Androgen receptor (AR) is emerging as a novel prognostic biomarker in triple-negative breast cancer (TNBC), but the underlying mechanisms remain unknown. As accumulating evidence has shown that long non-coding RNAs (lncRNAs) regulate important cancer hallmarks, we hypothesised that AR-regulated lncRNAs might play roles in TNBC progression. Here, we performed experiments with or without DHT treatment in three TNBC cell lines, and we identified an AR negatively induced lncRNA (ARNILA), which correlated with poor progression-free survival (PFS) in TNBC patients and promoted epithelial-mesenchymal transition (EMT), invasion and metastasis in vitro and in vivo. Subsequently, we demonstrated that ARNILA functioned as a competing endogenous RNA (ceRNA) for miR-204 to facilitate expression of its target gene Sox4, which is known to induce EMT and contribute to breast cancer progression, thereby promoting EMT, invasion and metastasis of TNBC. Our findings not only provide new insights into the mechanisms of lncRNA in regulating AR but also suggest ARNILA as an alternative therapeutic target to suppress metastasis of TNBC patients.

Triple negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer that poses a clinical challenge. Thus, new therapy strategies are urgently needed. The selective WEE1 inhibitor, AZD1775, has shown strong anti-proliferative effects on a variety of tumors. Here, we first demonstrate that inhibition of ATR by selective inhibitor AZD6738 can enhance AZD1775-caused growth inhibition in TNBC. Our results show that the enhanced cell death is attributed to repressed DNA damage repair and excessive replication stress, thereby causing increased DNA damage reflected by accumulation of the DNA double-strand-break marker γH2AX. On the other hand, combined treatment with AZD6738 and AZD1775 forces mitotic entry of cells with DNA damages by activating CDK1 activity, inducing severely aberrant mitosis and mitotic catastrophe, ultimately resulting in cell death. Dual inhibition of WEE1 and ATR also inactivated RAD51-mediated homologous recombination, which sensitized TNBC cells to cisplatin and PARP inhibitor. Here, based on the preclinical results that ATR inhibition synergizes with WEE1 inhibition in TNBC, we propose that this combination therapy alone, or in parallel with chemotherapy, represents an innovative and potent targeted therapy in TNBC.