The serum from seventy nine patients with invasive breast cancer and twenty individuals without malignancy was analyzed using the enzyme-linked immune adsorbent assay method. The cut-off value was estimated by the ROC curve analysis (15.86 μg/L). HER-2/neu ECD values in the serum of patients with breast cancer were significantly higher than in control subjects. Circulating HER-2/neu ECD was significantly associated with the histological grade of tumors and the status of axillary lymph nodes. Negative correlation was observed between HER-2/neu ECD in the serum and estrogen receptor positivity. When we analyzed HER-2/neu ECD in relation with coexpression of steroid receptor and HER-2/neu receptor in tissue, statistically higher values were found in the subgroup of patients with steroid receptor negative, HER-2/neu negative tumors than in the other subgroups. HER-2/neu ECD was not an independent factor in the univariate and multivariate analysis. However, elevated HER-2/neu ECD levels were found in patients with breast cancer possessing more aggressive phenotype.

CDK4/6 inhibition provides a potent adjunct to Her2-targeted therapies in preclinical breast cancer models

In spite of the efficacy of Her2-targeted therapies, recurrence and progression remain a challenge for treatment of Her2 positive breast cancer. CDK4/6 controls pathway downstream of Her2, Inhibition of these kinases could represent an important therapeutic approach to augment the effectiveness of standard therapies. In models of acquired resistance to Her2-targeted therapies, Cyclin D1 was inappropriately activated and CDK4/6 inhibition was effective at blocking proliferation by targeting this common pathway associated with resistance. These data were recapitulated in Her2 positive xenografts. Furthermore, in a series of 35 primary breast tumor explants, treatment with PD-0332991 resulted in a greater than 4-fold suppression of the Ki67. The effects of CDK4/6 inhibition were dependent on an intact RB-pathway, and consonantly, loss of RB and high-levels of p16 were associated with resistance to CDK4/6 inhibition. Combination studies illustrated that CDK4/6 inhibition is cooperative with multiple Her2-targeted agents and provides a complementary mechanism of action to T-DM1 to efficiently suppresses the proliferation of residual Her2-positive tumor cell populations that survive T-DM1. Together, these data indicate CDK4/6 is a viable therapeutic target that functions downstream of Her2, and tissue based markers are available to direct rational utilization of CDK4/6 inhibitors in combination with Her2-targeted agents.

The Mysterious Ways of ErbB2/HER2 Trafficking

The EGFR- or ErbB-family of receptor tyrosine kinases consists of EGFR/ErbB1, ErbB2/HER2, ErbB3/HER3 and ErbB4/HER4. Receptor activation and downstream signaling are generally initiated upon ligand-induced receptor homo- or heterodimerization at the plasma membrane, and endocytosis and intracellular membrane transport are crucial for regulation of the signaling outcome. Among the receptors, ErbB2 is special in several ways. Unlike the others, ErbB2 has no known ligand, but is still the favored dimerization partner. Furthermore, while the other receptors are down-regulated either constitutively or upon ligand-binding, ErbB2 is resistant to down-regulation, and also inhibits down-regulation of its partner upon heterodimerization. The reason(s) why ErbB2 is resistant to down-regulation are the subject of debate. Contrary to other ErbB-proteins, mature ErbB2 needs Hsp90 as chaperone. Several data suggest that Hsp90 is an important regulator of factors like ErbB2 stability, dimerization and/or signaling. Hsp90 inhibitors induce degradation of ErbB2, but whether Hsp90 directly makes ErbB2 endocytosis resistant is unclear. Exposure to anti-ErbB2 antibodies can also induce down-regulation of ErbB2. Down-regulation induced by Hsp90 inhibitors or antibodies does at least partly involve internalization and endosomal sorting to lysosomes for degradation, but also retrograde trafficking to the nucleus has been reported. In this review, we will discuss different molecular mechanisms suggested to be important for making ErbB2 resistant to down-regulation, and review how membrane trafficking is involved when down-regulation and/or relocalization of ErbB2 is induced.

