lncRNA ATXN8OS promotes breast cancer by sequestering miR‑204

Multifaceted roles of long non-coding RNAs in triple-negative breast cancer: biology and clinical applications

Triple-negative breast cancer (TNBC) is a heterogeneous breast cancer subtype that lacks targeted therapy due to the absence of estrogen, progesterone, and HER2 receptors. Moreover, TNBC was shown to have a poor prognosis, since it involves aggressive phenotypes that confer significant hindrance to therapeutic treatments. Recent state-of-the-art sequencing technologies have shed light on several long non-coding RNAs (lncRNAs), previously thought to have no biological function and were considered as genomic junk. LncRNAs are involved in various physiological as well as pathological conditions, and play a key role in drug resistance, gene expression, and epigenetic regulation. This review mainly focuses on exploring the multifunctional roles of candidate lncRNAs, and their strong association with TNBC development. We also summarise various emerging research findings that establish novel paradigms of lncRNAs function as oncogenes and/or tumor suppressors in TNBC development, suggesting their role as prospective therapeutic targets.

lncRNA FGD5‑AS1 promotes breast cancer progression by regulating the hsa‑miR‑195‑5p/NUAK2 axis

Breast cancer is the second most prevalent cancer in women worldwide. Long non-coding RNAs (lncRNAs) have been identified as important regulators of tumorigenesis and tumor metastasis. lncRNA FGD5-AS1 has been previously reported as a carcinogenic gene, however its role in breast cancer has yet to be investigated. The present study aimed to understand the function of lncRNA FGD5-AS1 in breast cancer and examine the underlying molecular mechanisms. Sample tissues for downstream gene expression profiling were collected from patients with breast cancer (n=23). The effect of FGD5-AS1 overexpression on cell viability, invasion and migration has been studied in breast cancer cells (MDA-MB-231). Changes in glycolysis were monitored by comparing glucose consumption, lactate production and ATP levels. Using StarBase and TargetScan databases a putative interaction between FGD5-AS1, miR-195-5p and SNF1-like kinase 2 (NUAK2) was predicted in silico. Expression levels of FGD5-AS1, has-miR-195-5p and NUAK2 were validated by reverse transcription-quantitative PCR and interactions were validated using dual-luciferase reporter assays and RNA pull-down. High expression of lncRNA FGD5-AS1 was detected in breast cancer tissue samples and disease model cell lines. Silencing of FGD5-AS1 led to decreased cell proliferation, migration and invasion. It was identified that at a molecular level FGD5-AS1 serves as a sponge of miR-195-5p and alters the expression of its downstream target gene NUAK2. In breast cancer lncRNA FGD5-AS1 serve a key role in glycolysis and tumor progression via the miR-195-5p/NUAK2 axis. The findings of the present study indicated FGD5-AS1 as a candidate target for intervention in patients with breast cancer.

Ginsenoside Rg3 Prevents Oncogenic Long Noncoding RNA ATXN8OS from Inhibiting Tumor-Suppressive microRNA-424-5p in Breast Cancer Cells

Ginsenoside Rg3 exerts antiproliferation activity on cancer cells by regulating diverse noncoding RNAs. However, little is known about the role of long noncoding RNAs (lncRNAs) or their relationship with competitive endogenous RNA (ceRNA) in Rg3-treated cancer cells. Here, a lncRNA (ATXN8OS) was found to be downregulated via Rg3-mediated promoter hypermethylation in MCF-7 breast cancer cells. SiRNA-induced downregulation of ATXN8OS decreased cell proliferation but increased apoptosis, suggesting that the noncoding RNA possessed proproliferation activity. An in silico search for potential ATXN8OS-targeting microRNAs (miRs) identified a promising candidate (miR-424-5p) based on its high binding score. As expected, miR-424-5p suppressed proliferation and stimulated apoptosis of the MCF-7 cells. The in silico miR-target-gene prediction identified 200 potential target genes of miR-424-5p, which were subsequently narrowed down to seven that underwent hypermethylation at their promoter by Rg3. Among them, three genes (EYA1, DACH1, and CHRM3) were previously known oncogenes and were proven to be oppositely regulated by ATXN8OS and miR-424-5p. When taken together, Rg3 downregulated ATXN8OS that inhibited the tumor-suppressive miR-424-5p, leading to the downregulation of the oncogenic target genes.

LncRNA ATXN8OS enhances tamoxifen resistance in breast cancer

Background

Tamoxifen (TAMR) resistance remains a massive obstacle for breast cancer (BC) management. The precise parts of long non-coding RNA ataxin 8 opposite strand (ATXN8OS) in BC TAMR resistance have not been defined.

Methods

The levels of ATXN8OS, vasodilator-stimulated phosphoprotein (VASP), and miR-16-5p were assessed by quantitative real-time polymerase chain reaction or western blot. Colony formation and cell viability were analyzed by MTT and colony formation assays, respectively. Targeted interactions among miR-16-5p, ATXN8OS, and VASP were confirmed by dual-luciferase reporter assay. Animal studies were performed to observe the role of ATXN8OS in TAMR sensitivity in vivo.

Results

ATXN8OS expression was increased in BC tissues and cells. ATXN8OS depletion promoted BC cell sensitivity to TAMR. ATXN8OS sequestered miR-16-5p by directly binding to miR-16-5p. The promotional effect of ATXN8OS knockdown on BC cell TAMR sensitivity was mediated by miR-16-5p. VASP was a direct target of miR-16-5p, and miR-16-5p overexpression enhanced TAMR sensitivity by VASP. Moreover, ATXN8OS regulated VASP expression by acting as a miR-16-5p sponge. In addition, ATXN8OS knockdown augmented BC TAMR sensitivity in vivo.

Conclusion

ATXN8OS knockdown enhanced BC TAMR sensitivity partially through the miR-16-5p/VASP axis, highlighting a potential therapeutic target for improving the clinical benefits of TAMR treatment in BC patients.