In Situ Quantitative Measurement of HER2mRNA Predicts Benefit from Trastuzumab-Containing Chemotherapy in a Cohort of Metastatic Breast Cancer Patients

Abstract

BackgroundWe sought to determine the predictive value of in situ mRNA measurement compared to traditional methods on a cohort of trastuzumab-treated metastatic breast cancer patients.MethodsA tissue microarray composed of 149, classified as HER2-positive, metastatic breast cancers treated with various trastuzumab-containing chemotherapy regimens was constructed. HER2 intracellular domain(ICD), HER2 extracellular domain(ECD) and HER2 mRNA were assessed using AQUA. For HER2 protein evaluation, CB11 was used to measure ICD and SP3 to measure ECD of the HER2 receptor. In addition, HER2 mRNA status was assessed using RNAscope assay ERRB2 probe. Kaplan – Meier estimates were used for depicting time-to-event endpoints. Multivariate Cox regression models with backward elimination were used to assess the performance of markers as predictors of TTP and OS, after adjusting for important covariates.ResultsHER2 mRNA was correlated with ICD HER2, as measured by CB11 HER2, with ECD HER2 as measured by SP3 (Pearson’s Correlation Coefficient, r = 0.66 and 0.51 respectively) and with FISH HER2 (Spearman’s Correlation Coefficient, r = 0.75). All markers, HER2 mRNA, ICD HER2 and ECD HER2, along with FISH HER2, were found prognostic for OS (Log-rank p = 0.007, 0.005, 0.009 and 0.043 respectively), and except for FISH HER2, they were also prognostic for TTP Log-rank p = 0.036, 0.068 and 0.066 respectively) in this trastuzumab- treated cohort. Multivariate analysis showed that in the presence of pre-specified set of prognostic factors, among all biomarkers only ECD HER2, as measured by SP3, is strong prognostic factor for both TTP (HR = 0.54, 95% CI: 0.31–0.93, p = 0.027) and OS (HR = 0.39, 95%CI: 0.22–0.70, p = 0.002).ConclusionsThe expression of HER2 ICD and ECD as well as HER2 mRNA levels was significantly associated with TTP and OS in this trastuzumab-treated metastatic cohort. In situ assessment of HER2 mRNA has the potential to identify breast cancer patients who derive benefit from Trastuzumab treatment.

Simultaneous Multiplexed Imaging of mRNA and Proteins with Subcellular Resolution in Breast Cancer Tissue Samples by Mass Cytometry

“…Furthermore, we characterized the mRNA expression of HER2 , CK19 , and CXCL10 (also known as IP-10 ) in combination with 16 antibodies in 70 samples from breast cancer patients. The HER2 gene is frequently genetically amplified in breast cancer patients, and HER2 mRNA expression levels have been shown to be highly correlated to genetic status and protein levels ( Vassilakopoulou et al., 2014 , Wang et al., 2013 ), making HER2 an ideal gene for validation of the system. CK19 is a type-1 cytokeratin often expressed in breast cancer that can be used as a marker to detect disseminated tumor cells in lymph nodes by mRNA or protein detection methods, but the mRNA-to-protein correlation in tissues is unknown ( Visser et al., 2008 ).…”

HER2 amplification level is not a prognostic factor for HER2-positive breast cancer with trastuzumab-based adjuvant treatment: a systematic review and meta-analysis

“…There was a discrepancy at the protein level in the two studies, which used different scoring systems and found that the Hercept test scoring system may be not accurate enough to identify the correlation [ 40 , 41 ]. In metastatic setting, seven out of eight studies at DNA and mRNA level showed there was a positive correlation between HER2 amplification or mRNA expression level and response to trastuzumab or survival [ 43 – 49 ]. The only study that did not reach the limit of statistical significance was an explorative study with a small sample size of 33 [ 50 ].…”

In situ analysis of FGFR2 mRNA and comparison with FGFR2 gene copy number by dual-color in situ hybridization in a large cohort of gastric cancer patients

“…Based on mRNA analysis, an additional 7% of breast cancer patients may be eligible for Herceptin therapy [ 51 ]. HER2 detection by RNAscope correlates well with immunohistochemistry and DNA-FISH [ 52 ]. HER2 expression could also be detected reliably by RNAscope in gastric cancer [ 53 ].…”