Signaling pathways in breast cancer: therapeutic targeting of the microenvironment

Breast cancer is the most common cancer in women worldwide. Understanding the biology of this malignant disease is a prerequisite for selecting an appropriate treatment. Cell cycle alterations are seen in many cancers, including breast cancer. Newly popular targeted agents in breast cancer include cyclin dependent kinase inhibitors (CDKIs) which are agents inhibiting the function of cyclin dependent kinases (CDKs) and agents targeting proto-oncogenic signaling pathways like Notch, Wnt, and SHH (Sonic hedgehog). CDKIs are categorized as selective and non-selective inhibitors of CDK. CDKIs have been tried as monotherapy and combination therapy. The CDKI Palbocyclib is now a promising therapeutic in breast cancer. This drug recently entered phase III trial for estrogen receptor (ER) positive breast cancer after showing encouraging results in progression free survival in a phase II trials. The tumor microenvironment is now recognized as a significant factor in cancer treatment response. The tumor microenvironment is increasingly considered as a target for combination therapy of breast cancer. Recent findings in the signaling pathways in breast cancer are herein summarized and discussed. Furthermore, the therapeutic targeting of the microenvironment in breast cancer is also considered.

Future directions for monitoring treatment responses in breast cancer

In the prior review, we outlined the current standard of care for monitoring treatment responses in breast cancer and discussed the many challenges associated with these strategies. We described the challenges faced in common clinical settings such as the adjuvant setting, neoadjuvant setting, and the metastatic setting. In this review, we will expand upon future directions meant to overcome several of these current challenges. We will also explore several new and promising methods under investigation to enhance how we monitor treatment responses in breast cancer. Furthermore, we will highlight several new technologies and techniques for monitoring breast cancer treatment in the adjuvant, neoadjuvant and metastatic setting.

Life cycle management of critical ligand-binding reagents

Bioanalytical laboratories develop and validate ligand-binding assays (LBA) used to quantify the concentration of analytes of interest in various buffers and relevant biological matrices. The building blocks of LBA are reagents that recognize molecular and structural motifs on ligands, which are combined in various LBA formats to minimize biological matrix interferences and specifically detect and quantify the analyte of interest. The use of these LBA-requiring critical reagents, can span decades as programs mature to commercialization. Since critical reagents are generated mostly from biological systems, attention to their life cycle management, quality, characterization and sustainability are vital to the success of bioanalytical laboratories. Integrating de novo reagent generation, reagent biophysical characterization, LBA development, validation, and use, with reagent resupply processes leverages interdisciplinary activities and ensures smooth operations of a bioanalytical laboratory.

Evaluation of Serum Levels of HER2, MMP-9, Nitric Oxide, and Total Antioxidant Capacity in Egyptian Breast Cancer Patients: Correlation with Clinico-Pathological Parameters

Breast cancer is by far the most common cancer in women worldwide and the main cause of cancer-related mortality. Breast cancer accounts for 38% of all malignancies among Egyptian women. The aim of our study was to evaluate the serum levels of human epidermal growth factor receptor-2 (HER2), matrix metalloproteinase-9 (MMP-9), nitric oxide (NO), and total antioxidant capacity (TAC) in breast cancer patients and to correlate these markers with clinico-pathological parameters. Serum HER2, MMP-9, and carcinoma antigen 15-3 (CA 15-3) were assessed in 80 breast cancer patients and ten healthy subjects as a control group by the enzyme-linked immunosorbent assay (ELISA) technique while NO and TAC were assessed by a colorimetric method. Serum HER2 was ≥15 ng/mL in nine patients (11.3%). High HER2 ECD levels were significantly associated with tissue HER2 (P<0.0001), metastasis (P= 0.0024), and negativity of both estrogen (P=0.0075) and progesterone (P=0.0239) receptors. Serum MMP-9 (P=0.0013), NO (P<0.0001), and CA 15-3 (P<0.0001) were significantly increased while serum TAC was significantly (P=0.01) decreased in breast cancer patients as compared to the control group. Serum MMP-9 was increased significantly (P=0.028) in metastatic patients as compared to non-metastatic patients. We found a positive correlation between serum HER2 and CA 15-3 (r=36, p=0.005). In conclusion, serum HER2 reflects the tissue HER2 status of breast cancer, so the determination of serum HER2 is helpful in assessing HER2 status, but in addition, a high level may reflect metastatic disease. Also, serum MMP-9 can be useful for denoting the development of metastasis in breast cancer patients. Follow-up is needed to evaluate the value of serum HER2 and MMP-9 as prognostic markers.

Immunohistochemical analysis of the monoclonal antibody 4B5 in breast tissue expressing human epidermal growth factor receptor 4 (HER4)

AIMS

A recent study examining the specificity of human epidermal growth factor receptor (HER) 2 pharmacodiagnostic antibodies demonstrated that CB11 and 4B5 stain both HER2-transfected and HER4-transfected cell lines. However, there has been no evidence showing that 4B5 has affinity for HER4 in clinically obtained tissues, and, if so, whether this has any impact on the assessment of HER2. We therefore sought to determine the expression of membrane-bound HER4 in clinical breast carcinomas, and evaluate its impact on the clinical utility of 4B5 in determining HER2 status.

