Serum HER2 levels determined by two methods in patients with metastatic breast cancer

Dual amplification for PEC ultrasensitive aptasensing of biomarker HER-2 based on Z-scheme UiO-66/CdIn2S4 heterojunction and flower-like PtPdCu nanozyme

As an important prognostic indicator in breast cancer, human epithelial growth factor receptor-2 (HER-2) is of importance for assessing prognosis of breast cancer patients, whose accurate and facile analysis are imperative in clinical diagnosis and treatment. Herein, photoactive Z-scheme UiO-66/CdIn2S4 heterojunction was constructed by a hydrothermal method, whose optical property and photoactivity were critically investigated by a range of techniques, combined by elucidating the interfacial charge transfer mechanism. Meanwhile, PtPdCu nanoflowers (NFs) were fabricated by a simple aqueous wet-chemical method, whose peroxidase (POD)-mimicking catalytic activity was scrutinized by representative tetramethylbenzidine (TMB) oxidation in H2O2 system. Taken together, the UiO-66/CdIn2S4 based photoelectrochemical (PEC) aptasensor was established for quantitative analysis of HER-2, where the detection signals were further magnified through catalytic precipitation reaction towards 4-chloro-1-naphthol (4-CN) oxidation (assisted by the PtPdCu NFs nanozyme). The PEC aptasensor presented a broader linear range within 0.1 pg mL-1-0.1 μg mL-1 and a lower limit of detection of 0.07 pg mL-1. This work developed a new PEC aptasensor for ultrasensitive determination of HER-2, holding substantial promise for clinical diagnostics.

Advances in HER2 testing

HER2-positive breast cancer is a particularly aggressive type of breast cancer. Indication of HER2 positivity is essential for its treatment. In addition to a few FDA-approved methods such as immunohistochemical (IHC) detection of HER2 protein expression and in situ hybridization (ISH) assessment of HER2 gene amplification, several novel methods have been developed for HER2 testing in recent years. This chapter provides an overview of HER2 testing with emphasis on those new methods.

Advantages and disadvantages of technologies for HER2 testing in breast cancer specimens

OBJECTIVES

Human epidermal growth factor receptor 2 (HER2) plays a central role as a prognostic and predictive marker in breast cancer specimens. Reliable HER2 evaluation is central to determine the eligibility of patients with breast cancer to targeted anti-HER2 therapies such as trastuzumab and lapatinib. Presently, several methods exist for the determination of HER2 status at different levels (protein, RNA, and DNA level).

METHODS

In this review, we discuss the main advantages and disadvantages of the techniques developed so far for the evaluation of HER2 status in breast cancer specimens.

RESULTS

Each technique has its own advantages and disadvantages. It is therefore not surprising that no consensus has been reached so far on which technique is the best for the determination of HER2 status.

CONCLUSIONS

Currently, emphasis must be put on standardization of procedures, internal and external quality control assessment, and competency evaluation of already existing methods to ensure accurate, reliable, and clinically meaningful test results. Development of new robust and accurate diagnostic assays should also be encouraged. In addition, large clinical trials are warranted to identify the technique that most reliably predicts a positive response to anti-HER2 drugs.

Serum HER2 extracellular domain as a potential alternative for tissue HER2 status in metastatic gastric cancer patients

AIM

We investigated whether serum concentrations of the HER2 extracellular domain (ECD) can be used as an alternative to test tissue HER2 status in metastatic gastric cancer.

MATERIALS & METHODS

A total of 133 cases of metastatic gastric cancer were included in present study. Serum HER2 ECD was measured by chemiluminescence immunoassay (CLIA). Receiver operating characteristic curve analysis was used to determine optimal serum HER2 ECD concentrations for differentiation between positive and negative HER2 status.

RESULTS

The median level of serum HER2 ECD was 9.6 ng/ml in metastatic gastric cancer patients. There was a significant relationship between serum and tissue levels of HER2 protein (p < 0.001). Area under the curve for serum HER2 ECD was 0.771 (95% CI: 0.682-0.860).

CONCLUSION

Levels of serum HER2 ECD are highly correlated with tissue HER2 status in metastatic gastric cancer. Serum HER2 ECD assay can be considered as a potential alternative for tissue HER2 status.

Clinical significance of glycoprotein nonmetastatic B and its association with HER2 in breast cancer

Glycoprotein nonmetastatic B (GPNMB) is a potential oncogene that is particularly expressed in melanoma and breast cancer (BC). To clarify its clinical significance in BC, we measured serum GPNMB in vivo and investigated its cross talk with human epidermal growth factor 2 (HER2). GPNMB was expressed in four of six breast cell lines (SK-BR-3, BT-474, MDA-MD-231, and MDA-MD-157), two of six colorectal cell lines, and two of four gastric cancer (GC) cell lines. We established a GPNMB quantification system using enzyme-linked immunosorbent assay (ELISA) for these cell lines. We measured serum GPNMB in vivo in 162 consecutive BC patients and in 88 controls (50 colorectal cancer [CC] and 38 GC patients). The GPNMB concentration in BC, CC and GC was 8.163, 5.751 and 6.55 ng/mL, respectively. The GPNMB level was significantly higher in BC patients than in CC patients (P = 0.021). The HER2-rich subtype of BC patients had significantly higher GPNMB levels than other subtypes (vs. Luminal; P = 0.038; vs. DCIS; P = 0.0195). These high GPNMB levels decreased after treatment (surgery/chemotherapy). Next, we examined the relationship between GPNMB and HER2 in vitro using SK-BR3 and BT-474 (HER2-positive/GPNMB-positive) cells. GPNMB depletion by small interfering RNA (siRNA) increased both HER2 expression and phosphorylation. Trastuzumab (Tra) in combination with docetaxel promoted cell growth inhibition, and treatment with Tra or an Extracellular signal-related kinase (ERK) inhibitor enhanced GPNMB expression. These results indicate that GPNMB might be a surrogate marker for BC and may cross talk with the HER2 signal pathway. GPNMB may therefore emerge as an important player in anti-HER2 therapy.

Challenges in the clinical utility of the serum test for HER2 ECD

Approximately 15-30% of breast cancers over-express the HER2/neu receptor. Historically, over-expression of HER2/neu has been identified using IHC or FISH, both of which are invasive approaches requiring tissue samples. Recent evidence has shown that some tumors identified as "negative" using these methods can respond to HER2/neu targeted therapy. Shedding of the extracellular domain (ECD) of the receptor into the circulation has led to the development of a serum test of HER2 ECD as an additional approach to probe HER2/neu overexpression. The serum test will be able to monitor the dynamic changes of HER2 status over the course of disease progression. Some studies further suggest that the serum HER2 ECD level and its change may serve as a biomarker to reflect patients' response to therapy. Yet more than 10years after the first serum HER2 ECD test was approved by the FDA, serum HER2 testing has yet to be widely used in clinical practice. In this article we will review the progress of the serum HER2 ECD test and discuss some obstacles impeding its incorporation into broad clinical practice. We will also discuss recent improvements in the sensitivity and specificity of the assay that offer some hope for the future of serum HER2 test.