Long noncoding RNA ARHGAP5-AS1 inhibits migration of breast cancer cell via stabilizes SMAD7 protein 

Abstract Background: Tumor metastasis is the main cause of death from breast cancer patients and cell migration plays a critical role in metastasis. Recent studies have shown long non-coding RNAs (lncRNAs) play an essential role in the initiation and progression of cancer. In the present study, the role of a LncRNA, ARHGAP5-AS1 in breast cancer was investigated. Methods: Bioinformation was analyzed for the expression of ARHGAP5-AS1. qRT-PCR was conducted to verify the expression of ARHGAP5-AS1 in breast cancer specimens. Transwell migration assays and F-actin staining were utilized to estimate cell migration ability. RNA pulldown assays and RNA immunoprecipitation were used to prove the interaction between ARHGAP5-AS1 and SMAD7. Western blot and immunofluorescence imaging were used to examine the protein levels. Dual luciferase reporter assays were performed to evaluate the activation of TGF-β signaling.Results: Compared to MDA-MB-231 cells, the expression of LncRNA ARHGAP5-AS1(NR_027263) was significantly suppressed in its highly metastatic subtype MDA-MB-231-LM2 cells. Functional study showed ARHGAP5-AS1 could inhibit cell migration via suppression of stress fibers in breast cancer cell lines. Afterwards, SMAD7 was further identified to interact with ARHGAP5-AS1 by its PY motif and thus its ubiquitination and degradation was blocked due to reduced interaction with E3 ligase SMURF1 and SMURF2. Moreover, ARHGAP5-AS1 could inhibit TGF-β signaling pathway due to its inhibitory role on SMAD7. Conclusions: Overall, these findings demonstrate that ARHGAP5-AS1 inhibits breast cancer cell migration and could server as a novel biomarker for breast cancer metastasis and a potent target for the treatment in the future.