METHODS AND RESULTS

Breast carcinomas were assessed by immunohistochemistry (IHC) for membrane-bound HER4 using anti-HER4 clone E200. HER2 expression in these cases was then assessed using anti-HER2 clone 4B5, and a reference clone, SP3. In all 117 membrane HER4-positive cases (out of 241), 4B5 scored equal to or less than the reference anti-HER2 clone SP3. Eighteen cases were positive for membrane-bound HER4 by E200 and negative by 4B5, including a membrane HER4 level 3+ case.

CONCLUSIONS

No cross-reactivity of 4B5 with membrane-bound HER4 was identified in the clinical IHC analysis of formalin-fixed paraffin-embedded breast carcinoma cases as evidenced by the HER4 antibody clone E200.

Circulating HER2 Extracellular Domain: A Specific and Quantitative Biomarker of Prognostic Value in all Breast Cancer Patients?

The HER2 oncoprotein has emerged as an essential biomarker in the treatment of breast cancer patients. Once the primary breast cancer is removed, there is an increasing need to detect breast cancer recurrence as early as possible with the hope that earlier intervention with new anti-HER2 therapies will improve quality of life and increase overall survival. Numerous publications have shown that increasing blood levels of circulating HER2 is an early indicator of progression, particularly in HER2-positive patients and that the rise and fall parallels the clinical course of disease and independent of therapy. Many studies show that the HER2 status of the primary tumor may not fully and accurately reflect the HER2 status of recurrent cancer. Thus, elevated serum HER2 levels may be an early signal of the emergence of a HER2-positive metastatic tumor and therefore alert the physician to re-assess HER2 status using a tissue test.

Bringing cancer serological diagnosis to a new level: focusing on HER2, protein ectodomain shedding and neoepitope technology

Cancer is a heterogeneous disease and consequently an exact diagnosis is as important as the actual therapy. Therefore, identification of novel diagnostic biomarker targets is urgently needed. Physiological and pathological changes are reflected by post-translational modifications of proteins. Each post-translational modification (e.g., proteolytic cleavage) is the result of a specific local process and may produce disease-specific neoepitopes. Neoepitopes have been successfully used as biomarkers in many diseases, and may also serve as promising tools in the development of future diagnostic assays within oncology. By specifically targeting neoepitopes, more information regarding disease-type and -state may be obtained and future research into neoepitopes will provide important and novel means for the diagnosis, prognosis and treatment efficacy in cancer. In this paper, we focus on protein ectodomain shedding and the generation of neoepitopes as future noninvasive (serological) cancer biomarkers. We use the protein ectodomain shedding of the human epidermal growth factor receptor 2, which is associated with breast cancer, as an example. We assess the current status of measuring human epidermal growth factor receptor 2 and discuss how this potentially could be improved. Furthermore, we expand the discussion to include examples of other cancer associated proteins.

ErbB1-4-dependent EGF/neuregulin signals and their cross talk in the central nervous system: pathological implications in schizophrenia and Parkinson's disease

Ligands for ErbB1-4 receptor tyrosine kinases, such as epidermal growth factor (EGF) and neuregulins, regulate brain development and function. Thus, abnormalities in their signaling are implicated in the etiology or pathology of schizophrenia and Parkinson's disease. Among the ErbB receptors, ErbB1, and ErbB4 are expressed in dopamine and GABA neurons, while ErbB1, 2, and/or 3 are mainly present in oligodendrocytes, astrocytes, and their precursors. Thus, deficits in ErbB signaling might contribute to the neurological and psychiatric diseases stemming from these cell types. By incorporating the latest cancer molecular biology as well as our recent progress, we discuss signal cross talk between the ErbB1-4 subunits and their neurobiological functions in each cell type. The potential contribution of virus-derived cytokines (virokines) that mimic EGF and neuregulin-1 in brain diseases are also discussed.

