Translational Implications of Dysregulated Pathways and microRNA Regulation in Quadruple-Negative Breast Cancer

Triple-negative breast cancers (HER2-, ER-, PR-) continue to present a unique treatment challenge and carry unfavorable prognoses. The elucidation of novel therapeutic targets has necessitated the re-evaluation of stratification approaches to best predict prognosis, treatment response and theranostic and prognostic markers. Androgen receptor expression and function have important implications on proliferation, tumor progression, immunity and molecular signaling in breast cancer. Accordingly, there has been increasing support for classification of androgen receptor-negative triple-negative breast cancer or quadruple-negative breast cancer (QNBC). QNBC has unique molecular, signaling and expression regulation profiles, particularly those affected by microRNA regulatory networks. microRNAs are now known to regulate AR-related targets and pathways that are dysregulated in QNBC, including immune checkpoint inhibitors (ICIs), SKP2, EN1, ACSL4 and EGFR. In this review, we explore and define the QNBC tumor subtype, its molecular and clinical distinctions from other subtypes, miRNA dysregulation and function in QNBC, and knowledge gaps in the field. Potential insights into clinical and translational implications of these dysregulated networks in QNBC are discussed.

Automated summary

Triple-negative breast cancers present unique treatment challenges and carry unfavorable prognoses. The classification of androgen receptor-negative triple-negative breast cancer, or quadruple-negative breast cancer (QNBC), is gaining increasing support. QNBC has distinct molecular profiles affected by microRNA regulatory networks, including dysregulation in immune checkpoint inhibitors, SKP2, EN1, ACSL4, and EGFR. Insights into the clinical implications of these dysregulated networks in QNBC are discussed.