Quantitative detection of HER2 protein concentration in breast cancer tissue does not increase the number of patients eligible for adjuvant HER2-targeted therapy

Histo-ELISA technique for quantification and localization of tissue components

A novel Histo-ELISA technique is intended to facilitate quantification of target tissue proteins in a tissue section and involves the selection of target regions in the tissue section, application of streptavidin-conjugated HRP (horseradish peroxidase), coupled with peroxidase substrate—TMB (3,3′,5,5′-tetramethylbenzidine), and staining dye evaluation with ELISA reader. The target protein content (weight per volume unit) was translated from optical densities by a reference standard curve, obtained via parallel staining of the targeted protein-coated slides. To validate the technique, we carried out quantifications of IgG extravasation in ischemic and nonischemic brain sections in a mouse stroke model. With those obtained data and the reference of immunohistochemistry scores assessed on the adjacent sections, accuracy, sensitivity, and precision for the technique were evaluated. For all evaluated parameters, Histo-ELISA performance was either comparable to or better than the standard immunohistochemistry. A comparison with the data from the repeated measurements yielded a rather low coefficient of variation. The results confirmed that the technique is a fairly reliable quantitative test with rather high sensitivity, accuracy, precision, and reproducibility for detecting target protein content in tissue sections and that its tissue distribution and related subsequent morphological changes can be observed at the same time.

An Electrochemical Sandwich Immunosensor for the Detection of HER2 using Antibody-Conjugated PbS Quantum Dot as a label

A facile electrochemical sandwich immunosensor for the detection of a breast cancer biomarker, the human epidermal growth factor receptor 2 (HER2), was designed, using lead sulfide quantum dots-conjugated secondary HER2 antibody (Ab2-PbS QDs) as a label. Using Ab2-PbS QDs in the development of electrochemical immunoassays leads to many advantages such as straightforward synthesis and well-defined stripping signal of Pb(II) through acid dissolution, which in turn yields better sensing performance for the sandwiched immunosensor. In the bioconjugation of PbS QDs, the available amine and hydroxyl groups from secondary anti-HER2 and capped PbS QDs were bound covalently together via carbonyldiimidazole (CDI) acting as a linker. In order to quantify the biomarker, SWV signal was obtained, where the Pb²⁺ ions after acid dissolution in HCl was detected. The plated mercury film SPCE was also detected in situ. Under optimal conditions, HER2 was detected in a linear range from 1-100 ng/mL with a limit of detection of 0.28 ng/mL. The measures of satisfactory recoveries were 91.3% to 104.3% for the spiked samples, displaying high selectivity. Therefore, this method can be applied to determine HER2 in human serum.

A novel quantitative immunohistochemistry method for precise protein measurements directly in formalin-fixed, paraffin-embedded specimens: analytical performance measuring HER2

In clinical routine pathology today, detection of protein in intact formalin-fixed, paraffin-embedded tissue is limited to immunohistochemistry, which is semi-quantitative. This study presents a new and reliable quantitative immunohistochemistry method, qIHC, based on a novel amplification system that enables quantification of protein directly in formalin-fixed, paraffin-embedded tissue by counting of dots. The qIHC technology can be combined with standard immunohistochemistry, and assessed using standard bright-field microscopy or image analysis. The objective was to study analytical performance of the qIHC method. qIHC was tested under requirements for an analytical quantitative test, and compared with ELISA and flow cytometry for quantitative protein measurements. Human epidermal growth factor receptor 2 (HER2) protein expression was measured in five different cell lines with HER2 expression from undetectable with immunohistochemistry to strong positive staining (IHC 3+). Repeatability, reproducibility, robustness, linearity, dynamic range, sensitivity, and quantification limits were evaluated. Reproducibility and robustness were assessed in a setup to resemble daily work in a laboratory using a commercial immunohistochemistry platform. In addition, qIHC was correlated to standard HER2 immunohistochemistry in 44 breast cancer specimens. For all evaluated parameters, qIHC performance was either comparable or better than the reference methods. Furthermore, qIHC has a lower limit of detection than both immunohistochemistry and the ELISA reference method, and demonstrated ability to measure HER2 accurately and precise within a large dynamic range. In conclusion, the results show that qIHC provides a sensitive, quantitative, accurate, and robust assay for measurement of protein expression in formalin-fixed, paraffin-embedded cell lines, and tissue.

Long-term Follow-up Data from Pivotal Studies of Adjuvant Trastuzumab in Early Breast Cancer

The addition of adjuvant trastuzumab therapy for 1 year to standard chemotherapy significantly improved disease-free survival and overall survival versus chemotherapy alone in a number of pivotal early breast cancer studies. Here we review long-term follow-up data on the efficacy, cardiac safety, and general safety of trastuzumab in these pivotal studies. We also evaluate ongoing phase II/III adjuvant trials with newer HER2-targeted agents and the efficacy and safety of the recently developed subcutaneous (SC) formulation of trastuzumab in early breast cancer. Long-term follow-up data confirm the significant survival benefit afforded by the addition of trastuzumab to chemotherapy in patients with HER2-positive disease, with an acceptable safety profile. Long-term cardiac safety data suggest that the incidence of cardiac adverse events is maintained at a relatively low level with continued follow-up. At this present time, 1 year of trastuzumab treatment remains the standard of care in HER2-positive early breast cancer. Future adjuvant trastuzumab treatment strategies should focus on reducing cardiotoxicity, particularly in elderly patients, by identifying potential predictive biomarkers of cardiac dysfunction. Clinicians must also decide whether to omit trastuzumab in women who would achieve little benefit from treatment to avoid cardiotoxicity.

Serum human epidermal growth factor receptor 2 levels as a real-time marker for tumor burden in breast cancer patients

BACKGROUND AND OBJECTIVES

Human epidermal growth factor receptor 2 (HER2) status, an important factor in the treatment of breast cancer patients, is usually determined using primary tumor tissue samples; however, the HER2 status of metastatic lesions may differ from that of the primary tumor, but biopsies cannot be performed in all cases. Here, we investigated whether serum HER2 levels can serve as an alternative to assessments of HER2 expression in cancer tissues.

METHODS

Between April 2008 and July 2009, serum HER2 levels were evaluated in 295 patients with newly diagnosed breast cancer, 1,068 patients under follow-up care without recurrence after curative surgery, and 82 patients with disease recurrence.

RESULTS

Among 303 patients with histologically confirmed HER2-positive tumors, the rates of serum HER2 elevation were 9.2% in preoperative patients, 0.9% in patients under follow-up care without recurrence, and 44.0% in patients with recurrent disease; for patients with HER2-negative primary tumors, the corresponding values were 0.8%, 2.6%, and 15.8%, respectively.

CONCLUSION

Our results suggest that serum HER2 could be a useful real-time marker for tumor burden and recurrence in patients with HER2-positive disease.