SP3, a reliable alternative to HercepTest in determining HER-2/neu status in breast cancer patients

Accurate assessment of HER-2/neu gene status in breast cancer patients has important prognostic and therapeutic implications. Overexpression/gene amplification of HER-2 is associated with a more aggressive clinical course and eligibility for targeted therapy with trastuzumab. A variety of immunohistochemical (IHC) antibodies and in situ hybridisation (ISH) methods have been employed to assess HER-2 status. SP3 is a rabbit monoclonal antibody that has been shown to have a high level of agreement with other anti-HER-2 antibodies and ISH methods. We assessed HER-2 status by SP3 and HercepTest IHC stains and by fluorescence in situ hybridisation (FISH) on invasive breast carcinomas from paired needle core biopsy and excisional biopsy specimens from 100 patients. We compared the two antibodies with respect to concordance rates with FISH, concordance rates between samples of the same tumour, and sensitivity and specificity using FISH as the reference test. Concordance between SP3 and FISH in needle core biopsy and excisional biopsy specimens was 96% (95% CI 91.9% to 99.7%) (κ=0.89 (95% CI 0.73 to 1.00)) and 97% (95% CI 90.3% to 99.3%) (κ=0.84 (95% CI 0.66 to 1.00)), respectively. Sensitivity and specificity of SP3 for detecting HER-2 overexpression/gene amplification were 78.3% and 100%, respectively, in needle core biopsy and excisional biopsy specimens. Concordance between SP3 results assessed on the needle core biopsy and excisional biopsy was 89% (95% CI 81.2% to 94.4%) (κ=0.62 (95% CI 0.42 to 0.82)). Concordance between SP3 and HercepTest antibodies, after excluding 2+ cases, was 97.6% (95% CI 94.0% to 99.3%) (κ=0.88 (95% CI 0.77 to 1.00)). SP3 is a reliable alternative to HercepTest in evaluating HER-2 status in breast cancer patients. Like other anti-HER-2 antibodies, SP3 may serve as a diagnostic tool in breast pathology and has potential utility as an IHC biomarker in non-mammary malignancies.

Interference-Free HER2 ECD as a Serum Biomarker in Breast Cancer

Over-expression of the HER2/neu receptor occurs in 20 to 30 percent of breast tumors and is linked to poorer prognosis. The HER2/neu expression status determines whether or not patient will receive trastuzumab-based treatment. In clinical practice, over-expression of HER2/neu is routinely identified using Immunohistochemistry (IHC) or Fluorescence in Situ Hybridization (FISH), both of which are invasive approaches requiring tissue samples. Serum assays for the Extra Cellular Domain of HER2/neu receptor (HER2 ECD) have been reported but the use is very limited due to serum interference factors (e.g. human anti-animal immunoglobulin antibodies) that lead to false test results and inconsistency with tissue Her2 status. We have developed an ELISA based approach using an MBB buffer to eliminate false results and to obtain more accurate assessment of HER2 ECD levels. Using this refined assay we retroactively measured HER2/neu levels from breast cancer patients and controls. Abnormal HER2 ECD levels were detected in about 32% of invasive breast cancer patients but not in controls or patients with benign diseases. In addition, we also showed that patients with elevated serum HER2 levels appeared to have worse survival regardless of treatments. In a small group of 12 Ductal Carcinoma in situ (DCIS) patients who received HER2/neu peptide vaccination and surgery, only one patient showed constantly rising HER2 levels after treatment and this patient had recurrence of HER2 positive tumor within 5 years. Our studies indicate that once the serum interference issue is resolved, serum HER2 ECD can have potential clinical utility to supplement the tissue based tests.

Autocrine motility factor promotes HER2 cleavage and signaling in breast cancer cells

Trastuzumab (Herceptin) is an effective targeted therapy in HER2-overexpressing human breast carcinoma. However, many HER2-positive patients initially or eventually become resistant to this treatment, so elucidating mechanisms of trastuzumab resistance that emerge in breast carcinoma cells is clinically important. Here, we show that autocrine motility factor (AMF) binds to HER2 and induces cleavage to the ectodomain-deleted and constitutively active form p95HER2. Mechanistic investigations indicated that interaction of AMF with HER2 triggers HER2 phosphorylation and metalloprotease-mediated ectodomain shedding, activating phosphoinositide-3-kinase (PI3K) and mitogen-activated protein kinase signaling and ablating the ability of trastuzumab to inhibit breast carcinoma cell growth. Furthermore, we found that HER2 expression and AMF secretion were inversely related in breast carcinoma cells. On the basis of this evidence that AMF may contribute to HER2-mediated breast cancer progression, our findings suggest that AMF-HER2 interaction might be a novel target for therapeutic management of patients with breast cancer, whose disease is resistant to trastuzumab.

