Subtype-Independent Activation of NF-κB Signaling in Breast Cancer

Nuclear factor kappa B (NF-κB) signaling plays a central role in inflammation, immunity, cell survival, and cancer progression. Its constitutive activation is frequently observed in breast cancer, contributing to tumor growth, treatment resistance, and metastasis. MicroRNAs (miRNAs) are key post-transcriptional regulators of gene expression and may modulate NF-κB signaling in a subtype-specific or -independent manner. The aim of the study was to identify miRNAs that may potentially regulate the activity of genes associated with NF-κB signaling across five molecular subtypes of breast cancer in Polish women. Tumor and matched normal tissue samples were collected from 405 patients with five breast cancer subtypes: luminal A (n = 130), HER2-negative luminal B (n = 100), HER2-positive luminal B (n = 96), non-luminal HER2-positive (n = 36), and triple-negative breast cancer (TNBC, n = 43). Expression profile of selected NF-κB-related genes were evaluated using mRNA microarrays and RT-qPCR. Protein levels were assessed by ELISA. Candidate regulatory miRNAs were identified via miRNA microarrays and validated using the miRDB database. A consistent upregulation of MAP3K7, TAB2, TNFAIP3, CSNK2A1, BCL2L1, XIAP, CXCL2, and PLAU was observed across all subtypes, suggesting activation of canonical NF-κB signaling. Downregulation of specific miRNAs, miR-1297 and miR-30a (targeting MAP3K7), miR-134 (TAB2), miR-125b (TNFAIP3), and miR-4329 (XIAP), may contribute to this deregulation. For CSNK2A1, BCL2L1, CXCL2, and PLAU, no regulatory miRNAs meeting our criteria were identified. Our study reveals a subtype-independent activation of the canonical NF-κB signaling pathway in breast cancer, underpinned by consistent upregulation of key components (at both the transcript and protein levels. Dysregulation of specific miRNAs likely contributes to this altered gene expression. These findings suggest the presence of a common NF-κB-driven oncogenic program across molecular subtypes, with potential implications for developing miRNA-based therapeutic strategies targeting inflammation, survival signaling, and treatment resistance in breast cancer.