Theranostics 2018; 8(10):2846-2861. doi:10.7150/thno.23463

Research Paper

Long non-coding RNAs AC026904.1 and UCA1: a “one-two punch” for TGF-β-induced SNAI2 activation and epithelial-mesenchymal transition in breast cancer

Guo-Yin Li1*, Wei Wang2*, Jian-Yong Sun3*, Bo Xin4, Xiang Zhang1, Ting Wang1, Qian-Feng Zhang5, Li-Bo Yao1, Hua Han1, Dai-Ming Fan6, An-Gang Yang2, Lin-Tao Jia1✉, Lei Wang1✉

1. State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, China;
2. Department of Immunology, Fourth Military Medical University, Xi'an, China;
3. Department of Thoracic Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, China;
4. Department of Oncology, No. 88 Hospital of PLA, Tai'an, China;
5. Department of Obstetrics and Gynecology, Xijing Hospital, Fourth Military Medical University, Xi'an, China;
6. Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an, China
*These authors contributed equally to this work.

Abstract

Transforming growth factor-β (TGF-β) has received much attention as a major inducer of epithelial-mesenchymal transition (EMT) during cancer progression, mainly by activating a set of pleiotropic transcription factors including SNAI2/Slug. However, the involvement of long non-coding RNAs (lncRNAs) in TGF-β-induced Slug activation and EMT remains largely unknown.

Methods: In this study, we used microarray analysis to compare lncRNA expression profiles between TGF-β treated and untreated breast cancer cells. Then, the clinical significance of lncRNAs in breast cancer was investigated by qPCR and Kaplan-Meier survival analysis. The molecular mechanisms and EMT-promoting effects in vitro were analyzed by confocal laser microscopy, Western blotting, chromosome conformation capture (3C), chromatin isolation by RNA purification (ChIRP), ChIP, luciferase reporter assay and transwell migration assay. Lastly, the pro-metastatic effects in vivo were evaluated by bioluminescent imaging and hematoxylin and eosin (H&E) staining.

Results: We observed that TGF-β induced genome-wide changes in lncRNA levels in breast cancer cells, among which AC026904.1 and UCA1 were highly expressed in metastatic breast cancer and closely associated with poor prognosis. Mechanistic study revealed that AC026904.1 and UCA1 were upregulated by non-canonical and canonical TGF-β pathways, respectively. Further analysis showed that AC026904.1 functions as an enhancer RNA in the nucleus, whereas UCA1 exerts a competitive endogenous RNA (ceRNA) activity in the cytoplasm. In addition, the biological functions of these two lncRNAs converged on the activation and maintenance of Slug, constituting a one-two punch in promoting EMT and tumor metastasis.

Conclusion: These findings uncover for the first time that AC026904.1 and UCA1 could cooperatively upregulate Slug expression at both transcriptional and post-transcriptional levels, exerting critical roles in TGF-β-induced EMT. The present work provides new evidence that lncRNAs function as key regulators of EMT and hold great promise to be used as novel biomarkers and therapeutic targets for metastatic breast cancer.

Keywords: EMT, lncRNA, enhancer RNA, ceRNA, breast cancer.

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How to cite this article:
Li GY, Wang W, Sun JY, Xin B, Zhang X, Wang T, Zhang QF, Yao LB, Han H, Fan DM, Yang AG, Jia LT, Wang L. Long non-coding RNAs AC026904.1 and UCA1: a “one-two punch” for TGF-β-induced SNAI2 activation and epithelial-mesenchymal transition in breast cancer. Theranostics 2018; 8(10):2846-2861. doi:10.7150/thno.23463. Available from http://www.thno.org/v08p2846.htm