SIRT1 Promotes Breast Cancer Stem Cell-Associated Properties and Represents a Potential Therapeutic Target.

Breast cancer stem cells (BCSCs) drive tumor progression, metastasis, and therapeutic resistance. Sirtuin 1 (SIRT1) has been implicated in stem cell regulation, but its context-dependent role in BCSC maintenance and the underlying molecular mechanisms remain poorly defined. SIRT1 expression was evaluated in human breast cancer specimens. Pharmacologic and genetic SIRT1 inhibition was assessed in breast cancer cell lines and orthotopic xenograft models to determine effects on stemness, epithelial-mesenchymal transition (EMT), metastasis, and chemoresistance, with emphasis on Wnt/β catenin signaling. SIRT1 was overexpressed in breast cancer and correlated with higher tumor grades. SIRT1 inhibition reduced BCSC markers (CD44, ALDH1), stemness genes (NANOG, SOX-2), mammosphere formation, EMT, and invasion. In vivo, SIRT1 inhibition suppressed tumor growth, blocked lymphatic metastasis, and delayed cisplatin resistance. Mechanistically, these effects were mediated by downregulation of Disheveled 3 (DVL3) and attenuation of Wnt/β catenin signaling. SIRT1 is associated with the maintenance of BCSC-related properties, EMT, and activation of the Wnt/β-catenin pathway in breast cancer. Targeting SIRT1 may represent a potential therapeutic strategy to suppress tumor progression and improve treatment response.