Long noncoding RNA MEG3 inhibits breast cancer growth via upregulating endoplasmic reticulum stress and activating NF-κB and p53.
Zhang Yan,Wu Jiang,Jing Hong,Huang Gui,Sun Zhulei,Xu Shouming
Journal of cellular biochemistry
Long noncoding RNA (lncRNA) maternally expressed 3 (MEG3) has been implicated as a tumor suppressor gene in several human cancer types. However, little is known regarding its involvement and potential mechanism in human breast cancer. In this study, we explored the effect of MEG3 on the growth of human breast cancer cell line MDA-MB-231 in vitro and in vivo, and sought to elucidate the potential signaling mechanisms. Ectopic overexpression of MEG3 using a lentiviral vector Lv-MEG3 significantly inhibited breast cancer cell growth in vitro and a cancer xenograft growth in vivo. MEG3 overexpression led to marked increase of apoptosis in breast cancer cells as determined using flow cytometry and fragmented DNA labeling. Moreover, ectopic expression of MEG3 increased the expression of endoplasmic reticulum (ER) stress-related proteins required for unfolded protein response, including glucose-regulated protein 78 (GRP78), inositol-requiring enzyme 1 (IRE1), protein kinase RNA (PKR)-like ER kinase (PERK), and activated transcription factor 6 (ATF6), as well as proapoptotic proteins CCAAT/enhancer binding protein homologous protein (CHOP) and caspase-3. Finally, MEG3 overexpression markedly increased nuclear factor κB (NF-κB) expression, NF-κB translocation to the nucleus, and p53 expression, whereas pharmacological inhibition of NF-κB completely abolished MEG3-induced activation of p53. Together, these results suggest that MEG3 inhibits breast cancer growth and induces breast cancer apoptosis, partially via the activation of the ER stress, NF-κB and p53 pathways, and that NF-κB signaling is required for MEG3-induced p53 activation in breast cancer cells. Our results indicate targeting lncRNA MEG3 may represent a novel strategy for breast cancer therapy.
Oleandrin induces apoptosis via activating endoplasmic reticulum stress in breast cancer cells.
Li Xiao-Xi,Wang Da-Qing,Sui Cheng-Guang,Meng Fan-Dong,Sun Shu-Lan,Zheng Jian,Jiang You-Hong
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie
BACKGROUND:Breast cancer is the most common malignant tumor in women. Due to limited treatment outcome and high rate of metastasis, the prognosis is especially poor for triple-negative breast cancer. It is urgent to discover and develop novel agents for treatment of breast cancer. Herein, we investigated the potential mechanisms of Oleandrin's (a cardiac glycoside) cytotoxic activity against breast cancer cells. METHODS:Cell proliferation was assessed by xCELLigence Real-Time Cell Analyzer (RTCA)-MP system. Apoptotic cells were detected by using Annexin V/PI staining and nuclear fragments observation. The effect of oleandrin on ATP1B3 expression and markers of ER stress were determined by western blot. A primary cell sensitivity assay was performed via a collagen gel droplet-embedded culture drug sensitivity method (CD-DST). RESULTS:Oleandrin suppressed cell proliferation and colony formation in the three breast cancer cell lines but did not affect normal mammary epithelial cells. Additionally, the expression of ATP1B3 was higher in the three breast cancer cell lines compared to MCF10A cells. Treatment with oleandrin increased the number of apoptotic cells and led to nuclear pyknosis, fragmentation, and apoptotic body formation in breast cancer cells. Furthermore, oleandrin treatment increased expression of Bax and Bim but decreased that of Bcl-2. Treatment with oleandrin also upregulated the expression of endoplasmic reticulum stress associated proteins, including eIF2α, ATF4, and CHOP, but not PERK. oleandrin treatment also induced the phosphorylation of PERK and eIF2α. Of note, oleandrin exhibited antitumor effects on patient-derived breast cancer cells under three-dimensional culture conditions. CONCLUSIONS:Taken together, our results suggest that oleandrin induces mitochondrial-mediated apoptosis by activating endoplasmic reticulum stress in breast cancer. Moreover, oleandrin may be an effective strategy for the treatment of breast cancer.