One Step Nucleic Acid Amplification (OSNA) Lysate Samples Are Suitable to Establish a Transcriptional Metastatic Signature in Patients with Early Stage Hormone Receptors-Positive Breast Cancer

SIMPLE SUMMARY: The One Step Nucleic Acid Amplification (OSNA) is a recent technique for sentinel lymph nodes staging in breast cancer (BC). After OSNA assay, instead of being discarded, the residual OSNA lysate can also be used for gene expression studies, being the potentially ideal sample to search for new biomarkers. The aim of our study was to identify biomarkers related to tumor-microenvironment interplay in OSNA lysate of sentinel lymph nodes in women with early stage hormone receptors-positive BC. We identified 11 upregulated genes in metastatic lymph nodes. These genes codify proteins mainly involved in cancer aggressiveness and with impact in immune response. Thus, these findings support that OSNA lysate transcriptomic analysis may identify biomarkers potentially useful in the future for prognosis stratification and therapy selection. As OSNA assay is being implemented for sentinel lymph nodes staging in other cancers, this approach could also have a wider utility. ABSTRACT: The One Step Nucleic Acid Amplification (OSNA) is being adopted worldwide for sentinel lymph nodes (SLNs) staging in breast cancer (BC). As major disadvantage, OSNA precludes prognostic information based on structural evaluation of SLNs. Our aim is to identify biomarkers related to tumor-microenvironment interplay exploring gene expression data from the OSNA remaining lysate. This study included 32 patients with early stage hormone receptors-positive BC. Remaining OSNA lysates were prepared for targeted RNA-sequencing analysis. Identification of differentially expressed genes (DEGs) was performed by DESeq2 in R and data analysis in STATA. The results show that, in metastatic SLNs, several genes were upregulated: KRT7, VTCN1, CD44, GATA3, ALOX15B, RORC, NECTIN2, LRG1, CD276, FOXM1 and IGF1R. Hierarchical clustering analysis revealed three different clusters. The identified DEGs codify proteins mainly involved in cancer aggressiveness and with impact in immune response. The overexpression of the immune suppressive genes VTCN1 and CD276 may explain that no direct evidence of activation of immune response in metastatic SLNs was found. We show that OSNA results may be improved incorporating microenvironment-related biomarkers that may be useful in the future for prognosis stratification and immunotherapy selection. As OSNA assay is being implemented for SLNs staging in other cancers, this approach could also have a wider utility.