The lncRNA DANCR promotes breast cancer brain metastasis by acting as a ceRNA for miR-758-3p to regulate PTGS2 expression

Abstract

Brain metastases in breast cancer patients are correlated with markedly lower survival rates than extracranial metastases, highlighting the critical necessity for identifying novel therapeutic targets. The functional involvement of differentiation antagonizing nonprotein coding RNA (DANCR) in the pathogenesis of breast cancer brain metastases (BCBMs) has yet to be fully elucidated. Bioinformatics analyses identify DANCR as a potential specific prognostic biomarker of BCBM. CCK-8, transwell, and wound healing assays are performed to examine the effects of DANCR on the proliferation, migration, and invasion of tumors, along with in vivo assays. Mechanistic insights are obtained through quantitative real-time polymerase chain reaction (qRT-PCR), western blot analysis, and dual-luciferase reporter assays. DANCR is markedly upregulated in BCBM and specifically correlates with the prognostic risk of BCBM. DANCR overexpression significantly enhances breast cancer cell proliferation, migration, and invasion. According to low-throughput screening, only the expression of prostaglandin-endoperoxide synthase 2 (PTGS2) consistently varies in parallel with that of DANCR, and PTGS2 silencing reverses DANCR-induced protumor effects in vitro. Additionally, in brain metastatic lesions, PTGS2 expression is also elevated in patients with increased DANCR expression. Mechanistically, DANCR and PTGS2 possess a conserved miR-758-3p response element. DANCR directly binds to and sequesters miR-758-3p, thereby alleviating the suppressive effects of miR-758-3p on both DANCR and PTGS2. When the miR-758-3p binding site on DANCR is mutated, this interaction is completely abolished. DANCR drives BCBM by functioning as a miR-758-3p sponge to upregulate PTGS2. Targeting the DANCR/miR-758-3p/PTGS2 axis represents a promising therapeutic approach.

1. Introduction

Breast cancer is the most common malignancy among women worldwide. Compared with other types of extracranial metastases, brain metastasis, one of the most severe complications of breast cancer, is associated with a significantly poorer prognosis [1]. With advances in systemic therapies and prolonged survival of breast cancer patients, the incidence of brain metastases has also increased [2,3]. Current estimates indicate that approximately 15% to 30% of breast cancer patients will develop brain metastases [4]. The introduction of anti-erb-b2 receptor tyrosine kinase 2 (HER2) therapies has significantly improved outcomes for patients with HER2-positive breast cancer and brain metastases, extending the median overall survival to 34.4 months [5–7]. However, treatment options for triple-negative BCBM remain limited, with ongoing research focusing on combinations of chemotherapy, immune checkpoint inhibitors, and novel targeted therapies [8–12].

Through analyses of brain metastasis samples and preclinical models, researchers have identified a number of potential therapeutic targets implicated in BCBM. Elevated expression of vascular endothelial growth factor A (VEGFA), epidermal growth factor receptor (EGFR), and Rous sarcoma oncogene (SRC) enhances the metastatic potential of breast cancer cells to the brain [13–19]. In addition, multiple proteins, including ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 5 (ST6GALNAC5), PTGS2, heparin-binding EGF-like growth factor (HBEGF), cathepsin S (CTSS), angiopoietin-2 (ANGPT2), cell migration-inducing hyaluronidase 1 (CEMIP), matrix metallopeptidase 1 (MMP1), cell migration-inducing hyaluronidase 2 (MMP2), sphingosine-1-phosphate receptor 3 (S1P3), and syndecan 1 (SDC1), have been shown to facilitate the transmigration of breast cancer cells across the blood-brain barrier (BBB) [19–27]. Furthermore, protocadherin 7 (PCDH7) and YTH N6-methyladenosine RNA binding protein F3 (YTHDF3) play crucial roles in mediating interactions between metastatic breast cancer cells and astrocytes within the brain microenvironment [18,28]. Despite these advances, effective treatment of BCBM remains a major clinical challenge, and the identification of additional therapeutic targets is urgently needed.

Recent studies have highlighted the significant regulatory roles of long non-coding RNAs (lncRNAs) in tumor progression and metastasis through diverse mechanisms. For example, lncRNA associated with BCBM (Lnc-BM) promotes BCBM by enhancing communication between breast cancer cells and the brain microenvironment [29]. Our previous work demonstrated that lncRNA-cardiac conduction regulatory RNA (CCRR) promotes the formation of gap junctions between metastatic breast cancer cells and astrocytes by upregulating gap junction protein alpha 1 (CX43) expression [30]. Moreover, the exosome-derived lncRNA GS1-600G8.5 has been shown to facilitate BCBM by compromising the integrity of the BBB [31]. In this study, through bioinformatics analyses and experimental validation, we identify DANCR as a novel lncRNA involved in BCBM and elucidate its molecular mechanism, providing a potential therapeutic target for this devastating disease.