Evaluation of ERBB2 mRNA Expression in HER2-Equivocal (2+) Immunohistochemistry Cases

In ER-Positive, HER2-Negative Breast Cancers, HER2 mRNA Levels Correlate Better with Clinicopathologic Features and Oncotype DX Recurrence Score than HER2 Immunohistochemistry

With the approval of trastuzumab deruxtecan for treating advanced human epidermal growth factor receptor-2 (HER2) low breast cancer (BC), it has become increasingly important to develop more accurate and reliable methods to identify HER2-low BC. In addition, HER2 immunohistochemistry (IHC) has limitations for quantification of HER2. We explored the relationship between HER2 IHC and mRNA levels and evaluated whether HER2 IHC scores and mRNA levels are associated with clinicopathologic features and Oncotype DX Recurrence Score (RS) in estrogen receptor (ER)-positive, HER2-negative BCs. A total of 750 BCs sent for Oncotype DX (ODX) testing were included in this study, and 559 with HER2 mRNA levels were available. There were no statistically significant differences between HER2 0 and HER2-low BC in clinicopathologic variables or ODX RS using HER2 IHC. There was a significant difference in median HER2 mRNA values between HER2 0 and HER2-low (8.7 vs 9.3, P < .001); however, the HER2 mRNA distribution had substantial overlap between these 2 groups with a suboptimal area under the receiver operating characteristic curve (area under the receiver operating characteristic curve = 0.68). A HER2 mRNA value of 9.2 was generated as the optimal cutoff for distinguishing HER2 0 and HER2-low BC. Comparing ER+ BCs with HER2 mRNA high (>9.2) and low (≤9.2) revealed a statistically significant difference in most clinicopathologic variables and ODX RS. From this large cohort of ER-positive, HER2-negative BC, our results demonstrated that HER2 mRNA levels correlated better with clinicopathologic features and recurrence risk as assessed by ODX RS than HER2 IHC scores. Our findings suggest that HER2 mRNA-detecting methods could potentially serve as a quantitative and reliable method for identifying a biologically meaningful group of HER2-low BC. Further study is needed to determine whether HER2 mRNA levels could be more reliable than IHC for identifying which patients will be most likely to benefit from trastuzumab deruxtecan.

Magnetically induced self-assembly electrochemical biosensor with ultra-low detection limit and extended measuring range for sensitive detection of HER2 protein

An innovative electrochemical biosensor was fabricated for sensitive detection of human epidermal growth factor receptor 2 (HER2) protein, which was considered as an essential tumor marker for diagnosis and treatment evaluation of breast cancer. The sensor was constructed using Apt and PNA as recognition probes incorporated with magnetic Fe3O4/α-Fe2O3@Au nanocomposites. The sensing strategy was designed to lower the detection limit of HER2, and avoid the large steric interference caused by macromolecular HER2 on the electrode surface. Rigid structure dsDNA (Apt/ssDNA) was designed to improve the sensitivity of the sensor. Apt captured the macromolecular HER2 protein, and ssDNA chains were simultaneously released, causing a sensitive change in the electrochemical signal. PNA captured the released ssDNA chains, which converted the electrochemical signal changes caused by HER2 to those caused by the number of short strand ssDNA, so the detection range was extended. Under optimized conditions, this sensing strategy realized an ultra-low detection LOD of HER2 (4.1 fg·mL-1), and the detection range was 10 fg·mL-1-5 × 106 fg·mL-1. The experimental results confirmed that the electrochemical biosensor had excellent selectivity, reproducibility, and storage stability. Analysis of spiked serum samples exhibited a recovery rate of 95.9-115.7 %, which indicated great promise for HER2 detection in serum samples.