Spontaneous and pronase-induced HER2 truncation increases the trastuzumab binding capacity of breast cancer tissues and cell lines

A subgroup of HER2-overexpressing breast tumours co-expresses p95(HER2), a truncated HER2 receptor that retains a functional HER2 kinase domain but lacks the extracellular domain, thus impairing trastuzumab binding. We evaluated p95(HER2) expression in 99 frozen breast carcinoma samples by western blot analysis. The HER2-positive cell line BT474 treated with pervanadate or pronase was used as a positive control for p95(HER2) expression. Immunohistochemistry was performed on parallel formalin-fixed, paraffin-embedded sections of the same case series using antibodies directed against either the intra- or extra-cellular binding domain of HER2. In particular, biotinylated trastuzumab (BiotHER) was used to evaluate the binding capacity of the humanized antibody. To avoid a subjective evaluation of the score values and the percentage of immunostained cells, the slides were scanned and automatically analysed. The number of cases with HER2 overexpression (score 3+) and HER2 gene amplification was higher in the p185(HER2)-positive/p95(HER2)-positive samples than in the p185(HER2)-positive/p95(HER2)-negative group. Automated analysis confirmed a significantly higher percentage of 3+ scored cells in p95(HER2)-positive cases. Conversely, the percentage of 2+ scored cells was higher inp95(HER2)-negative cases. The status of the HER2 extracellular domain was then studied using flow cytometry on BT474 cells after pronase enzymatic digestion using trastuzumab and pertuzumab, while the presence of HER2-HER3 dimers was studied using a proximity-ligation assay. In vitro experiments showed that short-term pronase digestion of BT474 cells produced two HER2 fragments (of 95 and 150 kDa, detectable in tissue specimens as well), increased the binding affinity of trastuzumab, reduced the rate of HER2-HER3 dimers, and did not interfere with pertuzumab-binding capacity. In conclusion, the presence of p95(HER2 as detected by western blot analysis does not compromise the immunohistochemical detection of HER2. Our data suggest that a reduction of the receptor steric hindrance as induced by enzymatic shedding may facilitate the binding capacity of trastuzumab.

Predictive value of HER2 serum levels in patients treated with lapatinib or trastuzumab -- a translational project in the neoadjuvant GeparQuinto trial

BACKGROUND

We were able to demonstrate a predictive value of serum HER2 (sHER2) in patients receiving trastuzumab in the neoadjuvant GeparQuattro trial. However, the role of sHER2 in patients receiving neoadjuvant therapy (NT) with lapatinib is still unclear.

METHODS

The neoadjuvant GeparQuinto trial compared trastuzumab vs lapatinib in addition to chemotherapy in HER2-positive primary breast cancer patients. The sHER2 levels were measured by enzyme-linked immunosorbant assay in 210 patients, of whom 109 (52%) patients received trastuzumab and 101 (48%) lapatinib at three different time points.

RESULTS

Twenty-two percent of patients had elevated baseline sHER2 levels (>15 ng ml⁻¹). A decrease of sHER2 levels (>20%) in the trastuzumab and lapatinib-treated group during NT was seen in 44% and 24% of the patients, an increase of sHER2 levels (>20%) was seen in 6% and 41% of patients, respectively. Higher pre-chemotherapy sHER2 levels were associated with higher pathological complete remission (pCR) rates in the entire study cohort (OR 1.8, 95% CI 1.02-3.2, P=0.043). A decline of sHER2 levels (>20%) during NT was a predictor for pCR in the lapatinib-treated patient group (OR: 11.7, 95% CI 1.3-110, P=0.031).

CONCLUSION

Results of this study demonstrate that sHER2 levels change differently during NT depending on the anti-HER2 treatment strategy. Elevated baseline sHER2 levels (>15 ng ml⁻¹) and a decrease of sHER2 levels (>20%) early after therapy initiation are both relevant criteria to predict response to lapatinib-based treatment.

Targeting high affinity and epitope-distinct oligoclonal nanobodies to HER2 over-expressing tumor cells

Modern anti-HER2 antibody therapy tends to exploit a panel of different antibodies against different epitopes on the antigen. For this aim, nanobodies are very striking targeting agents and can be easily produced against any cell-specific membrane antigen. The oligoclonal nanobodies can be used to block more than one functional epitope on a target antigen and inhibit the generation of escape variants associated with cancer therapy. In this study, 12 nanobody clones selected from an immune camel library were examined for their ability to differ between tumor markers. These oligoclonal nanobodies targeted breast cancer cells better than each individual nanobody. In epitope mapping, several nanobodies overlapped in the epitope recognized by trastuzumab and some of the non-overlapping nanobodies could affect the binding of trastuzumab to HER2. This study demonstrates that the oligoclonal nanobodies are potential therapeutic tools that can be used instead of, or in combination with trastuzumab to assess tumor viability during treatment.