Gene expression comparison between primary aggressive luminal breast cancer and paired axillary and sentinel lymph node metastasis.

Abstract

e13060 Background: More aggressive and therapy-resistant hormone receptor (HR)-positive breast cancer (hereafter luminal breast cancer, LBC) remains a great challenge. Few studies examine the genomics of axillary lymph node (ALN) metastasis in LBC. The aim of this study was to characterize and compare the mRNA expression patterns of primary breast cancers and paired ALN metastases. Methods: Aggressive pT1-2N2-3M0 LBC patients aged over 18 years who were treated at Shandong Provincial Hospital Affiliated to Shandong First Medical University and had available matched primary and metastatic tumor samples for gene expression analyses were retrospectively recruited. Bulk mRNA expression levels were determined by RNA sequencing (Illumina NovaSeq 6000 system) and calculated using featureCounts. Differential gene expression analysis was performed using DESeq2. All analyses were carried out with differentially expressed genes (DEGs) with an FDR <0.05. Changes of intrinsic subtypes from primary to metastatic disease were assessed. Results: Ten LBC patients with paired tumor samples were included. Compared with the primary tumor, ALN metastatic tumor had 1509 statistically significant DEGs, including 743 upregulated genes and 766 downregulated genes. Notably, there was an upregulation of genes related to immune response-activating signal transduction, T cell receptor signaling pathway, B cell receptor signaling pathway, and cytokine-cytokine receptor interaction in the ALN metastasis. The downregulation of genes were mainly enriched in the PI3K-Akt signaling pathway, ECM-receptor interaction, Wnt signaling pathway, and TGF-beta signaling pathway. Intrinsic subtype distribution in primary tumors was different from those in ALN metastatic tumors, such as Luminal A (30% vs. 50%), Luminal B (10% vs. 20%), HER2-enriched (20% vs. 10%), Basal-like (10% vs. 10%), and Normal-like (30% vs. 10%). These results suggest that LBC is a highly heterogeneous disease. Conclusions: In aggressive pT1-2N2-3M0 LBC, ALN metastases have a distinct gene expression profile and show upregulation of immune-related genes ( CR2, BLK, PAX5, CD19, FCRL1, TNFRSF13B). Genes associated with signaling pathways are involved in the development of breast cancer ( FST, TNN, LAMC3, SFRP2, FGF18), and are downregulated when compared to autologous primary cancer. These pathways are potential targeted pathways in the treatment of breast cancer. LBC cells metastatic to lymph nodes undergo a change to metastasize and survive in the new microenvironment, which may provide insights into the metastatic process. Besides, a switch towards more aggressive intrinsic subtype from primary to advanced disease is also observed.